Abstract
The mobility of cells from two established cell lines of hamster origin, NIL B and its SV40 virus‐transformant SV‐NIL, was studied in cellular aggregates maintained in agitated liquid medium. Subcutaneous injection of 5×10^6^ NIL B or SV‐NIL cells into Syrian hamsters resulted in a high frequency of tumor formation—1.00 for SV‐NIL cells and 0.93 for NIL B cells. Cells from five different tumors of NIL B origin were grown in tissue culture and their mobility in cellular aggregates was also studied. The mobilities of the tumor‐derived cells were similar to each other and to that of the SV‐NIL cells, but slightly higher than that of the NIL B cells. In addition, the plating efficiency, saturation density and doubling time of NIL B, SV‐NIL and the tumor‐derived cells were determined in conventional fiat culture. No consistent pattern of saturation density or doubling time was observed in the tumor‐derived cells with respect to each other or to the established lines; however, the plating efficiencies of the tumor‐derived cells were all considerably lower than those of NIL B and SV‐NIL cells. It was concluded that selection for the ability to divide and survive in vivo (i.e. to form tumors) was accompanied by a modest increase in cell mobility in vitro.