Mitochondrial DNA content reduction induces aerobic glycolysis and reversible resistance to drug-induced apoptosis in SW480 colorectal cancer cells.

Mutations and reductions in mitochondrial DNA (mtDNA), which are frequent in human tumors, may contribute to enhancing their malignant phenotypes. However, the effects of mtDNA abnormalities in colorectal cancer remain largely unknown. In this study, mtDNA-reduced cell model was established by partial depletion of mtDNA in SW480 cells and the effects of mtDNA reduction in colorectal cancer cells were investigated. We found that mtDNA-reduced cells had enhanced glucose uptake and generated markedly higher level of lactate. These changes were accompanied by only a slight reduction in ATP production compared with the parent cells. Furthermore, the activity of the glycolytic enzymes, hexokinase (HK) and phosphofructokinase (PFK), was increased in mtDNA-reduced cells. These results suggested a switch to aerobic glycolysis in mtDNA-reduced cells, which helped the cells to gain a survival advantage. Notably, when mtDNA content was restored, metabolism returned to normal. In addition, the mtDNA-reduced cells were highly resistant to 5-fluorouracil- and oxaliplatin-induced apoptosis and this drug resistance was reversible following recovery of the mtDNA content. We also found that the Akt/mTOR pathway was activated in the mtDNA-reduced cells. This pathway might play a significant role in drug resistance in the mtDNA-reduced cells as drug susceptibility was restored when this pathway was inhibited. Taken together, our results supported the notion that mtDNA reduction induced aerobic glycolysis and a reversible apoptosis-resistant phenotype in SW480 cells, and that the Akt/mTOR pathway might be involved in the drugs-induced apoptosis resistance.

[Value of five-repetition sit-to-stand test in clinical evaluation of chronic obstructive pulmonary disease].

OBJECTIVE: To investigate the value of five-repetition sit-to-stand test (5STS) in clinical evaluation of elderly patients with chronic obstructive pulmonary disease (COPD). METHODS: Fifty-one patients with COPD and 20 healthy individuals were enrolled in this study. All the participants underwent 5STS, pulmonary function examination, and 6 min walking test (6MWT) and were evaluated for severity of dyspnea (by mMRC) and BODE index during the tests. RESULTS: All the participants completed 5STS test with a good reproducibility of the time used for 3 sessions of the test (P<0.001). The mean time used by COPD patients for 5STS was significantly longer than that by healthy individuals (12.93±3.11s vs 0.72±0.71 s, P=0.002). The results of 5STS showed a significant negative correlation with those of 6MWT in the case group and control group with correlation coefficients of -0.611 and -0.682, respectively. The results of 5STS were negatively correlated with FEV1%Pre and body mass index (P<0.05) but positively with mMRC and BODE index in COPD patients (P<0.05). CONCLUSION: 5STS is a simple and reproducible test to evaluate the patients' exercise capacity and the severity of COPD, and is well correlated with the current methods for clinical evaluation of COPD.