Evaluation of Mast Cells in Oral Potentially Malignant Disorders and Oral Squamous Cell Carcinoma

Comparison of Mast Cell Count in Oral Epithelial Dysplasia and Squamous Cell Carcinoma

Statement of the Problem

Squamous cell carcinomas (SCCs) and premalignant disorders such as leukoplakia are common oral cavity lesions. Although these lesions are epithelial in nature, they are also associated with juxta-epithelial chronic inflammation. Mast cells play a significant role in inflammation initiation and propagation.

Purpose

Previous studies have yielded conflicting results in this field. Therefore, this research aimed to assess the number of mast cells in oral SCC and dysplastic leukoplakia and explore their possible role in these lesions.

Materials and Method

In this retrospective cross-sectional study, sixty-three archival cases, including 22 OSCCs, 28 dysplastic leukoplakias as epithelial dysplasia (ED), and 13 normal oral mucosal tissues, were examined for mast cells, using toluidine blue staining. Hotspot areas were identified at 10× magnification and mast cells were counted in 5 fields at 40× magnification. The average cell numbers were calculated, and the severity of inflammation was scored. Statistical analysis was performed using SPSS statistical software 20, including One-way ANOVA, Two-way ANOVA, paired-t test, and independent t-test. p Value < 0.05 was considered significant.

Results

Among the 51 pathologic lesions, 54.9% were males and 45.1% were females, with a mean age of 56.34±15.35 years. The most common locations were the tongue and buccal mucosa. The mast cell count was significantly lower in SCC compared to ED (p= 0.009). There was no correlation between mast cell count and inflammation score (p= 0.345).

Conclusion

In this study, the mast cell count was higher in ED compared to OSCC, suggesting an increase in these cells during the pre-malignant stages. However, the number of mast cells decreased after connective tissue invasion and microenvironmental changes occurred.

Role of mast cells in the pathogenesis of oral submucous fibrosis: a systematic review and meta-analysis

BACKGROUND

Oral Submucous Fibrosis (OSMF) is an oral potentially malignant disorder (OPMD) that commonly occurs in the South Asian population as there is high usage of areca nut. There has been extensive research on the pathogenesis and treatment of this condition. It is well-established in the scientific literature that mast cells (MC) have a definitive role in several inflammatory disorders. OSMF being a chronic inflammatory disorder, is also expected to have increased MCs. Hence, this review aims to evaluate the role of MCs in the pathogenesis of OSMF.

METHODS

A systematic search of articles was performed by two of the authors independently in PubMed, Scopus, Embase, Web of Science, and Google Scholar using the appropriate keywords and Boolean terms. The risk of bias was assessed using the Modified Newcastle-Ottawa Scale. The meta-analysis was performed with R studio software (Version: 4.4.0, Year: 2024, Company: The R foundation for statistical computing).

RESULTS

The search retrieved 36 studies, of which 16 were suitable for the review. There is evidence for a marked increase in the number of MCs in OSMF than the normal mucosa upon analyzing the retrieved articles. However, when comparing the grades of OSMF, there are variations in the reports. As all the retrieved articles were case-control studies, the risk of bias was analyzed using the Modified New Castle Ottawa Scale. All the studies scored in the good category (Score 6-9). The pooled effect size shows the Standard Mean Deviation (SMD) to be 0.09, 95% confidence interval (CI) [-0.18;0.37] to lie on either side of no effect. Hence the role of MCs in OSMF has not been established because of homogeneity and consistent sampling error.

CONCLUSION

Our systematic review does suggest a definitive role of mast cells in the progression of OSMF. However, there is a lack of methodological rigor in the included studies. This may contribute to diluting the results.

miR-504 knockout regulates tumor cell proliferation and immune cell infiltration to accelerate oral cancer development

miR-504 plays a pivotal role in the progression of oral cancer. However, the underlying mechanism remains elusive in vivo. Here, we find that miR-504 is significantly down-regulated in oral cancer patients. We generate miR-504 knockout mice (miR-504-/-) using CRISPR/Cas9 technology to investigate its impact on the malignant progression of oral cancer under exposure to 4-Nitroquinoline N-oxide (4NQO). We show that the deletion of miR-504 does not affect phenotypic characteristics, body weight, reproductive performance, and survival in mice, but results in changes in the blood physiological and biochemical indexes of the mice. Moreover, with 4NQO treatment, miR-504-/- mice exhibit more pronounced pathological changes characteristic of oral cancer. RNA sequencing shows that the differentially expressed genes observed in samples from miR-504-/- mice with oral cancer are involved in regulating cell metabolism, cytokine activation, and lipid metabolism-related pathways. Additionally, these differentially expressed genes are significantly enriched in lipid metabolism pathways that influence immune cell infiltration within the tumor microenvironment, thereby accelerating tumor development progression. Collectively, our results suggest that knockout of miR-504 accelerates malignant progression in 4NQO-induced oral cancer by regulating tumor cell proliferation and lipid metabolism, affecting immune cell infiltration.

