Abstract LB349: Cysteine restriction enhances antitumor immunity in colorectal cancer

Abstract Background: Colon cancer is the second leading cause of cancer mortality worldwide, however, there are still issues with multidrug resistance and severe adverse reactions. Previous studies have shown that sulfur-containing amino acids are involved in cancer development, drug resistance, and immune evasion. Here, Our experimental findings suggested that restricting the intake of sulfur-containing amino acids may present a novel strategy for treating colorectal cancer. Methods: We assessed the impact of sulfur-containing amino acid restriction (SAR) on distinct cellular subpopulations within the tumor microenvironment through single-cell sequencing on colon carcinogenesis induced by azoxymethane/dextran sodium sulfate (AOM/DSS). Employing our custom-produced neutralizing antibodies against SLC7A11 to restrict cysteine intake, we examined the therapeutic implications and underlying molecular mechanisms by RNA-seq, Multiplexed immunofluorescence staining and Western blotting. Results: In the AOM/DSS model, SAR led to a slight reduction in mouse body weight compared to the normal diet. However, this dietary restriction significantly enhanced the survival rate of mice and effectively suppressed tumor growth. The single-cell sequencing results indicated a significant increase in the proportion of T cells within the tumor microenvironment in response to SAR. This suggested that restricting the intake of sulfur-containing amino acids may be a promising anti-tumor strategy. Previous studies have indicated high expression of the SLC7A11, a cysteine transporter protein, in various cancers, including colorectal cancer. To further investigate the role of cysteine in colorectal cancer, we developed the neutralizing antibody 1A4 against SLC7A11. Our results indicated that 1A4 markedly inhibited colorectal cancer development in mice. As known, 85% of colorectal cancers are microsatellite stable, which hardly benefit from treatment with immune checkpoint inhibitors (ICIs). Compared to anti-PD-1 and anti-CTLA4, 1A4 significantly inhibited the growth of CT26 in vivo. Multiplexed immunofluorescence staining results demonstrated that 1A4 significantly increased the proportion of CD8+ T cells in colorectal cancer tissues. Conclusion: Limiting cysteine intake significantly inhibits the growth of colorectal cancer, increases the proportion of CD8+ T cells, and enhances anti-tumor immunity. Citation Format: Jichang Li, Kang Xia, Zeruo Yang, Xiaoxue Pan, Xiaojing Yang, Pengyuan Wang, Shanwen Chen. Cysteine restriction enhances antitumor immunity in colorectal cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (7Suppl): Abstract nr LB349.