Human Papillomaviruses-Related Cancers: An Update on the Presence and Prevention Strategies in the Middle East and North African Regions

The human papillomavirus (HPV) is a non-enveloped double-stranded DNA virus capable of infecting skin and mucosa epithelial cells. Commonly, HPV infection is associated with sexually transmitted diseases and is considered the leading cause of cervical cancer and other carcinomas of the anogenital tract. However, several studies reported their involvement in cancers of non-sexual regions, including colorectal, head and neck, and breast cancers. There are several studies from the Middle East and North Africa (MENA) regions on the potential association between high-risk HPVs and cancer; nevertheless, there are limited studies that address the significance of HPV vaccination as a potential guard against these cancers. In the current review, we present a comprehensive description of the current HPV-associated cancers prevalence rates in the MENA region, demonstrating their steady increase with time, especially in African regions. Moreover, we discuss the potential impact of vaccination against HPV infections and its outcome on human health in this region.


Introduction
Cancer is one of the leading causes of mortality, with approximately 20 million new cancer cases worldwide and 10 million cancer deaths [1]. Along with environmental and genetic factors, recent studies attribute 20% of human cancers to viralor bacterial infections [2]; with several reports revealing the presence of viruses in both solid and non-solid tumors [3]. Some of the most commonly identified viruses include Epstein-Barr virus (EBV), human papillomaviruses (HPVs), human herpes virus 8 (HHV8 or Kaposi's sarcoma-associated herpesvirus), as well as hepatitis viruses B and C (HBV and HCV) [3]. Advancement in molecular biology showed viral oncogenes to alter cell signaling and growth control pathways, thus triggering the onset and development of human diseases, including cancer [4].
Human papillomaviruses (HPVs) are small, double-stranded DNA viruses with an icosahedral capsid belonging to the Papillomaviridae family and are the etiological agent of dermatological and sexually transmitted diseases [5]. Commonly, HPV is the most common cause of sexually transmitted infections worldwide, with once in a lifetime infection risk amongst both men and women of about 50% [6]. HPVs have the ability to infect the cutaneous and mucosal epithelial tissues of the skin, upper respiratory, and anogenital tracts [5]. Although HPVs are well-known inducers of common and anogenital warts [7], transition (EMT) [57]. The HPV cycle is completely intraepithelial, non-lytic, and blocks pro-inflammatory signal activation, thus recruiting antigen-presenting cells and releasing cytokines; these events promote cell growth and proliferation [5]. Nevertheless, most highrisk HPV types evade host immune recognition and induce persistent infection, promoting neoplastic transformation and cancer progression [5].
Numerous investigations worldwide reported a varying prevalence of HPV infection subtypes in human cancers, indicating an association between geographical location and HPV prevalence [15,18,[58][59][60]. The Middle East and North Africa (MENA) region consists of 19 countries, including Algeria, Bahrain, Egypt, Iran, Iraq, Israel, Jordan, Kuwait, Lebanon, Libya, Morocco, Oman, Qatar, Saudi Arabia, Syria, Tunisia, United Arab Emirates (UAE), and Yemen. Though the MENA region is highly diverse politically, culturally, and economically, most of the population in the MENA region shares conservative cultural values [61]. As compared to the West, the MENA region has a lower HPV prevalence rate [62]. However, most MENA countries do not screen for HPV infections due to stigmatization based on religious and traditional values, plausibly leading to small sample sizes and low incidence rates of HPV infection, thus miscalculating the actual number of cases [62].
Moreover, since HPV infection is majorly sexually transmitted, the introduction of vaccination programs within countries of the MENA region is nascent [61,63]. Today, in addition to Turkey (which includes the organized screening program) [64], Libya and UAE are the only two countries with HPV vaccine included in their health programs [62]. On the other hand, countries such as Qatar, Algeria, and Morocco included HPV vaccination programs in their health settings, but they are not readily available to the population [62].
As compared to developed countries, reports on HPV infection and human cancers are limited in developing countries, including the Middle East and North Africa (MENA) region. Herein, we will review the updated literature on the presence and distribution of HPVs in human cancers with a special focus on cervical, head and neck, colorectal, and breast cancers in the MENA region. The countries of the MENA region will be classified into the GCC (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and UAE) and Yemen region, Levant countries (Iraq, Jordan, Lebanon, Palestine, and Syria), Maghreb countries (Algeria, Libya, Morocco and Tunisia) and Other countries of the MENA region (Egypt, Iran and Israel). Turkey, a country of unique Ottoman descent, is often listed among Middle-Eastern countries since it occupies regional territories in both Asian and European continents, sharing boundaries with other Middle-Eastern-Mediterranean countries, such as Syria and Iran; thus it will also be included in the list of the countries discussed.

