Experimental production of lingual carcinomas in hamsters: tumor characteristics and site of formation

Chronic mechanical trauma/irritation and oral carcinoma: A systematic review showing low evidence to support an association

BACKGROUND

Chronic trauma of oral mucosa, resulting from repeated and persistent mechanical irritative action of an intraoral injury agent, has repeatedly been reported to be possibly implicated in the development of oral squamous cell carcinoma (OSCC).

OBJECTIVES

The present systematic review aimed to assess whether chronic mechanical trauma can be considered a risk factor for OSCC.

DATA SOURCES

PubMed, CENTRAL (Cochrane Central Register of Controlled Trials), Scopus; EMBASE, Web of Science.

STUDY ELIGIBILITY CRITERIA

Cohort studies comparing OSCC incidence among subjects with/without chronic mechanical trauma or case-control or cross-sectional studies comparing chronic mechanical trauma among subjects with/without OSCC.

RESULTS

Only one prospective case-control study fulfilled the inclusion criteria, but the quality of the evidence provided is not enough to define trauma as a risk factor for OSCC. The main limitation is the presence of only one case-control study at high risk of bias. In the absence of strong evidence supporting the role of trauma in OSCC, a thorough discussion on trauma and carcinogenesis has been performed.

CONCLUSIONS

Available evidence does not support an active role for chronic trauma in oral carcinogenesis, neither as promoter nor as progressor factor. Prospective cohort studies able to better assess trauma in OSCC are needed.

Effects of low-intensity ultrasound combined with low-dose carboplatin in an orthotopic hamster model of tongue cancer: A preclinical study

Low-intensity ultrasound (LIUS) combined with chemotherapy is an innovative modality for cancer treatment, but its effect on orthotopic carcinoma remains unknown. Our previous study revealed that LIUS enhanced the growth inhibitory effects of several chemotherapeutic drugs in nude mice with transplanted tumors. In the present study, we used 7,12-dimethylbenz(alpha)anthracene to induce orthotopic tongue carcinogenesis in hamsters. We used the first-line chemotherapy drug for tongue cancer, carboplatin (CBP) in combination with LIUS to investigate the synergistic effect. The results revealed that LIUS combined with low-dose CBP enhanced the inhibitory effects of CBP on tumor growth, prolonged survival, and did not increase the incidence of side-effects. It also enhanced the inherent DNA damage caused by CBP, suppressed the expression of the DNA repair proteins O⁶-methylguanine DNA methyltransferase (MGMT) and Chk1, and increased the expression of DNA damage-inducible protein GADD45α. Furthermore, compared with CBP alone, LIUS combined with CBP reduced the expression of cyclin D1 and cyclin B1, induced the expression of caspase-3, cleaved caspase-3, caspase-8, Bax, and Bak, and inhibited the expression of Bcl-2. Examination of clinical samples revealed that MGMT, Chk1, and Gadd45α were higher in OTSCC than in adjacent normal tissue. Hence, our results indicated that LIUS enhanced the ability of low-dose CBP to damage DNA in an orthotopic hamster model of tongue cancer, induced apoptosis, inhibited tumor growth and progression, while it did not increase the toxic side-effects of the drug, suggesting additional clinical benefits for patients treated with the combination of CBP with LIUS.

Effects of propolis on lingual mucosa response of hamsters submitted to experimental carcinogenesis

OBJECTIVE

To assess the tissue reaction of the lingual mucosa in hamsters submitted to daily, alternating, topical applications of 9,10-dimethyl-1,2-benzanthracene (DMBA) and a commercial brand of an ethanol propolis extract (EPE).

METHODS

A total of 60 hamsters were divided into three groups with two experimental periods (13 and 20 weeks). The lateral edge of the tongue was submitted to daily, alternating, topical applications of 0.5% DMBA and 30% EPE (EPE group, n=20), 0.5% of DMBA and aqueous propolis extract (APE group, n=20) and 0.5% of DMBA and saline solution (DMBA group, n=20). The occurrence of clinical and histological alterations was analyzed, along with the measurement of the area and volume of the clinical alterations, the determination of structural and cytological alterations of the squamous epithelial tissue with atypias and the measurement of the histological area of squamous cell carcinomas.

RESULTS

There were no significant differences among groups regarding any of the variables analyzed in the two evaluation periods. At week 13, a single squamous cell carcinoma occurred in the EPE group. At week 20, the greatest occurrence of squamous cell carcinoma was also in the EPE group.

CONCLUSION

The mechanism of EPE (30% alcohol content) affecting the onset of tissue reaction and the promotion of carcinogenesis has not been clarified yet.

Computer-assisted morphometric analysis of lymphatic vessel changes in hamster tongue carcinogenesis

BACKGROUND

To characterize lymphangiogenesis in early-stage hamster tongue carcinoma development, morphological features and spatial relationships of lymphatic vessels.

