CORRELATION OF ALPHA-2-BETA-1 INTEGRIN EXPRESSION WITH HISTOLOGICAL TYPE AND HORMONAL RECEPTOR STATUS IN BREAST CARCINOMAS

Interactions between cells and extracellular matrix are mediated in pa rt by a family oi alpha beta heterodimeric molecules known as integrin s. Immunohistochemical studies have shown that benign hyperelastic/neo plastic mammary epithelium expressed high levels of alpha 2 beta 1 col lagen/laminin receptor. In contrast, malignant cells of breast carcino ma exhibited marked diminuition or loss of the alpha 2 beta 1 integrin . A correlation has been suggested between the loss of the alpha 2 bet a 1 expression and the increased invasiveness of neoplastic cells. Thi s study investigated the expression of alpha 2 beta 1 integrin and its extracellular ligand collagen IV by using monoclonal antibodies on th e cryostat section of 124 invasive mammary carcinomas. Two Patterns of alpha 2 beta 1 immunoreactivity, i.e. pericellular and basolateral, w ere identified in breast carcinomas and correlated with their histolog ical type. In most invasive ductal carcinomas of no special type (NOS) , integrin staining tended to decrease in both pericellular and basola teral aspects. Loss of basolateral staining for alpha 2 beta 1 integri n corresponded closely to the loss of immunoreactivity for collagen IV Mucinous and medullary carcinomas showed strongly alpha 2 beta 1 peri cellular staining, but no basolateral reactivity or collagen IV expres sion. Only two of the infiltrating lobular carcinomas expressed strong pericellular reactivity. In 82 ductal carcinomas NOS, the abnormally low expression/absence of alpha 2 beta 1 integrin correlated with estr ogen and progesterone receptor negativity p<0.04 and p<0.002, respecti vely). No correlation between integrin expression, histological grade, nodal involvement and proliferative activity was found. The results o f the present study suggest that changes in alpha 2 beta 1 expression correlate with the histological type and hormonal receptor status in b reast carcinomas. The clinical implications of these findings remain t o be elucidated.