RNA interference against polo-like kinase-1 in advanced non-small cell lung cancers

Worldwide, approximately one and a half million new cases of lung cancer are diagnosed each year, and about 85% of lung cancer are non-small cell lung cancer (NSCLC). As the molecular pathogenesis underlying NSCLC is understood, new molecular targeting agents can be developed. However, current therapies are not sufficient to cure or manage the patients with distant metastasis, and novel strategies are necessary to be developed to cure the patients with advanced NSCLC.RNA interference (RNAi) is a phenomenon of sequence-specific gene silencing in mammalian cells and its discovery has lead to its wide application as a powerful tool in post-genomic research. Recently, short interfering RNA (siRNA), which induces RNAi, has been experimentally introduced as a cancer therapy and is expected to be developed as a nucleic acid-based medicine. Recently, several clinical trials of RNAi therapies against cancers are ongoing. In this article, we discuss the most recent findings concerning the administration of siRNA against polo-like kinase-1 (PLK-1) to liver metastatic NSCLC. PLK-1 regulates the mitotic process in mammalian cells. These promising results demonstrate that PLK-1 is a suitable target for advanced NSCLC therapy.     

Possible translocation of periodontal pathogens into the lymph nodes draining the oral cavity

Numerous publications have reported the presence of periodontopathogenic bacteria in peripheral and central vascular lesions. However, it is unclear how this bacterial translocation occurs. The objective of this study was to investigate whether periodontopathic bacteria are translocated to lymph nodes proximal to the oral cavity. Obtaining lymph node samples is not ethically feasible unless they are excised as part of the surgical management of patients with cancer. This study analyzed formalin-fixed and paraffin-embedded lymph nodes, histologically negative for cancer cell invasion, that were excised from 66 patients with histories of head and neck cancer. Real-time PCR was performed to amplify the 16S ribosomal DNA fragments from Porphyromonas gingivalis, Treponema denticola, Aggregatibacter actinomycetemcomitans, Tannerella forsythia, and Prevotella intermedia. The relationship between bacterial detection and cancer severity, gender, and the use of anti-cancer therapy was examined by Fisher??s exact test. P. gingivalis, T. forsythia, and P. intermedia were present in 17%, 8%, and 8% of the samples of submandibular and submental lymph nodes, respectively. There were no significant relationships between bacterial detection and the cancer disease status, patient gender or use of anticancer therapy. According to these data, it appears that the translocation of periodontopathic bacteria may occur via lymphatic drainage, irrespective of the cancer disease status, gender or anticancer therapy.     

Widespread expression of γ-glutamyl cyclotransferase suggests it is not a general tumor marker

γ-Glutamyl cyclotransferase (GGCT) contributes to the γ-glutamyl cycle that regulates glutathione metabolism. Although GGCT has been implicated in several studies as a possible cancer marker, little is known about its distribution in cells and tissues. The authors investigated GGCT expression in normal tissues and tumors using Western blots and immunohistochemistry with a novel anti-GGCT monoclonal antibody. GGCT was detected in most organs and was mainly found in epithelial cells. Although the intracellular distribution was mainly cytoplasmic, in some situations, nuclear staining was strong. A significant increase in the expression of GGCT was found in tumors of the lung, esophagus, stomach, bile duct, and uterine cervix. In contrast, there was a significant decrease in expression in renal and urothelial tumors. These results suggest that GGCT may be a biomarker of tumors in a limited range of organs.     

CDK phosphorylation of Drc1 regulates DNA replication in fission yeast

Cyclin-dependent kinases (CDKs) are absolutely required for DNA replication in eukaryotic cells. CDKs are thought to activate one or more replication factors, but the identities of these proteins are unknown. Here we describe fission yeast Drc1, a protein required for DNA replication that is phosphorylated by Cdc2. Drc1 depletion leads to catastrophic mitotic divisions with incompletely replicated DNA, indicating that Drc1 is required for DNA synthesis and S-M replication checkpoint control. Drc1 associates with Cdc2 and is phosphorylated at the onset of S phase when Cdc2 is activated. Mutant Drc1 that lacks CDK phosphorylation sites is nonfunctional and fails to interact with Cut5 replication factor. These data suggest that Cdc2 promotes DNA replication by phosphorylating Drc1 and regulating its association with Cut5.     

