Hemidesmosomes, collagen VII, and intermediate filaments in basal cell carcinoma

We have undertaken an analysis of hemidesmosomes (HD) and their associated structures, intermediate filaments (IF) and anchoring fibrils (AF), in various types of basal cell carcinoma (BCC). Using a combination of electron microscopy and immunofluorescence microscopy we show that there is a correlation between the loss of HD and tumor type (i.e., in solid and infiltrative BCC hemidesmosomes are present, sometimes in reduced numbers), while there appears to be a lack of hemidesmosomes in cells of sclerosing specimens. Moreover, even though there is a loss of cytoplasmic constituents of the HD in sclerosing forms of BCC, this is not the case with regard to collagen VII, a component of AF, which are normally associated with the extracellular side of the HD. Collagen VII is localized to the basement membrane zone of tumor cells in the absence of the cytoplasmic constituents of HD. Furthermore, deposits of collagen VII occur in the connective tissue close to tumor cell populations in all but one of the BCC specimens we analyzed. In addition to modifications in HD and AF in BCC tissue, there are changes in the cytoskeletal elements of both tumor cells and the normal appearing epidermis that overlies tumor areas. In sclerosing BCC microfilaments are commonly observed along the basal portions of tumor cells where they abut the connective tissue. IF are often found interacting with these microfilaments. Indirect immunofluorescence analysis of tumor tissue using a monoclonal keratin antibody preparation, AE1, which in normal epidermis stains basal cells, reveals that AE1 antibodies only weakly stain tumor cells. Moreover, in the epidermis that overlies tumor cell regions AE1 antibodies stain suprabasal cells and not basal cells. This change in staining pattern generated by AE1 antibodies appears to depend upon the proximity of tumor cells. These results are discussed in relation to the organization of the HD and its associated AF and IF. The possibility that HD, IF, and AF antibody preparations may be of diagnostic use is raised.