Lack of TNFalpha expression protects anaplastic lymphoma kinase-positive T-cell lymphoma (ALK+ TCL) cells from apoptosis.
Here we report that T-cell lymphomas characterized by the expression of anaplastic lymphoma kinase (ALK+ TCL) fail to express the TNFalpha and frequently display DNA methylation of the TNFalpha gene promoter. While only a subset of the ALK+ TCL-derived cell lines showed a high degree of the promoter methylation, all 6 showed low to nondetectable expression of the TNFalpha mRNA, and none expressed the TNFalpha protein. All 14 ALK+ TCL tissue samples examined displayed some degree of the TNFalpha promoter methylation, which was the most prominent in the distal portion of the the promoter. Treatment with a DNA methyltransferase inhibitor, 5'-aza-2'-deoxy-cytidine (5-ADC), reversed the promoter methylation and led to the expression of TNFalpha mRNA and protein. Furthermore, in vitro DNA methylation of the promoter impaired its transcriptional activity in the luciferase reporter assay. This impairment was seen even if only either distal or proximal portion were methylated, with methylation of the former exerting a more profound inhibitory effect. Notably, the ALK+ TCL cell lines uniformly expressed the type 1 TNFalpha receptor (TNF-R1) protein known to transduce the TNFalpha-induced pro-apoptotic signals. Moreover, exogenous TNFalpha inhibited growth of the ALK+ TCL cell lines in a dose-dependent manner and induced activation of the members of the cell apoptotic pathway: Caspase 8 and caspase 3. These findings provide additional rationale for the therapeutic inhibition of DNA methyltransferases in ALK+ TCL. They also suggest that treatment with TNFalpha may be highly effective in this type of lymphoma.
Zhang
Qian
Q
Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. qian2@mail.med.upenn.edu
Wang
Hong Y
HY
Bhutani
Gauri
G
Liu
Xiaobin
X
Paessler
Michele
M
Tobias
John W
JW
Baldwin
Donald
D
Swaminathan
Kunchithapadam
K
Milone
Michael C
MC
Wasik
Mariusz A
MA
D000077548:Anaplastic Lymphoma Kinase; D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D045744:Cell Line, Tumor; D019175:DNA Methylation; D017931:DNA Primers / Q000235:genetics; D015870:Gene Expression; D006801:Humans; D017728:Lymphoma, Large-Cell, Anaplastic / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology
D017931:DNA Primers; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D047888:Receptors, Tumor Necrosis Factor, Type I; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases