title: Expression and clinical significance of cytochrome c oxidase subunit IV in colorectal cancer patients.
abstract: BACKGROUND
  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.
  
  
  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.
authors.affiliation: Department of Oncology, Tangdu Hospital, Fourth Military Medical University, Xi'an, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Cancer Biology and Experimental Teaching Center of Basic Medicine, Fourth Military Medical University, Xi'an, China.
authors.forename: Yibing
authors.initials: Y
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Cancer Biology and Experimental Teaching Center of Basic Medicine, Fourth Military Medical University, Xi'an, China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Cancer Biology and Experimental Teaching Center of Basic Medicine, Fourth Military Medical University, Xi'an, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Qu
authors.affiliation: Department of Biotherapy, Sun Yat-Sen University Cancer Center, Guangdong, China.
authors.forename: Qiuzhong
authors.initials: Q
authors.lastname: Pan
authors.affiliation: Department of Biotherapy, Sun Yat-Sen University Cancer Center, Guangdong, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Lü
authors.affiliation: Department of Biotherapy, Sun Yat-Sen University Cancer Center, Guangdong, China.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Cancer Biology and Experimental Teaching Center of Basic Medicine, Fourth Military Medical University, Xi'an, China.
authors.forename: Tingitng
authors.initials: T
authors.lastname: Ren
authors.affiliation: Department of Oncology, Tangdu Hospital, Fourth Military Medical University, Xi'an, China.
authors.forename: Haichuan
authors.initials: H
authors.lastname: Su
keywords: colorectal cancer; cytochrome c oxidase subunit IV; immunohistochemistry; real-time polymerase chain reaction