Frequent downregulation of miR-34 family in human ovarian cancers.
OBJECTIVE
The miR-34 family is directly transactivated by tumor suppressor p53, which is frequently mutated in human epithelial ovarian cancer (EOC). We hypothesized that miR-34 expression would be decreased in EOC and that reconstituted miR-34 expression might reduce cell proliferation and invasion of EOC cells.


METHODS
miR-34 expression was determined by quantitative reverse transcription-PCR and in situ hybridization in a panel of 83 human EOC samples. Functional characterization of miR-34 was accomplished by reconstitution of miR-34 expression in EOC cells with synthetic pre-miR molecules followed by determining changes in proliferation, apoptosis, and invasion.


RESULTS
miR-34a expression is decreased in 100%, and miR-34b*/c in 72%, of EOC with p53 mutation, whereas miR-34a is also downregulated in 93% of tumors with wild-type p53. Furthermore, expression of miR-34b*/c is significantly reduced in stage IV tumors compared with stage III (P = 0.0171 and P = 0.0029, respectively). Additionally, we observed promoter methylation and copy number variations at mir-34. In situ hybridization showed that miR-34a expression is inversely correlated with MET immunohistochemical staining, consistent with translational inhibition by miR-34a. Finally, miR-34 reconstitution experiments in p53 mutant EOC cells resulted in reduced proliferation, motility, and invasion, the latter of which was dependent on MET expression.


CONCLUSIONS
Our work suggests that miR-34 family plays an important role in EOC pathogenesis and reduced expression of miR-34b*/c may be particularly important for progression to the most advanced stages. Part of miR-34 effects on motility and invasion may be explained by regulation of MET, which is frequently overexpressed in EOC.
Department of Biomedical Sciences, Cornell University, Ithaca, New York 14853-6401, USA.
David C
DC
Corney
Chang-Il
CI
Hwang
Andres
A
Matoso
Markus
M
Vogt
Andrea
A
Flesken-Nikitin
Andrew K
AK
Godwin
Aparna A
AA
Kamat
Anil K
AK
Sood
Lora H
LH
Ellenson
Heiko
H
Hermeking
Alexander Yu
AY
Nikitin
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D049109:Cell Proliferation; D019175:DNA Methylation; D015536:Down-Regulation; D005260:Female; D018628:Gene Dosage; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D010051:Ovarian Neoplasms / Q000235:genetics*; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D017978:Receptors, Growth Factor / Q000378:metabolism*
C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D017978:Receptors, Growth Factor; C491743:MET protein, human; D019859:Proto-Oncogene Proteins c-met