FASN gene expression analysis
Gene expression data and clinical information from patients with PCA were obtained from The Cancer Genome Atlas (TCGA). Using the TCGA network, the differential expressions of FASN in PCA and normal prostate tissue were analyzed. The TCGA-PCA cohort consisted of 496 PCA tissue samples and 52 normal prostate tissue samples. The surgically resected PCA tissue and the non-tumor tissue with detailed clinicopathological parameters were collected from 243 patients who underwent surgical resection in the Affiliated Hospital of Jiangnan University from 2007 to 2018. For all patients, Gleason score (GS) were defined according to the GS systems revised in 1977 and published by the International Association of Urological Pathology (ISUP).
Animals and design
All mice were maintained in an SPF environment at 22 ± 1℃ and relative humidity of 55% ± 10% with a 12 h light-dark cycle. Twelve BALB/C nude mice (male, 6-7 weeks old) were purchased from Beijing Vital River Laboratory Animal Technology Co., Ltd and evenly divided into two groups, one fed with a normal diet (NC, total energy 3.6 kcal g-1, 10% kcal fat) and the other a high PA diet (containing 5% PA) designed and purchased from Trophic (Nantong, Jiangsu, China). A total of 5 × 105 LNCaP cells were subcutaneously injected at left and right armpit site of each mouse. Tumor diameter was measured three times a week, and the size of xenograft tumor was calculated by the following standard formula: length × width2 × 0.5. Mice were sacrificed by neck breaking 4 weeks after injection. After that, the livers and tumors were excised for hematoxylin and eosin staining (H&E staining) and immunohistochemistry.
The c-MycT mice were obtained from the Departments of Medicine, Urology, Molecular and Medical Pharmacology, University of California, Los Angeles[19]. The mice over-express the human c-Myc gene in prostatic epithelium. The PCR primer sequence of the c-MycT gene is 5’ AAACATGATGACTACCAAGCTTGGC 3’ and 5’ TCGAGGTCATAGTTCCTGTTGGTGA 3’. During the 48 weeks period, the control group was fed with normal control feed (NC, total energy 3.6 kcal g-1, 10% kcal fat), while the other groups were fed with a high PA diet (containing 5% PA) designed and purchased from Trophic (Nantong, Jiangsu, China). The body weight of each mouse was measured every two weeks. Mice were sacrificed by neck breaking at the age of 48 weeks, and the anterior, dorsolateral, and ventral prostate (AP, DL and VP) lobes were dissected, photographed, and weighed.
Western blot
Total proteins were extracted from tumor tissue in RIPA lysis buffer containing protease inhibitor and phosphatase inhibitor. Proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and transferred to polyvinylidene fluoride (PVDF) membranes. The membranes were blocked with 5% milk then incubated with primary antibodies at 4°C overnight. The primary antibodies used in the experiment were as follows: TGF-β1 (1:1000; Novus), E-cadherin (1:1000; Cell Signaling Technology), N-cadherin (1:1000; Cell Signaling Technology), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (1:1000; Cell Signaling Technology), FASN (1:1000; Cell Signaling Technology), and vimentin (1:1000; Cell Signaling Technology). After washing with 1 × Tris Buffered Saline with Tween 20 (TBST) three times, the membranes were incubated with horseradish peroxidase (HRP)-conjugated goat anti-rabbit or anti-mouse IgG (1:2000; Abcam). Finally, the membranes were visualized using Immobilon™ Western Chemiluminescent HRP Substrate (Millipore). The protein bands were quantified by ImageJ software.
Immunohistochemistry (IHC)
The paraffin blocks of prostate tissue of patients with PCA were cut into 4 μm slices. The slices were deparaffinized with xylene, dehydrated with ethanol, washed with distilled water, permeabilized in 0.3% Triton X-100 for 20 minutes, and then treated with 0.3% hydrogen peroxide for 30 minutes. Then, the slices were then immersed in boiling citrate buffer solution for 10 minutes in medium and low fire. After cooling, the slices were placed in hydrogen peroxide and blocking solution. Then they were incubated with the primary antibody at 4°C overnight and treated with goat anti-rabbit secondary antibody for 10 minutes. The primary antibodies used in the experiment were as follows: TGF-β1 (1:500; Novus), E-cadherin (1:300; Cell Signaling Technology), N-cadherin (1:400; Cell Signaling Technology). Then, the expression of the target molecule was observed with diaminobenzidine (DAB), and the slides were stained with hematoxylin. After washing in running water, the slides were dehydrated with gradient alcohol and xylene. Finally, the neutral balsam was mounted on the glass slide with a cover glass. Keep the slides in a cool and dry place for one week, and then scanned them with a Pannoramic MIDI slide scanner. ImageJ software was used to measure the positive cell (cells stained with brown) rate.
H&E staining
After deparaffinization and dehydration (these procedures are the same with IHC staining), the slices were stained with hematoxylin for 20 seconds, washed with running water for 15 minutes, and then rapidly immersed in eosin staining solution, 95%, 70% and 80% ethanol for 50 seconds, and then soaked with 100% ethanol for 2 minutes. Next, the slices were incubated with xylene for 2 minutes twice in total. Finally, the neutral balsam was mounted on the glass slide with a cover glass. The slides were kept in the cool and dry place for one week, and then scanned with Pannoramic MIDI slide scanner. Image-Pro Plus 6.0 software was used to measure the area of adipose cells.
Patient survival analysis
Raw counts of RNA-sequencing data (level 3) and corresponding clinical information from PCA were obtained from TCGA database. For Kaplan-Meier curves, P-values and hazard ratios (HRs) with 95% confidence intervals (CIs) were generated by log-rank tests and univariate Cox proportional hazards regression. The Kaplan-Meier survival analysis with log-rank test was used to compare the survival differences between the two groups. For the expression distribution of TGF-β1 in PCA samples, the tumoral RNA-sequence data were downloaded from the Genomic Data Commons (GDC) data portal (TCGA).
Statistical analysis
All results were expressed as the means ± SD using GraphPad Prism 7.0 (La Jolla, California, CA). For two-group analysis, datasets were compared using unpaired two-tailed Student’s t-tests. For the analysis of three or more groups, one-way analysis of variance (ANOVA) was performed. Two-way ANOVA was used to analyze datasets with two independent factors. ImageJ software was used to analyze the results of western blot and IHC staining. The area of adipose cells was measured by Image-Pro Plus 6.0. P < 0.05 was considered to be statistically significant.