Expression of bcl-2 in salivary glands and salivary gland adenomas. A contribution to the reserve cell theory

Expression of FOXI1 and POU2F3 varies among different salivary gland neoplasms and is higher in Warthin tumor

PURPOSE

Salivary gland tumors are histologically diverse. Ionocytes and tuft cells, rare epithelial cells found in normal salivary glands, might be associated with salivary tumors. Here, we explored the expression of FOXI1 and POU2F3, master regulators of ionocytes and tuft cells, respectively, for common salivary neoplasms using immunohistochemistry.

METHODS

We analyzed normal salivary tissues and nine salivary gland tumors; Warthin tumors (WT), pleomorphic adenomas (PA), basal cell adenomas, and oncocytomas were benign, whereas mucoepidermoid, adenoid cystic, acinic cell, salivary duct carcinomas, and polymorphous adenocarcinomas were malignant.

RESULTS

Normal salivary glands contained a few FOXI1- and POU2F3-positive cells in the ducts instead of the acini, consistent with ionocytes and tuft cells, respectively. Among the benign tumors, only WTs and PAs consistently expressed FOXI1 (10/10 and 9/10, respectively). The median H-score of WTs was significantly higher than that of PAs (17.5 vs. 4, P = 0.01). While WTs and PAs harbored POU2F3-positive cells (10/10 and 9/10, respectively), the median H-score was higher in WTs than in PAs (10.5 vs 4, respectively). Furthermore, WTs exhibited a unique staining pattern of FOXI1- and POU2F3-positive cells, which were present in luminal and abluminal locations, respectively. Whereas none of the malignant tumors expressed FOXI1, only adenoid cystic carcinoma consistently expressed POU2F3 (5/5), with a median H-score of 4.

CONCLUSION

The expression patterns of the characteristic transcription factors found in ionocytes and tuft cells vary among salivary gland tumor types and are higher in WT, which might be relevant for understanding and diagnosing salivary gland neoplasms.

Digital image analysis of intraepithelial B-lymphocytes to assess lymphoepithelial lesions in salivary glands of Sjögren's syndrome patients

OBJECTIVE

Salivary glands of primary SS (pSS) patients characteristically harbour periductal infiltrates, in which lymphoepithelial lesions (LELs) can develop. LELs are composed of hyperplastic ductal epithelium with infiltrating lymphocytes and may assist in the challenging diagnostic process of pSS. As manual identification of LELs remains difficult, we aimed to identify LELs by using an objective digital image analysis (DIA) algorithm that detects intraepithelial lymphocytes.

METHODS

A virtual triple-staining technique developed for this study was used to count intraepithelial lymphocytes in consecutive slides stained for CD3 (T-lymphocytes), high-molecular-weight cytokeratin (hmwCK) (striated ducts) and CD20 (B-lymphocytes) in labial and parotid gland biopsies in a diagnostic cohort of 109 sicca patients. Patients were classified as having pSS or non-SS according to the ACR-EULAR classification criteria.

RESULTS

T-lymphocytes were detected in almost all analysed ducts of pSS and non-SS sicca patients, whereas intraepithelial B-lymphocytes were present in 59-68% of labial and parotid gland biopsies of pSS patients, against only 2-3% of patients classified as non-SS. Intraepithelial B-lymphocytes were found in almost all striated ducts with hyperplasia (LELs). Remarkably, ∼25% of analysed striated ducts without hyperplasia of pSS patients also contained B-lymphocytes (precursor-LELs). Furthermore, presence of intraepithelial B-lymphocytes was associated with clinical parameters of pSS (i.e. serology).

CONCLUSION

The presence of intraepithelial B-lymphocytes in salivary gland biopsies of sicca patients is a clear indicator of pSS and can be used as an objective alternative to LEL scoring. Therefore, identification of B-lymphocyte-containing ducts should be added to the diagnostic histopathological work-up of patients suspected of pSS.

