Abstract 5841: Exploring the role of versican in immune exclusion within triple negative breast cancer

Abstract

Abstract Immunotherapy has found limited success in solid tumors such as triple negative breast cancer (TNBC). The poor response can be attributed to the presence of the extracellular matrix (ECM) that can act biochemically or physically to interfere with cytotoxic T cell migration, leading to a limitation in tumor cell killing. Through previous work on deconstructing this matrix and outlining the spatial arrangement of proteins, we were able to identify versican as a key protein in T cell location. Versican is a chondroitin sulfate proteoglycan and has multiple functions in the ECM due to its ability to bind many ECM components. Using immunohistochemistry in this study, we analyzed the localization of CD8+ T cells within human TNBC tissues to classify them as inflamed (tumorhi, stromahi), desert (tumorlo, stromalo) or immune excluded (tumorlo, stromahi). From the analysis of 26 tissues, nearly half were classified as immune excluded with most of the CD8+ T cells restricted to the stroma, whilst only a quarter were inflamed. When comparing this to versican accumulation we noticed that immune excluded tissues have significantly higher levels of versican in the tumor epithelium compared to inflamed tissues where versican is mostly found within the stroma. To investigate the function of versican’s structure, we carried out transwell migration assays using versican enriched protein treated with or without chondroitinase ABC and showed that the chondroitin sulfates attached to versican’s peptide backbone are an important factor towards T cell trafficking with a reduction in migration following chondroitinase ABC treatment. Comparison of versican levels to chondroitin sulfate via immunohistochemistry showed a positive correlation within inflamed tissues, however no correlation was observed in immune excluded tissues. Versican isoforms expression in TNBC tissues and cell lines was examined with qRT-PCR which showed that within all tissues and cell lines the V0 and V1 isoform are the highest expressed out of the 5 isoforms. Overall, in this work, we have found that versican is differentially expressed in excluded tissues in comparison to inflamed tissues. With chondroitin sulfate shown to play a major role in immune cell trafficking, understanding how it differs between inflamed and excluded tumors can help identify potential targets to improve immunotherapy response. Citation Format: Priyanka Hirani, Kimberly M. Alonge, Daniel J. Pennington, Pedro R. Cutillas, Thomas N. Wight, Oliver M. Pearce. Exploring the role of versican in immune exclusion within triple negative breast cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5841.