title: Re-expression of LKB1 in LKB1-mutant EKVX cells leads to resistance to paclitaxel through the up-regulation of MDR1 expression.
abstract: OBJECTIVE
  The tumor suppressor LKB1 has recently been shown to be involved in the regulation of microtubule dynamics, thus cancer cells with inactivated LKB1 may have developed a means to overcome dysregulated microtubule functions, making them intrinsically resistant to microtubule targeting agents. Here, we generated isogenic LKB1-wild type and mutant non-small cell lung cancer (NSCLC) cell lines to evaluate the role of LKB1 in paclitaxel resistance.
  
  
  METHODS
  SRB, flow cytometry and immunoblotting were used to assess cell proliferation and apoptosis in NSCLC cell lines after paclitaxel treatment. Expression of LKB1 was restored in LKB1-null cells by retrovirus infection and was reduced in LKB1-wild type cells by shRNA knock down.
  
  
  CONCLUSIONS
  The restoration of LKB1 in LKB1-null cells failed to promote paclitaxel-induced apoptosis in both p53-wild type and p53-mutant backgrounds, indicating that LKB1 was not required for paclitaxel-induced apoptosis. Interestingly, the re-establishment of LKB1 expression led to the up-regulation of class III beta-tubulin and MDR1 in EKVX cells. The up-regulation of MDR1 protein and transcripts in EKVX cells was specifically associated with the expression of wild-type LKB1 and mainly responsible for the increased cellular resistance to paclitaxel. However, the presence of LKB1 protein was not required to maintain this increased MDR1 expression even though there was no genetic amplification or promoter de-methylation of the ABCB1 locus in EKVX-LKB1-WT cells. These data suggest that LKB1 does not promote paclitaxel-induced apoptosis in most NSCLC cell lines. In contrast, in some NSCLC, the presence of LKB1 may facilitate increases in either MDR1 or class III beta-tubulin expression which can lead to paclitaxel resistance.
authors.affiliation: The Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 32322, United States; Department of Hepatobiliary Surgery, NanFang Hospital, Guangzhou, People's Republic of China; Department of Gastroenterology, NanFang Hospital, Guangzhou, People's Republic of China.
authors.forename: Kaisheng
authors.initials: K
authors.lastname: Mao
authors.affiliation: The Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 32322, United States; Department of Gastrointestinal Surgery, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, People's Republic of China.
authors.forename: Fakeng
authors.initials: F
authors.lastname: Liu
authors.affiliation: The Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 32322, United States.
authors.forename: Xiuju
authors.initials: X
authors.lastname: Liu
authors.affiliation: The Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 32322, United States.
authors.forename: Fadlo R
authors.initials: FR
authors.lastname: Khuri
authors.affiliation: The Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 32322, United States.
authors.forename: Adam I
authors.initials: AI
authors.lastname: Marcus
authors.affiliation: Department of Gastroenterology, NanFang Hospital, Guangzhou, People's Republic of China. Electronic address: lims@smu.edu.cn.
authors.forename: Mingsong
authors.initials: M
authors.lastname: Li
authors.affiliation: The Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 32322, United States. Electronic address: wzhou2@emory.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhou
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000235:genetics; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics; D017239:Paclitaxel / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D014404:Tubulin / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics*
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D014404:Tubulin; D017346:Protein Serine-Threonine Kinases; C109790:STK11 protein, human; D000091162:AMP-Activated Protein Kinase Kinases; D017239:Paclitaxel
keywords: Microtubule targeting agents; Multi-drug resistance; Paclitaxel resistance; Promoter methylation; Serine/threonine kinase; Tumor suppressor