Dendritic cell-based combined immunotherapy with autologous tumor-pulsed dendritic cell vaccine and activated T cells for cancer patients: rationale, current progress, and perspectives

Effective adoptive cancer immunotherapy depends on an ability to generate tumor-antigen-presenting cells and tumor-reactive effector lymphocytes and to deliver these effector cells to the tumor. Dendritic cells (DCs) are the most potent antigen-presenting cells, capable of sensitizing T cells to new and recall antigens. Many studies have shown that tumors express unique proteins that can be loaded on DCs to trigger an immune response. The current experimental and clinical statuses of adoptive transfer of tumor antigen-pulsed DCs and vaccine-primed activated T cells are summarized herein. Clinical trials of antigen-pulsed DCs have been conducted in patients with various types of cancer, including non-Hodgkin lymphoma, multiple myeloma, prostate cancer, renal cell carcinoma, malignant melanoma, colorectal cancer, and non-small cell lung cancer. These studies have shown that antigen-loaded DC vaccination is safe and promising for the treatment of cancer. In addition, tumor vaccine-primed T cells have been shown to induce antitumor activity in vivo. Several clinical studies are being conducted on the use of vaccine-primed T cells such as tumor-drainage lymph node. It is reasonable to consider using both tumor antigen-pulsed DCs and vaccine-primed lymphocytes as adjuvants. We are now investigating the use of autologous whole tumor antigen-pulsed DCs and the DC vaccine-primed activated lymphocytes in patients with multiple metastasis of solid tumors.     

Exosomes secreted from monocyte-derived dendritic cells support in vitro naive CD4+ T cell survival through NF-(kappa)B activation

We investigated the effect of exosomes secreted from human monocyte-derived dendritic cells (Mo-DCs), which are generated from PBMCs in response to treatment with GM-CSF and IL-4, on naive CD4+ T cell survival in vitro. Exosomes isolated from culture supernatants of Mo-DCs (>90% purity) were purified with anti-HLA-DP, -DQ, -DR-coated paramagnetic beads. Purified exosomes prolonged the survival of naive CD4+ T cells (>98% purity) in vitro. Treatment with neutralizing mAb against HLA-DR significantly decreased the supportive effect of purified exosomes on CD4+ T cell survival. Exosomes increased nuclear translocation of NF-(kappa)B in naive CD4+ T cells, and NF-(kappa)B activation was significantly suppressed by anti-HLA-DR mAb or NF-(kappa)B inhibitor pyrrolidine dithiocarbamate (PDTC). In addition, PDTC inhibited the effect of exosomes on naive CD4+ T cell survival. Thus, exosomes secreted by Mo-DCs appear to support naive CD4+ T cell survival via NF-(kappa)B activation induced by interaction of HLA-DR and TCRs.     

A hamster temperature-sensitive alanyl-tRNA synthetase mutant causes degradation of cell-cycle related proteins and apoptosis

We have isolated a temperature-sensitive alanyl-tRNA synthetase mutant from hamster BHK21 cells, designated as ts ET12. It has a single nucleotide mutation, converting the 321st amino acid residue, 321Gly, to Arg. The mutation was localized between two RNA-binding domains of alanyl-tRNA synthetase. Thus far, we have isolated two temperature-sensitive aminoacyl-tRNA synthetase mutants from the BHK21 cell line: ts BN250 and ts BN269. They are defective in histidyl- and lysyl-tRNA synthetase respectively. Both mutants rapidly undergo apoptosis at the nonpermissive temperature, 39.5 degrees C. ts ET12 cells, however, did not undergo apoptosis until 48 h after a temperature-shift to 39.5 degrees C, while mutated alanyl-tRNA synthetase of ts ET12 cells was lost within 4 h. Loss of the mutated alanyl-tRNA synthetase was inhibited by a ubiquitin-dependent proteasome inhibitor, MG132, and by a protein-synthesis inhibitor, cycloheximide. Cell-cycle related proteins were also lost in ts ET12 cells at 39.5 degrees C, as shown in ts BN250. In contrast, the mutated aminoacyl-tRNA synthetases of ts BN250 and ts BN269 were stable at 39.5 degrees C. However, the defects of these mutants released EMAPII, an inducer of apoptosis at 39.5 degrees C. No release of EMAPII occurred in ts ET12 cells at 39.5 degrees C, consistent with the delay of apoptosis in these cells.