1. Introduction
Prostate cancer (PC) is the second most common cancer and the fifth most common solid tumor to cause death in men worldwide, with an estimated 1,400,000 new cases annually and a total of over 375,000 deaths each year. Its incidence and mortality rates vary between regions, being the highest in Northern Europe and Central America [
1]. In addition to its high prevalence, PC-related prognosis diverges with patients’ age [
2], ethnicity, stage [
3], and genetic background. The above, together with inherited susceptibility, obesity, and environmental influence, are also recognized as major risk factors for the disease [
4]. Currently, several germline variants of i.e.,
HOXB13,
NKX3.1, and
BRCA2 are associated with an increased risk of inherited susceptibility to PC. These mutations are more common in men with early-onset PC arising due to congenital defects in response to oxidative stress (e.g.,
NKX3.1) or DNA damage repair mechanisms (
BRCA2); therefore, they may predict a more aggressive course of the disease. On the other hand, these variants are of relatively low frequency among all PC cases and do not resemble the etiology of sporadic PC [
5,
6,
7].
PCs are considered a flagship example of the intra-tumoral heterogeneity standing behind the inequities in the course of the disease observed between patients. Such complexities arise from the multifocal nature of the disease currently often associated with the clonal branching evolution of different molecular architectures and genomic burdens that ultimately poses a barrier to therapeutic efficacy [
8,
9,
10]. It may be inferred that the loading of the genomic alterations, both germline and somatic, has a predominant impact on the development and progression of the tumor [
11]. In fact, these are the actual markers driving the individual trajectory of PC, whose prediction, contrary to general opinion, lies beyond the routine histopathological features.
Radical prostatectomy (RP) is one of the primary treatment options for localized PC, and it has excellent oncologic outcomes. Despite the good overall control of the disease progression after RP, 20–30% of patients experience PC recurrence that manifests in an increase in the prostate-specific antigen (PSA) in the serum without any clinical evidence of metastatic disease (MD) [
12]. A PSA elevation is thereby an indicator of remaining prostatic tissue, denoting the presence of PC cells at local or distant sites. Although biochemical recurrence (BCR) anticipates PC progression, the increase in the PSA concentration may be prolonged and does not always lead to clinically apparent metastases [
13]; nevertheless, it has been reported that the 5-year risk of clinical progression (CP) in men with BCR ranges from 27% to 60% [
12].
In the current recommendations, the European Association of Urology (EAU) proposes risk group classification combining the Gleason grading score (GGS), clinical stage (TNM), and initial PSA level [
14]. This classification derived primarily from the study by D’Amico et al. [
15], which was based on the stratification of patients with a similar risk of BCR at the time of primary intervention (RP or external beam radiotherapy (EBRT)) and is commonly used in clinical settings [
16].
The clinical use of PSA as a routine marker of PC is now up for debate due to many controversies. In particular, among symptomatic patients, the specificity of PSA was found to be as low as 3% at 96% sensitivity; however, these estimations varied between different studies and applied only to the PSA threshold of 4 ng/mL in PC detection [
17]. This was explained by the fact that PSA is not tumor-specific, but rather an organ-specific marker that is entirely produced by the prostatic gland [
18]. It is also a prostate differentiation marker; thus, tumors with higher Gleason scores that have a more aggressive clinical course tend to express lower values of PSA [
19]. Moreover, the contribution of the tumor alone to the elevated PSA value is unpredictable, as it may also be derived from an enlarged prostatic gland with hyperplasia, prostate inflammation, or manipulation by a prostate massage or biopsy. Additionally, studies show that the range of PSA values increases with age, and so this marker should be interpreted with caution and considered collectively with other clinical parameters [
20]. Therefore, the use of PSA as a screening tool involves the risk of overdiagnosis and overtreatment, causing patients with insignificant cancer to be subjected to unnecessary treatment for an indolent disease. Nevertheless, the standard PSA threshold of 4 ng/mL, determined to maximize cancer detection, is currently considered too low and causes the misidentification of low-grade or benign cases [
21]. More importantly, there is no consensus regarding the levels of PSA defining BCR following RP. The values suggested in the current literature range between 0.2 and 0.6 ng/mL, with values above the cutoff of 0.4 ng/mL best predicting further progression. The value of PSA after RP is not expected to exceed 0.1 ng/mL, while values above 0.1 ng/mL are recognized as the most indicative of residual prostate tumor tissue [
22,
23]. Regardless, PSA is widely used in many nomograms (e.g., EAU risk groups) to estimate the risk of BCR, but also as a part of various assessment tools by Boorjian [
24], Briganti [
25], and Partin [
26] to evaluate the risk of CP and cancer-specific and overall survival (CSS and OS, respectively) rates after an RP of acceptable accuracy.
