Expression profiling by high throughput sequencing
Summary
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.
Overall design
Mice of defined genotypes (n=5 mice per genotype) were administered intranasal Ad5-CMV-Cre to recombine genetic alleles. When moribund with breathing difficulties, tumor nodules were removed (2 independent nodules per mouse) and flash frozen in liquid nitrogen. Uninfected littermate control lungs were used as the "normal lung tissue". Lungs and tumor nodules were crushed in liquid nitrogen and RNA extracted using a combination of the QIAshredder and RNeasy kit.
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