Mammary cancer stages in BALB/cV mice: mouse mammary tumor virus expression and virus-host interactions.
A unique subline of BALB/c mice, designated "BALB/cV," exhibits an intermediate mammary tumor incidence (47%) and harbors a distinct milk-transmitted mouse mammary tumor virus (MMTV). Virus expression and virus-host interactions were examined during the different stages of mammary tumorigenesis (normal, preneoplastic, and neoplastic) in the BALB/cV system. Protein immunoblot analyses established the presence of correctly processed (BALB/cV)MMTV structural proteins in all types of BALB/cV mammary tissues. Competition enzyme-linked immunosorbent assays demonstrated that cells from each biologic phenotype were capable of supporting high levels of (BALB/cV)MMTV protein expression. However, mammary epithelial cells that spontaneously underwent the inappropriate pathway of squamous metaplasia did not contain detectable levels of (BALB/cV)MMTV structural proteins. Iodination experiments revealed the presence of a 68K env-related protein on the surface of BALB/cV mammary cells. Nevertheless, sera from 40 mice bearing BALB/cV-positive mammary tissues did not contain detectable levels of anti-env antibodies. Metabolic labeling experiments showed that the half-life of transformation-related, host cell protein p53 (approximately equal to 60 min) in the distinct BALB/cV mammary cell populations was similar to that reported for normal mouse 3T3 cells. It appears that p53 is not stabilized by protein interactions involving any MMTV-encoded or MMTV-induced protein in mammary tumor cells. These characteristics of the BALB/cV system are compatible with the hypothesis that MMTV is only one of two or more cooperating factors required to mediate complete mammary transformation.
D000818:Animals; D000914:Antibodies, Viral / Q000032:analysis; D002454:Cell Differentiation; D004591:Electrophoresis, Polyacrylamide Gel; D008321:Mammary Glands, Animal / Q000382:microbiology; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism / Q000382:microbiology*; D008324:Mammary Tumor Virus, Mouse / Q000276:immunology; D008679:Metaplasia / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D009363:Neoplasm Proteins / Q000032:analysis; D009367:Neoplasm Staging; D010641:Phenotype; D010750:Phosphoproteins / Q000032:analysis; D016159:Tumor Suppressor Protein p53; D014759:Viral Envelope Proteins / Q000276:immunology
D000914:Antibodies, Viral; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D016159:Tumor Suppressor Protein p53; D014759:Viral Envelope Proteins