Cellular senescence contributes to radiation-induced hyposalivation by affecting the stem/progenitor cell niche

Radiotherapy for head and neck cancer is associated with impairment of salivary gland function and consequent xerostomia, which has a devastating effect on the quality of life of the patients. The mechanism of radiation-induced salivary gland damage is not completely understood. Cellular senescence is a permanent state of cell cycle arrest accompanied by a secretory phenotype which contributes to inflammation and tissue deterioration. Genotoxic stresses, including radiation-induced DNA damage, are known to induce a senescence response. Here, we show that radiation induces cellular senescence preferentially in the salivary gland stem/progenitor cell niche of mouse models and patients. Similarly, salivary gland-derived organoids show increased expression of senescence markers and pro-inflammatory senescence-associated secretory phenotype (SASP) factors after radiation exposure. Clearance of senescent cells by selective removal of p16Ink4a-positive cells by the drug ganciclovir or the senolytic drug ABT263 lead to increased stem cell self-renewal capacity as measured by organoid formation efficiency. Additionally, pharmacological treatment with ABT263 in mice irradiated to the salivary glands mitigates tissue degeneration, thus preserving salivation. Our data suggest that senescence in the salivary gland stem/progenitor cell niche contributes to radiation-induced hyposalivation. Pharmacological targeting of senescent cells may represent a therapeutic strategy to prevent radiotherapy-induced xerostomia.

Histopathological analysis of the differential diagnosis of peripheral odontogenic fibroma from fibrous epulis

OBJECTIVES

Peripheral odontogenic fibroma (POF) is a relatively rare odontogenic tumor of the gingiva. Although its histological differential diagnosis from fibrous epulis (FE) is important, no study has reported the differences in their expression of immunohistochemical markers. Here, we compared the expression of tumor markers that are frequently used for the differential diagnosis of fibroproliferative lesions between POF and FE.

METHODS

Forty cases were selected, including 20 POF and 20 FE cases. CD34, B cell lymphoma (Bcl)-2, and Ki-67 were used as markers for immunohistochemical examination. The positive cell ratio was calculated, and Mann-Whitney U test was performed for statistical analysis.

RESULTS

POF and FE were negative for CD34 expression but showed Bcl-2 and Ki-67 expression. The ratio of Bcl-2- and Ki-67-positive cells was significantly higher in POF than in FE (p < 0.001).

CONCLUSIONS

POF is CD34 negative, and Bcl-2 and Ki-67 positive-cell ratio differs between POF and FE, suggesting that these proteins may serve as immunohistochemical markers for the differential diagnosis of POF.

Polymorphous Low Grade Adenocarcinoma of the Parotid Gland. Cytological, Histological and Immunohistochemical Features and Review of the Literature

Aim: Polymorphous low grade adenocarcinoma of the salivary glands (PLGA) is a low grade neoplasm that predominantly occurs in the minor salivary glands. In this site is amenable to biopsy and histologic diagnosis. However, experience with cytological findings in these tumors is limited. We describe the cytology of this entity. Experimental design: Touch imprint cytology of a primary parotid PLGA is specified and correlated with histology. Results: Smears were hypercellular showing branching papillae, sheets and clusters of uniform cells with bland nuclei, dispersed chromatin and no nucleoli. The cells had a scant to moderate amount of eosinophilic cytoplasm. They formed tubular structures containing hyaline globules. Conclusions. The cytologic differential diagnosis of PLGA includes adenoid cystic carcinoma, pleomorphic adenoma, and monomorphic adenoma. PLGA should be considered in the differential diagnosis of head and neck tumors, where the cytology suggests on of the above mentioned tumors, even when the clinical findings (involvement of a major salivary gland, lymph node metastasis) is not typical of PLGA.

Bcl-2 expression is essential for development and normal physiological properties of tooth hard tissue and saliva production

BACKGROUND

Apoptosis plays a fundamental role in appropriate tissue development and function. Although expression of Bcl-2 has been reported during tooth and submandibular gland (SMG) development, the physiological role Bcl-2 plays during these processes has not been addressed. This study was performed to evaluate the impact of Bcl-2 expression on the formation and properties of tooth hard tissue, and saliva production.

METHODS

Twenty-four mice (12 males and 12 females) were divided into three groups of eight (n=8): group A (Bcl-2 +/+), group B (Bcl-2 +/-), and group C (Bcl-2 -/-) and subjected to micro-CT analyses. The mineral content of first molars was analyzed by X-Ray diffraction (XRD) and scanning electron microscopy (SEM) color dot map. The surface microhardness was determined by Vickers test on labial surfaces of incisors. Saliva was collected from different groups of mice after subcutaneous injection of pilocarpine.

