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Keywords:

  • 1, 25D3;
  • squamous cell carcinoma;
  • E-cadherin;
  • motility;
  • invasion;
  • metastasis

Abstract

BACKGROUND:

The active metabolite of vitamin D 1α,25-dihydroxycholecalciferol (1,25D3) has exhibited broad-spectrum antitumor activity in xenograft animal models. However, its activity against metastatic disease has not been extensively investigated.

METHODS:

Squamous cell carcinoma (SCC) or 1,25D3-resistant variant SCC-DR cells were treated with 1,25D3. Actin organization was examined by immunofluorescence assay. Cell migration was assessed by “wound” healing and chemotactic migration assays. Cell invasion was assessed by a Matrigel-based invasion assay and in situ zymography. Matrix metalloproteinase 2 (MMP-2) and MMP-9 expression and secretion were examined by immunoblot analysis and an enzyme-linked immunosorbent assay, respectively. E-cadherin expression was assessed by flow cytometry, immunoblot analysis, and immunohistochemistry. Knockdown of E-cadherin was achieved by small interfering RNA. An experimental metastasis mouse model was created by intravenous injection of tumor cells; and lung tumor development in the mice was assessed by magnetic resonance imaging, gross observation, and histology.

RESULTS:

SCC cellular morphology and actin organization were altered by 10 nM 1,25D3. 1,25D3 inhibited SCC cell motility and invasion, which were associated with reduced expression and secretion of MMP-2 and MMP-9, and 1,25D3 promoted the expression of E-cadherin. These findings were not observed in SCC-DR cells. Knock down of E-cadherin rescued 1,25D3-inhibited cell migration. Intravenous injection of SCC or SCC-DR cells resulted in the establishment of extensive pulmonary lesions in saline-treated C3H mice. Treatment with 1,25D3 resulted in a marked reduction in the formation of lung tumor colonies in mice that were injected with SCC cells, but not in mice that were injected with SCC-DR cells.

CONCLUSIONS:

1,25D3 suppressed SCC cell motility, invasion, and metastasis, partially through the promotion of E-cadherin-mediated cell-cell adhesion. Cancer 2013. © 2012 American Cancer Society.