TERT Core Promotor Mutations in Early-Onset Bladder Cancer

Activating mutations in the core promoter of the TERT gene have been described in many different tumor entities. In vitro models showed a two- to fourfold increase in transcriptional activity of the TERT promoter through creation of a consensus binding motif for Ets/TCF transcription factors caused by these mutations. TERT core promoter mutations are the most common mutations in bladder cancer with a frequency between 55.6% and 82.8% described so far, and are independent of stage and grade. Since limited data on molecular alterations of early-onset bladder tumors exists, we assessed the frequency of TERT core promoter mutations in early-onset bladder cancer. Two cohorts of bladder tumors (early-onset patient group; n=144 (age of onset of disease ≤45 years); unselected, consecutive group; n=125) were examined for TERT core promoter mutations. After microdissection and extraction of DNA the corresponding hotspot regions in the TERT core promoter were examined by Sanger-sequencing or a SNaPshot approach. A significantly lower frequency of TERT core promoter mutations was found in tumors from the early-onset cohort compared to the consecutive cohort (57.6% vs. 84.8%, p<0.001). Among the early-onset cohort cases younger than the cohort's median age of 39 years at disease onset showed a significantly reduced number of TERT promoter mutations (31/67, 46,3%) than cases aged between 39 and 45 years (52/77, 67.5%; p=0.012). This association was not found in the consecutive cases. Mutation status was independent of tumor stage and grade. We conclude that in tumors from early-onset bladder cancer patients TERT core promoter mutations are not as frequent as in bladder tumors from consecutive cases, but seem to play an important role there as well. In patients below 39 years of age TERT core promoter mutations are a more infrequent event, suggesting different mechanisms of tumorigenesis in these young patients.