Expression profiles of BOLA family members in OC
We firstly analyzed dysregulated transcriptional levels of BOLA family members in 20 various types of human cancers in the Oncomine database. As listed in Fig. 1, BOLA family members might act as either tumor promoter or suppressor in diverse kinds of tumors. In overall OC patients, the mRNA expression levels of BOLA1 and BOLA2 were significantly upregulated than that in normal ovarian tissues in Bonome’s dataset with a fold change of 1.373 and 3.545 respectively, however, no data on the differential mRNA expression of BOLA3 in overall OC tissues compared with normal ovarian tissues, as shown in Table 1. We also summarized the mRNA levels of BOLA family members in different types of OC that obtained from Oncomine datasets in Table I. For BOLA1, the mRNA expression level was significantly higher in serous, endometrioid, mucinous, and clear cell adenocarcinoma than normal ovarian tissues in Lu’s dataset. With regard to BOLA2, the mRNA expressions were higher in serous, endometrioid and clear cell adenocarcinoma in Lu’s dataset and were higher in serous, endometrioid, mucinous and clear cell adenocarcinoma than normal ovarian tissues in Hendrix’s dataset. As to BOLA3, the mRNA expressions were higher in serous, endometrioid, and mucinous adenocarcinoma than that in normal ovarian tissues.
Additionally, the GEPIA database was utilized to contrast the differential mRNA expression of BOLA family members between OC and normal ovarian tissues as well. As shown in Fig. 2A, the expression levels of BOLA2 and BOLA3 were remarkably higher, and mRNA level of BOLA1 was slightly upregulated (P > 0.05) in OC tissues than normal ovarian tissues, which corresponded with results of the Oncomine database except for that of BOLA1. Moreover, the correlation between mRNA expression levels of BOLA family members and different stages of OC were also analyzed, and only BOLA3 was significantly upregulated in higher stage (Fig. 2B).
Moreover, we analyzed the protein expression of BOLA family members in normal ovarian tissues and OC tissues using HPA database. As shown in Fig. 3, we found that ovarian stroma cells had medium BOLA1 staining in 3 cases of normal ovarian tissues. Relatively, among 11 cases of OC tissues examined, 2 cases had medium BOLA2 staining, 5 cases had low BOLA2 staining and 4 cases had no BOLA1 staining. As to for BOLA2, it was undetected in normal ovarian tissues,however, among the examined 12 OC tissues, 9 cases had medium BOLA2 staining, 1 case had low BOLA2 staining and 2 cases had no BOLA2 staining. Considering BOLA3, the data showed that there was no BOLA3 staining in normal ovarian tissues༌in comparison, among 11 cases of OC tissues examined, there were 2 cases of mediumBOLA3 staining, 3 cases of low BOLA3 staining and 6 cases of no BOLA3 staining.
Taken together, these results indicated BOLA family members may function as oncogenes in OC, and may be a possible therapeutic target of precision therapy for patients with OC.
Prognostic value of BOLA family members in patients with OC
We firstly appraised the relationship between the mRNA expression of BOLA family members and the survival in all OC patients via Kaplan-Meier plotter analysis. The data demonstrated that the increased BOLA3 mRNA level was associated with shorter PFS and OS of OC patients, while decreased BOLA2 mRNA level was associated with shorter PFS of OC patients (Fig. 4). However, there was no relation between BOLA3 mRNA level and prognosis of OC patients.
Then, we also assessed the prognostic values of BOLA family members in different subtypes of OC patients who were defined according to different histology, clinical stages, pathological grades, and TP53 status by Kaplan–Meier plotter analysis. As shown in Table II. As to OS, increased mRNA expression of BOLA3 was significantly related to shorter OS in serous OC patients for different histology. For clinical stages, low mRNA expression of BOLA2 predicted poor OS in stage 2, low mRNA expression of BOLA3 was related to shorter OS in stage 4, while high mRNA expression of BOLA3 predicted the poor OS in stage 3. In terms of pathological grades, high BOLA1 mRNA expression was linked to poor OS in grade 1–2, while high mRNA expression of BOLA2 and BOLA3 predicted favorable OS in grade 3. Interestingly, increased expression of BOLA2 predicted favorable OS in mutated TP53 type, while increased expression of BOLA1was associated with longer OS in wild-type TP53.
