Erlotinib Antitumor Activity in Non-small Cell Lung Cancer Models is Independent of HER1 and HER2 Overexpression

Abstract

Background: The human epidermal growth factor receptors HER1/EGFR and HER2 offer potential targets for treating non-small cell lung cancer (NSCLC). The antitumor efficacy of erlotinib (Tarceva, F. Hoffmann-La Roche, Ltd., Basel, Switzerland), a HER1/EGFR tyrosine-kinase inhibitor, was investigated in relation to HER1/EGFR and HER2 expression in five NSCLC xenograft models. Materials and Methods: Tumor-bearing mice were randomized to daily oral erlotinib, 50 mg/kg, or vehicle (controls) for 20-50 days. The antitumor efficacy of erlotinib was measured through tumor volume, serum tumor markers and tumor biomarkers. Tumor HER1/EGFR and HER2 expression were analyzed immunohistochemically. Results: Erlotinib reduced tumor volume in three NSCLC models. It also reduced serum tumor marker levels and the extent of inhibition correlated with tumor growth inhibition. HER1/EGFR and HER2 expression differed between the five tumor models, suggesting that expression level does not predict response to treatment. Conclusion: Erlotinib showed differing antitumor activity in five NSCLC models, suggesting that its antitumor effect is independent of HER1/EGFR and HER2 overexpression.