Characterization of Cellular FLICE Inhibitory Protein (c-FLIP) in Cells of Human Cervical Cancer

The protein cFLIP is suspected to protect cells against programmed cell death (apoptosis) in cervical cancer carcinoma, and thus provide a mechanism to promote metastasis. Increased cFLIP expression would be anticipated in cervical caner cells resistant to apoptosis compared to those that are vulnerable. The objective of this study was to determine the relative expression of cFLIP in a cervical cancer cell line (HeLa cells ) known to contain cells both resistant and vulnerable to apoptosis, depending upon whether or not the cells express cytokeratin filaments. The HeLa cells that express (K+) or lack (K-) cytokeratin filaments were cultures and then exposed to culture medium alone (control), cyclohexamide (a protein synthesis inhibitor), and/or Fas antibody (to induce apoptosis). A cell death assay confirmed K+ cells are more resistant to apoptosis than K- cells. The cells were subsequently lysed to separate cellular proteins using SDS-polyacrylamide gel electrophoresis (SDSPAGE). SDS-PAGE followed by immunoblot analysis revealed no differences in cFLIP expression (relative to β- actin) between K+ and K- HeLa cells under control culture conditions. However, further experiments in which the cells were exposed to cyclohexamide and/or Fas agonist indicated cFLIP increased in K- cells, regardless of treatment. Additional experiments are underway to resolve these discrepancies, including a test of whether cFLIP might associate with keratin filaments to influence the abundance of immunodetectable cFLIP