The present data motivate studies designed to determine how IL-4 regulates FAAH in prostate cancer cells compared to lymphocytes, whether stromal IL-4 immunoreactivity (and/or expression of IL-4 receptors in the tumour epithelia) correlates with tumour epithelial FAAH-IR in prostate cancer tissue, and which other components of the tumour microenvironment are potential regulators of the endocannabinoid system. The gene discussed is IL4; the disease is neoplasm.