MiR-21 upregulation induced by promoter zone histone acetylation is associated with chemoresistance to gemcitabine and enhanced malignancy of pancreatic cancer cells.
OBJECTIVE
MicroRNA-21 (miR-21) is reported to be overexpressed and to contribute to proliferation, apoptosis and gemcitabine resistance in pancreatic ductal adenocarcinomas (PDACs). The aims of this study were to explore regulation of miR-21 expression by epigenetic change and its impact on chemoresistance and malignant properties of of pancreatic cancer.


METHODS
We retrospectively collected 41 cases of advanced pancreatic cancer patients who were sensitive or resistant to gemcitabine and assessed levels of serum circulating miR-21 for correlation with cytotoxic activity. Histone acetylation in the miR-21 promoter was also studied in gemcitabine-sensitive and gemcitabine-resistant PDAC cells. Gemcitabine-resistant HPAC and PANC-1 cells were transfected with pre-miR-21 precursors (pre-miR-21) and antisense oligonucleotides (anti-miR-21), and were treated with TSA. Finally, invasion and metastasis assays were performed and alteration in mir-21, PTEN, AKT and pAKT level was evaluated in these cells.


RESULTS
Serum miR-21 levels were increased in gemcitabine- resistant PDAC patients compared with gemcitabine-sensitive subjects. The miR-21 levels were increased in 6 PDAC cells treated with gemcitabine significantly, associated with 50% inhibitory concentrations (IC50s). Histone acetylation levels at miR-21 promoter were increased in PDAC cells after treatment with gemcitabine. Enhanced invasion and metastasis, increased miR-21 expression, decreased PTEN, elevated pAKT level were demonstrated in gemcitabine-resistant HPAC and PANC-1 cells. Pre-miR-21 transfection or TSA treatment further increased invasion and metastasis ability, decreased PTEN, and elevated pAKT levels in these two lines. In contrast, anti-miR-21 transfection could reverse invasion and metastasis, and PTEN and pAKT expressions induced by gemcitabine.


CONCLUSIONS
MiR-21 upregulation induced by histone acetylation in the promoter zone is associated with chemoresistance to gemcitabine and enhanced malignant potential in pancreatic cancer cells.
Department of Medical Oncology, Shanghai First People's Hospital, Shanghai Jiao Tong University, Shanghai, China E-mail : liweiwangdr@163.com.
Wei-Feng
WF
Song
Lei
L
Wang
Wei-Yi
WY
Huang
Xun
X
Cai
Jiu-Jie
JJ
Cui
Li-Wei
LW
Wang
D000107:Acetylation; D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics / Q000556:secondary; D000964:Antimetabolites, Antineoplastic / Q000627:therapeutic use; D017209:Apoptosis; D014408:Biomarkers, Tumor / Q000235:genetics; D015153:Blotting, Western; D021441:Carcinoma, Pancreatic Ductal / Q000188:drug therapy / Q000235:genetics / Q000556:secondary; D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D005500:Follow-Up Studies; D006657:Histones / Q000378:metabolism*; D006801:Humans; D008297:Male; D035683:MicroRNAs / Q000235:genetics*; D008875:Middle Aged; D009367:Neoplasm Staging; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology*; D011379:Prognosis; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D000093542:Gemcitabine
D000964:Antimetabolites, Antineoplastic; D014408:Biomarkers, Tumor; D006657:Histones; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D012333:RNA, Messenger; D003841:Deoxycytidine; D000093542:Gemcitabine