Ovarian cancer ascites fluid contains matrix
proteins that can impact
tumor growth via
integrin receptor binding. In human ovarian
tumor tissue arrays, we find that activation of the cytoplasmic focal adhesion (FAK)
tyrosine kinase parallels increased
tumor stage, β5
integrin, and
osteopontin matrix staining. Elevated
osteopontin, β5
integrin, and FAK
mRNA levels are associated with decreased serous
ovarian cancer patient survival. FAK remains active within
ovarian cancer cells grown as spheroids, and anchorage-independent growth analyses of seven ovarian
carcinoma cell lines identified sensitive (HEY, OVCAR8) and resistant (SKOV3-IP, OVCAR10) cells to 0.1 μmol/L FAK inhibitor (VS-4718, formerly PND-1186) treatment.
VS-4718 promoted HEY and OVCAR8 G0-G1 cell-cycle arrest followed by cell death, whereas growth of SKOV3-IP and OVCAR10 cells was resistant to 1.0 μmol/L
VS-4718. In HEY cells, genetic or pharmacological FAK inhibition prevented
tumor growth in mice with corresponding reductions in β5
integrin and
osteopontin expression. β5 knockdown reduced HEY cell growth in soft
agar,
tumor growth in mice, and both FAK Y397 phosphorylation and
osteopontin expression in spheroids. FAK inhibitor-resistant (SKOV3-IP, OVCAR10) cells exhibited anchorage-independent Akt S473 phosphorylation, and expression of membrane-targeted and active Akt in sensitive cells (HEY, OVCAR8) increased growth but did not create a FAK inhibitor-resistant phenotype. These results link
osteopontin, β5
integrin, and FAK in promoting ovarian
tumor progression. β5
integrin expression may serve as a
biomarker for serous ovarian
carcinoma cells that possess active FAK signaling.