Extracellular matrix in mammary gland development and breast cancer progression

Hu G., Li L., Xu W.
Frontiers in Laboratory Medicine, 2017

Extracellular matrix is one of the essential components of the breast tumor microenvironment, in which the development and progression require extensive reorganization of ECM. In this review, the authors summarized recent findings on functions of ECM microenvironment in mammary gland development, tumor growth, invasion, migration and metastasis, focusing on the functions of cancer cell-derived ECM in tumor progression.

 

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

Chia J., Kusuma N., Anderson R., Parker B., Bidwell b., Zamurs L., Nice E., Pouliot N.
The American Journal of Pathology, 2007

Here, the authors investigate the expression and function of alpha5 chain-containing laminins, laminin-521 and laminin-511, during metastatic progression. Expression of laminin-511/laminin-521 subunits was examined in genetically related breast tumor lines and corresponding primary tumors and metastases in a syngeneic mouse model. The results indicate that laminin-511 rather than laminin-111, -332, or -521 correlates with metastatic potential in mouse mammary tumors. Current evidence argues against a direct role for laminin-111 and laminin-332 in the late stage progression of breast tumors because both isoforms are down-regulated in most advanced breast tumors, suggesting a tumor suppressing role and it is unlikely that these isoforms are used directly by breast tumor cells to promote invasion and metastasis. Laminin-511 was a potent adhesive substrate for both murine and human breast carcinoma cells and promoted strong haptotactic responses in metastatic lines. Haptotaxis was mediated by alpha3 integrin in both MCF-7 and MDA-MB-231 cells and was strongly inhibited by blocking antibodies against this integrin subunit. However, whereas nonmetastatic MCF-7 cells migrated toward laminin-511 (primarily via a3β1 integrin), results suggest that this response is mediated by an as yet unidentified a3β integrin heterodimer in MDA-MB-231 cells. These results are consistent with earlier reports implicating a3 integrins in breast cancer progression and support the role of laminin-511 as a functional substrate regulating breast cancer metastasis.

 

Laminin α5 is necessary for submandibular gland epithelial morphogenesis and influences FGFR expression through β1 integrin signaling

Rebustini I.T., Patel V.N., Stewart J.S, Layvey A. Georges-Labouesse E., Hoffman M.P
Dev Biol. 2007

Here, the authors investigate the function of laminin α5 in mouse submandibular glands (SMGs). They show that although laminin α5 is not required for gland initiation, it plays an important role in initial cleft formation and epithelial morphogenesis; is necessary for sublingual gland formation; and later in development is required for epithelial cell organization and lumen formation. The data suggests that laminin α5 controls SMG epithelial morphogenesis through β1 integrin signaling by regulating FGFR expression, which also reciprocally regulates the expression of Lama5 and that this regulation is independent of Lama1. Lama5-/- SMGs have a striking phenotype: epithelial clefting is delayed, although proliferation occurs; there is decreased FGFR1b and FGFR2b, but no difference in Lama1 expression; later in development, epithelial cell organization and lumen formation are disrupted. In wild-type SMGs α5 and α1 are present in epithelial clefts but as branching begins α5 expression increases while α1 decreases. Lama5 siRNA decreased branching, p42 MAPK phosphorylation, and FGFR expression, and branching was rescued by FGF10. FGFR siRNA decreased Lama5 suggesting FGFR signaling provides positive feedback for Lama5 expression. Anti-β1 integrin antibodies decreased FGFR and Lama5 expression, suggesting that β1 integrin signaling provides positive feedback for Lama5 and FGFR expression. Interestingly, the Itga3-/-:Itga6-/- SMGs have a similar phenotype to Lama5-/-. Our findings suggest that laminin α5 controls mouse submandibular glands epithelial morphogenesis through β1 integrin signaling by regulating FGFR expression, which also reciprocally regulates the expression of Lama5. These data link changes in basement membrane composition during branching morphogenesis with FGFR expression and signaling.

 

A laminin 511 matrix is regulated by TAZ and functions as the ligand for the a6Bb1 integrin to sustain breast cancer stem cells

Chang C., Lal Goel H., Gao H., Pursell B., Shultz L.D., Greiner D.L., Ingerpuu S., Patarroyo M., Cao S., Lim E., Mao J., Kulju McKee K., Yurchenco P.D., Mercurio A.M.
Research communication, 2015

One of the first papers that highlighted the importance of ECM proteins in 2D breast cancer stem cell culture. Shows that laminin-511 is a critical niche component for breast cancer stem cells. Breast cancer stem cells produce a laminin-511 matrix that functions as the ligand for the a6Bb1 integrin to promote self-renewal and tumor initiation. The authors observed that TAZ regulates the transcription of the a5 subunit of LN511 and the formation of a LN511 matrix. These data establish a positive feedback loop involving TAZ and LN-511 that contributes to stemness in breast cancer. They see down-regulation of the laminin B2 chain.