High-Risk HPVs in Cervical Cancer
Cervical cancer is the fourth most commonly diagnosed cancer, as well as the fourth leading cause of cancer death in women [1]. Infection with high-risk HPV is the most common cause of the onset and development of cervical cancer and accounts for more than 99% of all cervical cancer cases [65]. Although a non-sexual mode is reported, sexual transmission remains the most common mode of infection [66]. Following high-risk HPV infection, the virus is deposited on the basal layer of the cervical epithelium infecting its mucosa [66]. Viral replication occurs, and the HPV DNA is integrated into the cellular genome, leading to the onset of cervical cancer [66]. On average, persistent HPV infection progresses into high-grade cervical intraepithelial neoplasia and invasive cancer within 15-30 years [67].
In approximately 50% of the cases, high-risk HPV-infected women do not develop clinically detectable serum antibody levels and thus pose a risk of re-infection with the same HPV subtype [68]. Today, widespread HPV infection and its association with cervical cancer made HPV vaccination an essential part of cervical cancer prevention strategies. HPV vaccines produce continuous levels of serum-neutralizing antibodies, which are efficient in alleviating the disease [68]. Formal screening and vaccination programs in high-income countries helped reduce cervical cancer incidence and mortality by 50% [67]. However, in the middle-and low-income countries, the prevalence of cervical cancer is still high (~90%) due to the lack of HPV screening and vaccination programs [67]. To date, three HPV vaccines (Cervarix, Gardasil, and Gardasil-9) protecting against either two, four, or nine types of HPV, respectively, protect against HPVs -16 and -18, which are the most frequent high-risk HPV subtypes, in addition to other HPV types [69,70], and are effective in preventing cervical cancer development by 70% [71]. A nationwide study from Sweden by Lei et al. (2020) [23], including over 1.6 million females aged 10 to 30 years, found that HPV vaccination correlates with a reduction in the incidence of invasive cervical cancer. Despite its effectiveness, HPV vaccination coverage worldwide is still limited to 15% [72].
Nevertheless, though the association between HPV infection and progression of cervical cancer is well known, only a few studies from the MENA region reported data on HPV-associated cervical cancer (Table 1). A meta-analysis by Obeid et al., 2020 [62] reported a pooled HPV prevalence rate of 81% in cervical cancer patients, 54% in women with abnormal cervical cytology results and 16% among the general population in the MENA region. Moreover, the study reported the highest HPV positivity in cervical cancer in Maghreb countries (88%), while the lowest prevalence was found in Iran (73%) [62]. On the other hand, abnormal cervical cytology subgroup had a pooled HPV prevalence of 54%, with the highest reported prevalence in Northeast Africa (94%) and the lowest in the Levant region (31%) [62]. Furthermore, middle-and low-income countries had the highest HPV prevalence rates [62]. Similar to other regions, in the MENA region, the most commonly detected HPV subtype in cervical cancer samples is HPV16, followed by HPV18 [62]. Another study also evaluated the pool prevalence of HPV and its high-risk genotypes in Middle Eastern countries and reported a prevalence of 12.3% and 5.2%, respectively [73]. Below, we provide the prevalence and distribution of HR-HPVs and their association with cervical cancer in MENA countries (Table 1).

In GCC Countries and Yemen
In the GCC region, HPV positivity was reported in~10% of cervical cancer patients; high-risk HPVs were present in only~4% of the samples [73]. A recent study by Ali et al. (2019) [74] analyzed the presence of cervical high-risk HPV infection among women in some GCC countries, including Bahrain, Saudi Arabia, Qatar, and UAE. The study reported 21% of cervical high-risk HPVs in women, of which Arab women had a significantly lower prevalence of high-risk HPV infections compared with non-Arab women (16.4% vs. 31.6%); however, no significant difference in the distribution of high-risk HPV infection types was present between the two groups [74]. Demographically, the overall high-risk HPV prevalence was highest in women from Qatar (31%), followed by women from Bahrain (20%), Saudi Arabia (17%), and UAE (15%) [74]. Surprisingly, younger women (<50 years) were positive for high-risk HPVs, indicating that younger women are at a higher risk of HPV infection [74]. In addition, while infection with HPV16 and HPV18 was low (17% and 3%, respectively), infection with other high-risk HPVs was highly predominant, accounting for 64% of the cases [74]. Based on the cytological diagnosis, the overall high-risk HPV positivity rate among women with normal and abnormal cytology was 15% and 51%, respectively, indicating that the presence of high-risk HPVs is associated with abnormal cytology [74]. The study also evaluated the presence of high-risk HPV positivity in women with atypical glandular cells not otherwise specified (AGC-NOS), atypical squamous cells that cannot exclude high-grade squamous intraepithelial lesion (ASC-H), atypical squamous cells of undetermined significance (ASCUS), high-grade squamous intraepithelial lesion (HGSIL), low-grade squamous intraepithelial lesion (LGSIL), and negatively for intraepithelial lesion or malignancy (NILM) [74]. The results indicate an increase in high-risk HPV positivity rates with the severity of cytological lesions, from 41% in women with ASCUS to 60% in those with HSIL as compared to (15%) in NILM [74].
Notably, to date, only one study was performed in Oman regarding the presence of HPV in women with normal and abnormal cytology; the study reported a prevalence of 17% and 37.5% of HPV, respectively [80]. The study further reported the presence of 22 different HPV genotypes (15 high-risk and seven low-risk), with HPV82 (high-risk,~11%) and HPV54 (low-risk, 12%) being the most prevalent among women [80].
On the contrary, UAE reported the highest prevalence of high-risk HPVs (88%) in samples from women diagnosed with cervical squamous intraepithelial neoplasia and cervical carcinomas, with HPV16 as the most commonly detected HPV subtype [92]. Similarly, another study involving women diagnosed with ASCUS reported the presence of high-risk HPVs in 18% of the cases, especially in pre-menopausal women with HPV16 as the predominant subtype [93]. HPV18 was reported as a less frequent high-risk HPV subtype [93,94].

