Clinical and prognostic significance of expression of phosphoglycerate mutase family member 5 and Parkin in advanced colorectal cancer

BACKGROUND: Drugs targeting mitochondria can induce mitophagy and restrain proliferation in colorectal cancer (CRC) cells. Phosphoglycerate mutase family member 5 (PGAM5) activates serine/threonine PTEN-induced putative kinase 1/Parkin pathway-mediated mitophagy. However, there are few studies on the clinical and prognostic significance of expression of PGAM5 protein and mitophagy-related protein Parkin in patients. AIM: To assess the clinical significance of PGAM5 and Parkin proteins, as biomarkers for diagnosis and prognosis of CRC, by studying their expression in advanced CRC tissues and their association with clinicopathological parameters. METHODS: The expression of PGAM5 and Parkin in CRC tissues from 100 patients was determined by immunohistochemistry. Each case was evaluated by using a combined scoring method based on signal intensity staining (scored 0-3) and the proportion of positively stained cancer cells (scored 0-4). The final staining score was calculated as the intensity score multiplied by the proportion score. Specimens were categorized as either high or low expression according to the Youden index, and the association between the expression of PGAM5 or Parkin and clinicopathological factors was ascertained. Additionally, we employed western blot to measure PGAM5 and Parkin protein expression in six matched pairs of CRC and adjacent non-tumor tissues. RESULTS: Immunohistochemical and western blot findings showed that both PGAM5 and Parkin protein expression in tumor tissues was significantly higher than that in the adjacent tissues: PGAM5 and Parkin were mainly expressed in the cytoplasm of colonic epithelial cells. PGAM5 and Parkin protein levels were significantly positively correlated in advanced CRC tissues. Moreover, reduced Parkin protein expression was an independent prognostic factor for overall survival and progression-free survival in CRC patients as evinced by multivariate analysis. CONCLUSION: The expression of PGAM5 protein and mitophagy-related protein Parkin has diagnostic significance for CRC and may become new biomarkers. Parkin may be a potential marker for the survival of CRC patients.