We have reported that the frequency of induction of the morphologically transformed phenotype in early passage Syrian hamster embryo cells is increased in carcinogen-treated cultures when the cells are cultured in media of pH 6.70, instead of the traditionally used pH 7.35. The purpose of the studies reported here was to determine the neoplastic potential of cells derived from colonies of morphologically normal, altered, and transformed phenotypes from untreated and carcinogen-treated cultures generated under low pH conditions. Results from these studies indicate that cells derived from morphologically transformed colonies generated at pH 6.70 following benzo[a]pyrene or 3-methylcholanthrene treatment became established as immortal cell lines with a frequency of 30 and 14%, respectively. In contrast, cells derived from morphologically transformed colonies in untreated cultures and morphologically normal colonies from carcinogen-treated cultures establish as immortal cell lines at a frequency of 3% or less. Acquisition of aneuploidy was associated with immortalization in most cell lines. Ninety-two % of the immortal lines eventually progressed to the neoplastic phenotype upon subsequent cell culture, as assessed by cell injection into newborn hamsters. Approximately 75% of the neoplastic cell lines exhibited anchorage-independent growth in agarose. A comparison of these results to those generated at pH 7.35 by other investigators indicates that pH 6.70 culture of SHE cells is primarily enhancing early stages of the transformation process, i.e., induction of morphological transformation, while the frequency of progression from the morphologically transformed phenotype to neoplasia appears similar between the two pH values. These results support earlier indications that pH 6.70 culture of SHE cell is a useful model system for the study of multistage carcinogenesis.

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