PRF1 and neoplasm: When cytotoxic and apoptotic markers were examined in BRAF and PK5L1940 cell-derived allograft tumors by real-time PCR, an increase of Gzmb and Prf1 (from 5-fold to up to 15-fold) expression in animals treated with Th2 cells compared to control animals was found, indicating an increase in tumor lytic factors (Fig. 4a).