A cellular model reflecting the phenotypic heterogeneity of squamous cell carcinoma

Squamous cell carcinomas have a range of histopathological manifestations. The parameters that determine this clinicallly observed heterogeneity are not fully understood. Here, we report the generation of a cell culture model that reflects part of this heterogeneity. Defined genetic elements have been used to progressively immortalize and transform primary UV-unexposed keratinocytes. When injected into immunosuppressed mice, transformed cells grew as xenografts with distinct histopathological characteristics. We observed solid, sarcomatoid and cystic growth types as three major tissue architectures that were primarily composed of pleomorphic and basaloid cells but in some cases displayed focal apocrine differentiation. We demonstrate that generated cells represent different stages of skin cancerogenesis and as such can be used to identify novel tumor-promoting alterations such as the overxepression of the PADI2 oncogene in solid-type SCC. Importantly, cultured cells maintain the characteristics from xenograft they were derived from while being amenable to manipulation and analysis. The availability of cell lines representing different clinical manifestations opens a new avenue to study stochastic and deterministic factors causing case-to-case heterogeneity departing from the same set of oncogenes and the same genetic background. In order to identify potential drivers of skin carcinogenesis we compared the global gene expression pattern of the Ts4 cells derived from a solid-type xenograft with parental (N), transformed (T) and immortal (IM) cell populations. RNA was extracted from 4 biological replicates ofthe cell in cultures, except for Ts4 cells (3 biological replicates).