Synergistically Anti-metastatic Effect of 5-Flourouracil on Colorectal Cancer Cells via Calcium-mediated Focal Adhesion Kinase Proteolysis

Abstract

Aim: To investigate the possibility of enhancing an anti-metastatic effect of 5-fluorouracil (5-FU) on colorectal cancer (CRC) cells by combining it with continuous calcium supplementation. Materials and Methods: Optimal doses of 5-FU with/without lactate salt (CaLa) were determined via clonogenicity and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assays using human CRC cells cultured on normal or low-attachment plates. Invasion and migration assays confirmed the enhanced anti-metastatic effect of combining 5-FU and CaLa. Western blot analysis for elements of the focal adhesion kinase (FAK) signaling cascade and epithelial-mesenchymal transition (EMT) markers was used to investigate the underlying mechanism. Results: 5-FU (2.5 mu M) had no antitumor activity against unanchored CRC cells, while it significantly suppressed anchorage-dependent cell proliferation. In contrast, treatment with CaLa (2.5 mM), alone and in combination with 5-FU, exerted antitumor activity against both anchored and unanchored CRC cells via calcium-mediated FAK proteolysis and inhibition of EMT markers, such as vimentin and SNAIL. Conclusion: Calcium supplementation represents a method of enhancing the potency of existing antitumor agents such as 5-FU, augmenting their clinical effectiveness.