Altered CD40 and E-cadherin expression--putative role in oral lichen planus.

BACKGROUND: Oral lichen planus (OLP) is characterized among other features by apoptosis of basal keratinocytes. To identify potential regulatory mechanisms associated with basal cell apoptosis in OLP, we investigated the expression of CD40, CD40 ligand (CD40L), CD44 and epithelial (E)-cadherin. METHODS: Biopsies from 22 patients with OLP were investigated by immunohistochemistry for detection of CD40, CD40L, E-cadherin, CD44, Laminin-5 and Collagen IV, double-labelling for CD40 and CD3, and in situ mRNA hybridization for CD40 and CD40L. RESULTS: In actively diseased areas of OLP lesions, basal keratinocytes did not express CD40 and were focally E-cadherin-negative, in contrast to non-diseased areas and normal oral mucosa. Demonstration of intraepithelial T cells expressing CD40 and CD40L, indicates a potential role in inflammatory cell responses involved in the disease process of OLP. CONCLUSION: T cells may orchestrate inflammatory cell responses in OLP via CD40-CD40L interactions. As basal keratinocytes downregulate CD40, they may escape CD40-CD40L-induced apoptosis in OLP. On the other hand, loss of E-cadherin expression may contribute to epithelial basal cell destruction and T-cell migration into the epithelial compartment in OLP.

Loss of BCL-2 in the progression of oral cancer is not attributable to mutations.

BACKGROUND: BCL-2 and BAX are important in the regulation of apoptosis. There have been reports of loss of BCL-2 in basal cells of oral epithelial dysplasia (OED) and in oral squamous cell carcinoma (OSCC), and suppression of BAX in poorly differentiated OSCC. AIM: To investigate whether loss of BCL-2 in OED and OSCC, and of BAX in poorly differentiated OSCC could be attributed to BCL-2 and BAX mutations. METHODS: Immunohistochemistry and in situ hybridisation were used to confirm BCL-2 and BAX expression. DNA was extracted from archival samples of OED (n = 22) and OSCC (n = 28). The connective tissue part from each section was collected separately and used as the normal reference. RESULTS: No mutations were detected in BCL-2 or BAX that could explain their aberrant expression at the mRNA and protein levels in OED and OSCC. The reported A/G polymorphism at codon 7 of BCL-2 was detected in 18 of 50 samples and a novel C/T polymorphism at codon 100 was detected in three of 50 samples. CONCLUSIONS: No mutations were found that could explain loss of BCL-2 in oral dysplasia and carcinoma. An unreported C/T polymorphism in BCL-2 was detected. Downregulation of BCL-2 in OED and OSCC may be the result of transcriptional regulation.

Cell death regulation in oral squamous cell carcinoma: methodological considerations and clinical significance.

In the last three decades, more work has been done on apoptosis and its role in the pathogenesis of many diseases including cancer. In almost all instances of cancer, dysregulation of cell death (apoptosis) and cell proliferation have been found to play a major role in tumourigenesis. A lot of progress has been made on understanding the molecular basis of apoptosis and its regulatory mechanisms. This review focuses on current knowledge on the regulation of apoptosis in oral squamous cell carcinoma, current methodologies and methodological consideration in estimation of cell death in tissue sections and the clinical significance of apoptosis related molecules in progression of oral squamous cell carcinoma.

CD40, CD154, Bax and Bcl-2 expression in Sjögren's syndrome salivary glands: a putative anti-apoptotic role during its effector phases.

Sjögren's syndrome (SS) is an autoimmune rheumatic disorder characterized by chronic lymphocytic infiltration and decreased secretion in the salivary glands (SGs). For some time, apoptosis has been suggested to constitute the major mechanism for acinar epithelial destruction during the effector phases; however, this is still controversial. We have recently demonstrated that despite the expression of Fas and FasL, the incidence of apoptosis is not increased in SS patients compared with control individuals. Our aim was therefore to further evaluate the expression of the pro- and anti-apoptotic Bax and Bcl-2 proteins. CD40 and CD154 expression was also investigated, as CD40 ligation has been suggested to protect cells from Fas-mediated apoptosis. Immunohistochemical staining was performed on SG tissue from primary and secondary SS patients, a group of patients with non-SS-related degenerative changes as well as on healthy control individuals. The frequency of stained cells in the foci of infiltrating mononuclear cells (IMCs) and in the acinar and ductal epithelium was determined. We found the expression of Bcl-2 but rarely Bax in SS SG IMCs. Bcl-2 in epithelial cells was sparse, while Bax expression occurred frequently and with no significant difference between the patient groups. CD40 and CD154 expression was high among SS IMCs, while CD40 levels were slightly decreased in SS epithelium compared with controls. Elevated CD154 expression was found in SS epithelium, being significantly increased in the ducts. In conclusion, our study further supports the hypothesis about apoptosis resistance among SS focal IMCs and suggests a putative protective role of CD40 ligation in SS SG epithelium.

Maintained CD40 and loss of polarised CD40 ligand expression in oral squamous cell carcinoma.