Apart from PC cases that meet the EAU recommendations for PSA-based prognostication, of the utmost importance should be distinguishing aggressive from indolent tumors of high recurrence potential. Recently, studies have described specific subgroups of patients classified with a low GGS, PSA level, and/or disease risk who presented unusually aggressive courses of PC, as observed in a clinical routine [
27]. All of the above prompted us to investigate the molecular mechanisms underpinning distinct trajectories of PC progression that could be adopted in clinical care and better stratify patients with rapid recurrence in spite of the favorable primary prognosis.
The epithelial-to-mesenchymal transition (EMT) is an essential process during cancer progression enabling tumor cells to invade local tissues, disseminate, and ultimately form distant metastases that naturally occur during tissue remodeling or embryogenesis. Specifically, this cellular mechanism implies the loss of function and structure of epithelial cells that, at the end of the transition, present a mesenchymal phenotype and therefore acquire migratory and invasive properties. The EMT is regulated by various transcription factor (TF) families, such as Zeb (Zeb1, Zeb2); Snai (Snai1, Snai2); and Twist, switching the expression profiles of specific genes determining either the epithelial (e.g.,
CDH1) and/or mesenchymal state (e.g.,
FN1,
CDH2,
VIM). As a result, it involves the remodeling of the cytoskeleton and local tissue architecture, the loss of cell–cell junctions, changes in cell polarity, and the destabilization of interactions with the extracellular matrix (ECM), ultimately allowing the cells to escape from the primary tumor site. Once the new foci in a distant tissue have been formed, the cells regain their epithelial character through a reverse program—a mesenchymal-to-epithelial transition (MET), enabling the colonization of a new niche. Many growth factors and signaling pathways orchestrate the EMT, dictating thus the nature of neoplastic cells and the trajectory of cancer progression [
28,
29]. Notably, it has been shown that the specific profiles of the EMT reflect the clinically observed Gleason score delineating the levels of cellular de-differentiation within the PC foci [
2], likely as a transcriptional response to either androgen or estrogen signaling axes [
30].
In previous studies, other important factors affecting the mechanism of PC recurrence and progression (i.e., EMT) were shown, such as age and signaling by steroid hormone receptors (
AR,
ESR1,
ESR2), revolving around the remodeling of the tumor tissue architecture and encouraging more aggressive clinical behavior from PC cells, consequently tipping the odds to favor the establishment of overt PC progression among specific subgroups of patients [
2,
3]. However, these studies did not go beyond the Gleason score to routinely classified subgroups of patients according to, e.g., the EAU guidelines and did not correlate the molecular profiles to any specific prognosis. Nevertheless, BCR is considered a primary sign of PC progression and a more aggressive course of the disease, although its accurate diagnosis utilizing routine PSA levels in the serum is generally perplexing and may lead to poor patient outcomes. Altogether, the above prompted us to determine the association of BCR with its molecular drivers, i.e., to identify functional biomarkers of pivotal relevance in EMT with regards to clinical parameters such as PSA, GGS, and T score to assess the risk of BCR at the time of primary treatment and enable the stratification of the potential for a more aggressive course of PC. We designed the study to be a priori oriented towards the genes relevant to the EMT to present a holistic view of the molecular aspects of PC progression using a set of functional analyses, which resulted from the molecular function of the genes and gene sets explaining the observed phenotypes and outcomes.
