Semiconductor quantum dots (QDs) hold some advantages over conventional organic fluorescent dyes. Due to these advantages, they are becoming increasingly popular in the field of bioimaging. However, recent work suggests that cadmium based QDs affect cellular activity. As a substitute for cadmium based QDs, we have developed photoluminescent stable silicon quantum dots (Si-QDs) with a passive-oxidation technique. Si-QDs (size: 6.5 ± 1.5 nm) emit green light, and they have been used as biological labels for living cell imaging. In order to determine the minimum concentration for cytotoxicity, we investigated the response of HeLa cells. We have shown that the toxicity of Si-QDs was not observed at 112 µg ml(-1) and that Si-QDs were less toxic than CdSe-QDs at high concentration in mitochondrial assays and with lactate dehydrogenase (LDH) assays. Especially under UV exposure, Si-QDs were more than ten times safer than CdSe-QDs. We suggest that one mechanism for the cytotoxicity is that Si-QDs can generate oxygen radicals and these radicals are associated with membrane damages. This work has demonstrated the suitability of Si-QDs for bioimaging in lower concentration, and their cytotoxicity and one toxicity mechanism at high concentration.

Chronic systemic delivery of therapeutic proteins, such as inhibitors of angiogenesis, present a number of difficult pharmacological challenges. To overcome these problems for one such protein, we constructed retroviral and adenoviral vectors that express a novel, secretable form of the antiangiogenic protein, platelet factor 4 (sPF4). Vector-mediated sPF4 transduction selectively inhibits endothelial cell proliferation in vitro, and results in hypovascular tumors that grow slowly in vivo. Additionally, tumor-associated angiogenesis is inhibited and animal survival is prolonged, following transduction of established intracerebral gliomas by an sPF4-expressing adenoviral vector. These data support the concept that targeted antiangiogenesis, using virally mediated gene transfer, represents a promising strategy for delivering antiangiogenic therapy.

Chemokines are characterized by the homing activity of leukocytes to targeted inflammation sites. Recent research indicates that chemokines play more divergent roles in various phases of pathogenesis as well as immune reactions. The chemokine receptor, CCR1, and its ligands are thought to be involved in inflammatory bone destruction, but their physiological roles in the bone metabolism in vivo have not yet been elucidated. In the present study, we investigated the roles of CCR1 in bone metabolism using CCR1-deficient mice. Chemokines are initially identified as small cytokines that direct the homing of circulating leukocytes into sites of inflammation (1). Chemokines are now recognized to be major factors in inflammation and immune development as well as tumor growth, angiogenesis, and osteolysis. Chemokine receptors are expressed in a well organized spatiotemporal manner in various types of leukocytes, including lymphocytes, granulocytes, and macrophages. They facilitate the recruitment of these cells into inflammatory sites during the appropriate phase of inflammation.Recent findings indicate that chemokine receptors, including CCR1 7 and its related chemokines, CCL3 and CCL9, are involved in the pathogenesis of a variety of diseases. In particular, CCL3 (also called MIP-1␣), a major pro-inflammatory chemokine produced at inflammatory sites, appears to play a crucial role in pathological osteoclastogenesis (2, 3). In osteolytic bone inflammation (e.g. rheumatoid arthritis-associated bone destruction), CCL3 induces ectopic osteoclastogenesis (4) * This work was supported in part by Grant H19-nano-012 from the Ministry of Health, Labor and Welfare (to K. Y.) and by a research fellowship from the Japan Society for the Promotion of Science for Young Scientists (2007Scientists ( -2009 ( The abbreviations used are: CCR, C-C chemokine receptor; M-CSF, macrophage-colony stimulation factor; BALP, bone-specific alkaline phosphatase; CCL, C-C chemokine ligand; MCP-1, macrophage chemoattractant protein-1; MIP-1, macrophage inflammatory protein-1; CT, computed tomography; PTX, pertussis toxin from Bordetella pertussis; RANK, receptor activator of NF-B; RANKL, receptor activator of NF-B ligand; RANTES, regulated upon activation normal T expression and secreted; TRAP, tartrate-resistant acid phosphatase; NTx, N-telopeptides.

Recent data suggest that many tumors, such as malignant gliomas, have disrupted pRB function, either because of RB-1 gene mutations or as a result of mutations affecting upstream regulators of pRB such as cyclin D1 or p16/INK4a/MTS1 (ref. 1-5). Tumor suppression by pRB has been linked to its ability to repress E2F-responsive promoters such as the E2F-1 promoter. Thus, a prediction, which has not yet been demonstrated experimentally in vivo, is that E2F-responsive promoters should be more active in tumor cells relative to normal cells because of an excess of "free" E2F and loss of pRB/E2F repressor complexes. We demonstrate that adenoviral vectors that contain transgenes driven by the E2F-1 promoter can mediate tumor-selective gene expression in vivo, allowing for eradication of established gliomas with significantly less normal tissue toxicity than seen with standard adenoviral vectors. Our data indicate that de-repression of the E2F-1 promoter occurs in cancer cells in vivo, a finding that can be exploited to design viral vectors that mediate tumor-selective gene expression.