The mammalian target of rapamycin (mTOR), a protein in the phosphoinositide 3-kinase (PI3K) pathway important to cell cycle regulation, is frequently activated in cancer. This signaling pathway regulates cell growth and metabolism, and when dysregulated in cancer, it contributes to tumor angiogenesis and growth. mTOR contains two distinct complexes, MTORC1, and MTORC2. MTORC1 plays a role in biosynthesis, while MTORC2 helps with cellular metabolism. It has been shown that mTOR knockout models are embryonically lethal to mice. However, lower levels of functional mTOR have been shown to be beneficial and slow cancer progression. Allelic variation occurs within inbred strains of mice, including BALB/c mice. One allelic variant in mTOR, R628C, which contributes to tumor susceptibility has been identified in BALB/c mice. This single amino acid change occurs in the HEAT repeats of mTOR. HEAT repeats have been shown to facilitate binding partner interactions, dimerization, and localization. Studies on mutations found within the HEAT repeats in several proteins have altered protein function and emphasize the structural importance of HEAT repeats. The goal of this study is to further elucidate the functional significance of HEAT repeats in TOR function and how allelic variation in the HEAT repeats may contribute to tumor susceptibility. Characterization of this allelic variant has shown stress inputs, such as irradiation, lead to a more severe phenotype and reduced mTORC1/2 signaling. Subsequent in vitro studies using a tetracycline inducible expression system (T-RExTM) have shown differential binding to mTORC1/2 complex partners in cells expressing the Balb/c allele. Additional studies are being performed to assess other complex binding partners, dimerization state and localization of the allelic variant. Our findings will model mTOR signaling activation mechanisms in humans to aid in development of new cancer treatments.

Note: This abstract was not presented at the meeting.

Citation Format: Patricia A. Wiley, Joy Gary, Zaw Phyo, Shuling Zhang, Amanda Sciorillo, Dorian Fraizer. Phenotypic characterization of allelic variation within the HEAT repeats of the mechanistic target of rapamycin [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 3410. doi:10.1158/1538-7445.AM2017-3410