title: Molecular features of doxorubicin-resistance development in colorectal cancer CX-1 cell line.
abstract: OBJECTIVE
  Resistance to chemotherapy is the key obstacle to the effective treatment of various cancers. Accumulating evidence suggests significant involvement of the epithelial-to-mesenchymal transition (EMT) in the chemoresistance of most cancer types. This study aimed at analyzing the gene expression profile of doxorubicin (DOX)-resistant colorectal cancer cells CX-1.
  
  
  METHODS
  DOX-resistant CX-1 cell sublines were acquired by stepwise increment of DOX concentrations in cell growth media. Global gene expression profiling was performed using human gene expression microarrays. The expression levels of individual genes were assessed by means of quantitative PCR (qPCR), while the DNA methylation pattern of several selected genes was determined by methylation-specific PCR.
  
  
  RESULTS
  Four DOX-resistant CX-1 sublines were established as a valuable tool for cell chemoresistance studies. Altered expression of the EMT, cell adhesion and motility, and chemoresistance-related genes was observed in DOX-resistant cells by genome-wide gene expression analysis. Besides, early and significant upregulation of the key EMT genes ZEB1 (5.8×; P<0.001) and CDH2 (6.2×; P=0.044) was identified by qPCR, with subsequent activation of drug transporter gene ABCC1 (3.3×; P=0.007) and cell stemness gene NANOG (2.4×; P=0.008). Downregulation of TET1 (2.1×; P=0.041) and changes in the methylation status of the p16 gene were also involved in the acquisition of cell resistance to DOX.
  
  
  CONCLUSIONS
  The results of our study suggest possible involvement of the key EMT and drug transporter genes in the early phase of cancer cell chemoresistance development.
authors.affiliation: Division of Human Genome Research Centre, Faculty of Natural Sciences, Vilnius University, Vilnius, Lithuania; Department of Biochemistry, Faculty of Natural Sciences, Vytautas Magnus University, Kaunas, Lithuania; National Cancer Institute, Vilnius, Lithuania.
authors.forename: Raimonda
authors.initials: R
authors.lastname: Kubiliūtė
authors.affiliation: Department of Biochemistry, Faculty of Natural Sciences, Vytautas Magnus University, Kaunas, Lithuania.
authors.forename: Indrė
authors.initials: I
authors.lastname: Šulskytė
authors.affiliation: Division of Human Genome Research Centre, Faculty of Natural Sciences, Vilnius University, Vilnius, Lithuania; Department of Biochemistry, Faculty of Natural Sciences, Vytautas Magnus University, Kaunas, Lithuania; National Cancer Institute, Vilnius, Lithuania.
authors.forename: Kristina
authors.initials: K
authors.lastname: Daniūnaitė
authors.affiliation: Department of Biochemistry, Faculty of Natural Sciences, Vytautas Magnus University, Kaunas, Lithuania.
authors.forename: Rimantas
authors.initials: R
authors.lastname: Daugelavičius
authors.affiliation: Division of Human Genome Research Centre, Faculty of Natural Sciences, Vilnius University, Vilnius, Lithuania; National Cancer Institute, Vilnius, Lithuania. Electronic address: sonata.jarmalaite@gf.vu.lt.
authors.forename: Sonata
authors.initials: S
authors.lastname: Jarmalaitė
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics*; D019175:DNA Methylation; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D044127:Epigenesis, Genetic; D020869:Gene Expression Profiling; D019942:Genes, p16 / Q000187:drug effects; D055106:Genome-Wide Association Study; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D059005:Topoisomerase II Inhibitors / Q000494:pharmacology*
chemical_list: D000903:Antibiotics, Antineoplastic; D059005:Topoisomerase II Inhibitors; D004317:Doxorubicin
keywords: CX-1; Colon cancer; Doxorubicin resistance; Epithelial-to-mesenchymal transition