We have established cell lines from six human squamous cell carcinomas (SCC) of the epidermis and tongue, using culture methods previously developed for clonal growth and serial cultivation of normal keratinocytes. The SCC lines all form rapidly growing, well-differentiated SCC's or progressively growing squamous cysts in nude mice. In contrast to normal keratinocytes, SCC cells form unstratified or very poorly stratifying colonies and do not require epidermal growth factor for sustained growth. The SCC lines vary in their requirement for a fibroblast feeder layer to support clonal growth, from complete independence to a dependence as absolute as normal keratinocytes possess. Only one line forms large, progressively growing colonies at high efficiency in semisolid medium; the other five lines exhibit only a small amount of abortive growth in semisolid medium, after which the cells appear to rapidly degenerate. These results demonstrate that SCC's often grow as established lines in culture, but they frequently possess in vitro growth requirements similar to those of normal keratinocytes. Consequently, neither semisolid medium nor standard surface culture media are appropriate for initiating primary SCC cultures or for selecting transformants out of carcinogen-treated keratinocyte populations, because they do not provide conditions permissive for the growth of many malignant keratinocytes.

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This investigation was supported by the Ellison Foundation, by Massachusetts Division of the American Cancer Society Grant 1492-C, and by National Cancer Institute Grants CA-26656 and CA-19589.

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