Overexpression of Apolipoprotein C1 (APOC1) in Clear Cell Renal Cell Carcinoma and Its Prognostic Significance

Abstract

BACKGROUND The aims of this study included 3 aspects: 1) assessing the expression of Apolipoprotein C1 (APOC1) in clear cell renal cell carcinoma (ccRCC) and normal groups; 2) evaluating the prognostic significance of APOC1 expression in the overall survival (OS) of ccRCC patients; and 3) exploring APOC1-related signaling pathways. MATERIAL AND METHODS The APOC1 expression value and clinical data of ccRCC patients were obtained from the cBioPortal database. We then evaluated the association of APOC1 expression with clinical characteristics of ccRCC patients. We also assessed the correlation between APOC1 expression and clinical outcome using Kaplan-Meier method. Our work then verified the independent prognostic factors of ccRCC by Cox regression analysis. Finally, the potential role of genes co-expressed with APOC1 was revealed via functional enrichment analysis. RESULTS Bioinformatic data revealed that APOC1 was expressed at higher levels in ccRCC tissue than in the normal group (all P<0.05). The high expression of APOC1 was associated with unfavorable prognosis of female patients (P<0.01), but not of male patients. APOC1 high expression also shortened the survival time of ccRCC patients age ≥60 years old (P<0.05). Cox regression analysis further indicated that APOC1 expression was an independent prognostic factor for OS of ccRCC patients. Additionally, we found that APOC1 expression was significantly associated with sex, grade, clinical stage, and T stage. Finally, enrichment analysis suggested that APOC1-associated pathways were involved in tumor growth and metastasis. CONCLUSIONS The current study indicated that APOC1 was highly expressed in ccRCC and was significantly associated with key clinical features. APOC1 appears to be an independent prognostic factor in patients with ccRCC. Importantly, APOC1 might be a potential therapeutic target for ccRCC via regulating pathways involved in cell growth and metastasis.

Figure 1

Expression of APOC1 in human cancers. (A) Disease summary for APOC1. red: high expression, blue: low expression. The threshold was set as follows: P value: 0.05, fold change: 2, gene rank: 10%, (B) Comparison of APOC1 across 6 analyses regarding ccRCC via meta-analysis. All data were derived from the Oncomine database based on TCGA data.

Figure 2

(A–F) The differential analyses of APOC1 expression in different datasets. All data were derived from the Oncomine database based on TCGA data.

Figure 3

APOC1 expression and prognosis analyses in kidney renal clear cell carcinoma. (A) Representative immunohistochemistry images and detailed information on APOC1 in kidney cancer and normal tissues that were obtained from the HPA database; (B) Tumor/normal differential expression analysis in Gepia; (C) Patient survival analysis in Gepia.

Figure 4

Survival analyses based on clinical characteristics of ccRCC patients. (A) Sex; (B) Age; (C) Clinical stage; (D) Histological grade.

Figure 5

ROC analysis for predicting prognosis. (A) Overall survival (OS); (B) Disease-free survival (DFS).

Figure 6

APOC1 expression analyses based on clinicopathological factors. (A) Sex; (B) Primary tumor laterality; (C) Age; (D) Histological grade; (E) T stage; (F) Clinical stage. Compared with normal group: ** P<0.01 and *** P<0.001.

Figure 7

The expression of co-expressed genes with APOC1 in various cells.

Figure 8

GO annotation and KEGG pathway analyses. (A) Molecular function (MF); (B) Biological process (BP); (C) Cellular component (CC); (D) Biological pathways.