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. 2024 Aug 15;75(2):1165–1175. doi: 10.1016/j.identj.2024.07.012

The Predictive Value of BUB1 in the Prognosis of Oral Squamous Cell Carcinoma

Xiaoqian Li 1,⁎
PMCID: PMC11976542  PMID: 39147662

Abstract

Background

Oral squamous cell carcinoma (OSCC) is the most common type of malignant tumour in the oral cavity, and it is known for its poor prognosis. Budding uninhibited by benzimidazoles 1 (BUB1) may be related to cancer prognosis; however, the specific relationship between BUB1 and OSCC prognosis remains largely unexplored.

Methods

The mRNA levels of BUB1 were analysed using data from the TCGA_OSCC and GSE23558 cohorts. OSCC samples from the TCGA_OSCC dataset were divided into low- and high-BUB1 expression groups based on the median BUB1 level. Furthermore, results of survival analysis, tumour mutation burden (TMB), gene set enrichment analysis (GSEA) pathways, and drug-sensitivity analysis were compared between the 2 groups.

Results

Based on the data from the TCGA_OSCC and GSE23558 cohorts, BUB1 mRNA levels were significantly upregulated in OSCC tissues compared to healthy controls. Moreover, high expression of BUB1 may serve as an independent indicator of poor prognosis in OSCC. Additionally, patients with high BUB1 expression also exhibited increased levels of immune checkpoints and TMB, suggesting that patients with high BUB1 expression may benefit from immunotherapy. Mechanistically, transcription factors ZFP64, TCF3, and ZNF281 were found to potentially bind to the promoter region of BUB1, thereby regulating its gene expression. Furthermore, GSEA results showed that BUB1 expression was closely related to cell cycle and tumour-related pathways in OSCC. Drug-sensitivity analysis showed that patients with high BUB1 expression may be more sensitive to gemcitabine, paclitaxel, or imatinib.

Conclusions

Collectively, results demonstrated that high BUB1 levels may be related to a poor prognosis of OSCC, highlighting its potential as a novel prognostic biomarker for OSCC.

Key words: Oral squamous cell carcinoma, BUB1, Prognosis, Immune, Transcription factors

Introduction

Oral squamous cell carcinoma (OSCC) is a highly prevalent malignant tumour in the oral cavity, often associated with high incidence and poor prognosis.1, 2, 3 OSCC usually occurs in certain parts of the oral cavity, such as the lateral and ventral surfaces of the tongue and floor of the mouth.4 Presently, conventional treatments for OSCC include the excision of the primary tumour with or without dissection of lymph nodes.5,6 In clinical cases, metastatic lymph node occurs in approximately 30% to 50% of patients with OSCC, inevitably resulting in poor prognosis.7,8 Early detection also affects the prognosis for OSCC. Research has shown that patients with OSCC diagnosed at advanced stages (III and IV) had a lower overall survival rate compared with those with OSCC diagnosed at early stages (I and II).9 Unfortunately, OSCC is most often diagnosed at an advanced clinical stage, resulting in a 5-year survival rate of 25% to 50% in patients experiencing local relapse and distant metastasis.10,11 Thus, uncovering promising biomarkers is an attractive option for the early detection and prognosis of OSCC.

Research has indicated that members of the budding uninhibited by benzimidazoles (BUB) family, specifically budding uninhibited by benzimidazoles 1 (BUB1; also known as BUB1A) and BUBR1 (also known as BUB1B), are correlated with the prognosis of patients with cancer.12,13 Delgado et al13 found that elevated levels of BUBR1 were linked to decreased survival rates in canine OSCC. Additionally, BUB1 encodes a kind of multidomain protein kinase, which plays a crucial role in the mitotic checkpoint for spindle assembly.14,15 Mutation and aberrant expression of BUB1 have been reported to be correlated with the progression of various kinds of cancers.16,17 For example, BUB1 was found to promote the proliferation of liver cancer cells indirectly.15 Moreover, upregulated BUB1—along with 3 other genes—was found to contribute to the poor prognosis of ovarian cancer.18 In lung cancer, elevated BUB1 expression has been evidenced to be related to poor prognosis, and BUB1 overexpression was able to promote lung cancer cell proliferation and migration.19 BUB1 has been increasingly reported to be an oncogene in various cancers, which indicates the crucial role of BUB1 in cancer. However, to the best of the researcher's knowledge, BUB1 has not been systematically studied in OSCC.

