Characterization of sequences related to the mouse mammary tumor virus that are specific to MCF-7 breast cancer cells.

Mouse mammary tumour virus (MuMTV) DNA hybridized more strongly to two human EcoRI fragments (6.6 and 9.5 kilobases) in DNA from the MCF-7 human breast cancer cell line than in DNA from normal human placenta. Seven recombinants (NMWV 1E1-7) containing these MuMTV-related sequences were identified. Hybridization of NMWV 1E probes to Southern transfers of human DNA suggested that these probes hybridize to multiple sequences in the human genome. The pattern obtained was very similar to that obtained using MuMTV gag-pol DNA. Analysis of the cloned DNA showed that the NMWV 1E MuMTV-related sequences are arranged as tandem repeats and are contained in EcoRI fragments of 6.6 or 9.5 kilobases. Only two NMWV 1E EcoRI fragments (9.5 and 15 kilobases) were detected in 17 DNA samples prepared from human placenta and blood. In contrast the 6.6-kilobase EcoRI fragment was detected in two (MCF-7 and EFM-19) of seven breast cancer cell lines and the MDA MB-231 cell line contained NMWV 1E sequences in an EcoRI fragment of 9.8 kilobases.