Report on Second International Conference on Natural Products for Cancer Prevention and Therapy Held in Kayseri, Turkey, 8–11 November 2017

Scientific experts from eight countries gathered[...].


Preface
Scientific experts from eight countries gathered to share their views and experience on the latest research on natural products for cancer prevention and therapy. The traditionally used herbal medicines, medicinal plants, plant extracts, fractions, and phytochemicals for cancer prevention and therapy were discussed throughout the meeting. The scientific program comprised of 12 plenary lectures, 23 oral presentations, and 72 posters, providing an opportunity for more than 130 natural product scientists to present their research in three days. Abstracts for plenary talks, oral presentations, and posters were published as proceedings of the meeting in the special issue of Proceedings, Volume 1 and Issue 10 (http://www.mdpi.com/2504-3900/1/10). The aim of this biannual meeting was to foster discussion and disseminate the results of the research on natural products that are used for cancer prevention and therapy. During the meeting, the scientific committee members of the meeting who attended the conference had been selected as judges to evaluate all of the oral and poster presentations and the three best oral and poster presentation awards have been granted to the young scientists. The participants were able to network and engage in discussion for potential collaboration to advance our knowledge on utility of natural products for prevention and treatment of cancer.

Plenary Lectures
The meeting was successfully focused on the natural products being investigated for their efficiency in several cancer types and for their potency in cancer prevention. Only the plenary lectures have been summarized here in this manuscript, and all of the other oral and poster presentations have been listed where the abstracts can be reached from http://www.mdpi.com/2504-3900/1/10. Growth factors are one of the main factors responsible from the uncontrolled cell progress in cancer. Up to date many scientists have focused on these factors either as the marker or as the targets in several cancer types. Yerer has presented a plenary lecture on the natural products targeting these factors (Nerve growth factor (NGF), epidermal growth factor (EGF), hepatocyte growth factors (HGF), fibroblast growth factors (FGF), vascular endothelial growth factors (VEGF), platelet derived growth factor (PDGF), and transforming growth factor (TGF-β) (http://www.mdpi.com/2504-3900/1/10/979) [1].

Anupam Bishayee
The presentation of Bishayee highlighted studies on cancer preventive and therapeutic attributes of various naturally occurring agents and underlying mechanisms of action, with special emphasis on results reported from our laboratory. Current limitations, challenges, and future directions of research for successful cancer drug development based on natural products will also be discussed (http://www.mdpi.com/2504-3900/1/10/982) [2].

Novel Anticancer Capacities of Saffron Amr Amin
Amr Amin has presented a plenary lecture on the anticancer effects of the saffron's main active ingredient "safranal" against HCC using in vitro, in silico, and network analyses. In their studies, in addition to the unique and differential cell cycle arrest, safranal showed pro-apoptotic effect through activation of both intrinsic and extrinsic initiator caspases implicating ER stress-mediated apoptosis (http://www.mdpi.com/2504-3900/1/10/834) [3].

Marc Diederich
This plenary lecture focused on Cardiac Glycosides (GCs) can be considered as pharmacological agents, allowing for cancer cells to switch from one cell death modality to another. All the findings encourage to further explore a potential for CGs in general as cancer cell death modulators alone or in combination with other targeted treatments (http://www.mdpi.com/2504-3900/1/10/972) [4].

Ins and Outs of Flavonoids in Cancer Prevention vs. Cancer Therapy: A Lesson from Quercetin in Leukemia
Gian Luigi Russo, Maria Russo, Carmela Spagnuolo, Idolo Tedesco, Stefania Moccia Russo et al. has critically reviewed the clinical and pre-clinical studies on the concept that polyphenols, being antioxidant compounds, can fight cancer. They suggest that a clear distinction must be done between the use of polyphenols, such as flavonoids, in cancer treatment versus cancer prevention, starting from adequate and specifically selected cellular models. As an example, he has present data on the potential application of quercetin against chronic lymphocytic leukemia (CLL) (http://www.mdpi.com/2504-3900/1/10/977) [5].

Anticancer Potential of Flavones
Randolph RJ Arroo, DidemŞöhretoglu, Demetrios A Spandidos, Vasilis P Androutsopoulos Flavones are abundantly present in common fruits and vegetables, many of which have been associated with cancer prevention. Taking into account that no flavonoid based drugs are clinically used in cancer therapy, Randolph has focused on the flavones-which constitute a subgroup of the flavonoids-show some structural analogy with estrogen, and are known to interact with human estrogen receptors, either as agonist or as antagonist. Thus, whereas epidemiological and pre-clinical data seem to indicate a high potential for flavonoids, from the point of view of the pharmaceutical industry and drug developers, they are considered poor candidates (http://www.mdpi.com/2504-3900/1/10/975) [6].

Adriano Borriello
The relevance of these mechanisms and their translation in clinical therapy has been discussed in Borelli's plenary lecture. Resveratrol and its mechanism of action has been emphasized by her in cancer cells and in experimental models of senescence, inflammation, obesity, and metabolic diseases. Its molecular targets act at different levels: (1) specific molecular pathways (like p53, NF-kappaB, PKC, PI3K, MDM2, LATS1, STK3 and several others); (2) epigenetic control of gene transcription through sirtuin activation; (3) cell division cycle and differentiation; (4) apoptosis and autophagy; and, Human infection with HCV is currently recognized as the leading cause of hepatocellular carcinoma (HCC), which demands liver transplantation, which was estimated to result in ∼10,000 deaths in the US only in the year 2011. Elsebai has presented a plenary lecture on cynaropicrin as a potential agent for treatment and prevention of HCC by indirect way through inhibition of HCV and in a direct way evidenced by the many antitumor activities in literature (http://www.mdpi.com/2504-3900/1/ 10/974) [8].
2.1.9. Relationship between Structure of Phenolics and Anticancer Activity

Müberra Koşar
Many phenolic compounds have been investigated for their potential use as cancer chemopreventive agents. Phenolic compounds consist of one or more hydroxyl substitution on the aromatic ring system. Koşar has emphasized that Cinnamic acid esters, such as caffeic acid phenethyl and benzyl esters, display selective antiproliferative activity against some types of cancer cells. Flavonoids consist of a large group of polyphenolic compounds having a benzo-γ-pyrone structure, and are ubiquitously present in plants. This structure can be responsible from the anticancer acitvities of these compounds (http://www.mdpi.com/2504-3900/1/10/978) [ Srivastava's presentation mainly focused on the combination of BRAF inhibitors with Mcl-1 inhibitor such as piperlongumine may have therapeutic advantage to melanoma patients with acquired resistance to BRAF inhibitors alone or in combination with MEK1/2 inhibitors (http://www.mdpi. com/2504-3900/1/10/981) [12].

Conflicts of Interest:
There is not any conflict of interest to declare.