Fig 2: Lipid accumulation and fatty acid uptake in cells. (A) Protein expression of fatty acid transporter 1 (FATP1) and CD36 in PC3 and LNCaP cells was decreased by culture for 24 h in increased concentrations of serum in medium. (B) FATP1 and CD36 expression was increased by x-rays (2 Gy) and C75 (35 μM) in PC3 and LNCaP cells cultured in medium containing 10% serum. Representative blots are shown. Loading control was β-actin. (C) Representative images of lipid droplets in PC3 and LNCaP cells visualized by Oil Red O staining 24 h after culture in medium containing 1% serum with or without oleic acid (100 μM). Bars represent 500 μm. (D) Absorbance of PC3 cells and LNCaP cells exposed to oleic acid for 24 h then stained with Oil Red O. Stain was solubilized with isopropanol. n = 3. (E) 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay of PC3 cells every 24 h after culture in medium containing 1% serum and 100 to 500 μM oleic acid. Data are expressed compared with vehicle treated controls and are means ± standard error of the mean (SEM), n = 4.

Fig 3: Rescue effect of exogenous oleic acid in MCF-7 cells with or without CD36 expression. (A) Anti-proliferation of the SCD1 inhibitor in MCF-7 cells can be rescued by oleic acid-BSA supplementation but not by BSA alone or palmitic acid-BSA. (B) Anti-proliferation of the SCD1 inhibitor in CD36-depleted MCF-7 cells cannot be rescued by oleic acid supplementation. The cell viability was determined using the MTS assay in 3 independent replicates at each dose level. Data represent the mean ± SD of three independent experiments. Error bars represent the SD from the mean. SCD1, stearoyl-CoA desaturase 1; BSA, bovine serum albumin.

Fig 4: CD36 is overexpressed in human CRC. (A,B) Immunoreactivity score of CD36 expression was analyzed in matched normal colon mucosa and tumor tissues from patients diagnosed with Stage I–IV CRC (TMA: n = 56, *p < 0.001 vs. normal tissue). (C) CD36 staining in matched normal colon mucosa, primary CRC, and CRC metastasis to liver and lung [representative images are shown; liver (n = 12) and lung metastasis (n = 5)]. (D) Correlations between FASN and CD36 was determined based on RNASeq data of CRC patient samples (n = 22 of normal tissues and n = 215 of tumors) from The Cancer Genome Atlas. (E) Expression of FASN and CD36 in human normal colon mucosa and tumor tissues. N, normal mucosa; T, primary tumor; L, normal liver tissue; M, liver metastasis.

Fig 5: SSO treatment and CD36 knockdown inhibit tumor growth in vivo. (A) Tumor volume, tumor weight, and mouse weight of control and SSO treated (20 mg/kg) mice are shown. SSO was dissolved in 10% PEG and administered in 200 μl dosages via oral gavage daily. 1.0 × 106 cells were injected into NU/NU mice. Treatment was initiated when tumors reached ~100 mm3 (day 0). (B) RT-PCR analysis of HCT116 tumors showing the effect of SSO treatment on CD36, FASN, and survivin mRNA expression. (C) Tumor volume of HCT116 NTC and CD36 shRNA #2 and #4 xenografts is shown. 1.0 × 106 cells were injected into NU/NU mice and tumor growth was measured every 3 days. (D) H&E and Ki67 staining of HCT116 NTC and CD36 shRNA tumors. (E) Tumor volume and tumor weight of HT29 LuM3 NTC and CD36 shRNA #4 xenografts are shown. (F) mRNA expression of survivin in HT29 LuM3 xenografts (analysis of tumors from 2 mice per group is show).