Knockdown of RNA binding protein musashi-1 leads to tumor regression in vivo

Gastroenterology. 2008 May;134(5):1448-58. doi: 10.1053/j.gastro.2008.02.057. Epub 2008 Mar 4.


Background & aims: In the gut, tumorigenesis is thought to arise from the stem cell population located near the base of intestinal and colonic crypts. The RNA binding protein musashi-1 (Msi-1) is a putative intestinal and progenitor/stem cell marker. Msi-1 expression is increased during rat brain development and in APC(min/+) mice tumors. This study examined a potential role of Msi-1 in tumorigenesis.

Methods: Msi-1 small interfering RNA (siRNA) was administered as a liposomal preparation to HCT116 colon adenocarcinoma xenografts in athymic nude mice and tumor volume was measured. Cell proliferation was assessed by hexosaminidase and 3-(4,5-dimethylthiazol 2-yl)-2,5-diphenyltetrazolium bromide MTT assays. siRNA-transfected cells were subjected to 12 Gy gamma-irradiation. Apoptosis was assessed by immunoreactive activated caspase-3 and mitosis was assessed by phosphorylated histone H3 staining. The tumor xenografts were stained similarly for phosphorylated histone H3, activated caspase-3, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling, Notch-1, and p21(WAF1). Furthermore, siRNA-transfected cells were subjected to cell-cycle analysis and Western blot analyses for Notch-1 and p21(WAF1).

Results: Knockdown of Msi-1 resulted in tumor growth arrest in xenografts, reduced cancer cell proliferation, and increased apoptosis alone and in combination with radiation injury. siRNA-mediated reduction of Msi-1 lead to mitotic catastrophe in tumor cells. Moreover, there was inhibition of Notch-1 and up-regulation of p21(WAF1) after knockdown of Msi-1.

Conclusions: Our results show the involvement of Msi-1 in cancer cell proliferation, inhibition of apoptosis, and mitotic catastrophe, suggesting an important potential mechanism for its role in tumorigenesis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenocarcinoma / genetics
  • Adenocarcinoma / metabolism
  • Adenocarcinoma / pathology*
  • Animals
  • Apoptosis
  • Biomarkers, Tumor
  • Blotting, Western
  • Cell Proliferation
  • Colorectal Neoplasms / genetics
  • Colorectal Neoplasms / metabolism
  • Colorectal Neoplasms / pathology*
  • Disease Progression
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Immunohistochemistry
  • Mice
  • Mice, Nude
  • Neoplasm Transplantation
  • Neoplasms, Experimental
  • Nerve Tissue Proteins / genetics*
  • Nerve Tissue Proteins / metabolism
  • RNA, Neoplasm / genetics*
  • RNA-Binding Proteins / genetics*
  • RNA-Binding Proteins / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transplantation, Heterologous


  • Biomarkers, Tumor
  • MSI1 protein, human
  • Msi1h protein, mouse
  • Nerve Tissue Proteins
  • RNA, Neoplasm
  • RNA-Binding Proteins