Alterations of beta-catenin pathway in non-melanoma skin tumors: loss of alpha-ABC nuclear reactivity correlates with the presence of beta-catenin gene mutation

Immunohistochemical expression of ?-catenin, E-cadherin, cyclin D1 and c-myc in benign trichogenic tumors

BACKGROUND

beta-catenin gene mutations have been reported in vast majority of pilomatrixomas (PMXs). beta-catenin, a component of the adhesion molecules of the cytoskeleton, is degraded at the cytoplasm. Excess cytoplasmic beta-catenin enters into the nucleus and activates the transcription of several genes encoding c-myc, cyclin D1 and others. Sublocation of beta-catenin has been demonstrated by immunohistochemistry. The aim of this study was to determine the role of beta-catenin-related proteins in various benign trichogenic tumors.

METHODS

We investigated the expression of beta-catenin, E-cadherin, c-myc and cyclin D1 immunohistochemically, and the expression of these molecules were compared between two groups consisting of 12 PMXs and 12 other benign trichogenic tumors (OBTTs).

RESULTS

In PMX group, nuclear and/or cytoplasmic expression of beta-catenin was associated with a loss of membranous expression of E-cadherin (p = 0.002). In OBTT group, a membranous expression of E-cadherin and beta-catenin was observed, and there was a stronger nuclear immunoreactivity of cyclin D1 compared with PMX group (p = 0.006).

CONCLUSIONS

In PMX, nuclear and/or cytoplasmic beta-catenin expression of tumoral cells is not related with beta-catenin-related gene expressions (c-myc or cyclin D1). The molecular behaviour of OBTTs is clearly different from that of PMXs in terms of to E-cadherin and beta-catenin expression.

Differential expression of E-cadherin in metastatic lesions comparing to primary oral squamous cell carcinoma

BACKGROUND

The main cause of treatment failure in resectable oral squamous cell carcinoma (OSCC) is metastasis. E-cadherin (E-cad) plays a principal role in cell adhesion and motility, and is associated with OSCC progression. The aim of this study was to investigate the clinical significance of E-cad expression in OSCC with lymph node metastasis which had radical neck dissection done.

METHOD

Immunohistochemistry was used to detect E-cad expression in normal oral mucosa (NOM) (n = 10), oral precancerous lesions (OPLs) (n = 20), primary OSCC (n = 45), and their paired metastatic lesions (n = 45). E-cad immunoreactivity correlated with the clinicopathologic features.

RESULTS

E-cadherin immunoreactivity was progressively reduced in the NOM followed by OPLs and primary OSCC (58%). It decreased significantly in the advanced stages of OSCC. However, the increase in E-cad immunoreactivity was observed in the majority (60%) of metastatic lesions in relation to primary OSCC. Patients with such increased or positive immunoreactivity of E-cad in metastatic lesions exhibited worse prognosis.

CONCLUSION

The findings suggested a dynamic change in E-cad immunoreactivity during tumorigenesis and metastasis of OSCC. In a multivariate analysis, E-cad immunoreactivity in metastasis lesions (odds ratio 3.74, 95% CI 1.15-14.67; P = 0.040) implied the potential role of mortality predictors for OSCC cases with nodal involvement.

The Wnt-signaling pathway is not implicated in tumorigenesis of Merkel cell carcinoma

BACKGROUND

The Wnt-signaling pathway, involving beta-catenin, apc, and axin, plays a critical role in numerous developmental events. Alterations in the Wnt-signaling pathway have been detected in a wide variety of neoplasms. However, similar aberrations have not been described in Merkel cell carcinoma (MCC). The aim of this study was to determine the status of the Wnt-signaling pathway in MCC.

METHODS

Twelve cases of MCC were tested for the expression of beta-catenin and mutational status of CTNNB1 (gene for beta-catenin), APC, AXIN1, and AXIN2. Genomic DNA extracted from paraffin blocks was subjected to a polymerase chain reaction/single-strand conformation polymorphism analysis and sequencing.

