Expression of BUBR1 in human oral potentially malignant disorders and squamous cell carcinoma

A Molecular Hypothesis on Malignant Transformation of Oral Lichen Planus: A Systematic Review and Meta-Analysis of Cancer Hallmarks Expression in This Oral Potentially Malignant Disorder

We aimed to qualitatively and quantitatively analyze, through a systematic review and meta-analysis, the current evidence on the differential expression of the hallmarks of cancer in oral lichen planus (OLP) samples, in order to know the earliest molecular mechanisms that could be involved in the malignant transformation of this oral potentially malignant disorder. We searched MEDLINE/PubMed, Embase, Web of Science, and Scopus for studies published before November 2023. We evaluated the methodological quality of studies and carried out meta-analyses to fulfill our objectives. Inclusion criteria were met by 110 primary-level studies, with 7065 OLP samples, in which the expression of 104 biomarkers were analyzed through immunohistochemistry. Most OLP samples showed sustained cell proliferation signaling (65.48%, 95%CI = 51.87-78.02), anti-apoptotic pathways (55.93%, 95%CI = 35.99-75.0), genome instability (48.44%, 95%CI = 13.54-84.19), and tumor-promoting inflammation events (83.10%, 95%CI = 73.93-90.74). Concurrently, OLP samples also harbored tumor growth suppressor mechanisms (64.00%, 95%CI = 53.27-74.12). In conclusion, current evidence indicates that molecular mechanisms promoting hyperproliferative signaling, an antiapoptotic state with genomic instability, and an escape of epithelial cells from immune destruction, are developed in LP-affected oral mucosa. It is plausible that these events are due to the actions exerted by the chronic inflammatory infiltrate. Malignant transformation appears to be prevented by tumor suppressor genes, which showed consistent upregulation in OLP samples.

Molecular landscape of proliferative verrucous leukoplakia: a systematic review

Proliferative verrucous leukoplakia (PVL) is a rare oral potentially malignant disorder characterised by multifocal origin and unpredictable long-term evolution to oral squamous cell carcinoma (OSCC) or oral verrucous carcinoma (OVC). Currently no predictive biomarkers are in clinical use. We aimed to explore the genomic profile of PVL. A total of 685 cases in 26 studies were included in this review. Genomic data were presented in 15% of studies and biomarker analysis was reported in 85% of studies. At first clinical presentation, PVL is characterised by a high loss of heterozygosity (LOH), similar to OSCC, and low copy number alterations (CNA). As these progress, more CNAs and mutations in CDKN2A and alterations to ELAVL1 expression are noted, but no TP53 mutations are identified. There is significantly lower LOH at 17p in early PVL compared with OSCC (p = 0.037). Deletions in chromosomal loci 17q12, 5q31.1 and amplifications in 7q11.2, 7q22 are shared between early lesions and OVC. PVL shows CNAs at 11q31. WNT signalling pathway genes (SUZ12, CTTN and FOLR3) are enriched in CN-altered regions. PVL stroma shows significantly lower α-SMA and higher CD34 expression than OVC and OSCC. The exact genomic landscape is currently unclear, and further studies are necessary to unravel this mystery.

Influence of PD-1/PD-L1 on immune microenvironment in oral leukoplakia and oral squamous cell carcinoma

OBJECTIVE

To evaluate the relation between the expression of PD-1, PD-L1, CD3, CD8, Foxp3 and clinicopathological features in patients with oral leukoplakia (OLK) and oral squamous cell carcinomas (OSCC) as well as the malignant outcome in OLK patients, and to study the effect of PD-1 and PD-L1 on immune microenvironment in the progression of oral carcinogenesis.

METHODS

We evaluated the expression of PD-1/PD-L1 and composition of CD3+ , CD8+ and Foxp3+ T lymphocytes in OLK and OSCC samples by immunohistochemical (IHC) staining and analyzed their relation with clinical information and malignant transformation in OLK patients.

RESULTS

IHC staining demonstrated that the expression of PD-1 was significantly increased in the high-grade OLK group than in the low-grade OLK group, while PD-L1 was detected mainly in OSCC. The expression of CD3, CD8, and Foxp3 was found higher in the high-grade OLK group than in the low-grade OLK group, and the Foxp3+ cells were found more in the OSCC group than in the high-grade OLK group. PD-1 was significantly correlated with CD3 (p < 0.05, R = 0.52), CD8 (p < 0.05, R = 0.46), and Foxp3 (p < 0.05, R = 0.46), and the low PD-1-expression group showed a better malignant-free survival than high PD-1 expression group in the OLK (p < 0.05).

CONCLUSION

The PD-1/PD-L1 may induce immune suppression in OLK and accelerate the progress of malignant transformation.

