(3) While much attention has been devoted to determining whether PPARs are friend or foe of tumors, our second question is also of fundamental significance: Is PPAR's role in tumor growth mediated by cell autonomous or by noncell autonomous mechanisms? From the perspective of PPAR investigators, this question may arise naturally because PPARs regulate intracellular processes, including proliferation, apoptosis, and differentiation as well as inflammatory processes through the control of mediators in cell-cell communication. The gene discussed is PPARA; the disease is neoplasm.