Aberrant expression of DUSP4 is a specific phenomenon in betel quid-related oral cancer

A Critical Interpretive Synthesis of the Role of Arecoline in Oral Carcinogenesis: Is the Local Cholinergic Axis a Missing Link in Disease Pathophysiology?

Arecoline is the primary active carcinogen found in areca nut and has been implicated in the pathogenesis of oral squamous cell carcinoma (OSCC) and oral submucous fibrosis (OSF). For this study, we conducted a stepwise review process by combining iterative scoping reviews with a post hoc search, with the aim of identifying the specific mechanisms by which arecoline initiates and promotes oral carcinogenesis. Our initial search allowed us to define the current trends and patterns in the pathophysiology of arecoline-induced OSF and OSCC, which include the induction of cell proliferation, facilitation of invasion, adhesion, and migration, increased collagen deposition and fibrosis, imbalance in immune and inflammatory mechanisms, and genotoxicity. Key molecular pathways comprise the activation of NOTCH1, MYC, PRDX2, WNT, CYR61, EGFR/Pl3K, DDR1 signaling, and cytokine upregulation. Despite providing a comprehensive overview of potential pathogenic mechanisms of OSF, the involvement of molecules functioning as areca alkaloid receptors, namely, the muscarinic and nicotinic acetylcholine receptors (AChRs), was not elucidated with this approach. Accordingly, our search strategy was refined to reflect these evidence gaps. The results of the second round of reviews with the post hoc search highlighted that arecoline binds preferentially to muscarinic AChRs, which have been implicated in cancer. Consistently, AChRs activate the signaling pathways that partially overlap with those described in the context of arecoline-induced carcinogenesis. In summary, we used a theory-driven interpretive review methodology to inform, extend, and supplement the conventional systematic literature assessment workflow. On the one hand, the results of this critical interpretive synthesis highlighted the prevailing trends and enabled the consolidation of data pertaining to the molecular mechanisms involved in arecoline-induced carcinogenesis, and, on the other, brought up knowledge gaps related to the role of the local cholinergic axis in oral carcinogenesis, thus suggesting areas for further investigation.

Low-dose arecoline regulates distinct core signaling pathways in oral submucous fibrosis and oral squamous cell carcinoma

BACKGROUND

Betel nut chewing plays a role in the pathogenesis of oral submucous fibrosis (OSF) and oral squamous cell carcinoma (OSCC). As the major active ingredient of the betel nut, the effect of arecoline and its underlying mechanism to OSF and OSCC pathogenesis remain unclear.

METHODS

Next-generation sequencing-based transcriptome and dRRBS analysis were performed on OSF and OSCC cells under low-dose arecoline exposure. Functional analyses were performed to compare the different roles of arecoline during OSF and OSCC pathogenesis, and key genes were identified.

RESULTS

In this study, we identified that low-dose arecoline promoted cell proliferation of both NFs and OSCC cells via the acceleration of cell cycle progression, while high-dose arecoline was cytotoxic to both NFs and OSCC cells. We performed for the first time the transcriptome and methylome landscapes of NFs and OSCC cells under low-dose arecoline exposure. We found distinct transcriptome and methylome profiles mediated by low-dose arecoline in OSF and OSCC cells, as well as specific genes and signaling pathways associated with metabolic disorders induced by low-dose arecoline exposure. Additionally, low-dose arecoline displayed different functions at different stages, participating in the modulation of the extracellular matrix via Wnt signaling in NFs and epigenetic regulation in OSCC cells. After exposure to low-dose arecoline, the node roles of FMOD in NFs and histone gene clusters in OSCC cells were found. Meanwhile, some key methylated genes induced by arecoline were also identified, like PTPRM and FOXD3 in NFs, SALL3 and IRF8 in OSCC cells, indicating early molecular events mediated by arecoline during OSF and OSCC pathogenesis.

CONCLUSIONS

This study elucidated the contribution of low-dose arecoline to OSF and OSCC pathogenesis and identified key molecular events that could be targeted for further functional studies and their potential as biomarkers.

