Further electron microscopic studies on the mechanism of carcinogenesis: the specificity of the changes in carcinogen-treated mouse skin

Analysis of images for detection of oral epithelial dysplasia: A review

This paper provides a review of various image analysis approaches that have been previously used for recognition of dysplasia in images of the epithelium of the oral cavity. This domain has become especially admissible with the uncovering of the importance of image analysis which can probably be an aid to subjective diagnosis by histopathologists. Oral malignancy is a rampant form of cancer found among people of the Indian subcontinent due to various deleterious habits like consumption of tobacco, areca nut, betel leaf etc. Oral Submucous Fibrosis, a precancer, whose pathological category falls between normal epithelium and epithelial dysplasia, is caused because of these habits and can ultimately lead to oral cancer. Hence early detection of this condition is necessary. Image analysis methods for this purpose have an enormous potential which can also reduce the heavy workload of pathologists and to refine the criterion of interpretation. This paper starts with a critique of statistics of oral carcinoma in India and distribution of cancer in intra-oral sites and moves on to its causes and diagnostic approaches including causative agents, problems in curative approach and importance of image analysis in cancer detection. The various image analysis methods to appraise the cytological and architectural changes accompanied by Oral Epithelial Dysplasia in the images of the oral epithelial region have been described in relation to 2005 WHO Classification System and it was found that in future, analysis of images based on the mentioned methods has the potential in better interpretation and diagnosis of oral carcinoma.

Role of the host stroma in cancer and its therapeutic significance

Current cancer research focuses mainly upon the cancer cells in malignant tumours and is providing a growing database about aberrations in their genetic composition. However, tumours also contain non-cancerous host tissue, referred to as the stroma, which plays an active and indispensable role in tumour growth and influences the virulence of the neoplasm towards the host. Many cell types inhabit the stroma, amidst apparently inert fibrous and viscous matrix material, composed of complex polysaccharides, proteins and other molecules. Actually, all of these elements are in constant turnover, causing unpredictable evolution in the properties of the community. This article provides pathologic observations and data on reciprocal interactions between these stromal and neoplastic components of tumours and how they change during the course of the disease. Malignant progression depends upon dauntingly intricate communications between different specialised lineages within the cellular society, which enable rapid adaptation to changing circumstances. Opportunistic misuse of such communication networks enables tumour cells to recruit and incorporate adjacent normal stroma into their midst, so that they may grow, infiltrate and parasitise the host. The absolute dependency of primary tumours and metastases on their diverse stromal components for survival and their insatiable need to continuously recruit more stroma to support expansion, renders them vulnerable to strategies capable of disrupting the cellular interactions involved. This dependency is of critical importance for cancer therapy research, and proposed methods for turning this parasitic behaviour of tumours against themselves are suggested below.

Inappropriate gene expression in human cancer and its far-reaching biological and clinical significance

This article provides a broad overview of the field of inappropriate gene expression in many organisms across the animal and plant kingdoms as well as its importance to human disease in general and cancer in particular. Study of the topic is especially important for understanding how the chaotic maelstrom of evolving and cascading regulatory genetic interactions in an advancing cancer produces its clinical effects and for designing pragmatic solutions to how such disorder might eventually be tamed. It is emphasized that the topic warrants much more attention in research and in clinical practice because of the added value it brings to refining cancer diagnosis and treatment and to the assessment of prognostic markers. It is also particularly relevant to understanding the etiology and extensive clinical manifestations of paraneoplastic syndromes affecting multiple organs remote from the tumor and the treatment or amelioration of the substantial morbidity that they cause in cancer patients. More broadly, inappropriate expression can be caused by a number of mechanisms including mutations, rearrangements of the genome, and viral insertions and, under prolonged selection pressures, also has the potential to be an agent of evolutionary change.

Morphometric computer-assisted image analysis of oral epithelial cells in normal epithelium and leukoplakia

BACKGROUND

There are very few studies documenting morphometric parameters of normal oral mucosa and leukoplakia. The present study was undertaken to establish the morphometric parameters of the parabasal and spinous cells of normal oral epithelium. Analysis of changes occurring in these cells in leukoplakia was also done.