Verification of the expression trend and interaction prediction of innate immune cells and immune-checkpoint molecules in the process of oral mucosal carcinogenesis

OBJECTIVES

This study aimed to explore the expression trends of innate immune cells and immune-checkpoint molecules validated by data calculation in the process of oral mucosal carcinogenesis, as well as to explore methods of suppressing oral mucosal carcinogenesis based on immunotherapy by predicting their interactions. Me-thods 1) The cancer genome atlas (TCGA) database comprehensively scores immune cells and immune-checkpoint molecules in the process of oral mucosal carcinogenesis and screens out intrinsic immune cells and immune-checkpoint molecules that interfere with tumor immune escape. 2) Clinical patient blood routine data were collected for the statistical analysis of peripheral blood immune cells during the progression of oral mucosal carcinogenesis. Immune cells in peripheral blood that may affect the progression of oral mucosal carcinogenesis were screened. 3) Immunohistochemical staining was performed on intrinsic immune cells and immune-checkpoint molecules validated based on data calculation in various stages of oral mucosal carcinogenesis. 4) Special staining was used to identify innate immune cells in various stages of oral mucosal carcinogenesis based on data-calculation verification. 5) Survival analysis was conducted on intrinsic immune cells and immune-checkpoint molecules validated based on data calculation during the process of oral mucosal carcinogenesis. The association of intrinsic immune cells and immune-checkpoint molecules with the prognosis of oral squamous cell carcinoma was verified.

RESULTS

The expression of monocytes and neutrophils increased during the process of oral mucosal carcinogenesis. The expression of eosinophils showed a single peak trend of up and down. The expression of mast cells decreased. In the process of oral mucosal carcinogenesis, the expression of the immune-checkpoint molecules cytotoxic T-lymphocyte-associated protein 4 (CTLA4) and programmed cell death-ligand (PD-L1) increased. The expression trends of monocytes, neutrophils, and eosinophils were positively correlated with those of CTLA4 and PD-L1 immune-checkpoint molecules. The expression trend of mast cells was negatively correlated with the expression of CTLA4 and PD-L1. Monocytes, neutrophils, and eosinophils may promote tumor immune escape mediated by CTLA4 and/or PD-L1, thereby accelerating the progression of oral mucosal carcinogenesis. Mast cells may inhibit tumor immune escape mediated by CTLA4 and/or PD-L1, delaying the progression of oral mucosal carcinogenesis.

CONCLUSIONS

Therefore, interference with specific immune cells in innate immunity can regulate the expression of CTLA4 and/or PD-L1 to a certain extent, inhibit tumor immune escape, and delay the progression of oral mucosal carcinogenesis.

The Distinctive Features behind the Aggressiveness of Oral and Cutaneous Squamous Cell Carcinomas

Squamous cell carcinomas arise from stratified squamous epithelia. Here, a comparative analysis based on recent studies defining the genetic alterations and composition of the stroma of oral and cutaneous squamous cell carcinomas (OSCC and CSCC, respectively) was performed. Both carcinomas share some but not all histological and genetic features. This review was focused on how mutations in tumor suppressor genes and protooncogenes cooperate to determine the differentiation, aggressiveness, and metastatic potential of OSCC and CSCC. In fact, driver mutations in tumor suppressor genes are more frequently observed in OSCC than CSCC. These include mutations in TP53 (encoding pP53 protein), CDKN2A (encoding cyclin dependent kinase inhibitor 2A), FAT1 (encoding FAT atypical cadherin 1), and KMT2D (encoding lysine methyltransferase 2D), with the exception of NOTCH (encoding Notch receptor 1), whose mutation frequency is lower in OSCC compared to CSCC. Finally, we describe the differential composition of the tumor microenvironment and how this influences the aggressiveness of each tumor type. Although both OSCC and CSCC tumors are highly infiltrated by immune cells, high levels of tumor-infiltrating lymphocytes (TILs) have been more frequently reported as predictors of better outcomes in OSCC than CSCC. In conclusion, OSCC and CSCC partially share genetic alterations and possess different causal factors triggering their development. The tumor microenvironment plays a key role determining the outcome of the disease.

