Parkin protein expression and its impact on survival of patients with advanced colorectal cancer

Objective: Features of colorectal cancer such as natural history, molecular, chromosomal, and epigenetic alterations have been well described. However, there is still a lack of accurate prognostic markers, which is evident by the lower overall survival rates of patients with advanced cancer. Although alterations in parkin protein expression have been described in colorectal cancer, the functional significance of this protein remains unknown. The present study aimed to investigate the involvement of parkin expression in colorectal adenocarcinoma development and progression by evaluating the association between its expression, clinicopathological parameters, and expression of known proteins involved in colorectal cancer. Methods: Tissue microarrays consisting of 73 tumor and 64 normal tissue samples were generated to examine parkin expression and localization by immunohistochemistry. Results: A positive correlation of parkin and APC expression was observed in the superficial, intermediate, and profound regions of all cases (rho = 0.37; P = 0.001). Parkin expression was also significantly associated with tumors in men (P = 0.049), those of the mucinous subtype (P = 0.028), and of advanced stage (III + IV, P = 0.041). In addition, increased parkin expression was observed in the invasive front tumor region (P = 0.013). More importantly, a positive correlation was found between parkin expression and the overall survival of patients with advanced colorectal cancer (P = 0.019). Multivariate analysis showed that parkin expression was independent of any of the clinicopathological parameters evaluated in relation to patient survival. Conclusions: These results suggest that parkin expression status can be used as a potential independent prognostic marker of survival in advanced colorectal cancer.