EXPRESSION OF INTEGRIN SUBUNITS IN THE - HUMAN INFANT BREAST CORRELATES WITH MORPHOGENESIS AND DIFFERENTIATION

Integrins are widely expressed on normal tissues and their function is considered critical directly or indirectly with the control of cell g rowth and differentiation. Also, they are likely to play a crucial rol e in cell-matrix interactions during development. As the human breast develops after birth, it provides a rare opportunity in which to study human organogenesis. We have examined the distribution of integrins i n the human infant breast with the aim of elucidating the possible rol e of these molecules in morphogenesis and differentiation. Necropsy br east specimens from six male and eight female infants, ranging in age from 1 day to 9 months, were used in this study. Cryostat sections wer e stained by the avidin-biotin complex technique, using a panel of mon oclonal antibodies (MAbs) which recognize beta(1), alpha(2), alpha(6), beta(4), alpha(v), and alpha(v) beta(3) integrin chains, which are ca ndidate molecules for a role in mammory morphogenesis. MAbs to beta(1) (DH12) and alpha(2) (HAS3) showed positive membrane and cytoplasmic s taining of basal cells and luminal epithelial cells. In addition, posi tive staining for the beta(1) integrin chain was found on fibroblasts. A MAb which recognizes the alpha(6) chain (MP4F10) showed positive st aining of the basal cells and heterogeneous staining of the luminal ep ithelial cells, whilst beta(4) chain (439-9B) showed positive staining in the basement membrane domain of the basal cells with no staining o f the luminal epithelial cells. There was a positive correlation betwe en the intensity of expression and the structural development of the d uctal system, with integrin expression reduced or absent in the end bu ds and lateral buds. These data provide evidence that some integrin mo lecules are expressed in a pattern that correlates with the morphologi cal and functional differentiation of the normal mammary gland. Change s in the expression and function of integrins may have an inductive ro le in the development of the normal mammary gland.