DEGs in APA samples compared with control AAG samples
As large amounts of data were included in the gene expression profiles, the original data were analyzed and filtered. A total of 182 upregulated and 88 downregulated DEGs were identified by GEO2R analysis. The intersection DEGs of the three datasets consisted of 6 genes, PCP4, ATP2A3, PPP4R4, CTNND2, CYP11B2 and CLRN1. More genes including IL17D, EDA2R, RAB3C, SCRN1, CLCN5, MTMR4, ABCB4, HTR4, QPCT, GBP2, NETO2, VDR, CBR1, ADAM23, FAM19A4 and AQP2 were covered in any two of these datasets. The Venn graph showed the intersection DEGs was in Fig. 2.
Functional enrichment analysis for DEGs
To further elucidate the roles of DEGs, GO functional and KEGG pathway enrichment analyses were performed. As expected, the upregulated DEGs were primarily involved in calcium ion homeostasis (GO: 0055074, n = 3, p = 2.00X10-4). And they also enriched in regulation of cardiac conduction (GO: 1903779), dendrite (GO: 0030425), synapse (GO: 0045202) and oligosaccharide metabolic process (GO: 0009311). In the KEGG pathway analysis, calcium signaling pathway (hsa04020, n = 8, p = 4.38X10-6, Supplement 2 (Ⅰ)) came first, and the aldosterone synthesis and secretion (hsa04925, n = 6, p = 8.73X10-6, Supplement 2 (Ⅰ)) was the second one. The detail information of upregulated DEGs enrichment was showed in Table 1. As for downregulated DEGs, the most common enrichments were protein binding (GO: 0005515), extracellular space (GO: 0005615), collagen-containing extracellular matrix (GO: 0062023), extracellular region (GO: 0005576) and extracellular exosome (GO: 0070062). And the downregulated DEGs were enriched in the KEGG pathways of cancer (hsa05200) and proteoglycans in cancer (hsa05205). The detail information of downregulated DEGs enrichment was showed in Table 2.
PPI network construction from DEGs
The DEGs were further analyzed using the STRING database to construct the PPI network, and the general PPI network with all of the 270 DEGs were showed in Fig. 3. Furthermore, the constructed PPI network was exported into Cytoscape software, and subjected to the sub-module PPI network construction using the MCODE tool. As shown in Supplement 3 ((Ⅰa) for Module 1, (Ⅰb) for Module 2 and (Ⅰc) for Module 3), three sub-modules with MCODE score greater than 4.0 were identified from the constructed PPI network. In the Module 3, the DEGs were primarily involved in positive regulation of cytosolic calcium ion concentration (GO: 0007204, n = 3, p = 1.45X10-6), including PTGFR, CCKBR and TACR1 genes. In the KEGG pathway analysis of Module 3, calcium signaling pathway (hsa04020, n = 4, p = 7.60X10-8) with PTGFR, CCKBR, HTR2B and TACR1 genes was enriched firstly. The detail information of Module 3 enrichment analysis was showed in Supplement 3 (Ⅱ). Other modules (Module 1 and 2) were not enriched successfully due to the few nodes.
Clinical manifestations of study participants
Thirteen patients with diagnosed APA (ages: 27–69 years) and 11 patients with NFA (as control group) were recruited in this study, which used to confirm the mRNA expression of several DEGs by RT-qPCR. Clinical characteristics of these patients were summarized in Supplement 4. The systolic blood pressure (SBP), diastolic blood pressure (DBP), and aldosterone of APA group were all higher, and the plasma K+, PRA and tumor size were lower than that in NFA group. The results above showed that the clustering on clinical manifestations of these two groups was obvious, which suitable for the subsequent RT-qPCR analysis.
The mRNA expression of several DEGs by RT-qPCR
To confirm the results of bioinformatics analysis, RT-qPCR was performed to detect the mRNA expression of 7 upregulated genes (PCP4, ATP2A3, CYP11B2, CLCN5, HTR4, VDR and AQP2) among the intersection of DEGs, which related to aldosterone synthesis and secretion and calcium signaling regulation (the proteins encoded by the above seven genes and their biological functions were showed in Supplement 5). The mRNA levels of CYP11B2, a well-known upregulated gene, was also tested positively in our cohort (24.420 folds of NFA, p < 0.001). And also, the HTR4 and AQP2 were significantly increased in APA samples compared to NFA (3.753 folds of NFA, p = 0.002 and 11.487 folds of NFA, p = 0.018). The fold changes, p values of all the 7 genes and the box plots of 3 upregulated genes by RT-qPCR were showed in Table 3 and Fig. 4.