Abstract 2022: E7386, a Wnt/β-catenin signaling modulator, suppresses the differentiation of regulatory T cells in combination with lenvatinib plus anti-PD-1 antibody
Authors: Shen Jialing , Ishida Ryoga , Kume Masahiko , Kimura Takayuki , Adachi Yusuke , Kato Yu 
Published: March 2024

Abstract
Background: E7386, a selective inhibitor of the interaction between β-catenin and CREB binding protein (CBP), showed antitumor activity in preclinical tumor models with aberrant activation of the Wnt/β-catenin signaling pathway. Previously, we reported the enhanced antitumor activity of a triple combination (E7386 in combination with Lenvatinib [LEN, a multiple receptor tyrosine kinase inhibitor mainly targeting VEGFRs and FGFRs] plus anti-PD-1 antibody) versus a 2-drug combination (LEN plus anti-PD-1 antibody). In this study, we further investigated the immunomodulatory functions of E7386 as a triple combination by single-cell RNA-sequencing (scRNA-Seq) analysis and subsequent functional assays.
Methods: Mice bearing subcutaneous RAG (mouse renal cell carcinoma) tumors were randomized into 4 groups (n=6 in each group), including ⑴ Nontreatment, ⑵ E7386 at 25 mg/kg (PO, QD), ⑶ LEN at 10 mg/kg (PO, QD) plus anti-PD-1 antibody at 10 mg/kg (IP, BIW), and ⑷ triple combination. Tumor tissues were collected after a 2-week treatment period. CD45+ immune cells were isolated from the tumors by magnetic cell separation (MACS) and subjected to scRNA-Seq using 10x Genomics pipelines. Bioinformatics data analysis was conducted with Clarivate Analytics. To evaluate the effects of E7386 on Treg differentiation, an in vitro-induced regulatory T cells (Tregs) differentiation assay was conducted. Naïve CD4+ T cells were isolated by MACS and plated under iTreg differentiation conditions (stimulation of TGF-β and IL-2) with or without treatment of E7386. Induced Tregs and conditional culture medium were collected for evaluation of Treg differentiation, including gene expression and protein analysis.
Results: CD45+ immune cells were clustered into 14 cell-type groups. Increased proportion of monocytes, NK cells, Tregs, CD4+ T cells, CD8+ T cells, eosinophils, and neutrophils were observed after LEN plus anti-PD-1 treatment. Among these subpopulations, Treg were most significantly suppressed by E7386 plus LEN plus anti-PD-1. Gene expression analysis revealed that the triple combination suppressed the activated gene expression of the Stat5/Foxp3 axis in CD4+ T cells, particularly Tregs, induced by LEN plus anti-PD-1 treatment. Consistently, the iTreg differentiation assay confirmed the suppressive function of E7386 on the Treg differentiation rate. Multiple subsequent in vitro assays also demonstrated the inhibitory effects of E7386 on TGF-β secretion and the expression levels of TGF-β downstream target genes.
Conclusion: In summary, these data suggest a suppressive role of E7386 on Treg differentiation, which leads to antitumor activity of E7386 in combination with lenvatinib and anti-PD-1 antibody in a preclinical tumor model.
Citation Format: Jialing Shen, Ryoga Ishida, Masahiko Kume, Takayuki Kimura, Yusuke Adachi, Yu Kato. E7386, a Wnt/β-catenin signaling modulator, suppresses the differentiation of regulatory T cells in combination with lenvatinib plus anti-PD-1 antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2022.