In Levant Countries
Similar to studies in GCC, studies in the Levant countries are also limited. In Iraq, Goral et al., 2019 [98] and AlMufty et al., 2016 [99] explored cervical HPV genotype distribution among different Pap readings. Intriguingly, Goral et al. reported 40.6% HPV-positive cases, out of which 46.2% were normal, and 53.8% had abnormal Pap smears. Additionally, both high-risk (HR-HPV) and low-risk (LR-HPV) genotypes were identified in the sample with a higher frequency for HR-HPV [98]. Concurrently, AlMufty et al. tested 104 samples obtained from women with vaginal discharges and lower abdominal pain, 12.5% were positive for high-risk HPV genotypes, out of which 30.7% were HPV16, and 53.8% showed mixed genotyping [99]. Jubrael et al., 2012, studied the levels of IL-10 and TNFα cytokines in women with HPV DNA + and DNA − cervical lesions [100]. The authors reported a significantly higher level of IL-10 in cervical secretions of HPV DNA + compared to DNA − patients (88.73 vs. 24.00 pg/mL) and in samples obtained from healthy individuals (control) (88.73 vs. 8.27 pg/mL). On the other hand, no difference was noted in the levels of TNFα in cervical secretions of HPV DNA + vs. DNA − cases and controls (12.18 vs. 9.90 vs. 7.90 pg/mL, respectively) [100]. The study suggests that the notable increase in IL-10 compared to TNFα could be due to a down-modulation of tumor-specific immune responses to HPV-infected lesions [100].
Two Jordanian studies reported the presence of HPV infection in cervical cancer; they show an increase in the prevalence of HPV infection in Jordanian women with cervical cancer [101,102]. The first study reported an overall high-risk HPV prevalence in cervical cancer (87%), low-grade squamous intraepithelial lesions (72%), and high-grade squamous intraepithelial lesions (79%); genotyping identified HPV16 as the most predominant subtype (54%) in all cervical lesions [101]. A recent analysis by Abu-Lubad et al. (2020) [102], reported an increase in HPV infection in cervical cancer patients against controls (92% v/s 61%); this study also reported significant dominance of the HPV16 subtype. Contrary to findings from GCC countries, in Jordan, women older than 50 years of age displayed the highest HPV infection rate [102]. Compared to Jordan, in the Lebanese population, only one study was carried out to determine the presence of HPV in Lebanese women with cytological abnormalities; the study reported the presence of HPV in 5% of the women with HPV16 as the dominant subtype [103].

In Maghreb Countries
In Algeria, Mougin et al., 2016 reported a 100% prevalence of HPV in cervical cancer samples [105]. On the other hand, Mouhammedi et al., in 2017, examined cervical samples from 96 women that were either HIV-1-infected or presenting with a gynecological disease [106]. The authors found that 60% of tested samples were HPV+, out of which, HR-HPV infection accounted for more than 80%. Remarkably, the study also noted a significantly higher frequency of HPV infection among the HIV-1-infected group [106].
In Libya, only one study was published in 2014 exploring the prevalence of HPV in North-Eastern Libyan patients with cervical cancer [107]. The study reports a strong connection between HPV and cervical cancer, with the majority (82.5%) of tested samples positive for HPV-16 and 12.7% positive for HPV-18 genotype [107].
In Morocco, various studies were published between 2010 and 2017, investigating the prevalence and genotype distribution of HPV in cervical cancer [108][109][110][111]. HPV infection in patients with cervical cancer was reported to be 92.5% versus only 13.9% in healthy cases, with HPV16 as the most common genotype, followed by HPV18 [111]. Concurrently, Elgnaoui et al., 2016, [110] reported that 74% of tested biopsies were positive for HPV, of which 67.7% were high-risk HPVs, and 24% were low-risk HPVs. In Fez and neighboring areas, the reported prevalence of HPV was only 43.1%, with the most prevalent genotype being HPV 53 [110].
In Tunisia, a recent study investigated the distribution of HPV in precancerous and cancerous cervical neoplasia and reported an HPV prevalence of 83% in cervical lesions [112]. More specifically, HPV was detected in 65% of CIN I, 82% of CIN II/CIN III, and 85% of cervical cancer cases [112]. Genotyping revealed the presence of HPVs -16 and -18 in all tested lesions, and a significant association between HR-HPV and cervical intraepithelial neoplasia was determined [112].

In Other Countries of the MENA Region and Turkey
In Egypt, Yousef et al., 2016 [113], detected 26 HPV types with a prevalence of 40.8% in the 152 women tested. In cytologically normal females, HPV prevalence was 17.7%, 56.5% in patients with a low-grade squamous intraepithelial lesion (LSIL), 3.2% in the high-grade squamous intraepithelial lesion (HSIL), and 22.6% in invasive squamous cell carcinoma (SCC) groups [113]. Similarly, HPV positivity of 22% was reported in cervical cancer patients with a prevalence of 6.5% of high-risk HPV subtypes [73]. Recently, Elazab, M et al., 2021, reported that out of 1000 women included in the study, only 14.3% were tested for HPV and were found positive, while 85.7% of women were not tested. In addition, 67.8% of HPV-positive women were found to have different degrees of CIN [114].
In Iran, Khodakarami and colleagues [115] were the first to report HPV positivity in 8% of the general female population with a 5% prevalence of high-risk HPVs. In their investigation, they identified cervical cytological abnormalities in 34 women, of whom 35.3% were HPV-positive [115]. The most prevalent subtype identified in the Irani population was HPV16, followed by HPV18. Moreover, while HPV16 was predominant in 60% of invasive cervical cancer, it was present in 9% and 2% of women with abnormal and normal cytology, respectively [115]. Moreover, a pooled prevalence of HPV positivity was reported in~14% of cervical cancer samples, with a prevalence of 6.5% of high-risk HPV subtypes [73].
As for Israel, studies published from 2017 to 2021 [116][117][118] reported similar results. For instance, Schejter et al., 2021 screened 115,807 cervical samples from the general population and found only 9% positivity for HR-HPV, out of which 37% had abnormal PAP LBC results [118]. Similarly, in patients positive for HIV, HR-HPV was detected in 29% of the screened samples, out of which 35% had CIN 2 or higher on histopathology [117]. In patients with CIN 2-3, HPV was detected in 92.9%, and HR-HPV was detected in 85.8% [116].
Moreover, in Turkey, a pooled HPV prevalence of 8% was reported in cervical cancer samples [73]. The prevalence of high-risk HPV subtypes was 6% [73]. Additionally, Oruc et al. (2022) reported national cervical cancer screening results from 89,302 women between 2015 and 2019. The study found that 94.1% of the samples were HPV-negative, while only 4.9% were HPV-positive. The most common HPV genotypes were 16, 51, 31, and 52 [119].
Overall, studies investigating the prevalence of high-risk HPV-induced cervical cancer in the Middle East and North Africa are still scarce. We believe it is still crucial to conduct larger studies with bigger sample sizes to confirm the incidence of high-risk HPVs in the stated population. Notably, the methodology used for HPV DNA detection varied significantly amongst reviewed papers. Although the majority of studies used RT-PCR [74,[79][80][81][82][83][84]92,95,96,[99][100][101][102][103], others also used Hybird Capture 2 (HC2) [85], HPV linear array assay and direct sequencing [90], and hybridization reverse blot technique [98,105,106]. The highlighted differences in HPV detection technique used potentially affected the reported prevalence of HPV.

