Apatinib to enhance antitumor activity of gefitinib in non-small cell lung cancer.

Abstract

e20086 Background: Gefitinib, an oral EGFR-TKI, is recommended as the first-line therapy for non-small cell lung cancer (NSCLC) patients with EGFR mutations. Apatinib is an oral TKI against VEGFR-2 and is effective as third- or later-line treatment in advanced NSCLC. EGFR and VEGF/VEGFR pathways are interrelated. We conducted this study to explore the effect of gefitinib plus apatinib therapy in NSCLC and the possible mechanism. Methods: Cell viability assay was performed on 4 NSCLC cell lines (A549, H1975, H1650 and HCC827) to determine IC50 of gefitinib, apatinib and their combination for growth inhibition. The nude mice were injected i.h. with H1975 cells to establish EGFR mutated NSCLC xenograft tumor. Tumor volume was recorded every three days. Immunohistochemistry for Ki67 and PCNA expression was performed to detect tumor cell proliferation in mice. In addition, the expression levels of key proteins were detected by immunohistochemistry and western blot, respectively. Results: The H1975 cells were the most susceptible to the combination of gefitinib and apatinib, with lowest IC50 value of 0.44 ± 0.09, compared with other cells. In H1975 xenograft model, gefitinib plus apatinib showed markedly higher inhibiting effect on tumor volume than both gefitinib and apatinib mono-therapy. Moreover, the expressions of both Ki67 and PCNA significantly decreased in mice after combined therapy than either gefitinib or apatinib alone, indicating that the combined therapy was superior to mono-therapy of gefitinib or apatinib in suppressing cell proliferation in mice. Additionally, there was an obviously higher expression of EGFR, pho-EGFR, VEGFR, pho-VEGFR, VEGFA, p-mTOR, t-mTOR, p-AKT, t-AKT, p-Erk, and t-Erk in mice treated with gefitinib plus apatinib than mono-therapy. Furthermore, the much stronger inhibitory effect on angiogenesis of gefitinib plus apatinib therapy was revealed, as more expression of CD31 than both gefitinib and apatinib mono-therapy. Conclusions: Apatinib significantly potentiated the antitumor effect of gefitinib in NSCLC both in vivo and vitro. These findings support a great therapeutic potential role for the combination of apatinib and EGFR-TKI in the treatment of NSCLC in clinic.