Effects of FBXW7 mutations in serous endometrial cancers: increased levels of potentially druggable proteins and in vitro sensitivity to SI-2 and dinaciclib
Wednesday, September 12, 2018 — Poster Session I
- ME Urick
- DW Bell
Women with clinically aggressive endometrial cancers (ECs) have frequently acquired genomic alterations that affect the FBXW7 (F-box and WD repeat domain-containing 7) tumor suppressor gene. Specifically, somatic FBXW7 mutations have been reported in 17-30% of serous ECs, 11-28% of uterine carcinosarcomas, and 7-25% of clear cell ECs. Despite these high frequencies, the molecular effects of mutated FBXW7 in ECs have not been determined. To this end, we used transient transfection and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) editing to introduce recurrent somatic FBXW7 mutations into serous EC cells and studied altered protein levels resulting from these mutations using Western blotting. We determined the sensitivity of CRIPSR-edited FBXW7-mutant serous EC cells to targeted inhibitors using cell viability assays as well as the molecular and cellular effects of the inhibitors using Western blotting, apoptosis assays and flow cytometry. FBXW7 mutations resulted in increased Cyclin E1, steroid receptor coactivator 3 (SRC-3), c-MYC, Rictor, glycogen synthase kinase 3 (GSK3), P70S6 kinase, and protein kinase B (AKT) phosphorylated protein levels. CRISPR-edited FBXW7-mutant serous EC cells exhibited significantly decreased viability in response to SI-2 (a SRC inhibitor) and dinaciclib (a cyclin dependent kinase (CDK) inhibitor) compared to parental cells. Along with decreased viability, these targeted inhibitors induced significant changes in cell cycle distribution and/or increased apoptosis in CRISPR-edited FBXW7-mutant serous EC cells compared to parental cells. These results provide the first direct biochemical evidence that FBXW7 mutations in EC cells cause increased levels of potentially druggable proteins and increased in vitro sensitivity to targeted agents.
Category: Genetics and Genomics