Cell Surface Features Associated with Differentiation-Induction of Methylcholanthrene-transformed AKR-2B Fibroblasts by N,N-Dimethylformamide

Methylcholanthrene-transformed AKR-2B mouse embryonal fibroblasts (AKR-MCA cells) were examined for cell surface alterations after growth in culture medium containing N,N-di-methylformamide (DMF) using the lactoperoxidase-glucose oxidase radioiodination procedure with subsequent electrophoresis. DMF has been shown to induce maturational changes in a variety of transformed cells in vitro and has been reported to produce a more normal phenotype when applied to cultured AKR-MCA cells. The electrophoretic profile of ¹²l-lsurface proteins from AKR-MCA cells exhibited a prominent peak of labeled material with a molecular weight of approximately 85,000. After growth of AKR-MCA cells in medium containing DMF, the M_r 85,000 peak was substantially reduced, while there was a large increase in M, 200,000 to 250,000 radbiodinated surface material. This cell surface labeling pattern was virtually identical to that of the nontransformed AKR-2B fibroblasts from which AKR-MCA cells were derived. The cell surface alterations observed upon exposure of AKR-MCA cells to DMF occurred as a function of time of growth in DMF and DMF concentration. Growth of AKR-MCA cells in DMF resulted in a steady increase in cell surface ¹²⁵l incorporation up to the fourth day of exposure to DMF. At this time, the incorporation level was 22.9-fold greater than that for untreated AKR-MCA cells. Incorporation of radiola-bel was decreased after the fifth and sixth days of AKR-MCA exposure to DMF. This trend was also manifested by AKR-2B fibroblasts grown in the presence of DMF. The data suggest that there was increased expression of the M_r 200,000 to 250,000 surface protein on both AKR-2B and AKR-MCA cells when grown in DMF. DMF also inhibited morphological transformation and the cell surface changes associated with transformation of AKR-2B cells by exogenous transforming growth factors.