Methylation status of cyclin-dependent kinase inhibitor genes within the transforming growth factor beta pathway in human T-cell lymphoblastic lymphoma/leukemia.
Epigenetic silencing of downstream components of the transforming growth factor beta pathway including the cyclin-dependent kinase inhibitors (CDKIs) p15INK4B, p27KIP1 and p21CIP1 is implicated in the pathogenesis of some hematological malignancies. Loss of p15INK4B expression due to promoter methylation occurs frequently in human T-cell acute lymphoblastic leukemia (T-ALL) but the expression and methylation status of p27KIP1 remains to be characterized in T-ALL or T-cell lymphoblastic lymphoma (T-LBL). As well, while some have reported a high frequency of p21CIP1 methylation in ALL patient samples others have found the gene to be unmethylated in this disease and the relationship between p21CIP1 expression and promoter methylation has not been examined in T-LBL. Using RNase protection assays (RPA) and methylation specific PCR (MSP), we found p27KIP1 to be expressed and its promoter unmethylated in 20 of 20 (100%) and 28 of 28 (100%) T-LBL/ALL samples, respectively. In contrast, p21CIP1 mRNA was absent in 7 of 14 (50%) T-LBL biopsies and 5 of 6 (83%) T-ALL cell lines. However, like p27KIP1 there was no evidence of p21CIP1 promoter methylation by MSP or temporal temperature gradient electrophoresis (TTGE) analysis of 35 CpG sites in any of the 28 T-LBL/ALLs analyzed. Similar to T-ALL, we found p15INK4B mRNA was absent in 13 of 14 (93%) T-LBL biopsies and its promoter methylated in 6 of 10 (64%) cases. Our results indicate that p21CIP1 mRNA is absent in human T-LBL biopsies and T-ALL cell lines at a high frequency. However, unlike p15INK4B, reduced p21CIP1 expression in T-LBL/ALL is independent of dense promoter-associated CpG methylation. In contrast to some hematological malignancies p27KIP1 methylation does not appear to contribute significantly to T-LBL/ALL pathogenesis.
Department of Pathology, Saskatoon Cancer Centre, Royal University Hospital, University of Saskatchewan, 103 Hospital Drive, Saskatoon, Saskatchewan, S7N 0W8, Canada.
Stuart A
SA
Scott
Tomofumi
T
Kimura
Wei-Feng
WF
Dong
Ryo
R
Ichinohasama
Susan
S
Bergen
Annette
A
Kerviche
David
D
Sheridan
John F
JF
DeCoteau
D002352:Carrier Proteins / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics; D050762:Cyclin-Dependent Kinase Inhibitor p15; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D016213:Cyclins / Q000235:genetics; D019175:DNA Methylation; D017931:DNA Primers; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000209:etiology / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods; D011401:Promoter Regions, Genetic / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics
C493956:CDKN1A protein, human; C436291:CDKN1B protein, human; C493966:CDKN2B protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; D016212:Transforming Growth Factor beta; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases