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Integrin α9β1 promotes malignant tumor growth and metastasis by potentiating epithelial-mesenchymal transition.

Gupta SK, Oommen S, Aubry MC, Williams BP, Vlahakis NE - Oncogene (2012)

Bottom Line: In addition, we found that α9β1 forms a tri-partite protein complex with β-catenin and E-cadherin, which dissociates following integrin activation and subsequent src and β-catenin phosphorylation.These in vitro results are biologically significant as α9β1-expressing cancer cells induce greater tumor growth and metastases in mice as compared to the cells without α9β1 expression or when integrin expression is suppressed.Furthermore, integrin α9β1 is expressed in primary human small cell lung cancer and patients having a high expression of α9β1 demonstrated significantly worse long-term survival compared with patients with low α9β1 expression.

View Article: PubMed Central - PubMed

Affiliation: Thoracic Disease Research Unit, Division of Pulmonary & Critical Care Medicine, Mayo Clinic, Rochester 55905, MN, USA.

ABSTRACT
The integrin α9β1 binds a number of extracellular matrix components to mediate cell adhesion, migration and tissue invasion. Although expressed in a variety of normal human cells including endothelium, it is also expressed in cancer cells. We have previously shown that α9β1 binds VEGF-A to facilitate angiogenesis, an important component of the tumor microenvironment. As α9β1 induces accelerated cancer cell migration, we wished to determine what role it played in cancer growth and metastasis. In this study, we show that α9β1 expression induces molecular changes consistent with epithelial-mesenchymal transition. In addition, we found that α9β1 forms a tri-partite protein complex with β-catenin and E-cadherin, which dissociates following integrin activation and subsequent src and β-catenin phosphorylation. These findings were consistent in cells in which: α9β1 was exogenously over-expressed, or when its expression was suppressed in cancer cells endogenously expressing α9β1. These in vitro results are biologically significant as α9β1-expressing cancer cells induce greater tumor growth and metastases in mice as compared to the cells without α9β1 expression or when integrin expression is suppressed. Furthermore, integrin α9β1 is expressed in primary human small cell lung cancer and patients having a high expression of α9β1 demonstrated significantly worse long-term survival compared with patients with low α9β1 expression. These findings highlight a novel mechanism of integrin α9β1 function in human cancer.

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α9β1 induces cellular changes of EMT and enhanced cancer cell migration and invasionA, Flow cytometry analysis showing the extent of α9β1 surface expression (shaded histograms) on cells as indicated; and isotype antibody control (clear histogram). B, Immunoblots for α9, β1, E-cadherin or N-cadherin in lysates from mouse (LLC-1) or human NSCLC and SCLC cell lines. C, Cell adhesion on plastic (no matrix) or TnfnRAA with (black) or without (grey) α9β1 inhibitor, VLO5. D, Cell migration in the presence (black) or absence (grey) of TnfnRAA and/or VLO5. E, Cell invasion using cells stimulated by TnfnRAA and treated with (black) or without (grey) VLO5. F, Immunoblots to detect the EMT markers E-cadherin and vimentin in lysates from cells grown on plastic (no matrix) or TnfnRAA or with TGF-β.
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Figure 4: α9β1 induces cellular changes of EMT and enhanced cancer cell migration and invasionA, Flow cytometry analysis showing the extent of α9β1 surface expression (shaded histograms) on cells as indicated; and isotype antibody control (clear histogram). B, Immunoblots for α9, β1, E-cadherin or N-cadherin in lysates from mouse (LLC-1) or human NSCLC and SCLC cell lines. C, Cell adhesion on plastic (no matrix) or TnfnRAA with (black) or without (grey) α9β1 inhibitor, VLO5. D, Cell migration in the presence (black) or absence (grey) of TnfnRAA and/or VLO5. E, Cell invasion using cells stimulated by TnfnRAA and treated with (black) or without (grey) VLO5. F, Immunoblots to detect the EMT markers E-cadherin and vimentin in lysates from cells grown on plastic (no matrix) or TnfnRAA or with TGF-β.

Mentions: Having shown that EMT and metastatic cell behavior can be induced by the exogenous over-expression of α9β1, we next determined whether endogenously expressed integrin in lung cancer cells had a comparable action. Using flow cytometry (Fig 4A) and immunoblotting (Fig 4B) we found that α9β1 expression was variable but appeared more robust in human SCLC compared to NSCLC. In addition, LLC1, a mouse model cell line for lung carcinoma, also expressed integrin α9β1. Compared to normal bronchial epithelium (NHBE), these cancer cell lines showed evidence of EMT, as measured by E and N-cadherin expression. However, those cells expressing α9β1 demonstrated relatively less expression of E-cadherin and higher expression of N-cadherin and the extent of colony formation by these cancer cells on soft agar was dependent on the extent of α9β1 expression (Suppl. Fig S6-A,B). Integrin α9β1 appears to induce a functionally relevant EMT phenotype in these lung cancer cells as demonstrated by increased α9β1-dependent adhesion (Fig 4C), migration (Fig 4D) and Matrigel invasion (Fig 4E). Although the overall extent of the response varied, they were mostly proportional to the magnitude of α9β1 expression.


