Clinical and Biological Relevance of NF-κB Activation in B-CLL.

Based on previous observations, we postulate that the molecular and clinical variability of Chronic Lymphocytic Leukemia (CLL) could reflect differences in the degree of NF-κB activation. To test this hypothesis, the expression profile (mRNA and protein expression) of a series of 41 B-CLL cases with lymph node involvement was analyzed at the same time, with a cDNA microarray (OncoChip, 7K clones) and an oligo microarray (Human 1A Agilent, 22K sequences). Results were correlated with the IgV_H mutational status, ZAP-70 expression, clinical outcome and NF-κB activation status, as determined by EMSA and phosphorylated IκBα (p-IκBα) detection by Western Blotting. The study showed a correlation between the presence of a surrogate marker of NF-κB activation, p-IκBα, and changes in the degree of NF-κB activation, as determined by EMSA. NF-κB activation was associated with the expression of 2200 and 894 genes using the oligo and cDNA microarray platforms respectively. These sets of genes comprise key genes involved in the control of B-cell receptor signaling, signal transduction and apoptosis, including SYK, LYN, BCL2, CCR7, BTK, PIK3CD, BAFF. Cases with higher levels of NF-κB activation showed longer overall survival than cases with lower activation. A Cox regression model was derived to analyze variables of potential prognostic interest in this series: IgV_H mutational status, ZAP-70 and p-IκBα expression. The multivariate analysis disclosed p-IκBα and ZAP-70 expression as independent prognostic factors related with overall survival. In conclusion, a variable degree of activation of NF-κB, as determined by the expression of p-IκBα and EMSA, is a relevant event in CLL, associated with changes in the survival probability, and correlated with the expression of a large set of genes identified by two different microarray platforms.