RESULTS

Samples from Bcl-2 -/- mice showed significantly smaller micro-CT values, lower and poor crystallinity of hydroxyapatite (HA), and lowest surface micro hardness. SMG from Bcl-2 -/- mice showed remarkable reduction in size, consistent with reduced saliva accumulation.

CONCLUSIONS

The absence of Bcl-2 expression in SMG did not affect the expression of other Bcl-2 family members. Thus, Bcl-2 expression influence on the formation and properties of tooth hard tissue, and saliva accumulation.

SIGNIFICANCE

Bcl-2 expression has a significant impact on the mineralogical content of enamel crystals of tooth structure. Lack of Bcl-2 expression led to impaired production of enamel ACP crystals.

Biomarker Analysis in Carcinoma ex Pleomorphic Adenoma at an Early Phase of Carcinomatous Transformation

Diagnostic criteria for intracapsular carcinoma ex pleomorphic adenoma (CXPA) are subjective and vary among authors. Biomarker analysis, which could provide more objective evaluation of these tumors, has rarely been studied in intracapsular CXPA. Immunohistochemical evaluation of c-erbB-2, p53 protein, bcl-2, and Ki-67 was performed in 8 cases of CXPA at an early phase of malignant transformation (4 intracapsular and 4 minimally invasive) and in 17 pleomorphic adenomas (PA). In all cases of CXPA, p53 and Ki-67 were demonstrated predominantly in luminal cells of benign and malignant areas, significantly more in the latter. Few benign myoepithelial cells were p53 positive. c-erbB-2 reactivity was strongly associated with atypical luminal cells. Bcl-2 expression was weak and focal in malignant areas from 2 cases. In conclusion, both p53 and c-erbB-2 proteins appear to be involved at an early stage of malignization of PA. In PA with atypical cells, evaluation of the expression of these 2 markers provides more objective criteria for the diagnosis of intracapsular CXPA.

Pathogenesis of Warthin's tumors

INTRODUCTION

Warthin's tumor, also known as papillary cystadenoma lymphomatosum, monomorphic adenoma, or adenolymphoma, is a benign cystic tumor of the salivary glands containing abundant lymphocytes and lymph node-like stroma. It is named after the pathologist Aldred Scott Warthin, who described two cases in 1929.

OBJECTIVE

The aim of this study is to analyze the pathogenesis of Warthin's tumor.

METHODS

A total of 15 patients with Warthin's tumor were studied. Hematoxylin and eosin stains, which have been used for at least a century and are still essential for recognizing various tissue types and the morphologic changes for cancer diagnosis, were used. Warthin's tumor was evaluated for the expression of MGMT, CD3, HSP90AA1, MMP-1, Bcl-2, CD79A, IgG, Ki-67, p53, IgM, OPN, S100, myeloperoxidase, and VEGF by immunohistochemistry.

RESULTS

Immunohistochemical staining confirmed that the immune cells within the follicles of Warthin's tumor were positive for MGMT (10.0 ± 0.34%), Ki-67 (13.3 ± 0.45%), Bcl-2 (42.6 ± 8.33), and p53 (11.6 ± 2.3). The immune cells associated with CD3 were present at the stroma of residual cells (47.3 ± 3.89); however, they were not present in the epithelium cell layers. B cells (CD79A) consistent with germinal centers were present within the immune cells and formed follicles (43.2 ± 13.5%).

CONCLUSIONS

Histopathological analysis of the stroma and parenchyma revealed balanced distribution of epithelial and stromal component. Epithelial component of the Warthin's tumor is the trigger for the tumor process. This study indicates that the Warthin tumor is a consequence of inflammatory etiology.

Recurrent salivary pleomorphic adenoma shows increased immunohistologic expression of bcl-2 oncoprotein

BACKGROUND

Internal cell biology, including apoptotic regulation, is presumed to play a key role in the development of recurrent pleomorphic adenoma (PA).

AIM

The aim of our study was to determine the relevance of B-cell lymphoma 2 (bcl-2) oncoprotein immunoexpression and distribution in primary PA, and its recurrence.

