In Leukemia Research on line
Chronic lymphocytic leukemia (CLL) is a highly heterogeneous disease which has proven amenable to subtyping through genomic microarray analysis. Initially, 13q14 deletions as an isolated finding were associated with a favorable prognosis. However, recent evidence has revealed significant heterogeneity within the 13q14 deletion subtype, thus, there is a clear clinical need for more precise stratification of 13q14 deletions at the genomic level. The minimal deleted region (MDR) includes: DLEU2, DLEU7, MIR15A/MIR16-1 and part of DLEU1. Recent studies suggest that in addition to the MDR, the size of the deletion and the involvement of the nearby tumor suppressor gene RB1 serve as an independent prognostic biomarker for disease progression. Nine individuals in whom a 13q deletion had previously been identified by bacterial artificial chromosome (BAC) array were re-analyzed using the Cancer Cytogenomics Microarray Consortium's consensus design on an Agilent (Santa Clara, CA) 180K oligonucleotide platform. Based on the size and location of the 13q14 deletion, cases were further classified as having type (smaller, not including RB1) or type II (larger, including RB1) deletions, as described by Ouilette et al. (Cancer Res, 2008). Type I deletions were seen in 77% of cases, and Type II deletions in 22%. There was a single case of a biallelic 13q14 deletion. Deleted regions ranged in size from 1.0 to 9.8 Mb. Unlike older BAC technologies that are subject to limited resolution, the CCMC 180K oligonucleotide array allowed for further clarification of 13q deletion cases, providing valuable clinical and prognostic information for CLL.