Overexpression of the paternally expressed gene 10 (PEG10) from the imprinted locus on chromosome 7q21 in high-risk B-cell chronic lymphocytic leukemia.

We report high expression of the maternally imprinted gene PEG10 in high-risk B-CLL defined by high LPL mRNA expression. Differential expression was initially identified by microarray analysis and confirmed by real time PCR in 42 B-CLL patients. mRNA expression ranged from 0.3- to 375.4-fold compared to normal peripheral blood mononuclear cells (PBMNC). Expression levels in CD19+ B-CLL cells were 100-fold higher than in B-cells from healthy donors. PEG10 expression levels in B-CLL patient samples remained stable over time even after chemotherapy. High PEG10 expression correlated with high LPL expression (p=0.001) and a positive Coombs' test (p=0.04). Interestingly, similar expression patterns were observed for the neighbouring imprinted gene sarcoglycan-epsilon (SGCE). Monoallelic expression and maintained imprinting of PEG10 were found by allele- or methylation-specific PCR. The intensity of intracellular staining of PEG10 protein corresponded to mRNA levels as confirmed by immunofluorescence staining. Short term knock-down of PEG10 in B-CLL cells and HepG2 cells was not associated with changes in cell survival but resulted in a significant change in the expression of 80 genes. However, long term inhibition of PEG10 led to induction of apoptosis in B-CLL cells. Our data indicate (i) a prognostic value of PEG10 in B-CLL patients; (ii) specific deregulation of the imprinted locus at 7q21 in high-risk B-CLL; (iii) a potential functional and biological role of PEG10 protein expression. Altogether, PEG10 represents a novel marker in B-CLL. Copyright (c) 2007 Wiley-Liss, Inc.