Cytokeratin 18 expression inhibits cytokine-induced death of cervical cancer cells.

Objectives: In cervical cancer, increased cytokeratin 18 (CK18) filament expression is associated with disease progression. However, it may also provide resistance to cytokine-induced apoptosis. The present study tested whether CK18 expression influences susceptibility to cytokine-induced apoptosis. Methods: The cervical cancer cell lines C-4II (high CK18 expression), ME-180 (low CK18 expression), and 2 subtypes of HeLa cells containing or lacking CK18 expression (CK18 + and CK18 − cells, respectively) were exposed to vehicle (control), Fas ligand (FasL) (50 ng/mL), or tumor necrosis factor α (TNF-α; 10 ng/mL) without/with cycloheximide (CHX; 2.5 μg/mL) to test the hypothesis that diminished CK18 expression increases susceptibility to cytokine-induced apoptosis. Results: Flow cytometric analysis of cell death via TUNEL staining revealed that cytokine-induced apoptosis was 2-fold greater in ME-180 cells than C-4II cells in response to FasL+CHX or TNF-α+CHX ( P − HeLa cells (23% and 91% apoptotic for FasL and FasL+CHX, respectively) than CK18 + HeLa cells (1% and 11%, respectively; P + or CK18 − HeLa cells ( P > 0.05). Caspase 3 activity was greater in CK18 − HeLa cells than in CK18 + HeLa cells at 8 and 18 hours after FasL treatment ( P P Conclusions: Cervical cancer cells with diminished CK18 expression are more susceptible to cytokine-induced apoptosis, particularly in response to FasL treatment. These observations suggest that relative CK18 expression is an important factor when considering therapeutic strategies to enhance immune cell-mediated death of cervical cancer cells.