Association of Histone H3 Trimethylation in Circulating Monocytes with Lack of Early Recurrence in Patients with Bladder Cancer following BCG Induction Therapy

BACKGROUND: The mode of action of Bacillus Calmette-Guerin (BCG) in the treatment of patients with non-muscle invasive bladder cancer (NMIBC) is incompletely understood, but recent studies support an association between BCG-induced trained immunity in circulating monocytes and disease-free survival. OBJECTIVE: We compared epigenetic profiles in monocytes from NMIBC patients with early disease recurrence with those from recurrence-free patients. METHODS: We conducted chromatin immunoprecipitation and DNA sequencing (ChIP-seq) on monocytes from seven patients treated with BCG (four with early recurrences and three recurrence-free after one year) to determine genome-wide distribution and abundance of histone 3 lysine 4 trimethylation (H3K4me3) prior to and after five weeks of induction therapy. RESULTS: Genome-wide H3K4me3 profiles before or after BCG induction distinguished patients with early recurrences from those remaining recurrence-free. Furthermore, H3K4me3 levels at genes involved in specific pathways were increased in the recurrence-free group. Independent quantification showed increased H3K4me3 levels in elements of the Wnt and AMPK signaling pathways in the recurrence-free group before BCG initiation, while elements of the MAPK showed increased levels after five weeks of induction in the same group. Validation of these genes on an independent cohort of four additional patients that remained recurrence-free after one year and three with early recurrences revealed consistent increases in H3K4me3 levels associated with MAPK pathway genes after five weeks of BCG treatment in the recurrence-free group. CONCLUSIONS: Recurrence-free survival following BCG immunotherapy for NMIBC is associated with the accumulation of H3K4me3 at specific gene loci, and could lead to identification of prognostic biomarkers.