[Relevance of cell culture models in cutaneous tumour biology. Part I: tumour cell lines].

Cutaneous squamous cell carcinoma, basal cell carcinoma and melanoma, much like all other human solid tumors, result from a multi-step process in which genetic and epigenetic changes accumulate in the affected cells. Insight into the biology of human tumors is a requirement for developing effective therapies. Cell culture models are a very valuable experimental system. The degree of tumorigenic transformation can be precisely defined. Tumor cell lines display similar functional hierarchy as tumors or tissues in vivo and can, consequently, provide a crucial source of minor cell subsets, like tumor stem cells. Progression series of clonally related cell lines offer the opportunity to follow the process of sequential acquisition of transformation-related traits up to the development of properties with direct clinical equivalents, like tumorigenicity and metastatic competence. These phenotypical changes can be directly correlated with changes at the genome level, concerning both gene structure and expression. While for most studies, human transformed cell lines are the model of choice, there are questions for which animal cell lines are strongly preferred, such as interactions between the tumor and the immune system. To properly interpret the results of all experiments with classical two-dimensional cell culture, a possible danger of artifacts due to grossly unnatural environment must be constantly taken into account. It is thus obligatory to confirm any such result with other experimental models like complex three-dimensional culture models or experimental animals, and with clinical samples.