Gene Expression Signature Quantifies the Cellular Contribution of the Tumor Vs. the Microenvironment in Determining Colorectal Cancer Prognosis and Therapeutic Outcome

Abstract Accumulating evidence has suggested that cancer progression and therapeutic response may depend on not only tumor cells but also their tumor microenvironment (TME). However, their contributory roles are complex and not well understood. Here we report an analysis of 2373 human colorectal cancer (CRC) tumors representing all stages, leading to identification of a 20-gene signature capable of quantifying the cellular contribution of the tumor vs. the TME in determining colorectal cancer prognosis and therapeutic outcome. We classified these tumors into the consensus molecular subtypes (CMS1-4) with distinct, variable TME cellular features defined by CIBERSORT deconvolution analysis of bulk gene expression data. Surprisingly, all the 10 positive signature genes (portending worse survival) were strongly correlated with the TME-rich CMS1 and CMS4 tumors. By contrast, all the 10 negative signature genes (portending better survival) were highly related to the TME-poor CMS2 and CMS3 tumors. A single cell expression analysis from an independent database further revealed that strikingly, all the 10 positive genes were principally expressed by the immune/stromal TME whereas all the 10 negative genes were predominantly expressed in epithelial tumor cells. These data suggest that the TME has an equally important role as do tumor cells in determining CRC prognosis and support targeting the TME to improve survival. Moreover, distinct gene expression from tumor cells versus the TME also showed a differential impact on therapeutic outcome. Retrospective analyses on two independent clinical trial datasets show that the 20-gene signature score significantly predicted progression free survival in metastatic CRC patients treated with cetuximab, an FDA-approved EGFR inhibitor therapy. These data suggest a potential for the 20-gene signature as a predictive biomarker to identify “sensitive” versus “resistant” subpopulations of CRC patients to improve outcome of EGFR-targeted therapy. Citation Format: Mingli Yang, Timothy J. Yeatman, Michael V. Nebozhyn, Michael J. Schell, Lance Pflieger, Andrey Loboda, Warren J. Pledger, Ramani Soundararajan, Michelle Maurin, Heiman Wang, Jetsen Rodriguez Silva, Ashley Alden. Gene expression signature quantifies the cellular contribution of the tumor vs. the microenvironment in determining colorectal cancer prognosis and therapeutic outcome [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 6430.