Prostate Cancer Chemoprevention Targeting Men with High-Grade Prostatic Intraepithelial Neoplasia (HGPIN) and Atypical Small Acinar Proliferation (ASAP): Model for Trial Design and Outcome Measures

Prostate cancer chemoprevention by natural agents: Clinical evidence and potential implications

Prostate cancer (PCa) is the most common non-skin cancer and the second leading cause of cancer-related deaths in American men. Due to its long latency period, PCa is considered as an ideal cancer type for chemopreventive interventions. Chemopreventive agents include various natural or synthetic agents that prevent or delay cancer development, progression and/or recurrence. Pre-clinical studies suggest that many natural products and dietary agents have chemopreventive properties. However, a limited number of these agents have been tested in clinical trials, with varying success. In this review, we have discussed the available clinical studies regarding the efficacy of natural chemopreventive agents against PCa, including tea polyphenols, selenium, soy proteins, vitamins and resveratrol. We have also provided a discussion on the clinical challenges and opportunities for the potential use of chemopreventive agents against PCa. Based on available literature, it appears that the variable outcomes of the chemopreventive clinical studies necessitate a need for additional studies with more rigorous designs and methodical interpretations in order to measure the potential of the natural agents against PCa.

Chemoprevention in African American Men With Prostate Cancer

BACKGROUND

Recommendations for cancer screening are uncertain for the early detection or prevention of prostate cancer in African American men. Thus, chemoprevention strategies are needed to specifically target African American men.

METHODS

The evidence was examined on the biological etiology of disparities in African Americans related to prostate cancer. Possible chemopreventive agents and biomarkers critical to prostate cancer in African American men were also studied.

RESULTS

High-grade prostatic intraepithelial neoplasia may be more prevalent in African American men, even after controlling for age, prostate-specific antigen (PSA) level, abnormal results on digital rectal examination, and prostate volume. Prostate cancer in African American men can lead to the overexpression of signaling receptors that may mediate increased proliferation, angiogenesis, and decreased apoptosis. Use of chemopreventive agents may be useful for select populations of men.

CONCLUSIONS

Green tea catechins are able to target multiple pathways to address the underlying biology of prostate carcinogenesis in African American men, so they may be ideal as a chemoprevention agent in these men diagnosed with high-grade prostatic intraepithelial neoplasia.

A Perspective on Prostate Carcinogenesis and Chemoprevention

In this perspective, modifiable carcinogenic factors for the prostate are summarized. This is followed by a discussion of how current knowledge about causation of prostate cancer and chemoprevention of prostate cancer can be used to develop preventive strategies. Prostate cancer is a slowly developing cancer which offers opportunities for preventive interventions. Only a few randomized clinical trials of prostate cancer prevention have been completed. The SELECT study with selenium and vitamin E did not find protective effects, but in two trials with 5α-reductase inhibitors risk was reduced about 25%, showing that chemoprevention is possible and indicating that the androgen receptor is a suitable target. Besides smoking cessation and reduction of obesity, there are no known dietary or life style interventions that will have a major impact on prostate cancer risk. Inflammation of the prostate is an attractive target and aspirin may be a promising candidate agent, but has not been addressed yet in preclinical and clinical studies. Antioxidants other than selenium and vitamin E are unlikely to be very effective and data on several dietary supplements are not encouraging. More candidate agents need to be identified and tested in relevant and adequate preclinical models and Phase II trials that have predictive value for outcome of Phase III randomized studies. Doing this will require a systematic approach comparing preclinical and clinical study outcomes to determine their predictive value of preventive efficacy.

Proceedings of the Indo-U.S. bilateral workshop on accelerating botanicals/biologics agent development research for cancer chemoprevention, treatment, and survival

With the evolving evidence of the promise of botanicals/biologics for cancer chemoprevention and treatment, an Indo-U.S. collaborative Workshop focusing on “Accelerating Botanicals Agent Development Research for Cancer Chemoprevention and Treatment” was conducted at the Moffitt Cancer Center, 29–31 May 2012. Funded by the Indo-U.S. Science and Technology Forum, a joint initiative of Governments of India and the United States of America and the Moffitt Cancer Center, the overall goals of this workshop were to enhance the knowledge (agents, molecular targets, biomarkers, approaches, target populations, regulatory standards, priorities, resources) of a multinational, multidisciplinary team of researcher's to systematically accelerate the design, to conduct a successful clinical trials to evaluate botanicals/biologics for cancer chemoprevention and treatment, and to achieve efficient translation of these discoveries into the standards for clinical practice that will ultimately impact cancer morbidity and mortality. Expert panelists were drawn from a diverse group of stakeholders, representing the leadership from the National Cancer Institute's Office of Cancer Complementary and Alternative Medicine (OCCAM), NCI Experimental Therapeutics (NExT), Food and Drug Administration, national scientific leadership from India, and a distinguished group of population, basic and clinical scientists from the two countries, including leaders in bioinformatics, social sciences, and biostatisticians. At the end of the workshop, we established four Indo-U.S. working research collaborative teams focused on identifying and prioritizing agents targeting four cancers that are of priority to both countries. Presented are some of the key proceedings and future goals discussed in the proceedings of this workshop.

Molecular Targeted Therapies Using Botanicals for Prostate Cancer Chemoprevention

In spite of the large number of botanicals demonstrating promise as potential cancer chemopreventive agents, most have failed to prove effectiveness in clinical trials. Critical requirements for moving botanical agents to recommendation for clinical use include adopting a systematic, molecular-target based approach and utilizing the same ethical and rigorous methods that are used to evaluate other pharmacological agents. Preliminary data on a mechanistic rationale for chemoprevention activity as observed from epidemiological, in vitro and preclinical studies, phase I data of safety in suitable cohorts, duration of intervention based on time to progression of pre-neoplastic disease to cancer and using a valid panel of biomarkers representing the hypothesized carcinogenesis pathway for measuring efficacy must inform the design of clinical trials. Botanicals have been shown to influence multiple biochemical and molecular cascades that inhibit mutagenesis, proliferation, induce apoptosis, suppress the formation and growth of human cancers, thus modulating several hallmarks of carcinogenesis. These agents appear promising in their potential to make a dramatic impact in cancer prevention and treatment, with a significantly superior safety profile than most agents evaluated to date. The goal of this paper is to provide models of translational research based on the current evidence of promising botanicals with a specific focus on targeted therapies for PCa chemoprevention.