BACKGROUND AND OBJECTIVES: All-trans retinoic acid (RA) is a form of vitamin A analogue that has shown chemopreventive activities in many types of malignancy with the properties that regulate cellular differentiations and suppress malignant proliferations. It is thought that the catabolism of RA is mediated by cytochrome P450RAI (CYP26) and its absorption, effects and catabolism are related to cellular retinol binding proteins (CRBP-I and II) and cellular retinoic acid binding proteins (CRABP-I and II). With eight different squamous cell carcinoma cell lines (AMC-HN-1~-8), we investigated the effects of RA and roles of these proteins in the metabolism and regulatory activity of RA. MATERIALS AND METHODS: Survival fractions of eight AMC-HN cells were analyzed six days after the treating them with 1 nM of RA. Reverse transcription-polymerase chain reactions (RT-PCR) were performed before and 24 hours after the load of 1 nM of RA to detect the expressions of CRBP-I, CRABP-I, CRABP-II, and CYP26. RESULTS: Resistances to RA were detected in AMC-HN-1, -2, -5, and -6 cell lines after RA treatment, and AMC-HN-3, -4, -7, and -8 cell lines showed sensitive responses to RA. Before the addition of RA, expressions of CYP26 were detected in AMC-HN-1, -2, -4, -5, -6, and -7 cell lines and CRBP-I was expressed in AMC-HN-3, 4, 5, 7, and -8. After RA addition, the expressions of CYP26 were enhanced in AMC-HN-2, -5, -6, and -7. In six of eight cell lines, CRABP-I was suppressed and CRABP-II was enhanced after RA treatment. CONCLUSION: These results suggest that CYP26 has a direct correlation with the cellular metabolism of RA in the head and neck squamous cell carcinomas and that CRABP-I and CRABP-II have distinct roles in the regulatory effects of RA. CRBP-I might be an indicator that implies the responsiveness to RA.
Absorption ; Carcinoma, Squamous Cell* ; Cell Line ; Cytochromes ; Head* ; Metabolism* ; Neck* ; Receptors, Retinoic Acid ; Retinol-Binding Proteins, Cellular ; Tretinoin* ; Vitamin A

Objective: To explore the effect of down-regulation of retinol binding protein 2 (RBP2) expression on the biological characteristics of ovarian cancer cells and its mechanism. Methods: Knockdown of RBP2 and cisplatin (DDP)-resistant ovarian cancer cell line SKOV3/DDP-RBP2i was established, the negative control group and blank control group were also set. Cell counting kit 8 (CCK-8) was used to detect the cell proliferation ability, flow cytometry was used to detect cell apoptosis, scratch test and Transwell invasion test were used to detect cell migration and invasion ability, real-time fluorescent quantitative polymerase chain reaction (RT-qPCR) and western blot were used to detect the expressions of molecular markers related to epithelial-mesenchymal transition (EMT). The effect of RBP2 on the growth of ovarian cancer was verified through experiment of transplanted tumors in nude mice, and the relationships between RBP2 expression and tumor metastasis and patient prognosis were analyzed using the clinical data of ovarian cancer in TCGA database. Results: After down-regulating the expression of RBP2, the proliferation ability of SKOV3/DDP cell was significantly reduced. On the fifth day, the proliferation activities of SKOV3/DDP-RBP2i group, negative control group and blank control group were (56.67±4.16)%, (84.67±3.51) and (87.00±4.00)% respectively, with statistically significant difference (P<0.001). The apoptosis rate of SKOV3/DDP-RBP2i group was (14.19±1.50)%, higher than (8.77±0.75)% of the negative control group and (7.48±0.52)% of the blank control group (P<0.001). The number of invasive cells of SKOV3/DDP-RBP2i group was (55.20±2.39), lower than (82.60±5.18) and (80.80±7.26) of the negative control group and the blank control group, respectively (P<0.001). The scratch healing rate of SKOV3/DDP-RBP2i group was (28.47±2.72)%, lower than (50.58±4.06)% and (48.92±4.63)% of the negative control group and the blank control group, respectively (P<0.001). The mRNA and protein expressions of E-cadherin in the SKOV3/DDP-RBP2i group were higher than those in the negative control group (P=0.015, P<0.001) and the blank control group (P=0.006, P<0.001). The mRNA and protein expression of N-cadherin in SKOV3/DDP-RBP2i group were lower than those in the negative control group (P=0.012, P<0.001) and the blank control group (P=0.005, P<0.001). The mRNA and protein expressions of vimentin in SKOV3/DDP-RBP2i group were also lower than those in the negative control group (P=0.016, P=0.001) and the blank control group (P=0.011, P=0.001). Five weeks after the cells inoculated into the nude mice, the tumor volume of SKOV3/DDP-RBP2i group, negative control group and blank control group were statistically significant different. The tumor volume of SKOV3/DDP-RBP2i group was smaller than those of negative control group and blank control group (P=0.001). Bioinformatics analysis showed that the expression of RBP2 in patients with metastatic ovarian cancer was higher than that without metastasis (P=0.043), and the median overall survival of ovarian cancer patients with high RBP2 expression was 41 months, shorter than 69 months of low RBP2 expression patients (P<0.001). Conclusion: Downregulation of the expression of RBP2 in SKOV3/DDP cells can inhibit cell migration and invasion, and the mechanism may be related to the inhibition of EMT.
Animals ; Apoptosis ; Carcinoma, Ovarian Epithelial/genetics* ; Cell Line, Tumor ; Cell Proliferation ; Cisplatin/pharmacology* ; Drug Resistance, Neoplasm/genetics* ; Female ; Gene Silencing ; Humans ; Mice ; Mice, Nude ; Ovarian Neoplasms/pathology* ; Retinol-Binding Proteins, Cellular/metabolism*

Retinoids regulate not only various cell functions including proliferation and differentiation but also glucose and lipid metabolism. After we observed a marked up-regulation of cellular retinol-binding protein-I (CRBP-I) in the liver of hepatitis B virus x antigen (HBx)-transgenic (HBx Tg) mice which are prone to hepatocellular carcinoma (HCC) and fatty liver, we aimed to evaluate retinoid pathway, including genes for the retinoid physiology, CRBP-I protein expression, and retinoid levels, in the liver of HBx Tg mice. We also assessed the effect of chronic metformin treatment on HCC development in the mice. Many genes involved in hepatic retinoid physiology, including CRBP-I, were altered and the tissue levels of retinol and all-trans retinoic acid (ATRA) were elevated in the liver of HBx Tg mice compared to those of wild type (WT) control mice. CRBP-I protein expression in liver, but not in white adipose tissue, of HBx Tg mice was significantly elevated compared to WT control mice while CRBP-I protein expressions in the liver and WAT of high-fat fed obese and db/db mice were comparable to WT control mice. Chronic treatment of HBx Tg mice with metformin did not affect the incidence of HCC, but slightly increased hepatic CRBP-I level. In conclusion, hepatic CRBP-I level was markedly up-regulated in HCC-prone HBx Tg mice and neither hepatic CRBP-I nor the development of HCC was suppressed by metformin treatment.
Adipose Tissue, White ; Animals ; Carcinoma, Hepatocellular* ; Fatty Liver ; Hepatitis B virus ; Incidence ; Lipid Metabolism ; Liver* ; Metformin* ; Mice ; Mice, Transgenic* ; Retinoids ; Retinol-Binding Proteins, Cellular* ; Trans-Activators ; Tretinoin ; Up-Regulation ; Vitamin A