Effect of heterologous transplantation of H 4-II-E rat hepatoma cells into the cheek pouch of irradiated hamster.

A series of transplant-explant experiments using the H 4-Il-E rat hepatoma cell line and golden hamsters have been carried out. The original tissue culture cells. which had a modal chromosome number of 51, implanted into the cheek pouches of irradiated hamster (400 rads) produced tumors which were typical hepatomas histologically. Cells from these tumors were placed back into tissue culture and were transferred twice more into the cheek pouches of irradiated animals and tissue culture. These were termed the first. second and third selection, respectively. At each stage of selection. chromosome counts, karyotypes and histological and biological characteristics of the cells were determined. The explant from the first selection tumors and that from the second selection tumors were found. to have 53 and 54 chromosome modes. respectively. Two explants derived from separate animals in the third stage of selection each showed different modes of chromosome number (53 and 54). The explants with a modal chromosome number of 54 had a more homogeneous karyotype than those with 53 chromosomes, and the former appeared to be less malignant than the latter. as judged by transplantability, growth rate of the cells in the hydrocortisone treated hamster and the isologous host and histological appearance of the tumors. A possible relationship between cytogenetic variations and biological variations in the cells is discussed.