Caspase 3-mediated focal adhesion kinase processing in human ovarian cancer cells: possible regulation by X-linked inhibitor of apoptosis protein.
OBJECTIVE
Cell adhesion is an important cell survival determinant and disruption of integrin-mediated signal transduction may be involved in anchorage-dependent cell death. We have examined the processing of focal adhesion kinase (FAK), a component of integrin-mediated signal transduction, in a cisplatin-sensitive human ovarian epithelial cancer cell line (OV2008), to test the possible role of FAK degradation in the control of apoptosis via regulation of cell attachment.


METHODS
FAK processing after cisplatin treatment in the absence or presence of various caspase-inhibiting substances was analyzed by Western blot. Caspase-inhibiting activities were introduced using cell-permeable peptides or adenoviral vector.


RESULTS
Cisplatin-induced caspase 3 and FAK cleavage, cell detachment from the growth surface, and apoptosis in a temporally related and concentration-dependent manner. FAK fragments were detected exclusively in cells detached from the culture surface. Addition of active caspase 3 to the whole cell lysate elicited a similar pattern of FAK cleavage. Pretreatment of whole cell lysates and cells with tetrapeptide inhibitors of caspases significantly decreased FAK cleavage induced by exogenous active caspase 3 and cisplatin, respectively. Overexpression of X-linked inhibitor of apoptosis protein (Xiap), an endogenous caspase inhibitor, attenuated the cisplatin-induced FAK processing, morphologic changes, and apoptosis. The inhibitory action of Xiap was abolished with the deletion of a functional motif required for caspase inhibition.


CONCLUSIONS
These findings are consistent with our hypothesis that FAK processing is in part mediated by caspase 3, the activation of which is modulated by Xiap.
Sasaki
Hiromasa
H
Reproductive Biology Unit, Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, Ontario, Canada K1Y 4E9.
Kotsuji
Fumikazu
F
Tsang
Benjamin K
BK
D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D002945:Cisplatin / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D007150:Immunohistochemistry; D009360:Neoplastic Cells, Circulating; D010051:Ovarian Neoplasms / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D014176:Protein Biosynthesis; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D051636:X-Linked Inhibitor of Apoptosis Protein
D000970:Antineoplastic Agents; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D011506:Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D002945:Cisplatin