The Tyrphostin B42 inhibits cell proliferation and HER-2 autophosphorylation in cervical carcinoma cell lines
Laboratory of Oncology, Research Unit in Cell Differentiation and Cancer, FES Zaragoza, UNAM, Mexico
AIM: The HER family receptors have an important role controlling cell growth and differentiation. Although the activity of the HER-2 receptor is strictly controlled in normal cells, HER-2 receptor overexpression plays a pivotal role in transformation and tumorigenesis. Constitutive cell surface receptor kinase signaling and persistent phosphorylation of HER-2 protein have been implicated in conferring uncontrolled growth to mammary cancer cells, and to a lesser extent, with adenocarcinoma of uterus, cervix, fallopian tube, and endometrium. Our objective was to clarify the role of HER-2 in cervical carcinoma. METHODS: First, we demonstrated the presence of HER-2 protein expression by flow cytometry on two new cervical carcinoma cell lines CALO and INBL. Second, we used specific tyrosine kinase inhibitors called Thyrphostins to examine HER-2 regulation by the crystal violet assay, a method useful for obtaining quantitative information about the relative density of cells adhering to multi-well cluster dishes. Third, we used western blot analysis for HER-2 phosphorylation determination. RESULTS: The most efficient agent, Tyrphostin B42, known as an inhibitor of ephitelial growth factor receptor, arrested cervical carcinoma cell lines growth in vitro at micromolar concentrations within 72h of application. Tyrphostin B42 inhibited the HER-2 signal-regulated kinase pathway. The latter was observed by the reduction in the phosphorylated forms of HER-2. The loss of phosphorylated forms of HER-2 at early time points after Tyrphostin B42 application was associated with suppression of cell growth and the induction of apoptosis. CONCLUSIONS: Thus, inhibition of cervical carcinoma cell lines proliferation by Tyrphostin B42 is mediated by inhibition of HER-2 protein kinase signal.
Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in oral session 895 (Chemotherapy response).