Reversion of the Malignant Phenotype of Human Breast Cells in Three-Dimensional Culture and In Vivo by Integrin Blocking Antibodies

Abstract

In a recently developed human breast cancer model, treatment of tumor cells in a 3-dimensional culture with inhibitory β1-integrin antibody or its Fab fragments led to a striking morphological and functional reversion to a normal phenotype. A stimulatory β1-integrin antibody proved to be ineffective. The newly formed reverted acini re-assembled a basement membrane and re-established E-cadherin–catenin complexes, and re-organized their cytoskeletons. At the same time they downregulated cyclin D1, upregulated p21cip,waf-1, and stopped growing. Tumor cells treated with the same antibody and injected into nude mice had significantly reduced number and size of tumors in nude mice. The tissue distribution of other integrins was also normalized, suggesting the existence of intimate interactions between the different integrin pathways as well as adherens junctions. On the other hand, nonmalignant cells when treated with either α6 or β4 function altering antibodies continued to grow, and had disorganized colony morphologies resembling the untreated tumor colonies. This shows a significant role of the α6/β4 heterodimer in directing polarity and tissue structure. The observed phenotypes were reversible when the cells were disassociated and the antibodies removed. Our results illustrate that the extracellular matrix and its receptors dictate the phenotype of mammary epithelial cells, and thus in this model system the tissue phenotype is dominant over the cellular genotype.

The extracellular matrix in breast cancer predicts prognosis through composition, splicing, and crosslinking

“…Furthermore, tumor reversion, or induction of a quiescent phenotype in malignant cells requires laminin and induction of normal cell-ECM signaling [16,28]. Laminin-111/Ln-1 has three head domains which can crosslink into a soft cohesive 3D network, whereas other laminin isoforms with truncated head domains, such as laminin-332/Ln-5, laminin-511/Ln-10 or laminin-521/Ln-11, cannot form a network [22,29], and do not support normal epithelial cell function in vitro, despite the fact that all these isoforms present similar tail domains to cells [16].…”

Expression level of integrin α5 on tumour cells affects the rate of metastasis to the kidney

“…In melanoma, alterations of a2b1, a3b1, and a6b1 integrins appear to be associated with malignancy (Chen et al, 1991;Natali et al, 1991Natali et al, ,1993Moretti et al, 1993). In breast cancer, a2b1, a5b1, or a6b4 integrins seem to be crucial for malignant transformation (Pignatelli et al, 1991;Natali et al, 1992;Zutter et al, 1993;Weaver et al, 1997). In pancreatic carcinoma cell lines, expression of a2, a3, a6, b1, b4, and b5 integrins was detected in adenocarcinomas and ampullary tumours, in the normal pancreas, reduced levels of expression occur, or in the case of some integrins there is no expression (Hall et al, 1991).…”

Induction of a novel isoform of the lncRNA HOTAIR in Claudin‐low breast cancer cells attached to extracellular matrix

“…These findings likely reflect the complexity in composition of ECM and the signaling pathways in response to ECM. Interference of other integrin receptors and kinases individually and in combination, such as integrin α6 (major receptors for laminin), is still needed to determine the role of each individual ECM and its responsive cellular signaling molecules in the activation of HOTAIR expression (Kenny et al ., 2007b; Lee et al ., 2007; Lu et al ., 2012; Weaver et al ., 1997; Ziober et al ., 1999). More importantly, our results indicate that HOTAIR expression is required for invasive growth of Claudin‐low breast cancer cells, particularly cell viability (Fig.…”