Cadherins, Catenins and Associated Proteins in Normal Epidermis, Basal Cell Carcinoma and Other Cutaneous Tumours: An Immunohistochemical Study

Background 1: In carcinoma, the detachment of cancer cells from a primary tumour site as a result of disorganised cell-cell association is a critical step leading to tumour invasion and metastasis. Adherens junctions (AJ) are multiprotein complexes localised at intercellular and cell-matrix contacts, mediating the adhesion of cells to each other or to matrix structures. The association of actin filaments with the actin-binding proteins enables them to serve a variety of functions including the stability of cell shape, mechanical support, cell-cell adhesion and cell motility. The latter is thought to be driven largely by the polymerisation of actin monomers into filaments near the plasma membrane. The maintenance of epithelial differentiation requires proper formation of cell-cell junctions where destabilisation of such junctions allows the initiation of the invasive process and the progression of carcinoma. Because there is evidence that down- regulation or complete loss of the major AJ component, E-cadherin, occurs in association with human epithelial cancers, it has been suggested that E-cadherin could play a role as an invasion-suppressor molecule. Aim 1: • To investigate the cellular distribution of AJ components (E- and P-cadherin, A- and beta-catenin and associated proteins) in the normal human epidermis and in a variety of skin tumours including basal cell carcinoma (BCC), pilomatrixoma (PMX), squamous cell carcinoma (SCC) and precursor lesions and melanocytic lesions. Also to assess whether the decrease in membranous distribution of the AJ major components, particularly cadherins and beta-catenin, in human skin cancer progressed further in de-differentiation tumours. • To investigate the possible co-localisation of E- and P-cadherin in the basal and the first layer of suprabasal cells of the human normal epidermis and BCC with respect to the hypothetical stepwise loss of cadherins by tumour cells. • To characterise the overall structure of AJ in BCC versus the normal epidermis and to investigate the association of AJ components with the actin-based cytoskeleton. Also to examine the patterns of distribution of filamentous actin in the normal epidermis and BCC and how actin bundles are arranged in the tumour cells with respect to their shape, migratory behaviour and thus invasiveness. • To compare the changes in the abundance and distribution of actin and the expression of E-, P-cadherin and p-catenin in nodular and infiltrative BCC with those in migrating keratinocytes in vitro. Methods 1: Immunoperoxidase and double immunofluorescent staining. Cell culture. Aim 2: • To investigate whether any decrease in membrane beta-catenin expression in epidermal tumours is accompanied by redistribution to the cell nucleus secondary to the activation of the Wnt pathway. • To investigate the expression of the transcription factor Gli-1 in normal skin and BCC as there is evidence that the activation of the Shh/Ptc-Smo signalling pathway plays a key role in BCC development. Methods 2: Immunoperoxidase staining. Aim 3: To grow different subtypes of BCC tumours in vitro. (Abstract shortened by ProQuest.)