Cell-type related and spatial variation in the expression of integrins in cutaneous tumors

Adhesion Molecules in Non-melanoma Skin Cancers: A Comprehensive Review

Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are the most frequently diagnosed cancers, generating significant medical and financial problems. Cutaneous carcinogenesis is a very complex process characterized by genetic and molecular alterations, and mediated by various proteins and pathways. Cell adhesion molecules (CAMs) are transmembrane proteins responsible for cell-to-cell and cell-to-extracellular matrix adhesion, engaged in all steps of tumor progression. Based on their structures they are divided into five major groups: cadherins, integrins, selectins, immunoglobulins and CD44 family. Cadherins, integrins and CD44 are the most studied in the context of non-melanoma skin cancers. The differences in expression of adhesion molecules may be related to the invasiveness of these tumors, through the loss of tissue integrity, neovascularization and alterations in intercellular signaling processes. In this article, each group of CAMs is briefly described and the present knowledge on their role in the development of non-melanoma skin cancers is summarized.

Basal cell carcinoma: cell of origin, cancer stem cell hypothesis and stem cell markers

Cancer stem cells have recently been described in several high-grade neoplasms. It is still unclear if they also occur in cutaneous malignancies. Cancer stem cells are not identical with somatic stem cells. The presence of tumour stem cells in a neoplasm does not in itself equal that the tumour derives from a somatic stem cell. A cell originally lacking stem cell characteristics could also acquire those features during the course of carcinogenesis and then becomes the clonal founder cell of a tumour. Basal cell carcinoma (BCC) is the most common cutaneous malignancy. A plethora of various stem cell markers has been applied to study its cellular origin. Intriguingly, the anatomical origin of BCC is still uncertain. This review will discuss the various stem cell markers used in BCC and the cellular origin of this tumour, and touches briefly on the possibility of cancer stem cells in BCC. If BCC or other skin cancers harbour tumour stem cells, these cells could be specifically targeted, making use of specific cell surface molecules such as receptor proteins. Novel drugs directed against those receptor proteins could replace currently available shotgun approaches including imiquimod.

The contribution of epidermal stem cells to skin cancer

Tumors arising from the skin are of multiple phenotypes, with differing degrees of malignant potential. In mouse models of skin carcinogenesis, tumors of squamous phenotype are the most common; however, human disease indicates that multiple phenotypes may arise from a common pool of stem cells that are then influenced by epigenetic factors. The use of transgenic and knockout gene technologies with mice is unraveling some of the specific genes regulating fate determination in stem cells other than squamous lineage, including basal cell carcinoma and sebaceous adenomas. The following review examines the evidence for the stem cell origin of epidermal tumors and the contribution of some specific gene families toward stem cell fate decisions during epidermal tumor progression.

Microarray profiles of human basal cell carcinoma: Insights into tumor growth and behavior

PURPOSE

Basal cell carcinoma (BCC) is the most common human neoplasm. Much interest lies in determining the genetic basis of BCC to explain the unique locally invasive phenotype and infrequent metastatic behavior of these skin tumors.

OBJECTIVE

We sought to examine a gene expression profile for BCC to elucidate new molecules responsible for its unique growth characteristics.

METHODS

We analyzed gene expression patterns of 50 BCC tumors using spotted cDNA microarrays of 1718 characterized human genes related to cancer and immunity. This is the largest and most comprehensive gene expression study ever performed for BCC. Nodular and sclerosing histological subtypes of BCC were examined and compared to normal control skin. After statistical filtering, 374 significantly dysregulated genes were sorted by hierarchical clustering to determine trends of gene expression and similarities between patient gene expression profiles.

RESULTS

A total of 165 upregulated genes and 115 downregulated genes were identified. These covered a range of categories, including extracellular matrix, cell junctions, motility, metastasis, oncogenes, tumor suppressors, DNA repair, cell cycle, immune regulation and angiogenesis. Clusters of genes were either commonly dysregulated across the 50 patient sample, or selectively affected in subsets of tumors. Histological subtypes were not distinguishable by hierarchical clustering. Many of the genes elucidated, including collagen type IV subunits and other novel candidates, possess functions related to extracellular matrix remodeling and metastasis.

CONCLUSION

These results suggest a gene profile which may explain the invasive growth yet rarely metastatic behavior of BCC. The genes identified may also be potential targets for therapeutics aimed at further controlling invasiveness and local destruction of BCC.

CD44 and melanocytic tumors: a possible role for standard CD44 in the epidermotropic spread of melanoma

CD44 is a polymorphic family of cell membrane glycoproteins that mediate cell-matrix and cell-cell interactions involved in the mechanisms of tumor invasion and metastasis, and are subject to differential regulation during normal and malignant cell growth. We have investigated immunohistochemically the expression of CD44S and the variant isoforms CD44v3 and CD44v6 in paraffin-embedded tissue from 5 Spitz nevi, 3 compound melanocytic nevi, 2 blue nevi, 6 primary melanomas, 15 cutaneous metastases (three epidermotropic, nine dermal and three ulcerated) and 10 lymph node metastases of melanoma. Melanocytes were extensively positive for CD44S in primary melanomas and benign melanocytic proliferations. Among 15 cases of cutaneous metastases of melanoma, the three epidermotropic metastases, as well as one of the three ulcerated ones were positive for CD44S. CD44S expression was diminished or totally absent in six of the nine dermal metastases, in two of the ulcerated metastases and in seven of the ten lymph node metastases. CD44v3 and CD44v6 melanocytic expression was absent in all the lesions studied. According to our results, selective retention of CD44S expression by melanocytes in epidermotropic metastases of melanoma seems to indicate that preservation of CD44S may contribute to the intraepidermal spread of melanoma.