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KrasG12D/+ co-mutation alters the transcriptional landscape of lung adenocarcinoma

ABSTRACT: The tumor microenvironment (TME) contains a rich source of nutrients that sustain cell growth and ultimately facilitate tumor progression. The availability of glucose and glutamine in the TME are essential for the development and activation of effector T cells that exert anti-tumor function. Recently, inhibition of glutaminase, the enzyme that hydrolyzes glutamine to glutamate, has garnered interest as an approach to both decrease tumor metabolism and growth, while increasing available glutamine in the TME for effector T cells. Checkpoint blockade immunotherapy unleashes anti-tumor effector capabilities of T cells, and although there are good responses in many solid tumors, a significant proportion of patients respond poorly. In lung adenocarcinoma, response to immunotherapy is reported to be impaired in KRAS-mutant patients harboring concurrent KEAP1 and STK11/Lkb1 mutations. To investigate the metabolism and immune microenvironment of KRAS-mutant lung adenocarcinoma, we generated a series of murine models that reflect the KEAP1 and STK11/Lkb1 mutational landscape seen in patients. Here we show increased glutamate abundance in the Lkb1-deficient TME associated with CD8 T cell activation in response to anti-PD1 checkpoint immunotherapy. Combination treatment with the glutaminase inhibitor CB-839 inhibited clonal expansion and cytotoxic activation of tumor-infiltrating CD8 T cells. Thus, CD8 T cells exposed to checkpoint immunotherapy have a dependence on glutamine and reliance on glutaminase activity and are negatively impacted by the glutaminase inhibitor in this highly activated state. Therefore, we discern that the combination of immunotherapy and glutaminase inhibition is not efficacious for CD8 T cell activation in the tumor microenvironment.

ORGANISM(S): Mus musculus

PROVIDER: GSE193895 | GEO | 2022/05/02

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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KrasG12D/+ co-mutation alters the transcriptional landscape of lung adenocarcinoma

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