Non-transformed clonal line derived from a mammary tumor of an RIII mouse. Supernatant fluid from these cells was negative for reverse transcriptase activity. Useful for visualization of sarcoma virus-induced foci and for an in vitro quantitative assay for bovine papilloma virus. Host for transfection with plasmids containing bovine papilloma virus DNA. Tested and found negative for ectromelia virus (mousepox).The species was confirmed by Real-Time PCR.