Silencing Bcl-2 in models of mantle cell lymphoma is associated with decreases in cyclin D1, nuclear factor-kappaB, p53, bax, and p27 levels.
Molecular mechanisms responsible for lymphoma resistance to apoptosis often involve the bcl-2 pathway. In this study, we investigated the cell signaling pathways activated in bcl-2-overexpressing human mantle cell lymphoma cell lines (JVM-2 and Z-138) that have been treated with oblimersen, a molecular gene silencing strategy that effectively suppresses bcl-2 in vitro and in vivo. Z-138 cells expressed higher levels of bcl-2 and were more sensitive to the effects of bcl-2 silencing, mediated by oblimersen or bcl-2 small interfering RNA, in vitro. Tumors derived following injection of Z-138 cells were sensitive to oblimersen as judged by decreases in tumor growth rate and decreases in cell proliferation (as measured by Ki-67). Immunohistochemistry and Western blot analysis of oblimersen-treated Z-138 tumors revealed a dose-dependent decrease in bcl-2 levels and an associated increase in the proapoptotic proteins caspase-3 and caspase-9. Silencing bcl-2 in Z-138 xenografts revealed an associated dose-dependent suppression of bax, a decrease in nuclear factor-kappaB and phospho-nuclear factor-kappaB, and transient loss of p53 levels. Coimmunoprecipitation studies suggest that the latter observation is mediated by an association between bcl-2 and phospho-mdm2. Bcl-2 silencing also led to p27 down-regulation and coimmunoprecipitation studies point to a role for bcl-2 in regulation of p27 localization/degradation. Bcl-2 silencing was also correlated with loss of cyclin D1a protein levels but not cyclin D1b levels. Coimmunoprecipitation studies indicate that bcl-2 may mediate its effects on cyclin D1a via interaction with p38 mitogen-activated protein kinase as well as a previously unreported interaction between bcl-2 and cyclin D1a.
Tucker
Catherine A
CA
Department of Advanced Therapeutics, BC Cancer Research Center, Vancouver, British Columbia, Canada V5Z 1L3. ctucker@bccrc.ca
Kapanen
Anita I
AI
Chikh
Ghania
G
Hoffman
Brad G
BG
Kyle
Alastair H
AH
Wilson
Ian M
IM
Masin
Dana
D
Gascoyne
Randy D
RD
Bally
Marcel
M
Klasa
Richard J
RJ
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D049109:Cell Proliferation; D056741:Cyclin D; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D004195:Disease Models, Animal; D020868:Gene Silencing; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D020522:Lymphoma, Mantle-Cell / Q000235:genetics* / Q000378:metabolism / Q000517:prevention & control; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013873:Thionucleotides / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
C494827:Bax protein, mouse; C493961:Cdkn1b protein, mouse; D056741:Cyclin D; D016213:Cyclins; D004268:DNA-Binding Proteins; D016328:NF-kappa B; D009363:Neoplasm Proteins; D016376:Oligonucleotides, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; C499308:Rag2 protein, mouse; D013873:Thionucleotides; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D050760:Cyclin-Dependent Kinase Inhibitor p27; C408162:oblimersen; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2