Parathyroid hormone affects the fibroblast growth factor-proteoglycan signaling axis to regulate osteosarcoma cell migration.

Parathyroid hormone (PTH)(1-34), which has been established to have a dual effect on bone metabolism, was recently found to regulate osteosarcoma cell migration. A significant part of the bone anabolic action of PTH(1-34) is attributed to fibroblast growth factor (FGF)-2 stimulation. Furthermore, it was recently suggested that the FGF-proteoglycan axis may form an extracellular matrix-related regulatory feedback loop that controls osteoblastic lineage cell proliferation and execution of the osteogenic program. In this study, we investigated the possible participation of FGF-2 signaling in PTH(1-34)-dependent osteosarcoma cell migration. FGF-2 treatment of osteosarcoma cells resulted in a significant increase (P ≤ 0.01) in MG63 cell migration, similar to that caused by PTH(1-34). mRNA expression analysis of cells treated with PTH(1-34) showed a strong increase in FGF-2 transcript levels (P = 0.0015). Interestingly, the addition of FGF-2 to MG63 cells led to significant downregulation of small leucine-rich proteoglycan biglycan expression at both the mRNA (P ≤ 0.0001) and protein (60%) levels. In order to examine the significance of biglycan on MG63 cell migration, transfection with short interfering RNA specific for biglycan was performed, resulting in a significant increase (P ≤ 0.01) in the migration capacity of biglycan-deficient MG63 cells. In contrast, exogenous human recombinant biglycan strongly inhibited the migration of these cells (P ≤ 0.01). Finally, a direct correlation between PTH(1-34) action and biglycan expression was established by the finding of a significant decrease (P ≤ 0.01) in biglycan transcript levels in PTH(1-34)-treated cells. To summarize, the present study demonstrates a novel cooperative mechanism of PTH(1-34) and FGF-2 action that results in specific alteration of the biglycan extracellular matrix content to regulate osteosarcoma cell migration.

Parathyroid hormone (PTH) peptides through the regulation of hyaluronan metabolism affect osteosarcoma cell migration.

Parathyroid hormone (PTH) strongly stimulates hyaluronan (HA) synthesis and secretion of both normal and carcinogenic cells of the osteoblastic lineage and improves skeletal microarchitecture. HA, a glycosaminoglycan component of the extracellular matrix (ECM), is capable of transmitting ECM-derived signals to regulate cellular function. In this study, we investigated whether the changes of HA metabolism induced by PTH (1-34) and PTH (7-84) peptides in moderately MG-63 and well-differentiated Saos 2 osteosarcoma cell lines, are correlated to their migration capabilities. Our results demonstrate that intermittent PTH (1-34) treatment significantly (P < or = 0.01) supported the migration of MG-63 cells, increased their HA-synthase-2 (HAS2) expression (P < or = 0.001), and enhanced their high-molecular size HA deposition in the pericellular matrix. Both increased endogenous HA production (P < or = 0.01) and treatment with exogenous high-molecular weight HA (P < or = 0.05) correlated to a significant increase of MG-63 cell migration capacity. Transfection with siHAS2 showed that PTH (1-34), mainly through HAS2, enhanced HA and regulated MG-63 cell motility. Interestingly, continuous PTH (1-34) treatment stimulated both Saos 2 cell HAS2 (P < or = 0.001) and HAS1 (P < or = 0.001) isoform expression inhibited their HYAL2 expression (P < or = 0.001) and modestly (P < or = 0.05) enhanced their migration. Therefore, the PTH (1-34) administration mode appears to distinctly modulate the migratory responses of the MG-63 moderately and Saos 2 well-differentiated osteosarcoma cell lines. Conclusively, the obtained data suggest that there is a regulatory effect of PTH (1-34), in an administration mode-dependent manner, on HA metabolism that is essential for osteosarcoma cell migration.