It is suggested that Th2-polarized cytokines secreted by splenic T cells in the PC-3 tumor microenvironment may increase Fas mRNA expression levels in the corresponding treated PC-3 cells, possibly subsequently causing PC-3 cells’ apoptosis induced by Fas ligand (FasL)-bearing cells such as CD8+ T cells. The gene discussed is FAS; the disease is pachyonychia congenita.