A majority of MCA-induced sarcoma cell lines derived from RAG2^−/−x γc^−/− mice cannot form tumors when transplanted into syngeneic WT mice. MCA-induced sarcoma cell lines were derived from tumors generated in syngeneic C57BL/6-strain WT, RAG2^−/−, and RAG2^−/−x γc^−/− mice. These cell lines were transplanted into syngeneic RAG2^−/− (n ≥ 2 for each cell line) or WT (n ≥ 5 for each cell line) hosts, and tumor growth was measured over time. (A) The mean growth for each cell line is shown (open symbols = regressor cell lines; closed symbols = progressor cell lines). (B) The percentage of WT mice that developed tumors is shown for group of cell lines. Tumor-free mice were defined as having a nonenlarging mass <9 mm in average diameter. The number of cell lines and mice are indicated in the figure.