Effect of excisional wounding on DMBA-induced hamster tongue carcinogenesis

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.

A personalized computational model predicts cancer risk level of oral potentially malignant disorders and its web application for promotion of non-invasive screening

BACKGROUND

Despite their high accuracy to recognize oral potentially malignant disorders (OPMDs) with cancer risk, non-invasive oral assays are poor in discerning whether the risk is high or low. However, it is critical to identify the risk levels, since high-risk patients need active intervention, while low-risk ones simply need to be follow-up. This study aimed at developing a personalized computational model to predict cancer risk level of OPMDs and explore its potential web application in OPMDs screening.

METHODS

Each enrolled patient was subjected to the following procedure: personal information collection, non-invasive oral examination, oral tissue biopsy and histopathological analysis, treatment, and follow-up. Patients were randomly divided into a training set (N = 159) and a test set (N = 107). Random forest was used to establish classification models. A baseline model (model-B) and a personalized model (model-P) were created. The former used the non-invasive scores only, while the latter was incremented with appropriate personal features.

RESULTS

We compared the respective performance of cancer risk level prediction by model-B, model-P, and clinical experts. Our data suggested that all three have a similar level of specificity around 90%. In contrast, the sensitivity of model-P is beyond 80% and superior to the other two. The improvement of sensitivity by model-P reduced the misclassification of high-risk patients as low-risk ones. We deployed model-P in web.opmd-risk.com, which can be freely and conveniently accessed.

CONCLUSION

We have proposed a novel machine-learning model for precise and cost-effective OPMDs screening, which integrates clinical examinations, machine learning, and information technology.

The modulatory effect of cell–cell contact on the tumourigenic potential of pre-malignant epithelial cells: a computational exploration

Malignant development cannot be attributed alone to genetic changes in a single cell, but occurs as a result of the complex interplay between the failure of cellular regulation mechanisms and the presence of a permissive microenvironment. Although E-cadherin is classified as a 'metastasis suppressor' owing to its role in intercellular adhesion, the observation that it may be downregulated at a premalignant stage is indicative of additional roles in neoplastic development. We have used an agent-based computational model to explore the emergent behaviour resulting from the interaction of single and subpopulations of E-cadherin-compromised cells with unaffected normal epithelial cells within a monolayer environment. We have extended this to investigate the importance of local tissue perturbations in the form of scratch-wounding, or ablation of randomly-dispersed normal cells, on the growth of a single cell exhibiting E-cadherin loss. Our results suggest that the microenvironment with respect to localized cell density and normal/E-cadherin-compromised neighbours is crucial in determining whether an abnormal individual cell proliferates or remains dormant within the monolayer. These predictions raise important questions relating to the propensity for individual mutations to give rise to disease, and future experimental exploration of these will enhance our understanding of a complex, multifactorial pathological process.

Evaluation of high-performance liquid chromatography laser-induced fluorescence for serum protein profiling for early diagnosis of oral cancer

The present work deals with the evaluation of a high-performance liquid chromatography laser-induced fluorescence (HPLC-LIF) technique developed in our laboratory for early detection of oral cancer from protein profiles of body fluids. The results show that protein profiles of serum samples from a given class of samples, say, normal, premalignant, or malignant, are statistically very close to each other, while profiles of members of any class are significantly different from other classes. The performance of the technique is evaluated by the use of sensitivity and specificity pairs, receiver operating characteristic (ROC) analysis, and Youden's Index. The technique uses protein profile differences in serum samples, registered by the HPLC-LIF technique. The study is carried out using serum samples from volunteers diagnosed as normal or premalignant clinically, and as malignant by histopathology. The specificities and sensitivities of the HPLC-LIF method at an ideal threshold (M-distance = 2) for normal, malignant, and premalignant classes are 100, 69.5, and 61.5%, and 86.5, 87.5, and 87.5% respectively.