METHODS

This study was conducted on tissue sections of clinically normal oral mucosa and leukoplakia. Morphometric analysis was done for parabasal and spinous cells. Statistical analysis was done using one way ANOVA and Mann-Whitney test.

RESULTS

Morphometric parameters were greater in the spinous cells than in parabasal cells in normal oral mucosa. Leukoplakia showed greater cellular and nuclear parameters than normal mucosa.

CONCLUSION

Normal oral epithelium showed site-wise difference in cell and nuclear measurements. Nuclear parameters showed a statistically significant change than cellular parameters in dysplasia. These changes were expressed in the earliest stage of transformation to dysplasia.

Placental glutathione S-transferase isoenzyme expression in polycyclic aromatic hydrocarbon-induced hamster buccal pouch mucosa

Placental glutathione S-transferase (GST-P) immunohistochemical activity in polycyclic aromatic hydrocarbon (PAH)-induced hamster buccal pouch mucosa (HBPM) was investigated. Equimolar concentrations of 3,4-benzo[a]pyrene (BP), benz[a]anthracene (BA) and 20-methylcholanthrene (MC) in mineral oil solution were applied three times per week for up to 20 weeks to bilateral pouches of the hamsters. Control pouches were treated with 7,12-dimethylbenz[a]anthracene (DMBA), turpentine and mineral oil, respectively. A significant increase in the number of GST-P foci in the dysplastic pouches was found when compared with the hyperkeratotic and hyperplastic pouches after 5 weeks' DMBA treatment. The average numbers of GST-P positive stainings were significantly higher in DMBA-treated groups than in BP-, BA- and MC-treated groups killed at 5, 20, 30 and 40 weeks. No GST-P positivity was found in any pouches treated with turpentine and mineral oil observed at various periods. These results highlight the carcinogen-specificity of GST-P chemically induced in HBPM and indicate that induction of GST-P in pouch mucosa is linked with the carcinogenic potency of PAHs. The present study underpins the hypothesis that GST-P chemically induced in HBPM is an early marker of ongoing squamous cell carcinogenesis.

Changes in cytokeratins following treatment of hamster cheek pouch epithelia with hyperplastic or neoplastic agents

The effects of four different hyperplastic agents and of the carcinogen DMBA on cytokeratin expression in hamster cheek pouch epithelia were compared. Reversible hyperplasia was produced by the application of either oil of turpentine, vitamin A or TPA. No hyperplastic changes were produced by application of EPP. Apart from the transient appearance of a 45 kDa cytokeratin in one group treated with vitamin A, the immunohistochemical staining patterns and immunoblot profiles of cytokeratins from cheek pouches treated with each of the hyperplastic agents were identical to controls. Following application of DMBA, the cytokeratins stained with increased intensity in the spinous and granular cell layers. This was associated with increased amounts of 42-56 kDa cytokeratins and decreased production of 62-75 kDa cytokeratins. Monoclonal antibody AE1 detected a 45 kDa cytokeratin in extracts of DMBA-treated epithelia that was not detected in untreated epithelial extracts. Monoclonal antibody AE3 detected an additional 54 kDa cytokeratin band in extracts of DMBA-treated epithelia. These cytokeratin changes were present in preneoplastic epithelia and maintained in neoplastic epithelia.

Morphometric analysis of suprabasal cells in oral white lesions

Surgical specimens from the cheek mucosa of 73 patients with white lesions were studied to determine various morphometric parameters that would help differentiate between the various types of oral mucosal white lesions that carry a risk of malignant change. Four cell types were represented: traumatic keratosis, leucoplakia, candidal leucoplakia and lichen planus, in addition to a control group of normal mucosa. The shape and size of the epithelial cells in two cell compartments, parabasal and spinous, were investigated by an interactive image analysis system (IBAS-1). The results showed an increase in the cell size in the parabasal cell compartment of all the white lesions compared with the normal mucosa. In the spinous cell compartment there was an increase in the cell size in lichen planus and traumatic keratosis; leucoplakia and candidal leucoplakia showed a slight decrease in cell size compared with the normal mucosa. Attempts to discriminate between the four groups of white lesions showed that these parameters can provide a high level of separation between lichen planus and the three other groups, but not between leucoplakia, candidal leucoplakia, and traumatic keratosis.

