Characteristics of a tumor cell line and virus derived from hamster tumors induced by rauscher leukemia virus‐transformed hamster embryo cells

A transplantable hamster tumor (RHT‐1) induced by Rauscher leukemia‐virus‐transformed hamster embryo cells was established in tissue culture, and its characteristics were studied. The tumor cell line also contained group‐specific complement‐fixing antigen and continuously released infectious virus. Electron microscope observation showed that this cell line contained C‐type particles. The virus derived from this line served as “helper virus” for a defective Moloney sarcoma virus (MSV) from a non‐infectious hamster tumor (HT‐1), and rescued infectious MSV by direct superinfection of the HT‐1 cells. This infectious MSV virus, which was identified as MSV (RLV) by the focus neutralization test, produced foci readily in both hamster embryo cells and NIH‐METC. Foci produced by this MSV (RLV) pseudotype in hamster embryo cells consisted largely of spindle‐shaped cells which stained vividly with acridine orange. Tumors were produced when cell‐free supernates of MSV (RLV)‐transformed hamster embryo cells, or the cells themselves, were injected into newborn mice. Tumors were also produced when transformed cells were injected into newborn hamsters.