Hypermethylation of the RUNX3 gene in hepatocellular carcinoma

Methylation events play a critical role in various cellular processes including regulation of gene transcription and proliferation. Recently, RUNX3 gene, one of TGF-beta-Smads signaling transduction pathway genes, showed strong tumor-suppressor activity by regulation of epithelial proliferation and apoptosis. To elucidate the potential etiological role of the RUNX3 gene in the development of hepatocellular carcinoma (HCC), we have analyzed the methylation status of 5' CpG island of the RUNX3 gene in a series of 73 HCC tissues and 11 liver cell lines. Expectedly, promoter methylation of RUNX3 gene was found in 2 (2.7%) of 73 corresponding normal liver, whereas 30 (41.1%) of 73 HCCs and 4 (40%) of 10 liver cancer cell lines showed hypermethylation of the gene, respectively. There was no significant difference between promoter hypermethylaion and clinicopathologic parameters of primary HCC samples, including histologic grade, microvascular invasion, and clinical stage. Interestingly, demethylating agent 5-aza-2-deoxycytidine induced reactivation and more potent expression of RUNX3 gene in HCC cell lines. Our findings indicate that promoter hypermethylation of RUNX3 gene may occur as an early event in the development of HCC and that methylation may be a major mechanism for inactivation of RUNX3 gene in HCC.

Regulation of bcl-2 family in hydrogen peroxide-induced apoptosis in human leukemia HL-60 cells

Numerous types of cells have been shown to undergo apoptosis when exposed to oxidant agent such as hydrogen peroxide. In order to understand the functional relationship between the anti- and pro-apoptotic regulatory proteins in the cells under oxidant stress, we have studied the level of expression of apoptosis regulatory proteins, bcl-2 and bax, in human leukemia HL-60 cells. The exposure of HL-60 cells to different concentrations of H2O2 for 6 h resulted in a typical apoptosis of the cells as characterized by flow cytometry, cell cycle analysis, and DNA fragmantation. There was a block in G1 to S transition and apoptotic cells were mainly derived from S and G2 cells. Kinetic study demonstrated that the levels of both bcl-2-mRNA and -protein expression were decreased with the progression of cellular apoptosis whereas the level of bax-mRNA was unchanged but the expressed bax-protein was not detectable. Cycloheximide, a nonspecific translation inhibitor, did not prevent the hydrogen peroxide-mediated apoptosis in HL-60 cells. These results suggest that the regulation of bcl-2, but not of bax are important factor in the oxidative stress-induced apoptosis in HL-60 cells.

Optimization of tumour radiotherapy: Part V--Radiosensitization by 2-deoxy-D-glucose and DNA ligand Hoechst-33342 in a murine tumour.

Radiosensitizing effects of combination of a minor groove DNA ligand, Hoechst-33342, with the glucose analogue and inhibitor of glycolysis, 2-deoxy-D-glucose (2-DG) have been investigated in Ehrlich ascites tumour (EAT) bearing mice following focal irradiation of the tumour with 60Co gamma-rays. Treatment-induced tumour growth delay and tumour free animal survival were evaluated as parameters of radiation response. Focal irradiation of the tumour with a single fraction of 10 Gy induced a moderate delay in tumour growth but did not lead to complete regression in any of the tumours. Intravenous administration of H-342 1 hr before irradiation enhanced radiation-induced growth delay in a dose dependent manner. Complete regression of the tumour was observed only at a dose of 10 mg/kg body wt, leading to a cure (tumour free survival for more than 100 days) rate of 55%. Administration of 2-DG (2 g/kg body wt; i.v.), immediately before irradiation significantly enhanced radiation-induced growth delay and resulted in a cure rate of 45%. In combination with this dose of 2-DG (2 g/kg body wt), H-342 at a lower dose (5 mg/kg body wt) significantly enhanced the cure rate to 66%. H-342 or 2-DG given alone or in combination at the doses investigated here did not show any significant effects on the unirradiated tumour.

