Anti-invasion, anti-proliferation and anoikis-sensitization activities of lapatinib in nasopharyngeal carcinoma cells

Nasopharyngeal cancer (NPC) is a highly prevalent and invasive head and neck cancer in Asia. Disease recurrence and distant metastasis account for major NPC deaths. Therefore, more effective therapy is needed. Lapatinib, a dual tyrosine kinase inhibitor (TKI) against both EGFR and HER-2, has been known to exert potent antitumor activity against several cancer models. Given that both EGFR and HER-2 are co-expressed in NPC, we hypothesized that dual targeting of EGFR and HER-2 by this small molecule EGFR/HER-2 TKI would elicit anti-tumor activity in NPC. Using in vitro models of NPC, we demonstrated that lapatinib was able to efficiently inhibit the phosphorylation of both EGFR and HER-2. This was accompanied by significant growth inhibition of NPC cells (with maximal growth inhibition >90%). For the most lapatinib-sensitive cell line (HK1-LMP1, with IC₅₀ ∼ 600 nM), which harbored the highest levels of both EGFR and HER-2, inhibition of cell growth was associated G₀/G₁ cell cycle arrest, marked PARP cleavage, caspase-3 cleavage, as well as significant downregulation of several important survival proteins (e.g. survivin, Mcl-1 and cyclin D1). NPC cells are intrinsically invasive. We found that lapatinib was able to inhibit cellular invasion of both HK1-LMP1 and HONE-1 cells. Furthermore, our data demonstrated for the first time that lapatinib harbored potent anoikis-sensitization activity (i.e. sensitizing cancer cells to detachment-induced apoptosis) in human cancer cells overexpressing both EGFR and HER-2 (HK1-LMP1 and HK1). Taken together, our findings suggest that lapatinib is a promising anti-cancer agent for NPC with anti-invasion and anoikis-sensitization activities.