Leveraging cancer-evolved resistance mechanisms to enhance EZH2 activity in adoptive T cells

Abstract The clinical landscape of metastatic melanoma has been revolutionized by immune checkpoint blockade (ICB); however, despite these advancements, the effectiveness of ICB for metastatic melanoma is limited to approximately half of patients1. The development of acquired resistance, in part through the loss of MHC-I

antigen presentation, leaves most patients to experience disease progression2–5. Recent advancements have highlighted the use of adoptive cell therapy (ACT) for treatment of ICB resistant melanoma (e.g., CAR T cells)6– 8. However, the solid tumor microenvironment (TME) presents a critical barrier for success of T cell-based

therapies largely due to the direct competition between tumor-infiltrating lymphocytes (TILs) and cancer cells for metabolic resources, rendering T cells dysfunctional and exhausted9,10. There is an urgent clinical need for the development of new strategies to engineer adoptive T cells with the ability to sustain function in the harsh solid

TME, particularly if these approaches can be combined with other therapies (e.g., small molecule targeted therapy) to improve clinical outcomes. Our group and others have recently reported that TME-induced environmental stress leads to epigenome remodeling events within TILs, including loss of the histone methyltransferase EZH211. EZH2, a key component

of the Polycomb Repressive Complex 2 (PRC2), induces the repression of gene transcription via methylation of lysine 27 of Histone H3 (H3K27me3)12. Loss of EZH2, and thereby H3K27me3, in activated T cells leads to transcriptional reprogramming that results in an exhausted T cell phenotype. Our Preliminary Data suggests that

protecting EZH2 activity in activated T cells circumvents this exhaustion and produces a T cell with durable activity in the harsh TME. Preliminary Data presented herein, and evidence previously reported by independent groups, support the premise of our proposal that protection of T cell EZH2 expression and/or activity will create

a more durable and potent ACT. In this innovative proposal, we will rigorously test the hypothesis that preserving EZH2 function in T cells will enable adoptive T cells to persist and function in the melanoma tumor environment. To test our hypothesis, we will pursue the following Specific Aims: (1) Demonstrate enhanced EZH2 activity can

protect T cell function in the solid tumor microenvironment, and (2) Engineer EZH2i resistant CAR T cells for combinatorial treatment of metastatic melanoma.