 

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

Kusuma N., Denoyer D., Eble J.A., Redvers R.P., Parker B.S., Pelzer R. Anderson R.L., Pouliot N.
International Journal of Cancer, 2011

Laminin-511 is a potent adhesive and migratory substrate for metastatic breast tumor cells in vitro and its expression correlates with tumor grade and metastatic potential in vivo. Here the authors 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 dis-integrin 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.

 

Laminin and b1 Integrins Are Crucial for Normal Mammary Gland Development in the Mouse

Klinowska T.C.M., Soriano J.V., Edwards G.M., Oliver J.M., Valentijn A.J., Montesano R., Streuli C.H.
Developmental Biology, 1999

Here, the authors examine the role of integrin-extracellular matrix interactions in the morphogenesis of ductal structures in vivo (mouse). End buds are surrounded by a basement membrane, which is shown to contain laminin-111 and collagen IV. Blocking B1 integrins dramatically reduced both the number of end buds per gland and the extent of the mammary ductal network, compared with controls. These effects were specific to the end buds since the rest of the gland architecture remained intact. Similar results were obtained with anti-laminin antibodies. In contrast, no effect on morphogenesis in vivo was seen with anti-a6 integrin antibody, suggesting that a6 is not the important partner for b1 in this system. They also show that integrins and hepatocyte growth factor (HGF) cooperate to regulate ductal morphogenesis. We propose that both laminin and b1 integrins are required to permit cellular traction through the stromal matrix and are therefore essential for maintaining end bud structure and function in normal pubertal mammary gland development.

 

Modifications in the basement membrane supramolecular structure of type IV collagen and laminin 5 organization facilitates skin derivative formation

Alfayez M.
Biomedical Research, 2010

It has been suggested that laminin-332 is involved in initiation of mammary gland development whilst laminin-511 is needed for maintaining the mammary bud down-growth into the dermis. In this study, the authors examine the proposed role(s) of the basement membrane proteins and their receptors during skin development using dissected mammary gland as a model. The pattern of expression of these molecules during skin formation was examined, utilizing collagen IV, laminin 5 and β4 or α6 integrin antibodies. The results suggest that these supramolecular structures play important roles in skin derivative development, more specifically mammary gland formation, and ease their resistance to skin derivatives down growth (invasion) into the underlying tissue.

 

Regulation of mammary gland branching morphogenesis by the extracellular matrix and its remodeling enzymes

Fata J.E., Werb Z. Bissell M.J
Breast Cancer Res 2004

A considerable body of research indicates that mammary gland branching morphogenesis is dependent, in part, on the extracellular matrix, affecting cell survival, polarity, proliferation, differentiation, adhesion, and migration. However, the precise mechanisms of ECM-directed mammary morphogenesis are not well understood and is discussed in this review. Mammary morphogenesis involves epithelial invasion of adipose tissue, a process akin to invasion by breast cancer cells, although the former is a highly regulated developmental process. How these morphogenic pathways are integrated in the normal gland and how they become dysregulated and subverted in the progression of breast cancer also remain largely unanswered questions.

 

Cell–Matrix Interactions in Mammary Gland Development and Breast Cancer

Muschler J., Streuli C.H.
Cold Spring Harb Perspect Biol., 2010

Here, the authors argue that the interactions between mammary epithelial cells and their extracellular matrix (ECM) are crucial in the development and function of the tissue. Current strategies for treating breast cancer take advantage of our knowledge of the endocrine regulation and stromal–epithelial interactions. In addition, focusing on the microenvironmental influences that arise from cell–matrix interactions may open new opportunities for therapeutic intervention, suggesting a treatment where endocrine, growth factor, and cell-matrix interactions are targeted.

 

Laminin-rich extracellular matrix association with mammary epithelial cells suppresses Brca1 expression

O'Connell F.C., Martin F.
Cell Death and Differentiation, 2000

In a primary cell culture model, association of a laminin-rich extracellular matrix (laminin-111) with mammary epithelial cells was required for cell survival and cell differentiation and suppressed Brca1 expression in these cells. ECM-association may significantly contribute to the final restriction in Brca1 expression in the lactating gland in vivo. Interestingly, the results suggest that mammary epithelial cells undergo apoptosis both when expressing and when not expressing Brca1, depending on whether the dying cell populations had been terminally differentiated or not.