Evidence for a Role of Tumor-Derived Laminin-511 in the Metastatic Progression of Breast Cancer

Abstract

Most studies investigating laminins (LMs) in breast can1 Although there is considerable structural homology between LM isoforms 2 and overlap in receptors used, 3,4 they differ in their tissue distribution and functional properties and have different roles under normal and pathological conditions, including cancer.1,5-8 Alterations in the composition and level of expression of BM LMs and their receptors in breast cancer have been documented and shown to contribute to disease progression.9,10 In particular, the excessive proteolytic activity associated with cancer progression typically results in decreased LM deposition and dissolution of the BM, a hallmark of invasive breast tumors. [11][12][13] It is clear, however, that despite decreased BM deposition, some LM remains expressed in invasive breast tumor cells and contributes functionally to their motile and invasive phenotype.11,14 -16 Consistent with this, increased expression of several LM receptors has been reported in breast tumor cells and shown to be associated with metastatic progression and poor prognosis in breast cancer patients. 9,[17][18][19][20][21][22][23] Together, these studies suggest that production of LM by breast cancer cells most likely contributes to their metastatic dissemination through autocrine stimulation.Although the association between LMs and breast cancer progression is well supported, the critical LM isoform involved in the metastatic progression of breast tumors remains unclear. Most studies investigating the expression and function of LMs and their receptors in breast cancer have been interpreted as evidence for the role of LM-111 (␣1␤1␥1 trimer, previously known as laminin-1) or LM-332 (␣3␤3␥2 trimer, previously known as laminin-5) but did not take into account the lack of specificity of some of the LM antibodies 14,22,24,25 or the overlap in receptors used to bind these isoforms and the more recently identified LM-511/521 (␣5␤1␥1 and ␣5␤2␥1 trimers, previously known as laminin-10 and -11, respecSupported by the US Army Department of Defense (concept award no. W81XWH-04-1-0707 to N.P.).

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

“…We reported previously that the expression of LM-511 (a5b1c1) but not LM-111 or LM-332 correlates with tumour progression in human breast cancer and with metastatic potential in a mouse model of spontaneous mammary cancer metastasis [5,9]. Its elevated expression in both tumour cells and in the vasculature of advanced human breast tumours and metastases [9,10] is consistent with current literature supporting the pro-metastatic function of LM-511.…”

“…Its elevated expression in both tumour cells and in the vasculature of advanced human breast tumours and metastases [9,10] is consistent with current literature supporting the pro-metastatic function of LM-511. In contrast, LM-111 and -332 act as tumour suppressors and are often down-regulated in the late stages of breast cancer progression [11][12][13][14][15].…”

“…In contrast, LM-111 and -332 act as tumour suppressors and are often down-regulated in the late stages of breast cancer progression [11][12][13][14][15]. 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].…”

“…For inhibition of 4T1.2 cell adhesion to coated A5G27 peptide (10 lg/well), 4T1.2 cells (4 9 10 4 /well) were pre-incubated on ice for 15 min with function-blocking antibodies (20 lg/ml) directed against the CD44 receptor or specific integrin subunits, or incubated at 37°C for 1 h with heparin (Sigma) or heparinase II (Sigma) or a-L-fucosidase (Sigma) or neuraminidase (Sigma) together with EDTA-free protease inhibitor cocktail (Roche) and added together with the cells to assay wells. Fluorescence was measured using a Bio-Rad Molecular Imager FX reader and specific adhesion calculated from a standard curve made up of 0, 25, 50, 75 and 100 ll of calcein-labelled cell lysate derived from the initial cell suspension as described previously [9]. Results represent the mean percentage adhesion relative to the adhesion obtained on LM-511 in the absence of peptide ± SD of three independent experiments.…”

Stromal Cell Expression of Caveolin-1 Predicts Outcome in Breast Cancer

“…31 All tissues were fixed in 10% buffered formalin and paraffin-embedded. Mouse monoclonal and rabbit polyclonal anti-caveolin-1 antibodies (BD Transduction Laboratories, Lexington, KY), were used at 2.5 and 0.5 g/ml respectively.…”