Quercetin, Testosterone and Prostate Cancer - The Missing Link Kothandaraman Narasimhan1, Ralf Henkel1, 1Department of Medical Biosciences, University of the Western Cape, Bellville, South Africa Introduction: Quercetin, a bioactive flavonoid, has been identified as bioactive compound in Typha capensis, a South African medicinal plant which is used for the treatment of male fertility problems [1,2]. It possesses both pro-oxidant and antioxidant properties. We tried to investigate if quercetin could play a role in triggering testosterone synthesis and at the same time inhibit prostate cancer (PC) cells. The objective was to elucidate the underlying regulatory mechanisms at the genetic level for the above roles for quercetin. Fig. 5 Fig. 6 Figure 5. CYP family of genes involved in testosterone biosynthesis and their interacting genes. The interlinking genes (yellow) might hold the key for the determining the expression of CYP family genes involved in the synthesis of steroid hormones including testosterone. Figure 6. Processes regulated by quercetin related to testosterone metabolism involving molecular function, pathway interactions, biological processes as well as human phenotype and gene families. Material and Methods: Using Systems Biology tools, we performed Data Mining from PubMed, Medline and Scopus databases on studies referring to quercetin and testosterone and PC, respectively [3]. A total of 71 studies were reported for testosterone and quercetin while 154 studies were reported for quercetin and PC. Data for gene-gene interaction, gene-protein interactions as well as gene-metabolite interactions were obtained from the STITCH and Comparative Toxicogenomics Database, respectively. Functional annotation analysis was performed using tools such as GO Term Finder, GO Term Mapper, UniProt, and STRAP. Fig. 7 Fig. 8 Results: Figure 7. Pathways identified to be regulated by quercetin in the synthesis of testosterone. Genes /proteins /enzymes involved as intermediaries might hold key to synthesis of testosterone augmented by quercetin. Figure 8. Pathways affected by quercetin in PC. In PC, quercetin primarily activates genes responsible for increased oxidative stress, oncogenes and pro-apoptotic pathway associated genes. Figure 9. Seven genes (dark red) are the inter-linking genes between testosterone biosynthesis and PC. Quercetin-induced testosterone might trigger CASPASE activity during PC as Caspase family of genes were the most prominent in the interlinking group of genes. We also identified TBXAS1 (Thromboxane-A synthase) which might be linked to testosterone in the inhibition of PC. Quercetin might help in maintaining higher levels of IGF1 along with IGF1R, and possibly play a role in inhibiting PC cells in the presence of testosterone. Fig. 9 Fig. 10 Fig. 11 Table 1. Quercetin specific genes and their role in eliciting testosterone biosynthesis and secretion. Table 2. Quercetin specific genes and their role in prostate cancer. Fig. 1 Fig. 2 Figure 10. Flavonoids as drugs that could target specific genes associated with testosterone biosynthesis and metabolism.  Figure 11. Genes targeted by different groups of flavonoids for PC. Conclusions: Pathways, biological process, gene families associated with specific set of genes that were associated with testosterone biosynthesis and PC augmented by quercetin were summarized in the current study. Quercetin plays a key role in triggering testosterone synthesis as well as inhibition of PC through different regulatory mechanisms. The study showed both upstream and downstream regulators and markers for apoptosis were regulated by quercetin. We also show testicular and spermatogenesis rejuvenation though administration of quercetin. Quercetin targets PC cells through targeting mitochondrial pathways. Interlinking genes between testosterone synthesis and PC show a potential role for CYP, Caspases, IGF and TBXAS1 genes in the inhibition of PC cells mediated by quercetin. Novel drugs in the form of different classes of flavonoids were identified through computational approaches targeting specific genes for testosterone synthesis and inhibition of PC. Figure 1. Genes associated with Biological Pathways identified through datamining techniques. No overlap between genes under each category was found indicating a distinct response to quercetin for testosterone and PC, respectively. Figure 2. For the Biological Processes a similar trend, except for IGF1 & IGF1R, can be seen indicating a unique mechanism associated with testosterone synthesis and PC inhibition. Fig. 3 Fig. 4 References: Ilfergane A, Haines-Arries N, van Zyl L, Henkel R (2015) Investigations on the effects of Typha capensis on TM3 Leydig cells. Andrology (Suppl.): 72 Haines-Arries N, Ilfergane A, Henkel R (2015) The effect of an aqueous Typha capensis extract on the ageing male reproductive system. Andrology (Suppl.): 110-111 Narasimhan K, Abu-Elmagd M, Al-Qahtani HM (2016) Pathogenic landscape of idiopathic male infertility: new insight towards its regulatory networks. npj Genomic Medicine - Nature. (2016); 1, Article number: 16023. Figure 3. Gene-metabolite (quercetin) interaction in the human genome. Genes interacting with quercetin were identified using in silico approaches. Figure 4. Genes related to testosterone metabolism that are triggered or inhibited by quercetin. CYP family of genes were the majority class of genes involved in this process. Acknowledgements: This project has been supported by the South African National Research Foundation.