Imprinted DLK1 is a putative tumor suppressor gene and inactivated by epimutation at the region upstream of GTL2 in human renal cell carcinoma

Abstract

A common deletion at chromosomal arm 14q32 in human renal cell carcinoma (RCC) prompted us to explore a tumor suppressor gene (TSG) in this region. We report that imprinted DLK1 at 14q32, a regulator of adipocyte differentiation, is a candidate TSG in RCCs. DLK1 expression was lost in 39 out of 50 (78%) primary RCC tissues, whereas expression of DLK1 was maintained in every normal kidney tissue examined. DLK1 was expressed in only one of 15 (7%) RCC-derived cell lines. In order to see the biological significance of DLK1 inactivation in RCCs, we tested the effect of restoration of DLK1 in RCC cell lines, using a recombinant retrovirus containing the gene. Reintroduction of DLK1 into DLK1-null RCC cell lines markedly increased anchorage-independent cell death, anoikis and suppressed tumor growth in nude mice. We then investigated the underlying mechanisms for DLK1 inactivation in RCCs. We found loss of heterozygosity at this region in 12 out of 50 RCC tissues (24%). To explore the role of epigenetic regulation of DLK1 inactivation in RCCs, we conducted methylation analysis of the upstream region and the gene body of DLK1. We could not find a differentially methylated region in either the upstream region or the gene body of DLK1. However, we found that gain of methylation upstream of GTL2, a reciprocal imprinted gene for DLK1, is a critical epigenetic alteration for the inactivation of DLK1 in RCCs. The present data have shown that gain of methylation upstream of the untranslated GTL2 leads to pathological downregulation of DLK1 in RCCs.

dlk1/FA1 Regulates the Function of Human Bone Marrow Mesenchymal Stem Cells by Modulating Gene Expression of Pro-inflammatory Cytokines and Immune Response-related Factors

“…Two inhibitors of apoptosis were also up-regulated, baculoviral inhibitor of apoptosis repeat-containing protein 3 (BIRC3) (56) and BCL2-related protein A1 (BCL2A1). These data suggest that dlk1 may modulate the apoptotic responses and corroborate the recent findings that dlk1 may function as a tumor suppressor gene with the ability to suppress tumor growth and increase anchorage-dependent cell death of cancer cells (57). Interestingly, overexpression of Dlk1 in hMSC did not affect their cell growth (15) suggesting that the dlk1 effects on cell growth may be cell type-dependent.…”

Silencing of the Imprinted DLK1-MEG3 Locus in Human Clinically Nonfunctioning Pituitary Adenomas

“…In contrast, Li et al 49 reported that expression of DLK1 resulted in inhibition of proliferation in hematopoietic cells. Furthermore, Kawakami et al 21 demonstrated that DLK1 expression is lost in human renal cell carcinomas and that its re-expression increases anchorage-independent cell death and suppresses tumor growth in nude mice. The role of DLK1 in human pituitary tumor development requires further investigation.…”

“…Loss of imprinting results in a phenotypic spectrum ranging from embryonic lethality to growth retardation and developmental abnormalities. 18,19 In addition, dysregulation of genes at this locus has been found in a subset of human tumors, such as renal cell carcinoma and neuroblastoma, 20,21 suggesting that the DLK1-MEG3 locus plays a role in the development of a number of human neoplasms.…”

Methylation analysis of the intergenic differentially methylated region of DLK1-GTL2 in human

“…Detailed information about one representative sample is given and showed intermediate patterns in three of the eight clones analysed. 27 The possibility exists that the intermediate patterns represent bacterial recombination artefacts. The amplification of bisulphite-treated DNA can generate heteroduplexes, as the parental template strands only differ at specific CpG-sites.…”