Downregulation of rRNA synthesis by BCL-2 induces chemoresistance in diffuse large B cell lymphoma.

Overexpression of the antiapoptotic oncogene BCL-2 predicts poor prognosis in diffuse large B cell lymphoma (DLBCL) treated with anthracycline-based chemoimmunotherapy. Anthracyclines exert antitumor effects by multiple mechanisms including inhibition of ribosome biogenesis (RiBi) through rRNA synthesis blockade. RiBi inhibitors induce p53 stabilization through the ribosomal proteins-MDM2-p53 pathway, with stabilized p53 levels depending on baseline rRNA synthesis rate. We found that the BH3-mimetic venetoclax could not fully reverse BCL-2-mediated resistance to RiBi inhibitors in DLBCL cells. BCL-2 overexpression was associated with decreased baseline rRNA synthesis rate, attenuating p53 stabilization by RiBi inhibitors. Drugs stabilizing p53 irrespective of RiBi inhibition reversed BCL-2-induced resistance in vitro and in vivo, restoring p53 activation and apoptosis. A small nucleolar size, indicative of low baseline rRNA synthesis, correlated with high BCL-2 levels and poor outcomes in DLBCL patients. These findings uncover alternative BCL-2-dependent chemoresistance mechanisms, providing a rationale for specific combination strategies in BCL-2 positive lymphomas.