Clinical relevance of the inhibitory effects of green tea catechins on prostate cancer progression in "high risk" men in combination with molecular profiling of catechin-resistant tumors.

CS15-03

Green Tea Catechins (GTCs) were proven effective at inhibiting cancer growth in several laboratory studies and different in vitro and in vivo experimental models. In addition, pioneer work has already demonstrated feasibility and safety of GTCs administration in healthy human volunteers. Beyond all the possible molecular hypothesis on GTCs action in human cells, and also considering that results obtained by epidemiological studies focused on a lower incidence of prostate cancer (CaP) in the Asian countries (where green tea is consumed regularly) as compared to Western populations are still controversial, a clear cut indication that a beneficial effect could also be obtained in a selected population of patients at high risk of CaP progression was timely needed. Prostate cancer (CaP) has been already ranked as the second leading cause of cancer-related death among men in Western countries, representing a major and fast-growing health and social problem. Lifestyle-related factors, and particularly diet, are considered to be the major contributors for CaP promotion. Because of unfavourable prognosis of high grade organ confined and extra-prostatic CaP, prevention may be the best approach to fight it at present time. The fact that CaP onset and progression takes considerable time to occur can be considered as an important opportunity for prevention studies. In fact, an effective protocol for treating pre-malignant lesions in high risk men, if successful, would result in important benefits for patients and substantial saving of social and health costs. Recent studies have shown that about 30% of men bearing high grade PIN (HG-PIN) lesions would develop CaP within one year as assessed by repeated biopsy. Since at present no treatment is given to these patients until CaP is diagnosed, we decided to fill this therapeutic void, in the hope that working with this clinical model would quickly address whether GTCs administration would be effective or not at preventing CaP progression. Therefore, we performed a pilot clinical trial for assessing the efficacy of GTCs administration for chemoprevention of CaP in HG-PIN volunteers. The cohort of patients included 60 HG-PIN volunteers that were enrolled after making them aware of the study and obtaining their signature on an informed consent form. The study was designed as double-blind and two-arms, placebo-controlled. Oral daily treatment was accomplished by giving three capsules containing 200 mg each of GTCs (total: 600 mg/day) and checking for compliance. After 1 year of treatment, only 1 tumor was diagnosed among the 30 GTCs-treated men (incidence: about 3%), while 9 cancers were found among the 30 placebo-treated men (incidence: 30%). Total PSA in GTCs-treated men was constantly lower with respect to placebo-treated ones, although the difference between the two arms never reached statistical significance. As a secondary observation, GTCs administration also affected IPSS (International Prostate Symptom Score) and QoL (Quality of Life) scores in men with coexistent BPH. Both scores clearly improved, reaching statistical significance in the case of IPSS and suggesting that GTCs administration might also be beneficial for treating BPH symptoms. No significant side or adverse effects were documented. To our knowledge, this is the first clinical study showing that GTCs are safe and very effective for treating pre-malignant lesions before CaP develops. Our finding suggests a new scenery in which the incidence of this disease could be greatly reduced by simply making GTCs available to the elders or high-risk men. This approach may result in a tremendous social and clinical impact, especially in the Western countries, although it appears rather obvious that the chemopreventive effect exerted by GTCs on human CaP development must be quickly confirmed by a larger study. Also because of these clinical results, the quest for a rationale explanation of the molecular alterations linked to GTCs action is important, but still wide open. Molecular or gene signatures are often used to model clinically relevant information (e.g. prognosis, survival time, sensitivity to drugs) as a function of gene expression data obtained at transcriptional level, but instead of individual genes, all signature components are used as predictors. By conventional Northern blot analysis, we previously identified a 8-genes signature that provided reliable prognostic prediction of human CaP. The prediction was further enhanced when molecular data were used in combination with standard clinical information. By this finding, we have shown that molecular characterization of CaP progression is indeed possible. We then proceeded further by determining the 8-genes signature in the well-characterized, pre-clinical TRAMP mouse model of CaP progression by RT-qPCR. The TRAMP model is a well known autochthonous transgenic animal model that was developed as an important tool for understanding the progression of human CaP, in that it displays in situ and invasive carcinoma of the prostate mimicking the whole spectrum of human CaP progression from PIN to androgen independent disease. Recent studies, including ours, have demonstrated that administration of GTCs is effective at inhibiting CaP development in these animals. Thus, we have validated our 8-genes signature in the TRAMP model, and particularly the down-regulation of CLU gene expression (which is a component of the signature) at mRNA and protein level during CaP onset and progression. On the contrary, upon GTCs administration, CLU expression is maintained at high levels in the prostate of TRAMP mice in which CaP development was strongly inhibited. In these mice, induction of pro-apoptotic nuclear CLU was detected at early stage of treatment. Linear discriminant analysis showed that the 8-genes signature was highly effective at discriminating the prostate of wild type from transgenic TRAMP mice spontaneously developing CaP (p < 0.0002). Since GTCs administration to TRAMP mice results in a substantial delay of CaP progression in 80% of the animals, while 20% remain unresponsive, we determined the 8-genes signature in the prostates of GTCs-sensitive and GTCs-resistant mice. The method significantly discriminated benign tissue from CaP. In fact, the category composed by wild type plus chemo-prevented, GTCs-sensitive TRAMP mice, in which CaP progression was strongly delayed, was discriminated from that of untreated TRAMP mice plus GTCs-resistant TRAMP mice, in which CaP developed irrespectively from GTCs administration (p < 0.01). More importantly, GTCs-resistant CaP was also significantly discriminated from both strongly delayed CaP still present in TRAMP mice responding to GTCs treatment (GTCs-sensitive; p < 0.0001) and spontaneously developing tumors of untreated TRAMP (p < 0.0001). Preliminary experiments in our laboratory have already shown that application of this method to a single tissue needle biopsy in humans is feasible and can detect CaP with sensitivity similar to pathological examination. Thus, RT-qPCR gene profiling, based on the signature composed by the 8-genes that we have identified, may represent an appropriate means for studying the biological behaviour of human CaP that may also bear potential prognostic value by providing a molecular classification for presence/absence of cancer and for discriminating GTCs-responsive from GTCs-resistant CaPs. This approach might also allow to explore the molecular basis of drug resistance. In fact, while the efficacy of GTCs in cancer growth inhibition has been well documented in several experimental models, little is known at present time about the possible mechanisms by which cancer cells can escape and acquire resistance to GTCs administration. The possibility to apply this molecular classification protocol to study the individual response to GTCs on needle biopsies collected before prostatectomy and during GTCs treatment would possibly enable us to discriminating aggressive CaPs and predicting final outcome. In the light of our recent result showing that chemoprevention of human CaP is achievable by GTCs administration; these results would take on a particular meaning for guiding the clinical management of this disease. In fact, the combination of GTCs treatment for men at high risk of CaP as first line prevention protocol, together with 8-genes signature profiling in tissue needle biopsies for real time monitoring of patient's response to discriminate responsive from unresponsive tumors, might importantly change in the near future the clinical managing of this highly diffuse malignancy.