Tumor-associated antigen expression and growth requirements predict tumorigenesis in squamous cell carcinoma

Squamous cell carcinomas (SCCs) are the most common malignancies in man. Wh ile clinical specimens are theoretically ideal to study tumor development a nd progression, practical difficulties such as normal cell contamination, t he presence of different cell types, and limited material make preclinical studies of model systems involving a homogeneous population of normal or tr ansformed cells preferable. Tumor-associated antigens (TAAs) found on the c ell surface, including integrins, mucins, cadherins, growth factor receptor s, membrane bound antigens, and glycoproteins are known to play an importan t role in squamous carcinogenesis. We hypothesized that (1) alterations in TAA expression in vitro predict in vivo alterations, (2) analysis of a grou p of TA-ks would provide a better indication of SCC tumorigenesis than any single marker, and (3.) SCCs, with independence from exogenous growth facto rs in vitro would demonstrate the most aggressive growth in vivo. The cell line which grew best in vitro without serum or other supplements demonstrat ed the most rapid tumor growth, whereas cell tines which grew only with sup plements rarely formed tumors. Normal keratinocytes, eight SCC and two immo rtal keratinocyte cell lines were evaluated by flow cytometry for the expre ssion of 10 cell surface markers, including alpha and beta integrins, minor blood group-related carbohydrate determinants, carcinoembryonic antigen-re lated proteins. E-cadherin, and GA733 (epithelial glycoprotein, epithelial cell adhesion molecule). None of the cell lines with abnormal expression of less than or equal to2 markers formed tumors, whereas all lines with alter ed expression of greater than or equal to3 markers formed tumors. Using GA7 33 expression as an example, we found that altered TAA expression in vitro predicted the presence of TAA alterations in clinical specimens. In summary , in vitro independence from supplements for optimal growth and altered exp ression of greater than or equal to3 cell surface markers were good predict ors of SCC tumorigenesis. These findings, may be useful in decreasing the n eed for whole animal tumorigenicity experiments.