Abstract 285: Targeting TXNDC5 in stromal fibroblasts resolves desmoplasia and resistance to immune checkpoint blockade in mesenchymal-type colorectal cancer
Authors: Cheng Kai-Lin , Chen Chih-I , Yu Shu-Han , Liang Huai-Wen , Tsai Yi-Wei , Hung Chen-Ting , Lin Yu-Shan , Tzeng Yi-Shiuan , Lin Sung-Jan , Wu Yueh-Feng , Lee Jen-Kuang , Yu Chia-Hui , Lin Shuei-Liong , Chen Shih-Yu , Wei Tzu-Tang , Huang Yun-Ju , Chen Ruey-Hwa , Chen Ching-Chow , Yang Kai-Chien 
Published: March 2024

Abstract
Objectives: Mesenchymal-type colorectal cancer (CRC), characterized by strong stromal infiltration and immune tolerance, resists immune checkpoint blockade and has poor outcomes. Cancer-associated fibroblasts (CAFs), abundant in tumor stroma, actively remodel the extracellular matrix (ECM), modulate immune evasion, and drive tumor progression. We have recently identified thioredoxin domain-containing protein 5 (TXNDC5), a protein disulfide isomerase (PDI), as a critical mediator of fibroblast activation and ECM remodeling in organ fibrosis. We hypothesized that TXNDC5 could contribute to fibroblast activation, stroma formation and disease progression in cancer, especially in the stroma-enriched fibrogenic mesenchymal-type CRC.
Methods: Transcriptome databases of CRC were re-analyzed to determine the clinical relevance of TXNDC5. Experimentally, CRC was induced in mouse lines by azoxymethane (AOM) and dextran sulfate sodium (DSS) stimuli, a model sharing multiple characteristics with human mesenchymal-type CRC. Human colonic fibroblast line CCD-18co was used to investigate the molecular mechanisms by which TXNDC5 regulates colonic fibroblast activities. Fibroblast-specific TXNDC5 knockout (Col1a2-Cre/ERT2*TXNDC5fl/fl) mice were generated, combining with single-cell RNA sequencing analyses on AOM/DSS-induced CRC tumors in these animals, to clarify how fibroblast TXNDC5 impact tumor microenvironment, CRC progression and response to immune checkpoint blockade.
Findings: TXNDC5 was predominantly expressed in stromal fibroblasts of human and mouse CRC. Fibroblast-specific deletion of Txndc5 lessened CAF activation, attenuated tumor fibrosis and reduced tumor burden in AOM/DSS-induced CRC. Mechanistically, increased TXNDC5 levels augments TGFβ signaling in CAF by post-translational stabilization of TGFBR1 through its PDI activity. In addition, deletion of Txndc5 in CAFs led to less tumor desmoplasia, decompressed tumor vessels and attenuated intra-tumoral hypoxia, thereby easing immune tolerance and increasing cytotoxic T cell infiltration in CRC. Single-cell transcriptome analysis revealed a marked change of intra-tumoral immune cell populations upon fibroblast-specific deletion of TXNDC5, shifting from myeloid-derived suppressive cells to cytotoxic tumor-infiltrating lymphocytes. Importantly, depletion of TXNDC5 in CAFs potentiated the anti-tumor effects of immune checkpoint blockade with anti-PD1 therapy in CRC.
Conclusions: Our data suggest an important yet previously unrecognized role of fibroblast TXNDC5 in CRC progression, through enhancing CAF activation, stroma formation and immune escape. Combining immune checkpoint blockade with TXNDC5 deletion synergistically improved anti-tumor effects in CRC. Targeting TXNDC5, therefore, can be a novel therapeutic approach for CRC patients.
Citation Format: Kai-Lin Cheng, Chih-I Chen, Shu-Han Yu, Huai-Wen Liang, Yi-Wei Tsai, Chen-Ting Hung, Yu-Shan Lin, Yi-Shiuan Tzeng, Sung-Jan Lin, Yueh-Feng Wu, Jen-Kuang Lee, Chia-Hui Yu, Shuei-Liong Lin, Shih-Yu Chen, Tzu-Tang Wei, Yun-Ju Huang, Ruey-Hwa Chen, Ching-Chow Chen, Kai-Chien Yang. Targeting TXNDC5 in stromal fibroblasts resolves desmoplasia and resistance to immune checkpoint blockade in mesenchymal-type colorectal 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 285.