Therefore, this research aimed to investigate the potential association between BUB1 and the occurrence and prognosis of OSCC; this goal would be achieved via a series of bioinformatics analyses of OSCC-related data in The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) public databases.

Materials and methods

Data preparation

In all, mRNA profiles and corresponding clinical data from 358 patients with OSCC were obtained from the TCGA database (https://tcga-data.nci.nih.gov/tcga/), comprising 358 OSCC tissues and 32 paired adjacent tissues. Amongst the 358 patients with OSCC, 355 patients from TCGA_OSCC cohort with complete survival information were included for further analysis. Clinical information of 355 patients with OSCC is summarised in the Table.

Table.

Clinicopathologic characteristics of patients with oral squamous cell carcinoma from The Cancer Genome Atlas database.

Characteristics Patients (N = 355)
No. %
Age, y ≤60 (median) 180 50.70
>60 (median) 175 49.30
Pathologic stage I 15 4.23
II 82 23.10
III 71 20.00
IV 177 49.86
Unknown 10 2.82
Survival time Long (>5 y) 33 9.30
Short (<5 y) 322 90.70
Overall survival status Deceased 155 43.66
Alive 200 56.34
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In this study, “OSCC,” “oral squamous cell carcinoma,” “patient,” and “tumor tissue” were selected as the key words to search the related datasets from GEO database. The GSE23558 (including 27 OSCC samples and 5 healthy samples, processing on Agilent-014850 Whole Human Genome Microarray 4 × 44K G4112F platform) and GSE65858 (including 185 OSCC samples with complete survival information, processing on Illumina HumanHT-12 V4.0 expression beadchip platform) datasets were obtained from the GEO (https://www.ncbi.nlm.nih.gov/geo/) database.

Differential expression analysis

In the TCGA_OSCC dataset, on the basis of the median expression level of BUB1, all OSCC specimens were divided into 2 groups: a group with high BUB1 levels (H-BUB1) and a group with low BUB1 levels (L-BUB1). Differentially expressed genes (DEGs) between H-BUB1 and L-BUB1 groups were identified by “limma” R package.20 Genes with a P value <.05 and |Log2 fold change| > 1 were considered DEGs.

Survival analysis

Kaplan–Meier (KM) survival curve was drawn based on the samples with complete survival information, using the survival package and the survminer package (https://CRAN.R-project.org/package=survminer) in R language. The survival differences between the groups were evaluated by log-rank test.

Gene set enrichment analysis (GSEA)

To identify signalling pathways related to BUB1 in the TCGA_OSCC cohort, GSEA was conducted using the gene set (c2.cp.kegg.v7.0.symbols) downloaded from the Molecular Signatures Database (MsigDB). Then, GSEA was conducted using the GSEA software (version: 4.0).

Single-sample GSEA (ssGSEA)

The composition of tumour-infiltrating immune cells often predicts the effectiveness of immunotherapy and, consequently, the prognosis of patients with cancer.21,22 In this study, ssGSEA of immune cell infiltration was utilised to determine the association between BUB1 expression levels and immune cell infiltration levels. Marker genes for 28 immune cell types were referenced from a previous study.23 Next, the ssGSEA was conducted to evaluate immune cell infiltration in H-BUB1 and L-BUB1 groups based on the expression levels of the marker genes for immune cells.

Screening BUB1-related transcription factors (TFs)

In the TCGA_OSCC cohort, differentially expressed TFs (DE-TFs) between healthy and OSCC tissues were identified by the “limma” R package.20 Genes with a P value <.05 and |Log2 fold change| > 1 were considered DE-TFs.

The correlation between the mRNA level of BUB1 and TF was analysed by the Spearman correlation coefficient (P < .05 and Rho > 0.3 as thresholds).

