Minimal arecaidine concentrations showing a promotion effect during DMBA-induced hamster cheek pouch carcinogenesis

Establishment of an in situ model to explore the tumor immune microenvironment in head and neck squamous cell carcinoma

OBJECTIVE

Establish an in situ model for investigating HNSCC, focusing on tumor growth, metastasis, and the immune microenvironment.

METHODS

Generated a monoclonal SCCVII-ZsGreen cell line through lentiviral transfection. Selected monoclonal lines with growth rates similar to the original SCCVII for in vivo tumorigenesis. Monitored tumor development and metastasis through fluorescence in vivo imaging. Employed immunohistochemistry to assess immune cell distribution in the tumor microenvironment.

RESULTS

SCCVII-ZsGreen exhibited comparable proliferation and in vivo tumorigenicity to SCCVII. In situ tumor formation on day 10, with cervical metastasis in C57BL/6 mice by day 16. No significant fluorescence signals in organs like liver and lungs, while SCCVII-ZsGreen presence confirmed in cervical lymph node metastases. Immunohistochemistry revealed CD4+ T, CD8+ T, B, and dendritic cells distribution, with minimal macrophages.

CONCLUSION

Our model is a valuable tool for studying HNSCC occurrence, metastasis, and immune microenvironment. It allows dynamic observation of tumor development, aids preclinical drug experiments, and facilitates exploration of the tumor immune contexture.

Carcinogenic Effects of Areca Nut and Its Metabolites: A Review of the Experimental Evidence

Oral cancers (OC) are among the most frequent malignancies encountered in Southeast Asia, primarily due to the prevalent habit of betel quid (BQ) and smokeless tobacco use in this region. Areca nut (AN), the primary ingredient in BQ, contains several alkaloids, including arecoline, arecaidine, guvacoline, and guvacine. These have been associated with both the AN abuse liability and carcinogenicity. Additionally, variations in AN alkaloid levels could lead to differences in the addictiveness and carcinogenic potential across various AN-containing products. Recent studies based on animal models and in vitro experiments show cellular and molecular effects induced by AN. These comprise promoting epithelial-mesenchymal transition, autophagy initiation, tissue hypoxia, genotoxicity, cytotoxicity, and cell death. Further, clinical research endorses these undesired harmful effects in humans. Oral submucosal fibrosis, a potentially malignant disease of the oral cavity, is predominantly reported from the geographical areas of the globe where AN is habitually chewed. OC in chronic AN users presents a more aggressive phenotype, such as resistance to anti-cancer drugs. The available evidence on the carcinogenicity of AN based on the findings reported in the recently published experimental studies is discussed in the present review.

The mouse oral carcinoma (MOC) model: A 10-year retrospective on model development and head and neck cancer investigations

Preclinical models of cancer have long been paramount to understanding tumor development and advancing the treatment of cancer. Creating preclinical models that mimic the complexity and heterogeneity of human tumors is a key challenge in the advancement of cancer therapy. About ten years ago, we created the mouse oral carcinoma (MOC) cell line models that were derived from 7, 12-dimethylbenz(a) anthracene (DMBA)-induced mouse oral squamous cell cancers. This model has been used in numerous investigations, including studies on tumor biology and therapeutics. We have seen remarkable progress in cancer immunology in recent years, and these cell lines, which are syngeneic to C57BL/6 background, have also been used to study the anti-tumor immune response. Herein, we aim to review the MOC model from its development and characterization to its use in non-immunological and immunological preclinical head and neck squamous cell carcinoma (HNSCC) studies. Integrating and refining these MOC model studies and extending findings to other systems will provide crucial insights for translational approaches aimed at improving head and neck cancer treatment.

[Development of precancerous lesions of oral mucous membrane diseases and oral cancer animal models]

Precancerous lesions of oral mucous membrane diseases and oral cancer are common diseases in developing countries, especially in South Asia. However, the cancerous mechanism remains unclear, and no efficient treatment and prognosis measure are currently available. Thus, precancerous lesions of the oral mucosa and oral cancer animal models must be identified to further understand their function. In this paper, we systematically review the development of oral mucosal precancerous lesions and oral cancer animal models by referring to related research.

Multifaceted Mechanisms of Areca Nuts in Oral Carcinogenesis: the Molecular Pathology from Precancerous Condition to Malignant Transformation

Oral cancer is one of the most frequent malignant diseases worldwide, and areca nut is a primary carcinogen causing this cancer in Southeast Asia. It has been widely reported that areca nut induced several cytotoxic effects in oral cells, including ROS generation, inflammation, tissue hypoxia, DNA damage, and cell invasion. Recently, through chronic exposure model, more extensive pathological effects due to areca nut have been found. These include the induction of autophagy, promotion of epithelial- mesenchymal transition, and facilitation of cancer stemness conversion. Clinical findings support these adverse effects. Oral submucosal fibrosis, a premalignant condition, is prevalent in the area with habitual chewing of areca nuts. Consistently, oral cancer patients with habitual chewing areca nut exhibit more aggressive phenotypes, including resistance to chemo-radiotherapy. In this review, we comprehensively discuss and concisely summarize the up-to-date molecular and cellular mechanisms by which areca nuts contribute to malignant transformation. This review may provide critical information regarding clinical applications in risk assessment, disease prevention, diagnosis, and personalized therapeutics for areca nut-induced oral malignancy.

