Abstract 3420: Tgfbm3b is a natural germline genetic variant that modifies anti-tumor responses to anti-PD-1 immunotherapy through its action on the tumor microenvironment
Authors: Chen Szu-Ying , Mamai Ons , Akhurst Rosemary 
Published: June 2022

Abstract
Our goal for this study is to use a mouse genetics approach to identify host germline genetic variants that determine therapeutic responses to cancer immunotherapy (IMT) and to validate these findings in cancer patients treated with α-PD-1. The information gathered may lead to drug targets that potentiate IMT responses and genetic markers may contribute to risk scores for response to IMTs. Immune Checkpoint blockade (ICB) therapy leads to remarkable clinical responses, including highly durable complete responses in a fraction of patients. Consequently, α-PD-1/PDL-1 is now first-line therapy for treating melanoma and NSCLC (non-small cell lung carcinoma). However, most patients do not respond to α-PD-1 therapy, and few show systemic adverse effects. There is therefore an unmet need to develop biomarkers and drug targets that will potentiate therapeutic responses to ICBs. Firstly, we found that blockade of active TGFβ using therapeutic antibodies synergizes with α-PD-1 therapy to potentiate tumor rejection, thus, we hypothesized that variant genetic modifiers of TGFβ1 may influence outcomes of α-PD-1 therapy. By utilizing Tgfbm3b-C57BL/6 (Tgfbm3b-C57) mice carrying a genetic variation of TGFβ1 to study the anti-tumor response to IMT, we confirmed that Tgfbm3b-C57 potentiated anti-tumor responses to α-PD-1 and to combinatorial α-PD-1/α-TGFβ IMT with higher induction of CD8+ T cell-mediated anti-tumor cytotoxicity. The C57 allele contains gene Adam17 that encodes an amino acid variant, L613V, and a charge change at amino acid 113 (D113N). Protein ADAM17 is a sheddase that involves in TNFα biosynthesis and sheds the TGFβ type I receptor (TβRI) to attenuate TGFβ signaling. To understand the molecular function of the variants, the vectors encoding wildtype (NIH) ADAM17 that carries D113, L613 versus the variant (C57) ADAM17 that has N113, V613, are being transfected and tested for the action on a panel of ADAM17 substrates including TNFα and TβRI on NIH3T3 cell line. We are also investigating whether genetic variation within the syntenic human TGFBM3 locus confers differential survival benefit to patients after α-PD-1 therapy. We will confirm the genetic association of ADAM17 SNPs and screen the TGFBM3b locus from LPIN1 to HPCAL1, and YWHAQ to DDEF2. The dataset includes genome-wide association data from progression-free survival analysis of 2000 NSCLC patients following α-PD-1 therapy. The preliminary data from our initial cohort (n=862) of NSCLC patients on PD-1 inhibitors are currently being evaluated. By investigating the molecular and cellular mechanisms by which Tgfbm loci influence ICB outcomes and addressing the relevance to human cancer patients, this project not only addresses an important basic science question but may ultimately lead to novel biomarkers or drug targets that can improve IMT outcomes and reduce adverse effects.
Citation Format: Szu-Ying Chen, Ons Mamai, Rosemary Akhurst. Tgfbm3b is a natural germline genetic variant that modifies anti-tumor responses to anti-PD-1 immunotherapy through its action on the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3420.