Cell culture.
The ovarian cancer cell lines SKOV3, A2780 was purchased from The European Collection of Authenticated Cell Cultures (ECACC), were grown in Dulbecco’s modified Eagle’s medium (DMEM, Invitrogen, Carlsbad, CA, USA) supplemented with 10% fetal bovine serum (FBS, Invitrogen), at 37°C in a 5% CO2 atmosphere in a humidified incubator. The CDDP resistant cell line A2780/cis was grown in 10% FBS RPMI 1640 (2mM Glutamine + 1µM cisplatin), at 37°C in a 5% CO2 atmosphere in a humidified incubator. All cell lines were authenticated by short tandem repeat (STR) fingerprinting.
Patient information and tissue specimens.
A total of184 paraffin-embedded and archived ovarian cancer samples were examined in this study. Clinical information on the samples is summarized in Supplementary Table 1. All tums were staged according to the International Federation of Gynaecology and Obstetrics standards (FIGO). Ten freshly collected ovarian cancer tissues were frozen and stored in liquid nitrogen until further use. Prior patient consent and approval from the Institutional Research Ethics Committee were obtained for the use of these clinical materials for research purposes.
Vectors, retroviral infection and transfection.
The human FAM46A gene was PCR-amplified from cDNA and cloned into pMSCV retroviral vector (Clontech, Mountain View, CA). ShRNAs targeting FAM46A were cloned into the pSuper-retro viral vector. Transfection of plasmids was performed using the Lipofectamine 3000 reagent (Invitrogen, Carlsbad, CA) according to the manufacturer’s instruction. Stable cell lines expressing FAM46A and FAM46A shRNA(s) were generated via retroviral infection using HEK293T cells as previously described and selected with 0.5 μg/ml puromycin for 10 days.
Western blotting (WB) analysis. WB was performed using anti-FAM46A antibody (Abcam), anti-p-Smad2 (Ser465/467), total Smad2 and anti-β-catenin antibodies, anti-cleaved caspase 3, anti- cleaved PARP antibodies (Cell Signaling). The blotting membranes were stripped and re-probed with an anti-α-tubulin antibody as a protein loading control (Sigma).
Xenografted tumor model, IHC, and H&E staining.
In the intraperitoneal tumor model, the BALB/c nude mice were randomly divided into four groups (n = 5/group). Four groups of mice were inoculated intraperitoneal with 2×106 A2780-Vector, A2780- FAM46A, A2780-cis/shRNA-Vector, A2780-cis/ FAM46A -shRNA#1 cells, respectively treated with CDDP (5 mg/kg) every 4 days for 35 days. Tumors were detected by an IVIS imaging system twice a week. Survival was evaluated from the first day of treatment initiation until death and tumors were excised and paraffin-embedded. Apoptotic index was measured by percentage of TUNEL-positive and active caspase 3-positive cells.
Cytotoxicity assay.
The sensitivity to cisplatin of ovarian cancer cells was determined using the MTT assay. Briefly, 2 × 103 cells were seeded onto 96-well plates and incubated at 37°C overnight. Cells were then transfected with different concentrations of cisplatin (0-200 μM). After incubation for 72 hours, 50 μl of the MTT solution (0.15%) was added to each well, and the plates were further incubated for 2 hours. One hundred microliters of DMSO was added to solubilize the MTT formazan product. Absorbance at 540 nm was measured with a Falcon microplate reader (BD-Labware). Dose-response curves were plotted on a semilog scale as the percentage of the control cell number, which was obtained from the sample with no drug exposure. IC50 was determined by the intersection of the cisplatin concentration and the midpoint of the 570-nm reading.
Apoptosis assay.
For evaluation of apoptosis, PE Annexin V Apoptosis Detection Kit I (BD Pharmingen) was used. Briefly, 1×106 ovarian cancer cells were plated in 10-cm plates and incubated for 24 hours. Treatment was started with cisplatin (10 μM) for 24 hours. Cell morphology was assessed by phase-contrast microscopy. Then, cells were removed from plate by trypsin-EDTA, washed twice with PBS, and resuspended with binding buffer at 106 cells/ml. FITC Annexin V and propidium iodide were added (each at 5 μl/105 cells). Cells were incubated for 15 minutes at room temperature in the dark. Percentage of apoptosis was analyzed with an EPICS XL flow cytometer (Beckman-Coulter). Each sample was analyzed in triplicate.
Transient Luciferase Assay
Cells (1x104) were seeded in triplicate in 48-well plates and allowed to settle for 24 h. For each transfection, one hundred nanograms of luciferase reporter plasmids pGL-3-FAM46A or vector and 5 ng of pRL-TK, expressing Renilla luciferase as an internal control, were transfected into cells using the Lipofectamine 3000 reagent (Invitrogen) according to the manufacturer’s instruction. 48h after transfection, cells were harvested and Luciferase and renilla signals were measured using the Dual Luciferase Reporter Assay Kit (Promega) according to a protocol provided by the manufacturer. The luciferase activity was normalized by the Renilla luciferase activity of each transfection to normalize the transfection efficiency. Three independent experiments were performed, and the data are presented as mean ± SD.
Nuclear and Cytoplasmic Extraction assay. Nuclear fractions were prepared by using the nuclear extraction kit (Active Motif, Carlsbad, CA). Briefly, after drug treatment, cells were pelleted and lysed by vigorous vortex in hypotonic buffer for 15 min. The samples were then centrifuged at 14,000 × g for 1 min; the supernatant was considered cytoplasmic. Insoluble pellets were further lysed in complete lysis buffer for 30 min, and nuclear extracts (supernatant) were collected after a 10-min centrifugation at 14,000 × g. Both cytoplasmic and nuclear fractions were quantified and subjected to Western blot analysis.
Chemical reagents. Cisplatin (Sigma, Saint Louis, MO) were dissolved in PBS with concentration of 50 uM. TGF-β inhibitor (LY2109761) were purchased from Santa Cruz Biotechnology (Dallas, TX).
Statistical analysis. Statistical tests for data analysis included Fisher’s exact test, log-rank test, Chi-square test, and Student’s 2-tailed t test. Multivariate statistical analysis was performed using a Cox regression model. Statistical analyses were performed using the SPSS 21.0 statistical software package. Data represent mean ± SD. P < 0.05 was considered statistically significant.
Microarray data process and visualization.
Microarray data were downloaded from the GEO database: (http://www.ncbi.nlm.nih.gov/geo/).
GSEA was performed using GSEA 2.0.9 :( http://www.broadinstitute.org/gsea/).