Overexpression of carboxypeptidase X M14 family member 2 predicts an unfavorable prognosis and promotes proliferation and migration of osteosarcoma

BACKGROUND: Carboxypeptidase X, M14 family member 2 (CPXM2), has been associated with several human developmental disorders. However, whether CPXM2 is involved in oncogenesis or tumor progression remains unclear. Currently, the clinical relevance and function of CPXM2 in human osteosarcoma were investigated. MATERIALS AND METHODS: The expression of CPXM2 in osteosarcoma cell lines and tissues were explored by immunohistochemistry and western blotting assays. A eukaryotic expression plasmid was transfected into fetal osteoblast cells to overexpress CPXM2 and the endogenous CPXM2 in osteosarcoma cells was silenced through an RNA interference (RNAi) method transfection. These transfections were validated via western blotting, and the expression levels of several key molecules involved in the epithelial mesenchymal transition was also determined via western blotting. The expression levels of CPXM2 in a fetal osteoblast cell line with CPXM2 overexpressing and an osteosarcoma CPXM2-knockout cell line was confirmed via reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blotting and immunofluorescence. The malignant phenotype of osteosarcoma cells was indicated by the cholecystokinin octapeptide, colony formation assay, scratch wound healing assay, and Transwell® migration assay. RESULTS: We found that CPXM2 was overexpressed in osteosarcoma and that the overexpression was associated with an unfavorable prognosis and tumor node metastasis staging. The knockdown of CPXM2 in cultured osteosarcoma cells significantly impeded cell proliferation and migration. In addition, the upregulation of CPXM2 in fetal osteoblast cells significantly promoted cell proliferation and migration. Besides, western blotting results revealed that several key molecules involved in the epithelial mesenchymal transition (EMT) were regulated by CPXM2. CONCLUSION: Taken together, these results imply an active role for CPXM2 in promoting tumor aggressiveness via epithelial to mesenchymal transition (EMT) modulation in osteosarcoma.