Tumorigenic Conversion of in vivo Differentiation Competent Mammary Cells by Introduction and Expression of ras or mil(raf) but not myc

Mammary cancer affects around 9% of women and is the most frequent cause of death in women aged between 40 to 54 years old (Miller and Bulbrook, 1986). Whilst the mechanisms involved in mammary tumorigene fs are not understood, there is evidence for the existence of a human mammary tumour virus that is related to the Mouse Mammary Tumour Virus (MMTV) (Schlom et al., 1971; Crepin et al., 1984; Keydar et al., 1984; Ono et al., 1986; Ono et al., 1987; Franklin et al., 1988). Additionally, a number of oncogenes have been implicated in the tumorigenic process. Elevated expression and/or amplification of the oncogenes ras, myc and neu have been correlated with human mammary tumorigenesis (Horan-Hand et al., 1984; DeBortoli et al., 1985; Ohuchi et al., 1986; Kraus et al., 1984; King et al., 1985; Slamon et al., 1987; Kozbor and Croces, 1984; Escot et al., 1986; Varley et al., 1987).