BACKGROUND: CD40 and its ligand (CD40L) are involved in immune response and inhibition or induction of apoptosis in different tissues. Little is known about CD40 and CD40L in oral squamous cell carcinomas (OSCC). MATERIALS AND METHODS: CD40 and CD40L were immunohistochemically evaluated in fresh-frozen samples of OSCC (n = 24) and normal oral epithelium (OE, n = 10). RESULTS: A high proportion of OE-cells expressed CD40 (> 80%) and CD40L (> 90%) in the basal compartment compared to less than 1% CD40-positive and 1% CD40L-positive cells in the suprabasal cell layer, reflecting a zonal distribution. In well-differentiated and moderately-differentiated OSCC, there was a less pronounced zonal distribution of CD40 and a marked loss of CD40L compared to OE (p < 0.05). Poorly-differentiated OSCC maintained CD40 and markedly lost CD40L compared to OE (p < 0.05). Double immunostaining for CD40L and laminin in OE showed a basement membrane associated localisation of CD40L. CONCLUSION: In OSCC, loss of polarised expression of CD40L and maintained expression of CD40 might be involved in tumourigenesis and immune evasion.

Apoptosis and expression of Bax and Bcl-2 in snuff- and non-snuff associated oral squamous cell carcinomas.

BACKGROUND: Oral squamous cell carcinoma (OSCC) is etiologically linked to tobacco and alcohol consumption. A higher frequency of p53 gene mutations was reported in snuff (toombak)-associated OSCC from the Sudan versus those from non-users (Ibrahim et al., 1999, 10). MATERIALS AND METHODS: OSCC from Sudanese toombak users (n = 13) and non-users from the Sudan (n = 6) and Norway (n = 24) were analysed for bax, bcl-2 and Ki-67 immunohistochemically. Apoptosis was evaluated by the TUNEL method. The OSCC from the Sudan had previously been studied for p53 gene mutations. RESULTS: We found a higher apoptotic rate and a higher bax expression in OSCC from Norway compared with those from the Sudan (p < 0.05) irrespective of toombak use. No significant differences were detected in apoptosis, bax, bcl-2 and Ki-67 in OSCC from the Sudan in relation to toombak use or p53 gene status. CONCLUSION: In OSCC, apoptosis was associated with bax expression and was unaffected by p53 gene status or toombak use in OSCC from the Sudan.

Oral squamous cell carcinoma is associated with decreased bcl-2/bax expression ratio and increased apoptosis.

Expression of bcl-2 and bax and apoptosis were studied in fresh frozen samples of normal oral epithelium (OE, n = 7) and oral squamous cell carcinomas (OSCC, n = 16) by immunohistochemistry and the TUNEL method. In OE, bcl-2 was expressed in both basal (96.6% +/- 2.3% [mean +/- SD]) and suprabasal (91.8% +/- 6.2%) compartments. In OSCC, compared with OE, there was a marked reduction of bcl-2-positive cells in the basal part, and in the central parts of well-differentiated (33.0% +/- 19.7%, P < .001) and moderately differentiated (6.1% +/- 4.6%, P < .001) and also in poorly differentiated (1.9% +/- 0.2%, P < .001) tumors. More cells expressed bax in the suprabasal layer of OE (65.6% +/- 9.9%) and central parts of OSCC than in the basal layer of OE (19.1% +/- 4.1%) and basal parts of OSCC. A higher proportion of cells expressed bax in the central part of well-differentiated OSCC (74.3% +/- 8.2%) than in poorly differentiated OSCC (24.9% +/- 9.7%, P < .001). Apoptotic cell death was more pronounced in OSCC (1.5% +/- 0.9%) than in OE (0.4% +/- 0.1%, P < .05). We conclude that, in OSCC, compared with OE, there is a decreased bcl-2 expression, a lowered bcl-2/bax ratio and increased apoptosis. The expression of bax correlates with histological tumor grading in oral squamous cell carcinoma.

Suppression of Fas receptor and negative correlation of Fas ligand with differentiation and apoptosis in oral squamous cell carcinoma.

Apoptosis and the expression of Fas receptor (Fas) and Fas ligand (FasL) were studied in 8 samples of normal oral mucosa (OM) and in 19 oral squamous cell carcinomas (OSCC) by immunohistochemistry and the TUNEL method. Fas was detected in less than 2% of cells in OSCC compared with 84.3+/-9.0% of cells in the basal layer in OM. FasL was found to be highly expressed in poorly differentiated lesions (90.9+/-3.6%), and in cells of both the basal (88.3+/-4.3%) and central (85.3+/-5.7%) parts of moderately differentiated lesions, whereas in well-differentiated (WD) lesions expression was considerably lower in both basal (42.7+/-4.1%) and central (11.5+/-2.4%) parts. In normal OM FasL was primarily detected in cells of the basal layer, but in a high proportion of cells (84.9+/-4.3%). Apoptotic cell death was greater in OSCC (1.6+/-0.6%) than in OM (0.6+/-0.2%, P<0.05) and was most pronounced in the central part of WD OSCC (2.3+/-0.5%). Our results show that Fas is expressed in low quantities in OSCC and that FasL expression correlates negatively with degree of differentiation and apoptosis in OSCC.