Integrin α9β1 promotes malignant tumor growth and metastasis by potentiating epithelial-mesenchymal transition.

Gupta SK, Oommen S, Aubry MC, Williams BP, Vlahakis NE - Oncogene (2012)

α9β1 induces cellular changes of EMT and enhanced cancer cell migration and invasionA, Flow cytometry analysis showing the extent of α9β1 surface expression (shaded histograms) on cells as indicated; and isotype antibody control (clear histogram). B, Immunoblots for α9, β1, E-cadherin or N-cadherin in lysates from mouse (LLC-1) or human NSCLC and SCLC cell lines. C, Cell adhesion on plastic (no matrix) or TnfnRAA with (black) or without (grey) α9β1 inhibitor, VLO5. D, Cell migration in the presence (black) or absence (grey) of TnfnRAA and/or VLO5. E, Cell invasion using cells stimulated by TnfnRAA and treated with (black) or without (grey) VLO5. F, Immunoblots to detect the EMT markers E-cadherin and vimentin in lysates from cells grown on plastic (no matrix) or TnfnRAA or with TGF-β.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3368989&req=5

Figure 4: α9β1 induces cellular changes of EMT and enhanced cancer cell migration and invasionA, Flow cytometry analysis showing the extent of α9β1 surface expression (shaded histograms) on cells as indicated; and isotype antibody control (clear histogram). B, Immunoblots for α9, β1, E-cadherin or N-cadherin in lysates from mouse (LLC-1) or human NSCLC and SCLC cell lines. C, Cell adhesion on plastic (no matrix) or TnfnRAA with (black) or without (grey) α9β1 inhibitor, VLO5. D, Cell migration in the presence (black) or absence (grey) of TnfnRAA and/or VLO5. E, Cell invasion using cells stimulated by TnfnRAA and treated with (black) or without (grey) VLO5. F, Immunoblots to detect the EMT markers E-cadherin and vimentin in lysates from cells grown on plastic (no matrix) or TnfnRAA or with TGF-β.
Mentions: Having shown that EMT and metastatic cell behavior can be induced by the exogenous over-expression of α9β1, we next determined whether endogenously expressed integrin in lung cancer cells had a comparable action. Using flow cytometry (Fig 4A) and immunoblotting (Fig 4B) we found that α9β1 expression was variable but appeared more robust in human SCLC compared to NSCLC. In addition, LLC1, a mouse model cell line for lung carcinoma, also expressed integrin α9β1. Compared to normal bronchial epithelium (NHBE), these cancer cell lines showed evidence of EMT, as measured by E and N-cadherin expression. However, those cells expressing α9β1 demonstrated relatively less expression of E-cadherin and higher expression of N-cadherin and the extent of colony formation by these cancer cells on soft agar was dependent on the extent of α9β1 expression (Suppl. Fig S6-A,B). Integrin α9β1 appears to induce a functionally relevant EMT phenotype in these lung cancer cells as demonstrated by increased α9β1-dependent adhesion (Fig 4C), migration (Fig 4D) and Matrigel invasion (Fig 4E). Although the overall extent of the response varied, they were mostly proportional to the magnitude of α9β1 expression.

Bottom Line: In addition, we found that α9β1 forms a tri-partite protein complex with β-catenin and E-cadherin, which dissociates following integrin activation and subsequent src and β-catenin phosphorylation.These in vitro results are biologically significant as α9β1-expressing cancer cells induce greater tumor growth and metastases in mice as compared to the cells without α9β1 expression or when integrin expression is suppressed.Furthermore, integrin α9β1 is expressed in primary human small cell lung cancer and patients having a high expression of α9β1 demonstrated significantly worse long-term survival compared with patients with low α9β1 expression.

View Article: PubMed Central - PubMed

Affiliation: Thoracic Disease Research Unit, Division of Pulmonary & Critical Care Medicine, Mayo Clinic, Rochester 55905, MN, USA.

ABSTRACT
The integrin α9β1 binds a number of extracellular matrix components to mediate cell adhesion, migration and tissue invasion. Although expressed in a variety of normal human cells including endothelium, it is also expressed in cancer cells. We have previously shown that α9β1 binds VEGF-A to facilitate angiogenesis, an important component of the tumor microenvironment. As α9β1 induces accelerated cancer cell migration, we wished to determine what role it played in cancer growth and metastasis. In this study, we show that α9β1 expression induces molecular changes consistent with epithelial-mesenchymal transition. In addition, we found that α9β1 forms a tri-partite protein complex with β-catenin and E-cadherin, which dissociates following integrin activation and subsequent src and β-catenin phosphorylation. These findings were consistent in cells in which: α9β1 was exogenously over-expressed, or when its expression was suppressed in cancer cells endogenously expressing α9β1. These in vitro results are biologically significant as α9β1-expressing cancer cells induce greater tumor growth and metastases in mice as compared to the cells without α9β1 expression or when integrin expression is suppressed. Furthermore, integrin α9β1 is expressed in primary human small cell lung cancer and patients having a high expression of α9β1 demonstrated significantly worse long-term survival compared with patients with low α9β1 expression. These findings highlight a novel mechanism of integrin α9β1 function in human cancer.

Show MeSH
Related in: MedlinePlus