CD8+T cell responsiveness to anti-PD-1 is epigenetically regulated by Suv39h1 in melanomas

Tumor-infiltrating CD8 + T cells progressively lose functionality and fail to reject tumors. The underlying mechanism and re-programing induced by checkpoint blockers are incompletely understood. We show here that genetic ablation or pharmacological inhibition of histone lysine methyltransferase Suv39h1 delays tumor growth and potentiates tumor rejection by anti-PD-1. In the absence of Suv39h1, anti-PD-1 induces alternative activation pathways allowing survival and differentiation of IFNγ and Granzyme B producing effector cells that express negative checkpoint molecules, but do not reach final exhaustion. Their transcriptional program correlates with that of melanoma patients responding to immune-checkpoint blockade and identifies the emergence of cytolytic-effector tumor-infiltrating lymphocytes as a biomarker of clinical response. Anti-PD-1 favors chromatin opening in loci linked to T-cell activation, memory and pluripotency, but in the absence of Suv39h1, cells acquire accessibility in cytolytic effector loci. Overall, Suv39h1 inhibition enhances anti-tumor immune responses, alone or combined with anti-PD-1, suggesting that Suv39h1 is an “epigenetic checkpoint” for tumor immunity.

Understanding CD8 + T cell response to immune checkpoint blockade at the molecular level is important for the design of more efficient cancer immune therapies. Authors show here that the histone lysine methyltransferase Suv39h1 controls the transcriptional programs that determine the functionality of CD8 + T cells and Suv39h1 inhibition may potentiate anti-PD-1 therapy of melanomas.

Abstract B14: Discovery of YAP-TEAD protein-protein interaction inhibitors (PPI) for treating malignant pleural mesothelioma (MPM)

We have recently reported the development of YAP-TEAD interaction inhibitors that disrupt the YAP-TEAD complex and block proliferation of tumor cells. These compounds represent promising new treatment modalities for mesothelioma where the Hippo pathway is highly deregulated, with around 45% of MPM cases displaying a mutation of NF2 or LATS and predominantly nuclear YAP localization. MPM is an extremely aggressive disease with limited treatment options and no cure and is inherently chemoresistant, with only 50% of patients responding to the standard-of-care treatment; consequently, it has a very poor prognosis. The aim of this study was to support a multipronged approach to treat MPM. We have first established the in vitro proof of concept using siRNA experiments. Then, we have evaluated the effect of several Inventiva compounds (YAP-TEAD inhibitors) on the proliferation of a well-characterized YAP-dependent mesothelioma cell line (H2052) and on a large panel of MPM cells. We have further demonstrated the mechanism of action (MOA) of our compounds investigating the nuclear localization of YAP, the YAP-TEAD interactions, and the YAP protein expression levels in H2052 cancer cell line. To demonstrate the MOA, we have used immunofluorescence, proximity ligation assay, as well as Co-IP and Western blot experiments. Furthermore, we have examined the effect of IVA compounds in combination with the standard-of-care agent pemetrexed in a 3D spheroid model, and demonstrated the target engagement by looking at YAP-TEAD target gene expression. The effect of IVA compounds has been compared to this obtained with siRNA transfection. To assess the efficacy of pemetrexed +/- Inventiva compounds, we exposed H2052 cells to either each of the single agents or to their combination for 4 or 15 days in 2D or in 3D cultures. We used EdU incorporation assay or the measure of the spheroid area to access cell proliferation. We found a synergistic effect between YAP-TEAD inhibitors and pemetrexed, leading to a drastic inhibition of cancer cell proliferation and an increase of cytotoxicity. This suggests that YAP-TEAD inhibitors used in combination with existing chemotherapeutics could be used to attenuate multidrug resistance and resensitize chemoresistant cancer cells. We are currently exploring the effect of Inventiva compounds in H2052 mouse xenograft model. This study will be expanded to other indications and combination strategies where standard-of-care agents are ineffective and YAP is activated.

Citation Format: Anne Soudé, Martine Barth, Jean-Michel Luccarini, Séverine Delaporte, Florence Chirade, Christelle Valaire, Aude Boulay, Geneviève Cheret, Marie Dorchie, Céline Estivalet, Pascale Tuya-Boustugue, Robin Tranchand, Didier Jean, Lisa Quetel, Jean-Baptiste Assié, Irena Konstantinova, Jean-Louis Junien, Pierre Broqua. Discovery of YAP-TEAD protein-protein interaction inhibitors (PPI) for treating malignant pleural mesothelioma (MPM) [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr B14.