Integrin‐dependent response to laminin‐511 regulates breast tumor cell invasion and metastasis

Abstract

The basement membrane protein, laminin (LM)-511, is a potent adhesive and migratory substrate for metastatic breast tumor cells in vitro. Its expression correlates with tumor grade and metastatic potential in vivo. These observations suggest that responsiveness to autocrine or paracrine-derived LM-511 may be an important property regulating breast cancer metastasis in vivo. To address this, we compared the metastatic potential of 4T1 mammary carcinoma cells to that of 4T1 variants isolated by repeated chemotactic migration toward LM-511 in vitro (4T1LMF4) followed by serial injection into the mammary gland and recovery of spontaneous metastases from bone (4T1BM2). Variant subpopulations exhibited a distinct morphology on LM-511 and increased expression of b1 and b4 integrins compared to parental 4T1 cells. Importantly, mice inoculated with 4T1LMF4 and 4T1BM2 variants showed a 2.5-to 4-fold increase in the incidence of spontaneous metastasis to bone compared to 4T1 tumor-bearing mice. Functionally, 4T1BM2 variants were more adherent and more invasive toward LM-511 than parental 4T1 cells. Treatment of 4T1BM2 cells with lebein-1, a disintegrin with selectivity toward LM-type integrin receptors, potently inhibited their migration and invasion toward LM-511. Similarly, a3b1 integrin-dependent migration and invasion of human MDA-MB-231 breast carcinoma cells toward LM-511 were significantly inhibited by lebein-1. Taken together, these results provide strong evidence that LM-511 contributes to the metastasis of breast tumors and suggest that targeting integrin-LM-511 interactions with lebein-1 or other inhibitors of LM-511 receptors may have therapeutic potential for patients with advanced breast cancer.Metastasis from primary breast tumors is the leading cause of cancer related death in women. In these patients, metastases develop most commonly in bone, lung, liver and brain. In particular, bone metastasis that occurs in the majority of patients with advanced breast cancer inevitably leads to various debilitating skeletal complications. 1 Yet despite significant advances, the mechanisms involved in the development of bone or soft tissue metastases remain elusive. The current evidence indicates that organ-specific tropism is regulated in part by stromal factors (chemokines, growth factors and extracellular matrix proteins) produced at metastatic sites. 2,3 In turn, metastatic colonization depends on intrinsic properties of tumor cells and on the acquisition of specific attributes that allow them to respond appropriately to the signals emanating from the metastatic microenvironment. Thus, complex interactions between intrinsic and stromal-derived signals cooperate to facilitate homing, survival and growth of metastatic breast tumors in distant organs. [4][5][6] However, not all cells within a given tumor have the same ability to respond to external signals and to metastasize. The concepts of tumor heterogeneity and rare metastatic variants are now firmly established 7,8 and are best exemplified by the heterogeneity in ...

Laminin α5-derived peptides modulate the properties of metastatic breast tumour cells

“…Our study demonstrated that LM-511 is a potent adhesive substrate for breast tumour cells and promotes their migration and invasion [9]. The relevance of breast tumour cell interaction with LM-511 in metastasis was further supported by the isolation of aggressive bone metastatic tumour variants using a selection protocol based on their rapid migratory response towards LM-511 in vitro [16]. The enhanced metastatic capacity of these variants was associated with increased expression of b1 and b4 integrin/laminin receptors [16].…”

“…Our own investigation revealed a role for LM-511 but not LM-111 or -332 in the regulation of breast cancer metastasis [5,9,16]. Here, we sought to test LMa5 chain-derived peptides, previously shown to possess cell binding activity [19,20,41], for their ability to modulate LM-511-dependent breast tumour cell responses in vitro and metastasis in vivo.…”

“…The medium was then removed and fresh medium containing 50 lg/ml lamininderived synthetic peptides was added. After 24, 48, 72, and 96 h, tumour cells were fixed by addition of 50 ll/well of 50% trichloroacetic acid (TCA), and proliferation was quantified using Sulforhodamine B (SRB) staining as described previously [16].…”

“…LM consists of one a-, one b-, and one c-chain that assemble into a cross-like heterotrimeric structure. To date, 16 laminin isoforms have been identified in mammals [6], and their roles in modulating cell adhesion, proliferation, differentiation, and migration in normal and pathological states have been widely documented [7,8].…”

“…The relevance of breast tumour cell interaction with LM-511 in metastasis was further supported by the isolation of aggressive bone metastatic tumour variants using a selection protocol based on their rapid migratory response towards LM-511 in vitro [16]. The enhanced metastatic capacity of these variants was associated with increased expression of b1 and b4 integrin/laminin receptors [16]. Together, these observations suggest that interfering with LM-511-dependent interactions could be an effective strategy to block or delay the onset of breast cancer metastasis.…”