Changes in growth pattern of human squamous-cell carcinomas of the head and neck during serial passages in nude mice.

Six human squamous-cell carcinomas of the head and neck heterotransplanted to nude mice were studied with respect to changes in tumour volume doubling time (DT), cell cycle phase distribution and clonal composition during serial passages. The tumours exhibited a statistically significant decrease in DT between the first and third or fourth passages towards a constant value. The changes in DT are likely to depend on a reduction of cell loss factor. Five of the original tumours and serially passed heterotransplants were analyzed with flow cytometry. Two tumours were diploid and remained so after heterotransplantation. Three tumours had one diploid and one aneuploid cell population. At heterotransplantation there was a selection of clones and only the aneuploid cell populations could be recovered from the heterotransplants in the first as well as in later passages.