Abstract Ovarian cancer spreads via cell shedding and growth within malignant ascites. Effective targeted therapies have not been developed for ovarian cancer. Ascites contains an abundance of matrix proteins, and spheroids maintain integrin receptor expression. Through databases analyses we find that elevated osteopontin (OPN), β5 integrin, and focal adhesion kinase (FAK) mRNA levels are associated with decreased overall survival of serous ovarian cancer patients treated with platinum and taxol. In ovarian tumor tissue arrays, increased FAK activation (FAK Y397 phosphorylation) correlated with elevated tumor grade in parallel with increased in β5 integin and OPN levels. FAK is a cytoplasmic tyrosine kinase that remains active in spheroids, and treatment of seven ovarian carcinoma cell lines with sub-micromolar levels of FAK inhibitor (PND-1186) identified sensitive (HEY and OVCAR8), intermediate (OVCAR3, ID8-IP, and IGROV1-IP), and resistant (SKOV3-IP and OVCAR10) cells to blockage of growth under anchorage-independent conditions. Genetic or pharmacological FAK inhibition within ID8-IP or HEY cells selectively prevents anchorage-independent growth in culture and tumor growth in mice with corresponding reductions in β5 integrin and OPN expression. β5 knockdown reduced HEY growth in soft agar, tumor growth in mice, FAK Y397 phosphorylation, and OPN expression in spheroids. Although FAK inhibitor resistant ovarian carcinoma cells (SKOV3-IP and OVCAR10) were associated with anchorage-independent Akt S473 phosphorylation, membrane-targeted and activated Akt expression in sensitive cells (HEY and OVCAR8) resulted in only a partial rescue of FAK inhibitor-associated growth block. These results support the hypothesis that OPN, αvβ5 integrins, and FAK may function as a signaling axis promoting ovarian tumor progression. Although Akt signaling pathway activation is a common event in serous ovarian cancer, our results suggest that this may not impart complete resistance to FAK inhibitor treatment. Supported by NIH CA102310 Citation Format: Isabelle Tancioni, Sean Uryu, Florian Sulzmaier, Nina Shah, Christine Lawson, Nichol L.G. Miller, Christine Jean, Xiao Lei Chen, Kristy K. Ward, David D. Schlaepfer. Genetic and pharmacological FAK inhibition disrupt a β5 integrin signaling axis controlling anchorage-independent ovarian carcinoma growth. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 752. doi:10.1158/1538-7445.AM2014-752
Gene copy number alterations, tumor cell stemness, and the development of platinum chemotherapy resistance contribute to high-grade serous ovarian cancer (HGSOC) recurrence. Stem phenotypes involving Wnt-β-catenin, aldehyde dehydrogenase activities, intrinsic platinum resistance, and tumorsphere formation are here associated with spontaneous gains in Kras, Myc and FAK (KMF) genes in a new aggressive murine model of ovarian cancer. Adhesion-independent FAK signaling sustained KMF and human tumorsphere proliferation as well as resistance to cisplatin cytotoxicity. Platinum-resistant tumorspheres can acquire a dependence on FAK for growth. Accordingly, increased FAK tyrosine phosphorylation was observed within HGSOC patient tumors surviving neo-adjuvant chemotherapy. Combining a FAK inhibitor with platinum overcame chemoresistance and triggered cell apoptosis. FAK transcriptomic analyses across knockout and reconstituted cells identified 135 targets, elevated in HGSOC, that were regulated by FAK activity and β-catenin including Myc, pluripotency and DNA repair genes. These studies reveal an oncogenic FAK signaling role supporting chemoresistance.
Abstract Ovarian cancer is a leading cause of cancer death in women, is usually diagnosed in late stage, and currently has insufficient effective targeted therapies. The primary mode of metastasis is unique in that dissemination occurs via tumor cell shedding into the peritoneal cavity, survival and growth within ascites, and re-adhesion and proliferation of tumor cells at sites within the abdomen. Therefore, molecules and pathways involving cell adhesion and survival in non-adherent environments are of particular interest. Rgnef (p190RhoGEF/Arhgef28) is a Rho family guanine exchange factor that associates with focal adhesion kinase (FAK) and functions both as a downstream target of FAK tyrosine kinase activity and a regulator of FAK activity following integrin stimulation. FAK regulates cell adhesion, migration, and survival. Expression of FAK is associated with poor clinical outcome, its activity (as measured by FAK Y397 phosphorylation) is frequently increased in serous ovarian carcinomas, and it is currently under investigation as a therapeutic target in ongoing clinical trials. Immunohistochemical analysis of human tumor tissue arrays with antibodies specific for Rgnef and FAK pY397 reveal a positive correlation between Rgnef expression and FAK activation and increased stage/grade of serous-type ovarian cancer. Stable knockdown of Rgnef in human ovarian carcinoma cells grown as subcutaneous or intraperitoneal xenografts in mice suggest that Rgnef may play roles in both primary tumor growth and ascites-associated cell survival and spread. Here, we use a transgenic model of spontaneous ovarian cancer (MISIIR-T-Antigen) to test the role of Rgnef in ovarian cancer progression. Female Rgnef+/+;TAg+ and Rgnef-/-;TAg+ mice were monitored by ultrasound imaging from age 12 to 17 weeks before euthanasia. Rgnef-/-;TAg+ tumors were significantly smaller (p=0.0006) and contained fewer Ki67 positive cells than Rgnef+/+;TAg+ controls at 17 weeks. Tumors and ovarian carcinoma cells isolated from Rgnef-/-;TAg+ mouse ascites have reduced FAK pY397 and increased E-cadherin expression compared to controls, suggesting that loss of Rgnef results in a less aggressive tumor phenotype. These findings identify Rgnef as a component in signaling pathways promoting FAK activation and regulating ovarian tumor progression. Citation Format: Nichol L. G. Miller, Isabelle Tancioni, Sean Uryu, Elizabeth G. Kleinschmidt, Denise C. Connolly, David D. Schlaepfer. An Rgnef (p190RhoGEF/Arhgef28) signaling axis regulates ovarian cancer progression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3157. doi:10.1158/1538-7445.AM2014-3157
Rgnef (p190RhoGEF/Arhgef28) is a Rho guanine-nucleotide exchange factor (GEF) that binds focal adhesion kinase (FAK). FAK is recruited to adhesions and activated by integrin receptors binding to matrix proteins, such as fibronectin (FN). Canonical models place Rgnef downstream of integrin-FAK signaling in regulating Rho-GTPase activity and cell movement. Herein, we establish a new, upstream role for Rgnef in enhancing FAK localization to early peripheral adhesions and promoting FAK activation upon FN binding. Rgnef−/− mouse embryo fibroblasts (MEFs) exhibit defects in adhesion formation, levels of FAK phosphotyrosine (pY)-397 and FAK localization to peripheral adhesions upon FN replating. Rgnef re-expression rescues these defects, but requires Rgnef-FAK binding. Rgnef pleckstrin-homology (PH) domain mutation inhibits adhesion formation, FAK localization, FAK-pY397 and paxillin-pY118 without disrupting Rgnef-FAK interaction. A GEF-inactive Rgnef mutant rescues FAK-pY397 and early adhesion localization, but not paxillin-pY118. This suggests that downstream of FN-binding, paxillin-pY118 requires Rgnef GEF activity through a mechanism distinct from adhesion formation and FAK activation. These results support a scaffolding role for Rgnef in FAK localization and activation at early adhesions in a PH domain-dependent but GEF activity-independent manner.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