High-Risk HPVs in Head and Neck Cancer
Head and neck cancers (HNCs) include cancers affecting the oral cavity, pharynx (naso-, oro-, and hypopharynx), larynx, nasal cavity and paranasal sinuses, as well as tumors of salivary glands [120]. HNCs account for 5-50% of all cancers and are the tenth most commonly occurring cancers worldwide [1]. Tobacco consumption is the major risk factor for HNCs, including oral [121]. Viral infections by HPVs are a well-known etiological factor for HNCs, as HPV accounts for approximately 25% of all HNCs [122]. Similar to cervical cancers, HPV16 is the dominant genotype in HNCs; however, genotyping varies based on sex and geographical regions worldwide and ranges from 0 to 60% in prevalence [123]. Jalouli and colleagues [124] analyzed the presence of HPV in oral cavity squamous cell carcinomas (OCSCC) from eight countries in Asia, Africa, Europe, and North America. The study reported that 35% of the samples were positive for HPV; the highest prevalence of HPV was observed in Sudan (65%) [124]. However, due to the limited number of cancer cases from each country (~20 samples), no definite conclusion could be drawn from the study [124]. A recent report examined the prevalence of HPV positivity in oropharyngeal squamous cell carcinoma (OPSCC) in 34 Middle Eastern patients, the majority of them from Lebanon (27), in addition to patients from Syria (3), Iraq (2), Jordan (1), and Palestinian territories (1) [125]. The study reported a comparatively higher HPV prevalence of about 85% in these patients; while the Lebanese patients had HPV positivity of 76%, Syria and Iraq reported HPV positivity of 10% and 7%, respectively [125]. Both Jordan and Palestinian territories reported 3% of HPV positivity [125]. Similarly, a global meta-analysis in OPSCC reported the highest HPV occurrence in Lebanon (85%) [126]. Correspondingly, a recent meta-analysis on HPV-associated HNC prevalence rates in the MENA region reported an overall pooled incidence of 16%; HPV was predominantly present in the salivary glands (20%) and tonsils (16%) [127]. While the study further reported a higher prevalence of HPV-associated HNC in Turkey and Palestine-Israel territory (48% and 31%, respectively), while a low prevalence was reported in Saudi Arabia and Yemen (4% and 2%, respectively) [127]. Additionally, genotyping revealed the predominant presence of HPV16 followed by HPV18 in the MENA region [127]. Below we detail the prevalence and genotype distribution of HR-HPV types and their association with head and neck cancers in MENA countries (Table 2).

In GCC Countries and Yemen
Although there is insufficient literature reporting HPV-associated head and neck cancers from GCC, a few studies were carried out in Saudi Arabia, UAE, and Yemen. However, no similar studies were performed in neighboring countries, such as Bahrain, Kuwait, Oman, and Qatar.
A recent study from Saudi Arabia explored oral tongue squamous cell carcinoma patients, revealing the presence of HPV18 in 23% of the cases. HPV infection was associated with poor overall survival [138]. Another study examined the association of HPV in Saudi patients with head and neck squamous cell carcinoma (HNSCC); the study reported an overall HPV positivity of 3.5% in HNSCC patients, with a predominance in oropharyngeal carcinoma (21%) [139]. On the contrary, Jaber and colleagues [140] failed to report the presence of HPV in oral squamous cell carcinomas.
In UAE, only one study analyzed the presence of the two subtypes, HPV -16 and -18 in the onset and development of oral premalignant and squamous cell carcinoma; the study reported 73% and 71% of the cases to be positive for HPV16 and HPV18, respectively [165]. In addition, 58% of the cases were co-infected with HPV16 and HPV18 [165]. Nasher et al. (2014) [160] evaluated the expression of HPVs -16 and -18 in OSCC patients from Yemen; the study did not report the presence of HPVs in the OCSCC samples.

In Levant Countries
In Jordan, to date, only three studies were conducted to analyze the relation between HPV presence and head and neck cancer development. Recently, Khasawneh et al. (2020) [134] reported 31% HPV positivity in head and neck squamous cell carcinoma samples, of which 42%, 37%, and 18% of HPV positivity was present in samples from the oropharynx, oral cavity, and larynx, respectively. On the other hand, while a study on laryngeal squamous cell carcinoma found 15.4% of the samples positive for HPV [135], another investigation focusing on both oral and laryngeal squamous cell carcinomas demonstrated an overall pooled HPV positivity of 15%; compared with laryngeal carcinoma, oral carcinomas exhibited a higher HPV positivity (6% vs. 20%) [152]. Nevertheless, all three studies reported predominance of the HPV16 genotype in their samples (31-85%) [134,135,152].
On the other hand, although the highest HPV prevalence in the MENA region was reported in Lebanon (85%) based on a recent meta-analysis [125,126], only one study in the Lebanese population reported an HPV prevalence of 27% in oropharyngeal squamous cell carcinoma (OPSCC) samples [148].