METHODS

Ten primary-non-recurrent, 14 primary-to-recur, and 28 recurrences of parotid PA patients aged 19-73 (mean 40.7±16.7) years were enrolled. The bcl-2 expression was compared between groups using a semi-quantitative histoscore, defined as the multiple of the percentage of cells by the intensity of immunostaining.

RESULTS

Widely varying bcl-2 immunoreaction was found in the epithelial areas of 91.7% of primary and 85.2% of recurrent PA. Similarly varying but much less, immunopositivity was found in the myxoid areas of 62.5% of primary and 71.4% of recurrent tumours. No obvious differences in the bcl-2 staining intensity or pattern of specific epithelial morphologic structures in either the primary-non-recurrent, primary-to-recur or recurrent tumours were found. In both the mesenchymal and epithelial areas of PA, the differences in bcl-2 immunohistoscore between the primary-non-recurrent and primary-to-recur groups were not statistically significant (P=0.62, respectively 0.51). In the mesenchymal areas, the study revealed a significantly increased histoscore in recurrent tumours compared to their corresponding primaries (P=0.01). Increased bcl-2 expression in recurrent PA suggests an exaggerated aggressiveness of that tumor.

CONCLUSION

The fact that a significant difference in the histoscore was found exclusively in the myxoid component seems to accord with the reported prevalence of the latter in recurrent and metastatic PA.

Immunohistochemical expression of metallothionein in pleomorphic adenoma of minor salivary glands: a role in the control of apoptosis?

Pleomorphic adenoma is the most common benign neoplasm of both the major and minor salivary glands. The histological features are diverse and are characterized by the involvement of epithelial-myoepithelial structures. Metallothionein is a cysteine-rich protein present in myoepithelial cells of several benign and malignant neoplasms. The function of metallothionein is associated with DNA protection, oxidative stress and apoptosis. The purpose of this study was to evaluate the expression of metallothionein in pleomorphic adenoma of the minor salivary glands. Additionally, we investigated the association of the clinicopathological features of the lesions with metallothionein, specifically its association with Bcl-2, in an attempt to evaluate the role of metallothionein in the control of apoptosis. Thirty-five cases of pleomorphic adenoma were selected and immunohistochemistry was performed for metallothionein and Bcl-2 proteins. The proteins were quantified by the Quickscore method. The samples showed epidemiological characteristics similar to those described in the literature. We did not find an association between the clinicopathological characteristics of pleomorphic adenomas and the proteins studied, but an association between metallothionein and Bcl-2 was demonstrated. The results suggest that metallothionein may have a role in the control of apoptosis in pleomorphic adenoma.

Warthin adenocarcinoma: analysis of 2 cases of a distinct salivary neoplasm

Carcinomas arising in or from the epithelial component of preexisting parotid Warthin tumors (WTs) are rare; the other histologic types of carcinoma found to arise from WTs are adenocarcinoma not otherwise specified, undifferentiated, mucoepidermoid, squamous cell, and oncocytic. The aim of this study is to describe the clinicopathologic features of a distinct salivary gland neoplasm, previously undescribed, with a striated duct phenotype arising from WT. We have designated this neoplasm "Warthin adenocarcinoma" (WA). In this retrospective study, we searched the surgical pathology files of the Department of Pathology at The University of Texas M.D. Anderson Cancer Center for cases of malignant WT and salivary adenocarcinoma not otherwise specified diagnosed from January 1, 1985, through December 31, 2006, and evaluated patients' medical records and pathologic material. We obtained tissue sections and immunohistochemically stained them with antibodies against p63; Bcl-2; cytokeratin (CK)903, CK7, CK14, and CK18; antimitochondrial antibody (AMA); smooth muscle actin; calponin; S-100; and Ki-67. We identified 2 cases of WA; both patients were women, 44 and 60 years of age, with 4.0- and 4.5-cm tumors in the left parotid gland. Histologically, the tumors were composed of bilayered duct-like structures: The inner layer was formed by a single row of columnar oxyphilic cells expressing CK7, CK14, CK18, and AMA. The outer layer was composed of multiple layers of small round dark cells with scanty cytoplasm that expressed p63, Bcl-2, and CK903 and were focally positive for AMA and negative for myoepithelial markers. The Ki-67 proliferative indices were 20%; and 25%. A residual WT with transition to carcinoma was identified in both cases. Treatment had consisted of total parotidectomy with postoperative irradiation. Patients were free of disease 1 and 3 years after treatment. Warthin adenocarcinoma is a unique salivary gland carcinoma representing the malignant epithelial counterpart of WT. The identification of additional cases would help to better elucidate the line of differentiation of the tumor and further define its natural history.

