Aberrant DNA methylation ofp57KIP2 gene in the promoter region in lymphoid malignancies of B-cell phenotype

Abstract

The cyclin-dependent kinase inhibitor p57 KIP2 is thought to be a potential tumor suppressor gene (TSG). The present study examines this possibility. We found that the expression of p57 KIP2 gene is absent in various hematological cell lines. Exposing cell lines to the DNA demethylating agent 5-aza-2-deoxycytidine restored p57 KIP2 gene expression. Bisulfite sequencing analysis of its promoter region showed that p57 KIP2 DNA was completely methylated in cell lines that did not express the p57 KIP2 gene. Thus, DNA methylation of its promoter might lead to inactivation of the p57 KIP2 gene. DNA methylation of this region is thought to be an aberrant alteration, since DNA was not methylated in normal peripheral blood mononuclear cells or in reactive lymphadenitis. Methylation-specific polymerase chain reaction analysis found frequent DNA methylation of the p57 KIP2 gene in primary diffuse large B-cell lymphoma (54.9%) and in follicular lymphoma (44.0%), but methylation was infrequent in myelodysplastic syndrome and adult T-cell leukemia (3.0% and 2.0%, respectively). These findings directly indicate that the profile of the p57 KIP2 gene corresponds to that of a TSG. IntroductionCell cycle progression is promoted by cyclins and cyclindependent kinases (CDKs) and is counterbalanced by CDK inhibitors. 1 These components are regulated in the normal cell cycle, and disrupted regulation is closely related to tumorigenesis. For example, activation of cyclin D1 by bcl-1 translocation (t(11; 14)(q13;q23)) is a critical genetic alteration in mantle cell lymphoma, 2,3 and the CDK inhibitor p16 INK4A is genetically lost or mutated in many malignancies. 4 CDK inhibitors have been categorized into 2 families. One family, inhibitors of CDK4 (INK4s), includes p16 and p15, has repeated ankyrinlike sequences, and is a specific inhibitor of CDK4 and CDK6, resulting in competing cyclin D. 5,6 The other family, kinase inhibitor proteins (KIPs), includes p21 CIP1 , p27 KIP1 , and p57 KIP2 , 7-10 and this family potently inhibits the binding of several cyclin/CDK complexes. The presence of mutations and deletions in INK4s indicates that they are tumor suppressor genes (TSGs) 4 and that their function as negative regulators of cell proliferation fits the profile of TSGs. Because the KIP family also consists of CDK inhibitors, genetic alterations of the p21 CIP1 gene 11 and p57 KIP2 genes 12-14 have been extensively studied. In particular, the p57 KIP2 gene is located at chromosome 11p15.5, a region implicated in sporadic cancers, including those of the breast, 15 liver, 16 and bladder. 17 Beckwith-Wiedemann syndrome (BWS), 18 which is characterized by the somatic overgrowth of various tissues, including the kidneys, liver, and skeletal muscle, and by a predisposition to embryonal tumors of these organs (Wilms tumor, hepatoblastoma, and embryonal rhabdomyosarcoma), is linked to this region. 19 Although germ line point mutations of the p57 KIP2 gene resulting in protein truncation have been identified in some patients with BWS, 20,21 so...

Childhood and adult ALL: Differences in epigenetic lesions associated with cell cycle genes

“…This has been observed in other lymphoid malignancies [9], although p57 can be upregulated by 5-aza-2 0 -deoxicytidine [5].…”

Inactivation of class II transactivator by DNA methylation and histone deacetylation associated with absence of HLA-DR induction by interferon-γ in haematopoietic tumour cells

“…For instance, somatic changes in the methylation of CpG dinucleotides commonly occur during the pathogenesis of human tumours (Jones and Baylin, 2002). Among haematopoietic tumours, aberrant methylation of promoter-associated CpG islands (CGIs) in oestrogen receptor, p16INK4A, p15INK4B, p73, p57KIP2 and DAP kinase has been observed in acute lymphocytic leukaemia (ALL), acute myeloid leukaemia (AML), malignant lymphoma and multiple myeloma (Herman et al, 1997;Katzenellenbogen et al, 1999;Garcia-Manero et al, 2002a, b;Li et al, 2002). Methylation-mediated silencing of genes involved in immune system function has not been reported in haematopoietic tumours, however.…”

Identification of novel VHL target genes and relationship to hypoxic response pathways

“…BWS is characterized by prenatal and/or postnatal overgrowth and susceptibility to embryonal cancers such as Wilms' tumours (Maher and Reik, 2000). Somatic CDKN1C mutations have not been reported in human cancers, but epigenetic silencing of CDKN1C has been reported in lymphoid and solid cancers (Kikuchi et al, 2002;Li et al, 2002), although RCC has not yet been analysed. CDKN1C induces cell cycle arrest by inhibiting the activity of cyclin-dependent kinases, so both genetic and functional evidence implicate CDKN1C as a candidate TSG.…”