Prediction of TF binding sites

The sequence of the promoter region of BUB1, 1000 bp upstream from the transcriptional start site, was obtained from UCSC (http://genome.ucsc.edu/). The JASPER database (https://jaspar.genereg.net/) was utilised to retrieve the TF motifs. The online tool FIMO (https://meme-suite.org/meme/tools/fimo) was then used to predict the transcription binding site of TF at the promoter region upstream of the BUB1 gene.

Drug-sensitivity analysis

Resistance to anticancer therapy in patients with OSCC is a significant factor contributing to poor treatment outcomes.24 To improve the prognosis of OSCC patients, candidate small molecule compounds that may be used to treat OSCC were screened using the Genomics of Drug Sensitivity in Cancer (GDSC; www.cancerrxgene.org) and Cancer Therapeutics Response Portal (CTRP; https://portals.broadinstitute.org/ctrp/) databases. The half-maximal inhibitory concentration (IC50) values of 265 and 481 small molecules in 50 cell lines from the GDSC and CTRP databases, respectively, were collected. Next, Pearson correlation analysis was performed to determine the correlation between the mRNA levels of ZFP64, ZNF281, TCF3, or BUB1 and the IC50 value of each drug.

Statistical analyses

The differential expression of BUB1 mRNA between groups was determined by Wilcoxon rank-sum test. The effect of BUB1 mRNA level and different clinicopathologic features (age, sex, TNM stage, etc) on the overall survival (OS) was determined by multivariate Cox regression proportional hazard model. All statistical analyses were conducted using R software v3.5.2. Differences with P values <.05 were considered significant.

Results

mRNA level of BUB1 in OSCC tissues

According to the data in the TCGA_OSCC dataset, BUB1 mRNA level was notably increased in 32 OSCC tissues compared with their paired healthy tissues (Figure 1A). Moreover, when compared with healthy tissues (n = 32), BUB1 levels were still significantly higher in all OSCC tissues (n = 358) in the TCGA_OSCC dataset (Figure 1B). Similarly, an increase in BUB1 mRNA levels were observed in the OSCC tissues (n = 27) compared with controls (n = 5) in a validation dataset (GSE23558) (Figure 1C). These results showed that highly expressed BUB1 may be closely related to the occurrence of OSCC.

Fig. 1.

Fig 1

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The mRNA level of budding uninhibited by benzimidazoles 1 (BUB1) was elevated in oral squamous cell carcinoma (OSCC) tissues. A, Box plots of BUB1 mRNA level in 32 paired healthy (n = 32) and OSCC (n = 32) tissues in the TCGA_OSCC dataset. B, Box plots of BUB1 mRNA level in healthy (n = 32) and OSCC (n = 358) tissues in the TCGA_OSCC dataset. C, Box plots of BUB1 mRNA level in healthy and OSCC tissues in the GSE23558 dataset. D, Box plots of BUB1 level in tumour tissues from patients with OSCC in different stages (I, II, III, and IV). Box plots of BUB1 level in tumour tissues from patients with OSCC in (E) sex and (F) age subgroups.

Next, the relation between BUB1 level and several clinicopathologic features was evaluated by the Wilcoxon rank-sum test. As shown in Figure 1D, the mRNA level of BUB1 tended to increase with increasing TNM stage in the TCGA_OSCC dataset, and significantly differential BUB1 levels were observed in stage I vs stage III, stage II vs stage IV, and stage I vs stage IV (Figure 1D). However, there was no significant correlation between BUB1 level and either sex or age amongst patients with OSCC (Figure 1E and 1F).

GSEA functional analysis

A total of 631 DEGs were screened between H-BUB1 and L-BUB1 groups (Figure S1A). Next, Disease Ontology (DO) and GSEA functional analyses were performed on these DEGs. The results of DO analysis indicated that these 631 DEGs appeared in 124 DO pathways such as “pre-malignant neoplasm,” “in situ carcinoma,” “head and neck carcinoma,” and “oral cavity cancer” signalling pathways (Figure S1B and Table S1). The results of GSEA showed that compared to the L-BUB1 group, 46 pathways (eg, cell cycle, DNA replication, and pathways in cancer) were markedly activated, but a single pathway (linoleic acid metabolism pathway) was notably inhibited in the H-BUB1 group (Figure 2A and 2B and Table S2).

