Abstract 3219: STAT3 inhibition synergizes with epigenetic therapy to suppress glutamine metabolism and clonogenic potential in non-small cell lung cancer

Abstract Non-small cell lung cancer (NSCLC) remains one of the deadliest cancers with metastatic disease being the primary driver of mortality. Therefore, there is a critical need for therapies that prevent disease dissemination in both early and late-stage disease presentations. Among the recent novel therapeutic combinations that have transformed the treatment landscape of NSCLC is an approach developed in our lab and others utilizing DNA methyltransferase inhibition (DNMTi) paired with histone deacetylase inhibition (HDACi) to sensitize patients to immunotherapy. However, most patients do not benefit durably from epigenetic therapy alone or in combination with other therapies. In this study, we identified STAT3 as an actionable target in tumor cells that synergizes with epigenetic therapy (DNMTi+HDACi). We and others have previously shown that STAT3 signaling is augmented after epigenetic therapy. To interrogate the importance of this finding, we treated a panel of 12 human NSCLC cell lines with STAT3i+epigenetic therapy and identified five cell lines demonstrating a synergistic reduction of cell viability. These in vitro monolayer observations were recapitulated in an intermediate complexity 3D model, thus providing orthogonal validation of response applicability in a more treatment-resistant setting. In addition to phenotypic characterization, we deployed RNA sequencing to define the whole transcriptome consequences of our novel therapeutic paradigm. These transcriptional data showed that STAT3i+epigenetic therapy suppressed cell cycle and activated apoptotic pathways, which were validated by immunoblotting and flow cytometry-based approaches. We further demonstrated a significant and durable reduction in colony formation after treatment with STAT3i+epigenetic therapy. Additionally, we observed significant perturbation of a subset of genes involved in both epithelial-to-mesenchymal transition and suppression of glutamine and fatty acid metabolism. Reliance on glutamine is considered a hallmark of cancer metabolism. Furthermore, glutamine metabolism has been implicated in the plasticity between epithelial and mesenchymal cancer cell states, which is required for metastatic success. Additionally, survival of metastatic cells requires upregulation of pathways that promote anchorage-independent growth and anoikis resistance, which are suppressed in our phenotypic and transcriptional data, respectively. Taken together, our results suggest 1. STAT3i+epigenetic therapy diminishes the ability of NSCLC cells to survive and return to a colony-forming state and 2. This phenotype is associated with metabolic dysfunction. Our studies therefore provide a basis for the development of novel strategies to intercept metastatic recolonization by impairing circulating tumor cells from seeding distant sites. Citation Format: Julia An, Ying-Yu Chen, Jina Park, Stephen Baylin, Michael Topper. STAT3 inhibition synergizes with epigenetic therapy to suppress glutamine metabolism and clonogenic potential in 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 3219.