- Prolonged extracellular signal-regulated kinase 1/2 activation during fibroblast growth factor 1- or heregulin beta1-induced antiestrogen-resistant growth of breast cancer cells is resistant to mitogen-activated protein/extracellular regulated kinase kinase inhibitors. Thottassery, J.V., Sun, Y., Westbrook, L., Rentz, S.S., Manuvakhova, M., Qu, Z., Samuel, S., Upshaw, R., Cunningham, A., Kern, F.G. Cancer Res. (2004)