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 alpha (TNF-alpha; 10 ng/mL) without/with cycloheximide (CHX; 2.5 mu g/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-alpha+CHX (P < 0.05). Similarly, there was a higher incidence of FasL-induced apoptosis in CK18(-) HeLa cells (23% and 91% apoptotic for FasL and FasL+CHX, respectively) than CK18(+) HeLa cells (1% and 11%, respectively; P < 0.05). Surprisingly, TNF-alpha had no effect on either CK18(+) 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 < 0.05), an effect abrogated by the caspase 8 inhibitor IETD-fmk (P < 0.05). 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.
International Journal of Gynecological Cancer
LIPPINCOTT WILLIAMS & WILKINS
Digital Object Identifier (DOI)
Sullivan, B.T., Cherry, J.A., Sakamoto, H., Henkes, L.E., Townson, D.H, Rueda, B.R. 2010. Cytokeratin-18 (CK18) expression inhibits cytokine-induced death of cervical cancer cells. International Journal of Gynecologic Cancer 20:1474-1481
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