Effects Of Cisplatin And Endostar In Different Administration Sequences Combination On C57/BL/6Mice Xenografts

Purpose: Lung cancer is one of the most common malignant tumors inthe world. We have found that anti-angiogenesis therapy combined withcytotoxic therapy can produce better clinical curative effect, but which isthe optimal administration sequences when the two types of drugs usedtogether is still unclear. Our research evaluated the effect of theangiogenesis inhibitor recombinant human endostatin (Endostar)combined with cisplatin(DDP) under different administration sequenceon C57/BL/6mice xenografts. We calculated the tumor inhibition andexamed the changes of cell cycle distribution and the micro-vesseldensity and the concentration of DDP after treatment to elucidate theoptimal administration sequences the endostar combined with DDP, andthe possible mechanism. Method: the experiment contains two parts. Atthe first phase of our experiment, we divided35C57/BL/6mice into5groupsrandomly after obtaining tumor model (n=7in each group): Group NS:treated with NS control. Group Endostar: the mice were only treated withendostar at a dose of10mg/kg/d for14consecutive days. GroupCisplatin: the mice were only treated with cisplatin on day1and day8ata dose of4mg/kg/d. Group Endostar+Cisplatin: mice were treated with endostar and cisplatin simultaneously using the methods described above.Group Endostar First: endostar was given to each mouse from the firstday to the fourteenth day and cisplatin was given on day5and day12. Alldrugs were administrated with intraperitoneal injection. Tumors growthwas evaluated on alternate days by measurement of tumor diameters, andanimals were killed on day15by cervical dislocation.Then stripped andweighted the tumor tissue quickly, and calculated the tumor inhibition.Endostar was also assessed for its abilities to decrease microvesseldensity by using an anti-CD31method. The changes of cell cycledistribution after treatment were examined by flow cytometry. At thesecond phase of our experiment, animals were randomized into thefollowing3groups (n=20in each group): Group Cisplatin, GroupEndostar+Cisplatin and Group Endostar First. Each group was treatedwith the same medication as the first stage. The blood samples were takenfrom mice eyes in each group at the day1(20minutes after the firstinjection of cisplatin), day3, day5, day8(20minutes after the secondinjection of cisplatin) after ip injection of cisplatin, respectively. And thenkilled the mice. The concentration of cisplatin in blood and tumor tissueat different time pionts after administration was detected byhigh-performance liquid chromatography (HPLC). And the MVDdestcted by immunohistochemial. Results: the tumor volume has nostatistical difference in each group bebore administrated(P>0.05). Treatment with cisplatin showed significant inhibitory effects on tumorgrowth compared with NS or endostar alone. Compared with GroupEndostar First and Group Cisplatin, Group Cispatin+Endostar had themost significant delay in tumor growth as determined by tumor volumeand weight on day14(P<0.001). As to the tumor inhibition rate, GroupCisplatin, Group Cisplatin+Endostar and Group Endostar First hadsignificantly inhibited the tumor growth compared with the Group NS,especially Group Cisplatin+Endostar. And the q values of GroupCisplatin+Endostar is1.564, indicating that the two drugs have asynergetic effect when simultaneously used. But the q value of GroupEndostar First is1.095which means the two drugs only have additiveeffects when the two drugs was administrated successively. Thus,simultaneous therapy can increase the effectiveness better, compared withendostar followed by cisplatin. The cell cycle distribution was changedsignificantly after14days. Group Endostar, Group Cisplatin+Endostar,Group Endostar First have significantly increased G0/G1cell cycle arrest,increased G2/S arrest, and decreased the proliferation index (PI)compared NS treated group, especially when the two drugs usedsimultaneously (P<0.05). And there is also statistically significantdifference between the Group Cisplatin+Endostar and Group EndostarFirst (P<0.05). Tumors of the control groups, treated with NS, showedlarger mirovessel count than those of the other groups submitted to cisplatin or/and endostar, especially the simultaneous combination group(P=0.021). Furthermore, compared with the Endostar First Group, thesimultaneous combination group also showed significant difference(P=0.21). But there are no statistical significance between Endotar Groupand Endostar First Group. The concentration of cisplatin in tumor tissuehad been higher than in blood when simultaneous group on the third day(P<0.05), but the same phenomenon did not occurrence in the other twogroups. The concentration of cisplatin was the highest on the eighthday(3.794±0.210μg/ml), but no significant difference between GroupEndostar First and Group Cisplatin. But the MVD of simultaneous treatedgroup was obviously lower than cisplatin treated alone on the fifth day(P>0.05). On the eighth day, compared with cisplatin treated group, MVDof the combination groups were lower (P>0.01), especially thesimultaneous treated group. And Group Cisplatin+Endostar comparedwith the Group Endostar First, the P valued0.047. Conclusion: It hassynergistic antitumor effect when endostar and DDP used simultaneously,but additive antitumor effect then the two used successively. Endostarcombined with DDP could obviously inhibite the growth of the Lewislung cancer in mice, and it could improve the distribution of the cell cycleto make more tumor cells be in G0/G1phase, induce cell apoptosis andreduce the number of S phase cells, reduce cell proliferation. It also couldmake the chemotherapy drugs to penetrate into the tumor tissues better and improve the concentration of DDP in tumor tissue. And it improvedthe hypoxia to normalize the blood vessels and reduce the MVD of tumortissue. The concentration of DDP and MVD in tumor tissue had thesimilar changing trend when endostar combined with DDP, but thechanging of the MVD was slower. In addition, the therapeutic effect maybe associated with the cell cycle specificity or non-specificity ofchemotherapy drugs when endostar combined with chemotherapy drugs.