title: Reversal of Chemoresistance in Human Lung Cancer Cell Line A549/Taxol by Synthetic Second Mitochondria-Derived Activator of Caspase Peptide.
abstract: BACKGROUND
  Chemoresistance is a leading cause of treatment failure in advanced lung cancer, including that with the extensively prescribed taxol. Recently, a series of structurally unique second mitochondria-derived activators of caspase (Smac) that act as antagonists of inhibitor of apoptosis proteins (IAPs) have been discovered, exhibiting the ability of inducing enhanced apoptosis of various cancer cell types when combined with chemotherapy. In the present study, we synthesized the second mitochondria-derived activator of caspase peptide (Smac-N7 for short) and explored its capacity in combination with taxol in vitro.
  
  
  METHODS
  The sensitivity assay and reversal ability of Smac-N7 were tested by MTT. Flow cytometry was used to analyze apoptosis of cells with Annexin V/PI double staining technique. Cell cloning ability was performed to reflect its biological behavior in each group.
  
  
  RESULTS
  Concentrations with inhibitory rates < 10% were selected as the reversal value of Smac-N7 peptide using MTT. The reversal folds were 2.52, 3.26, 3.67, and 5.4 in taxol + Smac-N7 (0.0390625, 0.078125, 0.15625, 0.3125 μg/mL, respectively), and concentrations of Smac-N7 and reversal folds appeared in an obvious positive correlation (r(s) = 1, p = 0.000). Apoptosis analyzed at 48 hours by flow cytometry showed the apoptotic rates in taxol and 0.0390625, 0.078125, 0.15625, and 0.3125 μg/mL Smac-N7 + taxol groups were 15.4 ± 1.09%, 20.8% ± 2.18%, 28.4% ± 4.17%, 37.64% ± 6.41%, and 46.6% ± 7.76%, respectively. Concentrations of Smac-N7 appeared to have negative correlations with PE and SF (r(s) = -1, p < 0.05), which showed that the cells' cloning ability in 0.3125 μg/mL Smac-N7 + taxol group was worse than that of other groups.
  
  
  CONCLUSIONS
  When combined with taxol, 0.3125 μg/mL Smac-N7 peptide may significantly increase taxol-induced apoptosis in chemoresistant A549/taxol lung cells at 48 hours, and is potentially useful as a reversal agent in lung cancer therapy.
authors.forename: Xiao-Mei
authors.initials: XM
authors.lastname: Li
authors.forename: Wen
authors.initials: W
authors.lastname: Zou
authors.forename: Run-Mei
authors.initials: RM
authors.lastname: Wang
authors.forename: Yun-Peng
authors.initials: YP
authors.lastname: Zhao
authors.forename: Zai-Yun
authors.initials: ZY
authors.lastname: Zhang
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Yu
authors.forename: Lan
authors.initials: L
authors.lastname: Ye
authors.forename: Ji-Hua
authors.initials: JH
authors.lastname: Wang
authors.forename: Yu-Hua
authors.initials: YH
authors.lastname: Jiang
authors.forename: Chuan-Liang
authors.initials: CL
authors.lastname: Peng
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000473:pathology*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004357:Drug Synergism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000138:chemical synthesis / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000188:drug therapy / Q000473:pathology*; D024101:Mitochondrial Proteins / Q000138:chemical synthesis / Q000494:pharmacology*; D017239:Paclitaxel / Q000494:pharmacology; D014410:Tumor Stem Cell Assay
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D017239:Paclitaxel