Differentiation patterns in two- and three-dimensional culture systems of human squamous carcinoma cell lines

Relative quantification of the pattern of differentiation of two squamous carcinoma cell lines of the female genital tract, A431 and CaSki, was studied in various experimental tissue culture states that are frequently used to evaluate drug and radiation effects on human tumors. Two- and three-dimensional in vitro cultures, ie, monolayers and multicellular tumor spheroids (MCTS), and nude mice-xenograft tumors as in vivo tumor models were compared. In addition, epidermal growth factor (EGF) was used comparatively in the in vitro studies. Morphologic signs of epithelial differentiation could be recognized in both cell lines gradually increasing from monolayers to MCTS to xenograft tumors. Cytokeratin (CK) expression is described as stable in A431 cells. Using immunohistochemistry, however, partial masking of CK antigens was found when applying the antibody 8.12 on monolayer cells and could be quantified by flow cytometric measurements. Fundamental cellular changes were found in a CaSki xenograft tumor, which showed newly established features of a keratinizing carcinoma after late onset of tumor growth. Epidermal growth factor caused reduction of both intercellular contacts and later onset of necrosis in MCTS, leading to an increased viability of the spheroids. Significant differences in differentiation of the tumor model systems indicates that the characterization of differentiation with immunohistochemistry and flow cytometry is necessary to assist interpretation of data obtained with these different tumor models.