Effect of solvents on methylcholanthrene-induced carcinogenesis in mice

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Abstract
We have shown previously, with X‐chromosome linked phosphoglycerate kinase (PGK) cell markers, that the fibrosarcomas induced in mice by subcutaneous injection of 0.2–2.0 mg of methylcholanthrene (MCA) dissolved in olive oil had a multicellular origin. In this study we used a constant dose of MCA injected subcutaneously and compared the effects on tumorigenesis of using benzene or olive oil as the solvents. The benzene and olive oil groups differed in tumor incidence (100% versus 50%), location (muscle versus skin), and type (rhabdomyosarcomas versus fibrosarcomas). Each of the nine olive‐oil MCA‐induced tumors showed both PGK enzyme types, whereas 13 of 16 tumors induced by MCA in benzene displayed only a single PGK type. This difference in PGK phenotypes suggests that the MCA‐benzene neoplasms arose from one or a few cells. We conclude from these results that the nature of the solvent plays an important role in the type and number of cells from which tumors induced by subcutaneous injection of MCA arise.