Screening of genotoxicity and mutagenicity in extractable organics from oil sands process-affected water.

Large volumes of oil sands process-affected water (OSPW) are produced by the oil sands surface mining industry during alkaline hot-water extraction of bitumen. It is well documented that the acid extractable organics (AEOs) in OSPW, a highly complex mixture of acidic and polar neutral substances, are acutely toxic; but few studies have examined the genotoxicity or mutagenicity of this mixture. In the present study, the in vitro SOS Chromotest and the Ames test (TA98 and TA100 strains) were used to evaluate genotoxicity and mutagenicity for whole OSPW AEOs in the presence and absence of biotransformation by rat S9 liver enzymes. Two subfractions were also examined in the same assays: neutral extractable fraction (F1-NE), and the subsequent acid extractable fraction (F2-AE). In the SOS assay, whole AEO was cytotoxic when concentrated 2× (i.e., twice as concentrated as the environmental sample) and showed increasing genotoxic response above 6×. Co-exposure with S9 had a protective effect on the cell SOS-inducing factor and survival but did not eliminate genotoxicity above 6× concentrations. Most of the cytotoxicity was attributable to F2-AE, but both F1-NE and F2-AE had similar genotoxic dose-responses above 6×. In the Ames test without S9, whole AEO was mutagenic in both strains above 10× concentrations. Co-incubation with S9 had little effect on the TA100 strain but with TA98 resulted in bioactivation at midlevel doses (1.5-6.3×) and protection at higher doses (10-25×). The 2 subfractions were mutagenic in both strains but with different dose-responses. Further research in vivo or in more relevant cells is warranted to investigate the carcinogenic risks of OSPW. Environ Toxicol Chem 2017;36:1397-1404. © 2016 SETAC.

Differential SIRT1 expression in hepatocellular carcinomas and cholangiocarcinoma of the liver.

Hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) are two major liver malignancies. Although some phenotypic overlap is known, HCC and CCA are usually different with regard to etiology, histology, and prognosis. Gene expression and deacetylase activity of the class III histone deacetylase SIRT1 are up-regulated in cancer cells due to oncogene overexpression or loss of function of tumor suppressor genes. SIRT1 may play a critical role in tumor initiation, progression, and drug resistance by blocking senescence and apoptosis, and promoting cell growth and angiogenesis, but pleiotropic effects (synchronous or metachronous anti-proliferation and anti-apoptotic mechanisms) have been suggested in some cancers. Our aim was to investigate the expression of SIRT1 in liver epithelial malignancies. Thirty carcinomas of the liver, including 16 HCC and 14 CCA cases, were investigated by immunohistochemistry using monoclonal antibodies against SIRT1 and p53. Western blot analysis (WBA) was carried out for expression of SIRT1 in three CCA cell lines, one HCC cell line, and one cell line of Papova-immortalized normal hepatocytes. An expression of SIRT1 was found in 11 of 16 (68.75%) HCC and in 5 of 14 (35.71%) CCA. Moreover, we found an expression of p53 in 8 out of 16 (50%) HCC and 13 out of 14 (92.86%) CCA. WBA showed expression of SIRT1 in all cell lines studied, although a stronger signal was seen in the HCC cell line. Immunohistochemical data did not correlate to clinical stage or other clinical or histopathological parameters. Sirtuin 1 is a phylogenetically-conserved family of deacetylases and our data seem to indicate that (1) pleiotropic effects may be present in hepatic epithelial malignancies, and (2) there is no specificity of SIRT1 for either HCC or CCA.