| ObjectiveThe aim of this study was to investigate the influence of different dosing time points on the efficacy and adverse reactions of gefitinib and to explore its molecular mechanisms.Methods1. Female C57BL/6mice were implanted with Lewis lung carcinoma cells. The tumor bearing mice were divided randomly into thirteen groups including control group, six experimental groups and blank groups. The six experimental groups were given via gavage a single dose of gefitinib (100mg/kg) at6different time points (8:00,12:00,16:00,20:00, and24:00and4:00). The control group and blank groups were treated with the same volume of5%sodium carboxymethylcellulose.2. During the three weeks’ the administration of the drug, quality of life, and mice perianal swelling were recorded daily, the tumor volume was measured every three days. The blood samples were collected from the eye socket vein of the mice and then the mice were killed by cervical dislocation after three weeks’treatment with the drug. With their tumors pelt off in sterile conditions and weighed, the tumor inhibition rate was calculated.3. The blood samples were collected from the eye socket vein in mice, and50μl of the blood was used for blood routine test. Hematological parameters examined in this study included white blood cells(WBC), red blood cells(RBC), hemoglobin(HGB) and platelet(PLT) count.4. Some tumor and skin tissues were observed with histological analysis and scanning electron microscope (SEM) for the comparison of tumor necrosis and impact on the skin tissue.5. ELISA technique was employed to determined the level of IL-2, IL-6, and TNF-a in the blood according to the Biolegend introduction.6. RT-qPCR was performed to detect the expressions of EGFR, ABCG2, and MMP-9, P53genes for the exploration of molecular mechanisms.Results1. Gefitinib had an effect on the quality of mice life. The sprit state of the mice in A, B, F groups was better than C, D and E groups. The viscera index in A, and F groups was markedly higher than the other groups(P<0.05).2. Gefitinib could inhibit the growth of tumor in C57BL/6mice pronouncedly. In the whole experimental groups the tumor volume of A group increased more slowly(P<0.05), whose tumor inhibition rate was maximum and the C group’s was the minimum (44.12%vs14.15%,χ2=36.00, P=0.000). The histological and SEM analysis showed severer impairment to the tumor cells but less injury to the skin when gefitinib was administered at8:00and4:00.3. The results of blood routine test indicated that there was no significant difference among six experimental groups(P>0.05). The level of IL-2, IL-6and TNF-a in the experimental groups increased compared with the control group, which in A and F groups was closer to that in the control group. The level in C and D groups was higher compared with A and F groups (P<0.05).4. The expression of EGFR in various groups treated at different time points displayed significant differences. The EGFR expression in A group was the least, while that in C and D groups was higher than the above (P<0.05). The expression of EGFR in blank groups without gefitinib treatment showed circadian change, which reached the peak around12:00and reached valley value about20:00. The expression of MMP-9, ABCG2and P53in experimental also showed distinct differences(P<0.05), which in C, D and E groups was more than other experimental groups.Conclusions1. The results demonstrate that the efficacy and toxicities of gefitinib vary with its dosing time during a day. The efficacy of the drug can be increased, and toxicities of the drug can be decreased when it is administered at8:00and4:00.2. The underlying mechanism might be that rhythmic change in the mRNA expression of EGFR in tumor-bearing mice seems to affect the efficacy of gefitinib. Dosing-time should be taken into consideration when gefitinib is applied. |
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