Gene set enrichment analysis of FNDC3B expression in patients of PC
To investigate the effect of upregulated FNDC3B expression in PC, we performed gene set enrichment analysis of FNDC3B expression in patients, with corresponding clinical information from TCGA datasets. Our results showed that the expression of FNDC3B was significantly upregulated in patients with advanced PC and distant metastasis. We also found that the mRNA level of FNDC3B was higher in patients of PC with good OS than in those with poor prognosis, whereas no significant difference in the expression of FNDC3B was observed in patients according to age, sex and lymph node metastasis. These results suggest that upregulation of FNDC3B is associated with distant metastasis of PC and predicts a poor prognosis for patients (Fig. 1).
Clinical and molecular characteristics of PC with high FNDC3B expression
We further investigated the mRNA expression of FNDC3B in patients with PC from the TCGA database, and found that the mRNA level of FNDC3B was significantly higher in the cancer cells than in corresponding noncancerous normal tissues (Fig. 2A). In grade (G stage) G2 and G3, FNDC3B mRNA levels were higher compared to G1 (Fig. 2D). In the TNM stage II, the level of FNDC3B mRNA was higher than in stage I (Fig. 2E). In patients older than 65 years, FNDC3B mRNA levels were higher than in younger patients (Fig. 2C). In the advanced tumor stage (T stage) T3, the FNDC3B mRNA level was higher than in T2 (Fig. 2F). Gender-wise, the FNDC3B mRNA level in male patients was comparable to that in female patients (Fig. 2B). These results showed a significant association of higher expression of FNDC3B with advanced age, G stage, tumor stage, and TNM stage, but not with the sex of the patient.
Upregulation of FNDC3B mRNA levels indicates poor prognosis for patients of PC
PC patients from the TCGA data set were divided into two groups, based on the median expression of FNDC3B mRNA, to investigate the prognostic role of FNDC3B in PC. We found that level of FNDC3B mRNA was higher in patients with lymph node metastasis, and poor OS, and patients who had died (Fig. 3A, 3C, 3D), whereas it was lower in patients with distant metastasis (Fig. 3B). Overall, these data suggested that upregulation of FNDC3B mRNA levels indicated poor prognosis for patients with PC. This may serve as a potential indicator of prognosis in patients with PC.
The ROC curve shows that high levels of FNDC3B mRNA is associated with PC
Using ROC curves, we analyzed whether expression levels of FNDC3B mRNA can effectively distinguish PC patients with different pathological parameters, to confirm that FNDC3B mRNA expression is related to cancer cell proliferation and poor prognosis. FNDC3B mRNA expression could be used to distinguish PC tissues from normal tissues, with an AUC of 0.9510 (95% CI: 0.9253–0.9767; P < 0.0001) (Fig. 4A). We also found a significant difference in FNDC3B expression in PC subgroups, including subgroups of G stage (G1/G2, AUC = 0.6375, P = 0.0278; G1/G3, AUC = 0.6856, P = 0.0072), TNM stage (TNM stage I/TNM stage II, AUC = 0.6599, P = 0.0205), T stage (T2/ T3, AUC = 0.6223, P = 0.0559), status (Living/dead, AUC = 0.6236, P = 0.0052) lymph node metastasis (N0/N1 + NX, AUC = 0.6259, P = 0.0112), and distant metastasis (M0/M1 + MX, AUC = 0.6392, P = 0.0017; Fig. 4B-4I). These results confirm that higher levels of FNDC3B mRNA is associated with cancer proliferation, metastasis and poor prognosis in PC.
High FNDC3B mRNA level correlates with short OS in PC patients
KM survival analysis was used to determine the correlation of level of FNDC3B mRNA with OS of the patients with PC. Patients with higher levels of FNDC3B mRNA had shorter OS than those with lower levels (Fig. 5A, P = 0.0025). Moreover, we analyzed the association between OS and FNDC3B mRNA level in various clinical subgroups of PC. As shown in Fig. 5B-5G, compared with patients with low FNDC3B expression, males (Fig. 5B, P = 0.0130), age > 65 years (Fig. 5C, P = 0.0378), age ≤ 65 years (Fig. 5D, P = 0.0060), G1 + G2 stage (Fig. 5E, P = 0.0153), stages I + II (Fig. 5F, P = 0.0015) and T3 + T4 stage (Fig. 5G, P = 0.0371) patients with high FNDC3B mRNA level exhibited a shorter OS time. All these results indicate that level of FNDC3B mRNA correlates with short OS.
GO enrichment analysis shows that FNDC3B mRNA level is associated with genes involved in regulation of cell junction, tissue migration and epithelial cell migration
To identify the molecules regulated by FNDC3B, we performed GO enrichment analysis. We found that higher level of FNDC3B mRNA was associated with regulation of cell junction, tissue migration and epithelial cell migration (Fig. 6A). Furthermore, the it was also strongly associated with HIF1A, ADAM17, CORO1C, ITGB1, LIMS1, MAP4K4, PDLIM5 and PIK3CA (Fig. 6B). These results indicate that high level of FNDC3B mRNA is associated with junction and migration of PC cells.
KEGG enrichment analysis shows that FNDC3B is associated with pathways related to signal transduction
To investigate the association between FNDC3B and signaling pathways, we performed KEGG enrichment analysis. The results showed that FNDC3B expression was positively associated with PC. We also found that FNDC3B expression was significantly enriched in four main well-studied signaling pathways in PC, including the notch, TGF-β, VEGF and Wnt signaling pathways (Fig. 7A). Moreover, the expression of genes in these four signaling pathways, including ACVR1, BMPR2, CTNNB1, ITGAV, MAPK1, NOTCH2, PIK3CA and ROCK1, was associated with the level of FNDC3B mRNA (Fig. 7B). All these data suggest that level of FNDC3B mRNA is associated with four main signaling pathways in PC.