In Maghreb Countries
Compared with GCC and Levant regions, studies within Maghreb countries are very scarce and limited to two studies from Algeria and Tunisia.
The Algerian study investigated the presence of HPV in different cancers, including HNC. However, the study did not detect the presence of HPV in head and neck cancer [105].
On the other hand, in Tunisia, only one recent study documented the presence of HPV in HNC and reported 56% HPV positivity [133].
The above studies indicate the lack of information and hence warrant the necessity for further investigation.

In Other Countries of the MENA Region and Turkey
Other countries in the MENA region also explore the genotype distribution of HPVs in human cancers, especially Iran and Turkey. There are numerous studies carried out in these countries highlighting a probable association of HPV in the pathogenesis of HNCs.
An early study in Iran reported 41% HPV prevalence in oral squamous cell carcinoma, with HPV16 as the most predominant, followed by HPV18; however, HPVs -31 and -33 were undetected [166]. Recently, the IROPICAN study, a large multicenter case-control study in Iran, screened 21 α-HPV, 46 β-HPVs, and 52 γ-HPVs using bead-based HPV genotyping assays in 498 head and neck squamous cell carcinoma samples and 242 controls [171]. The study revealed the presence of α-HPVs in only 1.2% of the patients and 2.9% of the controls, from which HPV16 was the most prevalent type among participants [171]. On the other hand, β-HPVs and γ-HPVs were detected in 43.8% and 26.1% of the patients, versus 38.6% and 24.7% of the controls, respectively [171]. Similar to this study, a previous study in 2017 also reported a low HPV prevalence (3%) in head and neck squamous cell carcinomas [149]. In contrast, other investigations revealed a higher HPV positivity (7-43%) in head and neck squamous cell carcinomas [128][129][130]162], with HPVs -18, -52, and -61 as dominant subtypes [130,162]. Additionally, a systematic review and meta-analysis revealed an overall presence of HPV in oral lesions (21%), whereas, in oral squamous cell carcinoma, HPV prevalence was 31% [172]. Moreover, in laryngeal squamous cell carcinomas, 28% of the samples were HPV-positive; HPV16 was predominant, followed by HPV18 [150]. A study by Roshan et al. did not detect the presence of high-risk HPVs in laryngeal cancer [159]. Additionally, in sinonasal inverted papilloma, while benign samples showed 19% HPV positivity with the predominance of low-risk HPVs (HPV 6/11), squamous cell carcinoma cases were all positive for HPV (100%), with high-risk HPVs (HPV16/18) being in high proportion [156].
A Turkish study on 81 patients documented an increase in the prevalence of HPVassociated oropharyngeal cancers from 38 to 70% between the periods of 1996-2003 and 2004-2011 [173], While a very recent study by Köksal et al. (2021) reported a 24.5% HPV positivity in head and neck squamous cell carcinoma cases with a high prevalence of HPV16 genotype (85%) [131]. An earlier study carried out chromogenic in situ hybridization analysis for HPV DNA on fine-needle aspiration materials from metastatic lesions of 26 patients with HNSCC and reported 15% HPV positivity; the study reported HPV-positive tumors in two laryngeal sites, one nasopharyngeal site, and one oral cavity site [169]. In addition, cytologic review of these lesions revealed the presence of both keratinized and non-keratinized metastatic tumors; all HPV DNA-positive HNSCC tumors displayed non-keratinizing characteristics [169]. In general, when it comes to laryngeal carcinomas, reports vary with regards to HPV prevalence from 2 to 41% [142,153,167,168] with HPV16 as the most common subtype [142,153]. In contrast, Celebi et al. did not detect the presence of HPV neither in normal laryngeal mucosa nor laryngeal carcinoma patients [144]. In esophageal carcinoma, HPV DNA positivity was reported in~10% of the samples, with HPVs -16 and -39 being common [157].
It is clear from the above information that more investigations are necessary to confirm the presence and genotype distribution of HPVs in HN cancer cases in the MENA region.

High-Risk HPVs in Colorectal Cancer
The incidence of colorectal cancer (CRC) increased exponentially in the past years; CRC is the third most common type of cancer and the second leading cause of cancerrelated deaths worldwide [1]. Notably, CRC is linked to both hereditary and environmental risk factors, including viral infection by high-risk HPV, EBV, HCV, HBV, HHV8, and HIV [18,174]. According to a report by Donà and colleagues [175], HPV associated CRC is the most common in homosexual men involved in anal sex (MSM), especially amongst HIVinfected individuals receiving treatment. In addition, a number of studies highlighted that HPV infection is the major cause of development of anal/rectal lesions that subsequently develop into CRC [176,177]. Despite the global rise in the number of studies linking HPV to the development and progression of CRC, only a few studies from the MENA region reported data on HPV-associated CRC. These include countries such as Egypt, Iran, Israel, Lebanon, Saudi Arabia, Syria, and Turkey (Table 3). Below we detail the prevalence and genotype distribution of HR-HPV types and their association with CRC in MENA countries.

In GCC Countries and Yemen
Studies demonstrating the association between HPV presence and the onset of CRC in GCC countries are very rare. Only a few studies in Saudi Arabia reported the presence of HPV in CRC. An investigation involving 132 CRC patients in Saudi Arabia reported only two HPV-positive cases (1.5%) [195]. However, another study reported no presence of HPV-16 nor HPV-18 in CRC samples [196]. Data from these studies indicate that HPV prevalence in CRC may be reasonably low within the GCC countries as compared to the rest of the MENA region.