Expression of cyclooxygenase-2, Bcl-2 and Ki-67 in pleomorphic adenoma with special reference to tumor proliferation and apoptosis

The present report is of immunohistochemical and cell biological studies on cyclooxygenase(COX)-2, Bcl-2 and Ki-67 in pleomorphic adenoma (n = 35). Pleomorphic adenomas from oral minor glands (n = 15), parotid gland (n = 11), Submandibular gland (n = 8) were studied and sublingual gland (n = 1). Expression of COX-2, Bcl-2 and Ki-67 was examined immunohistologically. Immunostaining intensity of COX-2 and Bcl-2 was classified into expression levels from +3 to 0. The positivity to Ki-67 was evaluated by counting the number of positive cells per 1000 cells, and the values were expressed in as percentage. Apoptotic cells were detected using the modified TUNEL method. Expression of COX-2 mRNA was analyzed by real time PCR using fresh tissues of 4 cases. The relationship between morphological findings and the level of COX-2 mRNA expression was analyzed using a laser capture microdissection (LCM). The results of immunohistochemistry and gene analysis using LCM revealed expression of COX-2 mainly in luminar tumor cells. Expression of COX-2 in pleomorphic adenoma was correlated with expression of Bcl-2 statistically (p = 0.044 < 0.05, r = 0.342). There was only a small number of apoptotic cells cells, and intensity of expression of TUNEL was not correlated with the expression of COX-2 (p = 0.463 > 0.05, r = -0.128). There was no statistical correlation between COX-2 and Ki-67 (p = 0.97 > 0.05, r = -0.07). It is suggested that COX-2 may inhibit apoptosis mediating Bcl-2 expression in pleomorphic adenoma, rather than playing a role in cell proliferation.

Apoptosis: The Sculptor of Development

Apoptosis is a programmed mechanism of cell death recognized by its characteristic morphological and biochemical changes. Over the last decade, our understanding of the biochemistry of apoptosis has flourished. However, the physiological relevance of apoptosis remains elusive. Here, I propose that the process of programmed cell death plays an essential role in structural development. From pioneering studies almost a century ago to recent findings using modern technology, similar conclusions have emerged that highlight the fundamental role of apoptosis in vascular development. This review will recount these classic and modern studies as I survey evidence that implicates apoptosis in other aspects of development and ask how cell death can possibly contribute to homeostasis and development of the immune system. I briefly consider the mechanisms that may determine the fate of cells within the vasculature and propose new roles for the contribution of apoptosis to development and differentiation. More provocatively, I explore the possibilities that arise from this growing field of study, including prevention of developmental defects and even abnormal development after birth, such as neoplastic development. To realize these end points, the biochemical bases of apoptosis must be thoroughly understood.

Prognostic value of apoptosis and apoptosis-associated proteins in salivary gland adenoid cystic carcinoma

The purpose of the present study was to investigate the level of apoptosis and expressions of p53, mdm2 and bcl-2 proteins in salivary gland adenoid cystic carcinoma (ACC) to determine potential relationships among apoptosis, apoptosis-associated proteins and clinical cumulative survival. Thirty-nine formalin-fixed, paraffin-embedded cases, cribriform (17), tubular (13) and solid (9), were studied by immunohistochemistry. Apoptosis detection and analysis were determined by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL). There was an inverse significance between the apoptotic index (AI) and bcl-2 expression (P = 0.018), whereas no correlation was found between the AI and either p53 or mdm2 expression (P = 0.416 and P = 0.456). Co-expression of p53 and mdm2 was found in 22 cases (P = 0.037). Patients with p53-positive tumors had a worse prognosis than those with p53-negative tumors (P = 0.014). Patients with a high AI had a better cumulative survival than patients with a low AI (P = 0.038). The present study suggests that p53 expression and AI can be useful as prognostic values; bcl-2 protein plays a role in the down-regulation of apoptosis and is also potentially useful as a prognostic parameter in salivary gland ACC.

