Abstract LB_C18: A novel WNT-RIP1 signaling pathway promotes colorectal cancer metastasis via induction of EMT

Abstract

Abstract We identified new potential roles of RIP1 (receptor-interacting protein kinase 1) in controlling WNT signaling to enhance metastasis of colorectal cancer (CRC). First, we showed that WNT3A treatment sequentially increased the expression of RIP1 and β-catenin. Next, Immunohistochemical analyses of human CRC tissue arrays consisting of normal, primary, and metastatic cancers showed that elevated RIP1 expression might be related to β-catenin expression and it also indicated inductions of carcinogenesis and metastasis. In in vivo experiments with mice, intravenous injection of RIP1 over-expressed CRC cells has demonstrated that RIP1 may promote metastasis. These results implied RIP1 might be major component of WNT signaling. Next, we performed immunoprecipitation (IP) to revealed intracellular signaling mechanism that WNT3A treatment could induce direct binding between RIP1 and β-catenin, and observed direct binding and stabilization of the β-catenin protein via regulation of RIP1 ubiquitination by a downregulation of the E3 ligase, cIAP1/2. Down-regulation of cIAP1/2 expression with siRNA treatment and inhibition of its ubiquitinase activity with pharmacological inhibitor treatment could enhance WNT3A-induced RIP1 and β-catenin protein expression and binding. These results also enhance the migration and invasion of CRC cells in vitro via induction of endothelial-mesenchymal transition (EMT). The in vitro binding assay and IP of exogenous RIP1-containing CRC cells additionally result in the direct binding of RIP1 and β-catenin. The enhanced RIP1 expression can destroy the β-catenin–β-TrCP complex. Additionally, we also identified GDF15 (Growth and differentiation factor 15) is located at down-stream of WNT3A-RIP1 pathway and involved in EM induction. Taken together, these results suggest an identification of novel WNT-RIP1 pathway to enhance EMT and suggest GDF15 also might contribute CRC malignancy. Citation Format: A-RAM KANG, DO HOON KIM, JONG KUK PARK. A novel WNT-RIP1 signaling pathway promotes colorectal cancer metastasis via induction of EMT [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_C18.