| Lung cancers, among which non-small cell cancer (NSCLC) accounts for 80%, are the highest cause of both the morbidity and mortality worldwide. Meanwhile, the morbidity rate for pulmonary adenocarcinoma remains rapidly increasing. So far chemotherapy is still the major approaches of lung cancers therapy, because once detected many patients have been in advanced stage and lost chances of promptly surgical treatment. However, drug resistance, especially multi-drug resistance of tumor cells may often leads to the failure of the chemotherapy. More recently, it has become apparent that vascular endothelial growth factor (VEGF) over-expression in NSCLC is related not only to tumor growth, metastasis and poor prognosis, but also to the resistance to traditional therapeutic drugs. Therefore, anti-angiogenesis therapy, by targeting VEGF, has been considered as an important strategy to inhibit tumor growth and overcome drug resistance. Recent works have demonstrated that nordihydroguaiaretic acid (NDGA), a natural extracted product from plants, inhibits growth of many tumors in vitro and in vivo. These effects involved in reduction of many vascular growth factors expression, and inhibition of endothelial cells immigration, et al. Based on the chemical structure of NDGA, a new compound, named Nordy is synthetized. Primary studies shown that being similar to native NDGA, Nordy inhibits growth of many tumors, including malignant glioma, gastric cancer and leukaemia cells. However, the effects and its possible mechanisms of Nordy on expression of vascular growth factors and overcome drug resistance in lung cancer cells remain obscure. In the present study, the effects of Nordy on cell proliferation of human pulmonary adenocarcinoma cell line A549, its drug-resistance cell line A549-DDP in vitro, and on tumor growth of their xenografts in nude mice, as well as on expression of VEGF and P-glycoprotein were investigated by using the cell proliferation assay, light and electron microscopy, flow cytometry, in situ hybridization and immunohistochemistry combined with image analysis. Furthermore, the possible mechanisms of anti-angiogenesis and overcome drug resistance in lung cancer cells by Nordy were explored. Our aim was to provide more valuable experimental evidences for the possibility of clinical therapeutic trails of Nordy. The main results and conclusions are as follows: 1. To investigate the changes of cell morphology and proliferation rate in response to Nordy, A549 and A549DDP cells were treated for up to 72 hours with 50μmol/L, 100μmol/L,200μmol/L of Nordy, respectively. A dose- and time-dependent proliferation inhibition was demonstrated in both above cell lines after Nordy treatment. The average IC50 value of Nordy for A549 and A549DDP cells were 48.17μmol/L, 52.99μmol/L, respectively. The profound morphological changes in these cells, including reduction of cellular atypia, formation of abundant cytoplasmic processes, mitochondrial swelling and crista-breaken, as well as necrosis of local cytoplasma were occurred. Cell cycle analysis results showed that cell ratio in G0/G1 phases was augmented, while that in S and G2/M phases was decreased, which hinted that the cells were mainly blocked at G1 to S transition point after treatment with 100μmol/L Nordy. By using in situ hybridization and immunocytochemistry staining, it was found that the expression of VEGFmRNA in A549 and A549DDP cells were significantly decreased after treatment with 100μmol/L of Nordy for 72 hours. The more serious decline of P-glycoprotein expression level in A549DDP cells was also revealed. All these results suggested that Nordy inhibits the proliferation rate of lung cancer cell line A549 and its drug-resistance cell line A549-DDP in vitro, which might be closely related to its effects of blocking cell cycle proceeding, declining the expression level of VEGF mRNA and P-glycoprotein in these cells. 2.The animal models of human pulmonary adenocarcinoma cell line A549, and its drug-resistance cell line A549-DDP xenograft in nude mice were us... |
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