Hamster Oral Cancer Model Research Articles

Different oral cancer scenarios to personalize targeted therapy: Boron Neutron Capture Therapy translational studies.

Boron neutron capture therapy (BNCT) is a targeted therapy, which consists of preferential accumulation of boron carriers in tumor followed by neutron irradiation. Each oral cancer patient has different risks of developing one or more carcinomas and/or oral mucositis induced after treatment. Our group proposed the hamster oral cancer model to study the efficacy of BNCT and associated mucositis. Translational studies are essential to the advancement of novel boron delivery agents and targeted strategies. Herein, we review our work in the hamster model in which we studied BNCT induced mucositis using three different cancerization protocols, mimicking three different clinical scenarios. The BNCT-induced mucositis increases with the aggressiveness of the carcinogenesis protocol employed, suggesting that the study of different oral cancer patient scenarios would help to develop personalized therapies.

Low dietary n-6/n-3 polyunsaturated fatty acid ratio prevents induced oral carcinoma in a hamster pouch model

Dietary fatty acid patterns have been linked to the prevalence of certain cancers, however in oral carcinoma is limited. Thus, we investigated the chemopreventive effects of various dietary n-6 and n-3 fatty acids in a 9,10-dimethyl-1,2-benz[a]-anthracene (DMBA)- and betel quid extract (BQE) -induced hamster oral cancer model. Thirty 6-week-old adult male hamsters were housed and divided into normal, low, and high dietary n-6 and n-3 fatty acid groups under DMBA + BQE treatment for 16 weeks. The right buccal pouch of all hamsters were evaluated by tumor number, volume, burden and selected inflammatory parameters. The results indicate that the low dietary n-6/n-3 fatty acid group exhibited a significantly lower tumor number, volume, and burden than those of the other groups. Furthermore, this group had significantly lower nuclear factor-κB, proliferating cell nuclear antigen, and cyclin D1 expression in the right buccal pouch tissue. In conclusion, the lower dietary n-6/n-3 fatty acid ratio exerted chemopreventive effects in the DMBA- and BQE-induced hamster oral cancer model.

Luminescent lanthanide chelate contrast agents and detection of lesions in the hamster oral cancer model.

Lanthanide chelates are a somewhat unique class of molecules that have proven to be useful in the biomedical field due to their extremely large Stokes' shift and long fluorescent lifetimes. The ability of these molecules to produce fluorescence in the low- or zero-back-ground regime makes this class of molecules excellent candidates for use as contrast agents for a wide variety of applications in biological settings. Here we present the preparation, spectroscopic characterization, and application of a new terbium chelate contrast agent, based on the 1,4,7,10-tetraazacyclododecane macrocycle (cyclen), for detection of early-stage malignant lesions in the Syrian hamster cheek pouch. Tb-P(CTMB) delivers bright blue-green luminescence when excited with low photon fluxes of UV light. As a pilot study, the DMBA-treated Golden Hamster Cheek pouch epithelial cancer model was employed and Tb-P(CTMB) was used as a topical agent for the visual detection of diseased tissue. In this preliminary study the agent tended to associate with early-stage malignant lesions, suggesting that Tb-P(CTMB) could be used as a contrast agent to aid in identifying early-stage oral cancer lesions.

Biodistribution of a carborane-containing porphyrin as a targeting agent for Boron Neutron Capture Therapy of oral cancer in the hamster cheek pouch

Boron Neutron Capture Therapy (BNCT) is a bimodal cancer treatment based on the selective accumulation of 10 B in tumors and concurrent irradiation with thermalized neutrons. The short-range, high-LET radiation produced by the capture of neutrons by 10 B could potentially control tumor while sparing normal tissue if the boron compound targets tumor selectively within the treatment volume. In previous studies, we proposed and validated the hamster cheek pouch model of oral cancer for BNCT studies, proved that absolute and relative uptake of the clinically employed boron compound boronophenylalanine (BPA) would be potentially therapeutic in this model and provided evidence of the efficacy of in vivo BPA-mediated BNCT to control hamster oral mucosa tumors with virtually no damage to normal tissue. We herein present the biodistribution and pharmacokinetics of a lipophilic, carborane-containing tetraphenylporphyrin (CuTCPH) in the hamster oral cancer model. CuTCPH is a novel, non-toxic compound that may be advantageous in terms of selective and absolute delivery of boron to tumor tissues. For potentially effective BNCT, tumor boron concentrations from a new agent should be greater than 30 ppm and tumor/blood and tumor/normal tissue boron concentration ratios should be greater than 5/1 without causing significant toxicity. We administered CuTCPH intraperitoneally (i.p.) as a single dose of 32 μg/g body weight (b.w.) (10 μg B/g b.w.) or as four doses of 32 μg/g b.w. over 2 days. Blood (Bl) and tissues were sampled at 3, 6, 12, 24, 48, and 72 h in the single-dose protocol and at 1–4 days after the last injection in the multidose protocol. The tissues sampled were tumor (T), precancerous tissue surrounding tumor, normal pouch (N), skin, tongue, cheek and palate mucosa, liver, spleen, parotid gland and brain. The maximum mean B ratios for the single-dose protocol were T/N: 9.2/1 (12 h) and T/Bl: 18.1/1 (72 h). The B value peaked to 20.7±18.5 ppm in tumor at 24 h. The multidose protocol maximum mean ratios were T/N: 11.9/1 (3 days) and T/Bl: 235/1 (4 days). Absolute boron concentration in tumor reached a maximum value of 116 ppm and a mean value of 71.5±48.3 ppm at 3 days. The fact that absolute and relative B values markedly exceeded the BNCT therapeutic threshold with no apparent toxicity may confer on this compound a therapeutic advantage. CuTCPH-mediated BNCT would be potentially useful for the treatment of oral cancer in an experimental model.

