GSE106716
SYK activity modulates the EGFR-dependent transcriptome
Background: Among all gynecologic malignancies, epithelial ovarian cancer has the highest case-to-fatality ratio. Most patients are diagnosed at advanced stages and recurrence is common and accounts for disease-related mortality. Spleen tyrosine kinase (SYK) is an emerging cancer-associated kinase upregulated in recurrent tumors and is amenable for inhibition using small compounds that have been studied in clinical trials for autoimmune diseases. Our previous proteomic analysis identified several novel SYK substrates including EGFR and ERBB2. Here, we investigated the cross-talk between these pathways in ovarian carcinomas. Methods: Immunohistochemistry and immunoblotting were utilized to assess SYK and EGFR phosphorylation in ovarian serous carcinomas. Association with survival was determined by Kaplan-Meier analysis and the log-rank test. To study its role in EGFR signaling, SYK activity was modulated using a small molecule inhibitor, a syngeneic knockout, and an active kinase inducible system. We applied RNA-seq to investigate the SYK-regulated EGF-induced transcriptome. Results: Intense immunoreactivity of active pSYK(Y525/526) correlated with poor overall survival in two independent ovarian cancer cohorts. SYK directly phosphorylated EGFR and ERBB2, while knockout of SYK reduces their phosphorylation. Phosphorylation levels of SYK(Y525/526) positively correlated with EGFR(Y1187) and STAT3(Y705). Active SYK reduced sensitivity to the EGFR/ERBB2 inhibitor, lapatinib, and SYK non-phosphorylatable EGFR mutant was more sensitive to paclitaxel. SYK modulated the EGF-induced transcriptome, supporting its involvement in EGFR/ERBB2-regulated transcriptional activity. Conclusions: Our findings suggest an upstream role of SYK in regulating the EGFR/ERBB2 signaling, and provide a biological rationale for targeting SYK in ovarian cancer therapy. Overall design: RNA-seq on wildtype and SYK KO cells with no treatment or treated with EGF (50 ng/ml) for 24 h