Mantle cell lymphoma (MCL) accumulates in lymphoid organs but disseminates early on in extranodal tissues. Although proliferation remains located in lymphoid organs only, suggesting a major role of the tumor ecosystem, few studies have assessed MCL microenvironment. We therefore cocultured primary circulating MCL cells from 21 patients several weeks ex vivo with stromal or lymphoid-like (CD40L) cells to determine which interactions could support proliferation of MCL cells. We showed that coculture with lymphoid-like cells, but not stromal cells, induced cell-cycle progression, which was amplified by MCL-specific cytokines (IGF-1, BAFF, IL-6, IL-10). Of interest, we showed that our model recapitulated the MCL in situ molecular signatures i.e., proliferation, NFkB and survival signatures. We further demonstrated that proliferating MCL harbored an imbalance in Bcl-2 family expression leading to a consequent loss of mitochondrial priming. Interestingly, this loss of priming was overcome by the Type II anti-CD20 antibody obinutuzumab, which counteracted Bcl-xL induction through NFkB inhibition. Finally, we showed that the mitochondrial priming directly correlated with the sensitivity toward venetoclax and alkylating drugs. By identifying the microenvironment as the major support for proliferation and drug resistance in MCL, our results highlight a selective approach to target the lymphoma niche.
Overall design: MCL cells were amplified and RNA were prepared from exponentially growing cells. RNA was extracted using the RNeasy Kit (Qiagen, Hilden, Germany). Biotinylated cRNA was amplified with a double in vitro transcription and hybridized to the human U133 2.0 plus GeneChips, according to the manu- facturer’s instructions (Affymetrix, Santa Clara, CA, USA). Fluorescence intensities were quantified and analyzed using the GECOS software (Affymetrix).
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