RESULTS

Nuclear accumulation of beta-catenin was observed in only one case (8.3%), as determined by immunochemistry. No mutations were found in CTNNB1, APC, and AXIN2 in all cases, although silent mutations in AXIN1 were detected in three cases.

CONCLUSIONS

We conclude that the Wnt-signaling pathway does not play an important role in tumorigenesis in MCC.

Regulation of bone mass by Wnt signaling

Wnt proteins are a family of secreted proteins that regulate many aspects of cell growth, differentiation, function, and death. Considerable progress has been made in our understanding of the molecular links between Wnt signaling and bone development and remodeling since initial reports that mutations in the Wnt coreceptor low-density lipoprotein receptor-related protein 5 (LRP5) are causally linked to alterations in human bone mass. Of the pathways activated by Wnts, it is signaling through the canonical (i.e., Wnt/beta-catenin) pathway that increases bone mass through a number of mechanisms including renewal of stem cells, stimulation of preosteoblast replication, induction of osteoblastogenesis, and inhibition of osteoblast and osteocyte apoptosis. This pathway is an enticing target for developing drugs to battle skeletal diseases as Wnt/beta-catenin signaling is composed of a series of molecular interactions that offer potential places for pharmacological intervention. In considering opportunities for anabolic drug discovery in this area, one must consider multiple factors, including (a) the roles of Wnt signaling for development, remodeling, and pathology of bone; (b) how pharmacological interventions that target this pathway may specifically treat osteoporosis and other aspects of skeletal health; and (c) whether the targets within this pathway are amenable to drug intervention. In this Review we discuss the current understanding of this pathway in terms of bone biology and assess whether targeting this pathway might yield novel therapeutics to treat typical bone disorders.

Cyclin A and beta-catenin expression in actinic keratosis, Bowen's disease and invasive squamous cell carcinoma of the skin

BACKGROUND

Actinic keratosis (AK) has been defined as a precancerous lesion or an early phase in the evolution of squamous cell carcinoma (SCC) and histological changes seen in the individual cells of an AK are indistinguishable from those seen in SCC, which invade the dermis. Cyclin A is an increasingly utilized proliferation marker that has functions in both S phase (DNA replication) and initiation of mitosis, whereas alterations of beta-catenin, the molecule involved in cell-cell adhesion and in signalling transduction, could promote invasive and proliferative capacities of malignant tumours.

OBJECTIVES

To determine cyclin A and beta-catenin expression pattern in cutaneous SCC and in in situ lesions classified as keratinocytic intraepidermal neoplasia (KIN) and, using traditional terms, as AK and Bowen's disease (BD), and to analyse it in relation to SCC differentiation, diameter and thickness.

METHODS

Immunohistochemical staining was performed on 110 formalin-fixed paraffin-embedded tissue samples with the streptavidin-biotin technique using antibodies to cyclin A and beta-catenin. On histological examination, 53 lesions were diagnosed as AK, 16 as BD and 41 as SCC-11 well differentiated (WD), 16 moderately differentiated (MD) and 14 poorly differentiated (PD). Using KIN classification, 22 lesions were KIN1, 23 were KIN2 and 24 were KIN3. For cyclin A, distribution and labelling index (LI), and for beta-catenin, level of membranous staining and presence of aberrant (nuclear/cytoplasmic) localization were examined.

