title: Suppression of Hedgehog signalling promotes pro-tumourigenic integrin expression and function.
abstract: Aberrant Hedgehog (Hh) signalling has been reported in a number of malignancies, particularly basal cell carcinoma (BCC) of the skin. Clinical trials of Hh inhibitors are underway in many cancers, and these have produced significant clinical benefit in BCC patients, although regrowth of new, or clinically aggressive, variants, as well as development of secondary malignancies, has been reported. αvβ6 integrin is expressed in many cancers, where it has been shown to correlate with an aggressive tumour phenotype and poor prognosis. We have previously reported αvβ6 up-regulation in aggressive, morphoeic BCC variants, where it modulates the stromal response and induces invasion. To examine a possible link between Hh and αvβ6 function, we generated BCC models, overexpressing Gli1 in immortalized keratinocytes (NTert1, HaCaT). Unexpectedly, we found that suppressing Gli1 significantly increased αvβ6 expression. This promoted tumour cell motility and also stromal myofibroblast differentiation through integrin-dependent TGF-β1 activation. Gli1 inhibited αvβ6 expression by suppressing TGF-β1-induced Smad2/3 activation, blocking a positive feedback loop maintaining high αvβ6 levels. A similar mechanism was observed in AsPC1 pancreatic cancer cells expressing endogenous Gli1, suggesting a common mechanism across tumour types. In vitro findings were supported using human clinical samples, where we showed an inverse correlation between αvβ6 and Gli1 expression in different BCC subtypes and pancreatic cancers. In summary, we show that expression of Gli1 and αvβ6 inversely correlates in tumours in vivo, and Hh targeting up-regulates TGF-β1/Smad2/3-dependent αvβ6 expression, promoting pro-tumourigenic cell functions in vitro. These results have potential clinical significance, given the reported recurrence of BCC variants and secondary malignancies in patients treated by Hh targeting.
authors.affiliation: Cancer Sciences Unit, University of Southampton Faculty of Medicine, Southampton General Hospital, Southampton, SO16 6YD, UK.
authors.forename: Karwan A
authors.initials: KA
authors.lastname: Moutasim
authors.forename: Toby
authors.initials: T
authors.lastname: Mellows
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Mellone
authors.forename: Marie-Antoinette
authors.initials: MA
authors.lastname: Lopez
authors.forename: Joanne
authors.initials: J
authors.lastname: Tod
authors.forename: Philip C
authors.initials: PC
authors.lastname: Kiely
authors.forename: Karen
authors.initials: K
authors.lastname: Sapienza
authors.forename: Azzura
authors.initials: A
authors.lastname: Greco
authors.forename: Graham W
authors.initials: GW
authors.lastname: Neill
authors.forename: Shelia
authors.initials: S
authors.lastname: Violette
authors.forename: Paul H
authors.initials: PH
authors.lastname: Weinreb
authors.forename: John F
authors.initials: JF
authors.lastname: Marshall
authors.forename: Christian H
authors.initials: CH
authors.lastname: Ottensmeier
authors.forename: A Emre
authors.initials: AE
authors.lastname: Sayan
authors.forename: Veronika
authors.initials: V
authors.lastname: Jenei
authors.forename: Gareth J
authors.initials: GJ
authors.lastname: Thomas
mesh_terms: D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism*; D002280:Basal Cell Carcinoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002460:Cell Line; D002465:Cell Movement; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018920:Coculture Techniques; D015536:Down-Regulation; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D053823:Hedgehog Proteins / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000235:genetics / Q000378:metabolism*; D015603:Keratinocytes / Q000378:metabolism / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D034622:RNA Interference; D015398:Signal Transduction; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D000071676:Zinc Finger Protein GLI1
chemical_list: D000951:Antigens, Neoplasm; C400551:GLI1 protein, human; D053823:Hedgehog Proteins; D016023:Integrins; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; C508960:TGFB1 protein, human; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1; D000071676:Zinc Finger Protein GLI1; C073878:integrin alphavbeta6
keywords: Hedgehog; cancer; integrin; invasion; stroma