As referred to PFS (Table III), increased mRNA expression of BOLA3 were significantly related to shorter PFS in serous OC patients, and decreased levels of BOLA2 predicted poor PFS in serous OC patients. For clinical stages, high mRNA expression of BOLA2 were found to be connected to longer PFS in stage 1, stage 2, stage 3 and stage 4, high mRNA expression of BOLA1 predicted longer PFS in stage 3, whereas low levels of BOLA1 predicted longer PFS in stage 4. For pathological grades, increased levels of BOLA2 predicted better PFS in all grades, high mRNA expression of BOLA1 and BOLA2 were remarkably related to shorter PFS in grade 1–2, while low expression of BOLA3 predicted shorter PFS. Moreover, increased expression of BOLA2 was correlated with poor PFS in OC patients either with mutated TP53 or wild type.
In general, these results suggested that the mRNA expression levels of BOLA family members could be considered as optional biomarkers for predicting the survival of OC patient.
Genomic Alteration Of Bola Family Genes In Oc
We then explored the possible mechanisms that involved in dysregulation of BOLA family members’ expression in OC. We analyzed the genetic alteration frequency of BOLA family members using the cBioPortal online tool for OC (The Cancer Genome Atlas, Provisional), 606 patients were analyzed totally. The oncoprints included missense mutation, deletion, and amplification, with the ratios of genetic alterations of BOLA family members in OC varied from 1.89–9.95% (Figs. 5A, B). The ratios of genetic mutation in BOLA1, BOLA2, BOLA3 were 9.95% (0.17% mutation, 9.43% amplification, 0.34 deep deletion), 1.89% (amplification), 2.06% (1.89%amplification, 0.17% mutation) respectively. In addition, missense mutation was identified in BOLA1(Figs. 5C). Moreover, the survival curves indicated that cases with or without alterations in one of the BOLAs was not related with OS and PFS (Figs. 5C, D) using Kaplan–Meier plot analysis and log-rank test.
Function And Interaction Of Bola Family Members
A network of three BOLA family members and 20 kinds of proteins that were associated with BOLA family members significantly was set up using the String database and Cytoscape software. The network graph showed that metal-ion binding-related genes including glutaredoxin 5 (GLRX5), glutaredoxin 3 (GLRX3), werner helicase interacting protein 1 (WRNIP1), Zinc finger protein 576 (ZNF576), thimetoligopeptidase(THOP1), fumarylacetoacetate hydrolase domain-containing protein 2A(FAHD2A) and iron-sulfur cluster co-chaperone protein HscB (HSCB) were associated with BOLA family members(Fig. 6A). Next, GO enrichment and KEGG pathway analysis of BOLA family members and their interactors were conducted using DAVID. The BOLA family members were mainly related to mitochondrion and mitochondrion matrix location, BOLA family members and their interactors exerted their functions primarily on metal ion binding and protein disulfide oxidoreductase activity (Fig. 6B). However, no KEGG pathway for BOLA family members and their interactors was enriched. Finally, the Pearson correlation coefficients were calculated between BOLA family members by using correlation analysis in GEPIA and cBioPortal databases, ranging from 0.21 to 0.56 (Fig. 6C).
Gsea Identifies Bolas-regulated Pathways In Oc
To investigate the alteration of BOLA-related pathways in OC, GSEA analysis in OC with high or low expression levels of each BOLA gene were performed, gene sets with a Normalized Enrichment Score (21) > +/−2, FDR < 0.05 and p < 0.05 were identified as the hallmark gene sets, as shown is Fig. 7. In the pathway enrichment analysis, a high expression of BOLA1 were positively correlated with several oxidative phosphorylation (Fig. 7A), while negatively correlated with the focal adhesion in OC (Fig. 7B). High expression of BOLA3 expression was positively correlated with oxidative phosphorylation, proteasome, protein export and glutathione metabolism in OC (Fig. 7C, 7D, 7E, 7F). However, there was no any hallmark gene sets enrichment for high or low BOLA2 expression in OC.