Fig. 2.

Fig 2

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Gene set enrichment analysis (GSEA) functional analysis. GSEA identifies cancer-related pathways associated with the BUB1 gene. A, GSEA showed the enhanced activity of cell cycle, DNA replication, homologous recombination, mismatch repair, and spliceosome pathways in the high–BUB1 level (H-BUB1) group. B, GSEA showed the downregulated activity of the linoleic acid metabolism pathway in the H-BUB1 group.

mRNA level of BUB1 may be regulated by TFs

Next, to explore the reason that BUB1 is highly expressed in OSCC, DE-TFs between healthy and OSCC tissues were screened in the TCGA_OSCC dataset. A total of 491 TFs were found to be dysregulated between healthy and OSCC tissues (Figure 3A). Next, the correlation between BUB1 level and 491 DE-TFs was calculated based on the data in the TCGA_OSCC dataset, respectively. According to the thresholds of P value <.05 and |Cor| > 0.5, 48 DE-TFs were positively correlated with BUB1 level (Figure 3B and 3C). Meanwhile, TF binding sites were searched on the 1000-bp promoter regions of BUB1, and it was observed that ZFP64 (UN0588.1), TCF3 (MA0522.2), and ZNF281 (MA1630.2) may have binding sequences in promoter regions of BUB1 (Table S3). These results indicated that ZFP64, TCF3, and ZNF281 may regulate the transcription of BUB1 through binding to the BUB1 promoter region.

Fig. 3.

Fig 3

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The mRNA level of budding uninhibited by benzimidazoles 1 (BUB1) could be regulated by transcription factors (TFs) (ZFP64, TCF3, and ZNF281). A, Venn diagram showing the 491 common TFs (DE-TFs) between differentially expressed genes (DEGs) and TF-related genes. B, A total of 48 DE-TFs were positively correlated with BUB1. Thus, the network based on BUB1 and 48 DE-TFs was constructed. C, The positive correlations between BUB1 and TFs (ZFP64, TCF3, and ZNF281). D, The ZFP64 Chip-seq data showed an obvious binding peak on the BUB1 gene in the GSM2026876 dataset from the Cistrome database. E, The TCF3 Chip-seq data showed an obvious binding peak on the BUB1 gene in the GSM1782918 dataset from the Cistrome database. F, The ZNF281 Chip-seq data showed an obvious binding peak on the BUB1 gene in the GSM2026891 dataset from the Cistrome database. G, The network of BUB1, ZFP64, TCF3, and ZNF281 and their co-expression genes was constructed and analysed by GeneMANIA.

Furthermore, GSM2026876, GSM2026891, and GSM1782918 datasets from the Cistrome database (http://cistrome.org/db/#/) were used to further explore the relationship between BUB1 and 3 TFs (ZFP64, ZNF281, TCF3). The data in Figure 3D through 3F show the potential binding sites of TFs (ZFP64, TCF3, or ZNF281) in the BUB1 promoter regions. These results further verified that ZFP64, TCF3, and ZNF281 may regulate the transcription of BUB1.

Meanwhile, the GeneMANIA network was used to analyse the potential co-expression, co-localisation, pathways, and protein–protein interactions amongst BUB1 and 3 TFs (ZFP64, TCF3, and ZNF281). The results showed that there were potential interactions amongst BUB1, ZFP64, TCF3, and ZNF281 and 20 genes (Figure 3G).

Correlations between BUB1 mRNA level and immune infiltrates

To assess immune infiltration of tumour tissues in the TCGA_OSCC dataset, ssGSEA was conducted. Amongst 28 types of immune cells, significant differences were found in 14 immune cells (eg, activated CD4 T cell, CD56dim natural killer cell, eosinophil, gamma delta T cell, macrophage, mast cell, memory B cell, monocyte, natural killer T cell, neutrophil, plasmacytoid dendritic cell, T follicular helper cell, type 17 T helper cell, and type 2 T helper cell) between H-BUB1 and L-BUB1 groups (Figure 4A). Meanwhile, the mRNA level of BUB1 was negatively correlated with the proportion of 10 immune cells (including neutrophil, plasmacytoid dendritic cell, T follicular helper cell, type 17 T helper cell, CD56dim natural killer cell, eosinophil, macrophage, mast cell, monocyte, gamma delta T cell), and was positively correlated with the proportion of 3 immune cells (including activated CD4 T cell, type 2 T helper cell, and memory B cell) (Figure 4B).