In Levant Countries
There are comparatively more reports about the presence of HPV in CRC cases in the Levant region.
One very recent study in Iraq identified HPV16/18 positivity in 44.4% of CRC cases using chromogenic in situ hybridization [193].
In Lebanon, our group reported HPV prevalence in 60 cases out of the 94 CRC samples (64%), with HPV-16 and HPV-18 as the most frequent HR-HPV subtypes [17].
We also demonstrated HPV association with CRC development in Syrian cases in two different investigations, with an HPV prevalence of 54% and 37% in each one [53] [192]. Both studies revealed HPVs -16 and -18 as the most frequent HR-HPV types [53].

In Maghreb Countries
Interestingly, to date, there are no studies about the prevalence of HPVs in CRC in Maghreb countries within the MENA region.

In Other Countries of the MENA Region and Turkey
Compared to studies in the GCC, Levant, and Maghreb countries, there are several reports from Egypt, Iran, Israel, and Turkey analyzing the prevalence of HPV in CRC.
There is only one study from Egypt regarding HPV's association with CRC [197]. The study analyzed the presence of HPV-16/18 in 40 CRC samples, demonstrating the presence of HPV in six cases (15%). The most common HPV subtypes were HPV18 (12.5%) and HPV16 (2.5%); however, none of the 40 CRC cases were co-infected by HPV16/18 [197].
The bulk of the reports on HPV association with the pathogenesis of colorectal cancer in the MENA region come from Iran. Only a few of these studies report a high prevalence of HR-HPVs in colorectal cancer. In this context, a recent study by Tavakolian et al. (2020) reported that 12% of CRC samples were positive for HPV DNA [179]. Another study reported the presence of HPV-16 (10.5%) and HPV-18 (23.65%) in CRC cases [178]. A significantly high prevalence of HPV DNA (83%) was reported in CRC cases with a high frequency of the HPV subtype 16 (68%) [180]. However, the majority of such studies from Iran report a considerably low frequency of HPV association with CRC. An evaluation of 66 CRC patient samples confirmed the association of HPV in only 3 (4%) of these samples [182]. Another investigation reported a frequency of 6% of HPV DNA in CRC; with HPVs -51 and -56 as the most frequent (15.5%), followed by HPVs -16, -18, and -58 (10%), while, HPVs -31 and -33 had the lowest frequency (7.1%) [181]. In accordance with these results, other studies also reported fairly low HR-HPV frequencies. A study by Ranjbar and colleagues [184] reported HPV DNA in 6.25% of CRC cases, of which 7% of the cases had colon cancer while 4% had rectum cancer. Furthermore, HPV-18 was detected as the most frequent type [184]. Likewise, HPV was found in~3% of 70 adenocarcinoma colorectal tissues and 6% of adenomatous colorectal tissues, with HPV-16 as the most predominant genotype, followed by HPV-18 [183]. In another report, a lower HPV DNA prevalence in CRC patients was presented with only 1 as HPV-positive out of 100 CRC cases [185]. Moreover, Nosrati et al. did not detect any positive HPV cases in their cohort of 50 CRC samples [198]. Although the association of HPV in colorectal cancer may seem to be ambiguous in the Iranian population, an evident trend is observed in the gradually increasing number of HPV-positive cases, this may be due to recent developments in techniques used to detect HPV DNA in general.
On the other hand, data depicting the prevalence of HPV-association with CRC in an Israeli population are part of a large international study on populations from three different countries that included 106 patients from Israel [194]. As stated in this study, all samples were negative for all types of HPV. Therefore, it was concluded that there was no association between HPV and CRC [194].
Conversely, there are numerous studies regarding HPV association with CRC from Turkey. Five studies attempted to evaluate the presence of HPVs in the pathogenesis of CRC. Interestingly, two out of these studies reported the highest frequency of HR-HPV in CRC in the MENA region (81% and 82%) [187,188]; genotyping reported HPVs -18 and -33 as the most frequently detected types of HPVs in CRC tissues [187]. In addition to this, another study reported a considerably high prevalence of HPV-18 (76.4%) and HPV-33 (58.8%) genotypes in the Turkish population [189]. However, other studies from Turkey reported a comparatively low prevalence of HPV association with CRC. While one such study reported the detection of HPV in only 5 (7%) out of 72 colonoscopic biopsies [190], another research group from Turkey reported the complete absence of HPV genotypes among 106 colorectal carcinomas and 62 colon adenomas [191].
Evidently, HPV-16 and HPV-18 are the most commonly associated with CRC among the countries in the MENA region. However, it is of interest to note the high prevalence of certain regional strains of HPV, such as HPV-18 and HPV-33, which were largely identified by three out of five studies from Turkey. Another interesting finding pertains to co-infection cases with more than one HR-HPV type, as was noted by a few groups within the MENA region [53,178,189].

High-Risk HPVs in Breast Cancer
GLOBOCAN 2020 estimates breast cancer (BC) to be the most commonly diagnosed cancer, accounting for about 2.3 million new cases (11.7%) with a mortality rate of 6.9% globally [1]. As pointed out in our previous paper [199], the association between HPV and BC still generates substantial controversy. For instance, Khodabandehlou, N. et al., 2019, detected HPV DNA in 48.6% of BC samples vs. 16.1% in controls [200]. Such findings were supported by various similar reports [201,202]. Nevertheless, opposing studies reported a lack of HPV DNA in breast cancer samples, proposing the implausible association between HPV and the development of breast carcinomas [203,204]. Notably, some studies suggested that the prevalence of HPV in breast cancer is dependent on geographical locations [205]. As for the Middle East and North African region, studies were limited to Syria, Turkey, and Tunisia. Recent reports also included Algeria, Egypt, Iran, Iraq, Jordan, Lebanon, Morocco, Pakistan, Qatar, Syria, and Turkey (Table 4). Herein, we review all these studies.