3. Discussion
PC is the major cancer-related cause of death among males worldwide [
1]. The progression of PC is preceded by BCR, manifesting in an increase in serum levels of PSA. It is estimated that approximately 20–30% of patients will experience BCR in the 5 years following treatment, and, more importantly, 24–34% of them will develop PC metastasis with a high burden of lethality [
32,
33,
34]. In our study, during the overall follow-up time of 12.6 years (4604 days) post-RP, 72 patients (14%) experienced BCR events, with a 5-year rate of 64% (95% CI = 56–74%,
Supplementary Figure S1). Our observations were similar to those from the study by Han et al. of 2091 PC patients reporting a BCR rate of 17% during 17 years of follow-up and utilizing the same cutpoint for serum PSA of 0.2 ng/mL to define BCR [
35].
Currently, multiple treatment modalities are available for advanced or metastatic castration-resistant PC (mCRPC), although they are largely considered palliative options and prolong the median survival time only to a marginal extent [
36,
37,
38,
39]. In clinical practice, the diacritic course of PC is very heterogeneous and often progresses with a high degree of disparity observed between patients of similar characteristics. The paradigm of restricted therapeutic outcomes together with an unclear silhouette of PC in an individual is now beginning to shift research interests towards the potential of an accurate stratification of the recurrence risk, i.e., BCR progression. Interestingly, this phenomenon was confirmed, as an illustrative instance, in the clinical characteristics of the PC cohort analyzed in this study. In general, as reported in the literature, the risk of BCR tends to increase with high levels of PSA and an advancing pathologic stage, GGS, and lymph node status [
35]. The EAU-EANM-ESTRO-ESUR-SIOG guidelines adopted a model by D’Amico et al. stratifying BCR prognosis by attributing patients with the above features, which, when combined, defined the risk as either low, intermediate, or high, a crucial step for further disease control [
15]. While in our study the majority of patients were diagnosed with stages cT2c-cT4 (467 patients, 94%) and/or locally advanced disease (303 patients, 60%), many of them were diagnosed with a preoperative PSA level < 10 ng/mL (329 patients, 66%); at the same time, only 72 (14%) patients experienced actual BCR or showed positive lymph node status (80 patients, 16%) (
Table 1). With such heterogenic phenotypes, many patients might not share the improvements in their disease management, being a vastly different subset of a particular EAU risk group. Indeed, they were characterized by separate clinical entities arising from a set of molecular properties culminating in PC of a higher invasiveness; even with initial good prognosis or despite their unfavorable characteristics, they were devoid of metastatic potential and thus will never progress beyond PSA—only recurrence. Therefore, the current stratification of the risk of BCR in clinical practice was deemed ineffective, either underscoring or overestimating such cases, especially regarding the recent debate on PSA’s usefulness and its accuracy in predicting the risk of BCR [
12]. In support of the above, we showed that preoperative PSA values grouped as suggested in the EAU recommendations (<10 ng/mL, 10–20 ng/mL, ≥20 ng/mL) were not significant surrogates differentiating BCR prognosis (
p = 0.72,
Supplementary Figure S3) in an independent manner, even though this was opposed to the available body of research (e.g., [
13]). In turn, we established a cutpoint for the PSA level of 6.9 ng/mL that best differentiated the risk of BCR reaching an almost two-fold rise (
Figure 1,
Table 1) and was greater than the generally accepted level of 4 ng/mL utilized for PC screening [
21].
