Study Of The Reversal Effect Of Recombinant Human Endostatin On Chemotherapy Resistance In Human Lung Adenocarcinoma A549/DDP Cells

Objective: This study was to evaluate reverse effect of recombinant human Endostatin on drug-resistance of A549/DDP cells to cisplatin (DDP), and to explore its mechanisms.Methods: Lung adenocarcinoma cell line A549 and its DDP-resistant cell line A549/DDP were treated with DDP and/or recombinant human Endostatin. Difference in drug resistance was analyzed between different regimens (DDP, Endostatin and combination) and between different cell lines (A549 versus A549/DDP), after a 72h-treatment in vitro. MTT analyzed the growth inhibition by rh-Endostatin and DDP in A549 or A549/DDP was used to determine non-cytotoxic concentration of rh-Endostatin, and 50 % inhibited concentration for DDP, and to determine DDP-resistance index in A549/DDP. Cellular apoptotic rate and the expression of resistant proteins were analyzed with Caspase-3 method and western blot respectively in A549/DDP treated with Endostatin astence protein (LRP) and Glutathione -S-Transferase (GST).Results:1. MTT: rh-Endostatin at 400ug/ml showed no cytotoxicity in either A549 or A549/DDP after 72h-treatment. The observed 50%inhibited concentration (IC50) for DDP was (0.79±0.06) ug/ml in A549 and (13.3±0.9) in A549/DDP respectively. The DDP-resistance index in A549/DDP was 16.8. IC50 was lowered to 2.57±0.04ug/ml in A549/DDP treated by rh-Endostatin under the non-cytotoxic concentrations in combination with DDP, with a reversal fold (RF) of 5.14 and a relative reversal rate of 85.6%, demonstrating Endostain enhanced the killing effect of DDP in A549/DDP through a potential to reverse the resistance.2. The apoptosis rate result of Caspase-3: OD figure were 0.034±0.21, 1.289±0.39 and 2.693±0.78 respectively for cells treated with Endostain, DDP, and combination. A rate of 0.015±0.35 was reported in the A549/DDP control (P<0.05 in DDP group comparison).3. Western Blot: expression of LRP or GST was higher in A549/DDP cells. An obvious drop in expression level of either LRP or GST was noticed in A549/DDP treated with Endostatin-DDP combination with statistical significance (P=0.05 ,in DDP group comparison).Conclusion: Rh-Endostatin may partially? reverse DDP-resistance in A549/DDP cells in vitro, with a probable mechanism relating to lowered expression of LRP and GST, and to increased apoptotic rate.