The Immunolocalization of Mast Cells in the Pathology of Oral Submucous Fibrosis

Background Oral submucous fibrosis (OSMF) is a prevalent precancerous condition of the oral cavity and an ambiguity to clinicians because of its indistinguishable etiopathogenesis. Previous studies could not establish a definite role of mast cells (MCs) in the fibrosis of stroma. The present study was done to study the histopathological changes in OSMF and to determine the association of mast cells (MCs) and their degranulated components with vascularity. Methods A retrospective case-control study involved 40 cases of various histopathological grades of OSMF and was compared with 10 cases of normal buccal mucosa by using a cluster of differentiation 117 (CD117) kit for the identification of MCs and Masson's trichrome stain to study the number of blood vessels (BVs). Results The present study indicated that advanced cases of OSMF had keratinized epithelium with atrophic changes and moderate to advanced fibrosis of stroma with the involvement of underlying muscles. The MC density and the number of blood vessels were progressively reduced in OSMF as the grade advanced compared to healthy controls. Conclusion An increase in the mast cell density in the initial stages of OSMF suggests their definite role in the initiation of fibrosis and secondary changes to the epithelium such as atrophy.

Is CCL2 an Important Mediator of Mast Cell-Tumor Cell Interactions in Oral Squamous Cell Carcinoma?

In this study, we aimed to evaluate the influence of interactions between mast cells (MCs) and oral squamous cell carcinoma (OSCC) tumor cells on tumor proliferation and invasion rates and identify soluble factors mediating this crosstalk. To this end, MC/OSCC interactions were characterized using the human MC cell line LUVA and the human OSCC cell line PCI-13. The influence of an MC-conditioned (MCM) medium and MC/OSCC co-cultures on the proliferative and invasive properties of the tumor cells was investigated, and the most interesting soluble factors were identified by multiplex ELISA analysis. LUVA/PCI-13 co-cultures increased tumor cell proliferation significantly (p = 0.0164). MCM reduced PCI-13 cell invasion significantly (p = 0.0010). CC chemokine ligand 2 (CCL2) secretion could be detected in PCI-13 monocultures and be significantly (p = 0.0161) increased by LUVA/PCI-13 co-cultures. In summary, the MC/OSCC interaction influences tumor cell characteristics, and CCL2 could be identified as a possible mediator.

Combined impacts of histamine receptor H1 gene polymorphisms and an environmental carcinogen on the susceptibility to and progression of oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most frequently encountered type of oral cancer. Histamine receptor H1 (HRH1) was reported to play a crucial role in OSCC carcinogenesis, but impacts of genetic variants of HRH1 on OSCC remain unclear. Herein, we investigated the association between functional single-nucleotide polymorphisms (SNPs) of HRH1 and OSCC susceptibility or clinicopathologic variables by logistic regression models. HRH1 genotypes at four loci (rs346074, rs346076, rs901865, and rs2606731) were analyzed by a TaqMan allelic discrimination assay, and we found that patients harboring HRH1 rs901865 T and rs346074 T alleles had a significantly lower risk of developing larger tumor sizes (>T2) under a dominant model. Based on the environmental carcinogen exposure status, we observed that HRH1 rs901865 polymorphic variants were also associated with a lower risk of developing more-advanced clinical stages (III or IV) in patients with a betel-quid-chewing habit. Moreover, genotype screening of rs901865 and rs346074 in OSCC cell lines showed that cells respectively carrying the CT and TT genotypes expressed lower HRH1 levels compared to cells carrying the CC genotype of rs901865 and rs346074. Furthermore, analyses of TCGA and GEO databases revealed that HRH1 expression levels were upregulated in head and neck squamous cell carcinoma (HNSCC) and OSCC tissues compared to normal tissues and were correlated with larger tumor sizes and poorer prognoses. These results indicated the involvement of HRH1 SNPs rs901865 and rs346074 in OSCC development and support the interaction between HRH1 gene polymorphisms and an environmental carcinogen as a predisposing factor for OSCC progression.