Activity of the Dual Kinase Inhibitor Lapatinib (GW572016) against HER-2-Overexpressing and Trastuzumab-Treated Breast Cancer Cells

Abstract

Lapatinib (GW572016) is a selective inhibitor of both epidermal growth factor receptor (EGFR) and HER-2 tyrosine kinases. Here, we explore the therapeutic potential of lapatinib by testing its effect on tumor cell growth in a panel of 31 characterized human breast cancer cell lines, including trastuzumab-conditioned HER-2-positive cell lines. We further characterize its activity in combination with trastuzumab and analyze whether EGFR and HER-2 expression or changes induced in the activation of EGFR, HER-2, Raf, AKT, or extracellular signal-regulated kinase (ERK) are markers of drug activity. We report that concentration-dependent antiproliferative effects of lapatinib were seen in all breast cancer cell lines tested but varied significantly between individual cell lines with up to 1,000-fold difference in the IC 50 s (range, 0.010-18.6 Mmol/L). Response to lapatinib was significantly correlated with HER-2 expression and its ability to inhibit HER-2, Raf, AKT, and ERK phosphorylation. Long-term in vivo lapatinib studies were conducted with human breast cancer xenografts in athymic mice. Treatment over 77 days resulted in a sustained and significant reduction in xenograft volume compared with untreated controls. For the combination of lapatinib plus trastuzumab, synergistic drug interactions were observed in four different HER-2-overexpressing cell lines. Moreover, lapatinib retained significant in vitro activity against cell lines selected for long-term outgrowth (>9 months) in trastuzumabcontaining (100 Mg/mL) culture medium. These observations provide a clear biological rationale to test lapatinib as a single agent or in combination with trastuzumab in HER-2-overexpressing breast cancer and in patients with clinical resistance to trastuzumab.

Lapatinib, a HER2 tyrosine kinase inhibitor, induces stabilization and accumulation of HER2 and potentiates trastuzumab-dependent cell cytotoxicity

“…On day 19, we sacrificed two animals per group for immunohistochemistry analyses and the experiment continued on the remaining animals until day 23. As expected (Baselga et al, 1998;Konecny et al, 2006), both lapatinib and trastuzumab induced tumor regression of BT474 cell-derived xenografts. All the mice receiving the combination of lapatinib and trastuzumab showed complete tumor remission after 10 days (day 23) of treatment ( Figure 5a).…”

“…Lapatinib, a dual tyrosine kinase inhibitor (TKI) that targets both EGFR and HER2 (Wood et al, 2004;Baselga, 2006), inhibits the growth of HER2-overexpressing breast cancer cells in culture and in tumor xenografts (Chu et al, 2005;Konecny et al, 2006). In the clinic, lapatinib is active and improves time to disease progression in patients with advanced disease who have progressed to trastuzumab (Geyer et al, 2006).…”

“…One such approach would be to give the two agents in combination. In preclinical models, the combination is superior to single drug treatment and enhanced apoptosis has been proposed as a mechanism (Xia et al, 2005;Konecny et al, 2006). In the clinic, a phase III study comparing the efficacy of lapatinib versus the combination of lapatinib and trastuzumab in patients with advanced trastuzumab-resistant HER2-positive breast cancer has shown improved clinical outcome with the combination (O'Shaughnessy et al, 2008).…”

Modular anti‐EGFR and anti‐Her2 targeting of SK‐BR‐3 and BT474 breast cancer cell lines in the presence of ErbB receptor‐specific growth factors

“…Although the EGFR expression level in SK-BR-3 is threefold higher compared to BT474 (7), we found considerable EGFR phosphorylation only in untreated BT474 cells (but to a much lower extent in SK-BR-3) that was efficiently reduced by Lapatinib treatment (Fig. 3B) (12). Evidently, besides Her2 overexpression (12), the basal EGFR phosphorylation rather than the total EGFR expression contributes to sensitivity to Lapatinib treatment (27).…”

“…Trastuzumab could be circumvented to varying degrees by alternate ErbB receptor targeting using, for example, alternate therapeutic antibodies such as Pertuzumab, or tyrosine kinase inhibitors (TKI) such as Lapatinib, or by a combination of antiErbB receptor antibodies and TKIs (12)(13)(14)(15). A number of clinical studies revealed evidence for efficient tumor-cell treatment with Lapatinib [reviewed in Ref.…”