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Rheb1-Independent Activation of mTORC1 in Mammary Tumors Occurs through Activating Mutations in mTOR.

Cell reports (2020-04-30)
Bin Xiao, Dongmei Zuo, Alison Hirukawa, Robert D Cardiff, Richard Lamb, Nahum Sonenberg, William J Muller
ABSTRACT

Mechanistic target of rapamycin complex 1 (mTORC1) is a master modulator of cellular growth, and its aberrant regulation is recurrently documented within breast cancer. While the small GTPase Rheb1 is the canonical activator of mTORC1, Rheb1-independent mechanisms of mTORC1 activation have also been reported but have not been fully understood. Employing multiple transgenic mouse models of breast cancer, we report that ablation of Rheb1 significantly impedes mammary tumorigenesis. In the absence of Rheb1, a block in tumor initiation can be overcome by multiple independent mutations in Mtor to allow Rheb1-independent reactivation of mTORC1. We further demonstrate that the mTOR kinase is indispensable for tumor initiation as the genetic ablation of mTOR abolishes mammary tumorigenesis. Collectively, our findings demonstrate that mTORC1 activation is indispensable for mammary tumor initiation and that tumors acquire alternative mechanisms of mTORC1 activation.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Monoclonal Anti-β-Actin antibody produced in mouse, clone AC-74, ascites fluid
Sigma-Aldrich
Anti-Puromycin Antibody, clone 12D10, clone 12D10, from mouse
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Crystal violet solution