High-Resolution Genomic Profiling of Chronic Lymphocytic Leukemia Reveals New Recurrent Genomic Alterations

To identify genomic alterations in chronic lymphocytic leukemia (CLL), we performed single-nucleotide polymorphism (SNP)-array analysis on 353 samples from previously untreated patients entered on the CLL8 treatment trial. Based on paired-sample analysis (n=147), a mean of 1.8 copy number alterations (CNAs) per case were identified; about 60% of cases carried no CNAs other than those detected by routine fluorescence in-situ hybridization analysis. Copy-neutral loss-of- heterozygosity was detected in 6% of cases, and most frequently found on 13q, 17p and 11q. Minimal deleted regions (MDRs) were refined on 13q14 (deleted in 61% of cases) to the DLEU1 and DLEU2 genes, on 11q22.3 (27%) to ATM, on 2p (gained in 7% of cases) to a 1.9 Mb fragment containing 9 genes, and on 8q24 (5%) to a segment 486 Kb proximal of the MYC locus. 13q deletions exhibited proximal and distal breakpoint cluster regions. Among the most common novel lesions were deletions at 15q15.1 (4%), with the smallest deletion (70.5 Kb) found in the MGA locus; sequence analysis of MGA in 59 samples revealed a truncating mutation in one case lacking a 15q deletion. MNT at 17p13.3, which in addition to MGA and MYC encodes for the network of MAX-interacting proteins, was also found recurrently deleted. Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from cryopreserved diagnostic peripheral blood samples. Copy number analysis of Affymetrix® performed for 353 CLL samples. There are also 147 samples from mononuclear cells negative for CD19, which were used as references for copy number inference.