Abstract 6529: Multi-lineage de-differentiation (MLDD) towards the TTF1-low phenotype is a major determinant of immune response within STK11-deficient non-small cell lung cancer
Authors: Shivahare Rahul , Song No Joon , Nourmohammadi Bahareh , Imam Jemal , Sanabria Olivia , Amann Joseph M. , Ma Qin , Li Zihai , Carbone David P. , Kaufman Jacob 
Published: March 2024

Abstract
Background: The loss of serine/threonine kinase 11 (STK11) in non-small cell lung cancer (NSCLC) is associated with poor prognosis and resistance to immune checkpoint blockade (ICB) in 20-25% of cases. Experimental evidence from murine models suggests that STK11 loss contributes to lineage plasticity, while clinical observations indicate its impact on differentiation phenotypes in patients. However, the intricate interplay between differentiation states, the tumor microenvironment (TME), and clinical outcomes remains poorly elucidated. This study aims to comprehensively characterize these interactions to enhance our understanding of the complex dynamics underlying STK11-deficient NSCLC pathogenesis and therapeutic responses.
Methods: By leveraging large multi-omics datasets, we already demonstrated the low immune infiltration in TTF1-low and neuroendocrine MLDD subsets of LKB1-deficient tumors. In this study, we used GEMM-derived two KPL (Kras, TP53, and STK11 mutations) and one KPL-restored line to inject subcutaneously in F1 hybrid mice of B6 and Sv129 backgrounds. Tumor size was monitored at regular intervals, and upon reaching a sufficient size, tumors were harvested and partitioned for the characterization of immune cells (T-cells and NK cells) by flow cytometry and identification of the MLDD phenotypes through gene expression analysis using Nanostring technology.
Results: Mice injected with the STK11 WT line (2695L) exhibited smaller tumor volumes compared to those injected with STK11 mutant lines (2695X and 2381T4). Our comprehensive analysis, combining flow cytometry and Nanostring techniques, revealed that STK11 mutant lines displayed notably low infiltration of CD8+ T-cells, an elevated proportion of exhausted T-cells, and a manifestation of the TTF1-low immune phenotype characterized by high myeloid-derived suppressor cells (MDSCs) and increased KLRC1/KLRC2 expression. The presence of MDSCs in the STK11 mutant line correlated with pro-inflammatory cytokines but exhibited an inverse correlation with MHC-2 expression. MHC-2 expression was inversely correlated with CD8+ T-cell percentage and positively correlated with naïve T-cell percentage.
Conclusions: The data obtained from the study indicates that the MDSC phenotype seems to be important for immune evasion in STK11-loss tumors. Follow-up flow cytometry and gene expression experiments with combined T-cells and myeloid/PMN MDSC-related gene panels, along with further experiments involving cIAP1/PD1 inhibitors, are imperative to substantiate and expand upon our current findings.
Citation Format: Rahul Shivahare, No Joon Song, Bahareh Nourmohammadi, Jemal Imam, Olivia Sanabria, Joseph M. Amann, Qin Ma, Zihai Li, David P. Carbone, Jacob Kaufman. Multi-lineage de-differentiation (MLDD) towards the TTF1-low phenotype is a major determinant of immune response within STK11-deficient non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6529.