Localization of pigment epithelium-derived factor in growing mouse bone

Constitutive overexpression of pigment epithelium-derived factor inhibition of ocular melanoma growth and metastasis

PURPOSE

Pigment epithelium-derived factor (PEDF) is known to be an angiogenesis suppressor and to have antitumor effects. This study investigates whether constitutive overexpression of PEDF inhibits the growth and hepatic micrometastasis of ocular melanoma.

METHODS

Real-time RT-PCR was used to detect endogenous PEDF expression in human uveal melanoma cell lines and mouse melanoma cells. A lentiviral vector containing a mouse PEDF expression sequence was constructed and transduced into mouse melanoma cells in vitro. Transgene expression was assessed by Western blot analysis. Angiogenesis and transendothelial migration assays were performed in constitutively stable PEDF-overexpressing cells and transduced lentiviral vector control cells. The size and microvessel density of the ocular tumor and the number of hepatic micrometastasis were compared between the mice inoculated with PEDF-overexpressing tumor cells and those mice with the control cell line.

RESULTS

Four human uveal melanoma and three mouse melanoma cell lines were found to express PEDF mRNA. Endogenous overexpressing PEDF melanoma cells lost the ability to migrate and form tubes in vitro. In the animal experiment, the size of the ocular melanoma and the number of hepatic micrometastasis were decreased and microvessel density was also reduced in mice inoculated with constitutively overexpressing PEDF melanoma cells.

CONCLUSIONS

Lentivirus-mediated gene transfer of PEDF decreased the growth of ocular melanoma and its hepatic micrometastasis in a mouse ocular melanoma model. Dual antitumor/antiangiogenic activities of PEDF suggest that PEDF gene therapy may be considered an approach for the treatment of ocular melanoma.

Differences in matrix composition between calvaria and long bone in mice suggest differences in biomechanical properties and resorption: Special emphasis on collagen

The mammalian skeleton consists of bones that are formed in two different ways: long bones via endochondral ossification and flat bones via intramembranous ossification. These different formation modes may result in differences in the composition of the two bone types. Using the 2D-difference in gel electrophoresis technique and mass spectrometry, we analyzed the composition of murine mineral-associated proteins of calvaria and long bone. Considerable differences in protein composition were observed. Flat bones (calvariae) contained more soluble collagen (8x), pigment epithelium derived factor (3x) and osteoglycin (4x); whereas long bones expressed more chondrocalcin (3x), thrombospondin- 1 (4x), fetuin (4x), secreted phosphoprotein 24 (3x), and thrombin (7x). Although cystatin motifs containing proteins, such as secreted phosphoprotein 24 and fetuin are highly expressed in long bone, they did not inhibit the activity of the cysteine proteinases cathepsin B and K. The solubility of collagen differed which coincided with differences in collagen crosslinking, long bone containing 3x more (hydroxylysine)-pyridinoline. The degradation of long bone collagen by MMP2 (but not by cathepsin K) was impaired. These differences in collagen crosslinking may explain the differences in the proteolytic pathways osteoclasts use to degrade bone. Our data demonstrate considerable differences in protein composition of flat and long bones and strongly suggest functional differences in formation, resorption, and mechanical properties of these bone types.

PEDF-derived synthetic peptides exhibit antitumor activity in an orthotopic model of human osteosarcoma

Pigment epithelium-derived factor (PEDF) is one of the most potent inhibitors of angiogenesis, and has recently been demonstrated to have an important multifunctional role in tumor growth, invasion, and metastasis. However, relatively little is known of mechanisms through which PEDF exerts its antitumor activity. Therefore, with the aim of identifying potential functional epitopes specifically against osteosarcoma, we evaluated the bioactivity of four 25-mer synthetic PEDF-derived peptides (termed StVOrth-1, -2 -3, and -4) against a human osteosarcoma cell line, SaOS-2. We found that StVOrth-2 (residues 78-102) predominantly inhibited tumor cell proliferation, while StVOrth-3 (residues 90-114) markedly increased cellular adhesion to collagen type-1, with StVOrth-4 (residues 387-411) demonstrating most significant inhibition of Matrigel invasion. Furthermore, we show that StVOrth-1 (residues 40-64), -2 and -3 induce osteoblastic differentiation, evidenced by increased mineralized nodule formation. Interestingly, although no peptide inhibited angiogenesis in the tube formation assay, StVOrth-3 and -4 markedly suppressed VEGF expression. We further tested the activity of StVOrth-2 and StVOrth-3 in vivo, in an orthotopic model of osteosarcoma and found that both peptides significantly inhibited primary tumor growth and the development of pulmonary metastases. Together these results provide greater insight into the potential mechanisms through which PEDF exerts its antitumor function. Furthermore, this raises the possibility of developing short PEDF fragments as lead compounds for the treatment of osteosarcoma.

Steroid-sparing effect of pimecrolimus cream 1% in children with severe atopic dermatitis

OBJECTIVE

To investigate if pimecrolimus cream 1% reduces the need for steroids in the long-term management of severe pediatric atopic dermatitis (AD).

