Relationship between gene expression before treatment and sensitivity to fludarabine in CLL patients. Expression levels of the targets were investigated by RT-qPCR and normalized to both housekeeping genes. The average expression level in sensitive patients was used as calibrator. Expression levels presented as mean values ±SEM were investigated on two groups of CLL patients; eighteen patients in vivo (8S and 10R) and twenty-one patients in vitro (16S and 5R). Statistical analysis was performed by 2-sided t-test and levels were considered to be significantly different when p values were lower than 0.05. A and B. The expression of MYC and SULF2 was measured in CLL B cells of patients before their treatment with fludarabine in vivo (A) and in vitro (B). C and D. The expression of miR-29a, miR-181a, and miR-221 was investigated in CLL B cells of patients before their treatment with fludarabine in vivo (C) and in vitro (D).