Cytokeratin 18 expression inhibits cytokine-induced death of cervical cancer cells.
OBJECTIVE
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 < 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-α 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.
Vincent Center for Reproductive Biology, MGH/Department of Vincent Obstetrics and Gynecology, Massachusetts General Hospital, Boston, MA 02114, USA.
Brian T
BT
Sullivan
Jessica A
JA
Cherry
Hideo
H
Sakamoto
Luiz E
LE
Henkes
David H
DH
Townson
Bo R
BR
Rueda
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D016207:Cytokines / Q000008:administration & dosage / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D004353:Drug Evaluation, Preclinical; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D053222:Fas Ligand Protein / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D006367:HeLa Cells; D006801:Humans; D053538:Keratin-18 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*
D016207:Cytokines; D053222:Fas Ligand Protein; D053538:Keratin-18; D034741:RNA, Small Interfering; D053148:Caspase 3