METHODS

A total of 184 pediatric patients (aged 2-17 years) with a history of severe AD according to Rajka and Langeland were enrolled. Patients were randomized to treatment with pimecrolimus cream or vehicle cream for a 24-week period. Prednicarbate 0.25% was applied as rescue medication.

RESULTS

Patients on pimecrolimus required steroids on a mean of 29% of study days, compared with 35% of patients on vehicle (p = 0.1841). On the head and neck only, the respective figures were 10 versus 19% (p = 0.0009). In patients enrolled with acute severe disease (Investigator's Global Assessment > or = 4), steroids were used on 28% of the days in the pimecrolimus group compared to 45% in the control group (p = 0.0024). On the head and neck, steroids were used on 10% of study days with pimecrolimus versus 30% with vehicle (p < 0.0001).

CONCLUSION

The results indicate that the need for topical steroids on the head and neck is reduced with pimecrolimus cream 1% in the management of severe pediatric AD according to the definition of Rajka and Langeland.

Expression of pigment-epithelium-derived factor during kidney development and aging

Inhibitors and stimulators of endothelial cell growth are essential for the coordination of blood vessel formation during organ growth and development. In the adult kidney, one of the major inhibitors of angiogenesis is pigment-epithelium-derived factor (PEDF). We have analyzed the expression and distribution of PEDF during various stages of renal development and aging with particular emphasis on the formation of functional glomeruli. We show that PEDF gene expression and protein levels in the kidney significantly increase with age. We have detected PEDF in the mesenchyme and endothelial cells at all developmental stages studied, in all regions of the nephrogenic zone in which the formation of new blood vessels is associated with the development of nephrons and collecting ducts, and in mature podocytes in the adult kidney. Our results are the first to suggest that PEDF is important in early renal postnatal development, that it could be relevant to the maturation of glomerular function and the filtration barrier formed by these cells, and that it may serve as an anti-angiogenic modulator during kidney development.

Pigment epithelium-derived factor overexpression inhibits orthotopic osteosarcoma growth, angiogenesis and metastasis

Despite significant improvements, the current management of primary osteosarcoma is still limited by the development of metastatic disease, which occurs in approximately 30% of patients despite aggressive multiagent chemotherapy and tumor-ablative surgery. Therefore, there is a need for the development of novel agents to improve the outcome of these patients. Pigment epithelium-derived factor (PEDF) has been shown to be one of the most potent inhibitors of angiogenesis, and more recently has demonstrated a functional role in tumor growth, invasion and metastasis. In this study we report, for the first time, the multitargeted role of PEDF in the inhibition of growth, angiogenesis and metastasis of two orthotopic models of osteosarcoma (rat UMR 106-01 and human SaOS-2). Through stable plasmid-mediated gene transfer of full-length human PEDF, we show that PEDF overexpression significantly reduced tumor cell proliferation (P<0.05) and Matrigel invasion (UMR(PEDF), P<0.001; SaOS(PEDF), P<0.05) and increased adhesion to collagen type-1 (P<0.01), in vitro. In vivo, PEDF overexpression dramatically suppressed orthotopic osteosarcoma growth (P<0.05) and the development of spontaneous pulmonary metastases (UMR(PEDF), P<0.05; SaOS(PEDF), P<0.001). Furthermore, PEDF-overexpressing tumors exhibited reduced intratumoral angiogenesis, evidenced by a significant decrease in microvessel density (P<0.05). Therefore, together these results suggest that PEDF may be a new and promising approach for the treatment of osteosarcoma.

Inhibition of orthotopic osteosarcoma growth and metastasis by multitargeted antitumor activities of pigment epithelium-derived factor

Osteosarcoma is major cause of cancer-related death in the pediatric age group, and this is due to the development of pulmonary metastases that fail to be eradicated with current treatment regimes. Although there have been significant improvements in the long-term survival of such patients, 25-50% with initially non-metastatic disease, subsequently develop metastases and this remains the major cause of death for these patients. In this study, we report the multimodal activity of pigment epithelium-derived factor (PEDF) in inhibiting osteosarcoma growth, angiogenesis and metastasis. In vitro, we found that administration of recombinant PEDF (rPEDF) on two osteosarcoma cell lines (rat UMR 106-01 and human SaOS-2) significantly reduced tumor cell proliferation and increased apoptosis, as well as decreased cell invasion, angiogenesis, and increased adhesion to collagen type-1. Administration of rPEDF upregulated the mRNA expression of phenotypic osteoblast differentiation markers (ALP, pro-alpha(1) collagen and osteocalcin) in a pre-osteoblastic cell line, UMR 201, and also increased mineralized nodule formation in both UMR 106-01 and SaOS-2. In vivo, rPEDF dramatically suppressed primary osteosarcoma growth and the development of macroscopic pulmonary metastases in an orthotopic model of human osteosarcoma (SaOS-2). Interestingly, no activity was seen in tumors grown subcutaneously, suggesting a paracrine interaction between PEDF and the bone microenvironment. Preliminary pharmacoevaluation studies demonstrated rPEDF stability within media containing serum and osteosarcoma cells, and no gross systemic toxicity was observed in vivo with rPEDF administration. These results suggest that PEDF is emerging as an attractive and clinically appealing drug candidate for the treatment of osteosarcoma.

