Suppressive activity of MDSCs isolated from CT26 WT or CT26 SKT11 KO tumors and pharmacological reversal by STAT3 ASO treatment in the CT26 WT model. (A) Percentage of naive T cell proliferation by anti-CD3/CD28/IL2 stimulation in the presence of Gr1+ MDSCs isolated from CT26 WT or CT26 STK11 KO tumors (left), as indicated. Error bars represent SEM from technical replicates of MDSCs pooled from multiple tumors. P-values calculated using two-tailed Student's T test. Proliferation of non-stimulated T cells and anti-CD3/CD28/IL2-stimulated T cells used as controls in the assay are also shown (right). (B) Percentage T cell proliferation when co-cultured with MDSCs from mice engrafted with CT26 WT tumors and administered either CPIs and/or STAT3 ASO, or isotype control antibodies, as indicated. The x-axis represents the MDSC:T cell ratio in the assay. The proliferation of the non-stimulated T cells and anti-CD3/CD28/IL2-stimulated T cells which were used as controls in the assay is also shown.
ARTICLE ABSTRACT
Mutations in the STK11 (LKB1) gene regulate resistance to PD-1/PD-L1 blockade. This study evaluated this association in patients with nonsquamous non–small cell lung cancer (NSCLC) enrolled in three phase I/II trials. STK11 mutations were associated with resistance to the anti–PD-L1 antibody durvalumab (alone/with the anti-CTLA4 antibody tremelimumab) independently of KRAS mutational status, highlighting STK11 as a potential driver of resistance to checkpoint blockade. Retrospective assessments of tumor tissue, whole blood, and serum revealed a unique immune phenotype in patients with STK11 mutations, with increased expression of markers associated with neutrophils (i.e., CXCL2, IL6), Th17 contexture (i.e., IL17A), and immune checkpoints. Associated changes were observed in the periphery. Reduction of STAT3 in the tumor microenvironment using an antisense oligonucleotide reversed immunotherapy resistance in preclinical STK11 knockout models. These results suggest that STK11 mutations may hinder response to checkpoint blockade through mechanisms including suppressive myeloid cell biology, which could be reversed by STAT3-targeted therapy.
Patients with nonsquamous STK11-mutant (STK11mut) NSCLC are less likely than STK11 wild-type (STK11wt) patients to respond to anti–PD-L1 ± anti-CTLA4 immunotherapies, and their tumors show increased expression of genes and cytokines that activate STAT3 signaling. Preclinically, STAT3 modulation reverses this resistance, suggesting STAT3-targeted agents as potential combination partners for immunotherapies in STK11mut NSCLC.This article is highlighted in the In This Issue feature, p. 2659
