A New Mouse Tumor Model System (RIF-1) for Comparison of End-point Studies

A new tumor model system (RIF-1) was developed that is very suitable for studies in which clonogenic survival is compared with growth delay and control probability following various forms of treatment. The tumor was a radiation-induced sarcoma in the inbred female C3H/Km mouse. It had a low median tumor dose, had a satisfactory plating efficiency direct from in vivo to in vitro, was nonimmunogenic or minimally immunogenic, and metastasized only at a relatively advanced stage of growth. The cell line grew either as a monolayer on plastic dishes, as tumor spheroids in spinner culture, as lung nodules following injection of a single-cell suspension into the tail veins of syngeneic mice, or as a solid tumor. Both diploid and tetraploid clonogenic cells were found in monolayer cultures of the RIF-1 line.