The Antiangiogenic Experiment Of Docetaxel Metronomic Chemotherapy Combined With Dexamethasone On Lung Cancer-bearing Murine Model

Background and ObjectivesOne of the great achievment in cancer treatment during last half of the 20^th century was the development and clinical utilisation of chemotherapeutic drugs. These compounds have demonstrated the antitumour efficacy by means of damaging cellular DNA or inhibiting microtubules function, as a result, the proliferation was prevented and, brought the cancer cells to death. To kill the cancer cells as more as possible, the dosage of drugs are often used up to the maximum tolerated dose (MTD). However, the severe toxicity was caused by MTD as per expectation. Thus, it is necessary to establish rest interval for patients to get recovered from the side effects. But at the same time, tumor cells and the stromal cells around appear to thrive again. Therefore, most MTD chemotherapy not only impaires the quality of life of cancer patients, but also the efficacy is not satisfactory.In order to lessen the problems caused by MTD chemotherapy, lots of researchers devoted to searching for new modalities of drug administration aiming for a more efficient and non-toxic antitumoral and/or antimetastatic therapy. Angiogenesis is necessary to sustain the growth of the primary tumour and its infiltration, metastases. The therapy targeted to the tumour angiogenesis was first proposed by Folkman in 1971. From then on, researchers turned to the antiangiogenic effects of cytoxic drugs. In fact, all kinds of chemotherapeutic drugs proved to damage DNA or disrupt microtubules of dividing cells. As we all know, the endothelial cell division develops along with the new blood vessel formation, and tumor angiogenesis is included. Moreover, compared to the normal vessels which are almost stable, tumor endothelial cells proliferate at a faster rate and may be more sensitive to some chemotherapeutic drugs.Experiments had shown that some cytoxic drugs inhibited angiogenesis effectively, especially when administered more frequently and at lower dosage. Compared to MTD chemotherapy with long rest interval (e.g. 2-3 weeks) between consecutive cycles, it was more effective on the tumor vessel endothelial cells when administered more frequently and at a lower dosage. The reason is, recovery of tumor endothelial cells from the chemotherapy damage could be compromised, therefore the antiangiogenic effect was improved. This type of regimen was called "metronomic therapy" or "antiangiogenic chemotherapy". The metronomic therapy is targeted on the endothelial cells which are actived and genetically stable, thereby the resistance to the minimum dosage is reduced. In addition, the toxicity was also decreased. Moreover, the efficacy of metronomic chemotherapy can also be improved significantly by concurrent administration of other angiogenic drugs.Investigation shows lots of tumor generation and progress have close relation with chronic inflammation. Except anti-tumor, inflammation reaction promotes proliferation of tumor and angiogenesis, metastases .Inflammation-dependent angiogenesis seems to be a central force in tumor growth and expansion, a concept supported by the observation that the use of "classic" anti-inflammatory drugs, leads to angiogenesis inhibition. The mechanisms of inflammatory angiogenesis provide new approaches to target, prevent tumor angiogenesis by treatment of agents with anti-inflammatory properties. Now the reports that metronomic chemotherapy combinded with anti-inflammatory are very few abroad. It has not been reported in China.This experiment was presented on Lewis lung carcinoma bearing C57BL/6 mice, in order to evaluate the effect of docetaxel by means of metronomic chemotherapy and antiinflammation drug dexamethasone on angiogenesis and tumor growth of tumor bearing murine model, and accordingly compare their efficacy and toxicity.Materials and MethodsC57BL/6 mice bearing Lewis lung carcinoma were randomised into four groups:(1) docetxel metronomic group. Administer docetxel 5mg/kg intraperitoneally every other day;(2) dexamethasone group. Administer dexamethasone 5mg/kg intraperitoneally once a day;(3) coroperation group. Administer docetaxel 5mg/kg intraperitoneally every other day, dexamethasone 5mg/kg once a day (4) control group. Administer Normal Saline 0.2ml intraperitoneally once a day. There were ten mice in each group. Drugs were given from the 6^th day of post inoculation and continued for 8 days. The general performance of mice was observed every day. At the 15^th day of post inoculation, all mice were killed. Then we monitored tumor growth and weight loss of mice aiming to evaluate the efficacy and toxicity of different therapy. In the end, tumors were resected, weighed and immunohistochemistry was performed. Tumor microvessel density (MVD) and expression of hypoxia inducible factor 1(HIF-1) and nuclear factor-kappa B (NF-κB)were detected by IHC. The histological characteristics of the tumor were detected by microscopy. Statistical analysis of the experiment data was performed with SPSS10.0 statistical software, MVD comparing of each group using ANOVA and LSD analysis. Express comparing of HIF-1 and NF-κB using nonparameter test, Mann-Whitney both independent sampler comparing test. The level of significance was set at a= 0.05.Results1. The tumor growth curve in docetxel metronomic group dexamethasone group and coroperation group are near flat and that in control group is very steep.2. Mice in docetxel metronomic group dexamethasone group and coroperation group had no weight loss and increased slowly steadily. Mice weight in control group increased steadily and speed was fast. In the end, the weight of tumor in docetxel metronomic group, dexamethasone group, coroperation group and control group are (2.85±0.30)g (2.80±0.31)g (2.46±0.21)g (4.25±0.42)g, respectively.3. Observing the tumor samples grossly, we found that the tumor capsule in control group is breached and tumor is ruddy and crisp, while in docetxel metronomic group dexamethasone group and coroperation group, the capsule is intact and tumor is pale and tenacious. On microscopic examination of HE stained slides, we found that tumor tissue have more microvessels in control group than that in docetxel metronomic group dexamethasone group and coroperation group, while multiple areas of necrosis were found.4. The microvessel density (MVD) in docetxel metronomic group, dexamethasone group, coroperation group and control group are (15.89±2.28) (15.90±1.92) (12.44±1.72) and (27.10±2.06) respectively. MVD in docetxel metronomic group, dexamethasone group and coroperation group is lower than that in control group, and the difference is statistically significant (P<0.05).5. Expression of HIF-1 in docetxel metronomic group, dexamethasone group and coroperation group is lower than that in control group, and the difference is statistically significant (P<0.05).6. Expression of NF-κB in docetxel metronomic group, dexamethasone group and coroperation group is lower than that in control group, and the difference is statistically significant (P<0.05).Conclusions1. Docetaxel metronomic chemotherapy and dexamethasone can inhibit the growth and angiogenesis of Lewis lung carcinoma effectively.2. Docetaxel metronomic chemotherapy combinds with dexamethasone can inhibit synergisticly the growth and angiogenesis of Lewis lung carcinoma effectively,which effect is better than mono-agent group.3. Docetaxel metronomic chemotherapy and dexamethasone can inhibit the growth and angiogenesis of Lewis lung carcinoma effectively by inhibit expresstion of HIF-1a and NF-κB.