Ceramide promotes the death of human cervical tumor cells in the absence of biochemical and morphological markers of apoptosis

C8-ceramide a synthetic cell-permeable analog of endogenous ceramides interfered with cell proliferation and was cytotoxic to papiloma virus-containing human cervix carcinoma cells CALO INBL and HeLa that match two clinical stages of tumor progression. C8-ceramide (3μM) markedly reduced the tumor cell number after 48 h of treatment an effect that endured even after the removal of C8-ceramide. The carcinoma cells showed morphologic changes characteristic of necrosis and released lactate dehydrogenase (LDH). A biologically inactive analog C8-dihydro-ceramide had no effect on cell viability in any of the cell lines tested. Seventy-two hours after C8-ceramide treatment none of the biochemical and morphological markers characteristic of apoptosis: (a) nuclear chromatin condensation (b) DNA fragmentation (c) proteolysis of the caspase-3 substrate poly-(ADP-ribose)-polymerase (PARP) and (d) appearance of phosphatidylserine on the external cell membrane were observed. C8-ceramide had no effect on human cervix fibroblasts and induced a mild reduction (30%) in the proliferation of normal human cervix epithelia and HeLa cells (IV-B metastasic stage). The cytotoxicity of C8-ceramide was restricted to CALO (early II-B) and INBL (IV-A non-metastasic) carcinoma cells. The possible application of ceramide in the treatment of early stages of cervical cancer is discussed.