Silencing of PKD1 Expression Increased Migration Ability of Human Osteosarcoma Cells

INTRODUCTION Osteosarcoma (OS) is one of high grade malignant bone tumors and is the most commonly encountered malignant bone tumor in children and adolescents. Significant numbers of patients of the disease eventually develop pulmonary metastases and succumb to the disease even after conventional multi-agent chemotherapy and surgical excision. Protein kinase D1 (PKD1), founding member of a new family of serine/threonine protein kinases, plays a role in several cellular processes such as apoptosis, immune regulation, cell proliferation, oxidative stress signaling, adhesion and motility. Recent studies suggest that PKD1 expression is low in several cancers, and that low expression of PKD1 may increase cell proliferation, migration and invasion of cancer cells. However, the role of PKD1 in musculoskeletal tumors has not been discussed. Matrix metalloproteinases (MMPs) are considered to play important roles in the matrix degradation for tumor growth, invasion, and tumorinduced angiogenesis. Several solid tumors display enhanced expression of MMPs, and recently clinical trials have been initiated on MMPinhibitors. Recent studies revealed that MMP-2 (gelatinase A) and MMP-9 (gelatinase B) are present in large quantities in OS, and suggest that both MMP-2 and MMP-9 play a critical role on cell invasion and metastases of OS. The purpose of this study was to evaluate the role of PKD1 on migration ability of human OS cells and to examine the relationship between PKD1 and MMPs in human OS cells.