Activated proliferation of B-cell lymphomas/leukemias with the SHP1 gene silencing by aberrant CpG methylation.
Previously we showed reduced protein and mRNA expression of the SHP1 gene in lymphoma/leukemia cell lines and patient specimens by Northern blot, RT-PCR, Western blot, and immunohistochemical analyses. In this study, aberrant methylation in the SHP1 gene promoter was detected in many B-cell leukemia/lymphoma cell lines as well as in patient specimens, including diffuse large B-cell lymphoma (methylation frequency 93%), MALT lymphoma (82%), mantle cell lymphoma (75%), plasmacytoma (100%) and follicular lymphoma (96%) by methylation-specific PCR, bisulfite sequencing, and restriction enzyme-mediated PCR analyses. The methylation frequency was significantly higher in high-grade MALT lymphoma cases (100%) than in low-grade MALT lymphoma cases (70%), which correlated well with the frequency of no expression of SHP1 protein in high-grade (80%) and low-grade MALT lymphoma (54%). It suggests that the SHP1 gene silencing with aberrant CpG methylation relates to the lymphoma progression. SHP1 protein expression was recovered in B-cell lines after the treatment of the demethylating reagent: 5-aza-2'-deoxycytidine. Transfection of the intact SHP1 gene to the hematopoietic cultured cells, which show no expression of the SHP1 gene, induced growth inhibition, indicating that gene silencing of the SHP1 gene by aberrant methylation plays an important role to get the growth advantage of the malignant lymphoma/leukemia cells. The extraordinarily high frequency (75 to 100%) of CpG methylation of the SHP1 gene in B-cell lymphoma/leukemia patient specimens indicates that the SHP1 gene silencing is one of the critical events to the onset of malignant lymphomas/leukemias as well as important implications for the diagnostic or prognostic markers and the target of gene therapy. These data support the possibility that the SHP1 gene is one of the tumor suppressor genes.
Koyama
Maho
M
Department of Pediatrics, Graduate School of Medicine and Dentistry, Okayama University, Okayama, Japan.
Oka
Takashi
T
Ouchida
Mamoru
M
Nakatani
Yoko
Y
Nishiuchi
Ritsuo
R
Yoshino
Tadashi
T
Hayashi
Kazuhiko
K
Akagi
Tadaatsu
T
Seino
Yoshiki
Y
D001483:Base Sequence; D015139:Blotting, Southern; D015153:Blotting, Western; D002455:Cell Division; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000235:genetics*; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000032:analysis; D020869:Gene Expression Profiling; D015973:Gene Expression Regulation, Leukemic; D020868:Gene Silencing; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D015448:Leukemia, B-Cell / Q000201:enzymology / Q000235:genetics*; D016393:Lymphoma, B-Cell / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012334:RNA, Neoplasm / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
D004273:DNA, Neoplasm; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; C509249:PTPN6 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases