Abstract 184: The role of matrix metalloproteinases (MMPs) and CTNNB1 mutations in endometrial carcinoma
Authors: Berger Amnon A. , Levine Douglas A. , Kawaler Emily 
Published: August 2019

Abstract
Introduction: Advanced endometrial carcinoma (EC) carries a poor prognosis, especially for tumors with CTNNB1 somatic mutations. GOG-86P recently demonstrated that treatment of CTNNB1-mutated tumors with the anti-VEGFA antibody bevacizumab (bev) resulted in a better outcome, however, the mechanism for this response is unknown. We tested the hypothesis that overexpression of MMP proteins increases angiogenesis through VEGFA downstream signaling leading to improved clinical response in CTNNB1-mutated tumors.
Methods: Data from the endometrial TCGA and CPTAC projects were used to examine the relationship between exon 3 CTNNB1 mutations and VEGFA expression. We used 3 EC cell lines with wildtype (WT) CTNNB1, Ishikawa, HEC59 and JHUEM7, and a single EC cell line with a mutated CTNNB1, HEC108. We compared our results to a colorectal cancer (CRC) model by using the WT cell line RKO and mutated cell line HCT116. We measured VEGFA, CTNNB1, MMP2, MMP7, MMP9 RNA and protein levels in these cell lines using RT-PCR, western blots and ELISA. We transiently and stably overexpressed CTNNB1 in WT CRC and EC cell lines and downregulated CTNNB1 using shRNA transduction in mutated cell lines.
Results: An analysis of TCGA microsatellite stable, TP53-wildtype, endometrioid EC showed a 1.4-fold increase in VEGFA gene expression in tumors with CTNNB1 mutations compared to those without (P=0.01). CPTAC endometrial cancer proteomic data did not identify greater VEGFA protein expression in CTNNB1-mutated tumors. An analysis of known β-catenin targets in TCGA and CPTAC revealed significantly increased MMP7 and MMP9 gene and protein expression in CTNNB1-mutated tumors. Transient overexpression of CTNNB1 in WT EC and CRC cell lines increased VEGFA gene expression of 2-3 fold. Stable overexpression of physiologic levels of mutated CTNNB1 in WT EC and CRC lines resulted in significantly increased VEGFA and MMP7 gene expression and increased levels of secreted MMP7. Knockdown of CTNNB1 induced a significant decrease in VEGFA gene expression in HCT116, but not HEC108. MMP7 gene expression was paradoxically increased in CTNNB1-knockdown HCT116, but decreased in CTNNB1-knockdown HEC108.
Conclusions: We have shown in silico and in vitro that CTNNB1 exon 3 mutations are associated with increased VEGFA and MMP7 expression. Knockdown experiments in mutated tumors in EC and CRC models suggest that control of angiogenesis and mechanism of action for bev may vary between tumor types supporting the role of CTNNB1 mutations as a biomarker in EC. Ongoing experiments will study the role of MMP7 in CTNNB1-mutated tumors. These findings are being translated into biomarker stratified clinical trials and individualized treatment for women with advanced EC.
Citation Format: Amnon A. Berger, Douglas A. Levine, Emily Kawaler. The role of matrix metalloproteinases (MMPs) and CTNNB1 mutations in endometrial carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 184.