Characteristics of chemically transformed mouse epidermal cells in vitro and in vivo.

Primary cultures of epidermal cells from newborn mouse skin have been established. These cultures proliferate and express typical epidermal functions for limited time in vitro. The cultured cells keratinize and exhibit strong reactivity with an epidermis specific membrane antiserum. These cells can be transformed with DMBA either in standard cultures or more easily in cultures using 3T3 feeder cells. Transformed cells have increased proliferation rate. They do not pile up or form multilayered cultures like normal counterparts. They also keratinize less. When transformed cells were grown in the air on collagen gels they formed irregular clumps with central (horn-pearl) keratinization whereas normal controls formed stratified structures. Transofmred cells exhibited reduced reactivity with tissue specific membrane antiserum. There was masking or rearrangement of tissue specific membrane antigens with simultaneous exposition of new fetal-like antigens. Their reactivity with histocompatibility antisera was only slightly reduced. Transformed cells had both numerical and structural chromosome aberrations. They grew in soft agar and they induced tumors upon transplantation in the convenient host. When transplanted as cultures (on collagen) or as suspensions into the host, transformed cells were able to form epithelial cell cords invading the underlying mesenchyme with histological aspect typical of carcinoma. Cell cultures derived from in vivo DMBA induced tumors behaved like in vitro transformed cells.