Anti-angiogenic therapy for osteosarcoma

Even in tumor centers using established protocols, the survival rate of patients with osteosarcoma has not improved significantly in recent years. Novel therapies are urgently needed as an adjunct to conventional treatment modalities, to reduce the dose and subsequent toxicity associated with current chemotherapy, improve local disease control, prevent development of metastases, and offer an alternative treatment for those tumors that are poorly responsive to chemotherapy. Anti-angiogenic therapy currently holds great potential in conjunction with conventional treatment modalities for osteosarcoma. Specifically, anti-angiogenic factors derived from cartilage, a natural barrier to osteosarcoma invasion, may have important therapeutic applications in osteosarcoma.

Cell Cycle Genes PEDF and CDKN1C in Growing Deer Antlers

Deer antlers are the only mammalian appendage to display an annual cycle of full regeneration. The growth phase in antler involves the rapid proliferation of several tissues types, including epidermis, dermis, cartilage, bone, blood vessels, and nerves. Antlers thus provide an excellent model to study the developmental regulation of these tissues. We describe here the identification of two genes, pigment epithelium-derived factor (PEDF) and cyclin-dependent kinase inhibitor 1C (CDKN1C), both of which are known to be involved in cell proliferation and differentiation. These genes were identified as the result of screening an expressed sequence tag database derived from a cDNA library enriched for sequences from the growing antler tip. PEDF mRNA was detected in developing skin, cartilage, and bone during endochondral ossification. PEDF mRNA was not detected within endothelial cells that exhibited positive immunoreactivity to a CD146 antibody. CDKN1C mRNA was expressed by only the immature chondrocytes within the precartilage region. These results suggested that PEDF and CDKN1C are important genes involved in cell proliferation and differentiation during antler growth.

Pigment epithelium-derived factor as a multifunctional antitumor factor

The design of new therapeutic strategies for cancer treatment is based on the combination of drugs directed against different tumor compartments, including the tumor cells themselves and components of the stroma, such as the tumor vasculature. Indeed, several antiangiogenic compounds have entered clinical trials for use alone or in combination with conventional cytotoxic drugs. Pigment epithelium-derived factor (PEDF) is a multifunctional natural peptide with complex neurotrophic, neuroprotective, antiangiogenic, and proapoptotic biological activities, any of which could potentially be exploited for therapeutic purposes. This review summarizes recent studies that reveal the antitumor potential of PEDF based on its antiangiogenic properties and its newly discovered direct antitumor effects, which involve the induction of differentiation or apoptosis in tumor cells. We also discuss possible therapeutic applications of PEDF, based on these mechanistic insights and on the identification of functional domains that retain specific biological activities.

PEDF: a potential molecular therapeutic target with multiple anti-cancer activities

Pigment epithelium-derived factor (PEDF) is an endogenously produced protein that is widely expressed throughout the human body, and exhibits multiple and varied biological activities. Already established as a potent anti-angiogenic molecule, PEDF has recently shown promise as a potential anti-tumour agent, causing both direct and indirect tumour suppression. Here, we explore the unique anti-tumour properties of PEDF and discuss its role as an effective anti-angiogenic, anti-proliferative and pro-differentiation factor. We also discuss the prospects for PEDF therapy and the need for a closer evaluation of issues such as delivery, stability and potential toxicity.

Pigment epithelium-derived factor: a multimodal tumor inhibitor

Pigment epithelium-derived factor (PEDF), a noninhibitory member of the serine protease inhibitor (serpin) family, is a well-known potent endogenous inhibitor of angiogenesis. It has been known for years to be aberrantly expressed in ocular disorders, but in recent years, down-regulation has been shown to be prevalent in a range of cancers as well. This review describes the trimodal anticancer activities of this interesting protein: antiangiogenesis, apoptosis-mediated tumor suppression, and tumor cell differentiation. The key to successful antitumor therapy with this protein is the ability to synthesize the recombinant form of the protein (or its active shortened forms) and deliver at therapeutic doses or alternatively to use gene transfer technology to prolong the effect in vivo. Although there is a substantial amount of work carried out at the preclinical stage with this protein, more groundwork has to be done before PEDF is tested against cancer in clinical trials.

Commonly used mouse models of osteosarcoma

Osteosarcoma is the commonest primary tumour of bone and the second highest cause of cancer-related death in the paediatric age group. Little is known of the aetiology of human osteosarcoma and lesser still of the various interactions that occur between host and tumour cells that govern growth and progression of osteosarcoma in vivo. Although numerous osteosarcoma cell lines have been established and characterized in vitro, some as far back as in the 1960s, there is a scarcity of reliable and reproducible in vivo animal models that mimics all aspects of the human condition at the temporal, physiological and histopathological level, hence, making the accurate testing of therapeutic strategies difficult. Given that osteosarcoma is a disease that affects young people and better disease management strategies are essential, development of a robust human osteosarcoma model is long overdue.