Infection of cultured rat hepatoma cells by mouse mammary tumor virus.

A continuous line of buffalo rat hepatoma (HTC) cells has been successfully infected with mouse mammary tumor virus (MMTV) produced by the GR mammary tumor cell line. Uniform infection required initial exposure of the HTC cells to greater than 10(5) MMTV particles per cell. The resultant chronically infected cell population was found to have stably acquired 20-30 copies of MMTV DNA. The infected cells contain viral RNA and express viral antigens; however, very few MMTV particles are released into the culture medium. In spite of the biochemical evidence for infection, we have not detected any alterations in the morphology or growth properties of the infected HTC cells. As is the case in mammary tumor cells, the intracellular concentration of viral RNA is strongly stimulated (50-150 fold) by the synthetic glucorcorticoid, dexamethasone. Thus it appears that the mechanisms by which glucorticoids regulate MMTV gene expression in mouse cells are maintained when this virus infects nonmurine cells.