METHODS

Lymphatic vessels were examined histochemically, using 5'-Nase-ALPase enzyme and combined light and electron microscopy to measure lymphatic vessel area (LVA) and lymphatic vessel density (LVD).

RESULTS

In atypical hyperplastic tissues, LVA was found to be 1429.97 and LVD was found to be 39, in carcinoma in situ LVA was 2538.33 and LVD was 48, and in micro-invasive carcinoma LVA was 5733.74 and LVD was 59. Increased lymphangiogenesis was seen in pre-neoplastic states and in early-stage oral squamous cell carcinoma (OSCC). Small regular lymphatic vessels predominated in atypical hyperplasia, and large, irregular lymphatic vessels in early-stage OSCC. Lymphatic endothelial vessels were stretched and porous over large areas.

CONCLUSIONS

Newly formed lymphatics and patulous intercellular junctions may be optimally suited for tumor cell metastasis through lymphatic channels in early- and middle-phase carcinogenesis. Lymphatic capillary LVA and LVD became enlarged, and positively correlated, with malignancy, but show no correlation with 7,12-dimethylbenz[a]anthracene-induced time.

Experimental epithelial dysplasia produced by excisional wounding and application of Trp-P-2 in the hamster tongue

All 10 groups of hamsters received excision of the tip of tongue. Subsequently, 3 groups in which tongues were treated with Trp-P-2 (3-amino-1-methyl-5H-pyrido[4,3-b] indole) and then again excised in their tips followed by no treatment or by additional applications of DMSO or Trp-P-2, showed moderate to severe epithelial dysplasia. One group in which tongues were not treated and then again excised followed by applications of Trp-P-2, exhibited very slight epithelial dysplasia. However, one group in which tongues were treated with DMSO and then again excised followed by additional applications of DMSO, did not show any pathological changes. The remaining 5 groups in which tongues were treated with DMSO or Trp-P-2 or received no treatment and then not excised followed by no treatment or by additional applications of DMSO or Trp-P-2, also did not show any pathologic changes. These results clearly indicated that Trp-P-2 treatment together with two times of excisional wounding could produce lingual epithelial dysplasia in hamsters.

Epithelial dysplasia produced by carcinogen pretreatment and subsequent wounding

Golden hamsters in which the tongues were pretreated with DMBA for 4 weeks, subsequently excised, and either received no treatment or received additional postexcisional applications of acetone or DMBA for 9 to 13 days exhibited histologic evidence of epithelial dysplasia; these dysplastic lesions stained positive for papillomavirus genus-specific antigens. Conversely, animals in which the tongues received the same pretreatment yet had no excision failed to show any dysplastic changes, even though the tongues received additional applications of DMBA. Furthermore, papillomavirus genus-specific antigens were not demonstrable. The animals in which the tongues received no pretreatment with DMBA for 4 weeks followed by excisional wounding showed normal healing, even though the tongues were post-treated with DMBA. Papillomavirus genus-specific antigens could not be demonstrated in this last group.

Dose-response relationship in complete oral 4NQO-carcinogenesis in rats

Groups of 48 Wistar rats were subjected to thrice-weekly palatal application of the carcinogen 4-nitro-quinoline 1-oxide (4NQO) in propylene glycol 18, 12, 6 or 2 times, each 255 nmol 4NQO, in order to examine the relationship between the dose of the carcinogen and the tumour response. Other groups were treated with solvent alone or were left untreated. When the carcinogen was applied 18 or 12 times, squamous cell or verrucous carcinomas developed in 50% of the rats in 11 and 12 months, respectively, whereas rats subjected to the carcinogen 6 times demonstrated a 50% cancer rate in 23 months. Rats twice exposed to the carcinogen demonstrated a tumour rate of 25% in 30 months. Decreasing doses of 4NQO thus prolonged the latency period and decreased the tumour rate. The tumour development in the animals subjected to two carcinogen applications was significantly different from the tumour development among the solvent-treated animals, indicating that application of 255 nmol may approximate the initiating dose of 4NQO to be used in a two- or multi-stage carcinogenesis protocol. Most of the carcinomas, either squamous cell or verrucous, were located to the hard palate and to the gingival region of the upper jaw. Impaction of hair, bedding material and food was thought to promote the carcinogenic process.

Effect of excisional wounding on DMBA-induced hamster tongue carcinogenesis

The purpose of this study was to investigate histologically the effect of wounding on the hamster tongue after pretreatment with DMBA. The animals in which the tips of the tongues were pretreated with DMBA for 8 weeks, subsequently excised, and had no treatment or received applications of acetone, showed epithelial dysplasias. The animals which had the same pretreatment, excision, and received additional post-excision applications of DMBA for 9-13 days, developed squamous cell carcinomas. However, the animals which were pretreated with DMBA for 8 weeks but had no excision, did not show any pathologic changes, even though they received additional applications of DMBA for 9-13 days. The animals which received no pretreatment with DMBA for 8 weeks but had an excision, showed normal wound healing, even though they had a post-treatment with DMBA for 9-13 days. The results of the present study indicated that excisional wounding acted as a promotional stimulus in inducing the appearance of epithelial dysplasias or carcinomas of tongues initiated with the carcinogen DMBA.