Morphological changes in the lingual papillae and their connective tissue cores on the 7,12-dimethylbenz[alpha]anthracene (DMBA) stimulated rat experimental model

The aim of the study was to analyze morphological changes of the epithelial surface and underlying connective tissue cores (CTCs) of the lingual mucosa in the rat using a DMBA induced pre-cancerous experimental model. Lightmicroscopically, initially DMBA treated sections exhibited infiltration of chronic inflammatory cells. At 16 weeks, aldehyde-fuchsin (AF) positive elastic fibers decreased and were scanty in the juxtaepithelium. On the other hand, rather densely packed thick bundles of AF positive fibers were observable in the deep layers of lamina propria. Carcinomas were not found at any stage, however, epithelial dysplasia was observed at 24 weeks post-treatment with DMBA. Scanning electron microscopy revealed an irregular arrangement of filiform papillae 4-12 weeks following DMBA stimulation. Patchy degenerated areas were observed especially at 16-24 weeks post-treatment and filiform papillae were totally attenuated on the central part of the degenerated areas. After removal of the epithelium, attenuated CTCs were observed from 4-8 weeks. Morphology of CTCs seemed to be gradually remodeled and severely altered in the later stage. The CTCs were however attenuated and exhibited a patchy distribution. The animal experimental model in this study revealed degenerative morphological changes of CTCs of the lingual papillae in the precancerous stage induced by DMBA.

Oral premalignant lesions: is a biopsy reliable?

PURPOSE

The purpose of the present retrospective study was to learn whether a biopsy of oral premalignant lesions, leukoplakia and erythroplakia, shows histopathological findings representative of the whole surgically removed lesion. Moreover, to see whether histopathological characteristics of the whole lesion are significant for future malignant development after surgery.

MATERIALS AND METHODS

A total of 101 lesions in 96 patients were included, 42 lesions (41%) being homogenous and 50 (50%) non-homogenous leukoplakias, whereas nine (9%) were erythroplakias. The lesions were biopsied and subsequently surgically removed on the average of 10.4 months after biopsy. Surgical specimens were examined in two or more step sections distributed throughout the specimen. The histological findings of the biopsies were compared with those of the whole lesions. After surgical intervention the patients were followed (mean 6.8 years, range: 1.5-18.6), and new biopsies taken in case of recurrences. Smokers (73%) were encouraged to quit smoking and candidal infections were treated. The possible influence of different variables on the risk of malignant development was estimated by means of logistic regression analysis.

RESULTS

Histological examination of the whole lesions showed that seven lesions (7%) harboured a carcinoma and 70 lesions (69%) showed a degree of epithelial dysplasia or carcinoma in situ. Eleven lesions (12%) developed carcinoma after a mean follow-up period of 7.5 years. A comparison of the degree of dysplasia in the biopsies with that of the whole lesion demonstrated variation with concurrent diagnosis in 49% of the lesions and in 79% after inclusion of lesions with one degree up or down the scale of epithelial dysplasia.

CONCLUSION

The estimated odds ratio showed that none of the associated variables including presence of any degree of epithelial dysplasia in the whole lesion, site, demarcation and smoking had influence on the risk of malignant development.

Long-term treatment outcome of oral premalignant lesions

The purpose of the present retrospective study was to learn the long-term outcome of oral premalignant lesions, leukoplakia and erythroplakia, with or without surgical intervention and to relate the outcome to factors supposed to be significant for malignant development including clinical type, demarcation, size, site, presence of epithelial dysplasia, smoking and surgery. A total of 269 lesions in 236 patients were included. Ninety-four lesions were surgically removed, 39 lesions (41%) being homogenous and 46 (49%) non-homogenous leukoplakias whereas nine (5%) were erythroplakias. Seventy-three percent of the lesions were associated with tobacco habits. The mean size of the lesions was 486 mm(2), and 71% of the lesions showed a degree of epithelial dysplasia. After excision the defects were closed primarily by transposition of mucosal flaps or they were covered by free mucosal or skin grafts. A few defects were left for secondary healing. After surgical treatment the patients were followed (mean 6.8 yrs, range 1.5-18.6 yrs), and new biopsies taken in case of recurrences. One hundred and seventy five lesions had no surgical intervention, 149 lesions (85%) being homogenous and 20 (11%) non-homogenous leukoplakias, and 6 (3%) erythroplakias. Eighty-one percent of the lesions were associated with smoking. The mean size of the lesions was 503 mm(2) and 21 of the lesions (12%) exhibited epithelial dysplasia. Sixty-five lesions were not biopsied. These patients were also followed (mean 5.5 yrs, range 1.1-20.2 yrs), and biopsies taken in case of changes indicative of malignant development. All patients were encouraged to quit smoking and candidal infections were treated. The possible role of different variables for malignant development was estimated by means of logistic regression analysis. Following surgical treatment 11 lesions (12%) developed carcinoma after a mean follow-up period of 7.5 yrs. Non-homogenous leukoplakia accounted for the highest frequency of malignant development, i.e. 20%, whereas 3% of the homogenous leukoplakias developed carcinomas. Surgically treated lesions with slight, moderate, severe and no epithelial dysplasia developed carcinoma with similar frequencies, i.e. 9-11%. Without surgical intervention 16% of the 175 lesions disappeared whereas seven lesions (4%) developed carcinoma after a mean observation period of 6.6 yrs. The highest frequency of malignant development (15%) was seen for non-homogenous leukoplakias, this figure being 3% for homogenous leukoplakias. Fourteen percent of lesions with slight epithelial dysplasia developed malignancy and 2% of lesions with no dysplasia showed malignant transformation. Logistic regression analysis showed a seven times increased risk (OR = 7.0) of non-homogenous leukoplakia for malignant development as compared with homogenous leukoplakia and a 5.4 times increased risk for malignant development for lesions with a size exceeding 200 mm(2). No other examined variables including presence of any degree of epithelial dysplasia, site, demarcation, smoking and surgical intervention were statistically significant factors for malignant development.

