Upregulation of PLOD2 promotes invasion and metastasis of osteosarcoma cells

Objective To investigate the relationship of procollagen-lysine 2-oxoglutarate 5-dioxygenase 2 (PLOD2) expression and the clinical characteristics of osteosarcoma, and explore the potential mechanism of tumour metastasis promoted by PLOD2. Methods The expression of PLOD2 in osteosarcoma tissues and paired adjacent tissues were detected by immunohistochemistry and qRT-PCR. Correlation of PLOD2 expression in osteosarcoma with the clinical pathologic features was analyzed by Chi square test and Kaplan-Meier analysis.Fibrillar collagen formation and collagen deposition in the tumor tissues were detected by picrosirius red staining. We transfected U-2OS cells with LV-vector, LV-over/PLOD2, sh-NC and sh-PLOD2. The expression of PLOD2 was detected by qRT-PCR. The impact of POLD2 on U-2OS cell invasion was determined by wound-healing assay and Transwell migration assay. The expressions of PLOD2/FAK/JAK2-STAT3 signal pathway related proteins were detected by western blotting. Results The high expression level of PLOD2 in osteosarcoma tissues was 72.5%, significantly higher than 0% in paired adjacent noncancerous tissues (P<0.01), the expression of PLOD2 was positively correlated with lymph node metastasis, pulmonary metastasis and poor outcome (P<0.01). The same results were also observed in qRT-PCR assay. The median survival time of patients with high expression of PLOD2 protein was 13 months, significantly shorter than 32 months of patients with low expression of PLOD2 (P<0.05). The result of picrosirius red staining showed that the percentage of collagen fiber deposition in the osteosarcoma tissue with high level of PLOD2 was (74.43+ 9.63)%, significantly higher than (9.67±1.28)% in tissue with low expression of PLOD2 (P<0.001). The result of wound-healing and Transwell migration assay showed that over-expression of PLOD2 markedly promoted the invasion, however, knockdown of PLOD2 suppressed the invasion of U-2OS cells (both P<0.01). The result of western blotting showed that over-expression of PLOD2 significantly increased the expression levels of p-FAK, p-JAK2, p-STAT3, but knockdown PLOD2 decreased the levels of p-FAK, p-JAK2, p-STAT3 in U-2OS cells. Conclusions Up-regulation of PLOD2 in osteosarcoma is correlated with lymphatic and distant metastasis. PLOD2 promotes invasion and metastasis of osteosarcoma might through FAK/JAK2-STAT3 signal pathway. Key words: PLOD2; Osteosarcoma; Invasion; Metastasis; Signal pathway