T-reg Function Changes: a Novel Immune Regulatory Effect Underlying Benefit of Statin Use on Lethal Prostate Cancer

Prior research has demonstrated a consistently strong inverse association between statin drug use and risk of developing lethal prostate cancer, and a stronger protective effect with a longer duration of use. Further, in men with clinically localized prostate cancer, statins are associated with a reduced risk of progression to metastasis and dying from prostate cancer. For statins to have clinical utility as chemo-preventive and therapeutic (adjuvant) agents, additional characterization of the mechanisms through which statins interact with the tumor microenvironment are needed. Statin drugs have been shown to inhibit Yes-associated protein (YAP) nuclear translocation and transcriptional activation (via YAP phosphorylation) required for T regulatory cell (T-reg) immunosuppressive function. YAP is a critical regulator of the immunosuppressive microenvironment contributing to T-reg differentiation and immunosuppressive function and antitumor T cell response.

Simvastatin is a moderate intensity statin regimen recommended for cholesterol reduction, and was previously shown to have a strong cytoplasmic YAP sequestration activity. This trial is designed to investigate the effect of 40 mg oral simvastatin daily on YAP-mediate T-reg disfunction and antitumor immune response. Eligible patients include men newly diagnosed with pathologically-confirmed localized prostate cancer determined to be intermediate (stage T2b, or Gleason 7 or PSA 10-20ng/mL) or high risk (stage T2c or PSA >/= 20 ng/mL, or Gleason >/= 8) of biochemical recurrence at the time of biopsy; not currently taking a statin who are scheduled for prostatectomy. For the trial, 52 patients will be randomized in a 1:1 ratio to the statin group or the control group. Randomization sequence will be computer generated using random blocks with concealed allocation of the random treatment assignment (e.g., statin or control) and will be stratified by race (Black vs non-Hispanic White) and BMI (<30 vs ≥30). Patients randomized to the statin group will receive moderate intensity simvastatin (40mg, day) for eight weeks until the date of prostatectomy. Patients randomized to the control group will not receive any intervention, this is not a placebo-controlled trial and participants, and investigators will not be masked. Patients in both groups will receive standard clinical laboratory assessments at baseline and at the end of the study after eight weeks to evaluated adherence based on the change in cholesterol and inflammation biomarkers from baseline to the end of follow-up at eight weeks. Multiplex immunofluorescence will be used to assess intra-prostatic YAP-mediate T-reg dysfunction (the number FOXP3+ T-regs with phosphorylated YAP), and intra-prostatic anti-tumor immune response (the count and density of CD4+ and CD8+ T cells) in whole tumor sections obtained from the tumor block containing the index tumor (i.e., largest and/or highest Gleason sum).