Overexpression of miR-200c induces chemoresistance in esophageal cancers mediated through activation of the Akt signaling pathway.
OBJECTIVE
To determine the relationship between resistance to chemotherapy and microRNA (miRNA) expression in esophageal cancer, we focused on miRNAs known to be associated with maintenance of stem cell function.


METHODS
Using 98 formalin-fixed, paraffin-embedded samples obtained from patients with esophageal cancer who had received preoperative chemotherapy followed by surgery, we measured expression levels of several miRNAs that are considered to be involved in the regulation of stem cell function (e.g., let-7a, let-7g, miR-21, miR-134, miR-145, miR-155, miR-200c, miR-203, and miR-296) by real-time reverse transcriptase PCR. Then, we examined the relationship between miRNA expression and prognosis or response to chemotherapy. To investigate the mechanism of miRNA-induced chemoresistance, in vitro assays were carried out using esophageal cancer cells.


RESULTS
Analyses of the 9 miRNAs expression showed that overexpression of miR-200c (P = 0.037), underexpression of miR-145 (P = 0.023), and overexpression of miR-21 (P = 0.048) correlated significantly with shortened overall duration of survival. In particular, miR-200c expression correlated significantly with response to chemotherapy (P = 0.009 for clinical response; P = 0.007 for pathologic response). In vitro assay showed significantly increased miR-200c expression in cisplatin-resistant cells compared with their parent cells (∼1.7-fold). In anti-miR-200c-transfected cells, chemosensitivity to cisplatin and apoptosis after exposure to cisplatin was found to increase as compared with the negative control. Western blotting showed that knockdown of miR-200c expression was associated with increased expression of PPP2R1B, a subunit of protein phosphatase 2A, which resulted in reduced expression of phospho-Akt.


CONCLUSIONS
Results of this study emphasized the involvement of miR-200c in resistance to chemotherapy among esophageal cancers and that this effect was mediated through the Akt pathway.
Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Osaka, Japan.
Rie
R
Hamano
Hiroshi
H
Miyata
Makoto
M
Yamasaki
Yukinori
Y
Kurokawa
Johji
J
Hara
Jeong Ho
JH
Moon
Kiyokazu
K
Nakajima
Shuji
S
Takiguchi
Yoshiyuki
Y
Fujiwara
Masaki
M
Mori
Yuichiro
Y
Doki
D000368:Aged; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis / Q000188:drug therapy / Q000235:genetics* / Q000601:surgery; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D004789:Enzyme Activation / Q000235:genetics / Q000502:physiology; D004938:Esophageal Neoplasms / Q000175:diagnosis / Q000188:drug therapy / Q000235:genetics* / Q000601:surgery; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D008297:Male; D035683:MicroRNAs / Q000235:genetics* / Q000502:physiology; D008875:Middle Aged; D051058:Oncogene Protein v-akt / Q000378:metabolism* / Q000502:physiology; D011379:Prognosis; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D015854:Up-Regulation / Q000235:genetics
D000970:Antineoplastic Agents; C533896:MIRN200 microRNA, human; D035683:MicroRNAs; D051058:Oncogene Protein v-akt; D002945:Cisplatin