ATM, CTLA4, MNDA, and HEM1 in high versus low CD38 -: Expressing B-cell chronic lymphocytic leukemia

Purpose: In B-cell chronic lymphocytic leukemia (CLL), high CD38 expression has been associated with unfavorable clinical course, advanced disease, resistance to therapy, shorter time to first treatment, and shorter survival. However, the genes associated with CLL patient subgroups with high and low CD38 expression and their potential role in disease progression is not known. Experimental Design: To identify the genes associated with the clinical disparity in CLL patients with high versus low CD38 expression, transcriptional profiles were obtained from CLL cells from 39 different patients using oligonucleotide microarray. Gene expression was also compared between CLL cells and B cells from healthy individuals. Results: Gene expression analysis identified 76 differentially expressed genes in CD38 high versus low groups. Out of these genes, HEMI, CTLA4, and MNDA were selected for further studies and their differential expression was confirmed by real-time PCR. HEM1 overexpression was associated with poor outcome, whereas the overexpression of CTLA4 and MNDA was associated with good outcome. Down-regulation of HEM1 expression in patient CLL cells resulted in a significant increase in their susceptibility to fludarabine-mediated killing. In addition, when gene expression patterns in CD38 high and low CLL cells were compared with normal B-cell profiles, ATM expression was found to be significantly lower in CD38 high compared with CD38 low CLL as confirmed by real-time reverse transcription- PCR. Conclusions: These results identify the possible genes that may be involved in cell proliferation and survival and, thus, determining the clinical behavior of CLL patients expressing high or low CD38.