Systemic and Local Effects Among Patients With Betel Quid-Related Oral Cancer

The major predisposing factors of developing oral cancer include smoking, alcohol drinking, and betel quid chewing. Betel quid chewing could cause the abrasion and damage of oral mucosa by crude fibers, chemical insults by additive slaked lime, and arecoline from areca nut. These would lead to the local consequence of oral submucosal fibrosis, which is regarded clinically as a precancer lesion and a major cause of trismus. In addition, the components and additives in betel quid contain chemical toxins and carcinogens, which would further affect the oral mucosa and gradually develop a malignancy. Following literature review, aside from having a greater total tumor burden and more local diseases in the oral cavity and digestive tract, patients with betel quid-related oral cancer also have more systemic diseases from metabolic syndrome, hypertension, cardiovascular disease, type II diabetes mellitus, and obesity than those without this habit. In conclusion, those patients who have the history of smoking, alcohol drinking, and betel quid chewing would present much more unique clinical characteristics than those who only have a history of smoking and alcohol drinking. More attention should therefore be paid to pretreatment evaluation, treatment strategy, and posttreatment follow-up among betel quid chewers.

Wnt/β-catenin signaling pathway participates in the effect of miR-626 on oral squamous cell carcinoma by targeting RASSF4

BACKGROUND

The role of miR-626 in oral squamous cell carcinoma (OSCC) was investigated by targeting RASSF4.

METHODS

The miR-626 and RASSF4 expression was detected in normal oral mucosa or OSCC tissues and OSCC or normal cells. The methylation status of RASSF4 was analyzed using methylation-specific polymerase chain reaction (PCR). The cytoplasmic/nuclear ratios (C/N ratios) targeted by miR-626 were examined using microarray, followed by a dual-luciferase reporter assay. The subcellular localization of RASSF4 and miR-626 in OSCC cells was determined using RNA fluorescence in situ hybridization (FISH) and immunocytochemistry (ICC), respectively. Ca9-22 and HSC2 cells were divided into mock, inhibitor NC, miR-626 inhibitor, scramble, RASSF4 and miR-626 mimic + RASSF4 groups, and then CCK-8, Annexin V-FITC/PI, wound healing, Transwell, qRT-PCR and western blotting assays were performed.

RESULTS

OSCC tissues and cells had increased miR-626 expression and decreased RASSF4 expression. Patients with RASSF4 methylation had lower RASSF4 expression than those without methylation. In addition, a negative correlation between miR-626 and RASSF4 was found in OSCC tissues, both of which were correlated with the pathological grade, pathological stage, lymph node metastasis and patient prognosis. MiR-626 targeted RASSF4 in OSCC cells. Overexpressed RASSF4 inhibited the proliferation, invasion, migration and epithelial-mesenchymal transition (EMT) of OSCC cells, promoted cell apoptosis, and blocked the Wnt/β-Catenin pathway, which was reversed by miR-626 overexpression.

CONCLUSIONS

Inhibiting miR-626 can regulate the biological characteristics of OSCC cells, including proliferation, invasion, migration, EMT and apoptosis, by targeting RASSF4, which may be related to the Wnt/β-Catenin pathway.

Arecoline induces epithelial-mesenchymal transformation and promotes metastasis of oral cancer by SAA1 expression

Arecoline, the main alkaloid of areca nut, is well known for its role in inducing submucosal fibrosis and oral squamous cell carcinoma (OSCC), however the mechanism remains unclear. The aim of this study was to establish an arecoline‐induced epithelial‐mesenchymal transformation (EMT) model of OSCC cells and to investigate the underlying mechanisms. CAL33 and UM2 cells were induced with arecoline to establish an EMT cell model and perform RNA‐sequence screening. Luminex multiplex cytokine assays, western blot, and RT‐qPCR were used to investigate the EMT mechanism. Arecoline at a concentration of 160 μg/ml was used to induce EMT in OSCC cells, which was confirmed using morphological analysis, transwell assays, and EMT marker detection. RNA‐sequence screening and Luminex multiplex cytokine assays showed that many inflammatory cytokines (such as serum amyloid A1 [SAA1], interleukin [IL]‐6, IL‐36G, chemokine [CCL]2, and CCL20) were significantly altered during arecoline‐induced EMT. Of these cytokines, SAA1 was the most highly upregulated. SAA1 overexpression induced EMT and promoted the migration and invasion of CAL33 cells, while SAA1 knockdown attenuated arecoline‐induced EMT. Moreover, arecoline enhanced cervical lymph node metastasis in an orthotopic xenograft model of the tongue established using BALB/c nude mice. Our findings revealed that arecoline induced EMT and enhanced the metastatic capability of OSCC by the regulation of inflammatory cytokine secretion, especially that of SAA1. Our study provides a basis for understanding the mechanism of OSCC metastasis and suggests possible therapeutic targets to prevent the occurrence and development of OSCC associated with areca nut chewing.