Vitro cultivation of a chemically induced epidermal carcinoma: establishment of three cell lines and isolation of murine leukemia virus

SUMMARY-A squamous cell carcinoma, induced in a BALB/c mouse by 7,12-dimethylbenzla1anthra-cene, was established in tissue culture. The tumor developed into 3 distinct morphologic lines, all of which were malignant. A B-tropic Gross-AKR-type murine leukemia virus was isolated from each line. The char-acteristics of these lines and the possible significance of the leukemia virus in carcinoma induction were discussed.-J Natl Cancer Inst 50: 1561-1570, 1973. CHEMICAL INDUCTION of squamous cell car-cinomas on mouse skin has been a standard experimental model for the study of carcinogenesis. We have been developing an in vitro model system of skin carcinogenesis (J). During these studies, a squamous cell carcinoma induced in a BALB/c mouse by chemical treatment was established in tissue culture. This tumor was cultivated to investigate the morphologic characteristics and the degree of uniformity of malignant epidermal cells in vitro and to delineate specific cell charac-terIstICS, including their ability to maintain differentiation. Through early passage of the carcinoma cells, three distinct morphologic cell lines, all malignant, developed. The biologic behavior of each line and the isolation of murine RNA tumor virus from the carcinoma cells are reported here. MATERIALS AND METHODS Establishment if cell lines.-A large, well-differentiated, infiltrating squamous cell carcinoma was removed from the back of an 18-month-old BALB/c male mouse. At 6 months, this mouse had been painted once with 7,12-dimethylbenz-[aJanthracene (DMBA) at the tumor site; it was treated weekly thereafter with croton oil. Autopsy revealed no other malignancy. Before the aseptic removal of the tumor, the mouse was washed with Phisohex, Betadine, and 70% alcohol, and the tumor was sprayed with Neosporin Aerosol (Burroughs-Wellcome Co., Tuckaho, N.Y.) and coated with Nystatin ointment. After necrotic tissue was trimmed away, the tumor was minced with scissors and dissociated into single cells by repeated treatment with 0.5 % trypsi