Selective blockade of DCAMKL-1 results in tumor growth arrest by a Let-7a MicroRNA-dependent mechanism

Gastroenterology. 2009 Aug;137(2):649-59, 659.e1-2. doi: 10.1053/j.gastro.2009.05.004. Epub 2009 May 13.


Background & aims: MicroRNAs (miRNAs) are non-coding RNAs that regulate gene expression. The tumor suppressor miRNA let-7a has been reported to be inhibited posttranscriptionally in embryonic stem cells and in human cancers. Microtubule-associated kinase DCAMKL-1 is a putative intestinal stem cell marker that is expressed in Apc(Min/+) adenomas. We investigated the role of DCAMKL-1 on expression of let-7a miRNA and the oncogene c-Myc and in tumorigenesis.

Methods: Human tissue microassay slides were immunostained for DCAMKL-1. HCT116 and SW480 cells were transfected with DCAMKL-1 small interfering RNA (siRNA) (si-DCAMKL-1) and analyzed for DCAMKL-1, c-Myc (using immunoblot and real-time reverse-transcription polymerase chain reaction [RT-PCR]), and pri-let-7a miRNA (using real-time RT-PCR) levels. A liposomal preparation of si-DCAMKL-1 was administered into HCT116 xenografts in nude mice, and tumor volumes were measured. A luciferase reporter assay, with a plasmid containing a let-7a-binding site at the 3' untranslated region, was utilized to measure let-7a in cell lines. Cells were isolated from normal mouse intestine using DCAMKL-1 and fluorescence-activated cell sorting (FACS) and subjected to pri-let-7a miRNA analysis.

Results: Expression of DCAMKL-1 was increased in human colorectal cancers. siRNA-mediated blockade of DCAMKL-1 resulted in H tumor xenograft growth arrest, increased pri-let-7a miRNA, a corresponding decrease in luciferase activity, and decreased expression of the oncogene c-Myc. DCAMKL-1(+) cells isolated by FACS demonstrated a significant decrease in pri-let-7a miRNA, compared with more differentiated cells.

Conclusions: DCAMKL-1 is a negative regulator of let-7a miRNA biogenesis in intestinal stem and colorectal cancer cells; it could represent a novel target for anti-cancer stem cell-based strategies.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Analysis of Variance
  • Animals
  • Blotting, Western
  • Cell Line, Tumor
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / physiopathology
  • Disease Models, Animal
  • Female
  • Flow Cytometry
  • Gene Expression Regulation, Neoplastic
  • HCT116 Cells
  • Humans
  • Immunohistochemistry
  • Lysosomal-Associated Membrane Protein 1 / genetics
  • Lysosomal-Associated Membrane Protein 1 / metabolism*
  • Mice
  • Mice, Nude
  • MicroRNAs / biosynthesis
  • MicroRNAs / genetics*
  • MicroRNAs / metabolism
  • Probability
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Random Allocation
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sensitivity and Specificity
  • Transplantation, Heterologous
  • Tumor Burden / genetics


  • Lysosomal-Associated Membrane Protein 1
  • MicroRNAs
  • RNA, Messenger
  • mirnlet7 microRNA, human