Neoplastic transformation of Chinese hamster cells in vitro after treatment with flavoring agents

Chinese hamster B241 cells were treated with 5 nM allylisothiocyanate (AI) or 10 nM trans-cinnamaldehyde (CA) and surviving cells were cultivated for generations until the cells acquired the characteristics of transformed cells based on in vitro criteria: increase in (a) saturation density in monolayer culture, (b) plating efficiency at low serum level and (c) colony forming efficiency (CFE) in soft agar medium. When the values of CFE of the treated cells had become significantly high, anchorage-independent colonies were isolated, propagated and then subjected to an assay for neoplastic transformation. The anchorage-independent clonal cells (CH-AI-AG+-1 and CH-CA-AG+-2) were subcutaneously injected into a suprascapular site in nude mice. The mice were maintained in an SPF animal care facility and observed for tumor formation. Growth of neoplasm at the injection sites was observed in 6 out of 7 mice and in all of the 6 mice injected with CA- and AI-transformed cells, respectively, during 3 to 8 months after the injection, as compared with 1 out of 6 mice injected with untreated control cells. Subsequent transplantation of the tumor cells into new mice induced tumor production at the injection site in all the animals within a considerably shorter period of time than that following the initial inoculation. Malignancy of the neoplastic cells was ascertained by histological examination, and the cells were found to have karyotypes of the hamster cells after in vitro cultivation of the tumor cells. These experimental results suggest the transforming potency of the flavoring agents in Chinese hamster cells.