EGF‐related peptides are involved in the proliferation and survival of MDA‐MB‐468 human breast carcinoma cells

A majority of human breast carcinomas co‐express the epidermal growth factor (EGF)‐like peptides CRIPTO (CR), amphiregulin (AR) and transforming growth factor α (TGF‐α). MDA‐MB‐468 breast carcinoma cells express CR, AR and TGFα, while SK‐BR‐3 cells express CR and TGF‐α. Anti‐sense phosphorothioate oligodeoxynucleotides (AS S‐oligos) directed against either CR or TGF‐α inhibit the proliferation of both cell lines. A 40–50% growth inhibition was observed at a 2‐μM concentration of each AS S‐oligo. Treatment with the AR AS S‐oligo also resulted in a significant inhibition of MDA‐MB‐468 anchorage dependent growth (ADG). No significant growth inhibition was observed when MDA‐MB‐468 or SK‐BR‐3 cells were treated with a mis‐sense S‐oligo. The AS S‐oligos inhibited the expression of AR, CR or TGF‐α proteins and mRNAs, as assessed by immuno‐cytochemistry and semi‐quantitative RT‐PCR. An additive growth‐inhibitory effect was observed when MDA‐MB‐468 cells were treated with a combination of EGF‐related AS S‐oligos. Indeed, treatment of MDA‐MB‐468 cells with a combination of AR, CR and TGF‐α AS S‐oligos resulted in about 70% growth inhibition at a concentration of 0.7 μM each. Finally, treatment of MDA‐MB‐468 cells with a combination either of the 3 AS S‐oligos or of an EGF receptor‐blocking antibody (MAb 225) and either CR, AR or TGFα AS S‐oligos resulted in a significant increase in DNA fragmentation. Our data suggest that the EGF‐related peptides are involved in the proliferation and survival of breast carcinoma cells. Int. J. Cancer 80:589–594, 1999. © 1999 Wiley‐Liss, Inc.