Abstract 1781: G9a/GLP inhibition during ex vivo lymphocyte expansion increases in vivo cytotoxicity of engineered T cells against hepatocellular carcinoma
Authors: Lam Maxine S. , Reales-Calderon Jose A. , Ow Jin Rong , Aw Joey , Tan Damien , Vijayakumar Ragavi , Ceccarello Erica , Tabaglio Tommaso , Lim Yan Ting , Chien Wang Loo , Lai Fritz , Tanoto Anthony Tan , Chen Qingfeng , Sobota Radoslaw M. , Adriani Giulia , Bertoletti Antonio , Guccione Ernesto , Pavesi Andrea 
Published: April 2023

Abstract
Adoptive cell transfer (ACT) has been highly efficient in targeting certain refractory cancers and remains potentially effective for other cancers as new targets of cancer-immune interactions are revealed. ACT involves isolating immunocompetent cells from cancer patients, expanding them ex vivo, and infusing them back into the patient. Cells used for ACT are often effector cells, typically T cells, isolated from the patient’s peripheral blood and then engineered to target cancer cells by incorporating a T cell receptor (TCR) or chimeric antigen receptor (CAR), with additional modifications to improve immune cell proliferation and persistence. While cell therapies for various lymphomas have led to dramatic tumor regressions, response in solid tumors remains varied. Solid tumors present unique challenges, such as tumor heterogeneity and the lack of tumor-specific targets, but also an immunosuppressive tumor microenvironment (TME) characterized by poor T cell infiltration and terminal T cell differentiation and exhaustion at the tumor. To overcome the hostile TME, lymphodepleting regimens combined with an infusion of large numbers of T cells is often used. However, introducing large numbers of T cells significantly increases the risk of on-target/off-target toxicity, neurotoxicity, and cytokine release syndrome. The use of engineered T cells that transiently express TCRs or CARs by mRNA gene transfer, reduces these risks. Additionally, they avoid the use of viral vectors, hence there is no risk of insertional mutagenesis and can be manufactured more easily at low cost and on a larger scale. Such transient-engineered T cells have shown significant antitumor activity in phase I clinical trials and in preclinical animal models. However, multiple infusions are often required, increasing patient discomfort and treatment cost. To mitigate this, we sought to improve the antitumor activity of transient engineered T cells by screening a panel of small molecules targeting epigenetic regulators for their effect on T cell cytotoxicity. Using a model for engineered T cells targeting hepatocellular carcinoma, we found that short-term inhibition of G9a/GLP increased T cell antitumor activity in in vitro models and an orthotopic mouse model. G9a/GLP inhibition increased granzyme expression without terminal T cell differentiation or exhaustion and resulted in specific changes in the expression of genes and proteins involved in pro-inflammatory pathways, T cell activation, and cytotoxicity.
Citation Format: Maxine S. Lam, Jose A. Reales-Calderon, Jin Rong Ow, Joey Aw, Damien Tan, Ragavi Vijayakumar, Erica Ceccarello, Tommaso Tabaglio, Yan Ting Lim, Wang Loo Chien, Fritz Lai, Anthony Tan Tanoto, Qingfeng Chen, Radoslaw M. Sobota, Giulia Adriani, Antonio Bertoletti, Ernesto Guccione, Andrea Pavesi. G9a/GLP inhibition during ex vivo lymphocyte expansion increases in vivo cytotoxicity of engineered T cells against hepatocellular carcinoma [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 1781.