Abstract 2026: Single-cell RNA-sequencing analysis of tumor endothelial cells reveals suppression of specific endothelial subtypes by the combination treatment of Wnt/β-catenin signaling modulator E7386 plus lenvatinib
Authors: Kume Masahiko , Ishida Ryoga , Ozawa Yoichi , Shen Jialing , Konishi Hiroto , Kuronishi Megumi , Kimura Takayuki , Adachi Yusuke , Kato Yu 
Published: March 2024

Abstract
Background: Aberrant activation of Wnt/β-catenin signaling plays an important role in both carcinogenesis and modulation of the tumor microenvironment. E7386, a novel orally active antitumor agent, inhibits the interaction between β-catenin and CREB-binding protein (CBP) and thereby modulates Wnt/β-catenin signaling. We previously reported that E7386 in combination with lenvatinib (LEN), a multiple receptor tyrosine kinase inhibitor mainly targeting VEGFRs and FGFRs, showed a greater antitumor activity and reduction of tumor microvessels than each treatment alone in preclinical tumor models. Multiple clinical studies are in progress including the combination of E7386 plus LEN (NCT04008797). Here, we further tried to elucidate the mechanism underlying the antitumor and antiangiogenic effect of the combination of E7386 plus LEN by using single-cell RNA sequencing (scRNA-seq) of tumor endothelial cells (ECs).
Methods: Mice bearing subcutaneous RAG (mouse renal cell carcinoma cell line) tumors were treated with E7386 at 25 mg/kg and/or with LEN at 10 mg/kg by daily oral gavage for 8 days. Tumor ECs (CD31+/CD45−) were isolated by magnetic cell separation and flow cytometry and were subjected to scRNA-seq using 10x Genomics pipeline. Bioinformatics data analysis was conducted by Clarivate Analytics. After quality control and filtering, ECs were gated by their expression of pan-EC markers and were further classified into 9 subtypes (tip, capillary, arterial, venous, proliferating, immature, interferon, activated artery, and lymphatic) according to previously reported markers for each subtype.
Results: Among classified subtypes, proliferating and immature subtypes showed clear reduction in the percentage of total ECs with combination of E7386 plus LEN versus LEN monotherapy. In both proliferating and immature subtypes, a subset of Wnt/β-catenin downstream genes showed increased expression with LEN monotreatment. Conversely, these Wnt/β-catenin downstream genes were downregulated with the combination of E7386 plus LEN, suggesting that Wnt/β-catenin signaling may be associated with a drug resistance mechanism against LEN in these subtypes. Pathway analysis indicated that genes involved in cell proliferation and survival were downregulated by the E7386 plus LEN combination versus LEN monotreatment in both proliferating and immature subtypes.
Conclusion: Taken together, these results suggest a role for E7386 in suppressing the activation of Wnt/β-catenin signaling induced by LEN monotreatment in specific EC subtypes; this activity leads to enhanced antiangiogenic and antitumor activity with E7386 plus LEN combination therapy in a preclinical tumor model.
Citation Format: Masahiko Kume, Ryoga Ishida, Yoichi Ozawa, Jialing Shen, Hiroto Konishi, Megumi Kuronishi, Takayuki Kimura, Yusuke Adachi, Yu Kato. Single-cell RNA-sequencing analysis of tumor endothelial cells reveals suppression of specific endothelial subtypes by the combination treatment of Wnt/β-catenin signaling modulator E7386 plus lenvatinib [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 2026.