RESULTS

Diffuse cyclin A presence was observed more frequently in BD than in AK (P < 0.0001) or SCC (P = 0.0002), and in SCC-PD compared with SCC-WD (P < 0.0001) or SCC-MD (P = 0.0003). Differences between KIN3 and KIN2, as well as KIN3 and KIN1 lesions, were statistically significant (P < 0.0001), and the same result appeared when KIN1 and KIN2 cases were grouped and compared with those of KIN3 (P < 0.0001). Cyclin A LI was significantly lower (P < 0.05) in AK than in BD or SCC, but no difference between BD and SCC was found, and LI in BD was even higher than in SCC-WD or SCC-MD, while analysis regarding SCC differentiation and KIN classification revealed the same correlation as for the cyclin A distribution. Reduced or absent beta-catenin membranous staining was found in 90 cases (81.8%), more often in SCC than in AK (P = 0.03) or in AK and BD grouped together (P = 0.02). There was no statistical difference between SCCs of various level of differentiation, or between different KIN grades. Diffuse loss of membranous beta-catenin staining showed 36 lesions (32.7%), more frequently SCC than AK (P = 0.003) or AK and BD grouped (P = 0.006), as well as SCC-PD compared with SCC-WD (P = 0.01) and SCC-MD (P = 0.03), whereas all KIN comparisons remained nonsignificant. Aberrant beta-catenin cellular localization demonstrated 28 lesions (25.5%), most often in the basal or peripheral parts and in the lesions with diffuse beta-catenin loss (P = 0.009), but revealed no correlation with the histological type, SCC level of differentiation or KIN grades. Diffuse loss of membranous beta-catenin staining was found to be significantly more frequent in SCC thicker than 4 mm (P = 0.03), while all other comparisons between cyclin A or beta-catenin with the tumour size remained nonsignificant. Cyclin A LI was higher in cases with diffuse loss of membranous staining (P = 0.001) or with aberrant cellular localization of beta-catenin (P = 0.002).

CONCLUSIONS

Cyclin A LI showed greater difference between AK and BD than between BD and SCC, suggesting that increased proliferation (measured by cyclin A LI) characterizes progression of in situ lesions from AK to BD, whereas reduced beta-catenin expression separates more clearly SCC from the in situ lesions. Diffuse pattern of loss of membranous beta-catenin staining correlated better with the type of lesion, SCC differentiation and tumour size than reduced expression in general or aberrant cellular localization of beta-catenin. KIN classification does not seem to be supported by our findings, except when KIN1 and KIN2 lesions (in situ, partial thickness) are grouped.

The E-cadherin–β-catenin complex and its implication in lung cancer progression and prognosis

The E-cadherin–β−catenin complex plays a pivotal role in epithelial cell–cell adhesion and in the maintenance of differentiated adult epithelia. Perturbation of its expression or function is widely involved in tumor progression and metastasis. Recent years have seen a rapid expansion in the understanding of the biology and the clinical relevance of the E-cadherin adhesion complex in human lung cancer. During human lung cancer progression genomic, transcriptionnal and post-transcriptionnal alterations of the E-cadherin–β-catenin adhesion system are implicated and comprise deletion of the chromosomic region 3p21 that comprise the locus of the gene encoding β-catenin, transcriptionnal downregulation of E-cadherin, cytoplasmic redistribution, phosphorylation of both proteins and proteolysis of E-cadherin. E-cadherin-inactivating mutations and oncogenic-activating mutation of β-catenin are not reported.

Drebrin, an Actin-Binding, Cell-Type Characteristic Protein: Induction and Localization in Epithelial Skin Tumors and Cultured Keratinocytes

Isoform E2 of drebrin, an actin-binding protein originally identified in neuronal cells, has recently been identified in diverse non-neuronal cells, mostly in association with cell processes and intercellular junctions. Here, we report on the presence of drebrin in normal human skin, epithelial skin cancers, and cultured keratinocytes. Keratinocytes of normal epidermis contain almost no drebrin but the protein is readily seen in hair follicles. By immunohistochemistry and immunoblot, basal cell carcinomas (BCC) are rich in drebrin, and confocal laser scanning and immunoelectron microscopy show accumulation at adhering junctions, in co-localization with actin and partially with plaque proteins. In squamous cell carcinomas, keratoacanthomas, and in epidermal precancers, drebrin is heterogeneously distributed, appearing as mosaics. Primary keratinocyte cultures contain significant amounts of drebrin enriched at adhering junctions. When epithelium-derived cells devoid of drebrin are transfected with drebrin-enhanced green fluorescent protein, constructs accumulate in the cell periphery, and immunoprecipitation shows complexes with actin. During epidermal growth factor induced formation of cell processes, drebrin retains this junction association, as observed by live cell microscopy. Our results suggest novel functions of drebrin such as an involvement in cell-cell adhesion and tumorigenesis and a potential value in diagnosis of BCC.