An evolving body of research has attempted to provide a better framework for the prediction of BCR progression, going beyond the clinical characteristics per se, which, like PSA, are disputable, and enriching them with a molecular landscape reflecting the clinical behavior of PC. The above was also a rationale for our study, meriting an accurate stratification of PC patients deemed to be at an increased risk of a lethal course of the disease, which is, in fact, dictated by specific profiles of molecular markers of functional relevance in the mechanism of PC progression. For instance, the latest study by Pellegrino et al. employing the Decipher
® dataset showed that preoperative PSA blood levels poorly discriminated BCR, the development of metastasis, and PC-specific mortality (PCSM), with an area under the curve (AUC) of 50%, 51.5%, and 50.9%, respectively. At the same time, the study revealed the much higher accuracy of GGS, T score, and
KLK3 encoding PSA in predicting these events [
40]. In parallel, we showed that even the optimized cutpoint for the preoperative PSA level was not superior in predicting BCR to the expression of functional markers involved in transcriptomic reprogramming that appeared to be significant in PC recurrence, as shown in previous studies [
2,
3]. In particular, we found that the expression cutpoints determined for
PGR,
KLK3,
CDH1, and
MMP3 indicated a much higher risk (HR > 2) of BCR than preoperative PSA level, whereas the expression of
ESR1 and
VIM showed a comparable association (
Figure 1,
Table 1). Moreover, it is worth noting that a higher expression of
KLK3 correlated with better clinical outcomes (HR = 0.423, 95% CI = 0.265–0.677,
p = 0.0002,
Figure 1,
Table 1), and this finding was consistent with other research demonstrating that patients with positive lymph nodes, BCR, and metastatic disease, as well as those who died from PC, had significantly lower expression levels of
KLK3 [
9,
40]. The discrepancies between the serum PSA level and the tissue expression of KLK3 may be explained by the fact that during cancer development, there is an increased release of PSA into the blood [
41]. Low expression levels of KLK3 are observed in poor-prognosis PC as a result of a loss of tissue differentiation [
42]. On the other hand, some studies suggest that a higher expression of KLK3 may be associated with an indolent course of PC through KLK3 antiangiogenic activity [
43,
44]. It should also be noted that the alterations observed at the transcriptomic level are in fact a first line of response to signals received from the environmental milieu, though rarely translating into the expression of the corresponding proteins in a comparable ratio.
The androgen receptor is known for its role in the development and function of a normal prostate, but it is also an essential driver of prostate tumorigenesis. As a TF, it exerts specific effects in cells through the modulation of target genes followed by recruitment or crosstalk with other TFs and signaling pathways [
45]. Since Huggins’ publication in 1941 on surgical castration in advanced PC with exceptional palliative effect, AR has become the main domain of interest in the treatment of locally advanced and metastatic PC [
46]. Therefore, androgen deprivation therapy (ADT) achieved by pharmacological or surgical castration has become a therapeutic mainstay for such cases, as well as for adjuvant treatment in patients with BCR after primary local treatment [
47]. As was shown, some of the tumors lost the expression of
AR, but most retained it to reactivate the AR signaling axis under conditions of androgen refraction. By acquiring gain-of-function mutations, PC cells adapt to the low availability of androgens and de-differentiate into highly lethal mCRPC, which is in fact anticipated by BCR [
48]. We previously reported that a higher expression of
AR was associated with unfavorable disease-free survival (DFS) among PC patients, although the negative effect was diminished with progressing age, ultimately shifting in favor of signaling through
ESR1 [
2]. Surprisingly, in the present study involving the same group of patients, the expression of
AR was insignificant with regards to BCR (
Figure 1,
Table 1).
The overt role of AR in the prostate gland and PC puts it in the spotlight as a major research interest but, at the same time, should not detract from the relevance of other hormonal receptors such as estrogen or progesterone receptors (ER and PGR, respectively) in the evolution of PC [
49,
50,
51]. The role of ER in PC progression has been debated since the local expression of estrogens and aromatase converting testosterone to E
2 was detected in the malignant tissue of the prostate, thus showing that a single hormone may exert different effects depending on the receptor that it interacts with [
52].
