Abstract 141: MUC16/CA125 and Epithelial Growth Factor Receptor functionality in ovarian cancer
Authors: Wang Amy , Thapi Dharmarao , Rosales Nestor , Yan Xiu Jun , Spriggs David R. 
Published: August 2015

MUC16 encodes the CA125 antigen that is an established characteristic factor in epithelial human ovarian cancer. Yet its function remains largely unknown. The cloning of MUC16 has opened the door to additional functional exploration. MUC16 has a molecular size of over 14,000 amino acids and consists of a 31 amino acid cytoplasmic domain, a 25 amino acid transmembrane region, a 58 amino acid ectodomain and an external domain of up to 60 tandem repeats. As little as 114 AA of MUC16 will traffic to the membrane and induce an altered, more aggressive phenotype, and longer elements from the carboxyterminus with multiple CA125 antigenic tandem repeats were not substantially different. When either A2780 or SKOV3 or 3T3 cell lines had these short elements of the MUC16 gene carboxyterminus expressed, they had substantial increases in matrigel invasion and increased phosphorylation of AKT and ERK signaling. While MUC16 does not change in vitro growth. However, when placed in nu/nu mice, the MUC16 transformed tumors were more aggressive, with statistically significant more rapid tumor growth. Associated with these alterations in signal transduction are changes in gene expression including upregulation of fibronectin, IL-1β, MMP7, and MMP9.

EGF is a growth factor associated with ovarian cancer that is known to have interactions with epithelial growth factor receptor. In order to delineate the relationship of MUC16 and EGFrecepor, the current research work was undertaken to see the function of MUC16 and its effects on downstream signaling of AKT, ERK and SRC phosphorylation. Five different lentiviral plasmids that produce shEGFR targeting different DNA sequences were transfected into 293 cells. Subsequently, these cells secreted a lentivirus that contained shEGFR. Virus supernatant was used to infect SKOV3-MU16c114 cell line to create clonals SKOV3-MUC16c114-shEGFR cell lines. These cell lines were stably transfected and is selected with puromycin at 0.5 ug/ml.

Equal amounts of 24 hrs starved SKOV3 phrGFP (vector), MUC16c114, and MUC16c114-shEGFR cell line protein extracts were western blot analysed and equal amounts of EGFR were detected in phrGFP and MUC16c114 while EGFR was knocked out in the MUC16c114-shEGFR cell line. Increased amount of 4H11 (MUC16) mAbs was seen in the MUC16c114-shEGFR cell line compared to MUC16c114 and phrGFP vector control cell lines. The loss of EGFR expression was associated with decreased Matrigel invasion. Stability of EGFR was also examined. The introduction of MUC16c114 increased EGFR expression in each cell line tested. The relative stability of EGFR was increased by MUC16 expression as measured by EGFR persistence in the presence of cycloheximide.

We conclude the MUC16 may induce its aggressive phenotype through stabilization of EGFR on the cell surface.

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Citation Format: Amy Wang, Dharmarao Thapi, Nestor Rosales, Xiu Jun Yan, David R. Spriggs. MUC16/CA125 and Epithelial Growth Factor Receptor functionality in ovarian cancer. [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 141. doi:10.1158/1538-7445.AM2015-141