Targeting transforming growth factor (TGF)-betaRI inhibits activation of beta1 integrin and blocks vascular invasion in hepatocellular carcinoma.
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 alpha5beta1, that is equally expressed in invasive and noninvasive cells. However, in the former, the intracytoplasmic tail of beta1 integrin is constitutively phosphorylated at threonine 788-789 and the extracellular part is conformationally activated. In noninvasive cells, beta1 integrin is not activated. Transforming growth factor (TGF)-beta1 specifically phosphorylates beta1 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-betaRI inhibitor inhibits phosphorylation of the beta1 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-beta1 integrin was detected as well as TGF-beta1, p-Smad-2, and E-cadherin.


CONCLUSIONS
TGF-beta1 promotes vascular invasion by activating beta1 integrin. This suggests a rationale for targeting TGF-betaRI in future clinical trials.
Fransvea
Emilia
E
Department of Internal Medicine, Section of Internal Medicine; University of Bari Medical School, Bari, Italy. g.giannelli@intmed.uniba.it
Mazzocca
Antonio
A
Antonaci
Salvatore
S
Giannelli
Gianluigi
G
D000368:Aged; D015820:Cadherins / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000098:blood supply* / Q000473:pathology / Q000503:physiopathology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005260:Female; D006801:Humans; D039081:Integrin alpha5beta1 / Q000378:metabolism; D019012:Integrin beta1 / Q000378:metabolism*; D008113:Liver Neoplasms / Q000098:blood supply* / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009389:Neovascularization, Pathologic / Q000503:physiopathology*; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism*; D011720:Pyrazoles / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000187:drug effects / Q000378:metabolism*; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism
D015820:Cadherins; D004791:Enzyme Inhibitors; D016326:Extracellular Matrix Proteins; D039081:Integrin alpha5beta1; D019012:Integrin beta1; C530108:LY2109761; D011720:Pyrazoles; D011758:Pyrroles; D018125:Receptors, Transforming Growth Factor beta; D051899:Smad2 Protein; D051900:Smad3 Protein; D053773:Transforming Growth Factor beta1; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I