Desmoid tumor with ossification in chest wall: possible involvement of BAMBI promoter hypermethylation in metaplastic bone formation

A rare case of desmoid-type fibromatosis with focal metaplastic bone in the chest wall suggested that enhanced responsiveness to BMP signaling by decreasing BAMBI expression through promoter hypermethylation plays a crucial role in the formation of metaplastic bone.

INTRODUCTION

Desmoid-type fibromatosis, originating from mesenchymal cells with myofibroblastic features, is a locally aggressive and frequently recurring infiltrative lesion. One such sporadic case with metaplastic ossification in the chest wall is presented.

MATERIALS AND METHODS

A 43-year-old man was referred to the hospital with a gradually enlarging hard mass in the left anterolateral chest wall. A thoracotomy was carried out, and histopathological specimens were used for immunohistochemical, genetic, and methylation studies.

RESULTS

Accumulation of altered beta-catenin associated with a somatic heterozygous activating mutation in codon 41 was detected in the typical desmoid-type fibromatosis and at the ossifying focus. Among factors related to bone formation and the classical wnt-beta-catenin signaling pathway, BMP and activin membrane-bound inhibitor (BAMBI) expression was specifically downregulated at the ossifying focus. Hypermethylation of the BAMBI promoter was observed in microdissected tissue from the ossifying focus but not in that from the typical desmoid-type fibromatosis.

CONCLUSIONS

Because both BMP and classical Wnt/beta-catenin/LEF1 signaling cooperatively and mutually induce differentiation of mesenchymal cells into osteoblastic cells and promote bone formation, the epigenetic event leading to the enhanced responsiveness to BMP signaling may play a crucial role in the formation of metaplastic bone.

Elevated expression of E-cadherin and alpha-, beta-, and gamma-catenins in metastatic lesions compared with primary epithelial ovarian carcinomas

E-cadherin and catenins play key roles in cell adhesion and motility. Little is known about the changes in expression of these molecules in the progression of ovarian carcinomas. In the present study, the immunohistochemical expression of E-cadherin and alpha-, beta-, and gamma-catenins was examined in 77 cases of ovarian carcinoma. In addition, the expression of these molecules was evaluated in 26 matched pairs of primary and metastatic lesions of advanced ovarian carcinomas. Of the 77 primary lesions, positive staining for E-cadherin and alpha-, beta-, and gamma-catenin was observed in 75 (97%), 63 (82%), 71 (92%) and 57 (74%) cases, respectively. Positivity for E-cadherin and alpha-, beta-, and gamma-catenin was significantly decreased in stage III and IV tumors compared with stage I and II tumors, suggesting that expression of the cadherin-catenin complex is reduced with the advancing stages of a tumor. Interestingly, expression of E-cadherin and alpha-, beta-, and gamma-catenin in the lesions of peritoneal dissemination was significantly increased compared with the primary lesions. These findings suggest that expression of the cadherin-catenin complex changes markedly and that reexpression may occur during the peritoneal dissemination of ovarian carcinoma cells.

Arsenite maintains germinative state in cultured human epidermal cells

Arsenic is a well-known carcinogen for human skin, but its mechanism of action and proximal macromolecular targets remain to be elucidated. In the present study, low micromolar concentrations of sodium arsenite maintained the proliferative potential of epidermal keratinocytes, decreasing their exit from the germinative compartment under conditions that promote differentiation of untreated cells. This effect was observed in suspension and in post-confluent surface cultures as measured by colony-forming ability and by proportion of rapidly adhering colony-forming cells. Arsenite-treated cultures exhibited elevated levels of beta1-integrin and beta-catenin, two proteins enriched in cells with high proliferative potential. Levels of phosphorylated (inactive) glycogen synthase kinase 3beta were higher in the treated cultures, likely accounting for the increased levels of transcriptionally available beta-catenin. These findings suggest that arsenic could have co-carcinogenic and tumor co-promoting activities in the epidermis as a result of increasing the population and persistence of germinative cells targeted by tumor initiators and promoters. These findings also identify a critical signal transduction pathway meriting further exploration in pursuit of this phenomenon.