Inhibition of O-GlcNAcase sensitizes apoptosis and reverses bortezomib resistance in mantle cell lymphoma through modification of truncated Bid

Aberrant energy metabolism represents a hallmark of cancer and contributes to numerous aggressive behaviors of cancer cells, including cell death and survival. Despite the poor prognosis of mantle cell lymphoma (MCL), due to the inevitable development of drug resistance, metabolic reprograming of MCL cells remains an unexplored area. Post-translational modification of proteins via O-GlcNAcylation is an ideal sensor for nutritional changes mediated by O-GlcNAc transferase (OGT) and is removed by O-GlcNAcase (OGA). Using various small molecule inhibitors of OGT and OGA, we found for the first time that O-GlcNAcylation potentiates MCL response to bortezomib (BTZ). CRISPR interference of MGEA5 (encoding OGA) validated the apoptosis sensitization by O-GlcNAcylation and OGA inhibition. To identify the potential clinical candidates, we tested MCL response to drug-like OGA inhibitor, ketoconazole (KCZ), and verified that it exerts similar sensitizing effect on BTZ-induced apoptosis. Investigations into the underlying molecular mechanisms reveal that BTZ and KCZ act in concert to cause the accumulation of truncated Bid (tBid). Not only does KCZ potentiate tBid induction, but also increases tBid stability through O-GlcNAcylation that interferes with tBid ubiquitination and proteasomal degradation. Remarkably, KCZ strongly enhances BTZ-induced apoptosis in de novo BTZ-resistant MCL cells and in patient-derived primary cells with minimal cytotoxic effect on normal peripheral blood mononuclear cells and hepatocytes, suggesting its potential utility as a safe and effective adjuvant for MCL. Together, our findings provide novel evidence that combination of BTZ and KCZ or other OGA inhibitors may present a promising strategy for the treatment of drug-resistant MCL.

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