Possible involvement of reorganization of actin filaments, induced by tumor-promoting phorbol esters, in changes in colony shape and enhancement of proliferation of cultured epithelial cells

Tumor promoters are known to induce reorganization of actin, morphological changes and enhancement of proliferation of epidermal cells in vivo. In this study, we have examined the effects of tumor promoters on these events to clarify the role played by the organization of actin filaments in the regulation of the shape and growth of colonies of epithelial cells in culture. Treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) caused a change in the shape of colonies of FL and Madin-Darby canine kidney (MDCK) cells within 6 hr. Changes in the shape of colonies were consistent with the morphological change of individual cells and the dissociation of groups of cells in the colonies. Addition of TPA also caused reorganization of actin filaments after 2 hr, and it caused enhancement of proliferation of FL and MDCK cells after 48 hr but did not cause any such changes in KB cells. However, the binding affinities of 4 beta-phorbol 12,13-dibutyrate (PDBu) to FL and MDCK cells were similar to that of PDBu to KB cells. Related tumor promoters such as phorbol 12,13 didecanoate (PDD) and mezerein caused effects similar to those caused by TPA. In contrast, nontumor promoting phorbol esters, such as 4 alpha-PDD and phorbol, had no effect. Cyclic AMP blocked the TPA-induced changes in FL and MDCK cells. These results suggest that TPA-induced reorganization of actin filaments which can be inhibited by cyclic AMP results in changes in the shape of colonies and enhancement of proliferation.

Morphometric analysis of basal cell layer in oral premalignant white lesions and squamous cell carcinoma

The size and shape of the cells in the basal cell layer of the oral epithelium in 100 specimens from oral mucosa were studied by using an interactive image analysis system (IBAS-1). Four groups of white lesions (traumatic keratosis, lichen planus, leucoplakia, and a "risk group") in addition to two control groups (normal mucosa and squamous cell carcinoma) were studied retrospectively. The results showed a progressive increase in the dimensions (area, perimeter, and maximum diameter) of the nuclei from normal mucosa through traumatic keratosis, lichen planus, leucoplakia and the "risk group" to carcinoma, with considerable differences. The nucleus in squamous cell carcinoma was twice as large as in normal mucosa. A substantial increase in the dimensions of both the cell and the nucleus was found in the "risk group." The nucleo:cytoplasmic ratio, contrary to what might have been anticipated in risk lesions, did not show considerable differences between the diagnostic groups. Furthermore, it was slightly decreased in the risk group compared with the normal mucosa. The shape factors (form PE and contour index) seemed to be less helpful in the identification of the "risk group." The size of the basal cell and its nucleus can be of diagnostic value for lesions with a high risk of malignant transformation.

Changes in the rate of epithelial proliferation of rat oral mucosa in response to acute inflammation induced by turpentine

Inflammatory lesions were produced in the buccal mucosa by a subepithelial injection of turpentine; animals were killed 24 h later, 1 h after an intravenous injection of tritiated thymidine ( [3H]-Tdr). Control rats were given [3H]-Tdr but no turpentine. Lesions comprised a turpentine pool surrounded by a dense layer of inflammatory cells, beyond which the tissues were more diffusely inflamed. The labelling index (L.I.) for mitotic activity in overlying epithelium was determined in a region (C) close to the layer of dense infiltration and in a region (D) more distant. The L.I. in region D was over four times greater than in region C, and nearly four times greater than that of the contralateral, uninjected cheek. The L.I. in the uninjected cheek was significantly lower than that in controls, which may indicate a systemic depression of proliferative activity in the experimental animals, probably due to stress. Thus mild inflammatory injury stimulates epithelial proliferation, whereas more severe inflammation depresses it, perhaps due to more extensive progenitor-cell damage.

