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Expression data from GNMT knockout mice in Hepatocytes and OKER cell lines

ABSTRACT: Hepatocellular carcinoma (HCC) is the first cause of death in cirrhotic patients. Liver cirrhosis at a high risk of HCC has abnormal S-Adenosylmethionine (SAMe) levels. Catabolism of SAMe is mainly mediated by Glycine N-methyltransferase (GNMT), Lack in GNMT expression leads to epigenetic regulation of critical carcinogenesis pathways and mounting evidence assigns an essential role of GNMT in HCC. Methods: Here we have studied the role of LKB1-AMPK and RAS in the proliferation and transformation of GNMT-deficient HCC. Results. GNMT-deficient HCC was characterized by LKB1-AMPK misconnection, leading to resistance of apoptosis response mediated by a positive regulation of cAMP-PKA-CaMKKβ cascade. Additionally, Ras-mediated hyperactivation of LKB1 contributes to the proliferation of GNMT-deficient HCC in an ERK/p90RSK-dependent manner. The observed LKB1-induced Ras activation, was due to the regulation of RASGRP3 expression. Notably, the human HCC tumors with poorer prognosis showed the lowest levels of GNMT, p-AMPKα(Thr172) and the highest activation of Ras/LKB1/RASGRP3 axis. The present data suggest a correlation between LKB1 and RAS activity in a context of HCC with low GNMT expression, indicating that activation of the RAS/LKB1/RASGRP3 cascade might possess an important prognostic role in human liver cancer. Furthermore, these findings open the possibility to design new therapeutic strategies for the treatment of liver cancer.

ORGANISM(S): Mus musculus

PROVIDER: GSE34838 | GEO | 2012/07/01

SECONDARY ACCESSION(S): PRJNA150211

REPOSITORIES: GEO

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Project description:Purpose: Mutations in STK11 (LKB1) occur in 17% of lung adenocarcinoma (LUAD) and drive a suppressive (cold) tumor immune microenvironment (TME) and resistance to immunotherapy. The mechanisms underpin the establishment and maintenance of a cold TME in LKB1 mutant LUAD remain poorly understood and the identification of downstream effectors is critical to inform therapeutic strategies to invigorate antitumor immunity. In this study, we investigated the association between inactivation of AMPK, one of the downstream substrates of LKB1, and immune evasion in human LUAD as well as the causal role of AMPK on TME in genetically engineered mouse model (GEMM) of LUAD. Experimental Design: We modeled AMPK inactivation in vivo using GEMM by deleting both AMPKα1 (Prkaa1) and AMPKα2 (Prkaa2) in KrasG12D-driven LUAD (KAA). Furthermore, we investigated the impact of AMPK inactivation on immune cell infiltration and global gene-expression programs of murine LUAD. Gene expression signature from AMPK-deficient murine LUAD was further compared to that of Lkb1 deficient murineLUAD as well as human LUAD with either LKB1 mutation or attenuated AMPK phosphorylation. Results: Inactivation of both AMPKα1 and AMPKα2 accelerates KrasG12D-driven LUAD. AMPK-deficient tumors are characterized with reduced infiltration of CD8+/CD4+ T cells and gene signatures associated with compromised immune microenvironment, which resembles LKB1-deficient murine and human LUAD (KL) as well as LKB1-wildtype LUAD with reduced AMPK phosphorylation. Attenuation of the MHC Class 1 component ß2 microglobulin (ß2M) was identified as a shared feature in KL and KAA murine LUAD as well as in human LUAD with either LKB1 mutations or reduced AMPK phosphorylation. Furthermore, reactivation of AMPK by expression of constitutive active form of AMPKα1 leads to restoration of ß2M level in LKB1 mutant LUAD cells. Conclusions: The results identify attenuation of the LKB1 substrate AMPK as an important mechanism for decreased MHC Class 1 expression and immune evasion in LKB1 mutant LUAD. Translational relevance: LKB1 loss-of-function mutations rank as the third most common genetic alterations found in lung adenocarcinoma and associated with immune evasion. In the current study, on the basis of GEMM of LUAD we established the causal relationship between inactivation of the LKB1 substrate AMPK and immune evasion. Furthermore we find that the status of AMPK phosphorylation is more sensitive than LKB1 mutation in predicting impaired tumor immune microenvironment and likely also for the resistance to immunotherapy. The results also suggest that restoration of AMPK activity could increase the number of patients benefiting from immunotherapy.

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Expression data from GNMT knockout mice in Hepatocytes and OKER cell lines

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