// Joe R. Delaney 1 , Chandni Patel 1 , Katelyn E. McCabe 1 , Dan Lu 1 , Mitzie-Ann Davis 1 , Isabelle Tancioni 1 , Tami von Schalscha 1 , Alena Bartakova 1 , Carley Haft 1 , David D. Schlaepfer 1 , Dwayne G. Stupack 1 1 Department of Reproductive Medicine, UCSD Moores Cancer Center, La Jolla, CA, USA Correspondence to: Dwayne G. Stupack, e-mail: dstupack@ucsd.edu Keywords: ovarian cancer, autophagy, combination therapy, adverse events, necramed Received: June 16, 2015 Accepted: September 10, 2015 Published: September 22, 2015 ABSTRACT Serous Ovarian Cancers (SOC) are frequently resistant to programmed cell death. However, here we describe that these programmed death-resistant cells are nonetheless sensitive to agents that modulate autophagy. Cytotoxicity is not dependent upon apoptosis, necroptosis, or autophagy resolution. A screen of NCBI yielded more than one dozen FDA-approved agents displaying perturbed autophagy in ovarian cancer. The effects were maximized via combinatorial use of the agents that impinged upon distinct points of autophagy regulation. Autophagosome formation correlated with efficacy in vitro and the most cytotoxic two agents gave similar effects to a pentadrug combination that impinged upon five distinct modulators of autophagy. However, in a complex in vivo SOC system, the pentadrug combination outperformed the best two, leaving trace or no disease and with no evidence of systemic toxicity. Targeting the autophagy pathway in a multi-modal fashion might therefore offer a clinical option for treating recalcitrant SOC.
Abstract Introduction Focal adhesion kinase (FAK) controls cell growth and survival downstream of integrin-matrix receptors. Upon adhesion loss or FAK inhibition, FAK can translocate to the nucleus. The nucleolus is a non-membrane nuclear structure that regulates ribosome biogenesis and cell proliferation. Nucleostemin (NS), a nucleolar-localized protein, modulates cell cycle progression, stemness, and three-dimensional tumor spheroid formation. The signaling pathways that regulate NS levels in tumors remain undefined. Methods Human breast carcinoma cells were evaluated for growth in culture (adherent and anchorage-independent spheroid) and as orthotopic tumors. FAK signaling was evaluated by pharmacological FAK inhibitor addition (PF-271, IC50 ~ 0.1 μM) and by small hairpin RNA (shRNA) knockdown followed by re-expression of FAK wildtype (WT) or a kinase-dead (KD, K454R) FAK point mutant. Immunoblotting was used to evaluate FAK, NS, nucleolar phosphoprotein B23, and nucleolin levels. Total and phosphospecific antibody imunoblotting were used to detect changes in FAK, Akt kinase (Akt also known as protein kinase B), and 4E-binding protein 1 (4E-BP1) phosphorylation, a translation repressor protein and target of the mammalian target of rapamycin (mTOR) complex. Immunohistochemical, co-immunoprecipitation, and cellular fractionation analyses were used to evaluate FAK association with nucleoli. Results Pharmacological (0.1 μM PF-271) or genetic inhibition of FAK activity prevents MDA-MB-231 and 4T1L breast carcinoma growth as spheroids and as orthotopic tumors. FAK inhibition triggers proteasome-mediated decreased NS levels but no changes in other nucleolar proteins such as B23 (nucleophosmin) or nucleolin. Active FAK was associated with purified nucleoli of anchorage-independent cells and present within nucleoli of human invasive ductal carcinoma tumor samples. FAK co-immunoprecipitated with B23 that binds NS and a complex between FAK, NS, Akt, and mTOR was detected. Constitutively-active Akt kinase promoted tumor spheroid growth, stabilized NS levels, and promoted pS65 4E-BP1 phosphorylation in the presence of inhibited FAK. Rapamycin lowered NS levels and inhibited pS65 4E-BP1 phosphorylation in cells with activated Akt-mTOR signaling. Conclusions FAK signaling occurs in the nucleolus, active FAK protects NS, and Akt-mTOR pathway regulates NS protein stability needed for breast carcinoma spheroid and tumor growth.
Abstract Rho GTPase regulatory and integrin signaling pathways are associated with poor high-grade serous ovarian carcinoma (HGSOC) patient survival1. Focal adhesion kinase (FAK) transmits signals from integrins and promotes HGSOC tumor progression through mechanisms involving tumor-stromal cell interactions2. We previously found that the Rho guanine nucleotide exchange factor Rgnef (also named p190RhoGEF or Arhgef28) activates FAK as well as RhoA GTPase activity in mouse fibroblasts3. Here we find that Rgnef protein expression is elevated in Stage 3-4 HGSOC and that Rgnef knockout prevents spontaneous ovarian tumor formation in the MISIIR-T-antigen (TAg) induced C57BL/6 mouse model. At 17 weeks, Rgnef-/-;TAg ovarian tumors were significantly smaller (p<0.001) than Rgnef+/+;TAg controls. Primary Rgnef-/-;TAg and Rgnef+/+;TAg tumor cells were isolated and expanded ex vivo. Although loss of Rgnef did not alter growth as 3D spheroids, Rgnef-/-;TAg orthotopic (ovarian bursa) and intraperitoneal tumors were significantly smaller (p<0.01) than Rgnef+/+;TAg tumors in MISIIR-TAg-Low C57BL/6 syngeneic mice. Notably, FAK activation (as measured by FAK Y397 phosphorylation) was decreased in Rgnef-/-;TAg ascites-associated tumor cells. Together, these studies show that Rgnef loss impedes tumor growth independently of stromal Rgnef status and supports the notion that an Rgnef-FAK signaling linkage facilitates ovarian tumor initiation and progression. 1.Zhang, H., et al. Integrated Proteogenomic Characterization of Human High-Grade Serous Ovarian Cancer. Cell 166 (2016). 2.Sulzmaier, F.J., Jean, C. & Schlaepfer, D.D. FAK in cancer: mechanistic findings and clinical applications. Nat. Rev. Cancer 14, 598-610 (2014). 3.Miller, N.L., et al. A non-canonical role for Rgnef in promoting integrin-stimulated focal adhesion kinase activation. J. Cell Sci. 126, 5074-5085 (2013). Citation Format: Elizabeth G. Kleinschmidt, Nichol L.G. Miller, Isabelle Tancioni, Denise C. Connolly, David D. Schlaepfer. TARGETING RGNEF (P190RHOGEF/ARHGEF28) IMPAIRS OVARIAN TUMOR INITIATION AND PROGRESSION [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr TMEM-027.
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.
Abstract Identification of specific oncogenic gene changes has enabled the modern generation of targeted cancer therapeutics. In high-grade serous ovarian cancer (OV), the bulk of genetic changes is not somatic point mutations, but rather somatic copy-number alterations (SCNAs). The impact of SCNAs on tumour biology remains poorly understood. Here we build haploinsufficiency network analyses to identify which SCNA patterns are most disruptive in OV. Of all KEGG pathways ( N =187), autophagy is the most significantly disrupted by coincident gene deletions. Compared with 20 other cancer types, OV is most severely disrupted in autophagy and in compensatory proteostasis pathways. Network analysis prioritizes MAP1LC3B ( LC3 ) and BECN1 as most impactful. Knockdown of LC3 and BECN1 expression confers sensitivity to cells undergoing autophagic stress independent of platinum resistance status. The results support the use of pathway network tools to evaluate how the copy-number landscape of a tumour may guide therapy.
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