Cellular alterations which influence progression to an anchorage-independent phenotype are poorly understood. Few immortalised keratinocyte lines have been reported to form colonies in semi-solid medium, and the important role of the anchorage-dependence in controlling the behaviour of keratinocytes reflects the resistance of these cells to form colonies in soft agar. We describe here a model for studying in vitro the progression of human papillomavirus type-16 (HPV-16) immortalised keratinocytes from the early stages of immortalisation to an anchorage-independent phenotype. By an extensive selection procedure we have isolated three related cell lines, one immortalised, one weakly anchorage independent and one completely anchorage-independent. The comparison of these three lines gave a clear indication that this in vitro altered growth property is mainly correlated with a deregulation of the epidermal growth factor receptor (ECFR), leading to an increased proliferation rate of the cells coupled with changes in keratin expression.

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