title: Gastrin mediates resistance to hypoxia-induced cell death in xenografts of the human colorectal cancer cell line LoVo.
abstract: OBJECTIVE
  Gastrins act as growth factors for the normal and neoplastic colorectal mucosa. The aim of this study was to determine the role of gastrins in the response of human colorectal cancer (CRC) cells to hypoxia in vitro and in vivo.
  
  
  METHODS
  Expression of the gastrin gene in the human CRC cell line LoVo was examined under normoxia and hypoxia by quantitative PCR and by radioimmunoassay. Gastrin expression was knocked down with shRNA, and the effect on cell proliferation was measured by cell counting, on cell apoptosis by annexin V staining, and on cell migration by Boyden chamber assay. The effect of gastrin knockdown on tumourigenesis in mouse xenografts was analysed by measurement of tumour volumes and weights, and by immunohistochemistry.
  
  
  RESULTS
  Gastrin gene expression in LoVo cells was stimulated by hypoxia via binding of hypoxia-inducible factor-1α to the gastrin promoter. The viability of gastrin knockdown cells exposed to hypoxia (1% O2) in vitro was diminished because of loss of resistance against hypoxia-induced apoptosis, and the effect was partly reversed by treatment with non-amidated, but not amidated, gastrin. Conditioned medium from control LoVo cells under hypoxia simulated proliferation but not migration, and the effect was blocked by an inhibitor of non-amidated gastrins, but not by an inhibitor of amidated gastrins. In xenografts in mice exposed to hypoxia (10% O2) for 21days, tumour necrosis was significantly increased by knocking down gastrin expression.
  
  
  CONCLUSIONS
  These results provide evidence that non-amidated gastrins are involved in the adaptation of CRCs to hypoxic microenvironments through increasing resistance to apoptosis.
authors.affiliation: The University of Melbourne Department of Surgery, Austin Health, Heidelberg, Victoria, Australia.
authors.forename: David A
authors.initials: DA
authors.lastname: Westwood
authors.affiliation: The University of Melbourne Department of Surgery, Austin Health, Heidelberg, Victoria, Australia.
authors.forename: Oneel
authors.initials: O
authors.lastname: Patel
authors.affiliation: The University of Melbourne Department of Surgery, Austin Health, Heidelberg, Victoria, Australia. Electronic address: grahamsb@unimelb.edu.au.
authors.forename: Graham S
authors.initials: GS
authors.lastname: Baldwin
keywords: Cancer; Colorectal; Gastrin; Hypoxia