Clinicopathological Significances and Prognostic Value of PPFIA4 in Colorectal Cancer

Purpose: The PPFIA gene family (PPFIA1, PPFIA2, PPFIA3, and PPFIA4) is associated with multiple human diseases, particularly malignant tumors. However, the expression and prognostic value of the PPFIA family in human colorectal cancers (CRCs) have not been reported. Materials and methods: In this study, several databases, including Oncomine, UALCAN, and the cancer cell line encyclopedia, were used to compare differences in PPFIA1, PPFIA2, PPFIA3, and PPFIA4 expression between normal colon samples and CRCs. The expression levels of these four proteins were used to evaluate the survival of patients with CRC, as determined by the Cancer Genome Atlas Program (TCGA) portal and gene expression profiling interactive analysis (GEPIA) databases. Western blotting and reverse transcription-polymerase chain reaction were performed to detect protein and mRNA levels of PPFIA1, PPFIA3, and PPFIA4, respectively. Immunohistochemical (IHC) staining was used to detect the correlation between PPFIA4 expression and the degree of CRC malignancy. Furthermore, potential miRNAs targeting PPFIA4 in CRCs were studied and confirmed. Results: Bioinformatic analysis showed that the mRNA levels of PPFIA1, PPFIA3, and PPFIA4 were higher in CRC tissue samples than in normal colon tissue. Both mRNA and protein expression of PPFIA1, PPFIA3, and PPFIA4 were increased in the CRC cell lines LoVo and Hct116 compared with the normal colon epithelial cell line. Only PPFIA4 was associated with the prognosis of patients with CRC, which was confirmed by TCGA portal and GEPIA. IHC staining confirmed that the expression of PPFIA4 was higher in CRC tissues than in normal colon tissues and also increased in poorly differentiated CRC tissues and lymph node metastatic foci in comparison with well-differentiated CRC tissues and moderately differentiated CRC tissues. Functional annotation enrichment analysis indicated that the top 100 genes co-expressed with PPFIA4 were enriched in the G-protein coupled peptide receptor activity, leukotrience B4 receptor activity, and peroxisome proliferator-activated receptors and hypoxia-inducible factor-1 signaling pathways. In addition, miR-485-5p negatively regulates the expression of PPFIA4. Conclusion: PPFIA4 expression is associated with the development of CRCs and may be a novel potential prognostic marker for human CRCs.