Fig. 4.

Fig 4

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Correlations between BUB1 level and immune infiltrates. A, Box plots of the proportions of 28 immune cells in oral squamous cell carcinoma (OSCC) tissues between the high–BUB1 level (H-BUB1) and low–BUB1 level (L-BUB1) groups. B, The scatter plot of the correlation between BUB1 level and the proportions of 13 immune cells. C, Box plots of the levels of 12 immune checkpoints in OSCC tissues between H-BUB1 and L-BUB1 groups.

Next, mRNAs levels of 34 immune checkpoints between H-BUB1 and L-BUB1 groups were observed. The results showed that the levels of 12 immune checkpoints including TNFRSF9, CD200, CD40, CD276, TNFSF4, CD86, TNFRSF8, CD80, TNFSF14, ICOS, LAIR1, and LGALS9 were significantly increased in the H-BUB1 group compared to the L-BUB1 group (Figure 4C).

BUB1 may be an independent prognostic factor in OSCC

To investigate the effect of BUB1 on OSCC prognosis, a KM survival analysis and time-dependent receiver operating characteristic curves were conducted. KM curves showed that patients with OSCC in the H-BUB1 group exhibited a markedly worse overall survival (OS) compared with patients in the L-BUB1 group in both the TCGA_OSCC and GSE65858 datasets (Figure 5A and 5B). Moreover, the area under the curve values at 2, 4, and 6 years in the TCGA_OSCC dataset were 0.54, 0.56, and 0.65, respectively (Figure 5C). The area under the curve values at 2, 4, and 6 years in the GSE65858 dataset were 0.55, 0.62, and 0.85 (Figure 5D). These data suggest that BUB1 was capable of predicting the prognosis of patients with OSCC.

Fig. 5.

Fig 5

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BUB1 may be an independent prognostic factor in oral squamous cell carcinoma (OSCC). A and B, Kaplan–Meier curves showed the overall survival of patients with OSCC in the high–BUB1 level (H-BUB1) and low–BUB1 level (L-BUB1) groups in the TCGA_OSCC and GSE65858 datasets. The x-axis represents survival time, the y-axis represents survival rate, and different colours represent different groups. P values were calculated based on the log-rank test. C and D, Time-dependent receiver operating characteristic curves show area under the curve values at 2- (red), 4- (blue), and 6-year (green) survival in the TCGA_OSCC and GSE65858 datasets. E, The multivariate Cox analysis of the BUB1 gene and age, stage (I, II, III and IV), and sex (female and male). Hazard ratio > 1, patients exhibit a higher risk of death; hazard ratio < 1, patients exhibit a lower risk of death. F and G, Top 30 correlations between the mRNA levels of BUB1, ZNF281, TCF3, ZFP64, and the IC50 value of antitumour reagents in the Genomics of Drug Sensitivity in Cancer (GDSC) and Cancer Therapeutics Response Portal (CTRP) databases, respectively.

Next, to evaluate whether BUB1 is an independent prognostic indicator, 343 samples with complete clinical information (including stage, sex, and age) in the TCGA_OSCC dataset were selected for multivariate Cox analysis. Thus, age, sex, stage, and BUB1 expression were used as input variables in the multivariate Cox analysis. Results showed that BUB1 expression was significantly related to OS in patients with OSCC and that higher expression of BUB1 was related to worse outcome in patients with OSCC (Figure 5E). These data indicate that BUB1 may be an independent predictor for prognosis in OSCC.

Furthermore, the results of drug sensitivity analysis revealed that the mRNA levels of BUB1, ZFP64, TCF3, and ZNF281 were correlated with the IC50 value of some antitumour drugs (Figure 5F and 5G and Tables S4 and S5). The data in Tables S4 and S5 indicate that BUB1 mRNA level was negatively related to the IC50 value of gemcitabine, paclitaxel, or imatinib in both GDSC and CTRP databases, suggesting that patients with high BUB1 levels may be more sensitive to these drugs.

