Anti-tumor activity of GW572016: a dual tyrosine kinase inhibitor blocks EGF activation of EGFR/erbB2 and downstream Erk1/2 and AKT pathways

Abstract

Dual EGFR/erbB2 inhibition is an attractive therapeutic strategy for epithelial tumors, as ligand-induced erbB2/EGFR heterodimerization triggers potent proliferative and survival signals. Here we show that a small molecule, GW572016, potently inhibits both EGFR and erbB2 tyrosine kinases leading to growth arrest and/or apoptosis in EGFR and erbB2-dependent tumor cell lines. GW572016 markedly reduced tyrosine phosphorylation of EGFR and erbB2, and inhibited activation of Erk1/2 and AKT, downstream effectors of proliferation and cell survival, respectively. Complete inhibition of activated AKT in erbB2 overexpressing cells correlated with a 23-fold increase in apoptosis compared with vehicle controls. EGF, often elevated in cancer patients, did not reverse the inhibitory effects of GW572016. These observations were reproduced in vivo, where GW572016 treatment inhibited activation of EGFR, erbB2, Erk1/2 and AKT in human tumor xenografts. Erk1/2 and AKT represent potential biomarkers to assess the clinical activity of GW572016. Inhibition of activated AKT in EGFR or erbB2-dependent tumors by GW572016 may lead to tumor regressions when used as a monotherapy, or may enhance the anti-tumor activity of chemotherapeutics, since constitutive activation of AKT has been linked to chemo-resistance.

Genome-wide DNA copy number predictors of lapatinib sensitivity in tumor-derived cell lines

“…This is consistent with previous studies demonstrating that lapatinib treatment leads to the inhibition of EGFR and HER2, and consequently results in growth arrest and/or apoptosis in a variety of EGFR and HER2-dependent tumor cell lines (1,30). This is also concordant with the correlation between HER2 expression and the ability of lapatinib to inhibit HER2, Raf, Akt, and Erk phosphorylation in a panel of breast cancer cell lines (2).…”

The efficacy of Herceptin therapies is influenced by the expression of other erbB receptors, their ligands and the activation of downstream signalling proteins

“…Other studies that considered cell lines in culture have shown that indeed not all tumor cells respond to inhibition of ErbB receptors, despite exhibiting aberrant EGFR and/or ErbB2 expression (Motoyama et al, 2002). In this respect, it has been reported that a combination of the EGFR-directed mAb C225 and the erbB2 directed mAb 4D5 or using dual EGFR/HER2 inhibitors inhibited proliferation of tumor cell lines more strongly than either mAb alone (Ye et al, 1999;Motoyama et al, 2002;Xia et al, 2002). A diagnostic protocol for predicting patient response to Herceptin and chemotherapy is presented in Figure 2.…”

Truncated ErbB2 receptor (p95ErbB2) is regulated by heregulin through heterodimer formation with ErbB3 yet remains sensitive to the dual EGFR/ErbB2 kinase inhibitor GW572016

“…Proteins were visualized using fluorescent-labeled secondary Abs and quantified by Odyssey Infrared Imaging System. These results are representative of three independent experiments xenografts (Rusnak et al, 2001;Xia et al, 2002). Although preliminary, GW572016 has shown antitumor activity in early-phase clinical trials in heavily pretreated subjects with metastatic cancers, notably breast cancer (manuscript in preparation).…”

“…In addition, GW572016 inhibited p185 ErbB2 and p95 phosphorylation in S1 cells, a cell line established by single cell cloning of Hb4ac5.2 cells, a nonmalignant mammary epithelial line stably transfected with ErbB2 (Xia et al, 2002). In contrast, p95 was not identified in the EGFR-overexpressing head and neck squamous cell carcinoma line HN5 or in parental Hb4a cells, although exposure to 5 mM GW572016 inhibited phosphorylation of p170 EGFR (lower arrow) and p185 ErbB2 ,respectively (upper arrow).…”