Targeting the RNA m6A modification for cancer immunotherapy

Abstract N 6 -methyladenosine (m 6 A) is the most abundant epigenetic modification of RNA, and its dysregulation drives aberrant transcription and translation programs that promote cancer occurrence and progression. Although defective gene regulation resulting from m 6 A often affects oncogenic and tumor-suppressing networks, m 6 A can also modulate tumor immunogenicity and immune cells involved in anti-tumor responses. Understanding this counterintuitive concept can aid the design of new drugs that target m 6 A to potentially improve the outcomes of cancer immunotherapies. Here, we provide an up-to-date and comprehensive overview of how m 6 A modifications intrinsically affect immune cells and how alterations in tumor cell m 6 A modifications extrinsically affect immune cell responses in the tumor microenvironment (TME). We also review strategies for modulating endogenous anti-tumor immunity and discuss the challenge of reshaping the TME. Strategies include: combining specific and efficient inhibitors against m 6 A regulators with immune checkpoint blockers; generating an effective programmable m 6 A gene-editing system that enables efficient manipulation of individual m 6 A sites; establishing an effective m 6 A modification system to enhance anti-tumor immune responses in T cells or natural killer cells; and using nanoparticles that specifically target tumor-associated macrophages (TAMs) to deliver messenger RNA or small interfering RNA of m 6 A-related molecules that repolarize TAMs, enabling them to remodel the TME. The goal of this review is to help the field understand how m 6 A modifications intrinsically and extrinsically shape immune responses in the TME so that better cancer immunotherapy can be designed and developed.