In GCC Countries and Yemen
In the State of Qatar, Sher et al., 2020 [216] examined a cohort of 150 freshly obtained breast tissue specimens (50 benign breast lesions, 50 breast cancer, and 50 normal breast tissues) and reported the presence of high-risk HPV in 10% of the subjects with breast cancer, of which 12.12% were invasive carcinomas [216]. Concomitantly, our group examined 74 cases of breast cancer from 2008 to 2019 that were treated surgically in Hamad General Hospital, Qatar, and detected high-risk HPVs in 65% of the cases with a significant correlation between HPV+ breast cancer and triple-negative breast cancer subtype [217].

In Levant Countries
As compared to studies in the GCC, there are comparatively more studies in the Levant region analyzing the prevalence of HPV in breast cancer.
In Iraq, the frequency of HPV in breast cancer was evaluated by detecting the presence of HPV16 E7 protein; they reported an incidence rate of 30.67% in breast cancer patients [212].
Moreover, in Jordan, a recent study by Al Hamad et al., 2020 [213] examined the presence of multiple viruses, including HPV, in Jordanian women with breast cancer; this study revealed that HPV was detected in 21% out of 100 samples of sporadic breast cancers.
Similar to the Lebanese population, our group explored, for the first time, the genotype distribution of HPVs in BC samples from Syria. In this study, the authors analyzed the expression of high-risk HPVs, as well as correlated E6 oncoprotein and Id-1 gene expression in 113 Syrian breast cancer samples. Using PCR, we were able to establish a high HPV positivity (61%) with HPV33 as the most predominant subtype in this population (56%) [218]. Moreover, 24 of the 113 samples (35%) were coinfected with more than one HPV type [218]. Furthermore, the expression of the E6 oncoprotein correlated with Id-1 overexpression in the majority of invasive breast cancer tissue samples [218]. The study reported an association between infections with high-risk HPVs and human breast cancer progression in Syrian women [218].

In Maghreb Countries
Studies reporting the presence of HPV in breast cancer in Maghreb countries are scarce. In Algeria, HPV DNA was detected in 12% of breast tumor cases, with HPV16 as the most prevalent type accounting for 53.3% of HPV+ tumors [206].
Similarly, in Morocco, ElAmrani et al. examined the prevalence of mucosal and cutaneous HPV in tumors obtained from both controls and breast cancer patients [215]. The study reported HPV positivity in 25% of breast cancer cases and 8% of controls [215]. More specifically, the authors established the presence of both beta and gamma HPV types in breast cancer cases (10% and 7%, respectively) [215]. Notably, the study did not detect the presence of HPVs -16 and -18 in the samples; however, high-risk HPVs -51, -52, -58, -59, and -66 were found in~5% of breast cancer samples [215].
On the contrary, in Tunisian samples, Hachana et al. did not detect any HPV DNA in breast cancer samples [219].

In Other Countries of the MENA Region and Turkey
Contrary to the scarce data obtained from the GCC, Levant, and Maghreb regions, there are numerous studies in other MENA countries and Turkey analyzing the prevalence of HPV in breast cancer.
In Egypt, a very recent study reported differential expression of HPV in FFPE tissue (17%), fresh breast cancer tissue (50%), as well as white blood cells of breast cancer patients (40%) [220]. Another study by Tawfeik et al., 2020 [207] investigated the presence of HPV and immune T cells in Egyptian women diagnosed with breast cancer and reported that 20% of breast cancer cases were positive for high-risk HPVs, while benign lesions were not HPV-positive. On the other hand, another study reported a higher percentage of HPV-16 in non-inflammatory and inflammatory breast cancer cases (76% and 66%, respectively) [221].
Multiple studies were conducted to measure the prevalence of HPV in breast cancer patients in Iran; older studies reported a prevalence of more than 20% [224,225], while recent studies reported a minimal prevalence of 5.55% and 8.2% [181,210]. Recently, HPV DNA was detected in 12% of Iranian breast cancer samples, with HPV18 being the most prevalent subtype [209]. In addition, a comprehensive meta-analysis by Haghshenas et al. [208], including 11 studies with 1539 Iranian women, reported an estimated HPV prevalence of 23.6%. On the contrary, Jamal et al. [211] reported the complete absence of the HPV genome in 150 samples of breast cancer in Shiraz, Southwest Iran.
In the Turkish population, the first study by Gumus et al. [222] revealed that 74% of breast tumor tissue is positive for HPV-DNA, along with 32% of normal breast tissue samples. When it comes to their identified genotypes, HPV33 was commonly detected in both tumor and normal tissues (95% and 87%, respectively), followed by HPV18 (54% and 56%, respectively). Furthermore, a recent study by Balci et al., 2019 [223] investigated the presence of HPV in breast cancer and intraductal papilloma; the study revealed a high presence of HPV in both intraductal papilloma and carcinoma (30% and 44%, respectively).
In conclusion, most of the recent studies in the MENA region confirm the presence of HPV in human breast cancer and the effect of geographic locations on it. Therefore, we believe that high-risk HPVs are present and take part in the initiation and/or progression of breast cancers through the interactions of E5, E6, and E7 oncoproteins of HPV viruses, similar to those of cervical and head and neck cancers. However, it is clear that more comprehensive studies with large cohorts of samples are needed to clarify much of the controversy pertaining to HPV association with BC cases. Molecular studies elucidating the specific mechanism of the action of HPV infection in BC carcinogenesis are still nascent.

