| Aims and Meaning: Lung cancer is the most common malignant tumor in the word. It has been one of the leading causes of cancer-related death in mankind. Following the use of cisplatin in the chemotherapy, the problem of multidrug-resistance (MDR) has become focal point of research. The chemotherapy of cancer is limited by the development of drug resistance of cancer cells and adverse effects of anti-tumor drugs. The search for novel anti-tumor agents that circumvent these limitations has turned to natural plants. Curcuma longa L belongs to the Zingiberaceae family. Curcumin which was extracted from the rhizomes of C. longa L is the major component of this plant. Modern medical research shows that curcumin has anti-tumor effects. Although many studies shows that curcumin can suppress the growth of many kinds of tumor cell and induce apoptosis of different types of tumor cells, there are very few reports about the effect of curcumin on lung cancer multidrug-resistant cell line A549/DDP. So we chose the A549/DDP cell as the research subject to investigate the inhibitory effect of curcumin on A549/DDP and its effect on apoptosis of this cell line. Methods:①Cell counting was used to plot the cell growth curves of A549 cells and A549/DDP cells. The resistance index of A549/DDP cells to cisplatin was measured by tetrazolium (MTT) assay.②MTT assay also was used to measure the inhibitory ratio of A549 cells and A549/DDP cells in different concentrations of curcumin at different times. We calculated the IC50 values of curcumin of both cell lines by using the data obtained from the MTT assay and compared the IC50 values of A549 cells with that of A549/DDP cells. After the A549/DDP cells being treated with curcumin in the dose of about the IC50 for 24h, cell cycle analysis was detected by flow cytometry.③After 24h of treatment with curcumin in different concentrations, the morphologic changes of A549/DDP cells were observed under fluorescence microscope and the apoptotic states of A549/DDP cell were measured by terminal deoxynucleotidyltransferase-mediated deoxyuridine 5-triphosphate nick-end labeling (TUNEL) methods and flow cytometry.④Different does of curcumin were treated on A549/DDP cells, then, Western-blot was used to detect the level of the expression of cysteinyl aspartate-specific protease-8 (caspase-8) p10.Results:①The cell growth curve of A549 cells was similar to that of A549/DDP cells. The doubling generation time of A549 cells and A549/DDP cells were (33.24±0.24)h and (32.88±0.11)h, respectively(P>0.05).After 72 h of treatment with cisplatine, IC50 values of cisplatine to A549 cells and A549/DDP cells were 13.57μmol/L and 146.79μmol/L, respectively, which demonstrated A549/DDP with the resistance index of 10.82.②The inhibition of curcumin on A549 cells and A549/DDP cells was shown in the dose-dependent and time-dependent manner(P < 0.05) following 48h treatment with curcumin. IC50 value of curcumin to A549 cells was approximated that of A549/DDP cells.③After treatment with 20μmol/L of curcumin, there was a pronounced decrease of the cell rate in S phase, along with a significant arrest in G2/M phase.④Under fluorescence microscope, A549/DDP cells treated with curcumin showed shrunk or distorted nucleus with fluorescence conglomerated like grains in them.⑤TUNEL positive A549/DDP cells were detected in curcumin group. With the increase of doses of curcumin, the apoptosis indexes of A549/DDP cells increased and the number of An+PI– cells increased as well, i.e the apoptosis rate increased.⑥And the level of caspase8 p10 induced by curcumin increased as the concentration of curcumin increased in A549/DDP cells.Conclusions:①A549/DDP cell has similar growth property with A549 cell. Compared with its parental cell line A549, the A549/DDP was more resistant to traditional chemotherapeutics cisplatin. So A549/DDP cell can be confirmed as a MDR cell line.②Curcumin can inhibit A549 cells and A549/DDP cells from proliferation in dose-dependent and time-dependent manner. A549/DDP is sensitive to curcumin.③Curcumin can cause cell cycle to arrest in G2/M phase.④Curcumin can induce apoptosis of A549/DDP cells by activation of caspase-8.
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