The promoting effect of carbamide peroxide teeth bleaching gel in a preclinical model of head and neck cancer in hamster buccal pouch

Objectives

The aim of this study was to verify the promoting effect of carbamide peroxide on dimethylbenzanthracene (DMBA)-induced carcinogenesis in the hamster buccal pouch, in order to reduce the period of latency for tumor formation.

Methods

Sixteen hamsters were randomized into two groups of eight animals each. The hamsters of the group I had their right buccal pouches treated with 0.5% DMBA and 10% carbamide peroxide teeth bleaching gel for 55 days. The animals of the group II had their right pouches treated only with DMBA. After, six animals of each group had their pouches prepared for light microscopy. Histomorphometry was performed to assess the presence of keratinization, nuclear polymorphism, pattern of invasion, number of blood vessels, and inflammatory infiltrate in the tumor front. Furthermore, the newly formed lesions were graded according the Bryne's grading system. The remaining animals had the vascular system of the pouches casted by Mercox and qualitatively analyzed by scanning electron microscopy.

Results

Histopathological analysis of the buccal pouches treated with DMBA and carbamide peroxide exhibited formation of squamous cell carcinoma well-differentiated with a high degree of malignancy in all pouches. The development of this neoplasm was associated with a significant increase in the number of blood vessels, presence of keratin pearls, and inflammatory infiltrate. The pouches of the group II showed inflammation, epithelial hyperplasia, dysplasia, and squamous cell carcinoma in only three right pouches. The analysis of the electron micrographs of the pouches chemically inducted with DBMA and carbamide peroxide reveled formation of a new vascular network characteristic of squamous cell carcinoma.

Conclusion

The protocol presented here, using DMBA associated with carbamide peroxide, shortens the period of latency to produce squamous cell carcinoma in the hamster buccal pouch, decreasing the time and costs of the experiments.

DMBA-induced hamster buccal pouch carcinoma and VX2-induced rabbit cancer as a model for human oral carcinogenesis

In this article, we have described and compared the advantages and disadvantages of two potential animal cancer models (the hamster buccal pouch cancer model and the VX2-induced rabbit cancer model) for human squamous cell carcinomas of the oral mucosa. Currently, no animal cancer model is perfectly applicable to human oral squamous cell carcinomas. This is because the hamster buccal pouch cancer model has a different etiology and genetic constitution compared with human oral carcinomas. In addition, the VX2-induced rabbit cancer model is not produced in situ and, consequently, its natural behavior is totally reliant on the location of transplantation. Nonetheless, with the use of these two animal cancer models together, researchers could evaluate different aspects of the cellular and molecular biological characteristics or assess potential novel treatment regimens for squamous cell carcinomas of the human oral mucosa.

Animal models of cancer in the head and neck region

Animal models that resemble the cancers of the head and neck region are of paramount importance in studying the carcinogenesis of these diseases. Although several methods for modeling cancer in the head and neck are available, none are fully satisfactory. Subcutaneous xenograft models of cancer in nude mice are often used in preclinical studies. However, these models are problematic in several aspects as they lack the specific interactions that exist between the tumor cells and their native environment. Establishment of tumors at the orthotopic sites restore these distinct patterns of interactions between the tumor and the host organs that are lost or altered when the tumors are established in ectopic sites. With regard to the transgenic model of cancer in the head and neck region, it should be kept in mind that the transgene used to drive the malignant transformation may not be representative of the carcinogenic process found in human tumors. Low penetrance of tumor formation also translates into high cost and time commitment in performing studies with transgenic models. In this review, we will discuss some of the commonly used methods for modeling cancer in the head and neck region including squamous cell carcinoma of the head and neck as well as thyroid carcinoma.

Animal models in oral cancer research

Biologically and clinically relevant animal models are essential in investigation of the progression of diseases and the elaboration of diagnostic or therapeutic protocols. The several rodent models used for in vivo evaluation for oral cancer employ chemical, transplantation and genetic (knockout and transgenic) induction methods. These models are described together with their advantages and disadvantages. Their optimization and application in future research may improve the early detection and treatment of oral cancer.

