Overexpression of cyclin D1 promotes tumor cell growth and confers resistance to cisplatin-mediated apoptosis in an elastase-myc transgene-expressing pancreatic tumor cell line.
OBJECTIVE
Elevated cyclin D1 in human pancreatic cancer correlates with poor prognosis. Because pancreatic cancer is invariably resistant to chemotherapy, the goal of this study was to examine whether the drug resistance of pancreatic cancer cells is in part attributed to cyclin D1 overexpression.


METHODS
Stable overexpression and small interfering RNA (siRNA)--mediated knockdown of cyclin D1 were done in the newly established Ela-myc pancreatic tumor cell line. Cisplatin sensitivity of control, overexpressing, and siRNA-transfected cells was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, clonogenic, and apoptotic assays [DNA fragmentation, sub-G1, and poly(ADP-ribose) polymerase cleavage analysis]. The role of nuclear factor-kappaB and apoptotic proteins in cyclin D1-mediated chemoresistance was examined by EMSA and Western blotting, respectively.


RESULTS
Overexpression of cyclin D1 in Ela-myc pancreatic tumor cells promoted cell proliferation and anchorage-independent growth. Moreover, cyclin D1-overexpressing cells exhibited significantly reduced chemosensitivity and a higher survival rate upon cisplatin treatment, as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and clonogenic assays, respectively. Although overexpression of cyclin D1 rendered cells more resistant to cisplatin-induced apoptosis, siRNA-directed suppression of cyclin D1 expression resulted in enhanced susceptibility to cisplatin-mediated apoptosis. The attenuation of cisplatin-induced cell death in cyclin D1-overexpressing cells was correlated with the up-regulation of nuclear factor-kappaB activity and maintenance of bcl-2 and bcl-xl protein levels.


CONCLUSIONS
These results suggest that overexpression of cyclin D1 can contribute to chemoresistance of pancreatic cancer cells because of the dual roles of cyclin D1 in promoting cell proliferation and in inhibiting drug-induced apoptosis.
Biliran
Hector
H
Department of Pathology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Wang
Yong
Y
Banerjee
Sanjeev
S
Xu
Haiming
H
Heng
Henry
H
Thakur
Archana
A
Bollig
Aliccia
A
Sarkar
Fazlul H
FH
Liao
Joshua D
JD
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002945:Cisplatin / Q000494:pharmacology*; D003470:Culture Media / Q000494:pharmacology; D019938:Cyclin D1 / Q000235:genetics* / Q000502:physiology; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D016328:NF-kappa B / Q000378:metabolism; D010196:Pancreatic Elastase / Q000235:genetics; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D000093542:Gemcitabine
D000970:Antineoplastic Agents; D003470:Culture Media; C489428:Myc protein, mouse; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D034741:RNA, Small Interfering; D003841:Deoxycytidine; D019938:Cyclin D1; D010196:Pancreatic Elastase; D002945:Cisplatin; D000093542:Gemcitabine