Comparative immunohistochemical localization of fibronectin and actin in human breast tumor cells in vivo and in vitro

Different mitogenic and phenotypic responses of human breast epithelial cells grown in two versus three dimensions

Human breast epithelial cells, derived from fibroadenomas, were cultured under conditions promoting growth in two-dimensions (2D) as monolayers using the collagen-coated dishes and in three-dimensions (3D) inside the collagen gel matrix. Both epidermal growth factor (EGF) and cortisol (F) were required for maximal stimulation in 3D growth, but only cortisol was required for 2D growth. The growth stimulation of exogenously added type IV collagen was no greater than that of type I as a substrate in both the 2D and 3D growth. Immunocytochemical staining, using a polyclonal actin antibody, showed homogeneous staining in all cells in 2D monolayers, whereas more restricted distribution was observed in 3D outgrowths in the collagen gel matrix. The same cells, when cultured in 2D vs 3D, elicit different responses and the original phenotypes may be better maintained in 3D.

In vivo demonstration of cytoplasmic fibronectin in human breast carcinomas

The distribution pattern of fibronectin in 24 invasive human breast carcinomas has been studied using the indirect immunoperoxidase technique. A positive cytoplasmic staining reaction was observed in 16 tumours. Well-differentiated carcinomas showed weak or no staining, whereas all moderately or poorly differentiated carcinomas and one signet ring cell carcinoma contained fibronectin positive tumour cells with moderate or strong staining. The staining intensity was positively correlated to degree of anaplasia with the exception of two moderately differentiated duct carcinomas and the two medullary carcinomas, which were only slightly positive. Non-attached independently growing tumour cells stained more intensely than tumour cells in clusters. Pericellular fibronectin was found in only one carcinoma of medullary type. In normal ducts and glands it was seen at the stromal-epithelial junction corresponding to the basement membrane, around myoepithelial cells and along the luminal border. The results support the findings of several in vitro investigations that breast tumour cells synthesize fibronectin. It also suggests that cytoplasmic fibronectin expression might be an indicator of tissue differentiation in non-solidly growing invasive duct carcinomas of the human mammary gland.

Stromal cells of the fibroadenoma of the human breast. An immunohistochemical and ultrastructural study

Fourteen fibroadenomas of the human breast were examined by light and electron microscopy, and by immunohistochemistry for actin. They were classified into 3 groups according to their stromal patterns; myxoid, fibrous-cellular and sclerotic. Actin immunohistochemistry revealed that the stromal areas were strongly positive in the fibrous-cellular group and weakly positive in the myxoid and sclerotic groups. By electron microscopy the stromal cells in most cases of the myxoid and fibrous-cellular groups were fibroblasts, containing varying amounts of microfilaments, 5-7 nm in diameter (actin type filaments). However, a dense body was not usually present suggesting these stromal cells were variants of myofibroblasts. The amount of microfilaments in fibroblasts was greater in the fibrous-cellular group than in the myxoid group. This was consistent with the results of actin immunohistochemistry. In 3 cases of the fibrous-cellular group peculiar structures simulating Z-lines of striated muscles were noted in some stromal cells. Since no myosin filaments were detected, they were regarded as intermediate structures between Z-lines of striated muscles and dense bodies of smooth muscles. In the sclerotic group, stromal fibroblasts were sparse and had fewer organelles.