A novel antibody against cancer stem cell biomarker, DCLK1-S, is potentially useful for assessing colon cancer risk after screening colonoscopy

Lab Invest. 2017 Oct;97(10):1245-1261. doi: 10.1038/labinvest.2017.40. Epub 2017 Apr 17.

Abstract

DCLK1 expression is critically required for maintaining growth of human colon cancer cells (hCCCs). Human colorectal tumors (CRCs) and hCCCs express a novel short isoform of DCLK1 (DCLK1-S; isoform 2) from β-promoter of hDCLK1 gene, while normal colons express long isoform (DCLK1-L; isoform 1) from 5'(α)-promoter, suggesting that DCLK1-S, and not DCLK1-L, marks cancer stem cells (CSCs). Even though DCLK1-S differs from DCLK1-L by only six amino acids, we succeeded in generating a monospecific DCLK1-S-Antibody (PS41014), which does not cross-react with DCLK1-L, and specifically detects CSCs. Subcellular localization of S/L-isoforms was examined by immune-electron-microscopy (IEM). Surprisingly, besides plasma membrane and cytosolic fractions, S/L also localized to nuclear/mitochondrial fractions, with pronounced localization of S-isoform in the nuclei and mitochondria. Sporadic CRCs develop from adenomas. Screening colonoscopy is used for detection/resection of growths, and morphological/pathological criteria are used for risk assessment and recommendations for follow-up colonoscopy. But, these features are not precise and majority of the patients will never develop cancer. We hypothesized that antibody-based assay(s), which identify CSCs, will significantly improve prognostic value of morphological/pathological criteria. We conducted a pilot retrospective study with PS41014-Ab, by staining archived adenoma specimens from patients who developed (high-risk), or did not develop (low-risk) adenocarcinomas within 10-15 years. PS41014-Ab stained adenomas from initial and follow-up colonoscopies of high-risk patients, at significantly higher levels (three to fivefold) than adenomas from low-risk patients, suggesting that PS41014-Ab could be used as an additional tool for assessing CRC risk. CRC patients, with high DCLK1-S-expressing tumors (by qRT-PCR), were reported to have worse overall survival than low expressers. We now report that DCLK1-S-specific Ab may help to identify high-risk patients at the time of index/screening colonoscopy.

MeSH terms

  • Antibodies / analysis
  • Antibodies / metabolism*
  • Biomarkers, Tumor / analysis*
  • Biomarkers, Tumor / metabolism
  • Colon / chemistry
  • Colon / pathology
  • Colon / surgery
  • Colonic Neoplasms / diagnosis*
  • Colonic Neoplasms / surgery
  • Colonoscopy
  • Doublecortin-Like Kinases
  • Early Detection of Cancer / methods*
  • HCT116 Cells
  • HEK293 Cells
  • Humans
  • Immunohistochemistry
  • Intracellular Signaling Peptides and Proteins / analysis*
  • Intracellular Signaling Peptides and Proteins / chemistry
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Protein Isoforms / analysis
  • Protein Isoforms / chemistry
  • Protein Isoforms / metabolism
  • Protein Serine-Threonine Kinases / analysis*
  • Protein Serine-Threonine Kinases / chemistry
  • Protein Serine-Threonine Kinases / metabolism
  • Retrospective Studies

Substances

  • Antibodies
  • Biomarkers, Tumor
  • Intracellular Signaling Peptides and Proteins
  • Protein Isoforms
  • DCLK1 protein, human
  • Doublecortin-Like Kinases
  • Protein Serine-Threonine Kinases