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Initiation of C3H/10T1/2 cell transformation by N-methyl-N'-nitro-N-nitrosoguanidine and aflatoxin B1
Abstract:
The utility of C3/H/10T1/2 mouse embryo fibroblasts for the detection of carcinogenic substances has been limited by their apparent insensitivity to the oncogenic effects of direct-acting alkylating agents such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and procarcinogens such as aflatoxin B1 (AFB1). Because the process of C3H/10T1/2 transformation can be observed to proceed through discrete stages of initiation and promotion, we have considered the possibility that MNNG and AfB1 may only initiate C3H/10T1/2 transformation. Treatment of asynchronous C3H/10T1/2 cells with MNNG or AfB1 alone generally produced few transformed foci. If MNNG or AfB1 treatment was followed by the exposure of cells to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), numerous transformed foci were produced. Phorbol did not enhance transformation by either substance. MNNG and AfB1 thus appear to be initiating agents for transformation. TPA also enhanced the transformation of C3H/10T1/2 cells by low doses of 3-methylcholanthrene (3-MCA), but transformation by high concentrations of 3-MCA was inhibited by the presence of TPA. These studied suggest that the sensitivity of the C3H/10T1/2 transformation system to potential carcinogens can be dramatically heightened if the bioassay is conducted in the presence and absence of TPA.
Insights
The C3H/10T1/2 cell transformation assay can detect carcinogens more effectively. Adding the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) significantly enhances the detection of initiating carcinogens like MNNG and AFB1.
Area of Science:
- Cell biology
- Toxicology
- Carcinogenesis research
Background:
- The C3H/10T1/2 mouse embryo fibroblast cell line is used for detecting carcinogenic substances.
- Its sensitivity to certain carcinogens, like N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and aflatoxin B1 (AFB1), is limited.
- Cell transformation is understood to involve distinct initiation and promotion stages.
Purpose of the Study:
- To investigate if MNNG and AFB1 act as initiating agents in C3H/10T1/2 cell transformation.
- To determine if the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) can enhance the detection of these carcinogens.
- To assess the effect of TPA on transformation induced by 3-methylcholanthrene (3-MCA).
Main Methods:
- Treatment of asynchronous C3H/10T1/2 cells with MNNG or AFB1 alone.
- Treatment with MNNG or AFB1 followed by exposure to TPA.
- Treatment with varying concentrations of 3-methylcholanthrene (3-MCA) in the presence and absence of TPA.
- Observation and quantification of transformed foci.
Main Results:
- MNNG and AFB1 alone induced minimal transformation.
- Co-treatment with MNNG or AFB1 followed by TPA resulted in numerous transformed foci.
- TPA enhanced transformation by low doses of 3-MCA but inhibited it at high doses.
- Phorbol alone did not enhance transformation.
Conclusions:
- MNNG and AFB1 function as initiating agents in the C3H/10T1/2 cell transformation assay.
- The C3H/10T1/2 transformation system's sensitivity to potential carcinogens can be significantly improved by using TPA.
- This enhanced bioassay protocol allows for more effective detection of initiating carcinogens.