BUBR1 as a Prognostic Biomarker in Canine Oral Squamous Cell Carcinoma

Chromosomal instability (CIN) plays a key role in the carcinogenesis of several human cancers and can be related to the deregulation of core components of the spindle assembly checkpoint (SAC) including BUBR1 protein kinase. These proteins have been related to tumor development and poor survival rates in human patients with oral squamous cell carcinoma (OSCC). To investigate the expression of the SAC proteins BUBR1, BUB3 and SPINDLY and also Ki-67 in canine OSCC, we performed an immunohistochemical evaluation in 60 canine OSCCs and compared them with clinical and pathological variables. BUBR1, Ki-67, BUB3 and SPINDLY protein expressions were detected in all cases and classified as with a high-expression extent score in 31 (51.7%) cases for BUBR1, 33 (58.9%) cases for BUB3 and 28 (50.9%) cases for SPINDLY. Ki-67 high expression was observed in 14 (25%) cases. An independent prognostic value for BUBR1 was found, where high BUBR1 expression was associated with lower survival (p = 0.012). These results indicate that BUBR1 expression is an independent prognostic factor in these tumors, suggesting the potential use for clinical applications as a prognostic biomarker and also as a pharmacological target in canine OSCC.

Expression of spindle assembly checkpoint proteins BubR1 and Mad2 expression as potential biomarkers of malignant transformation of oral leukoplakia: an observational cohort study

Background

The Spindle Assembly Checkpoint (SAC) is a surveillance mechanism essential to ensure the accuracy of chromosome segregation during mitosis. Our aim was to evaluate the expression of SAC proteins in oral carcinogenesis, and to assess their potential in predicting malignant transformation of oral leukoplakia.

Material and Methods

We analysed the immunoexpression of BubR1, Mad2, Bub3, and Spindly proteins in 64 oral biopsies from 52 oral leukoplakias and 12 normal tissues. Univariate and multivariate analysis were performed to evaluate predictive factors for malignant transformation (MT).

Results

We observed that BubR1 and Mad2 were more highly expressed in high dysplasia grade lesions than in low grade or normal tissues (P<0.05). High expression of Spindly was significantly correlated with a high Ki-67 score (P=0.004). Six (11.5%) oral leukoplakias underwent malignant transformation. In univariate analysis, the binary dysplasia grade (high grade) (P<0.001) was associated with a higher risk of malignant transformation as well as high BubR1 (P<0.001) and high Mad2 (P=0.013) expression. In multivariate analysis, high expression of BubR1 and Mad2 when combined showed an increased risk for malignant transformation (P=0.013; HR of 4.6, 95% CI of 1.4-15.1).

Conclusions

Our findings reveal that BubR1 and Mad2 were associated with an increased risk for malignant transformation independently of histological grade and could be potential and useful predictive risk markers of malignant transformation in oral leukoplakias.

Key words:BubR1, Mad2, Spindly, Bub3, Oral Leukoplakia, epithelial dysplasia, Oral squamous cell carcinoma.

Immunohistochemical expression of budding uninhibited by benzimidazole related 1 in leukoplakia and oral squamous cell carcinoma

Background:

Budding uninhibited by benzimidazole related 1 (BUBR1) is an important protein in the mitotic spindle assembly checkpoint. Alterations in expression of BUBR1 have been reported in many premalignant and malignant lesions.

Aim:

To compare the expression of BUBR1 with respect to the normal mucosa and degree of dysplasia in oral leukoplakia (OL) and also with respect to different histopathological grades of oral squamous cell carcinoma (OSCC).

Materials and Methods:

Neutral buffered formalin-fixed and paraffin-embedded biopsy specimens 30 each of normal, OL and OSCC tissue were included in this study. The expression of BUBR1 was detected using immunohistochemistry (IHC). The scores obtained were subjected to ANOVA test.

Results:

Significant correlation was found in immunostaining between normal, dysplasia and OSCC groups with a P value of 0.00001. The expression of BUBR1 was significant when compared with different degrees of dysplasia and in different histopathological grades of OSCC with a P value of 0.00001.

Conclusion:

Higher IHC scores were obtained with increased histopathological grades of OL and OSCC suggesting its role as a prognostic indicator.

BUBR1 overexpression predicts disease-specific survival after nephroureterectomy in patients with upper tract urothelial carcinoma

OBJECTIVE

To date, there are few reliable markers to distinguish tumors with aggressive characteristics in upper tract urothelial carcinoma. The purpose of this study was to identify a biomarker related to genetic instability (chromosomal instability or microsatellite instability) with prognostic value, in patients with upper tract urothelial carcinoma.