Bonkhoff et al. in 1999 revealed for the first time an increase in ESR1 expression correlating with metastatic PC lesions including lymph nodes [
53] and, years later, demonstrated that progressing PC bypasses the androgenic cascade in favor of the re-emergence of the alternative ESR1 steroidal pathway [
51], which resembled our findings.
These observations, pertaining to the clinical management of PC, underlaid, for instance, a clinical trial of selective ER modulators (SERMs) whose administration culminated in the prevention of further PC progression as a major clinical outcome in men [
54], which had only been shown in vivo through the antagonism of ERα, not ERβ [
55]. Moreover, compelling data demonstrate a significant contribution of estrogen signaling in the EMT, a propulsive factor in PC progression, invasiveness, and drug resistance [
56]. Another piece of evidence supporting the deadly dualism of AR and ER in the trajectory of PC may also originate from their transcriptional targets, 80% of which, as we revealed, overlapped between the TFs, and which comprised a total of over twelve thousand genes, including major EMT effectors (
Table 2). The above is in agreement with still-relevant suggestions to implement SERMs into the standard of care due to the fact that both androgens and estrogens may affect the local architecture of the PC cells through the direct governance of the EMT program, accounting for disease progression [
57].
The molecular abundance of the pathways leading to BCR is a remarkable avenue in the improvement of risk stratification during the evolution of PC. Our previous investigations elucidated that the clinical manifestation of PC is mediated by the set of cellular effectors, i.e., the genes linked to the invasive properties of the tumor acting in concert [
3] and, more importantly, in combination with clinical features such as GGS or age [
2]. Even with the highest discriminative potential, none of the biomarkers could stratify the BCR risk individually. We subsequently attempted to extricate subgroups of PC patients with a markedly increased risk of BCR who shared a common profile of unfavorable alterations. Through the UpSet analysis, we identified 296 PRAD patients (60%) with simultaneous heightened
ESR1 and
MMP3 at the time of the primary treatment, which significantly correlated with worse BCR-free survival. Patients with that signature, termed in our study the stratum, showed significant disparities in regards to not only BCR (HR = 2.2, 95% CI = 1.3–3.6,
p = 0.003;
Figure 2,
Table 2) but also other major clinical parameters. In particular, the carriers of the stratum were associated with worse clinical prognosis in comparison to similar clinical groups, i.e., regarding the lymph node status, GGS, T score, and EAU risk-associated stage group (
Figure 2,
Table 2). Importantly, stratum-positive patients classified with the same BCR risk group by EAU guidelines tended to be much more susceptible to PC progression or even had worse outcomes than those classified with a higher risk. More specifically, stratum-positive patients with Gleason 7 (4 + 3), considered to be at an intermediate risk of BCR by the EAU (5-year BCR-free rate = 48% (95% CI = 27–85%)), were at a greater risk of BCR than patients with Gleason 8 (5-year BCR-free rate = 78% (95% CI = 61–100%)) or, surprisingly, even patients with Gleason 9 (5-year BCR-free rate = 62% (95% CI = 44–87%)) (
Figure 2,
Table 2).
The involvement of the regional lymph nodes, classified as N1 in PC, corresponds to locally advanced disease and is regarded as a high-risk feature of BCR in addition to the PSA level or GGS. We managed to find that stratum-positive patients with simultaneous N0, therefore not considered at a high risk of recurrence, had an unexpectedly greater risk of a BCR event than the non-carriers of the stratum with invaded lymph nodes (N1). As a notable point, the combination of the
ESR1 and
MMP3 signature with N1 status put the patients at the highest risk of BCR (
Figure 2,
Table 2). In addition to the above, BCR appeared much more often at an early stage (up to 1-year post-RP) among the latter (40.3%), thus representing an overwhelming majority in comparison to the stratum-negative subgroup (12.5%). The above is all the more significant as it was demonstrated by Venclovas et al. that BCR occurring up to 1-year post-RP together with the involvement of the lymph nodes is an essential predictor of failure in PC management [
58].