Mutation landscape analysis in OSCC

Next, the differences in copy number variations (CNVs) and somatic variations between H-BUB1 and L-BUB1 groups were analysed. Results showed that the incidence of CNVs in the H-BUB1 group was lower than that in the L-BUB1 group (Figure 6A and 6B). Meanwhile, somatic mutation level and tumour mutation burden (TMB) in H-BUB1 and L-BUB1 groups were analysed based on the somatic mutation data obtained from the TCGA_OSCC cohort. As shown in Figure 6C and 6D, the mutation rates of TP53 (62%) and FAT1 (21%) in the H-BUB1 group were lower than those in the L-BUB1 group (65% and 25%, respectively). Conversely, the mutation rate of TTN (36%) in the H-BUB1 group was higher than that in the L-BUB1 group (32%) (Figure 6C and 6D). Additionally, TMB was notably increased in the H-BUB1 group compared with the L-BUB1 group (Figure 6E).

Fig. 6.

Fig 6

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Mutation landscape analysis in oral squamous cell carcinoma (OSCC). A and B, The pie chart of copy number variations including single copy deletion, diploid normal copy, and low-level copy number amplification in high–BUB1 level (H-BUB1) and low–BUB1 level (L-BUB1) groups. C and D, Waterfall plots displaying somatic mutations in H-BUB1 and L-BUB1 groups. The colour scheme of the bars within the plot indicates the type of mutation and is further explained below the plot. The stacked bars at the top represent the number of somatic mutations identified in each patient. The sidebar shows the percentage of patients with a mutation in a certain gene. E, Box plots of log10-transformed tumour mutation burden (TMB) [Log10(TMB)] in OSCC tissues between H-BUB1 and L-BUB1 groups. Horizontal bars indicate median values; boxes represent the interquartile range.

Discussion

Accumulating evidence has highlighted the oncogenic role of BUB1 in various cancers, including neuroblastoma and liver cancer.15,25 In this study, the role of BUB1 in OSCC was observed for the first time. Analysis of OSCC-related data from public databases revealed that BUB1 mRNA level was significantly upregulated in OSCC tissues compared with healthy controls. Moreover, high BUB1 expression in patients with OSCC was associated with a poorer prognosis. Furthermore, multivariate Cox analysis revealed that BUB1 may serve as an independent predictor for prognosis in OSCC.

To explore the reason that BUB1 is highly expressed in OSCC, this research focussed on TFs known for their role in gene transcription modulation.26 Previous studies identified potential interactions between BUB1 and specific TFs (including POLR2A, ZBTB11, ELF1, and KLF9) in epithelial ovarian cancer.26 However, the current research revealed a potential association between BUB1 and 3 TFs (ZFP64, TCF3, and ZNF281) in OSCC. Evidence has shown that ZNF143 could upregulate the level of BUB1B via binding to the promoter regions of BUB1B.27 Qiu et al28 reported that ZFP64 could bind to the promoters of PD-1 and CTLA-4, leading to increased gene expression and contributing to development of esophageal cancer. Li et al29 demonstrated that TCF3 is involved in transcriptional regulation of ID1, playing a role in esophageal squamous cell carcinoma oncogenesis. Meanwhile, Zhang et al30 revealed that ZNF281 could contribute to liver cancer progression by partially downregulating annexin A10 (a tumour suppressor) at the transcriptional level. The current research revealed that these 3 TFs (ZFP64, TCF3, and ZNF281) could bind to the promoter regions of BUB1, suggesting that BUB1 may be modulated by ZFP64, TCF3, and ZNF281 at the transcriptional level.

