Anti-cancer Effect of Unique Cartilage Matrix-associated Protein in Breast Cancer Cells Depends on γ-Carboxylation.

Abstract

Unique cartilage matrix-associated protein (UCMA), a recently discovered vitamin K-dependent protein (VKDP) with a large number of γ-carboxyglutamic acid (Gla) residues, is associated with ectopic calcifications. Although the function of VKDPs is related to their γ-carboxylation status, the carboxylation status of UCMA in breast cancer is still unknown. Here, we investigated the inhibitory effect of UCMA with differing γ-carboxylation status on breast cancer cell lines, such as MDA-MB-231, 4T1, and E0771 cells. Undercarboxylated UCMA (ucUCMA) was generated by mutating the γ-glutamyl carboxylase (GGCX) recognition sites. The ucUCMA and carboxylated UCMA (cUCMA) proteins were collected from culture media of HEK293-FT cells that had been transfected with mutated GGCX and wild-type UCMA expression plasmids, respectively. Boyden Transwell and colony formation assays were performed to evaluate cancer cell migration, invasion, and proliferation. Culture medium containing cUCMA protein inhibited the migration, invasion, and colony formation of MDA-MB-231 and 4T1 cells to a greater degree than medium containing ucUCMA protein. Significant reductions in the migration, invasion, and colony formation were also observed in cUCMA-treated E0771 cells compared to those in ucUCMA-treated cells. The inhibitory role of UCMA in breast cancer is closely related to its γ-carboxylation status. The results of this study may be a basis for the development of UCMA-based anti-cancer drugs.