Abstract 1839: TGFBR1*6A mouse model mimics human breast cancer development and progression

Abstract

Abstract Transforming Growth Factor-ß (TGF-β) is one of the most commonly altered cellular signaling pathways in human cancer. Our group was the first to discover TGFBR1*6A (*6A), a common hypomorphic variant of the type I TGF-ß receptor (TGFBR1), which has been associated with increased risk for breast cancer in multiple epidemiological studies. Functional analysis also suggests that *6A is associated with decreased tumor suppressive TGF-β signaling in early tumor development and is involved with promoting tumorigenesis in advanced carcinomas. To better understand the functional impact of *6A and constitutively reduced TGF-ß signaling on breast cancer development and progression, we have recently developed a series of transgenic knock-in mouse model variants by replacing exon 1 of the mouse Tgfbr1 sequence with human exon 1 sequences harboring both *6A and wild-type (*9A) TGFBR1 variants and crossed them with MMTVneu mice. We generated a total of 5 FVB double and/or triple transgenic mouse strains: MMTVneu;9A/9A, MMTVneu;6A/6A, MMTVneu;9A/6A, MMTVneu;*9A/-, and MMTVneu;6A/-. Following tumor development, measurements were performed three times per week to determine tumor volume. All mice were allowed to live up to 18 months (548 days) or until they died of natural causes. Specimens were collected for later analysis of blood, tumors, normal mammary tissue, and were evaluated for lung metastases. Statistical comparisons performed using Student’s t-test. Only 34.4% of MMTVneu;9A/9A mice (11/32) developed mammary tumors, while 80% of MMTVneu;6A/6A mice (24/30; p=0.0002) and 62.5% of MMTVneu;6A/- mice (19/32, p=0.046) developed tumors. The percentage of MMTVneu;9A/6A and MMTVneu;*9A/- mice that developed tumors was higher than MMTVneu;9A/9A mice (48.3% and 50%, respectively) but was not statistically significant. Additionally, 66.7% of MMTVneu;6A/6A mice (20/30) developed 2 or more tumors, while only 25% of MMTVneu;9A/9A mice (8/32) developed multiple tumors (p=0.0007). Our data suggests that we have developed transgenic mouse strains that accurately mimic human breast cancer susceptibility associated with *6A and constitutively decreased TGFBR1 expression in humans, as evidenced by other studies. These mouse models may be a tool to provide invaluable insight to better understand the role of TGFBR1 variants in the development and progression of breast cancer. Citation Format: Michael James Pennison, Minghui Wang, Hugo Jimenez, Boris Pasche. TGFBR1*6A mouse model mimics human breast cancer development and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1839. doi:10.1158/1538-7445.AM2017-1839