Targeting transforming growth factor (TGF)-βRI inhibits activation of β1 integrin and blocks vascular invasion in hepatocellular carcinoma

Authors

  • Emilia Fransvea,

    1. Department of Internal Medicine, Immunology and Infectious Diseases, Section of Internal Medicine; University of Bari Medical School, Bari, Italy
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    • These authors contributed equally to this work.

  • Antonio Mazzocca,

    1. Department of Internal Medicine, Immunology and Infectious Diseases, Section of Internal Medicine; University of Bari Medical School, Bari, Italy
    2. Department of Pathology, Vanderbilt University Medical Center, Nashville, TN
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    • These authors contributed equally to this work.

  • Salvatore Antonaci,

    1. Department of Internal Medicine, Immunology and Infectious Diseases, Section of Internal Medicine; University of Bari Medical School, Bari, Italy
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  • Gianluigi Giannelli

    Corresponding author
    1. Department of Internal Medicine, Immunology and Infectious Diseases, Section of Internal Medicine; University of Bari Medical School, Bari, Italy
    • Dipartimento di Clinica Medica, Immunologia e Malattie Infettive, Sezione di Medicina Interna, Policlinico, piazza G. Cesare 11, 70124 Bari, Italy
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    • fax: (39)-080-5478-126.


  • Potential conflict of interest: Nothing to report.

Abstract

Vascular invasion is one of the major negative prognostic factors in patients with hepatocellular carcinoma (HCC), leading to cancer recurrence. To invade, HCC cells must penetrate the vessel wall, consisting of endothelial cells and extracellular matrix components, including fibronectin and fibrinogen. Employing invasive and noninvasive HCC cells, we studied the mechanism underlying vascular invasion. We show that HCC cells invade blood vessels via α5β1, that is equally expressed in invasive and noninvasive cells. However, in the former, the intracytoplasmic tail of β1 integrin is constitutively phosphorylated at threonine 788-789 and the extracellular part is conformationally activated. In noninvasive cells, β1 integrin is not activated. Transforming growth factor (TGF)-β1 specifically phosphorylates β1 integrin (threonine 788-789) via Smad-2 and Smad-3, causing a conformational change of the extracellular component with an inside-out mechanism. This leads noninvasive HCC cells to behave like invasive cells. A selective TGF-βRI inhibitor inhibits phosphorylation of the β1 integrin intracytoplasmic tail, and blocks invasion of HCC cells, both constitutively invasive and with acquired invasive properties. In human HCC tissues with microvascular invasion, phospho-β1 integrin was detected as well as TGF-β1, p-Smad-2, and E-cadherin. Conclusion: TGF-β1 promotes vascular invasion by activating β1 integrin. This suggests a rationale for targeting TGF-βRI in future clinical trials. (HEPATOLOGY 2009.)

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