DNA adduct formation in Saccharomyces cerevisiae following exposure to environmental pollutants, as in vivo model for molecular toxicity studies

DNA adduction in the model yeast Saccharomyces cerevisiae was investigated after exposure to the fungicide penconazole and the reference genotoxic compound benzo(a)pyrene, for validating yeasts as a tool for molecular toxicity studies, particularly of environmental pollution. The effect of the toxicants on the yeast's growth kinetics was determined as an indicator of cytotoxicity. Fermentative cultures of S. cerevisiae were exposed to 2 ppm of Penconazole during different phases of growth; while 0.2 and 2 ppm of benzo(a)pyrene were applied to the culture medium before inoculation and on exponential cultures. Exponential respiratory cultures were also exposed to 0.2 ppm of B(a)P for comparison of both metabolisms. Penconazole induced DNA adducts formation in the exponential phase test; DNA adducts showed a peak of 54.93 adducts/109 nucleotides. Benzo(a)pyrene induced the formation of DNA adducts in all the tests carried out; the highest amount of 46.7 adducts/109 nucleotides was obtained in the fermentative cultures after the exponential phase exposure to 0.2 ppm; whereas in the respiratory cultures, 14.6 adducts/109 nucleotides were detected. No cytotoxicity was obtained in any experiment. Our study showed that yeast could be used to analyse DNA adducts as biomarkers of exposure to environmental toxicants.

Rutin and orlistat produce antitumor effects via antioxidant and apoptotic actions

Cancer is a broad term used to describe a large number of diseases characterized by uncontrolled cell proliferation that leads to tumor production. Cancer is associated with mutations in genes controlling proliferation and apoptosis, oxidative stress, fatty acid synthase (FAS) expression, and other mechanisms. Currently, most antineoplastic drugs have severe adverse effects and new effective and safe drugs are needed. This study aims to investigate the possible anticancer activity of rutin and orlistat which are both safely used clinically in humans against two breast cancer models (in vivo EAC and in vitro MCF7) and the pancreatic cancer cell line (PANC-1). Our results have shown that both rutin and orlistat exerted an in vivo anticancer activity as evidenced by the decrease in tumor volume, CEA level, cholesterol content, FAS, and the exerted antioxidant action (reduced MDA level and increased GSH content) and through histopathological examination. In addition, both were cytotoxic to MCF-7 and Panc-1 cell lines by promoting apoptosis. In conclusion, the anticancer activity of rutin and orlistat makes them promising candidates for cancer treatment alone or in combination with other anticancer drugs specially that they are used clinically with an acceptable safety profile.

Effect of metformin and adriamycin on transplantable tumor model

Adriamycin is a cytotoxic anthracycline antibiotic used in treatment of many types of cancer. Metformin is antidiabetic drug and is under investigation for treatment of cancer. The aim of this work was to study the effect of each of adriamycin and metformin alone and in combination on solid Ehrlich carcinoma (SEC) in mice. Eighty BALB/C mice were divided into four equal groups: SEC group, SEC+adriamycin, SEC+metformin, SEC+adriamycin+metformin. Tumor volume, survival rate, tissue catalase, tissue reduced glutathione, tissue malondialdehyde, tissue sphingosine kinase 1 activity, tissue caspase 3 activity and tissue tumor necrosis factor alpha were determined. A part of the tumor was examined for histopathological and immunohistochemical study. Adriamycin or metformin alone or in combination induced significant increase in the survival rate, tissue catalase, reduced glutathione and tissue caspase 3 activity with significant decrease in tumor volume, tissue malondialdehyde, tissue sphingosine kinase 1 activity and tumor necrosis factor alpha and alleviated the histopathological changes with significant increase in Trp53 expression and apoptotic index compared to SEC group. In conclusion, the combination of adriamycin and metformin had a better effect than each of these drugs alone against transplantable tumor model in mice.

[A screen for genes involved in adriamycin resistance in Saccharomyces cerevisiae]

Adriamycin is an anthracycline antibiotic that is widely used in the treatment of various cancers. However, the efficacy of adriamycin-based chemotherapy is compromised by the development of adverse effects and the emergence of adriamycin-resistant cancer cells. In a search for novel mechanisms of resistance to adriamycin, we searched for genes that are related to adriamycin resistance using the budding yeast Saccharomyces cerevisiae and identified several genes (Akl1, Bsd2, Ssl2 and Erg13, etc.). We investigated the role of Akl1, a member of Ark/Prk kinase family, in adriamycin resistance and found that Akl1 might reduce adriamycin toxicity by inhibition of the internalization step in endocytosis via phosphorylation of component of endocytic complex. Furthermore, defects in vesicle trafficking from endoplasmic reticulum (ER) to vacuole reduced the degree of the adriamycin resistance induced by Akl1-overexpression, suggesting that inhibition of internalization step in endocytosis facilitates transport of protein from ER to vacuole, and decreases adriamycin toxicity.