Experimental tongue carcinoma of rats induced by oral administration of 4-nitroquinoline 1-oxide (4NQO) in drinking water

Oral administration of 0.001% 4NQO in drinking water resulted in a high incidence of tongue carcinoma in rats. In other major organs, tumor induction was rarely observed. The most frequent site of tongue carcinoma was the dorsum. No metastases were found. Changes observed included carcinoma in situ and invasive carcinoma. Carcinoma in situ showed erosion, leukoplakia, and a gross papillary appearance. Histologically, most carcinomas in situ showed full-thickness alteration of epithelium. Some carcinomas in situ in papillary lesions showed slightly less than full-thickness alteration of epithelium, exhibiting downward, well-differentiated growth. Invasive carcinomas were either endophytic or exophytic. Histologic grading of invasive carcinoma varied from highly to poorly differentiated. The method described offers a new experimental animal model of tongue carcinoma.

The effect of the short dose schedule of DMBA application in inducing lingual neoplasia in inbred Syrian hamsters

Lingual dysplasia and carcinoma were induced in Lakeview LSH inbred Syrian hamsters by local application of DMBA without the use of trauma in 4 weeks and 6-8 wks, respectively.

Hamster tongue carcinogenesis. I. Characteristics of the experimental model

Thrice weekly applications of DMBA to hamster ventral lingual mucosa, preceded by scratching with a barbed broach, led to tumor development in over 75% of the animals by 28 weeks. Macroscopic ulceration did not appear to be a necessary precursor of epithelial malignancy in this model. Tumors were preceded by a phase resembling human leukoplakia. In addition to developing tumors in the treated area, 60% of the hamsters developed tumors in the floor of the mouth or the area of mucosa on either side of the median lingual frenum.

Animal models of intra-oral chemical carcinogenesis: a review

Early attempts to induce malignant oral tumours were largely unsuccessful, as the oral mucosa is considerably more resistant to the actions of chemical carcinogens than skin. The first consistent success came when strong carcinogens were applied to the hamster cheek pouch. This model remains the most popular for studies of intra-oral carcinogenesis and is discussed at length. The advantages and disadvantages are critically reviewed. The models of intra-oral carcinogenesis in extra-pouch sites in the hamster, mouse, rat and nonhuman primates are considered. The possible reasons for the relative resistance of oral mucosa to chemical carcinogens are discussed, particularly in relation to portals of entry and saliva. Finally, the relative merits of the more popular models of intra-oral carcinogenesis are briefly discussed.

Retinoid inhibition of lingual carcinogenesis

Sixty-four male and female Syrian hamsters, 3 months of age and weighing 90 to 120 grams, were divided into four equal experimental groups. In animals of Groups 1 and 2 the right posterior lateral border of the tongue was painted three times weekly with a 0.5 percent solution of DMBA in acetone. Group 2 animals also received 10 mg. of 13-cis-retinoic acid in peanut oil administered orally twice weekly by pipette. Carcinogen and retinoid were administered on alternate days. Group 3 animals received only 13-cis-retinoic acid. Group 4 animals served as untreated controls. Four animals in each group were killed at 12, 14, 16, and 18 weeks. The Group 2 animals, receiving 13-cis-retinoic acid, exhibited a significant delay in the development of lingual tumors, both grossly and microscopically. At 14 weeks carcinomas were found in the DMBA animals, but only dysplasia and areas of carcinoma in situ were found in the DMBA-retinoid animals. After 18 weeks the DMBA animals exhibited large lingual tumors with surfacenecrosis, while the DMBA-retinoid animals presented smaller tumors with less invasion of underlying tissue.

Lingual carcinogenesis in an inbred strain of hamsters

Epidermoid carcinoma of the lateral border of the tongue can be induced in a standard strain of hamsters, applying DMBA in acetone after traumatizing the area with a root canal broach. Employing the same technique in an inbred strain of hamsters resulted in the more rapid development of carcinomas. The inbred strain should be a useful model for experimental carcinogenesis of tongue.

Effects of the water-soluble carcinogen 4-nitroquinoline N-oxide on hamster lingual mucosa

The water-soluble carcinogen 4-nitroquinoline N-oxide (4NQO) was painted onto hamster ventral lingual mucosa twice weekly for up to 20 weeks. No neoplasms developed during this period. The promoting agent croton oil was applied to the treated areas in an attempt to determine whether initiation had occurred. During the following 6 months, one animal developed a papilloma and three animals showed areas of epithelial atypia in the treated mucosa. No malignant neoplasms were seen. Despite its efficiency in producing intraoral neoplasms in the rat, 4NQO would appear to be a poor choice in the hamster.