Elevated GRP78 mRNA and protein levels were previously observed upon PDT with various PSs, however, mostly in murine cancer cell lines and in vivo in a murine experimental model.8 To investigate whether PDT induces GRP78 expression in human cancer cells, GRP78 mRNA and protein levels were evaluated in two prostate cancer cell lines: DU-145 and PC-3, and in a lung cancer cell line SW-900. This evidence concerns the gene HSPA5 and prostate carcinoma.