Study of genotoxic effects of antidiarrheal medicinal herbs on human cells in vitro.

The use of medicinal herbs has been a common practice in Asia but their genotoxic properties are little known. In the present study, genotoxic effects of three antidiarrheal herbs, guava leaf, mangosteen peel and pomegranate peel, were examined using established human cell lines, Raji and P3HR-1. Cells were treated with boiled-water extract of the herbs at various concentrations for 24 and 48 hours in vitro. Cell growth and viability were dose dependently reduced. No apparent chromosomal aberrations were induced by the treatment. Administration of pomegranate extract induced apoptotic DNA fragmentation. This genotoxicity test system is simple and convenient for the primary screening.

Potentiation of radiation effects in plateau phase human glioma cells by combination of metabolic inhibitors.

Effects of glycolytic inhibitor 2-deoxy-D-glucose (2-DG) on radiation damage were studied in a human glioma cell line (BMG-1), grown to confluence in monolayer. After irradiation (60Co-gamma-rays, 2 Gy) and incubation with low concentrations of 2-DG (0.5, 1.25 mM; 2-DG/glucose = 0.1, 0.25; 2 hr), in the absence or presence of respiratory inhibitor KCN (0.5-2 mM), cells were trypsinized and plated to assay radiation induced cytogenetic damage (micronuclei formation). The observations made were: (1) 2-DG and/or KCN treatments did not induce damage in unirradiated cells. (2) Either of these treatments did not increase radiation induced micronuclei formation. (3) Presence of 2-DG along with KCN (1,2 mM) significantly enhanced the radiation induced micronuclei formation. (4) Preliminary experiments by macrocolony assay showed that radiation induced cell death was also significantly increased by the combined treatment. These observations suggest that presence of clinically feasible, low concentrations of 2-DG (2-DG/glucose < 0.5) for short intervals of time after radiation could increase radiation damage in non-cycling, hypoxic tumour cells with impaired oxidative and increased glycolytic energy metabolism.

Chemical radiosensitization by misonidazole: production and repair of DNA single-strand breaks in Yoshida ascites tumor cells.

Formation of strand-breaks in DNA and its repair in Yoshida ascites tumor cells exposed to gamma radiation (100-400 Gy) in presence and absence of misonidazole (10 mM) were studied. The methodology involved pre-labelling of cellular DNA by 3H-thymidine during cell proliferation in rats, irradiation of cells in vitro and analysing sedimentation profile of DNA by ultracentrifugation in alkaline sucrose density gradients. Irradiation under euoxic conditions resulted in formation of about 1.5 times greater number of strand breaks as compared to those formed during irradiation under hypoxic conditions. Misonidazole (10 mM) by its presence along with the cells during irradiation under hypoxic conditions caused a 3-fold increase in the number of single strand breaks, but under euoxic conditions of irradiation the presence of misonidazole did not enhance the strand break formation. Incubation of cells irradiated in absence of misonidazole for 1 hr in tissue culture medium at 37 degrees C resulted in repair of substantial fraction of the strand breaks while there was no repair of the DNA strand breaks in cells irradiated in the presence of the chemical.

Estabelecimento de um método "in vitro" de controle biológico de agentes antineoplásicos em uso no Instituto Nacional de Câncer

O objetivo do presente trabalho foi desenvolver um método capaz de verificar a eficácia, a nível biológico, das drogas antineoplásicas, que näo necessitem de metabolismo prévio para sua açäo e que atualmente estäo sendo usadas no Instituto Nacional de Câncer (INCa). O princípio de ensaio foi baseado na medida de inibiçäo da proliferaçäo celular da linhagem K562 e de células ativadas por fitohemaglutinina (PHA), usando-se como marcador a incorporaçäo no DNA de timidina tritiada. Conclui-se que esse ensaio näo é adequado para testar a atividade antitumoral do Methotrexate, mas pode ser extremamente sensível para os estudos com derivados da Vinca