Prevention Strategies of HPVs Infection
Since HPV is largely transmitted via sexual activity, appropriate precautionary methods are the mainstay in preventing the spread of the disease. However, a number of prophylactic vaccines were also developed in recent times to prevent infections against both low and high-risk HPV types.
Under normal circumstances, the virus remains generally protected from the functional immune system, specifically antigen-presenting cells (APCs) and patrolling macrophages [226]. However, reports state that the generation of minimal antibody levels is often sufficient in preventing future infections against the same HPV genotype [226]. This is indicative of the fact that HPV prophylactic vaccines that could trigger the generation of neutralizing antibodies against the viral proteins of HPV will indeed offer enhanced prevention. Currently, three HPV prophylactic vaccines are on the market; details about these vaccines and their global use are discussed subsequently (Table 5). Cervarix TM is a bivalent HPV vaccine protecting against two HPV types: -16 and -18 [227]. The vaccine contains an equal composition of the L1 proteins of each of these HPV subtypes (16/18). This vaccine is produced in insect cells and formulated in an ASO4 adjuvant comprising alum and a toll-like receptor 4 (TLR4) agonist, MPL (3-O-desacyl-4'monophosphoryl lipid A) [228]. Cervarix TM is administered through an intra-muscular injection and is usually followed up with repeat doses at 1 and 6 months after the initial dose [226].
Results from the clinical trials of the vaccine indicate that it was highly immunogenic and capable of generating high titers of HPV 16/18 neutralizing antibodies and is well tolerated; thus proving to enhance activity against cervical intraepithelial neoplasia grade 2 (CIN2+) lesions expressing HPVs 16 and 18 [229]. According to another study, the vaccine showed the efficacy of nearly 90.4% against HPV 16 and 18 CIN2+ lesions [230], while providing cross-protection against HPV types 31 and 45, thus increasing its protection against cervical cancer by nearly 80% [231]. Moreover, Cervarix TM maintains an effect over a five years period [231]. On the other hand, as per the results of a study performing trials on participants of varying age groups, higher antibody levels for Cervarix TM were identified in the pre-teen/adolescent group in comparison with the 15 to 25 years age group [232]. This clearly indicates that higher antibody levels found in the younger age group could result in a longer duration of protection against the virus. The currently recommended age for administering Cervarix is 10 to 25 years [228].

Gardasil ®
Gardasil ® , a quadrivalent vaccine, is formulated through the generation of virus-like particles (VLPs) for each HPV type through the use of a recombinant Saccharomyces pombe vector and offers protection against infection with four HPV types, namely, HPVs -6, -11, -16, and -18 [233]. The purified VLPs for each HPV type, -6, -11, -16, and -18, are combined into 20, 40, 40, and 20 µg per dose, respectively, on an alum adjuvant [226]. Since this vaccine targets both high (HPVs 16 and18) and low (HPVs 6 and 11) risk HPV types, it can be used as a prevention measure against cervical cancers, as well as sexually transmitted diseases (STD), such as genital warts [228]. The vaccine is delivered through an intra-muscular injection as a 0.5 mL dose in a three-shot immunization protocol at 0, 2, and 6 months [226].

Gardasil ® 9
Another FDA-approved HPV-targeted vaccine is Gardasil ® 9. This vaccine is nonavalent and protects against nine HPV types, namely HPVs -6, -11, -18, -31, -33, -45, -52, and -58 [234], making it a much-required evolution over previous HPV vaccines, as it offers protection against a wider range of HPV types, including both high and low-risk HPV groups. Similar to Gardasil ® , Gardasil ® 9 is formulated on a similar VLP platform and is approved for use in both genders within the age group of 9 to 45 years [234]. The vaccine is able to offer nearly 90% protection against cervical cancer, which is indeed a virtual elimination of the disease in a wider context [235]. In addition, certain studies reported that Gardasil ® 9 also offers a 30% increased prevention of pre-cancer cervical lesions or CIN 2/3, relative to first-generation vaccines [236,237]. Moreover, apart from cancer, this vaccine is also able to provide approximately 75% to 90% prevention against other HPV-associated STDs [237,238].
Although the MENA region is not similar to western civilizations in terms of culture or religion, particularly when it comes to sexual behavior, there are a few social, cultural, and religious factors contributing to vaccine hesitancy [61]. Since the majority of MENA countries are Muslim-dominating ones, identifying the overall conceptions against vaccinations and studying Muslim-specific factors can aid in providing insight into the social and religious factors of vaccine hesitancy in these communities [239]. Various countries in the MENA region experienced a significant increase in vaccine-preventable diseases, including measles and influenza [240]. Concordantly, countries within the MENA region also opposed the initiation of anti-HPV health intervention programs (screening and vaccination) [241]. The majority of these countries saw a spike in the incidence of cervical and other HPV-related cancers, which can be prevented with appropriate vaccination programs. One of the most commonly detected HPV subtypes in the MENA region is HPV16, which is targeted by the currently available vaccines, and hence their use can help to prevent more than 70% of HPV-induced cancer cases in the MENA region. In September 2018, the Ministry of Health and Prevention in the UAE mandated the HPV vaccine for all female students from eighth grade upwards; however, the policy was met with public opposition resulting in the alteration of the Ministry policy to require parent approval prior to vaccination [241].
Evidently, HPV vaccines are well established in terms of their safety and efficacy. However, the applicability of these vaccines is often limited due to a huge gap in awareness [242]. Since HPV is sexually transmitted, such vaccines need to be targeted at adolescents between the ages of 9 and 15 years, typically prior to the initiation of sexual activity. To ensure high vaccine acceptance rates, the MENA region can benefit from campaigns addressing cultural and social concerns, as well as demonstrating safety and vaccine effectiveness.

Conclusions
In summary, there is sufficient HPV infection burden in MENA countries to warrant public health interventions and to emphasize the need for introducing HPV-based screening strategies and HPV vaccination programs; since it is clear that HPVs are associated with several types of human cancers, including cervical, head and neck, colorectal, and breast. The data presented herein on HPV genotype-specific distribution can provide a reference point to evaluate the efficacy of currently available HPV vaccines and may help healthcare authorities assess the impact of introducing HPV vaccination programs on cancer prevention. Additionally, sexual health education could also protect the MENA population from HPV and other sexually transmitted diseases.