Restoration of S100A4 expression enhances invasive and metastatic potentials of COLO16 cutaneous squamous cancer cells.

BACKGROUND

S100A4 promotes cancer metastasis but is frequently silenced in human cutaneous squamous cell carcinomas/c-SCCs due to DNA methylation, which may explain the less metastasized property of c-SCCs.

OBJECTIVE

This study aims to check 1) whether the metastatic potential of S100A4-negative human c-SCC cells could be enhanced when S100A4 expression is restored in COLO16 c-SCC cells with S100A4 methylation and 2) the correlation of S100A4 expression and the differentiation grades and invasiveness of human c-SCC tumors.

METHODS

The motility and invasion of parent and transfected COLO16 cells are examined by the use of 24-well modified Boyden chambers, scratched wound healing assay and nude mouse transplantation tumor model. Meanwhile, the correlation of S100A4 expression with growth patterns and grade of differentiation of c-SCC surgical specimens are analyzed.

RESULTS

S100A4 expression is successfully restored in COLO16 cells after plasmid lipofectamine transfection. Transwell and scratched wound healing assays shows that the invasion and migration activities of S100A4-expressing transfectants are higher than that of parent COLO16 cells. Subcutaneous and foot pad c-SCC models are established by injecting 5 × 10^{6}/100~l parental and S100A4-expressing COLO16 cells to BALB/c-nu/nude mice, respectively. Histological examination confirms the differences of invasiveness between the parent cells and the transfectants. Regional lymph node metastases are found only in the mice bearing S100A4-expressing tumors. S100A4 expression levels and frequencies are significantly different (P< 0.001) between the well and the poorly differentiated c-SCCs and closely correlated with tumor invasion (P< 0.05).

CONCLUSIONS

S100A4 confers invasive and metastatic potentials on human c-SCCs. The low incidence of metastasis of c-SCCs, especially the well differentiated ones, might be due to the infrequent S100A4 expression. S100A4 can be regarded as a negative prognostic biomarker or a metastasis-risk factor of human c-SCCs.