Abstract LB237: PVRL2 suppresses antitumor immune responses through PVRIG- and TIGIT-independent pathways
Authors: Yang Jiuling , Wang Li , Byrnes James , Kirkemo Lisa , Driks Hannah , Belair Cassandra , Aguilar Oscar , Lanier Lewis , Wells Jim , Fong Lawrence , Blelloch Robert 
Published: April 2024

Abstract
In recent years, PVRL2 (also known as Nectin-2 or CD112), a member of the Nectin family, has emerged as a crucial regulator of anti-tumor immune responses. PVRL2 interacts with the co-inhibitory receptor PVRIG that is expressed on T cells and NK cells, inhibiting their function. This interaction has thus become the presumed mechanism for PVRL2’s immunoinhibitory function. Therapeutic development targeting the PVRL2 pathway has primarily focused on the receptor PVRIG, with two anti-PVRIG antibodies currently undergoing Phase 1/2 clinical trials (NCT03667716, NCT04570839, NCT05746897). However, to date, very few studies have directly investigated the role of PVRL2, and whether PVRL2 indeed acts through PVRIG hasn’t been formally tested.
Our recent work reveals the crucial role of PVRL2 in suppressing anti-tumor immune responses across multiple syngeneic mouse models. CRISPR-directed deletion of PVRL2 robustly reduced tumor growth in an immune-dependent manner, with an even greater effect than seen with the deletion of the prominent checkpoint, PD-L1. Specifically, our findings suggest that PVRL2 functions by suppressing CD8 T and NK cells in the tumor microenvironment. Interestingly, the impact of PVRL2 on tumor growth in our study is certainly much more significant than observed in previous work on PVRIG. To follow up on this interesting finding and determine whether the PVRL2’s impact on immune cells acts through PVRIG, we generated Pvrig KO mice. Surprisingly, we found that PVRL2’s function is largely independent of PVRIG, as it still robustly promotes tumor growth even in the absence of PVRIG, indicating PVRIG-independent mechanisms. We further demonstrate that PVRL2 operates in parallel to the PVR-TIGIT pathway, another important immunoregulatory pathway in the Nectin family. Combined deletion of PVR or PVRIG with PVRL2 loss did not further suppress tumor growth, while combined TIGIT blockade with PVRL2 loss resulted in the most substantial reduction in tumor growth.
These findings strongly indicate the existence of additional unknown receptors mediating PVRL2’s function that remain to be discovered. Importantly, our study uncovers PVRL2’s central role in suppressing anti-tumor immune responses through mechanism outside its presumed receptor PVRIG, providing a compelling rationale for directly targeting PVRL2 itself. Combining PVRL2 and TIGIT targeting results in a near-complete block in tumor growth, offering a novel and promising therapeutic approach for cancer immunotherapy through the combinatorial targeting of PVRL2 and TIGIT.
Citation Format: Jiuling Yang, Li Wang, James Byrnes, Lisa Kirkemo, Hannah Driks, Cassandra Belair, Oscar Aguilar, Lewis Lanier, Jim Wells, Lawrence Fong, Robert Blelloch. PVRL2 suppresses antitumor immune responses through PVRIG- and TIGIT-independent pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB237.