Three cell lines from hamster buccal pouch tumors induced by topical 7,12-dimethylbenz(a)anthracene, alone or in conjunction with herpes simplex virus inoculation

Evaluation of apoptogenic adenovirus type 5 oncolytic vectors in a Syrian hamster head and neck cancer model

Human adenovirus (HAdV) vectors are intensely investigated for virotherapy of a wide variety of human cancers. Here, we have evaluated the effect of two apoptogenic HAdV5 vectors in an immunocompetent Syrian hamster animal model of head and neck cancer. We established two cell lines of hamster cheek pouch squamous cell carcinomas, induced by treatment with 9, 10-dimethyl-1, 2-benzanthracene (DMBA). These cell lines, when infected with HAdV5 mutants lp11w and lp11w/Δ55K (which are defective in the expression of either E1B-19K alone or both E1B-19K and E1B-55K proteins) exhibited enhanced apoptotic and cytotoxic responses. The cheek pouch tumor cells transplanted either subcutaneously at the flanks or in the cheek pouches of hamsters readily formed tumors. Intra-tumoral administration of HAdV5 E1B mutants efficiently suppressed the growth of tumors at both sites. Histological examination of orthotopic tumors revealed reduced vascularity and the expression of the viral fiber antigen in virus-administered cheek pouch tumors. These tumors also exhibited increased caspase-3 levels, suggesting virus-induced apoptosis may contribute to tumor growth suppression. Our results suggest that the apoptogenic HAdV5 vectors may have utility for the treatment of human head and neck cancers.

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.

Potential biomarkers for head and neck squamous cell carcinoma

OBJECTIVE

The purpose of the study was twofold: 1) to search for potential biomarkers that were overexpressed in cell lines that could represent both a clinical premalignant (immortalized) and a malignant state, and 2) to attempt to correlate metallothionein gene expression with clinical outcome in laryngeal carcinoma.

STUDY DESIGN

A series of in vitro experiments were used to unearth differentially expressed genes among normal, immortalized and tumorigenic cell lines. Secondarily, a retrospective analysis was undertaken.

METHODS

Differential display analysis was conducted to identify differentially expressed genes between human papillomavirus-infected immortalized HOK16B and benzo[ ]pyrene-derived tumorigenic cell line, HOK16B-BaP-T. The cell-specific expressions were examined by Northern blot analysis and compared with other known immortalized and cancer cell lines. Immunohistochemical staining was also conducted to localize metallothionein (MT I/II) protein expression among the different cell lines studied. A retrospective analysis of laryngeal specimens from archival tissues of 29 cancer patients who underwent primary surgical resection was also undertaken after immunohistochemical staining.

RESULTS

Twenty-one differentially expressed complementary cDNA clones, both novel and known, were identified using the differential display analysis. Northern blot analysis confirmed that clone 6 hybridized to a 1.6-kb RNA in HOK16B-Bap-T cell line. Clone 4 showed decreased expression in immortalized and cancer cell compared with NHOK. MT I/II transcript was observed in HOK16B, which was further elevated in HOK16B-Bap-T. Retrospective analysis showed that high immunoreactivity to MT I/II in surgically resected laryngeal cancer specimen correlated with increased frequency of recurrence within 2 years of surgery.

CONCLUSION

These findings suggest that clone 4 may potentially function as a tumor suppressor gene, which may be significant in tumor progression and invasion. Clone 6 may participate in viral-mediated oncogenic transformation of normal cells. Clone 6 may also have potential as a tumor maker differentiating normal from malignant tissue, as in the determination of surgical resection margins. MT I/II gene product may serve as a prognostic biomarker for laryngeal squamous cell carcinoma. The differentially expressed genes and gene products may serve as sensitive biomarkers for improved early detection, diagnosis, and prognosis of head and neck squamous cell carcinoma.

Cell, tissue and organ culture as in vitro models to study the biology of squamous cell carcinomas of the head and neck

In vitro models are currently being used to study head and neck squamous cell carcinoma (HNSCC). Several hundred HNSCC cell lines have been established by various investigators and used to study a broad spectrum of questions related to head and neck cancer. The head and neck model with respect to multistage carcinogenesis is now complete. Several techniques exist for the culture of normal epithelial cells from the upper aerodigestive tract (UADT). The biology of these UADT cells (oral cavity, oropharynx, hypopharynx and larynx) is being studied. Successful culture of premalignant lesions (dysplastic mucosa, leukoplakia, erythroplakia) has resulted in establishment of a limited number of premalignant cell lines and cell cultures. HPV infection of normal oral epithelial cells for immortalization (approximately premalignant cells) coupled with transformation with carcinogens (malignant cells) has established an experimental model for progression. Two in vivo models for oral carcinogenesis, the 7,12 dimethylbenz(a)anthracene-induced hamster cheek pouch model and the 4-nitroquinoline-N-oxide rat oral model, have been established in culture. Thus, multistage carcinogenesis models have been established from both human tissues and animal models and include cultures of normal, premalignant and malignant cells. Culture techniques for growing dissociated primary tumor cells for short term experimental analysis are being used. The culture of normal or tumor tissue as organ/explant cultures allows for the maintenance of normal cell-cell and cell-matrix interaction, but limits experimentation since these cultures cannot be propagated. Several three dimensional model systems are being used to obtain this histological complexity but allow for experimentation. The ability to culture normal, premalignant and malignant cells coupled with the use of a variety of culture techniques, should allow for the continued growth and experimentation in head and neck cancer research.