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

Background/Aim: Unique cartilage matrixassociated protein (UCMA), a recently discovered vitamin Kdependent 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. Materials and Methods: 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. Results: 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. Conclusion: 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.