Anti-tumor Activity Of High-dose EGFR Tyrosine Kinase Inhibitor Combined With Docetaxel Against Lung Cancer With EGFR Wild Type In Vivo

Background:Lung cancer is the leading cause of cancer-related deaths in the world and Morbidity and mortality has been increasing year by year.At present, lung cancer can be generally divided into two categories according to the difference of biological behavior: NSCLC which accounts for approximately 80% of all lung cancer cases and SCLC which accounts for approximately 15-20%.With the increase of awareness of tumor molecular biology, driven genes of lung cancer have been found, such as EGFR,ALK. Targeted therapy has developed rapidly and become a hot spot in clinical application and research.Several randomized, open-label, phase III clinical trials have compared TKIs with the routine chemotherapy, and the data suggest that the response rate(RR) and PFS of patients with EGFR-mutated NSCLC who receive EGFR-TKIs as a first-line treatment are significantly greater than those of patients who receive chemotherapy,although the OS did not differ significantly between these two treatments.However,the mutation of EGFR only occupies in a small proportion.EGFR mutations accounted for 9-21% in the Caucasian population while approximately 40% in the Asian population.This means that EGFR with no mutation(wild type) lung cancer still holds the majority.NCCN guidelines recommend that patients with EGFR mutation positive should be treated with TKIs, and EGFR wild type could be treated with chemotherapy.But studies have shown that chemotherapy couldn’t improve the long-term outcome of the vast majority of patients with lung cancer.In other words,the curative effect of chemotherapy has reached the stage of platform.In this study, we explore a preclinical characterization of the antitumor activity of icotinib using in vivo models. This report reports the findings with icotinib antitumor activities in lung cancer line A549 with wild type EGFR,further showing the anti-proliferation of different administration sequences and dose of icotinib and docetaxel. The data we generated from the study investigated in human NSCLC xenograft models would provide a theoretical basis for clinical related use of drugs.Methods:Lung cancer xenografts models were established with EGFR wild-type A549 tumor cell line, and 80 mice divided them into 5 groups according to the design of experiment, which included the control group,the single drug group(DTX, Ico H,Ico N), different doses of icotinib then docetaxel sequential groups(Ico H-DTX,Ico N-DTX), two drug combination groups(Ico H+DTX, Ico N+DTX), docetaxel then different doses of icotinib sequential groups(DTX-Ico H, DTX-Ico N). The tumor growth curves were drawn by measuring the changes of tumor volume in vivo twice a week, and the tumor inhibition rates were calculated after treatment. Determination of apoptosis related protein content by western blot method. MVD was observed by immunohistochemical staining.Results: 1. The changes of tumor volume and the tumor inhibition rates(1) the tumor inhibition rate of the high-dose icotinib alone group were better than the normal-dose icotinib alone group(P<0.05), which inferior to docetaxel alone group(P<0.05);(2)two drug combinations regardless of the order,the tumor inhibition rate of the high-dose icotinib group were better than the normal-dose icotinib group(P<0.05),and there were no significant difference between the normal-dose icotinib combined with docetaxel and docetaxel alone group(P>0.05);(3) the tumor inhibition rate of the high-dose icotinib then docetaxel sequential group was the best( P<0.05). The changes of tumor volume come to the same thing2.Determination of apoptosis related protein(1)the expression of EGFR 、AKT 、 MAPK without phosphorylated was no significant difference among the different groups;(2) icotinib can inhibit the phosphorylation of EGFR 、AKT 、MAPK, and high-dose icotinib better while docetaxel had no influence on it;(3)Compared to docetaxel alone group, docetaxel and Eck imatinib combined application of phosphorylation of Akt was no significant changes in two drug combinations groups, but phosphorylation of EGFR and MAPK which induced by docetaxel was inhibited the combined application of icotinib with high-dose significantly;(4) theinhibition of phosphorylation of EGFR、AKT、MAPK in different doses of icotinib then docetaxel sequential group obviously superior than two drug combination groups and docetaxel then different doses of icotinib sequential groups.Conclusions: High-dose of icotinib then docetaxel sequential(Ico H-DTX) can effect the tumor growth in mice with EGFR-wildtype A549 xenografts.