This cell line was derived from the HOS cell line (TE-85) by transformation using Kirsten murine sarcoma virus (Ki-MSV). The cells exhibit a high saturation density, a high plating efficiency in soft agar and produce tumors in nude mice. The cells are useful producing MSV pseudotypes with various ecotropic and xenotropic murine leukemia viruses. Cells carry the Ki-MSV genome but do not produce infectious virus particles or viral antigens.