| Background and ObjectiveMalignant melanoma generates from melanocytes .It's rare in China, accounting for 1-2% of all cancers .However, it has high mortality rate, high-risk of distant metastasis and poor prognosis. The survival time of most patients is less than 10 years. Malignant melanoma is not sensitive to adjuvant chemotherapy and radiotherapy.It was demonstrated that growth of solid tumors beyond 1-2 millimeters relies on new capillary blood vessel, which plays an important role in tumor size, metastasis, relapse and prognosis. It was hypothesized firstly by Folkman in 1971 that the continuous growth and metastasis of tumor depend on angiogenesis. With Avastin being used in clinic, anti-angiogenic therapy seems to be a promising modality for therapy of human malignant disease.Thalidomide, initially introduced as a sedative, was withdrawn from the market in the early 1960s because of its teratogenicity. Latter, some researchers found that thalidomide has the function of anti-angiogenesis, so it was used as anti-tumor drug for many cancers, such as multiple myeloma. Now, there are no reference about thalidomide on malignant melanoma in China. The aim of this study is to observe the effect of thalidomide on melanoma in mouse B16 melanoma model and explore the mechanism.Methods1. C57 mice model bearing B16 melanoma were established. On the second day ,the mice were randomly divided into 5 groups and each group consisted of 10 mice: high,middle,low dosage groups of thalidomide(400mg/kg/d,200mg/kg/d,50mg/kg/d of thalidomide were respectively dissolved in 0.2ml NS and given intragastricly every day for 14 days ); Positive control group(100mg/kg/d of CTX was injected intraperitoneally on day 1) ; Negative control group(the same volume of N-S was given intragastricly every day for 14 days). The diameters of the tumors were measured every two days. On the 15th day, the mice were sacrificed and the tumors were weighed. The rate of tumor inhibition was calculated. The survival time of the tumor-bearing mice were record in the same methods.2. Tumor tissue samples were taken and examined by HE staining to observe pathomorphologic difference between experiment groups and negative control group.3. The microvessel density (MVD) and the expression of vascular endothelial growth factor (VEGF) of the tumors were tested by immunohistochemical staining.4. The expression of VEGF mRNA in the tumor of every dosage group of thalidomide and negative control group was tested by reverse transcription-polymerase chain reaction (RT-PCR).5. SPSS10.0 software was used to carry out statistical analysis. F-test was employed. P volume was 0.05.Results1. The mean tumor weight of low,middle,high dosage groups of thalidomide (2.1307±0. 5018g,1. 9813±0. 6578g,2. 0986±0. 5549g) was less than that of negative control group (2. 4995±0. 8081g) . The inhibition rate (IR) of tumor growth was 14.75%,20.73% and 16.04%, respectively . However , the difference had no statistical significance (P>0.05) .The difference of mean tumor weight between different dosage groups of thalidomide had no statistical significance (P>0.05) . The mean tumor weight of the positive control group (0.4208± 0. 0719g) was obviously less than that of negative control group, IR was 83.17%, the difference had statistical significance (P<0.05) .2. The mean survival time of the tumor-bearing mice in low,middle,high dosage groups of thalidomide(27.3±5. 2d,29. 8±3. 3d, 25. 6±3. 4d,34.1±4. 2d) was longer than that of negative control group (21.5±3. 6d) , the difference had statistical significance (P<0.05) . However, the difference of the survival time in the tumor-bearing mice between different dosage groups of thalidomide had no statistical significance (P>0.05) .3. Different widespread necrosis domain of tumor cells was observed by HE staining examination in every dosage group of thalidomide. :4. In the three groups of mice treated with thalidomide, the expression of VEGF significantly decreased compared with that of negative control group(P<0.05) .The expression of VEGF in high,middle dosage groups significantly decreased compared with that of low dosage group (P<0.05) .The difference of expression of VEGF between high dosage group and middle dosage group didn't reach statistical difference (P>0.05).5. In the three groups of mice treated with thalidomide the microvessel densities count significantly decreased compared with that of negative control group(P<0.05) ,the difference of MVD between different dosage groups of thalidomide didn't reach statistical difference (P>0.05).6. In the three groups of mice treated with thalidomide, the relative quantities of VEGF mRNA were lower than those of negative control group. The difference reached statistical significance(P<0.05). The relative quantities of VEGF mRNA in high,middle dosage groups significantly decreased compared with those of low dosage group(P<0.05) .The difference of relative quantities of VEGF mRNA between high dosage group and middle dosage group didn't reached statistical difference (P>0.05).Conclusion1. Thalidomide alone has no inhibitive effect on melanoma growth in mouse B16 melanoma model. 2. Thalidomide can prolong the mean survival time of the tumor-bearing mice.3. Thalidomide can inhibit the expression of VEGF in mouse B16 melanoma model.4. Thalidomide can reduce the microvessel density in mouse B16 melanoma model. |
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