Induced Differentiation of Epithelioid Carcinoma Cell Lines: Evidence for Tumor Cell Quantal Mitosis

Abstract

The effect s of growth factors and calcium concentrations present in different culture media on induction of terminal differentiation were investigated for four different epidermoid carcinoma cell lines, Hela, KB, A431, and SCC - 25, and their responses determined relative to those elicited by normal human keratinocytes subjected to these culture conditions. Differentiation status was determined cyto-chemically by a validated keratin protein staining method, and by autoradiographic analyses. Growth and differentiation promoting factors that influence d the direction of integrated control of growth and differentiation in normal human keratinocytes were found to be effective for some cell lines but not others. The factors examined were 1) high density arrest in serum-free and serum-containing media, 2) media shifts from high density culture in serum-containing media to low density growth factor-depleted or supplemented serum-free medium, and 3) the concentration of calcium in the media. The extent and degree of differentiation achieved varied among different cell lines depend on the presence or absence of serum, EGF and insulin protein growth fac tors. Certain growth media appear to sponsor keratin protein , cyto-chemically- detected differentiation , and evidence of quantal mitotic division in low density HeLa cell and SCC25 cell cultures. Epidermoid carcinoma cell lines retain limited capacity to commit to early stages of cell differentiation.