Epidemiological and prospective studies indicate that comprehensive lifestyle changes may modify the progression of prostate cancer. However, the molecular mechanisms by which improvements in diet and lifestyle might affect the prostate microenvironment are poorly understood. We conducted a pilot study to examine changes in prostate gene expression in a unique population of men with low-risk prostate cancer who declined immediate surgery, hormonal therapy, or radiation and participated in an intensive nutrition and lifestyle intervention while undergoing careful surveillance for tumor progression. Consistent with previous studies, significant improvements in weight, abdominal obesity, blood pressure, and lipid profile were observed (all P < 0.05), and surveillance of low-risk patients was safe. Gene expression profiles were obtained from 30 participants, pairing RNA samples from control prostate needle biopsy taken before intervention to RNA from the same patient's 3-month postintervention biopsy. Quantitative real-time PCR was used to validate array observations for selected transcripts. Two-class paired analysis of global gene expression using significance analysis of microarrays detected 48 up-regulated and 453 down-regulated transcripts after the intervention. Pathway analysis identified significant modulation of biological processes that have critical roles in tumorigenesis, including protein metabolism and modification, intracellular protein traffic, and protein phosphorylation (all P < 0.05). Intensive nutrition and lifestyle changes may modulate gene expression in the prostate. Understanding the prostate molecular response to comprehensive lifestyle changes may strengthen efforts to develop effective prevention and treatment. Larger clinical trials are warranted to confirm the results of this pilot study.exercise ͉ lifestyle changes ͉ prostate cancer ͉ SHOC2 ͉ stress management E pidemiological evidence (1, 2) and migrant studies (3) indicate that the incidence of clinically significant prostate cancer is much lower in parts of the world where people eat a predominantly low-fat, plant-based diet. We (4, 5) and others (6) have shown previously that diet and lifestyle interventions in men with earlystage prostate cancer decrease prostate-specific antigen (PSA) and decrease the rate of PSA increase. These studies provided some evidence that comprehensive lifestyle changes may have therapeutic potential in early prostate cancers. However, although these interventions are associated with decreased circulating insulin-like growth factor 1 (IGF1) (7), and although serum from men after intervention has reduced the ability to stimulate prostate cell-line growth in vitro (4), the actual molecular effects of these interventions in prostate tissue have not been previously examined.Many men with indolent prostate cancers detected by PSA screening will not exhibit disease progression during their lifetime; their treatment and associated side effects are unnecessary (8). We report here the results of the Gene Expressio...