Mitogenic signaling in androgen sensitive and insensitive prostate cancer cell lines

Purpose: To investigate the role of a specific mitogen activated protein ki nase, extracellular signal-regulated kinase (ERK), in regulating cell: prol iferation induced by three potentially important prostate cancer mitogens t hat signal via different classes of receptors. Materials and Methods: Androgen sensitive (LNCaP) and insensitive (PC-3) pr ostate cancer cell lines were used in these studies. Epidermal growth facto r (EGF), lysophosphatidic acid (LPA), and dihydrotestosterone (DHT) were th e mitogenic stimulants and AG1478, a receptor tyrosine kinase inhibitor, an d PD98059, an inhibitor of MEK, were the chemical inhibitors used in this s tudy. Cell proliferation was measured using the WST-1 assay and ERK express ion and activation was determined by immunoblotting for phospho- and total ERK. Results: In androgen-sensitive LNCaP cells, epidermal growth factor (EGF) a nd dihydrotestosterone (DHT) both enhanced cell proliferation. EGF-stimulat ion dramatically increased ERK phosphorylation while DHT did not. In the an drogen-insensitive cell line, PC-3, EGF- and LPA induced ERK phosphorylatio n and cell proliferation. Inhibition of EGF- and LPA- induced ERK activatio n with the EGF receptor inhibitor, AG1478, or the MEK inhibitor, PD98059, a ttenuated their proliferative effects. Neither inhibitor had an effect on D HT stimulated cell proliferation. Conclusions: These data demonstrate heterogeneity of mitogenic signaling in prostate cancer cells, and support the hypothesis that androgens and growt h factors utilize divergent signaling pathways in prostate cancer to induce proliferation.