Proteomic Changes Associated With Endogenous FBXW7 Mutations in Moderately Differentiated Endometrial Cancer Cells Include Increased TROP2 and Galectin-3 Levels

Background Endometrial cancer (EC) is the fourth most commonly diagnosed cancer among women in the US and the fifth leading cause of cancer death in this population. The FBXW7 tumor suppressor gene is frequently mutated in all molecular subtypes of EC. The encoded protein is part of a ubiquitin ligase complex that targets substrate proteins for ubiquitination and, in most instances, proteasome-mediated degradation. Aims The purpose of this investigation was to identify the proteomic changes associated with endogenous FBXW7 mutations in EC. Materials & Methods Quantitative LC-MS/MS was used to identify significant (p < 0.05) differences in the proteomes and phosphoproteomes of two FBXW7-mutated EC cell lines, HEC-1-B(FBXW7-R367X )and JHUEM-1(FBXW7-R505C), as compared to isogenic mutation-corrected cell lines. Western blotting was performed to orthogonally validate a subset of protein changes. Results Analysis of LC-MS/MS results identified 397 total proteins and/or phosphoproteins with significantly different levels in both HEC-1-BFBXW7-R367X and JHUEM-1FBXW7-R505C, as compared to isogenic mutation-corrected cell lines. This protein set included increased levels of TROP2, galectin-3, ASS1, and PLCG2 in both HEC-1-BFBXW7-R367X and JHUEM-1(FBXW7-R505C) cells; these perturbations orthogonally validated by western blotting. Conclusion This study provides novel insights into the proteomic and phosphoproteomic effects of the endogenous FBXW7-(R367X) and FBXW7-(R505C) mutations in EC cells, including increased levels of galectin-3, a potentially druggable target, and of TROP2, which is a druggable target in EC.