CD40L⁺ but not mesenchymal cells support primary MCL cell proliferation ex vivo. (A) Whole transcriptome sequencing analysis of mRNA abundance (RPKM) of MKI67 (Ki67 gene) in cyclinD1⁺ primary MCL cells from LO, CD19⁺ PB B cells (PBC)s from 2 healthy volunteers, and JEKO-1, as previously described.⁵⁴  (B) Cell distribution in the different cell-cycle phases (%) for 1 proliferating cell line (JeKo-1), 5 primary PB MCL samples, and CD5⁺ CBBCs (healthy donor). The results are detailed in supplemental Figure 1B. (C) qRT-PCR analysis of the MKI67 gene in primary cells concomitantly isolated from LO and PB for 2 MCL patients. Pt, patient. (D) BrdU/propidium iodide staining of primary MCL cells (n = 5) in the presence of hMSC or L-40L coculture layer and cytokines for 7 days as indicated; paired Student t test. (E) BrdU/propidium iodide staining of primary MCL cells (n = 9) in the presence of L-40L coculture layer with or without cytokines for 7 days as indicated; paired Student t test. (F) Left (n = 9): cell-cycle analysis (% of BrdU⁺ cells) of primary MCL cells for the time and condition indicated; Student t test. Right (n = 5): total number of live cells is represented as fold increase from input on day 0; Student t test. n.s., not significant. *P < .05, **P < .01, ****P < .0001.