American Association for Cancer Research
00085472can181220-sup-200590_3_supp_5296205_plr757.pptx (61.8 kB)

Supplementary Figure S3 from 4E-BP1 Is a Tumor Suppressor Protein Reactivated by mTOR Inhibition in Head and Neck Cancer

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posted on 2023-03-31, 03:01 authored by Zhiyong Wang, Xiaodong Feng, Alfredo A. Molinolo, Daniel Martin, Lynn Vitale-Cross, Nijiro Nohata, Mizuo Ando, Amy Wahba, Panomwat Amornphimoltham, Xingyu Wu, Mara Gilardi, Michael Allevato, Victoria Wu, Dana J. Steffen, Philip Tofilon, Nahum Sonenberg, Joseph Califano, Qianming Chen, Scott M. Lippman, J. Silvio Gutkind

Supplementary Figure S3 shows Scheme of the m7GTP pull down (A) and eIF4G co-IP assays (B) depicting the regulation of ribosomal translation-initiating complex formation by mTOR and 4EBP; and C, densitometry analysis of figure 2C.


National Institute of Dental and Craniofacial Research

National Natural Science Foundation of China



Aberrant activation of the PI3K–mTOR signaling pathway occurs in >80% of head and neck squamous cell carcinomas (HNSCC), and overreliance on this signaling circuit may in turn represent a cancer-specific vulnerability that can be exploited therapeutically. mTOR inhibitors (mTORi) promote tumor regression in genetically defined and chemically induced HNSCC animal models, and encouraging results have been recently reported. However, the mTOR-regulated targets contributing to the clinical response have not yet been identified. Here, we focused on EIF4E-BP1 (4E-BP1), a direct target of mTOR that serves as key effector for protein synthesis. A systematic analysis of genomic alterations in the PIK3CA–mTOR pathway in HNSCC revealed that 4E-BP1 is rarely mutated, but at least one 4E-BP1 gene copy is lost in over 35% of the patients with HNSCC, correlating with decreased 4E-BP1 protein expression. 4E-BP1 gene copy number loss correlated with poor disease-free and overall survival. Aligned with a tumor-suppressive role, 4e-bp1/2 knockout mice formed larger and more lesions in models of HNSCC carcinogenesis. mTORi treatment or conditional expression of a mutant 4E-BP1 that cannot be phosphorylated by mTOR was sufficient to disrupt the translation–initiation complex and prevent tumor growth. Furthermore, CRISPR/Cas9–targeted 4E-BP1 HNSCC cells resulted in reduced sensitivity to mTORi in vitro and in vivo. Overall, these findings indicate that in HNSCC, mTOR persistently restrains 4E-BP1 via phosphorylation and that mTORi can restore the tumor-suppressive function of 4E-BP1. Our findings also support 4E-BP1 expression and phosphorylation status as a mechanistic biomarker of mTORi sensitivity in patients with HNSCC. These findings suggest that EIF4E-BP1 acts as a tumor suppressor in HNSCC and that 4E-BP1 dephosphorylation mediates the therapeutic response to mTORi, providing a mechanistic biomarker for future precision oncology trials.