Effects Of Tumstatin185-191 On Lung Adenocarcinoma Cell Lines: Blocking Proliferation, Promoting Apoptosis, Inhibiting Akt And ERK Activation, And Increasing Sensitivity To Cisplatin

Purpose Tumstatin and the peptides derived from tumstatin have previously been shown to be effective in vivo and in vitro against a wide range of human tumors.To data,however,few studies have investigated the combination antitumor activity of tumstatin with conventional anticancer drugs in cancinoma,and insufficient data are available on the antitumor effects by the tumstatin on non-small lung cancer(NSCLC) cells.In this report,we investigated the effects of tumstatin 185-191(Tum185-191) as a single agent or combination with cisplatin on NSCLC cell lines A549 and A549/DDP.In addition,we evaluated the changes in the Akt and ERK signaling in cultured NSCLC cells treated by tumstatin 185-191 and cisplatin.Methods A549 or A549/DDP cells were treated with Tum185-191 and cisplatin.Cell Viability was assessed using the modified 3-(4,5-dimethylthiazoh2-yl)- 2,5-diphenyltetrazolium bromide(MTT) assay. 50%inhibiting concentration(IC₅₀)values and reversing drug-resistance index(RI) of the chemotherapeutic drug were analyzed by MTT assays. Cell apoptosis was measured by morphological observation and flow cytometry.The activation of Akt and Erk were evaluated by immunocytochemistry and Western blotting.Results Here we showed that Tum185-191 could inhibit the proliferation of A549 and A549/DDP cells.IC₅₀ values of Tum185-191 were 73.67μM in A549 cells and 80.25μM in A549/DDP cells.After treated with 20μM Tum185-191,IC₅₀ values of cisplatin in A549 cells reduced from 5.24μM to 3.48μM,while 40μM Tum185-191 reduced from 5.24μM to 1.39μM.In A549/DDP cells,20μM Tum185-191 reduced IC₅₀ values of cisplatin from 77.16μM to 57.97μM,and 40μM Tum185-191 reduced to 26.40μM.The RI was 1.33 in 20μM Tum185-191 treated cells and 2.92 in 20μM Tum185-191 treated cells. Cotreatment with tumstatin 185-191 and cisplatin exerted significantly greater effects in promoting apoptosis than either agent used alone.A lower levels of phospho-Akt(p-Akt) and phospho-ERK(p-ERK) were found in the A549 and A549/DDP cells treated with higher dosage of tumstatin 185-191,while tumstatin 185-191 treatment whether alone,or in combination,had the similar effects on the protein levels of p-Akt and p-ERK in A549 and A549/DDP cells.Conclusions Our data suggest that Tum185-191 might enhance the sensitivity of A549 cells to cisplatin and has reversal effects on cisplatin resistant cell line A549/DDP.The effects of promoting apoptosis and downregulation of proliferation induced by Tum185-191 may be mediated through inactivation of the Akt and ERK pathways. Tum185-191 has promising antitumor activity either as single agent or in combination with cisplatin in A549 or A549/DDP cells.These findings indicate that combining conventional anticancer drugs such as cisplatin with agents that inhibit specific survival signals may provide a molecular basis for novel chemotherapeutic strategies in the treatment of NSCLC.