Biomedical subjects

M Kikukawa

Publications and source records attributed to M Kikukawa.

40 records · Page 3Linked to original sources

PubMedDate not supplied

Effect of dibutyryl cyclic AMP on the cyclin-dependent kinase inhibitor p27Kip1 in the human hepatoma cells PLC/PRF/5.

The cyclin-dependent kinase (cdk) inhibitor p27Kip1 is known to play a role in cell-cycle regulation at G1 and G1/S phase. We investigated the effect of the putative growth-inhibiting agent dibutyryl cyclic AMP (DBcAMP) on the serial changes of p27Kip1 expression in the human hepatoma cells PLC/PRF/5 in culture. The p27Kip1 protein level increased at an early stage of G1 phase (2 hours) after a release from serum-starvation and subsequently maintained the level until the entry to S phase, whereas an addition of DBcAMP at 1mM increased the p27Kip1 protein level during G1 phase. In contrast, the relative expression levels of p27Kip1 mRNA at 2 hours, 4 hours and 6 hours were lower in DBcAMP-added cells. The effects of DBcAMP on cell growth were, reduction of S-phase cells, inhibition of DNA synthesis, and accumulation of G2-phase cells. In the presence of the antisense oligodeoxynucleotides against p27Kip1 mRNA, DBcAMP-induced growth inhibition was partially abolished. These findings suggest that DBcAMP elevates p27Kip1 protein expression during G1 phase, which could be associated with growth inhibition. DBcAMP may inhibit the degradation of p27Kip1 protein.

Bucladesine↗

PubMedDate not supplied

Inhibitory effects of human sera on adenovirus-mediated gene transfer into rat liver.

Recent advances in molecular biology have made gene therapy for cancer feasible in clinical trials. Although recombinant adenovirus is an attractive vehicle for transferring therapeutic genes in vivo, animal studies have indicated that the clinical usefulness of adenovirus vectors may be limited by their immunogenicity. It has been shown that neutralizing antibodies against adenoviruses reduce the efficiency of vector readministration. It is of great importance to examine the effects of human sera on adenovirus-mediated gene transfer, because the majority of prospective gene therapy patients are likely to have been exposed to wild-type adenoviruses. In the present study, it was shown that anti-adenovirus antibody-positive human sera with the lowest positive titer substantially inhibit the adenovirus-mediated gene transfer not only in vitro but also in vivo. These results may have important implications for efficacy considerations when adenovirus vectors are employed in the clinical setting.

3T3 Cells↗

PubMedDate not supplied

Bystander effect caused by cytosine deaminase gene and 5-fluorocytosine in vitro is substantially mediated by generated 5-fluorouracil.

Because it appears impossible to transfer toxic genes to all the cells of a cancer, the bystander effect is critical to induce effective antitumor effects. In the present study, possible in vitro mechanisms of the bystander effect by the cytosine deaminase (CD) gene and 5-fluorocytosine (5-FC) were investigated. CD-transduced cancer cells exhibited much higher sensitivity to 5-FC compared to parental cells. CD-transduced cells caused killing of neighboring parental cells in the presence of 5-FC, irrespective of direct cell-to-cell contact. Media conditioned by CD-transduced cells and 5-FC contained considerable amounts of 5-fluorouracil (5-FU) and exhibited profound cytotoxicity on parental cells. Furthermore, this killing ability of conditioned media correlated well with 5-FU levels converted from 5-FC by CD-transduced cells. CD was shown not to be secreted into media from cells. These results indicate that diffusible 5-FU plays the substantially causative role in the in vitro bystander effect caused by the CD/5-FC system.

Animals↗

PubMedDate not supplied

Analysis of intrahepatic invasion of hepatocellular carcinoma using fluorescent dye-labeled cells in mice.

Despite intensive efforts in the treatment of hepatocellular carcinoma (HCC), its prognosis remains poor, mainly because of intrahepatic metastasis. It is, therefore, important to investigate the invasive and metastatic behavior of HCC. To examine this, murine HCC cells were labeled with the fluorescent carbocyanine dye, DiI and implanted under the capsule of the liver of syngeneic mice. Optimal conditions are described for labeling HCC cells with DiI. Histological analysis using fluorescent and confocal microscopes revealed that HCC cells migrate to and invade the adjacent portal vein, but not the adjacent central vein. Conversely, DiI-labeled hepatocytes were shown not to migrate in the liver. These results suggest that intrahepatic metastasis of HCC occurs by invading the portal venous system. Furthermore, it is indicated that orthotopic implantation of fluorescent dye-labeled tumor cells may be a convenient and useful method to investigate the invasive and metastatic behavior of various types of cancer.

Animals↗