In B-cell chronic lymphocytic leukemia (CLL), Rai stage, immunoglobulin gene 
mutational status, chromosomal abnormalities, CD38 and ZAP-70 expression were 
used as prognostic markers. In this study, to understand the molecular basis of 
chromosomal abnormalities leading to tumor progression, 90 CLL patients were 
grouped into poor prognosis (with 11q deletion and trisomy 12) and good 
prognosis (with normal karyotype and 13q deletion) and their clinical outcome 
was assessed. Gene expression profiles of 35 CLL samples with poor outcome (11q 
deletion, n=9; trisomy 12, n=5) and good outcome (13q deletion, n=13; normal 
karyotype, n=8) were analyzed using oligonucleotide microarray. Significance 
analysis of microarray (SAM) identified 27 differentially expressed genes 
between these two subgroups with significant overexpression of ATF5 and 
underexpression of CDC16, PCDH8, SLAM, MNDA and ATF2 in CLL patients with poor 
outcome. ATF5 gene expression in CLL was further studied because of its role in 
the regulation of cell cycle progression/differentiation and apoptosis. The 
overexpression of ATF5 was confirmed by real-time PCR using 39 CLL samples from 
the poor and good outcome groups. ATF5 was significantly (p<0.001) overexpressed 
in the poor outcome group. Furthermore, ATF5 expression was significantly higher 
in the 11q deletion as well as trisomy 12 group alone compared to the 13q 
deletion and normal karyotype groups. ATF5 overexpression was also associated 
with significantly (p=0.04) shorter time to treatment. Similarly, expression of 
five underexpressed genes also correlated with longer time to treatment. Thus, 
this report demonstrates that ATF5 may be one of the key genes involved in 
increased proliferation and survival in 11q deletion or trisomy 12, whereas 
CD16, CD86, SLAM, MNDA and ATF2 may be involved in the decreased proliferation 
of CLL cells with 13q deletion or normal karyotype.