SIRT6 deficiency impairs the deacetylation and ubiquitination of UHRF1 to strengthen glycolysis and lactate secretion in bladder cancer

Background: Aberrant interplay between epigenetic reprogramming and metabolic rewiring events contributes to bladder cancer progression and metastasis. How the deacetylase Sirtuin-6 (SIRT6) regulates glycolysis and lactate secretion in bladder cancer remains poorly defined. We thus aimed to study the biological functions of SIRT6 in bladder cancer.

Methods: Bioinformatic analysis was used to study the prognostic significance of SIRT6/UHRF1 in BLCA. Both in vitro and in vivo assays were used to determine the roles of SIRT6/UHRF1 in BLCA. Deacetylation and ubiquitin assays were performed to uncover the regulations of SIRT6-UHRF1. Measurement of extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) was used to assess glycolytic abilities.

Results: Here, we show that protein deacetylase SIRT6 was down-regulated in BLCA, and predicts poor overall survival. SIRT6 deficiency notably enhances BLCA cell proliferation, self-renewal, and migration capacities in vitro and in vivo. Mechanistically, SIRT6 interacts with, deacetylates, and promotes UHRF1 degradation mediated by β-TrCP1. Thus, SIRT6 deficiency leads to stabilized UHRF1 and depends on UHRF1 to accelerate BLCA malignant progression. Furthermore, UHRF1 significantly increased aerobic glycolysis via activating MCT4/HK2 expressions. Down-regulated SIRT6 thus depended on UHRF1 to promote glycolysis and lactate secretion in BLCA. Targeting UHRF1 or MCT4 notably impaired the extracellular lactate accumulations in BLCA. Significantly, a specific small-molecule inhibitor (NSC232003) targeting UHRF1 substantially inhibited SIRT6-deficient BLCA progression.

Conclusion: Together, our study uncovered an epigenetic mechanism of the SIRT6/UHRF1 axis in driving BLCA glycolysis and lactate secretion, creating a novel vulnerability for BLCA treatment.