Regulation of tumour cell fatty acid oxidation by n-6 polyunsaturated fatty acids.
Colquhoun A. de Mello FE. Curi R.
Departamento de Histologia e Embriologia, Universidade de Sao Paulo, Brasil.
Fatty acids have been shown to regulate the expression of mRNA for both lipogenic and glycolytic enzymes in rat liver. The role of fatty acids in the regulation of carnitine palmitoyltransferase (CPT) I and II activity in tumour cells was investigated. The polyunsaturated fatty acids, gamma-linolenic and arachidonic acid, caused 60-70% inhibition of tumour cell CPT I activity and 45-50% inhibition of [14C]-palmitic acid oxidation to 14CO2. These effects were blocked by the cyclooxygenase inhibitor, indomethacin. Prostaglandins E1 and E2 caused marked inhibition of both CPT I and CPT II activity and inhibition of cell proliferation. Prostaglandin E2 production by tumour cells was increased in the presence of arachidonic acid and inhibited when indomethacin was present. The proliferation of the HT29 cell line was unaffected as was its CPT I and II activity by both fatty acids and prostaglandins. CPT I mRNA expression was not inhibited by fatty acids, indeed it increased-in the presence of arachidonic acid and prostaglandin E1. These results strongly suggest that polyunsaturated n-6 fatty acids are able, via prostaglandin products, to regulate the CPT activity of certain tumour cells. This may have a considerable impact on mitochondrial beta-oxidation and cellular metabolism of fatty acids, reflected in the marked inhibition of cell proliferation by these fatty acids.
Down-regulation of protein kinase C-alpha detected in human colorectal cancer.
Suga K. Sugimoto I. Ito H. Hashimoto E.
Department of Pathological Biochemistry, School of Life Sciences, Faculty of Medicine, Tottori University, Yonago, Japan.
The down-regulation of protein kinase C (PKC) was examined by Western blot procedure on about 30 tissue samples derived from human colorectal cancer and the corresponding normal mucosa. PKC-alpha down-regulation was detected in 60% of the cancer tissues compared with the respective normal mucosa and was observed in a higher frequency with the tissues under more advanced cancer stages. However, the frequencies of the down-regulation of PKC-delta and PKC-zeta were lower than that of PKC-alpha. These results suggest that a decreased level of PKC-alpha may affect the cell growth and tumor promotion in colorectal tissue.
Vaccinia virus-induced changes in cytokine-regulated acute phase plasma protein synthesis by hepatoma cells.
Rokita H. Branicki W. Wronska D. Borysiewicz LK. Koj A.
Institute of Molecular Biology, Jagiellonian University, Krakow, Poland. email@example.com
Human hepatoma cell line, HepG2, has been infected with vaccinia virus and synthesis of plasma proteins was determined by electroimmunoassay and corresponding mRNA's measured by Northern blotting. The inhibitory effect of the virus was dose- and time-dependent. Electrophoretic mobility shift assay revealed a decrease in C/EBP binding activities in nuclear extracts isolated from the infected hepatoma cells. Supershift analysis of the C/EBP isoforms showed alpha and beta subunit involvement in DNA binding. The treatment of the cells with interleukin-1, interleukin-6, and dexamethasone at the initial stage of infection appears to delay the virally induced inhibition of host cell protein synthesis. Thus, possible "protective" role of the acute phase cytokines in viral infection is proposed.
Variations in gene expression and genomic stability of human hepatoma cells integrated with hepatitis B virus DNA.
Kuo KW. Yang PY. Huang YS. Shieh DZ.
Department of Biochemistry, Kaohsiung Medical College, Taiwan.
The association of hepatitis B virus (HBV) infection with human hepatoma is well established. However, no consensus regarding the etiology of hepatocellular carcinoma was elucidated. In this paper, the genomic stability and gene expression of HBV DNA-integrated and non-integrated hepatoma cells by Transcript Profile (TP)-PCR and RT-PCR are characterized. The additional DNA bands generated from TP-PCR of HBV integrated genomes were not correlated with the sequence of HBV, suggesting that the variations may result from genomic instability of the host cells. Moreover, differential genes expressed in HBV DNA-integrated cells were sequenced. A cDNA generated from the integrated cells exhibited 99.3% homology with the sequences of ATP synthase 6 and cytochrome C oxidase III, but the sequences were abnormally linked together. Since HBV infection may alter the energy metabolism of the cell, the results suggest that the integration may cause mitochondriae defects in the ATP synthase 6 and cytochrome C oxidase III genes.
Effect on colon cancer cells of human interferon-beta gene entrapped in cationic multilamellar liposomes.
Shimizu M. Akiyama S. Ito K. Kasai Y. Takagi H. Kito M. Ohishi N. Yagi K.
Department of Surgery, Nagoya University School of Medicine, Japan.
When cultured cells of human colon cancer cell line SW480 were transfected with human interferon-beta (hIFN-beta) gene by means of cationic multilamellar liposomes, the endogenously produced hIFN-beta exhibited a remarkable anti-proliferative effect on the cells, which was more effective than that of exogenously added hIFN-beta. This effect lasted for several days, and was blocked completely by the addition of sufficient amounts of anti-hIFN-beta antibody. From experiments using a transwell plate and an infusion pump, we found that endogenously produced hIFN-beta acted effectively on the cells around the transfectants and that the growth-inhibitory effect was totally retained upon continuous dilution of the medium. These data indicate that hIFN-beta expressed endogenously by transfer of its gene acted on these cancer cells mainly in a paracrine manner. Although the transfection with hIFN-gamma gene also revealed a definite growth-inhibitory effect on the same tumor cells, the extent was less than that of hIFN-beta gene.