Dicer, Drosha, and outcomes in patients with ovarian cancer.
BACKGROUND
We studied Dicer and Drosha, components of the RNA-interference machinery, in ovarian cancer.


METHODS
We measured messenger RNA (mRNA) levels of Dicer and Drosha in specimens of invasive epithelial ovarian cancer from 111 patients, using a quantitative reverse-transcriptase-polymerase-chain-reaction assay, and compared the results with clinical outcomes. Validation was performed with the use of published microarray data from cohorts of patients with ovarian, breast, and lung cancer. Mutational analyses of genomic DNA from the Dicer and Drosha genes were performed in a subgroup of ovarian-cancer specimens. Dicer-dependent functional assays were performed by means of in vitro transfection with small interfering RNA (siRNA) and short hairpin RNA (shRNA).


RESULTS
Levels of Dicer and Drosha mRNA correlated with the levels of expression of the corresponding protein and were decreased in 60% and 51% of ovarian-cancer specimens, respectively. Low Dicer expression was significantly associated with advanced tumor stage (P=0.007), and low Drosha expression with suboptimal surgical cytoreduction (P=0.02). Cancer specimens with both high Dicer expression and high Drosha expression were associated with increased median survival (>11 years, vs. 2.66 years for other subgroups; P<0.001). We found three independent predictors of reduced disease-specific survival in multivariate analyses: low Dicer expression (hazard ratio, 2.10; P=0.02), high-grade histologic features (hazard ratio, 2.46; P=0.03), and poor response to chemotherapy (hazard ratio, 3.95; P<0.001). Poor clinical outcomes among patients with low Dicer expression were validated in additional cohorts of patients. Rare missense mutations were found in the Dicer and Drosha genes, but their presence or absence did not correlate with the level of expression. Functional assays indicated that gene silencing with shRNA, but not siRNA, may be impaired in cells with low Dicer expression.


CONCLUSIONS
Our findings indicate that levels of Dicer and Drosha mRNA in ovarian-cancer cells have associations with outcomes in patients with ovarian cancer.
Merritt
William M
WM
University of Texas M.D. Anderson Cancer Center, Houston, TX 77230, USA.
Lin
Yvonne G
YG
Han
Liz Y
LY
Kamat
Aparna A
AA
Spannuth
Whitney A
WA
Schmandt
Rosemarie
R
Urbauer
Diana
D
Pennacchio
Len A
LA
Cheng
Jan-Fang
JF
Nick
Alpa M
AM
Deavers
Michael T
MT
Mourad-Zeidan
Alexandra
A
Wang
Hua
H
Mueller
Peter
P
Lenburg
Marc E
ME
Gray
Joe W
JW
Mok
Samuel
S
Birrer
Michael J
MJ
Lopez-Berestein
Gabriel
G
Coleman
Robert L
RL
Bar-Eli
Menashe
M
Sood
Anil K
AK
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D053208:Kaplan-Meier Estimate; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000378:metabolism; D008875:Middle Aged; D015999:Multivariate Analysis; D020125:Mutation, Missense; D009367:Neoplasm Staging; D009375:Neoplasms, Glandular and Epithelial / Q000235:genetics / Q000378:metabolism* / Q000401:mortality; D010051:Ovarian Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000401:mortality; D011379:Prognosis; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism*; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D016896:Treatment Outcome
D035683:MicroRNAs; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D004722:Endoribonucleases; C408087:DICER1 protein, human; C517918:DROSHA protein, human; D043244:Ribonuclease III; D053487:DEAD-box RNA Helicases