Detection of hepatocarcinogens by combination of liver micronucleus assay and histopathological examination in 2-week or 4-week repeated dose studies

Background Currently, revisions to the ICH S1 guidance on rodent carcinogenicity testing are being proposed. Application of this approach would reduce the use of animals in accordance with the 3Rs principles (reduce/refine/replace). The method would also shift resources to focus on more scientific mechanism-based carcinogenicity assessments and promote safe and ethical development of new small molecule pharmaceuticals. In the revised draft, findings such as cellular hypertrophy, diffuse and/or focal cellular hyperplasia, persistent tissue injury and/or chronic inflammation, preneoplastic changes, and tumors are listed as histopathology findings of particular interest for identifying carcinogenic potential. In order to predict hepatocarcinogenicity of test chemicals based on the results from 2- or 4-week repeated dose studies, we retrospectively reanalyzed the results of a previous collaborative study on the liver micronucleus assay. We focused on liver micronucleus induction in combination with histopathological changes including hypertrophy, proliferation of oval cells or bile duct epithelial cells, tissue injuries, regenerative changes, and inflammatory changes as the early responses of hepatocarcinogenesis. For these early responses, A total of 20 carcinogens, including 14 genotoxic hepatocarcinogens (Group A) and 6 non-liver-targeted genotoxic carcinogens (Group B) were evaluated. Results In the Group A chemicals, 5 chemicals (NPYR, MDA, NDPA, 2,6-DNT, and NMOR) showed all of the 6 early responses in hepatocarcinogenesis. Five chemicals (DMN, 2,4-DNT, QUN, 2-AAF, and TAA) showed 4 responses, and 4 chemicals (DAB, 2-NP, MCT, and Sudan I) showed 3 responses. All chemicals exhibited at least 3 early responses. Contrarily, in the Group B chemicals (6 chemicals), 3 of the 6 early responses were observed in 1 chemical (MNNG). No more than two responses were observed in 3 chemicals (MMC, MMS, and KA), and no responses were observed in 2 chemicals (CP and KBrO3). Conclusion Evaluation of liver micronucleus induction in combination with histopathological examination is useful for detecting hepatocarcinogens. This assay takes much less time than routine long-term carcinogenicity studies.

Genotoxicity evaluation of Chlorfenapyr in exposed freshwater African catfish Clarias gariepinus using micronucleus test

Chlorfenapyr is a new formulated insecticide targeted against insecticide resistant species. Its application in targeting harmful aquatic insects may potentially contaminate aquatic environment. This study is to evaluate its genotoxic effects on non-targeted aquatic biota. The study assessed the genotoxic potentials of chlorfenapyr in African catfish (Clarias gariepinus) using the micronucleus (MN) test. Juvenile stage of C. gariepinus were exposed to different concentrations; 5.00 – 15.00 mgL-1 of chlorfenapyr for 96 hours, peripheral blood was collected through the caudal vein and examined for micronucleus induction in the erythrocytes. The tested concentrations of chlorfenapyr did not elicit significant [F (5, 18) = 0.167, p 0.971] increase in MN formation and other nuclear abnormalities in the peripheral erythrocytes of C. gariepinus. The outcome of this study gives credence to the view that chlorfenapyr is not clastogenic and or aneugenic to non-targeted aquatic vertebrate with reference to fish (C. gariepinus).

Anticancer Potential of Lepidium Sativum Seeds Aqueous Extract on the Azoxymethane/ Dextran Sulfate Sodium-Induced Colon Cancer In vivo

Background:: Colon cancer is responsible for increasing death rate worldwide. Commonly used anticancer drugs have various side effects and their clinical usage must be limited due to their toxicity. Objective:: The present research aimed to evaluate the anticancer potential of Lepidium sativum L. (LS) seeds aqueous extract against azoxymethane/dextran sodium sulfate (AOM/DSS) induced-colon cancer in male albino mice. Methods:: Low (200 mg/kg) and high (400 mg/kg) doses of LS seeds extract were used in treatment of induced colon cancer in different grades. Results:: The present results report that LS treatment for colon cancer mice, especially the high dose, decreases colon polyps/tumor incidence and size, tissues disorder, expression of P53 and increases apoptosis in colon tissue. Moreover, LS decreases micronucleus induction in polychromatic (PCE), increases PCE/normochromatic erythrocytes ratio and decreases the percentage of sperm abnormalities. Conclusion:: The present study reports LS anticancer potential for induced colorectal cancer mice by ameliorating the inflammatory steps of colon.