Comprehensive Analysis Identifies PKP3 Overexpression in Pancreatic Cancer Related to Unfavorable Prognosis

Abstract

Plakophilin 3 (PKP3) affects cell signal transduction and cell adhesion and performs a crucial function in tumorigenesis. The current investigation evaluated the predictive significance and underlying processes of PKP3 within pancreatic cancer (PC) tissues. The assessment of differences in PKP3 expression was conducted through an analysis of RNA-seq data acquired from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Additionally, clinical samples were collected to validate the findings. The predictive significance of PKP3 was investigated by analyzing survival data derived from TCGA and clinical specimens. PKP3's biological function was assessed via phenotypic experiments after the suppression of PKP3 expression within PC cells. Functional enrichment analysis, encompassing KEGG, GO, and GSEA, was employed to assess the underlying mechanism of PKP3. Immune infiltration analysis was conducted in the present investigation to determine the association between PKP3 and tumor-infiltrating immune cells (TICs). In PC tissues, PKP3 expression was abnormally upregulated and correlated with a negative prognosis in individuals with PC. PKP3 can promote the progression, migration, and invasive capacity of PC cells and is relevant to the regulation of the PI3K-Akt and MAPK signaling pathways. Immune infiltration analysis demonstrated that PKP3 impeded CD8+ T-cell infiltration and immune cytokine expression within the tumor microenvironment. The PKP3 protein was identified as a prospective independent predictive indicator and represents a viable approach for immunotherapy in the context of PC. PKP3 may impact prognosis by broadly inhibiting immune cell infiltration and promoting the activation of tumor-associated signaling pathways.

Keywords: PKP3; biomarker; immune infiltration; pancreatic cancer; prognosis.

Figure 1

Expression levels of PKP3 mRNA in PC and their association with clinical characteristics. (A) Pan-cancer analysis of PKP3 expression in 33 malignant tumor types from the TCGA database. (B–G) Comparative analysis of PKP3 expression differences between PC tissues and normal tissues based on multiple research cohorts. (H–K) Comparison of PKP3 expression levels among PC patients grouped by different clinical characteristics. PKP3, plakophilin 3; PC, pancreatic cancer; TCGA, The Cancer Genome Atlas. *, p < 0.05; **, p < 0.01; ***, p < 0.001; ns, no significance.

Figure 2

PKP3 mRNA shows a poor prognosis for PC individuals. (A–C) Kaplan–Meier survival curves of overall survival time, progression-free survival time, and disease-specific survival time; (D) univariate and multivariate Cox analysis of PKP3 mRNA and clinical features. (E,F) Nomogram model and calibration plot of PKP3 mRNA and clinical features. PKP3, plakophilin 3.

Figure 3

Validation of PKP3 expression differences at tissue and cellular levels in PC: (A) Immunohistochemical staining to determine the expression levels of PKP3 protein within PC tissues and normal pancreatic tissues; (B) univariate and multivariate Cox analysis of PKP3 protein and clinical features; (C) the Kaplan–Meier survival curve used to illustrate the prognosis of PC individuals with distinct PKP3 protein expression; (D) qRT-PCR analysis of PKP3 mRNA in the PC cell lines and normal pancreatic cell line. PKP3, plakophilin 3; PC, pancreatic cancer. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

Figure 4

PKP3 knockdown suppresses the malignant phenotype of PC cells: (A) the qRT-PCR results used to determine the efficiency of PKP3 knockout in ASPC-1 and SW1990 cell lines; (B,C) the CCK-8 assay results used to analyze the impact of PKP3 knockout on tumor cell proliferation; (D–F) the wound healing assay and transwell migration assay results used to evaluate the impact of PKP3 knockout on tumor cell migration; (G) invasion assay results used to assess the effects of PKP3 knockout on tumor cell invasion. PKP3, plakophilin 3; PC, pancreatic cancer. **, p < 0.01; ***, p < 0.001.

Figure 5

Comprehensive enrichment analysis associated with PKP3 in pancreatic cancer: (A) Gene Ontology (GO) analysis of PKP3 co-expressed genes; (B) Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis based on PKP3 co-expressed genes; (C) immune-system-relevant signaling pathways and biological mechanisms in GSEA results. PKP3, plakophilin 3.

Figure 6

PKP3 expression is related to immune cell infiltration within PC: (A) Evaluation of the various levels of TIC infiltration in the high and low PKP3 expression groups. (B) Analysis of the correlation between the expression of PKP3 and the constituents of TICs. PKP3, plakophilin 3; TICs, tumor-infiltrating immune cells. *, p < 0.05; **, p < 0.01; ***, p < 0.001; ns, no significance.

Figure 7

Association of PKP3 with immune-correlated gene groups: Association of EVL and MHC genes (A), immune activation genes (B), chemokines (C), and chemokine receptors (D). EVL, Ena-VASP-like. *, p < 0.05; **, p < 0.01; ***, p < 0.001.