Vol 69, No 1 (2010)
Review article
Published online: 2010-03-09
The myoepithelial cell: its role in normal mammary glands and breast cancer
Folia Morphol 2010;69(1):1-14.
Abstract
Mammary gland epithelium is composed of an inner layer of secretory cells (luminal)
and an outer layer of myoepithelial cells (MEC) bordering the basal lamina
which separates the epithelial layer from the extracellular matrix. Mature MECs
morphologically resemble smooth muscle cells; however, they exhibit features
typical for epithelial cells, such as the presence of specific cytokeratin filaments.
During lactation, secretory cells synthesize milk components, which are collected
in alveoli and duct lumen, and transported to the nipple as a result of MEC
contraction. Although the induction of MEC contraction results from oxytocin
action, also other, still unknown auto/paracrine mechanisms participate in the
regulation of this process. As well as milk ejection, MECs are involved in mammary
gland morphogenesis in all developmental stages, modulating proliferation
and differentiation of luminal cells. They take part in the formation of extracellular
matrix, synthesizing its components and secreting proteinases and their inhibitors.
In addition, MECs are regarded as natural cancer suppressors, stabilizing
the normal structure of the mammary gland, they secrete suppressor proteins
(e.g. maspin) limiting cancer growth, invasiveness, and neoangiogenesis. The
majority of malignant breast cancers are derived from luminal cells, whereas
neoplasms of MEC origin are the most seldom and usually benign form of breast
tumours. MECs are markedly resistant to malignant transformation and they are
able to suppress the transformation of neigh boring luminal cells. Therefore,
a deeper insight into the role of MECs in the physiology and pathology of mammary
glands would allow a better understanding of cancerogenesis mechanisms
and possible application of specific MEC markers in the diagnosis and therapy of
breast cancer.
Folia Morphol 2010; 69, 1: 1-14
Folia Morphol 2010; 69, 1: 1-14
Keywords: myoepithelial cellmammary glandmilk ejectionbreast cancermyoepithelial tumours
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