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

ABSTRACT: 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.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.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.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.

SUBMITTER: Sureban SM

PROVIDER: S-EPMC2775069 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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

Sureban Sripathi M SM May Randal R Ramalingam Satish S Subramaniam Dharmalingam D Natarajan Gopalan G Anant Shrikant S Houchen Courtney W CW

Gastroenterology 20090513 2

<h4>Background & aims</h4>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.<h4>Methods</h4>Human tissue micro ...[more]

PMID: 19445940

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Project description:BACKGROUND:Achaete scute-like 2 (Ascl2), a basic helix-loop-helix (bHLH) transcription factor, controls the fate of intestinal stem cells. However, the role of Ascl2 in colon cancer progenitor cells remains unknown. The cell line HT-29 (47.5-95% of CD133(+) population) and LS174T (0.45% of CD133(+) population) were chosen for functional evaluation of Ascl2 in colon cancer progenitor cells after gene knockdown by RNA interference. METHODOLOGY/PRINCIPAL FINDINGS:Immunohistochemistry demonstrated that Ascl2 was significantly increased in colorectal adenocarcinomas. Downregulation of Ascl2 using RNA interference in cultured colonic adenocarcinoma HT-29 and LS174T cells reduced cellular proliferation, colony-forming ability, invasion and migration in vitro, and resulted in the growth arrest of tumor xenografts in vivo. The Ascl2 protein level in CD133(+) HT-29 cells was significantly higher than in CD133(-) HT-29 cells. Ascl2 blockade via shRNA interference in HT-29 cells (shRNA-Ascl2/HT-29 cells) resulted in 26.2% of cells staining CD133(+) compared with 54.7% in control shRNA-Ctr/HT-29 cells. The levels of 'stemness' associated genes, such as CD133, Sox2, Oct4, Lgr5, Bmi1, and C-myc, were significantly decreased in shRNA-Ascl2/HT-29 and shRNA-Ascl2/LS174T cells in vitro as well as in the corresponding tumor xenograft (CD133 was not performed in shRNA-Ascl2/LS174T cells). The shRNA-Ascl2/HT-29 cells had inhibited abilities to form tumorspheres compared with control. The microRNA (miRNAs) microarrays, identified 26 up-regulated miRNAs and 58 down-regulated miRNAs in shRNA-Ascl2/HT-29 cells. Expression levels of let-7b, miRNA-124, miRNA-125b, miRNA-17, miRNA-20a and miRNA-302b, involved in the regulation of 'stemness', were quantified with qPCR, which confirmed their identities. Restoration of miRNA-302b, via its mimic, led to the restoration of shRNA-Ascl2/HT-29 'stemness' characteristics, including tumorsphere formation and 'stemness' associated genes levels, and the recovery of cellular behaviors, including colony-forming ability, invasion and migration in vitro. CONCLUSIONS/SIGNIFICANCE:Ascl2 may be a potential target for the inhibition of colon cancer progenitor cells, and functions through a miR-302b-related mechanism.

Dataset Information

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

Publications

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

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