ABSTRACT
Mitochondria (mt) play an important role in both apoptosis and haem synthesis. The present study was conducted to determine DNA mutations in mitochondrial encoded cytochrome c-oxidase I and II genes. Bone marrow (BM) biopsy and aspirate, peripheral blood (PB) and buccal smear samples were collected from 20 myelodysplastic syndrome (MDS) patients and 10 age-matched controls. Cytochrome c-oxidase I (CO I) and II (CO II) genes were amplified using polymerase chain reaction and sequenced. CO I mutations were found in 13/20 MDS patients and the CO II gene in 2/10 normal and 12/20 MDS samples, irrespective of MDS subtype. Mutations were substitutional, deletional and insertional. CO I mutations were most common at nucleotide positions 7264 (25%) and 7289 (15%), and CO II mutations were most common at nucleotide positions 7595 (40%) and 7594 (30%), suggesting the presence of potential 'hot-spots'. Mutations were not found in buccal smears of MDS patients and were significantly higher in MDS samples compared with age-matched controls in all cell fractions (P < 0.05), with bone marrow high-density fraction (BMHDF) showing a higher mutation rate than other fractions (P < 0.05). MDS marrows showed higher levels of apoptosis than normal controls (P < 0.05), and apoptosis in BMHDF was directly related to cytochrome c-oxidase I gene mutations (P < 0.05). Electron microscopy revealed apoptosis affecting all haematopoietic lineages with highly abnormal, iron-laden mitochondria. These results suggest a role for mt-DNA mutations in the excessive apoptosis and resulting cytopenias of MDS patients.
Subject(s)
DNA, Mitochondrial/genetics , Electron Transport Complex IV/genetics , Mitochondria/enzymology , Mutation , Myelodysplastic Syndromes/genetics , Adult , Aged , Aged, 80 and over , Apoptosis , Bone Marrow Cells/enzymology , Bone Marrow Cells/ultrastructure , Female , Humans , In Situ Nick-End Labeling , Male , Middle Aged , Mitochondria/ultrastructure , Myelodysplastic Syndromes/enzymology , Myelodysplastic Syndromes/pathologyABSTRACT
Although dexamethasone is very effective for controlling peritumoral cerebral edema, it is associated with distressing side effects that decrease the quality of life for many patients. One potential mechanism to explain the ability of dexamethasone to repair blood-brain barrier dysfunction is through the inhibition of cyclooxygenase-2 (COX-2). The purpose of this study was to determine in a rat brain tumor model whether SC-236, a selective COX-2 inhibitor, is as effective as dexamethasone. Twenty-nine adult male Fischer 344 rats were implanted with intracerebral 9L gliosarcomas and divided into 3 treatment groups. One group (n = 9) served as controls, another (n = 9) was treated with dexamethasone (3 mg/kg p.o. daily), and a third group (n = 11) received SC-236 (3 mg/kg p.o. daily). A survival study was performed. The median survival in the control group was 16 days, compared with 23 days for the dexamethasone group and 23 days for the COX-2 inhibitor group. Kaplan-Meier analysis on pairwise group comparisons showed improved survival that was statistically significant for each treatment group compared with the control group (log-rank test P = 0.009 for dexamethasone to control and P = 0.005 for COX-2 to control), and no significant difference in survival for the COX-2 compared with dexamethasone (log-rank test P = 0.2). These results suggest that a selective COX-2 inhibitor appears to be as effective as dexamethasone in prolonging survival in a rat brain tumor model.
