Genomic approach in B-cell Chronic Lymphocytic Leukemia: molecularly distinct subgroups of patients with 13q14 deletion

B-cell chronic lymphocytic leukemia (B-CLL) is characterized by a highly variable clinical course that reflects its heterogeneous genomic pattern. To better define molecular subtypes of the disease, we performed SNP and gene expression profiling microarray analyses in a panel of early stage (Binet A) patients. A clustering analysis of genomic profiles identified four significant groups mainly driven by del(13)(q14) and trisomy 12. Notably, patients with del(13)(q14) were grouped in two separate clusters based on the presence of a biallelic loss and the extension of the deletion. The shorter monoallelic deleted 13q14 region was found to be 635 kb in length, not encompassing the mir-15a/16-1 locus. Interestingly, the mir-15a and mir-16 expression was found to be significantly down-regulated only in patients with biallelic loss. Furthermore, a multiclass supervised analysis identified a different transcriptional signatures in the two genomic subgroups with del(13)(q14). Finally, an integrative approach identified 93 transcripts, mainly mapped to chromosome 12 and 13q12-q14.3, whose expression was significantly correlated with the DNA copy number. Overall, our data further support the notion that transcription deregulation in B-CLL could be mostly due to a gene dosage effect and underscore the presence of two distinct molecular types of 13q14 deleted patients with potential clinical relevance.

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Mosca L, Fabris S, Lionetti M, Todoerti K, Agnelli L, Morabito F, Cutrona G, Andronache A, Matis S, Ferrari F, Gentile M, Spriano M, Callea V, Festini G, Molica S, Deliliers GL, Bicciato S, Ferrarini M, Neri A