Baseline gene expression of BCL2 family members and correlation to IC₅₀.BCL2, BCL2L1, MCL1, and BCL2L11 were measured in 20 patient samples, 4 cell lines, and 3 healthy controls. Results are expressed as a fraction of the mean of the healthy controls. (A) Baseline expression of BCL2 was found to differ significantly between high responders and low responders. No difference was found between low responders and cell lines. BCL2L1 was expressed similarly among all 4 groups. Decreased MCL1 expression was noted in cell lines compared with patient samples. (B) BCL2 mRNA expression may predict response to venetoclax in vitro, with higher expression correlating to increased sensitivity. (C) Increased ratios of expression of BCL2 to BCL2L1 predicts higher sensitivity to venetoclax.