DNA vaccine against hamster oral papillomavirus-associated oral cancer

Previously we developed a carcinogenesis model involving the combination of 9,10-dimethyl-1,2-benzanthracene (DMBA) application with physical wounding of hamster lingual mucosa. The presence of a novel hamster oral papillomavirus (HOPV) was demonstrated and its genome sequenced. In the present study, this HOPV hamster model was used to test whether vaccination with the L1 gene could prevent the development of oral carcinoma. DNA plasmids encoding the L1 gene or the vector alone were injected intramuscularly into 20 vaccinated and 20 control hamsters, respectively. The lingual tips of the hamsters were painted with DMBA for 8 weeks. A portion of the lingual tips was excised, and the tips were then painted daily with DMBA until the animals were killed 13 days later. All control hamsters developed lingual carcinoma, whereas 12 of the L1-vaccinated hamsters showed no lesions. These results suggest that immunization with L1 DNA vaccines may prevent the development of papillomavirus-associated oral cancer.

A preliminary investigation of an association between dental restorations and carcinoma of the tongue

The potential association of dental restorations and tongue carcinoma was studied. We reviewed the available pretreatment dental records of 133 patients with carcinoma of the tongue seen at the British Columbia Cancer Agency between 1958 and 1992. 75 patients had teeth adjacent to the ipsilateral side of the cancer (involved side) and the contralateral (control) side of the tongue, resulting in 150 tongue/teeth pairings. Overall there was no significant association between the presence of dental fillings and tongue carcinoma, as the prevalence of bilateral dental restorations was high. Dental restorations were found in 6 patients on the involved side only. Only 1 patient developed a cancer adjacent to normal teeth with contralateral restorations. We feel that this observation merits more study. Meanwhile, careful assessment of dentition and aggressive treatment of dysplastic lesions are warranted.

Experimental odontogenic tumors produced by ethylnitrosourea injections and mechanical injuries

The present study was carried out to investigate odontogenic tumor induction in the rats by injections of carcinogen N-ethyl-N-nitrosourea (ENU) coupled with incisional wounds. The animals which received local injections of ENU in the region of incisor tooth germ of the right mandible every other day for 19 days after birth coupled with incisional wounding in the same region at 2 and 8 days, developed odontogenic carcinomas. However, the animals which were given local injections of ENU in the region of incisor tooth germ but did not receive incisional wounds, showed no pathologic changes. The animals which received both local injections of physiologic salt solution and incisional wounds in the same manner as mentioned above, did not exhibit any pathologic changes. The present results indicate that local administration of carcinogen ENU coupled with mechanical injuries, namely incisional wounding, caused the production of odontogenic carcinomas in the incisor region of the mandible in rats.

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.

In situ freezing of the rat urinary bladder: DNA adduct formation in the bladder epithelium demonstrated by 32P-postlabeling assay

In situ freezing of the urinary bladder has been demonstrated to exert tumor-initiating potential in two-stage urinary bladder carcinogenesis in the rat. In the present experiment, DNA modification was examined after in situ freezing of the whole urinary bladder performed by pinching with frozen forceps at -15 degrees C or -30 degrees C for 2 s. The 32P-postlabeling analysis revealed at least 2 DNA adducts in the epithelial cells of the urinary bladder collected 3 days after freezing. Single-strand breaks of DNA were also found by means of the alkaline elution assay in the bladder epithelium collected 10 min after freezing. Thus, the previously demonstrated tumor-initiating activity of in situ freezing in urinary bladder carcinogenesis was revealed to be associated with substantial DNA damage and adduct formation.

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.