Loss of RNF43 Function Contributes to Gastric Carcinogenesis by Impairing DNA Damage Response

Abstract

Background & Aims RING finger protein 43 (RNF43) is a tumor suppressor that frequently is mutated in gastric tumors. The link between RNF43 and modulation of Wingless-related integration site (WNT) signaling has not been shown clearly in the stomach. Because mutations in RNF43 are highly enriched in microsatellite-unstable gastric tumors, which show defects in DNA damage response (DDR), we investigated whether RNF43 is involved in DDR in the stomach. Methods DDR activation and cell viability upon γ-radiation was analyzed in gastric cells where expression of RNF43 was depleted. Response to chemotherapeutic agents 5-fluorouracil and cisplatin was analyzed in gastric cancer cell lines and xenograft tumors. In addition, involvement of RNF43 in DDR activation was analyzed upon Helicobacter pylori infection in wild-type and Rnf43 ΔEx8 mice. Furthermore, a cohort of human gastric biopsy specimens was analyzed for RNF43 expression and mutation status as well as for activation of DDR. Results RNF43 depletion conferred resistance to γ-radiation and chemotherapy by dampening the activation of DDR, thereby preventing apoptosis in gastric cells. Upon Helicobacter pylori infection, RNF43 loss of function reduced activation of DDR and apoptosis. Furthermore, RNF43 expression correlated with DDR activation in human gastric biopsy specimens, and RNF43 mutations found in gastric tumors conferred resistance to DNA damage. When exploring the molecular mechanisms behind these findings, a direct interaction between RNF43 and phosphorylated H2A histone family member X (γH2AX) was observed. Conclusions We identified a novel function for RNF43 in the stomach as a regulator of DDR. Loss of RNF43 function in gastric cells confers resistance to DNA damage-inducing radiotherapy and chemotherapy, suggesting RNF43 as a possible biomarker for therapy selection.

WNT inhibition creates a BRCA‐like state in Wnt‐addicted cancer

“…In cancer, WNT16B is a driver of resistance to cytotoxic chemotherapy in prostate cancer (Sun et al , 2012), PARP1 is high in colorectal cancer (Dörsam et al , 2018), and WNT3A expression is a cause of in vitro olaparib resistance in an ovarian cancer cell line (Yamamoto et al , 2019). Most recently, mutational inactivation of RNF43 in gastric cancers was found to induce resistance to DNA damage (Neumeyer et al , 2020). Further, we find that treatment of mice with Wnt secretion inhibitors reduced the expression of both Mybl2 and DNA repair genes in the intestinal crypts.…”

Genomic Profiling Reveals the Molecular Landscape of Gastrointestinal Tract Cancers in Chinese Patients

“…As a tumor suppressor, RNF43 has shown its capacity to negatively regulate Wnt signaling (Koo et al, 2012;Loregger et al, 2015). Recent studies found that depletion of RNF43 enhanced tumor growth in GI cancers and conferred resistance to DNA-damageinducing chemotherapies and γ-radiation in gastric cancer cells (Neumeyer et al, 2019(Neumeyer et al, , 2020. Additionally, preclinical cancer models have shown the responsiveness of RNF43 mutations to Wnt inhibitors, several of which are in clinical trials (Janku et al, 2015(Janku et al, , 2020Yu et al, 2020).…”

Manifold role of ubiquitin in Helicobacter pylori infection and gastric cancer

“…Furthermore, infected mutant mice developed atrophy, hyperplasia and mucin 2 expressing metaplasia [ 135 ]. In AGS and MKN45 cells, RNF43 depletion mitigated the DNA damage response and apoptosis induced by H. pylori -infection, γ-radiation, 5-fluorouracil and cisplatin [ 136 ]. Further investigations concerning the RNF43 substrates are required to show specificity of this E3 ubiquitin ligase and, thus, to explore its therapeutic potential.…”