Differential migratory response of U-2 OS osteosarcoma cell to the various forms of platelet-derived growth factor

Molecular targets in therapy for human soft-tissue and bone sarcomas

Sarcomas represent a heterogeneous group of tumors with different natural histories and therapeutic approaches. Recent discoveries have identified molecular alterations in the pathogenesis of these tumors that lead to distinct effects on sarcoma cell biology. These tumor cell characteristics include independence from growth factors, evasion of apoptosis, and maintenance of genomic integrity. Inhibition of these molecular alterations represents a therapeutic opportunity to reverse the biologic basis of tumor formation in soft-tissue sarcomas and bone tumors.

Platelet-derived growth factor signaling and human cancer

Platelet-derived growth factor (PDGF) is a critical regulator of mesenchymal cell migration and proliferation. The vital functions of PDGFs for angiogenesis, as well as development of kidney, brain, cardiovascular system and pulmonary alveoli during embryogenesis, have been well demonstrated by gene knock-out approaches. Clinical studies reveal that aberrant expression of PDGF and its receptor is often associated with a variety of disorders including atherosclerosis, fibroproliferative diseases of lungs, kidneys and joints, and neoplasia. PDGF contributes to cancer development and progression by both autocrine and paracrine signaling mechanisms. In this review article, important features of the PDGF isoforms and their cell surface receptor subunits are discussed, with regards to signal transduction, PDGF-isoform specific cellular responses, and involvement in angiogensis, and tumorstromal interactions.

Insulin-like growth factors-I and -II stimulate chemotaxis of osteoblasts isolated from fetal rat calvaria

Repair and regeneration of damaged bone is believed to be regulated in part by growth factors stored in the bone matrix. These growth factors are synthesized and secreted by osteoblasts and are incorporated into the developing bone. This pool of stored growth factors is then released into the immediate area following resorption of the matrix. One of the initial steps in bone repair is the recruitment of osteoblasts to the repair site. Growth factors, such as TGF-beta and PDGF, which are present in bone matrix, have been shown to be chemotactic for osteoblasts. In this study, primary cultures of osteoblasts isolated from fetal rat calvaria were examined for chemotaxis in response to IGF-I and IGF-II. IGF-I stimulated a dose-dependent increase in osteoblast chemotaxis, while IGF-II stimulated chemotaxis maximally at the lowest concentration studied (0.1 ng/ml), and had no effect at the highest concentration studied (100 ng/ml). IGF-I and -II had no effect on osteoblast proliferation at any of the concentrations examined. These results indicate that IGFs may be playing an important role in the early stages of bone repair by stimulating osteoblast chemotaxis to the repair site.