Role of areca nut in betel quid-associated chemical carcinogenesis: current awareness and future perspectives

Betel quid (BQ)-chewing is a popular oral habit with potential links to the occurrence of oral cancer. Many of the literature-based studies reveal that areca nut (AN) extract may demonstrate mutagenic and genotoxic effects, in addition to inducing preneoplastic as well as neoplastic lesions in experimental animals. Areca nut should, thus, be highly suspected as a human carcinogen. Toxicity studies relating to AN-contained polyphenols and tannins are not conclusive, with both carcinogenic and anti-carcinogenic effects being reported. The mutagenicity and genotoxicity of areca alkaloids has been detected by many short-term assays. However, their genotoxicity to oral fibroblasts and keratinocytes, the target cells of BQ, has not been identified. It would thus appear that AN toxicity is not completely due to its polyphenol, tannin and alkaloid content. The single agent which is responsible for AN carcinogenicity awaits further clarification. Reactive oxygen species produced during auto-oxidation of AN polyphenols in the BQ-chewer's saliva, are crucial in the initiation and promotion of oral cancer. Nitrosation of areca alkaloids also produces AN-specific nitrosamines, that have been demonstrated to be mutagenic, genotoxic and are capable of inducing tumors in experimental animals. Arecaidine and AN extract are further suggested to be tumor promoters. Antioxidants such as glutathione and N-acetyl-L-cysteine can potentially prevent such AN-elicited cytotoxicity. Further studies are needed to delineate the metabolism of AN ingredient and their roles in the multi-step chemical carcinogenesis, in order to enhance the success of the future chemoprevention of oral cancer and oral submucous fibrosis.

Cancer induction in the DMBA hamster cheek pouch: a modified technique using a promoter

OBJECTIVE

To evaluate a modified method of carcinogenesis induction using the 9,10-dimethyl-1,2-benzanthracene (DMBA) sustained-release suture technique followed by arecaidine promotion in the hamster cheek pouch model.

STUDY DESIGN

Prospective, controlled animal study.

METHODS

Number 3-0 cotton sutures were impregnated with DMBA and coated with silicone elastomer. These sutures were placed in the cheek pouch of Syrian hamsters in the submucosal space to a length of approximately 1.5 cm. The suture placement was confirmed every 2 weeks and replaced if lost. After 12 weeks, the DMBA-coated sutures were removed. The cheek pouches were everted and painted with a solution of arecaidine three times weekly for up to an additional 4 weeks or until the tumor reached a size of 100 mm2.

RESULTS

We placed sutures in 165 Syrian hamster cheek pouches. Of these, 133 hamsters (80.6%) produced squamous cell carcinomas that reached a size of 100 mm2 and then were randomly selected for treatment in a new drug trial. Twenty-six hamsters (15.8%) were found dead and 6 (3.6%) were killed because of severe inflammation.

CONCLUSIONS

The DMBA hamster cheek pouch model is a reliable and efficient animal model for inducing squamous cell carcinoma and can be used to study upper aerodigestive tract tumors.

Placental glutathione S-transferase isoenzyme expression during promotion of two-stage hamster cheek-pouch carcinogenesis

Glutathione S-transferases (GSTs) are the products of a multigene family. A well-established function of GSTs is to metabolize carcinogens by catalysing the conjugation of electrophilic substrates to glutathione. Whether placental GST (GST-P) is expressed during the promotion of two-stage hamster buccal-pouch mucosa (HBPM) carcinogenesis was investigated here, using 7,12-dimethylbenz[a]anthracene (DMBA) as the initiator and 12-O-tetradecanoylphorbol-13-acetate (TPA) as the promoter. Cytoplasmic and nuclear staining for GST-P was seen in pouches treated with DMBA for 4 or 16 weeks, as well as in those treated with DMBA for 4 weeks and then TPA for 12 weeks. No GST-P positivity was seen in any pouches treated with only TPA or with mineral oil for either 4 or 16 weeks. The average number of GST-P-stained foci in the groups treated with DMBA for 16 weeks (246 +/- 96; mean +/- SD) or DMBA for 4 weeks followed by TPA for 12 weeks (186 +/- 67) was significantly higher than in pouches treated with only DMBA for 4 weeks (97 +/- 24). These results demonstrate that TPA alone is not sufficient for GST-P expression in hamster buccal pouch mucosa. However, after being initiated with DMBA, then promoted with TPA, GST-P activity is induced in hamster buccal pouch mucosa during squamous-cell carcinogenesis. This underpins the suggestion that GST-P may play an important part during the promotion stage of oral carcinogenesis.

Cancer-promoting effect of Taiwan betel quid in hamster buccal pouch carcinogenesis

OBJECTIVE

To investigate the cancer-promoting effect of Taiwan betel quid in hamster buccal pouch carcinogenesis.

MATERIALS AND METHODS

Two hundred and fifty-two non-inbred male adult Syrian golden hamsters were randomly divided into six groups, each containing forty-two animals. A treatment regimen over a 14-week experimental period was employed with six animals per group being killed at seven different periods (every 2 weeks). The right buccal pouch of each animal was painted three times a week with various combinations of 7,12-dimethylbenz[a]anthracene (DMBA), Taiwan betel quid extract, dimethyl sulfoxide (DMSO) and mineral oil.

RESULT

Both the number and size of tumors in animals concurrently treated with DMBA and betel quid were significantly higher than those in animals treated with DMBA alone in each killing period of 8, 10, 12 and 14 weeks. No visible tumors but hyperkeratosis and acanthosis were observed in pouches treated with betel quid alone for all killing periods.

CONCLUSION

Our results indicate Taiwan betel quid may be a co-carcinogen in human oral carcinogenesis, if extrapolation can be made from the current animal study.