Morphology of peritumoral proteoglycan alterations in the rabbit mesentery invaded by V2 carcinoma cells

After intraperitoneal implantation into Swiss Silver rabbits, V2 rabbit carcinoma cells invade the mesentery where they form nodules of different size and texture: compact (less than 120 microns in diameter), loose (120-250 microns) and mixed (above 200 microns). Together with tumor development, certain changes take place in the loose connective tissue of the mesentery. Application of TEM, together with use of safranin O, has shown that, in areas free of tumor growth, collagen bundles become thick and heavy and proteoglycan density is increased. Concurrently, the number of fibrocytes, now transformed to fibroblasts, increases. Small, compact nodules are surrounded by a concentrically arranged extracellular matrix. Its overall density is similar to that of nodule-free areas. In the immediate vicinity of large, loose nodules, all constituents of the extracellular matrix disappear. Adjacent connective tissue is partly destroyed but still contains collagen fibers and proteoglycans. These findings suggest the following: The presence of V2 carcinoma cells induces marked alterations in the structured and non-structured components of the extracellular matrix. These changes are, at the same time, progressive and regressive and the occurrence of one or the other depends on local tumor progression. Progressive alterations may result from an increased activity of fibroblasts. Since degradative effects, on the other hand, are only seen in the immediate vicinity of larger tumor aggregates, it is assumed that a minimal number of tumor cells is essential for destruction of extracellular matrix.

Ultrastructural morphometry of collagen from lamina propria during experimental oral carcinogenesis and chronic inflammation

Stereological point-counting methods were used to determine the volumetric alterations in collagen from the lamina propria immediately beneath the epithelial-connective tissue junction in hamster check-pouch mucosa treated with the chemical carcinogen DMBA. In addition, a non-neoplastic inflammatory control was evaluated in which a delayed hypersensitivity reaction was induced by the contact-sensitising agent DNCB. DMBA-treated tissues were assigned to histopathologically defined hyperplasia, dysplasia and carcinoma stages. The volume densities of collagen present in unit volume of extracellular lamina propria were found to decrease progressively and significantly in DMBA-treated tissues when compared with values obtained from normal untreated mucosa. Values from the inflammatory control were comparable with those from the dysplasia stage of carcinogenesis. The mechanisms responsible for these decreases in collagen volume density are unknown, but contributory factors might include collagen destruction by enzymes originating in either the epithelium or the cells of the inflammatory infiltrate, dilution of collagen produced by inflammatory oedema or alterations in the synthetic capabilities of fibroblasts.

Epidermal-dermal junction during experimental skin carcinogenesis and cocarcinogenesis as revealed by scanning electron microscopy

During epidermal carcinogenesis important changes in the epidermal-dermal junction take place. Because of methodological difficulties may be these changes, especially those concerned with three-dimensional organization of the junction, remain unsatisfactorily investigated. To obtain new information, we studied with scanning electron microscopy (SEM) the development of carcinogenic changes in the epidermis of mice induced by DMBA-TPA, DMBA alone, and by the cocarcinogen TPA alone. We correlated the results with those from transmission electron microscopy and light microscopy. Although the epidermal changes morphologically showed similarities, biologically they differed. With them, distinct changes in the epidermal-dermal junction developed, that could be followed through early, hyperplastic and neoplastic phases. With the SEM the first changes were seen in the basal layer of the epidermis and concerned the cell arrangement. SEM provided information about the localization and development of incipient epidermal carcinomas induced by DMBA-TPA and DMBA treatment, as well as about the changes in the basal lamina. These can be classified by their surface, their extent and their frequency throughout large regions. Our studies indicate that these changes vary greatly, depending upon the treatment used and the time of their development. Only the progressive disintegration of the basal lamina is characteristic of carcinogenesis.

