Abstract 6882: Exploring aryl hydrocarbon receptor expression and distribution in the tumor microenvironment, with a focus on immune cells, in various solid cancer types

Abstract Background: The aryl hydrocarbon receptor (AhR) is a transcription factor that performs various biological functions upon ligand activation. While there have been extensive studies and development of AhR-targeting anticancer therapies, including active clinical trials, research on the expression of AhR, a key biomarker, in the TME remain limited. Herein, we evaluated the nuclear and cytosolic AhR expression across five solid cancer types: head and neck squamous cell carcinoma (HNSCC), bladder cancer, colorectal cancer, esophageal cancer, and non-small cell lung cancer (NSCLC). Methods: Multiplexed immunohistochemistry (mIHC) and image cytometry were employed to investigate the AhR expression and distribution in 513 patient samples, of which 292 were from patients with one of five solid cancer types. For quantification of AhR expression levels, FCS files were generated, and the resulting data was analyzed using the R program. Results: AhR expression was predominantly high in cancer cells, followed by T cells and macrophages across all cancer types. All 513 patient samples were categorized into three clusters based on distinct expression and localization patterns of AhR. Cluster 1 exhibited high AhR expression in the cancer cell nucleus, whereas cluster 3 showed the lowest. AhR expression in the stromal macrophage nucleus was the most pronounced in cluster 2. In cluster 1, NSCLC was entirely absent, with esophageal cancer representing the largest proportion. In contrast, cluster 2 was notably different from cluster 1, with a 5% prevalence of NSCLC and a relatively higher proportion of HNSCC and colorectal cancer. The AhR expression in macrophages within cluster 2 was noticeably higher than in cluster 1. Cluster 3, which had the highest NSCLC proportion, generally displayed low AhR expression compared to other clusters, but also exhibited AhR expression in regulatory T cells (Tregs), a pattern which was not observed in other cancer types. Notably, a positive correlation was observed between the nuclear and cytosolic expressions of AhR, suggesting that AhR expression as a biomarker is independent of its subcellular localization. Furthermore, there was no clear correlation between AhR expression levels and cancer stage, grade, and metastatic status. Conclusion: We elucidated the expression profile of AhR within the TME across five cancer types, then classified the patient samples into three clusters based on their distinct AhR expression patterns. By demonstrating different expression patterns of AhR in cancer cells and immune cells, our findings are anticipated to provide a fundamental basis for clinical and immunological research on AhR-targeting therapies. Citation Format: Dong Kwon Kim, Chai Young Lee, Yu Jin Han, So Young Park, Heekyung Han, Kwangmin Na, Mi Hyun Kim, Seung Min Yang, Sujeong Baek, Youngtaek Kim, Joon Yeon Hwang, Seul Lee, Seong-san Kang, Taedong Han, Hyounmie Doh, Jongho Cho, Dajeong Kim, Daewon Cha, Min Hee Hong, Sun Min Lim, Jii Bum Lee, Jae Hwan Kim, Kyoung-Ho Pyo, Byoung Chul Cho. Exploring aryl hydrocarbon receptor expression and distribution in the tumor microenvironment, with a focus on immune cells, in various solid cancer types [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 6882.