Abstract 2273: Mechanistic and functional implications of FABP4 in ovarian cancer metastasis

Abstract

Abstract Purpose:The purpose of this study was to identify molecular predictors of residual disease (RD) in high grade serous ovarian cancer (HGSC) and further understand their role in promoting cancer metastasis. Method:The current study analyzed Affymetrix gene expression data of 504 HGSC cases from The Cancer Genome Atlas (TCGA) data to identify differentially expressed genes in tumors from patients with no gross residual disease after surgery (NRD) or presence of RD following initial debulking surgery. It was followed by qRT-PCR analysis of tumor samples for validation purposes. RPPA data of 354 patients from TCGA were analyzed. Immunohistochemical analysis was performed on the patient samples to determine the expression at the protein level (cancer versus stromal cells). Gene array was carried out after overexpressing the selected gene in ovarian cancer cells and the data was analyzed by Ingenuity Pathway Analysis (IPA). In vitro (migration and invasion) and in vivo (orthotopic mouse models) assays were used to determine the biological roles of gene(s) identified from the above analyses. Results: In TCGA data set, 97/107 (90.6%) of the patients with high expression of FABP4 gene had residual disease. In the validation cohort, among the 35 patients predicted to be at high risk for residual disease, 30 (86%) did have residual disease. In contrast, only 54 of the 104 patients with FABP4 values below the decision threshold (52%) had incomplete resection (p = 0.0002). RPPA analysis indicated that expression of FABP4 was positively correlated (Spearman correlation analysis) with expression of several other proteins known to increase tumor cell infiltration and metastasis such as JNK2 (p = 0.194), transglutaminase (p = 0.199), c-kit (p = 0.173), fibronectin (p = 0.364), PKC-A (p = 0.178), collagen-6 (p = 0.197) and paxillin (p = 0.239). It was negatively correlated with E-cadherin (p = -0.246) and claudin-7 (p = -0.201) expression. Immunohistochemical analysis confirmed that apart from endothelial cells and adipocytes, cancer cells also express significant amount of FABP4. In vitro assays showed significant reduction in invasion and migration after silencing FABP4 in HGSC cell lines (p<0.0001). On the other hand, overexpression of FABP4 led to increased invasion and migration (p<0.01). In vivo stable overexpression of FABP4 increased the tumor weight by 3.5 fold (p<0.05). It also increased the number of nodules by 2.5 fold (p<0.05). Overexpression also led to increase in metastasis sites including liver, spleen, diaphragm and omentum, while the tumor in the control group was confined to ovary and peritoneal cavity. Histological analysis of tumor tissues showed infiltrative phenotype after overexpression of FABP4. Conclusion:These findings provide a new understanding of ovarian cancer metastasis and identify a potentially important target for therapeutic intervention. Citation Format: Kshipra M. Gharpure, Susan L. Tucker, Shelley M. Herbrich, Anna K. Unruh, Alpa M. Nick, Erin K. Crane, Robert L. Coleman, Jamie Guenthoer, Heather J. Dalton, Sherry Y. Wu, Rajesha Rupaimoole, Gabriel Lopez-Berestein, Bulent Ozpolat, Cristina Ivan, Wei Hu, Keith Baggerly, Anil Sood. Mechanistic and functional implications of FABP4 in ovarian cancer metastasis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2273. doi:10.1158/1538-7445.AM2015-2273