Abstract 2150: Oncogenic role of GAEC1 and its potential modulation with p53 in pathogenesis of colon cancer

Abstract

Abstract Introduction: GAEC1 (Gene amplified in esophageal cancer 1), is frequently amplified and overexpressed in colon cancer tissues. In the present study, we aimed to unveil the oncogenic potential of GAEC1 in carcinogenesis of colon cancer by studying the underlying cellular functions and molecular interactions by in vitro and in vivo experiments. Method: Transient overexpression of GAEC1 with pcDNA3.1-GAEC1 and silencing with GAEC1-siRNA was performed and several downstream assays were done such as migration, clonogenic and apoptotic assay. Analysis of cell kinetics was done using flow cytometry and cell counting kit-8 was used for cell proliferation assay. Immunofluorescence and Western blot assay were used to determine the expression of different target proteins. Co-immunoprecipitation was used to confirm the protein-protein interaction. For xenotransplantation the severely combined immunodeficient (SCID) mice (4 groups, 6 in each group) were injected subcutaneously with GAEC1 shRNA and control shRNA transfected (stable) SW480 and SW48 colon cancer cells. Result: The overexpression of GAEC1 increased cell proliferation, migration, reduced apoptosis in colon cancer cells. Also, these cells showed cell cycle arrest at the synthetic phase, activation of Bcl-2, K-ras, pAKT proteins as well as inhibition of p53, PUMA, p21 and BAX proteins. Conversely, knockdown of GAEC1 reduced cell proliferation, migration, decreased the phosphorylation of AKT, and induced apoptosis, G2/M phase arrest and cleavage of poly (ADP-ribose) polymerase (PARP). Co-immunoprecipitation revealed GAEC1’s interaction with p53. In addition ectopic over expression and silencing of GAEC1 lead to reciprocal effects of p53 protein expression. Moreover, knockdown of GAEC1 reduced the nuclear translocation of murine double minute 2 protein (mdm2) indicating that GAEC1 is responsible for the degradation of p53 through the direct interaction between mdm2-p53 in nucleus. Furthermore, our in vivo data demonstrate that the loss of GAEC1 inhibits the tumor formation in xenograft model. Conclusion: Collectively our study demonstrates that GAEC1 exhibits the oncogenic role in colon cancer by reducing expression of p53 through protein-protein interaction which leads to the inhibition of PUMA, p21, BAX, and activation of Bcl-2, K-ras and pAKT protein expression. Note: This abstract was not presented at the meeting. Citation Format: Riajul Wahab, Farhadul Islam, Vinod Gopalan, Alfred King-Yin Lam. Oncogenic role of GAEC1 and its potential modulation with p53 in pathogenesis of colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2150. doi:10.1158/1538-7445.AM2017-2150