No abstract

Cholangiocarcinoma (CCA), a malignancy of biliary duct with a very poor prognosis, is the leading cause of cancer death in countries of the Mekong subregion. Liver fluke infection is the main etiological factor, but genetic variation has been recognized as also important in conferring susceptibility to CCA risk. Nuclear factor (erythroid derived 2)-like 2 (NRF2) is a key transcription factor in detoxification and antioxidant defense. Emerging evidence has demonstrated that genetic polymorphisms in the NRF2 gene may be associated with cancer development. The objectives of this study were to investigate the association of NRF2 genetic polymorphism with CCA risk and to evaluate the influence of the NRF2 genotype on survival time of affected patients. Single nucleotide polymorphisms (SNPs) of the NRF2 gene, including rs6726395: A/G, rs2886161: C/T, rs1806649: C/T, and rs10183914: C/T, were analyzed using TaqMan ® SNP genotyping assays. Among 158 healthy northeastern Thai subjects, the allele frequencies were 41, 62, 94, and 92%, respectively. The correlation of NRF2 SNPs and CCA risk was analyzed in the 158 healthy subjects and 198 CCA patients, using unconditional logistic regression. The results showed that whereas the NRF2 SNPs were not associated with CCA risk (p>0.05), Kaplan-Meier analysis of 88 intrahepatic CCA patients showed median survival time with rs6726395 genotypes of GG and AA/AG to be 344±138 (95%CI: 73-615) days and 172±37 (95%CI: 100-244) days, respectively, (p<0.006). On multivariate Cox proportional hazard analysis, the GG genotype of rs6726395 was found to be associated with longer survival with a hazard ratio of 0.54 (95%CI: 0.31-0.94). In addition, non-papillary adenocarcinoma was associated with poor survival with a hazard ratio of 2.09 (95%CI: 1.16-3.75). The results suggest that the NRF2 rs6726395 polymorphism can be a potential prognostic biomarker for CCA patients.

Altered expression of a cytosolic flavoenzyme NAD(P)H:quinone oxidoreductase-1 (NQO1) has been seen in many human tumors. Its remarkable overexpression in cholangiocarcinoma (CCA; an aggressive malignancy of the biliary duct system) was associated with poor prognosis and short survival of the patients. Inhibition of NQO1 has been proposed as a potential strategy to improve the efficacy of anticancer drugs in various cancers including CCA. This study investigated novel NQO1 inhibitors and verified the mechanisms of their enzyme inhibition. Among the different chemical classes of natural NQO1 inhibitors are coumarins, flavonoids, and triterpenoids. Coumarins are a group of particularly potent NQO1 inhibitors. The mechanisms and kinetics of enzyme inhibition of coumarin, aesculetin, umbelliferone, and scopoletin using the cell lysates as a source of NQO1 enzyme best fit with an uncompetitive inhibition model. Among the NOQ1 inhibitors tested in KKU-100 CCA cells, scopoletin and umbelliferone had the strongest inhibitory effect on this enzyme, while aesculetin and coumarin barely affected intracellular NQO1. All coumarins were further tested for cytotoxicity and anti-migration activity. At modest cytotoxic doses, scopoletin and umbelliferone greatly inhibited the migration of KKU-100 cells, whereas coumarin and aesculetin barely reduced cell migration. The anti-migration effect of scopoletin was associated with decreased ratio of matrix metalloproteinase 9/tissue inhibitors of metalloproteinases 1 (MMP9/TIMP1) mRNA. These findings suggest that natural compounds with potent inhibitory effect on intracellular NQO1 have useful anti-migration effects on CCA cells. In order to prove that the potent NQO1 inhibitor, scopoletin, is clinically useful in the enhancement of CCA treatment, additional in vivo studies to elucidate the mechanism of these effects are needed.

The endocannabinoid system has been postulated to help restrict cancer progression and maintain osteoblastic function during bone metastasis. Herein, the effects of cannabinoid receptor (CB) type 1 and 2 activation on breast cancer cell and osteoblast interaction were investigated by using ACEA and GW405833 as CB1 and CB2 agonists, respectively. Our results showed that breast cancer cell (MDA-MB-231)-derived conditioned media markedly decreased osteoblast-like UMR-106 cell viability. In contrast, media from MDA-MB-231 cells pre-treated with GW405833 improved UMR-106 cell viability. MDA-MB-231 cells were apparently more susceptible to both CB agonists than UMR-106 cells. Thereafter, we sought to answer the question as to how CB agonists reduced MDA-MB-231 cell virulence. Present data showed that co-activation of CB1 and CB2 exerted cytotoxic effects on MDA-MB-231 cells by increasing apoptotic cell death through suppression of the NF-κB signaling pathway in an ROS-independent mechanism. ACEA or GW405833 alone or in combination also inhibited MDA-MB-231 cell migration. Thus, it can be concluded that the endocannabinoid system is able to provide protection during breast cancer bone metastasis by interfering cancer and bone cell interaction as well as by the direct suppression of cancer cell growth and migration.