HDM4 is overexpressed in mantle cell lymphoma and its inhibition induces p21 expression and apoptosis.
In mouse models and cell lines, murine double minute 2 (MDM2) and MDM4 have been shown to synergistically promote proteasome-mediated degradation of p21 and p53. MDM4 also inhibits p53-mediated transcriptional activation of p21. p53 expression results in increased p21 expression, a negative cell-cycle regulatory protein and an inhibitor of cyclin D1. As mantle cell lymphoma is characterized by cyclin D1 overexpression, we assessed for human homolog of MDM4 (HDM4) expression and its effect on p21 in mantle cell lymphoma. Using immunohistochemical methods, in reactive lymph nodes (n=19) germinal center cells strongly expressed HDM4 in the nucleus and the cytoplasm, but mantle zone B-cells were only dimly positive. In mantle cell lymphoma tumors, aberrant HDM4 nuclear expression was observed in 18 of 19 (95%) cases. In contrast, HDM4 in other B-cell non-Hodgkin lymphoma types retained its normal pattern of expression. To further characterize the differential upregulation of HDM4 in mantle cell lymphoma, HDM4 was assessed by quantitative real-time polymerase chain reaction in four mantle cell lymphoma cell lines (Granta 519, Z-138, SP-53, and Mino) and six mantle cell lymphoma tumors. Both the splicing variant HDM4-S, containing only the p53-binding domain, and full length HDM4 were increased compared with normal CD19+ B-cells (P<0.05). Using small interfering RNA to inhibit HDM4 in the SP53 and Mino cell lines showed increased p21 and active caspase-3, the latter indicating increased apoptosis. Our results show that HDM4 is overexpressed in mantle cell lymphoma and, at least in part, exerts its effect by suppressing p21 expression, thereby enhancing cell-cycle progression. Inhibition of HDM4 may serve as a potential approach in the design of therapy for patients with mantle cell lymphoma.
Liang
Mei
M
Department of Hematopathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
Han
Xin
X
Vadhan-Raj
Saroj
S
Nguyen
Martin
M
Zhang
Yu H
YH
Fernandez
Michael
M
Drakos
Elias
E
Konoplev
Sergej N
SN
Yin
C Cameron
CC
Miranda
Roberto N
RN
McDonnell
Timothy J
TJ
Medeiros
L Jeffrey
LJ
Bueso-Ramos
Carlos E
CE
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism / Q000473:pathology; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000032:analysis; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D008224:Lymphoma, Follicular / Q000378:metabolism / Q000473:pathology; D016403:Lymphoma, Large B-Cell, Diffuse / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020522:Lymphoma, Mantle-Cell / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics
C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004273:DNA, Neoplasm; C482775:MDM4 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53