Naoko Okumura

Alternative splicings on p53, BRCA1 and PTEN genes involved in breast cancer.

Alternative splicing is a major contributor to transcriptome and proteome diversity, which can lead to the deregulation of crucial cellular processes and have been associated with a variety of human diseases including cancer. As p53, BRCA1, and PTEN proteins have a key role in preventing breast cancer formation, cancer-associated splicing variants of these tumor suppressor genes are potential molecular markers and may contribute to the development of diagnostic and prognostic methods. In the present review, we summarize these tumor suppressor genes at a viewpoint of alternative splicing involved in breast cancer.

PI3K/AKT/PTEN Signaling as a Molecular Target in Leukemia Angiogenesis

PI3K/AKT/PTEN pathway is important in the regulation of angiogenesis mediated by vascular endothelial growth factor in many tumors including leukemia. The signaling pathway is activated in leukemia patients as well as leukemia cell lines together with a decrease in the expression of PTEN gene. The mechanism by which the signaling pathway regulates angiogenesis remains to be further elucidated. However, it has become an attractive target for drug therapy against leukemia, because angiogenesis is a key process in malignant cell growth. In this paper, we will focus on the roles and mechanisms of PI3K/AKT/PTEN pathway in regulating angiogenesis.

Long-term cultivation of in vitro Apis mellifera cells by gene transfer of human c-myc proto-oncogene

Establishment of cell lines representative of honeybee character would greatly assist in their analysis. Here, we show that immortalized cell line, designated as MYN9, has been generated from honeybee embryo by the gene transfer of human c-myc proto-oncogene. The morphology of the cell is characteristic of embryonic stem cell, although the cell is stable and does not spontaneously differentiate. Polymerase chain reaction analyses show that the cell is originated from authentic honeybee cell. It is proposed that the integration of human c-myc gene into honeybee precursor populations results in the establishment of stable cell line suitable for cellular and molecular studies.

Insulin receptor substrate protein 53 (IRSp53) as a binding partner of antimetastasis molecule NESH, a member of Abelson interactor protein family

Involvement of NESH in cancer invasion and metastasis is now very important and interesting. In order to clarify the molecular mechanisms, we identified insulin receptor substrate protein 53 (IRSp53) as a partner of NESH utilizing a conventional yeast two-hybrid screen with a proline-rich domain of NESH as bait. The specific interaction was confirmed by coimmunoprecipitation assay and colocalization analysis in mammalian cells. The carboxyl-terminal SH3 domain of IRSp53 is responsible for the interaction with the proline-rich domain of NESH. NESH may play a critical role in regulating the actin cytoskeleton required for membrane ruffling induced by the IRSp53 pathway. We observed that NESH expression caused a marked reduction in motility and exhibited significant reduction in tumor metastatic potential in vivo [1]. NESH expression is also frequently lost in invasive cancer cell lines despite its ubiquitous expression in normal tissues. We, however, also found that use of imatinib to treat NESH-expressed cancer cells greatly enhances its invasive tumor growth in vivo [2]. An unknown antimetastasis pathway in which NESH is involved might be regulated by abelson tyrosine kinase [3]. To identify proteins interacting with the NESH, we used a two-hybrid system to screen a human complementary DNA library with a NESH protein as bait. More than four positive preys were identified, and subsequent sequence analysis revealed one of the preys to be IRSp53.

Against Lung Cancer Cells: To Be, or Not to Be, That Is the Problem

Tobacco smoke and radioactive radon gas impose a high risk for lung cancer. The radon-derived ionizing radiation and some components of cigarette smoke induce oxidative stress by generating reactive oxygen species (ROS). Respiratory lung cells are subject to the ROS that causes DNA breaks, which subsequently bring about DNA mutagenesis and are intimately linked with carcinogenesis. The damaged cells by oxidative stress are often destroyed through the active apoptotic pathway. However, the ROS also perform critical signaling functions in stress responses, cell survival, and cell proliferation. Some molecules enhance radiation-induced tumor cell killing via the reduction in DNA repair levels. Hence the DNA repair levels may be a novel therapeutic modality in overcoming drug resistance in lung cancer. Either survival or apoptosis, which is determined by the balance between DNA damage and DNA repair levels, may lender the major problems in cancer therapy. The purpose of this paper is to take a closer look at risk factor and at therapy modulation factor in lung cancer relevant to the ROS.