Furthermore, GSEA results indicated that some signalling pathways such as “cell cycle” and “pathway in cancer” are more activated in the H-BUB1 group compared with the L-BUB1 group. Accelerated cell cycle progression can result in uncontrolled cell proliferation, ultimately leading to cancer development.31 Studies have demonstrated that promoting cell cycle arrest could inhibit proliferation in OSCC cell lines.32,33 BUB1 is a key kinase involved in mitosis, which is essential for correct spindle assembly checkpoint and chromosome alignment.14,34 The connection between BUB1 and cell proliferation or cell cycle has been studied.35,36 Maeda et al37 found that knockdown of BUB1 led to an increase in cells in the M phase, resulting in cell cycle arrest in the M phase and cell growth inhibition in HeLa cells. However, the effect of BUB1 on cell cycle progression in OSCC remain unclear and warrants further investigation. Additionally, BUB1 mRNA level also related to some other cancer-related pathways (eg, STAT3, AKT/Bcl2, Wnt/β-catenin signallings) (Table S2). Previous studies have reported the molecular mechanism of BUB1 in different types of cancers. For example, Huang et al38 found that deficiency of BUB1 could prevent osteosarcoma development through inactivating PI3K/AKT signalling. Jiang et al. showed that BUB1 could contribute to bladder cancer progression by activation of STAT3 signalling.39 Zhang et al40 indicated that BUB1 was able to promote the proliferation and epithelial–mesenchymal transition in glioblastoma cells through upregulating Wnt/β-catenin signalling. Thus, it is plausible that BUB1 may play an oncogenic role in OSCC through modulating these signalling pathways, further research is needed to confirm this assumption.

Evidence has shown that tumour-infiltrating immune cells in the tumour microenvironment are correlated with the prognosis of patients with cancer.41,42 For example, natural killer cells have been associated with a favourable prognosis of patients with neuroblastoma.43 Additionally, Qi et al44 found that BUB1 not only could predict the prognosis of patients with liver cancer but also act as an immune status indicator. Moreover, Song et al25 found that amongst patients with neuroblastoma, L-BUB1 levels exhibited increased counts of natural killer cells compared to H-BUB1 levels. Results of the present study showed that BUB1 levels were negatively correlated with the infiltration of CD56dim natural kill cells, and these findings were consistent with the results of Song et al25 in 2022. These data suggest that patients with elevated BUB1 levels may have a poor prognosis and reduced infiltration of antitumour immune cells, such as natural killer cells.

It has been shown that patients with cancer often experience compromised immune function.45 Immune checkpoint inhibitors have been utilised in cancer therapy via targeting the dysfunctional immune system and promoting the activation of antitumour immune cells to eradicate cancer cells.46 Some studies showed that patients with high TMB may possess clinical benefits from immune checkpoint inhibitors.47 Data from the present study showed that patients with elevated BUB1 expression displayed higher TMB and higher levels of 12 immune checkpoints (TNFRSF9, CD200, CD40, CD276, TNFSF4, CD86, TNFRSF8, CD80, TNFSF14, ICOS, LAIR1, and LGALS9) compared with the L-BUB1 group. These data suggest that patients with elevated BUB1 expression may benefit from immune checkpoint inhibitors.

Conclusions

In the current study, comprehensive bioinformatics analyses revealed an elevated level of BUB1 in OSCC. Additionally, high BUB1 levels may be related to poor prognosis of patients with OSCC. BUB1 may potentially serve as an independent predictor for prognosis in OSCC. Collectively, BUB1 may act as a novel prognostic biomarker for OSCC.

Conflict of interest

None disclosed.

Footnotes

Supplementary material associated with this article can be found in the online version at doi:10.1016/j.identj.2024.07.012.

Appendix. Supplementary materials

mmc1.docx (14KB, docx)
mmc2.jpg (333.3KB, jpg)
mmc3.xlsx (18.7KB, xlsx)
mmc4.xlsx (18.8KB, xlsx)
mmc5.xlsx (9.5KB, xlsx)
mmc6.xlsx (46.6KB, xlsx)
mmc7.xlsx (81.7KB, xlsx)

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Supplementary Materials

mmc1.docx (14KB, docx)
mmc2.jpg (333.3KB, jpg)
mmc3.xlsx (18.7KB, xlsx)
mmc4.xlsx (18.8KB, xlsx)
mmc5.xlsx (9.5KB, xlsx)
mmc6.xlsx (46.6KB, xlsx)
mmc7.xlsx (81.7KB, xlsx)

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