Isotype-Specific Inhibition of Histone Deacetylases: Identification of Optimal Targets for Radiosensitization / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: Histone deacetylase (HDAC) inhibitors radiosensitize tumor cells. To elucidate mechanisms underlying radiosensitization by HDAC inhibition, understanding of differential contributions of HDAC isotypes is needed. The aim of this study was to investigate involvement of known HDAC isotypes in modulation of cellular radiosensitivity. MATERIALS AND METHODS: Because pharmacologic HDAC inhibitors lack isotype-specificity, RNA interference against 11 HDAC isotypes was used to inhibit HDAC in an isotype-specific manner. Radiation cell survival was evaluated using a clonogenic assay in SQ20B cells transfected with small interfering RNA specifically targeting HDAC isotypes. Immunocytochemistry was performed for detection of γH2AX foci. Protein expression was measured using Western blotting. RESULTS: Among 11 HDAC isotypes tested, specific inhibition of 7 isotypes (HDAC1, HDAC3, HDAC4, HDAC6, HDAC7, HDAC10, and HDAC11) enhanced radiation lethality in SQ20B cells. Radiosensitization by inhibition of these HDAC isotypes was accompanied by delay of DNA double strand break repair. Radiosensitivity of SQ20B cells was not altered by selective inhibition of the remaining four isotypes (HDAC2, HDAC5, HDAC8, and HDAC9). Inhibition of HDAC isotypes resulted in downregulation of various proteins involved in pro-survival and DNA damage repair pathways. CONCLUSION: Isotype-specificity exists in HDAC inhibition-induced radiosensitization. Different HDAC isotypes are differentially involved in modulation of cellular radiosensitivity.

The Effect of Chemoradiotherapy with SRC Tyrosine Kinase Inhibitor, PP2 and Temozolomide on Malignant Glioma Cells In Vitro and In Vivo / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: We investigated the effect of chemoradiotherapy with PP2 and temozolomide (TMZ) on malignant glioma cells using clonogenic assays and in vivo brain tumor model. MATERIALS AND METHODS: The effect of PP2 on radiosensitivity of U251 and T98G cells was investigated using clonogenic assays. The expression of E-cadherin, matrix metalloproteinases 2 (MMP2), Ephrin type-A receptor 2 (EphA2), and vascular endothelial growth factor (VEGF) was measured by Western blotting and an accumulation of γH2AX foci 6 hours after radiotherapy was measured after PP2 treatment. The effect of PP2 on migration, invasion, and vasculogenic mimicry formation (VMF) of U251 cells was evaluated. In an orthotopical brain tumor model with U251 cells, PP2 was injected intraperitoneally with or without oral TMZ before, during and after whole brain radiotherapy. Bioluminescence images were taken to visualize in vivo tumors and immunohistochemical staining of VEGF, CD31, EphA2, and hypoxia-inducible factor 1a was performed. RESULTS: PP2 increased radiosensitivity of U251 and T98G cells without decreasing survival of normal human astrocytes. Chemoradiotherapy with PP2 and TMZ resulted in increased accumulation of γH2AX foci. PP2 induced overexpression of E-cadherin and suppression of MMP2, VEGF, and EphA2. PP2 also compromised invasion, migration, and VMF of U251 cells. In brain tumors, chemoradiotherapy with PP2 and TMZ decreased tumor volume best, but not statistically significantly compared with chemoradiotherapy with TMZ. The expression of VEGF and CD31 was suppressed in PP2-treated tumors. CONCLUSION: PP2 enhances radiosensitivity of malignant glioma cells and suppresses invasion and migration of U251 cells. Chemoradiotherapy with PP2 and TMZ resulted in non-significant tumor volume decrease.

Bisphenol A Impairs Mitochondrial Function in the Liver at Doses below the No Observed Adverse Effect Level

Bisphenol A (BPA) has been reported to possess hepatic toxicity. We investigated the hypothesis that BPA, below the no observed adverse effect level (NOAEL), can induce hepatic damage and mitochondrial dysfunction by increasing oxidative stress in the liver. Two doses of BPA, 0.05 and 1.2 mg/kg body weight/day, were administered intraperitoneally for 5 days to mice. Both treatments impaired the structure of the hepatic mitochondria, although oxygen consumption rate and expression of the respiratory complex decreased only at the higher dose. The hepatic levels of malondialdehyde (MDA), a naturally occurring product of lipid peroxidation, increased, while the expression of glutathione peroxidase 3 (GPx3) decreased, after BPA treatment. The expression levels of proinflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) also increased. In HepG2 cells, 10 or 100 nM of BPA also decreased the oxygen consumption rate, ATP production, and the mitochondrial membrane potential. In conclusion, doses of BPA below the NOAEL induce mitochondrial dysfunction in the liver, and this is associated with an increase in oxidative stress and inflammation.

Alteration of Antioxidant Enzyme Gene Expression with Aging and Exercise in Fisher Rats

BACKGROUND: It has been reported that radical oxygen species(ROS) production increased drastically during ageing. This increase in ROS had negative effects on many age-related diseases. In this study, we investigated the effects of ageing and exercise on antioxidant gene expression in Fisher rats and the mechanism of chronic exercise on ROS generation related to ageing. METHODS: After a standard diet, young and old male Fischer rats were assigned to sedentary control groups(young control group: YC, old control group: OC) and exercise training groups(young exercised group: YE, old exercised group: OE). After a 12-week treadmill exercise training in the exercise training groups, antioxidant gene expre- ssion(catalase, glutathione peroxidase) in the liver and muscle was measured by RT-PCR(reverse transcription- polymerase chain reaction). RESULTS: Liver catalase mRNA expression was lower in the old group compared with that in the young group. However, this remained unchanged post-exercise. Liver glutathione peroxidase mRNA expression was not different between the young and old groups and remained unchanged in both these groups. The expression of catalase mRNA in the soleus muscle was significantly lower in the old control rats compared with that in the young rats. Exercise sig- nificantly increased catalase mRNA expression in the soleus in both the young and old rats. The expression of gluta- thione peroxidase mRNA in the soleus was lower in the old control rats than in the young. Exercise significantly increased glutathione peroxidase mRNA expression in both young and old rats. CONCLUSION: This study showed that chronic exercise could be an important contributor to the recovery in the decline of certain antioxidant gene expressions in both young and aged rats. Long-term exercise may posi- tively affect metabolic diseases by modulating antioxidant gene expression.