Establishment and cell cycle kinetics of a human squamous cell carcinoma in nude mice and in vitro

A human squamous cell carcinoma of the virus was xenografted to athymic, nude mice. A tissue culture cell line designated SqCaVu-1H was derived from a second-passage xenograft. The growth characteristics and cell cycle kinetics in the xenografts and in SqCaVu-1H cells were compared. Approximately 80% of the tumor implants produced growing xenografts which had a 2-week latent period followed by Gompertzian growth with a doubling time of 5 to 30 days at 35 days postimplantation. The cell cycle kinetics of the xenografts revealed a heterogeneity from region to region within the tumor. G2 phase and S phase in the xenografts are approximately 8 and 13 hr, respectively. The SqCaVu-1H cells contain only human chromosomes. The modal chromosome number was 64. SqCaVu-1H cells produce plasminogen activator during logarithmic growth, and they produce tumors when injected s.c. into athymic, nude mice. Logarithmically growing SqCaVu-1H cells have a population-doubling time of 21.8 hr in tissue culture. In vitro, their cell cycle duration is approximately 16.0 hr, with G2 phase at 5.6 hr and S phase at 8.6 hr. Comparison of the growth of the same human tumor cells under in vivo and in vitro conditions serves to emphasize that tumor cell proliferation depends strongly on the microenvironment. The varied proliferation characteristics are correlated with their varied inhibition of deoxyuridine incorporation into DNA because of exposure to methotrexate. Logarithmically growing SqVaCu-1H cells had a 50% inhibitory dose of 2.2 X 10(-6) M. Plateau-phase cells in vitro had a 50% inhibitory dose of 9 X 10(-6) M, while the inhibition of cells from the xenografts was nearly dose independent.