Increased SPHK1 and HAS2 Expressions Correlate to Poor Prognosis in Pancreatic Cancer

Abstract

Objective: SPHK1 and HAS2 have been reported to play important roles in tumorigenesis and development. However, their expression and prognostic value in pancreatic cancer (PC) remain unclear. This study is aimed at investigating the expression of SPHK1 and HAS2 on the prognosis of pancreatic cancer.

Materials and methods: The expression of SPHK1 and HAS2 in pancreatic cancer tissues was analyzed through TCGA and GTEx databases and validated by qRT-PCR and Western blot in pancreatic cancer cell lines. χ ² test was used to explore the correlation of the SPHK1 and HAS2 expressions with clinical characteristics. Kaplan-Meier survival analysis and ROC curve were used to evaluate the prognostic and diagnostic roles of SPHK1 and HAS2 in pancreatic cancer. Additionally, Spearman correlation analysis was applied to assess the correlation between the SPHK1 and HAS2 in pancreatic cancer. GO analysis and KEGG analysis were applied to explore the possible signaling pathway that SPHK1 and HAS2 coregulated genes mediated.

Results: The expression of SPHK1 and HAS2 was markedly upregulated in pancreatic cancer tissue and cell lines, respectively. Furthermore, there was a significant positive correlation between SPHK1 and HAS2 expressions. ROC curves showed that SPHK1 combine with HAS2 has good diagnostic value in pancreatic cancer patients with 85% sensitivity and 99.4% specificity. Kaplan-Meier analysis showed that increased expression of SPHK1 and HAS2 was significantly associated with short overall survival (OS) of pancreatic cancer patients. GO and KEGG results revealed that SPHK1 and HAS2 mainly involved cell proliferation and invasion mediated by extracellular matrix- (ECM-) receptor interaction, focal adhesion, and PI3K-AKT signaling pathways.

Conclusions: Overexpression of SPHK1 and HAS2 could be important markers for the prognosis of pancreatic cancer.

Figure 1

SPHK1 and HAS2 are upregulated in pancreatic cancer. (a) Relative SPHK1 and HAS2 mRNA expressions in pancreatic cancer patient tissues versus normal samples from TCGA and GTEx databases. (b) Immunohistochemical staining of SPHK1 in normal pancreatic and pancreatic cancer tissues on the Human Protein Atlas database. The “weak,” “moderate,” and “strong” correspond to the low, medium, and high of the intensity of immunohistochemical staining; ^∗P < 0.05.

Figure 2

Overexpression of SPHK1 and HAS2 in pancreatic cell lines. (a) qRT-PCR was used to detect the expression of SPHK1 and HAS2 mRNA expressions in pancreatic cell lines (Capan-1, AsPC-1, and PANC-1) and normal pancreatic duct epithelial HDPE6C7 cell line. (b) Western blot analysis of SPHK1 and HAS2 expressions in pancreatic cancer and cell lines (AsPC-1, Capan-1, and PANC-1) and normal pancreatic duct epithelial HDPE6C7 cells. ^∗∗P < 0.01 and ^∗P < 0.05.

Figure 3

The positive correlation and diagnostic ROC curves of SPHK1 and HAS2 in pancreatic cancer. (a) Correlation between SPHK1 and HAS2 expressions in pancreatic cancer tissues analyzed by TCGA and GTEx databases. (b) Diagnostic ROC curves of SPHK1, HAS2, and SPHK1 combine with HAS2 in distinguishing pancreatic cancer and normal people in a TCGA cohort.

Figure 4

The prognostic significance of SPHK1 and HAS2 in pancreatic cancer patients. (a) Kaplan-Meier curves showing the OS of pancreatic cancer patients with high and low SPHK1 expression. (b) Kaplan-Meier curves showing the OS of pancreatic cancer patients with high and low HAS2 expression. ^∗P < 0.05.

Figure 5

GO term and KEGG analysis of the coregulated genes. (a) 38 genes were coregulated by SPHK1 and HAS2. (b) GO term enrichment. Y-axis shows the GO terms of biological process. The length of the bars is proportional to the number of genes. (c) KEGG enrichment. The size of the nodes is proportional to the number of genes. GO: Gene Ontology; KEGG: Kyoto Encyclopedia of Genes and Genomes.