Eosinophil ablation and tumor development.

Tissue eosinophilia in squamous cell carcinoma has long been recognized; however, the role of eosinophils in tumor development remains unclear. Studies have reported both favorable and unfavorable prognoses for patients with tumors exhibiting tumor-associated tissue eosinophilia (TATE). This study seeks to elucidate the potential role of the eosinophil in squamous cell carcinoma development and provide an experimental model for future studies. The carcinogen-induced hamster oral cancer model was found to fulfill these objectives. Eosinophils progressively infiltrate into this carcinogen-induced oral cancer model. We now demonstrate that TATE is completely abolished by the use of an anti-interleukin-5 monoclonal antibody (mAb) preparation, TRFK-5. Clinical observations revealed that TRFK-5-treated hamsters exhibited smaller tumor burden and delayed onset of tumor development. The results suggest that anti-interleukin-5 antibody treatment may delay and/or inhibit tumor development, and that eosinophils may have a tumor-promoting role.

Cloning, Mapping, Expression, Function, and Mutation Analyses of the Human Ortholog of the Hamster Putative Tumor Suppressor Gene doc-1

doc-1 is a putative tumor suppressor gene isolated and identified from the hamster oral cancer model. Here, we report the molecular cloning and the functional characterization of the human ortholog of the hamster doc-1 gene. Human doc-1 cDNA is 1.6 kilobase pairs in length and encodes for a 115-amino acid polypeptide (12.4 kDa, pI 9. 53). Sequence analysis showed 98% identity between human and hamster doc-1 protein sequences. DOC-1 is expressed in all normal human tissues examined. In oral keratinocytes, expression of DOC-1 is restricted to normal oral keratinocytes. By immunostaining of normal human mucosa, DOC-1 is detected in both the cytoplasm and nuclei of basal oral keratinocytes; while in suprabasilar cells, it is primarily found in the nuclei. Human oral cancers in vivo did not exhibit immunostaining for DOC-1. Like murine DOC-1, human DOC-1 associates with DNA polymerase alpha/primase and mediates the phosphorylation of the large p180 catalytic subunit, suggesting it may be a potential regulator of DNA replication in the S phase of the cell cycle. Using a human doc-1 cosmid as a probe, human doc-1 is mapped to chromosome 12q24. We identified four exons in the entire human doc-1 gene and determined the intron-exon boundaries. By polymerase chain reaction and direct sequencing, we examined premalignant oral lesion and oral cancer cell lines and found no intragenic mutations.

Sequential cytogenetic alterations in hamster oral keratinocytes during DMBA-induced oral carcinogenesis.

Using the hamster cheek pouch oral cancer model, we have performed a comprehensive analysis of the cytogenetic changes in hamster oral keratinocytes during 7,12-dimethylbenz[a]anthracene (DMBA)-induced carcinogenesis. Tumour induction in the hamster cheek pouch required repeated application of the carcinogen for 14 weeks. We have found that this hamster oral cancer model to be suitable for cytogenetic studies. Unlike human oral cancers where chromosome breaks have been shown, this is only infrequently observed in DMBA-treated hamster oral keratinocytes. Of importance is the finding that at the beginning of the second week of DMBA treatment, there is a significant increase of karyotypes demonstrating tetraploid or near-tetraploidy. We propose that the significant increase in hamster oral keratinocytes exhibiting tetraploidy be further evaluated as a marker of premalignancy/malignancy.

TGF-alpha and oral carcinogenesis.

Transforming growth factor-alpha (TGF-alpha) has been shown to be consistently expressed by tumours of epithelial origin, particularly squamous and renal carcinomas. Epithelial tumours are often found to concurrently express the receptor to TGF-alpha, namely epidermal growth factor receptor (EGFR), at elevated levels. The simultaneous expression of TGF-alpha and EGFR by the carcinoma cells is thought to trigger the autocrine growth pathway, resulting in uncontrolled proliferation. Similar observations of elevated TGF-alpha/EGFR expression have been detected in oral squamous carcinomas from human and animal sources. By RNA blotting analyses, elevated levels of TGF-alpha/EGFR expression have been consistently observed with malignant human and hamster oral cancers. Interestingly, by use of cellular localisation techniques of in situ hybridisation and immunohistochemistry, we have shown that there is another, previously unnoticed, cellular source of TGF-alpha at oral tumour sites. Eosinophils are a major cellular source of this growth factor in oral cancer and their presence is tightly associated with malignant oral epithelium. Furthermore, transformed oral epithelium in vivo has been shown to be associated with elevated levels of EGFR expression. Thus quantitative changes in TGF-alpha and EGFR levels in the microenvironment of oral tumours have been observed in vivo. With the hamster oral cancer model, the stage is therefore set to elucidate the cellular and molecular contributions of TGF-alpha and EGFR in the process of oral cancer development.

TGF-alpha and EGF-receptor mRNAs in human oral cancers.

Transforming growth factor alpha (TGF-alpha) and epidermal growth factor receptor (EGFR) have been shown to be present in most squamous cell carcinomas. Using the Syrian hamster oral cancer model, we have recently demonstrated the consistent presence of TGF-alpha and EGFR mRNAs in chemically transformed hamster oral keratinocytes. We now present evidence that in human oral cancer (in vivo and in vitro), TGF-alpha and EGFR mRNAs can also be consistently detected. No TGF-alpha mRNA can be detected in normal human oral epithelium by Northern blot analysis. These findings reinforce the use of the hamster cheek pouch as an experimental model for the study of oral cancer development, at least in reference to the possible participation of TGF-alpha in the malignant transformation process.