Pelvic lymphadenectomy (pLND) during RP failed in the improvement of oncological outcomes and survival. On the other hand, it provided crucial information regarding staging, and therefore prognosis, that could not be obtained by any other available procedure [
26,
59]. The decision to perform a pLND is made upon the preoperative estimation of the probability of lymph node invasion based on various nomograms (involving GGS, PSA level, and T score) that have shown comparable diagnostic accuracy (Briganti, Partin, MSKCC), while 94% of patients were shown to be correctly staged [
60]. If the estimated nomogram risk exceeds 5% nodal involvement, it is an indication for pLND, whereas, in patients with a low-risk disease, this procedure is not performed during RP. Of special emphasis are thus our findings regarding the actual implications for PC patients, that those classified primarily with a low risk of progression should not undergo pLND, but if harboring the stratum, and thereby being exposed to a higher risk of BCR, they might benefit from a pLND.
As mentioned above, we did not observe differential BCR-free survival according to the EAU-recommended PSA level groups (
Supplementary Figure S3). Instead, we showed a comparable risk of BCR in stratum-negative patients that did not increase in different PSA-level groups (considered as presenting either a low, intermediate, or high risk of BCR), although this finding was limited by the low number of events in that group. On the other hand, patients harboring the stratum presented not only a higher frequency of the BCR events, but also an advancing risk corresponding to the PSA level, with an HR = 1.79 (95% CI = 0.92–3.49) for PSA < 10 ng/mL; HR = 2.23 (95% CI = 1–4.97) for PSA 10–20 ng/mL; and HR = 2.8 (95% CI = 1.16–6.94) for PSA > 20 ng/mL (
Figure 2,
Table 2). Integrating the available data, there was significant compliance in the area of the preoperative factors predicting BCR, which included PSA level, T and N scores, GGS, and risk classification by the EAU; however, as expected, GGS ≥ 8 and PSA ≥ 20 ng/mL were considered the strongest surrogates of BCR. By utilizing CA, we revealed that separate clinical features allocated PC patients to the high-risk group of BCR, including GGS ≥ 8, advanced T and N1 status, and PSA ≥ 20 ng/mL, which, consistent with the above, were considered indicators of an aggressive course of PC; in addition, these features corresponded to not only BCR itself but also the presence of the molecular
ESR1 and
MMP3 signature that was determined to anticipate unfavorable outcomes (
Figure 3). Of the utmost relevance is the fact that the latter effects were reflected by the
ESR1-driven molecular landscapes of the EMT effectors enhanced by
MMP3 activity. Specifically, the escalated invasive characteristics of the PC among stratum-positive patients likely emerged from the mesenchymal nature of the tumor cells, namely their capability to migrate, disseminate, and form metastases (
Figure 4), thus predisposing them to a more aggressive course of PC, which we also observed in previous studies [
2,
3]. Remarkably, clinical features such as stage, T and N scores, PSA level, and GGS combined with the stratum corresponded to a heightened expression of mesenchymal-state markers such as
CTNNB1,
FN1,
MMP2,
MMP3,
MMP9,
CDH2,
ACTA2,
SNAI2,
VIM,
ZEB1, and
ZEB2, accompanied by a decreased expression of epithelial markers such as
CDH1,
LAMA1, and
KRT18 (
Figure 4). Additionally, with the elevated risk of BCR among the stratum-positive group, patients demonstrated an elevated expression of mesenchymal-state markers even when compared to clinical groups of worse prognosis, i.e., stratum-positive N0 vs. stratum-negative N1, stratum-positive localized PC vs. stratum-negative locally advanced PC, stratum-positive PSA < 10 ng/mL vs. stratum-negative PSA > 20 ng/mL, hence explaining the BCR-related failure in these groups (
Figure 2,
Table 2). The most essential discovery of this study, and at the same time the major conclusion that may be drawn from it regarding the potential clinical implications, was the case of the PC patients collectively classified in the EAU high-risk group for BCR by any of the clinical determinants, such as PSA ≧20 ng/mL, >T2c, N1, and GGS ≧8, who showed an even poorer prognosis of BCR, with an over two-fold increase in HR when the stratum was present (
