Fibulin-2 is required for basement membrane integrity of mammary epithelium

Abstract

Fibulin-2 (FBLN2) is a secreted extracellular matrix glycoprotein which has been associated with tissue development and remodelling. In the mouse mammary gland, FBLN2 can be detected during ductal morphogenesis in cap cells and myoepithelial cells at puberty and early pregnancy, respectively. In an attempt to assign its function, we knocked down Fbln2 in the mouse mammary epithelial cell line EpH4. FBLN2 reduction led to an increase in the size of spheroidal structures when compared to scrambled control shRNA-transduced cells plated on Matrigel matrix. This phenotype was associated with a disruption of the collagen IV sheath around the epithelial spheroids and downregulation of integrin β1, suggesting a role for FBLN2 in stabilizing the basement membrane (BM). In contrast to mice, in normal adult human breast tissue, FBLN2 was detected in ductal stroma, and in the interlobular stroma, but was not detectable within the lobular regions. In tissue sections of 65 breast cancers FBLN2 staining was lost around malignant cells with retained staining in the neighbouring histologically normal tissue margins. These results are consistent with a role of FBLN2 in mammary epithelial BM stability, and that its down-regulation in breast cancer is associated with loss of the BM and early invasion.

Gas6 expression is reduced in advanced breast cancers

“…As with Gas6 scoring (Fig. 1a), Axl expression was scored based on intensity and number of cells stained positive as previously described 26 . Immunohistochemical analysis of normal breast showed complete absence of Axl staining, consistent with previous reports 25 , whereas nearly all ductal epithelium expressed moderate-high levels of Gas6.…”

“…For IHC antibody scoring, tissues were examined using ×20 and ×40 objectives. An arbitrary number was given on a scale of 0-3 by visual examination, based on the intensity and the number of stained cells, taking any field to field variation into account, where 0 was assigned for negative staining, 1 for low, 2 for moderate, and 3 for strong staining 26 . A separate score was assigned for either epithelial or stromal staining, and all samples were scored blindly by two independent individuals.…”

Correlation of Fibulin‑2 expression with proliferation, migration and invasion of breast cancer cells

“…A recent study found that there is no expression of Fibulin-2 in breast cancer patients, whereas normal in paracancerous tissues of breast cancer, which confirmed that Fibulin-2 can stabilize the basement membrane, and its downregulation is related to the loss of basement membrane and early invasion (17). Tan et al (18) showed that Fibulin-2 was expressed in breast ducts and perivascular tissues in normal breast tissues.…”

An Investigation of Fibulin-2 in Hypertrophic Cardiomyopathy

“…In this study, FBLN2 expression was evidently elevated in the myocardium and was clearly localized at the sub-endocardial fibrotic tissue excised from patients with obstructive HCM. FBLN2 has recently been shown to interact with COL IV to stabilize the basement membrane [ 26 ]. At the sub-endocardial region, FBLN2 co-localized with Col IV and TGFβ1.…”

“…Relative quantification of bands was performed using ImageJ software. Both FBLN2 bands (at 120 and 60 KDa) were considered in the quantification ( Figure 3 C,D and Supplementary Material Figures S3 and S4 ) [ 26 , 33 ].…”