Chronopharmacodynamics And Mechanisms Of Antitumor Effect Induced By Gefitinib In Tumor-bearing Nude Mice

Objection:To investigate the antitumor effect of gefitinib at different dosing times and the underlying molecular mechanism via the PI3K/AKT/m TOR and MAPK/ERK pathway.Methods:we established a mice model of non-small cell lung cancer xenografts. The mice were randomly divided into six experimental groups and a model group and placed in alternating light and dark environments. After adaptive feeding for one week, the mice in the experimental groups were divided into six subgroups, which were given gefitinib orally at six different time points for 21 days. The mice in the model group were given the same amount of solvent. The changes of tumor volume were measured every three days.After the mice were sacrificed, the tumor tissue was removed and weighed to calculate the inhibition rate. The m RNA expression of EGFR, AKT and m TOR were assayed by quantitative real-time PCR. Protein expression levels of P-EGFR, P-AKT and P-m TOR were determined by Western blot analysis. Apoptosis of tumor tissue sections was detected by TUNEL.Results:1.Compared with the model group, the tumors in the experimental groups grew more slowly(P <0. 05, Figure 1), and the tumors grew more slowly in groups 8:00, 4:00 and12:00 than in groups 16:00, 20:00 and 24:00.2.The tumor weight in all the experimental groups, except the 20:00 group, was significantly lower than that in the model group(P<0. 05, Table2). The tumor weight in the groups 4:00,8:00, and 12:00 was significantly different from that in the 20:00 group(P<0. 05). In all the experimental groups, the inhibition rate was the highest in the 8:00group, and the lowest in the 20:00 group.3.The relative expression of EGFR genes in the groups 4:00 and 8:00 was significantly different from that in the model group(P<0. 05). The relative expression of AKT genes in the groups 4:00, 8:00 and 12:00 was significantly different from that in the model group(P<0. 05). The relative expression of m TOR genes in the groups 4:00, 8:00 and 12:00 was significantly different from that in the model group(P<0. 05). The relative expression of ERK genes in the groups 4:00, 8:00 and 12:00 was significantly different from that in the model group(P<0. 05).4.The relative expression of p-EGFR protein in the groups 4:00, 8:00, 12:00 and 24:00was significantly reduced when compared with the model group(P <0. 05). The relative expression of p-AKT protein was significantly reduced in the groups 4:00 and 8:00 when compared with the model group(P <0. 05). The relative expression of p-m TOR protein was significantly reduced in the groups 4:00 and 8:00 when compared with the model group(P <0. 05).The relative expression of p-ERK protein was significantly reduced in the groups 4:00, 8:00 and 24:00 when compared with the model group(P <0. 05).5.The rate of apoptotic tumor cells in the groups 4:00, 8:00and 12:00 was statistically lower than that in the model group.Conclusion:Gefitinib can inhibit the tumor of bearing nude, and which has time rhythm, best time of inhibitory effect is 8:00, and the worst time of inhibitory effect is 20:00. Its mechanism is partly related to EGFR/AKT/m TOR and EGFR/ERK pathways.