Comprehensive Landscape of Cyclin Pathway Gene Alterations and Co-occurrence with FGF/FGFR Aberrations Across Urinary Tract Tumors

Background: Cyclin pathway gene alterations are frequent in urothelial tumors and may co-exist with other important aberrations, leading to therapeutic opportunities. We characterized the landscape of cyclin gene alterations in urothelial and non-urothelial urinary tract (UT) malignancies.

Patients and methods: Overall, 6842 urothelial and 897 non-urothelial UT cancers were analyzed (hybrid-capture-based comprehensive genomic profile (Foundation Medicine)). Alteration frequency in cyclin-sensitizing and -resistance genes, and co-occurrence with fibroblast growth factor receptor (FGFR) gene abnormalities were evaluated.

Results: Cyclin-activating gene alterations were detected in 47.3% of urothelial and 37.9% of non-urothelial UT cancers. Frequency varied by histology and tumor site. CDKN2A and CDKN2B loss were the most frequent alterations in urothelial tumors (present in 38.5% and 30.4% of patients, respectively). Both genes were less frequently altered in adenocarcinomas (15.2% and 8.9%), but commonly altered in squamous cell carcinomas (74.4% and 39%). Tumors of neuroendocrine origin were relatively silent in activating cyclin alterations, but frequently displayed Rb1 alterations (86% and 83.7% of neuroendocrines and small cell carcinomas). Urachal tumors (n = 79) presented a distinct landscape of cyclin alterations relative to other UT cancers, with less frequent alterations overall. FGF/FGFR genes were altered in 34.9% of urothelial (22.1% in FGFR3), and 19.4% of non-urothelial urinary tract tumors (6.8% FGFR3). Cyclin-activating alterations frequently co-occurred with FGF/FGFR alterations but were in general mutually exclusively with cyclin resistance alterations (RB1/CCNE1).

Conclusions: Cyclin pathway activating alterations are common in urinary tract tumors, but frequency varies with histology and tumors sites. Co-occurrence of cyclin and FGFR pathway alterations may inform therapeutic opportunities.