Suppression of Dicer increases sensitivity to gefitinib in human lung cancer cells.
BACKGROUND
Accumulating evidence is revealing an important role of microRNA (miRNA) in tumor progression and chemotherapeutic resistance. Dicer is a cytoplasmic endoribonuclease type III crucial for production of mature miRNAs. The aberrant expression of Dicer has also been reportedly associated with clinical aggressiveness, prognosis, and patient survival in various cancer types. However, the molecular mechanisms of Dicer in acquired gefitinib resistance are still not clear.


METHODS
In this study, we analyzed the protein level of Dicer between gefitinib-sensitive (PC9) and gefitinib-resistant (PC9/GR) non-small-cell lung cancer (NSCLC) cell lines by Western blot analysis. Silence and overexpression of the Dicer were performed to investigate the effects on gefitinib sensitivity, as assessed by (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay and sub-G1 assay of flow cytometry. To further explore the mechanism of chemoresistance, we examined whether Dicer knockdown led to modulating specific miRNAs and its miRNA target genes.


RESULTS
Dicer expression was significantly increased in PC9/GR compared with PC9 cells. Knockdown of Dicer restores gefitinib sensitivity in resistant cells, and overexpression of Dicer enhances resistance to gefitinib in sensitive cells. Silencing of Dicer induces sensitivity to gefitinib in NSCLC cells through the downregulation of miR-30b/c and miR-221/222 to increase the protein level of caspase-3, resulting in an increase in gefitinib-induced apoptosis.


CONCLUSIONS
Dicer contributes to the resistance to gefitinib in lung cancer. These results indicate that Dicer may be a target for diagnosis and therapy of patients with resistance to gefitinib.
National Institute of Cancer Research, National Health Research Institutes, Zhunan, Taiwan.
Jui-Chieh
JC
Chen
Yen-Hao
YH
Su
Ching-Feng
CF
Chiu
Yi-Wen
YW
Chang
Yang-Hao
YH
Yu
Chi-Feng
CF
Tseng
Hsin-An
HA
Chen
Jen-Liang
JL
Su
D000230:Adenocarcinoma / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D005260:Female; D000077156:Gefitinib; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics; D008297:Male; D035683:MicroRNAs / Q000378:metabolism; D008875:Middle Aged; D011799:Quinazolines / Q000627:therapeutic use*; D012333:RNA, Messenger / Q000378:metabolism; D012189:Retrospective Studies; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism*
D000970:Antineoplastic Agents; D053148:Caspase 3; D000077156:Gefitinib; D035683:MicroRNAs; D011799:Quinazolines; D012333:RNA, Messenger; D043244:Ribonuclease III; C525709:MIR221, human; C525710:MIR222, human; C546086:MIRN30b microRNA, human