METHODS

Expression of chromosomal instability-related markers (BUBR1, p53, polo-like kinase 1) and microsatellite instability-related markers (mismatch repair proteins, MLH1 and MSH2) were assessed by immunohistochemistry in 100 patients who had radical nephroureterectomy for upper tract urothelial carcinoma. Numerical aberrations of chromosomes 7, 9 and 17 were evaluated by fluorescence in situ hybridization, which allowed an estimation of the degree of chromosomal instability. BUB1B copy number was examined by array-based comparative genomic hybridization in 32 patients with upper tract urothelial carcinoma.

RESULTS

BUBR1 status was most significantly correlated with chromosomal instability-related and low mismatch repair parameters, according to the molecular biomarkers examined. Overexpression of BUBR1 is frequently detected in tumors with higher histological grade (P < 0.0001) and is significantly associated with chromosomal instability (P = 0.0071). Array-based comparative genomic hybridization revealed that no tumors (0%) showed BUB1B amplification and gain, indicating that overexpression of BUBR1 was independent of BUB1B copy number. For disease-specific survival, BUBR1 overexpression, lymphovascular invasion, pathological tumor stage, pathological lymph node involvement and low MSH2 expression were significant prognostic factors in univariate analyses. In multivariate analyses, BUBR1 overexpression was an independent prognostic factor for disease-specific survival (P = 0.0483, risk ratio 3.76, 95% confidence interval: 1.01-18.43).

CONCLUSIONS

BUBR1 may have significant potential as a biomarker for estimating disease-specific survival in patients with upper tract urothelial carcinoma treated by radical nephroureterectomy.

BubR1 Acts as a Promoter in Cellular Motility of Human Oral Squamous Cancer Cells through Regulating MMP-2 and MMP-9

BubR1 is a critical component of spindle assembly checkpoint, ensuring proper chromatin segregation during mitosis. Recent studies showed that BubR1 was overexpressed in many cancer cells, including oral squamous cell carcinomas (OSCC). However, the effect of BubR1 on metastasis of OSCC remains unclear. This study aimed to unravel the role of BubR1 in the progression of OSCC and confirm the expression of BubR1 in a panel of malignant OSCC cell lines with different invasive abilities. The results of quantitative real-time PCR showed that the mRNA level of BubR1 was markedly increased in four OSCC cell lines, Ca9-22, HSC3, SCC9 and Cal-27 cells, compared to two normal cells, normal human oral keratinocytes (HOK) and human gingival fibroblasts (HGF). Moreover, the expression of BubR1 in these four OSCC cell lines was positively correlated with their motility. Immunofluorescence revealed that BubR1 was mostly localized in the cytosol of human gingival carcinoma Ca9-22 cells. BubR1 knockdown significantly decreased cellular invasion but slightly affect cellular proliferation on both Ca9-22 and Cal-27 cells. Consistently, the activities of metastasis-associated metalloproteinases MMP-2 and MMP-9 were attenuated in BubR1 knockdown Ca9-22 cells, suggesting the role of BubR1 in promotion of OSCC migration. Our present study defines an alternative pathway in promoting metastasis of OSCC cells, and the expression of BubR1 could be a prognostic index in OSCC patients.

Clinicopathologic significance of BubR1 and Mad2 overexpression in oral cancer

OBJECTIVES

BubR1 and Mad2 are central components of the mitotic checkpoint complex that inhibits anaphase onset until all chromosomes are correctly aligned at the metaphase plate. We propose to analyse the combined expression of BubR1 and Mad2 and assess its significance to oral squamous cell carcinoma (OSCC) diagnosis and prognosis.

MATERIALS AND METHODS

BubR1 and Mad2 expression was assessed by real-time PCR in OSCC cell lines and in normal human oral keratinocytes, and by immunohistochemistry in 65 patients with OSCC. The results were compared regarding clinicopathological parameters, proliferative activity and survival.

RESULTS

BubR1 and Mad2 transcripts were overexpressed in OSCC cell lines which also exhibited attenuated spindle assembly checkpoint activity. BubR1 and Mad2 were also overexpressed in patients with OSCC. BubR1 expression was associated with advanced stages and larger tumour size in univariate analysis, and with shorter overall survival both in univariate and multivariate analysis. Mad2 overexpression was associated with that of BubR1 and, importantly, high expression of Mad2 and BubR1 was associated with increased cellular proliferation.

CONCLUSION

Our data propose a role for BubR1 and Mad2 in OSCC cellular proliferation, progression and prognosis.

An overview of the spindle assembly checkpoint status in oral cancer

Abnormal chromosome number, or aneuploidy, is a common feature of human solid tumors, including oral cancer. Deregulated spindle assembly checkpoint (SAC) is thought as one of the mechanisms that drive aneuploidy. In normal cells, SAC prevents anaphase onset until all chromosomes are correctly aligned at the metaphase plate thereby ensuring genomic stability. Significantly, the activity of this checkpoint is compromised in many cancers. While mutations are rather rare, many tumors show altered expression levels of SAC components. Genomic alterations such as aneuploidy indicate a high risk of oral cancer and cancer-related mortality, and the molecular basis of these alterations is largely unknown. Yet, our knowledge on the status of SAC components in oral cancer remains sparse. In this review, we address the state of our knowledge regarding the SAC defects and the underlying molecular mechanisms in oral cancer, and discuss their therapeutic relevance, focusing our analysis on the core components of SAC and its target Cdc20.

