Molecular effects of the pesticides carbaryl, chlorpyrifos, mancozeb, thiram, and pendimethalin in conditionally normal cells in vitro: genotoxicity, clonogenicity and effects on the expression of genes associated with carcinogenesis

Introduction. Cancer remains a major cause of mortality worldwide, with adverse environmental factors such as pesticides contributing significantly to its development. Despite the widespread use of various pesticides, the molecular mechanisms underlying their actions and carcinogenic potential have been studied for only a limited number of models, especially in normal human cells.
Aim. To study the molecular effects of pesticides carbaryl, chlorpyrifos, mancozeb, thiram, and pendimethalin in nonmalignant HaCaT and MCF10A cells.
Materials and methods. Non-toxic concentrations of pesticides were determined using the MTT assay. Genotoxicity was analyzed by the comet assay. Proliferative potential was assessed by clonogenic assay. Changes in the expression of genes associated with carcinogenesis were evaluated by real-time polymerase chain reaction.
Results. Carbaryl caused DNA damage in MCF10A cells, promoted proliferation in both cell lines during clonogenic assay, as well as caused activation of biotransformation genes (AHR, GSTA4) in MCF10A cells, repression (CYP1B1, GSTA4) genes in HaCaT cells and lowered expression of inflammation genes (IL1a, IL1b, PTGES, IFNGR1). Chlorpyrifos did not have genotoxic effect and did not affect clonogenicity but caused induction of biotransformation (CYP1A1, CYP1B1), inflammation (IL1b, PTGES) genes, and genes BCL2 and DNMTs. Mancozeb and thiram did not show genotoxicity in HaCaT and MCF10A cells but activated individual repair genes (ATR/ATM). Thiram stimulated HaCaT cell proliferation in clonogenic assay, and mancozeb activated expression of proliferation regulation genes (CCND2, CCNE1, Ki-67) but did not affect colony growth; both fungicides decreased expression of inflammation genes (COX2, IL1a, IL1b). Pendimethalin caused DNA damage and activation of repair genes (ATR, GADD45a, PCNA) in both cell lines, as well as decreased expression of GLUT3 in HaCaT cells and induced expression of CYP1A1 in HaCaT cells and CYP1B1 in MCF10A cells.
Conclusion. In this study, we performed a comprehensive assessment of the effects of pesticides on normal human cells. Our results indicate that pendimethalin, chlorpyrifos, and carbaryl exert the most procarcinogenic effect.