Osteosarcoma is the most common primary malignant bone tumor seen in orthopaedic practice. Despite intensive treatments of chemotherapy and surgical excision, the current five-year survival rate is only 60% to 78%. We are investigating the correlation of vascular endothelial growth factor (VEGF) expression with osteosarcoma growth and metastasis and trying to explore a therapeutic strategy by blocking VEGF. Recent studies have suggested that a subpopulation of cancer stem cells (CSCs) play a role in cancer survival and metastasis. The purpose of my project is to examine if regulating the function of VEGF can change the population of CSCs in osteosarcoma. Using polymerase chain reaction and immunocytochemistry techniques, we will examine the expression of VEGF, CXCR4 and cancer stem cell marker CD133 at transcriptional and post-translational levels among different VEGF-expressing osteosarcoma cells. We will examine the tumor cell growth patterns and compare the subpopulation ratio of CD133+ cells after VEGF blockage.