Expression and clinical significance of cytochrome c oxidase subunit IV in colorectal cancer patients

Introduction

Previous studies have demonstrated that the expression of cytochrome c oxidase (COX) subunits encoded by mitochondrial DNA is elevated in colorectal cancer (CRC). However, the expression of nuclear DNA-encoded COX IV and its clinical significance have not yet been investigated in CRC.

Material and methods

We examined COX IV expression in paired CRC samples (cancer and pericancerous tissues) by quantitative real-time polymerase chain reaction (qPCR), Western blot and immunohistochemical staining and analyzed its clinical significance.

Results

qPCR and Western blot analyses showed that COX IV expression was significantly elevated at both the mRNA (p = 0.05) and protein levels in CRC tissue samples when compared with those in paired pericancerous tissues. Immunohistochemistry also revealed that COX IV expression was significantly increased in CRC tissues (p < 0.001). Association analyses showed that there was no significant association between COX IV expression and clinical parameters of CRC patients except for gender (p = 0.017). Moreover, we did not find any association between COX IV expression and overall survival or recurrence-free survival of CRC patients. Further analysis showed no significant relationship between the expression of COX IV and proliferating cell nuclear antigen (PCNA), a marker of cell proliferation.

Conclusions

Our findings suggest that elevated COX IV expression may play an important role in colorectal carcinogenesis, but not in progression, which warrants further investigation in future studies.