MAPK4 overexpression promotes tumor progression via noncanonical activation of AKT/mTOR signaling
Wei Wang, Tao Shen, Bingning Dong, Chad J. Creighton, Yanling Meng, Wolong Zhou, Qing Shi, Hao Zhou, Yinjie Zhang, David D. Moore, Feng Yang
Wei Wang, Tao Shen, Bingning Dong, Chad J. Creighton, Yanling Meng, Wolong Zhou, Qing Shi, Hao Zhou, Yinjie Zhang, David D. Moore, Feng Yang
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Research Article Cell biology Oncology

MAPK4 overexpression promotes tumor progression via noncanonical activation of AKT/mTOR signaling

Abstract

MAPK4 is an atypical MAPK. Currently, little is known about its physiological function and involvement in diseases, including cancer. A comprehensive analysis of 8887 gene expression profiles in The Cancer Genome Atlas (TCGA) revealed that MAPK4 overexpression correlates with decreased overall survival, with particularly marked survival effects in patients with lung adenocarcinoma, bladder cancer, low-grade glioma, and thyroid carcinoma. Interestingly, human tumor MAPK4 overexpression also correlated with phosphorylation of AKT, 4E-BP1, and p70S6K, independent of the loss of PTEN or mutation of PIK3CA. This led us to examine whether MAPK4 activates the key metabolic, prosurvival, and proliferative kinase AKT and mTORC1 signaling, independent of the canonical PI3K pathway. We found that MAPK4 activated AKT via a novel, concerted mechanism independent of PI3K. Mechanistically, MAPK4 directly bound and activated AKT by phosphorylation of the activation loop at threonine 308. It also activated mTORC2 to phosphorylate AKT at serine 473 for full activation. MAPK4 overexpression induced oncogenic outcomes, including transforming prostate epithelial cells into anchorage-independent growth, and MAPK4 knockdown inhibited cancer cell proliferation, anchorage-independent growth, and xenograft growth. We concluded that MAPK4 can promote cancer by activating the AKT/mTOR signaling pathway and that targeting MAPK4 may provide a novel therapeutic approach for cancer.

Authors

Wei Wang, Tao Shen, Bingning Dong, Chad J. Creighton, Yanling Meng, Wolong Zhou, Qing Shi, Hao Zhou, Yinjie Zhang, David D. Moore, Feng Yang

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Figure 9

AKT activation is crucial for mediating MAPK4 tumor-promoting activity.

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AKT activation is crucial for mediating MAPK4 tumor-promoting activity. ...
(A) Soft agar assays comparing the anchorage-independent growth of PNT1A cells with Dox-induced expression of WT MAPK4 (WT+Dox), MAPK4S186A (S186A+Dox), and MAPK4D254A mutant (D254A+Dox). The PNT1A-iMAPK4 cells without Dox induction (WT-Dox) were used as control. Higher magnifications are shown in the bottom panels. Original magnification: ×50 (A and B). Western blots were used to confirm comparable levels of Dox-induced MAPK4 expression, and for detection of AKT phosphorylation. (B) Soft agar assays comparing the anchorage-independent growth of the Dox-induced PNT1A-iMAPK4 cells under different treatments as indicated. Western blots were used to assess AKT activation status (phosphorylation of GSK3β) in these cells. (C) Quantification of colony numbers in the soft agar assays in A and B. The group labeled WT contains both the WT+Dox group in A and the DMSO group in B. The q values were calculated and used to account for the FDR in the multiple comparisons (32). No test was applied to the WT+MK2206 group because no colonies were found. Data are mean ± SEM. **q < 0.01, ***q < 0.001. (D) Cell counting comparing the proliferation of HCT116 cells with (+) and without (–) Dox-induced expression of WT AKT1, and the T308D/S473D (DD) and K386A mutants. Western blots were used to confirm comparable levels of induced AKT1 expression. (E) Cell counting comparing the proliferation of HCT116 MAPK4-KO (KO, clone 4) cells with (+) and without (–) Dox-induced expression of WT AKT1 and the T308D/S473D (DD) mutant AKT1. Data are mean ± SEM. P values determined by unpaired 2-tailed Student’s t test. **P < 0.01. Western blots were used to confirm comparable levels of induced AKT1 expression. Data are representative of at least 3 independent experiments.