PCNA and acute lymphoblastic leukemia: Exo-CM from ALL cell lines (JM1 and SUP-B15) were added to JM1 cells and proliferative (Ki-67, PCNA), pro-survival (MCL1, BCL2) and pro-apoptotic (BAD, BAX) genes were analyzed by mRNA expression at two time points (6 and 24 h).