Induction of MYC protein after sIgM stimulation in CLL samples. (A,C) CLL samples were incubated with anti-IgM for 3 or 6 hours or for 6 hours with the isotype control antibody (IC). Expression of MYC and MAX protein was analyzed by immunoblotting. Results shown are representative of those obtained from analysis of 18 intracellular Ca²⁺-responsive (A) and 9 intracellular Ca²⁺ nonresponsive (C) CLL samples. MAX expression demonstrates equal loading of protein samples. (B,D) Quantitation of the fold increase in MYC protein expression (relative to isotype-control treated cells; C) measured by densitometry analysis of immunoblots at 3 or 6 hours after stimulation with anti-IgM for intracellular Ca²⁺-responsive (B) and -nonresponsive (D) samples. Graphs show data for individual samples, and any statistically significant differences (Student matched paired t test) between control and anti-IgM–stimulated cells (NS indicates not significant, P > .05). (E) Comparison between MYC induction (> 20% increase compared with control cells) and positive (□) and negative (■) intracellular Ca²⁺ responses (Fisher exact test) in anti-IgM–treated CLL samples (n = 27).