Regeneration in chronic sialadenitis: an analysis of proliferation and apoptosis based on double immunohistochemical labelling

The understanding of regeneration in salivary glands as a finely tuned balance of cellular proliferation, differentiation and apoptosis has been limited by the difficulty of identifying proliferating cells. This has been overcome in the present investigation by double immunohistochemical labelling for the proliferation-associated antigen Ki67 and for different cell-type-specific antigens applied to 8 specimens of normal parotids and 16 specimens of chronic parotid sialadenitis with particular reference to acini and intercalated ducts. In comparison with low baseline rates of proliferation in normal parotids, proliferative indices were significantly increased in chronic sialadenitis in mature acinar cells, intercalated ductal cells and myoepithelial cells without evidence of proliferation by an additional population of cells. In accordance with findings in glands of experimental animals, the present data do not support the previously postulated concept of regeneration of acini and intercalated ducts by a hypothetical population of uncommitted ductal stem cells. The demonstration of a profound capacity for intrinsic glandular regeneration from differentiated cells represents a biological basis for the good results obtained from conservative therapy of chronic sialadenitis and offers hope for novel therapies designed to reconstitute impaired salivary flow.

Immunocytochemistry of myoepithelial cells in the salivary glands

MECs are distributed on the basal aspect of the intercalated duct and acinus of human and rat salivary glands. However, they do not occur in the acinus of rat parotid glands, and sometimes occur in the striated duct of human salivary glands. MECs, as the name implies, have structural features of both epithelial and smooth muscle cells. They contract by autonomic nervous stimulation, and are thought to assist the secretion by compressing and/or reinforcing the underlying parenchyma. MECs can be best observed by immunocytochemistry. There are three types of immunocytochemical markers of MECs in salivary glands. The first type includes smooth muscle protein markers such as alpha-SMA, SMMHC, h-caldesmon and basic calponin, and these are expressed by MECs and the mesenchymal vasculature. The second type is expressed by MECs and the duct cells and includes keratins 14, 5 and 17, alpha 1 beta 1 integrin, and metallothionein. Vimentin is the third type and, in addition to MECs, is expressed by the mesenchymal cells and some duct cells. The same three types of markers are used for studying the developing gland. Development of MECs starts after the establishment of an extensively branched system of cellular cords each of which terminates as a spherical cell mass, a terminal bud. The pluripotent stem cell generates the acinar progenitor in the terminal bud and the ductal progenitor in the cellular cord. The acinar progenitor differentiates into MECs, acinar cells and intercalated duct cells, whereas the ductal progenitor differentiates into the striated and excretory duct cells. Both in the terminal bud and in the cellular cord, the immediate precursors of all types of the epithelial cells appear to express vimentin. The first identifiable MECs are seen at the periphery of the terminal bud or the immature acinus (the direct progeny of the terminal bud) as somewhat flattened cells with a single cilium projecting toward them. They express vimentin and later alpha-SMA and basic calponin. At the next developmental stage, MECs acquire cytoplasmic microfilaments and plasmalemmal caveolae but not as much as in the mature cell. They express SMMHC and, inconsistently, K14. This protein is consistently expressed in the mature cell. K14 is expressed by duct cells, and vimentin is expressed by both mesenchymal and epithelial cells. After development, the acinar progenitor and the ductal progenitor appear to reside in the acinus/intercalated duct and the larger ducts, respectively, and to contribute to the tissue homeostasis. Under unusual conditions such as massive parenchymal destruction, the acinar progenitor contributes to the maintenance of the larger ducts that result in the occurrence of striated ducts with MECs. The acinar progenitor is the origin of salivary gland tumors containing MECs. MECs in salivary gland tumors are best identified by immunocytochemistry for alpha-SMA. There are significant numbers of cells related to luminal tumor cells in the non-luminal tumor cells that have been believed to be neoplastic MECs.

