Abstract 6048: Genome-wide CRISPR screening identifies tyrosylprotein sulfotransferase-2 as a target for augmenting anti-PD1 efficacy

Abstract Immune checkpoint therapy (ICT) offers durable responses in select cancer patients, yet resistance remains a significant challenge, prompting the exploration of underlying molecular mechanisms. We propose tyrosylprotein sulfotransferase-2 (TPST2), known for its role in protein tyrosine O-sulfation, as a suppressor of cancer immunity. Through in vivo genome-wide CRISPR screening, TPST2 loss-of-function emerged as a potential enhancer of anti-PD1 treatment efficacy. TPST2 suppressed interferon-γ (IFNγ) signaling by sulfating IFNγ receptor 1 at Y397 residue, while its downregulation boosted IFNγ-mediated signaling and antigen presentation. Depletion of TPST2 in cancer cells augmented anti-PD1 antibody efficacy in syngeneic mouse tumor models by enhancing tumor-infiltrating lymphocytes. RNA sequencing data revealed TPST2's inverse correlation with antigen presentation, and increased TPST2 expression is associated with poor prognosis and altered cancer immunity across cancer types. In an effort to develop novel cancer immunotherapies targeting TPST2, we have discovered LDD-5557, a lead compound with potent enzyme inhibitory activity through library screening and structure-based hit to lead optimization process. The lead compound showed an excellent in-vivo PK profile including high oral bioavailability and immunotherapeutic efficacies of significant upregulations of CD8 positive T-cells and antigen processing related genes in a dose-dependent manner by co-treatment with anti-PD1 in a MC38 syngeneic mouse model. These findings underscore TPST2's novel role in cancer immunity and advocate for its consideration as a therapeutic target in ICT-based treatments. Citation Format: Yumi Oh, Sung-Yup Cho, Sujeong Kim, Yunjae Kim, Hyun Kim, Hansoo Park, Yongsoo Jang, Soobin Park, Yong-Chul Kim. Genome-wide CRISPR screening identifies tyrosylprotein sulfotransferase-2 as a target for augmenting anti-PD1 efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6048.