TNF and leukemia: When B-ALL cells were cultured in unconditioned medium or SCM, the total number of leukemia cells increased by 6 to 10-fold over 3 days; whereas, all of the B-ALL cell lines cultured in ACM or recombinant TNF-α (a component of ACM) exhibited a 2 to 4-fold increase in density over the same period (Fig. 2b and Supplementary Fig. 1d).