Methynissolin confers protection against gastric carcinoma via targeting RIPK2

Abstract

Gastric carcinoma (GC) is one of the most common malignant tumors worldwide, and ranks fifth in incidence and top 5 in tumor-associated mortality. Unfortunately, the molecular mechanisms contributing to GC development are still unclear, urgently requiring more studies. It has been proposed that the multifunctional regulator receptor-interacting protein 2 (RIPK2) is both a regulator that induces stomach cancer and its complications such as cachexia. However, the potential molecular function of RIPK2 on regulation of GC is largely unknown. Moreover, 3,9-di-O-methylnissolin, a flavonoid derived from the roots of Astragalus membranaceus, exhibits protective effects against cancer, inflammation, and bacterial infections. Unfortunately the antineoplastic mechanism of oral exposure of such flavonoid are poorly understood. It remains unknown whether 3,9-di-O-methylnissolin is capable of mitigating GC progression, and potential molecular mechanism. This study aims to provide mechanistic evidence that the 3,9-di-O-methylnissolin-triggered mitigation of GC by repressing RIPK2 activity and its downstream ASK1 signaling. The TCGA database, GEO database, subjects with GC phenotype and GC cell lines were used in this work. 3,9-di-O-methylnissolin intervention reduces stomach cancer cell migration, proliferation and invasion in vitro. Also, 3,9-di-O-methylnissolin confers protection against tumor growth in xenograft model in vivo. Mechanistically, on the other hand, in the para-carcinoma tissue, overexpression of RIPK2 reduces lipogenesis and disturbs lipid homeostasis. Overexpression of RIPK2 activates downstream signaling of ASK1, which in turn downregulates PPARα, a master regulator of lipid metabolism. This process results in lower lipogenesis and downregulation of a set of PPARα target genes. Astragalus membranaceus naturally produces 3,9-di-O-methylnissolin, a bioactive substance that when suppression of ASK1 by methylnissolin reduces RIPK2-induced GC and its related cachexia and restores lipid homeostasis. These findings offer important new understandings of stomach cancer and could aid in the development of treatment plans for gastric carcinoma and cachexia related to cancer.