Hamster tongue carcinogenesis II. Quantitative morphologic aspects of preneoplastic epithelium

Stereological techniques have been used to quantify some morphologic aspects of non-neoplastic and preneoplastic hyperplasia in hamster tongue. Scratching hamster ventral lingual mucosa and applying acetone thrice weekly resulted in moderate epithelial hyperplasia in biopsy material removed at 16 weeks. There was a significant increase in the number of progenitor cells per defined histologic field and a striking increase in the number of progenitor cells related to each unit of surface length. There was a small but significant increase in basement membrane length. In the experimental group in which the ventral lingual mucosa was scratched and painted with 0.5% DMBA in acetone there was pronounced epithelial hyperplasia with increases in the thickness of the progenitor, maturation and keratinized compartments. Progenitor cells showed hyperplasia and hypertrophy. The number of progenitor cells related to each unit of surface length was significantly greater than normal or control values. There was a significant increase in the basement membrane length per field, reflecting an increased folding and prominence of the rete ridges.

Ultrastructural alterations in experimental lingual leukoplakia and carcinoma

Epidermoid carcinomas, preceded by dysplastic leukoplakic lesions, were produced on the right lateral borders of the tongues of Syrian hamsters by the application, three times per week, of DMBA in acetone after the area had been scratched with a root canal broach. Animals were killed at 12 to 13 weeks and 15 to 16 weeks. Electron microscopic studies of both the dysplastic leukoplakic lesions and the well-differentiated epidermoid carcinomas revealed clumping of tonofilaments and widening of intercellular spaces, in addition to the cellular pleomorphism, altered nuclear-cytoplasmic ratio, and prominent nucleoli observed with the light microscope. In the carcinomas, there were variations in the morphology of mitochondria, with tubular forms in evidence. The basal lamina in the carcinomas was discontinuous. Pseudopodia arising from basal cells were seen in areas of basal lamina discontinuity.

The effect of turpentine on hamster cheek pouch mucosa: a model of epithelial hyperplasia and hyperkeratosis

Hamster cheek pouches were painted thrice weekly with 50% v/v turpentine in liquid paraffin over periods ranging from 1 day to 16 weeks. Pouch mucosa was examined histologically for changes and measurements of epithelial thickness were made with a calibrated eyepiece micrometer. An increase in epithelial thickness was first observed 48 hrs. after a single painting and was accompanied by inflammatory changes in both epithelium and connective tissue. Maximal epithelial thickening occurred after 9 weeks of thrice weekly painting. Cheek pouches of animals left without further treatment for up to 1 year following 9 weeks painting were indistinguishable from controls. The epithelial response to treatment with turpentine is that of a reversible benign epithelial hyperplasia with hyperkeratosis.

A qualitative and quantitative electronmicroscopic study of the structure of the adenoid cystic carcinoma of human minor salivary glands

The fine structural characteristics of five adenoid cystic carcinomas of human minor salivary galnds and a quantitative assessment of the relative volumes occupied by morphologically defined cell types in these tumors are reported. We observed that the cyst-like spaces which give the characteristic cribriform pattern to the adenoid cystic carcinoma contain replicated basement membrane-like materail. Material comprisimg aggregates of fine tubules having a median diameter of 270 A, and rounded, electron dense bodies were noted within duct-like lumena of one tumor. In addition, dilatation of the intercellular spaces and squamous metaplasia were noted. From 500 electronmicrographs obtained by standardized techniques and used for the morphological part of the study, 175 were selected by a random sampling method and analyzed by the stereological technique of point counting. This method demonstrated that duct type cells occupied 75% by volume of the tumor in these glands; myoepithelial cells occupied 3%, acinar cells occupied 2%, and other tissues occupied 22% of the tumors. These proportions differ significantly (P less than 0.001) from our previously published figures for normal specimens of these glands.

Fine structure of murine mammary tumours: the relationship between epithelium and connective tissue in neoplasms induced by various agents

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