Figure 2,
Table 2). This finding ultimately proved that the molecular drivers involved in the EMT program, which we determined in our study, strongly predisposed to a heightened risk of BCR and contributed to a more aggressive course of PC, irrespective of the clinical features that are taken into account in standard clinical settings. We speculate that these various trajectories of PC have their origin in the branching clonal evolution of the tumor cells, which manifests in multiple foci diverging in terms of genomic loading and histomorphological features such as the Gleason score, considered separate entities, albeit of a common progenitor (e.g., [
61,
62,
63,
64]). This phenomenon is currently explained through several types of clonal expansion (e.g., linear, branched, neutral, or macroevolution), which involve catastrophic rearrangements within the genome such as chromoplexy, chromothripsis, and kataegis [
65]. However, more and more evidence indicates the significant contribution of the non-genomic programs culminating in cell plasticity, especially EMT [
66], generating numerous phenotypic states of the same genome and enabling PC cells to escape from therapeutic pressure [
67]. Moreover, the specific profiles of the EMT were shown to reflect particular Gleason patterns and thus, indirectly, a subpopulation of PC, arising from signaling via the
AR and
ESR1 axes. As has been shown, during PC progression, the cells favor the latter, providing the advantage of an alternative source of steroidal signaling activated to retract from the androgens; hence, these patients become an AR-negative subpopulation, proving the initial potential for an aggressive course of PC and constituting a stratification niche preceding progression into CRPC or even mCRPC [
68]. This may be associated with a switch in the relevance of the hormonal signaling occurring along with the ageing soma, which we previously demonstrated [
2,
3] and stands in agreement with the theory of age-induced carcinogenesis [
65]. Finally, we were able to cross-validate the findings with the independent cohort of Rubicz et al. [
31] showing a similar trend of an EMT shift towards the mesenchymal state with the heightened expression of
ESR1 and MMP3, notably marked according to the stage of PC (localized/locally advanced) and the GGS (
Figure 5), which corresponded to our conclusions and proved the accuracy of the study.
In summary, BCR is a determinant of PC recurrence significantly increasing disease lethality through evolution to mCRPC. Therefore, the accurate prediction of the BCR risk is of the highest urgency in the management of PC patients. Our study provided evidence that specific molecular signatures of ESR1 and MMP3 predispose patients to experience unfavorable outcomes at the time of RP, even when analyzed in similar or different clinical groups that were primarily designed to stratify patients as having a low, intermediate, or high risk of BCR. We showed that patients collectively classified into the EAU high-risk group for BCR by all of the clinical determinants were at a much higher risk of BCR, with an over two-fold increase in HR when the expression of ESR1 and MMP3 was heightened. Furthermore, we demonstrated that the PSA level, despite its common use as a component of BCR stratification groups, had a poor correlation with BCR risk altogether. We additionally indicated that stratum-positive patients could benefit from pLND even when classified as being at a low risk of BCR by available clinical determinants. Nevertheless, as with any scientific study, our work was not without its limitations, such as the relatively small subgroups of patients sharing specific characteristics and the limited possibility of cross-validating the results, drawing a direct comparison, and implementing the results in clinical standards.
In overall, it is surprising that such fundamental factors as ESR1 have not been investigated yet for their potential to prognosticate PC aggressiveness. Therefore, we hypothesize that ESR1 has a major role in PC development and progression and could become a major focus of further investigations in PC theragnosis. Presumably, ESR1 together with MMP3 orchestrates the molecular landscape of clonal branching evolution, illustrating PC progression much better than the Gleason score, BCR, or PSA itself.