Cellular basis and clinical implications of biological markers in salivary tissues: their topological distribution in murine submandibular gland

Cell proliferation and apoptosis as well as cell-cell adhesion and communication are essential processes that assure cell survival, renewal and coordination. Since junctional proteins have a tumor suppressor activity, their immunohistochemical characterization has diagnostic and prognostic value. The purpose of this report is to review the role played by junctional and proliferation-related proteins in the salivary glands and to illustrate their immunohistochemical localisation in normal murine submandibular gland. Normal salivary gland tissue was obtained from normal adult male BALB/c mice. After immediate fixation in formalin and ethanol, the samples were immunohistochemically stained for E-cadherin (HECD-1), Bcl-2, Ki67 (MIB-1), connexin26 and connexin 32, beta-catenin and gamma-catenin. Their topological distribution and reactivity were evaluated by light microscopy. The nuclei of submandibular acinar cells exhibited low to moderate staining for Ki67, but no reaction was observed in ductal cells. Murine Bcl-2 was light to moderately expressed in the latero-basal domain of cells of submandibular acini but was only lightly expressed in striated and eosinophilic ducts. The lateral domain of acinar cells were heavily stained with anti-E-cadherin, while only low levels were expressed at the cellular surface of ducts. beta-Catenin was consistently and evenly distributed along the latero-apical boundaries of eosinophilic secretory duct cells as well as on the lateral domain of acinar cells. On the contrary, gamma-catenin was generally expressed at lower levels than beta-catenin, was not expressed in ductal cells and was only lightly stained on the lateral membranes of acinar cells. No expression of connexin 32 was observed in ducts but it was significantly expressed in a spotted pattern along the plasma membrane of acinic cells. Connexin 26 showed similar localization to that of connexin 32 but the staining was much more intense. Since these proteins have been reported to play key roles in maintaining homeostasis via control of cell growth, differentiation and death, their analysis in normal salivary tissue will hopefully contribute to the study of salivary tumorigenesis.

Apoptosis-induced and -suppressed cells in salivary gland adenoid cystic carcinoma: correlation with histological growth patterns

OBJECTIVE

It is well known that adenoid cystic carcinoma (ACC) arising from salivary glands shows a correlation between prognosis and histological growth patterns. The aim of the study was to evaluate whether three growth patterns of ACC are related to the distributions of apoptosis-induced and -suppressed tumor cells.

MATERIALS AND METHODS

We examined 77 cases of ACC including tubular (18 cases), glandular (50) and solid (9) patterns. In order to visualize the apoptotic cells, terminal deoxynucleotidyl transferase (TdT)- mediated dUTP-biotin nick end labeling (TUNEL) and avidin-biotin complex staining using Lewis Y (LeY) antibody were applied to paraffin sections. For detection of the apoptosis-suppressed cells, immunohistochemistry employing bcl-2 antibody was utilized.

RESULTS

Apoptosis index (AI) based on the TUNEL-stained specimens were tubular, 7.0; glandular 2.4; solid, 5.1. In tubular type, apoptotic cells were frequently located in the inner tubular layer rather than the outer layer. Solid type had scattered apoptotic cells in the nests. Bcl-2 expression was found in 61% of tubular, 20% of glandular and 22% of solid cases. The localization of bcl-2 protein was noticed in outer tubular cells, and peripheral cells or undifferentiated cells in solid pattern.

CONCLUSIONS

The peculiar distribution of apoptotic cells may result from the various proportions and distinctive arrangement of neoplastic ductal cells and neoplastic myoepithelial cells in ACC. Apoptotic cells and bcl-2 positive apoptosis-suppressed cells may participate in the construction of characteristic histological appearances of ACC.

Human mammary luminal epithelial cells contain progenitors to myoepithelial cells

