title: Low molecular weight heparin ablates lung cancer cisplatin-resistance by inducing proteasome-mediated ABCG2 protein degradation.
abstract: Cancer side population (SP) cells, which are often referred to as cancer stem cells, are thought to be responsible for lung cancer chemotherapy resistance, and currently no drug can specifically target these cells. We hypothesize low-molecular-weight heparin (LMWH) may affect the biological properties of SP cells and could be used to clinically target these cells. To test this, SP cells were isolated from cisplatin (DDP)-resistant lung adenocarcinoma A549/DDP cells by flow cytometric sorting. Compared to non-SP cells, SP cells formed increased numbers of colonies in vitro, and had a 1000-fold increase in tumorigenicity in vivo. Proliferation and apoptosis assays demonstrated LMWH had no significant effect on lung SP cell proliferation or apoptosis. However, LMWH reduced lung SP cell colony formation ability and protein expression of the multidrug transporter, ABCG2, by FACS and western blot analyses without affecting its mRNA levels by RT-PCR. Consistently, immunohistochemistry stainings of ABCG2 in LMWH-treated tumor tissues were significantly reduced compared with those in controls. Further, we found proteasomal inhibitor MG132, but not lysosomal inhibitors leupeptin and pepstatin A, could restore ABCG2 protein levels in LMWH-treated SP cells. These suggest LMWH ablates lung SP cell chemoresistance by proteasome-mediated reduction of ABCG2 protein levels without affecting its mRNA levels. We also determined LMWH combined with cisplatin could overcome cisplatin-resistance and induced lung SP cells apoptosis both in vitro and in vivo. This study provides an experimental basis for using a combination of LMWH, which targets lung SP cells, with chemotherapy to improve lung cancer survival.
authors: Department of Medical Oncology, No. 309 PLA Hospital, Beijing, PR China. qi_niu@hotmail.com
authors: Qi
authors: Q
authors: Niu
authors: Wei
authors: W
authors: Wang
authors: Yong
authors: Y
authors: Li
authors: Douglas M
authors: DM
authors: Ruden
authors: Fenghua
authors: F
authors: Wang
authors: Yue
authors: Y
authors: Li
authors: Fangying
authors: F
authors: Wang
authors: Jingying
authors: J
authors: Song
authors: Kun
authors: K
authors: Zheng
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D014408:Biomarkers, Tumor / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006495:Heparin, Low-Molecular-Weight / Q000494:pharmacology*; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D009363:Neoplasm Proteins / Q000378:metabolism*; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology; D059748:Proteolysis / Q000187:drug effects*; D016019:Survival Analysis; D023041:Xenograft Model Antitumor Assays
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D006495:Heparin, Low-Molecular-Weight; D007976:Leupeptins; D009363:Neoplasm Proteins; D061988:Proteasome Inhibitors; D046988:Proteasome Endopeptidase Complex; D002945:Cisplatin; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde