MiR-21 indicates poor prognosis in tongue squamous cell carcinomas as an apoptosis inhibitor.
OBJECTIVE
We aim to examine miR-21 expression in tongue squamous cell carcinomas (TSCC) and correlate it with patient clinical status, and to investigate its contribution to TSCC cell growth, apoptosis, and tumorigenesis.


METHODS
MicroRNA profiling was done in 10 cases of TSCC with microarray. MiR-21 overexpression was quantitated with quantitative reverse transcription-PCR in 103 patients, and correlated to the pathoclinical status of the patients. Immunohistochemistry was used to examine the expression of TPM1 and PTEN, and terminal deoxynucleotidyl transferase-mediated dUTP labeling to evaluate apoptosis. Moreover, miR-21 antisense oligonucleotide (ASO) was transfected in SCC-15 and CAL27 cell lines, and tumor cell growth was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, adherent colony formation, and soft agar assay, whereas apoptosis was determined by Annexin V assay, cytochrome c release, and caspase 3 assay. Tumorigenesis was evaluated by xenografting SCC-15 cells in nude mice.


RESULTS
MiR-21 is overexpressed in TSCC relative to adjacent normal tissues. The level of miR-21 is reversely correlated with TPM1 and PTEN expression and apoptosis of cancer cells. Multivariate analysis showed that miR-21 expression is an independent prognostic factor indicating poor survival. Inhibiting miR-21 with ASO in TSCC cell lines reduces survival and anchorage-independent growth, and induces apoptosis in TSCC cell lines. Simultaneous silencing of TPM1 with siRNA only partially recapitulates the effect of miR-21 ASO. Furthermore, repeated injection of miR-21 ASO suppresses tumor formation in nude mice by reducing cell proliferation and inducing apoptosis.


CONCLUSIONS
miR-21 is an independent prognostic indicator for TSCC, and may play a role in TSCC development by inhibiting cancer cell apoptosis partly via TPM1 silencing.
Li
Jinsong
J
Oral and Maxillofacial Surgery, and Breast Tumor Center, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, People's Republic of China.
Huang
Hongzhang
H
Sun
Lijuan
L
Yang
Mei
M
Pan
Chaobin
C
Chen
Weiliang
W
Wu
Donghui
D
Lin
Zhaoyu
Z
Zeng
Chunxian
C
Yao
Yandan
Y
Zhang
Peter
P
Song
Erwei
E
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D017209:Apoptosis; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D002460:Cell Line; D045744:Cell Line, Tumor; D005260:Female; D055785:Gene Knockdown Techniques; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D051379:Mice; D008819:Mice, Nude; D035683:MicroRNAs / Q000378:metabolism*; D046228:Microarray Analysis; D008875:Middle Aged; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D014062:Tongue Neoplasms / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D014162:Transfection; D014335:Tropomyosin / Q000235:genetics / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
D014408:Biomarkers, Tumor; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D016376:Oligonucleotides, Antisense; D034741:RNA, Small Interfering; C490775:TPM1 protein, human; D014335:Tropomyosin; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human