The origin of the epithelial and myoepithelial cells in the human breast has not been delineated. In this study we have addressed whether luminal epithelial cells and myoepithelial cells are vertically connected, i.e., whether one is the precursor for the other. We used a primary culture assay allowing preservation of basic phenotypic traits of luminal epithelial and myoepithelial cells in culture. The two cell types were then separated immunomagnetically using antibodies directed against lineage-specific cell surface antigens into at best 100% purity. The cellular identity was ascertained by cytochemistry, immunoblotting, and 2-D gel electrophoresis. Luminal epithelial cells were identified by strong expression of cytokeratins 18 and 19 while myoepithelial cells were recognized by expression of vimentin and alpha-smooth muscle actin. We used a previously devised culture medium (CDM4) that allows vigorous expansion of proliferative myoepithelial cells and also devised a medium (CDM6) that allowed sufficient expansion of differentiated luminal epithelial cells based on addition of hepatocyte growth factor/scatter factor. The two different culture media supported each lineage for at least five passages without signs of interconversion. We used parallel cultures where we switched culture media, thus testing the ability of each lineage to convert to the other. Whereas the myoepithelial lineage showed no signs of interconversion, a subset of luminal epithelial cells, gradually, but distinctly, converted to myoepithelial cells. We propose that in the mature human breast, it is the luminal epithelial cell compartment that gives rise to myoepithelial cells rather than the other way around.

Polymorphous low-grade adenocarcinoma of minor salivary glands: a study of 17 cases with emphasis on cell differentiation

AIMS

The diagnosis of polymorphous low-grade adenocarcinoma (PLGA) of salivary glands remains difficult for general surgical pathologists. In an effort to understand the morphological heterogeneity of these neoplasms and facilitate their recognition we reviewed the architectural patterns, cell differentiation and immunohistochemical features of 17 case of PLGA.

METHODS AND RESULTS

There were 11 females and six males with a mean age of 58 years. Twelve tumours were located in the palate, two in the posterior third of the tongue, and one each in the upper lip, buccal mucosa and retromolar triangle. Two patients presented with neck metastases. The mean tumour size was 20 mm (range 6-50 mm). The tumour cells were arranged in five architectural patterns: tubules and small duct-like structures; cords and trabeculae; solid nests; cribriform areas and papillae. Twelve (71%) cases were composed of a combination of tubules and small duct-like structures, cords and trabeculae, and solid nests. Cribriform areas with pseudoluminal spaces were seen in six (35%) cases. A focal papillary pattern was evident in three cases and constituted 40% of the tumour in one. Perineural invasion was seen in 13 cases (76%). All cases studied were positive for CAM5.2, 34BE12, vimentin and S100 protein and showed overexpression of bcl-2 protein. Rb protein was present in 13 cases whereas p53 expression was absent in all cases. The average proliferation index (PI) was 7% (range 1-17%). Three patients developed local recurrences with cervical lymph node metastases but no patient died as result of tumour. No morphological features were found to be prognostic for the development of local recurrences or lymph nodes metastases.

CONCLUSIONS

PLGA is a distinctive neoplasm of salivary glands formed by luminal and nonluminal tumour cells with limited patterns of architectural differentiation. The relative proportion of these cells seems to play a significant role in the morphogenesis of these tumours. The overexpression of the bcl-2 protein and the low PI suggest that inhibition of programmed cell death may be involved in the oncogenesis of PLGA.

Apoptosis is inversely related to bcl-2 but not to bax expression in salivary gland tumours

AIMS

We investigated the extent of apoptosis in 55 benign and malignant salivary gland tumours and its association with the immunohistochemical expression of bcl-2 and bax.

METHODS AND RESULTS

Apoptosis was detected in histological sections by the 3'-end DNA labelling method. bcl-2 and bax protein expression was determined by immunohistochemistry. The frequency of apoptosis was clearly higher in malignant than in benign tumours. In pleomorphic adenomas and Warthin's tumours the average apoptotic index was 0.01% (range 0.00-0.07%) while in the malignant salivary gland tumours it was 0.42% (range 0.00-1.75%). Immunohistochemical bcl-2 expression was observed in all pleomorphic adenomas and Warthin's tumours and in most cases the expression was strong. In malignant tumours, 9/25 cases showed no expression and in the rest of the cases, apart from adenoid cystic carcinomas, the bcl-2 expression was often weak. There were significantly more cases with no or weak bcl-2 positivity in malignant than in benign salivary gland tumours (P = 0.001). There was a statistically significant association between a weak bcl-2 expression and a high frequency of apoptosis (P = 0.02). In contrast to bcl-2, strong bax expression was found in both benign and malignant tumours and was not associated with the frequency of apoptosis.

CONCLUSIONS

The low bcl-2 expression in malignant tumours suggests that down-regulation of its expression might contribute to their higher frequency of apoptosis.