The role of myoepithelial cells in the morphogenesis of induced mammary tumours

Establishment and characterization of a novel human myoepithelial cell line and matrix-producing xenograft from a parotid basal cell adenocarcinoma

Myoepithelial cells exert important paracrine effects on epithelial morphogenesis and mitogenesis through direct cell-cell interactions and through synthesis of a basement membrane extracellular matrix. To study these effects further, this study established the first immortalized human myoepithelial cell line, HMS-1, and transplantable xenograft, HMS-X, from the rare parotid basal cell adenocarcinoma. The cell line exhibited a fully differentiated myoepithelial phenotype and the xenograft exhibited the rare property of accumulating an abundant extracellular matrix composed of both basement membrane and nonbasement membrane components with the latter predominating. With HMS-1 as a feeder layer, dramatic and specific induction of epithelial morphogenesis (spheroid formation) occurred with selected normal epithelial and primary carcinoma target cells. HMS-1 and HMS-X provide distinct advantages over the conventional murine matrices in existence. They will be invaluable in future studies of human tumor-myoepithelial and matrix interactions important for tumor cell growth, invasion, and metastasis.

The myoepithelial cell: embryology, function, and proliferative aspects

Myoepithelial cells form an integral part of the secretory and ductular portion of most glands. They share a common origin with lumenal epithelial cells and influence proliferation and differentiation of developing terminal glandular buds by producing a scaffold of basement membrane proteins. Their contractile capacity, controlled by hormonal and neural mechanisms, plays an important role in propulsion of secretions. Furthermore, myoepithelial cells maintain glandular structural integrity and transport metabolites to secretory cells. The advent of modern immunochemistry made identification of specific myoepithelial cell markers possible which facilitated studies on their presence and behavior in disease processes. Although the significance of many myoepithelial alterations is speculative, some have proved valuable in determining the histogenesis of glandular lesions.

Ultrastructure of mammary carcinomas in male rats induced by 7,12-dimethylbenz(a)anthracene

The morphology of mammary tumors induced by 7,12-dimethylbenz(a)anthracene in male rats was investigated by light and electron microscopy. All tumors induced in male rats were carcinomas with prominent epithelial growth which shows a medullary or cribriform appearance. Neither mammary dysplasias nor fibroadenomas were induced in male rats. Foci of adenoid cystic carcinoma were encountered in some parts of tumors. Papillary and/or tubular patterns, which have been observed frequently in mammary carcinomas in female rats, were not prominent histologic features in male rats. Secretory activity was not remarkable. The morphology of mammary carcinomas in male rats was unchanged in primary and transplanted tumors under various hormonal conditions. This finding supports our previously published results that the mammary carcinomas in male rats are hormone-independent, although our previous biochemical study revealed that the tumors contain both estrogen and estrogen-dependent progesterone receptors.