Survivin and pAkt as potential prognostic markers in squamous cell carcinoma of the head and neck

OBJECTIVE

The purpose of our study was to investigate the expression patterns of cell cycle regulatory proteins and members of the epidermal growth factor receptor (EGFR) signaling pathway in squamous cell carcinoma of the head and neck (HNSCC).

STUDY DESIGN

The expression levels of survivin, Bub1 B (budding uninhibited by benzimidazoles 1 homolog beta), PLK-1 (polo-like kinase 1), Ki-67, cyclin D1, p53, EGFR, pMAPK (phosphorylated mitogen-activated protein kinase), pAkt (phosphorylated protein kinase B), and PTEN (phosphatase and tensin homolog) were studied in a series of 180 tumor samples obtained from HNSCC surgical resections, 50 metastatic lymph node samples, and 72 corresponding noncancerous epithelium samples. Protein expression analysis was performed by immunohistochemical staining. The results were correlated with clinicopathologic features and survival data.

RESULTS

Prognostic significance could be found only for the markers survivin and pAkt. Only the marker combination of cyclin D1 and p53 had positive prognosis potential regarding overall survival.

CONCLUSIONS

Both pAkt and survivin show a positive correlation with distant metastases and may have utility as predictors of long-term outcomes for patients with HNSCC.

BUB1 and BUBR1 inhibition decreases proliferation and colony formation, and enhances radiation sensitivity in pediatric glioblastoma cells

PURPOSE

Glioblastoma (GBM) is a very aggressive and lethal brain tumor with poor prognosis. Despite new treatment strategies, patients' median survival is still lower than 1 year in most cases. The expression of the BUB gene family has demonstrated to be altered in a variety of solid tumors, pointing to a role as putative therapeutic target. The purpose of this study was to determine BUB1, BUB3, and BUBR1 gene expression profiles in glioblastoma and to analyze the effects of BUB1 and BUBR1 inhibition combined or not with Temozolomide and radiation in the pediatric SF188 GBM cell line.

METHODS

For gene expression analysis, 8 cell lines and 18 tumor samples were used. The effect of BUB1 and BUBR1 inhibition was evaluated using siRNA. Apoptosis, cell proliferation, cell cycle kinetics, micronuclei formation, and clonogenic capacity were analyzed after BUB1 and BUBR1 inhibition. Additionally, combinatorial effects of gene inhibition and radiation or Temozolomide (TMZ) treatment were evaluated through proliferation and clonogenic capacity assays.

RESULTS

We report the upregulation of BUB1 and BUBR1 expression and the downregulation of BUB3 in GBM samples and cell lines when compared to white matter samples (p < 0.05). Decreased cell proliferation and colony formation after BUB1 and BUBR1 inhibition were observed, along with increased micronuclei formation. Combinations with TMZ also caused cell cycle arrest and increased apoptosis. Moreover, our results demonstrate that BUB1 and BUBR1 inhibition sensitized SF188 cells to γ-irradiation as shown by decreased growth and abrogation of colony formation capacity.

CONCLUSION

BUB1 and BUBR1 inhibition decreases proliferation and shows radiosensitizing effects on pediatric GBM cells, which could improve treatment strategies for this devastating tumor. Collectively, these findings highlight the potentials of BUB1 and BUBR1 as putative therapeutic targets for glioblastoma treatment.

BUBR1 expression in oral squamous cell carcinoma and its relationship to tumor stage and survival

BACKGROUND

Defects in the mitotic spindle checkpoint have been proposed to contribute to the chromosomal instability observed in human cancers, including oral squamous cell carcinoma (OSCC). BUBR1 is a key component of the spindle checkpoint, whose role in oral carcinogenesis still needs to be clarified.

METHODS

We have analyzed the expression of BUBR1 in 49 cases of OSCC by immunohistochemistry and compared the findings with clinicopathologic parameters, proliferative activity, and DNA ploidy.

RESULTS

BUBR1 was overexpressed in 11 cases (22.4%). Tumors with overexpression of BUBR1 were associated with a less advanced pathologic stage (p = .05) and showed longer survival periods (p = .38) but shorter recurrence-free survival periods (p = .13) than those without it.

CONCLUSIONS

Our data imply the possibility that BUBR1 may be involved in the progression of OSCC, and suggest that BUBR1 may be a promising prognostic marker in patients with OSCC.