Ethanol extracts of black pepper or turmeric down-regulated SIRT1 protein expression in Daudi culture cells

SIRT1 is a mammalian candidate molecule involved in longevity and diverse metabolic processes. The present study aimed to determine the effects of certain herbs and spices on SIRT1 expression. Human cell lines Daudi, Jurkat, U937 and K562 were cultured in RPMI-1640. Herb and spice powders were prepared and the supernatants were collected. RT-PCR was used to quantify the expression level of the gene. Protein samples were then analyzed by Western blotting. Western blotting revealed the down-regulation of SIRT1 protein expression in Daudi cells treated with extracts of black pepper or turmeric. On the other hand, the effect on the SIRT1 gene expression examined by reverse transcription polymerase chain reaction was unaltered. In conclusion, component(s) of certain herbs and spices may induce the down-regulation of SIRT1 protein.

Dicer Functions in Aquatic Species

Dicer is an RNase III enzyme with two catalytic subunits, which catalyzes the cleavage of double-stranded RNA to small interfering RNAs and micro-RNAs, which are mainly involved in invasive nucleic acid defense and endogenous genes regulation. Dicer is abundantly expressed in embryos, indicating the importance of the protein in early embryonic development. In addition, Dicer is thought to be involved in defense mechanism against foreign nucleic acids such as viruses. This paper will mainly focus on the recent progress of Dicer-related research and discuss potential RNA interference pathways in aquatic species.

How do you RUN on

RUN domain is present in several proteins related to the functions of Rap and Rab family GTPases. Accumulating evidence supports the hypothesis that RUN domain‐containing proteins act as a component of vesicle traffic and might be responsible for an interaction with a filamentous network linked to actin cytoskeleton or microtubules. That is to say, on one hand, RUN domains associate with Rab or Rap family proteins, on the other hand, they also might interact with motor proteins such as kinesin or myosin via intervention molecules. In this review, we summarize the background and current status of RUN domain research with an emphasis on the interaction between RUN domain and motor proteins with respect to the vesicle traffic on filamentous network.

Genistein downregulates presenilin 1 and ubiquilin 1 expression

The aim of this study was to determine the effects of several food ingredients and chemical inhibitors on the expression of presenilin, a molecule involved in γ-secretase activity and the generation of amyloid-β peptide in Alzheimers disease. Western blotting revealed the downregulation of presenilin 1 protein expression by stimulation with genistein in vitro, while the effects on presenilin 1 gene expression examined by reverse transcriptase-polymerase chain reaction (RT-PCR) were unaltered in Daudi cells. Genistein likely downregulates presenilin via the inhibition of ubiquilin 1 expression in lymphoid cells. Our findings provide new insights that may help to establish preventive strategies against Alzheimers disease.

Clobetasol synergistically diminishes Ciz1 expression with genistein in U937 cells

Cip-interacting zinc finger protein 1 (Ciz1) stimulates DNA replication and has been implicated in the tumorigenesis of breast cancer cells. In order to investigate the possibility of using medicinal glucocorticoids against breast cancer, we studied whether certain glucocorticoids affect the expression of Ciz1. The in vitro effect of clobetasol treatment on the reduction of Ciz1 expression was detected by reverse transcriptase-polymerase chain reaction. Western blotting also confirmed the down-regulation of the protein in a dose-dependent manner upon clobetasol treatment in U937 monocytoid cells. Furthermore, we found that Ciz1 protein expression was decreased after pre-treatment of the cells with clobetasol and genistein. An extract of Lens culinaris also had a synergistic effect on the repression of Ciz1 protein expression.