title: Epigenetic changes and alternate promoter usage by human colon cancers for expressing DCLK1-isoforms: Clinical Implications.
abstract: DCLK1 specifically marks colon/pancreatic cancers in mice, and is expressed by human colon adenocarcinomas (hCRCs). Down-regulation of DCLK1 results in loss of cancer-stem-cells (CSCs), and inhibits spheroidal/xenograft growths from hCRC-cells. The 5'-promoter of DCLK1-gene is reportedly hypermethylated in hCRCs, resulting in loss of expression of DCLK1-transcripts, originating from 5'(α)-promoter (termed DCLK1-L, in here). However, in mouse colon-tumors, 5'-promoter of DCLK1-gene remains unchanged, and DCLK1-L, originating from 5'(α)-promoter, is expressed. We hypothesized that elevated levels of DCLK1-protein in hCRC-cells, may be transcribed/translated from an alternate-promoter. Several in silico and molecular biology approaches were used to test our hypothesis. We report for the first time that majority of hCRCs express short-transcripts of DCLK1 (termed DCLK1-S, in here) from an alternate β-promoter in IntronV of the gene, while normal-colons mainly express DCLK1-L from 5'(α)-promoter. We additionally report an important role of β-catenin and TCF4/LEF binding-sites for activating (α)-promoter, while activated NF-κBp65 (bound to NF-κB-cis-element), activates (β)-promoter in cancer-cells. DCLK1-S expression was examined in a cohort of 92 CRC patients; high-expressors had significantly worse overall-survival compared to low-expressors. Our novel findings' regarding usage of alternate (β)-promoter by hCRCs, suggests that DCLK1-S may represent an important target for preventing/inhibiting colon-cancers, and for eliminating colon-CSCs.
authors.affiliation: Departments of Neuroscience and Cell Biology, UTMB, Galveston, TX.
authors.forename: Malaney R
authors.initials: MR
authors.lastname: O'Connell
authors.affiliation: Departments of Neuroscience and Cell Biology, UTMB, Galveston, TX.
authors.forename: Shubhashish
authors.initials: S
authors.lastname: Sarkar
authors.affiliation: Gastroenterology Division in Internal Medicine, UTMB, Galveston, TX.
authors.forename: Gurinder K
authors.initials: GK
authors.lastname: Luthra
authors.affiliation: Gastrointestinal Cancer Research Laboratory, Division of Gastroenterology, Department of Internal Medicine, Charles A. Sammons Cancer Center and Baylor Research Institute, Baylor University Medical Center, Dallas, Texas, USA.|Department of Gastrointestinal and Pediatric Surgery, Division of Reparative Medicine, Institute of Life Sciences, Graduate School of Medicine, Mie University, Mie 514-8507, Japan.
authors.forename: Yoshinaga
authors.initials: Y
authors.lastname: Okugawa
authors.affiliation: Department of Gastrointestinal and Pediatric Surgery, Division of Reparative Medicine, Institute of Life Sciences, Graduate School of Medicine, Mie University, Mie 514-8507, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Toiyama
authors.affiliation: Surgery, UTMB, Galveston, TX.
authors.forename: Aakash H
authors.initials: AH
authors.lastname: Gajjar
authors.affiliation: Pathology, UTMB, Galveston, TX.
authors.forename: Suimin
authors.initials: S
authors.lastname: Qiu
authors.affiliation: Gastrointestinal Cancer Research Laboratory, Division of Gastroenterology, Department of Internal Medicine, Charles A. Sammons Cancer Center and Baylor Research Institute, Baylor University Medical Center, Dallas, Texas, USA.
authors.forename: Ajay
authors.initials: A
authors.lastname: Goel
authors.affiliation: Departments of Neuroscience and Cell Biology, UTMB, Galveston, TX.
authors.forename: Pomila
authors.initials: P
authors.lastname: Singh
mesh_terms: D000368:Aged; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D019175:DNA Methylation; D000089742:Doublecortin-Like Kinases; D044127:Epigenesis, Genetic; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D045325:HCT116 Cells; D057809:HEK293 Cells; D006801:Humans; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; C117347:DCLK1 protein, human; D000089742:Doublecortin-Like Kinases; D017346:Protein Serine-Threonine Kinases