Introduction Epidemiological evidence supports the potential role of dietary haem iron in gastrointestinal carcinogenesis.1 2 Oesophageal cancer cells acquire inorganic and organic iron by progressive up-regulation of iron and haem transport proteins.3 These alterations result in increased cellular iron loading which is likely to drive cellular proliferation.3 The effect of perturbing haem import proteins, hemopexin receptor (LRP1) and haem carrier protein (HCP1), on cancer cell iron transport, phenotype and tumour burden is unknown. The aim was to determine the in vitro and in vivo effects of depriving oesophageal cancer cells of haem iron.
Methods Stable knock-downs of LRP1 and HCP1 were created by infection with specific shRNA lenti-viral vectors. Successful knock-down was confirmed by Western blotting. The effect on cellular iron transport and cell phenotype was assessed by qRT-PCR and phenotypic experiments for viability, proliferation, migration and anchorage independent growth. Stable knock-downs of LRP1 and HCP1 were then xenografted into NOD-SCID mice as an in vivo model of oesophageal adenocarcinoma.
Results Perturbation of LRP1 and HCP1 caused a compensatory up-regulation of inorganic iron import proteins and a decrease in iron storage capacity. Neoplastic activity was significantly impaired compared to control (proliferation, viability, colony forming and migration – all p=<0.01). Loss of active haem iron import significantly reduced xenograft tumour burden in murine models with a 70% (p=0.014) and 58% (p=0.05) reduction in average xenograft weight compared to control.
Conclusion Haem import significantly contributes to iron loading in oesophageal cancer cells and creates a more aggressive phenotype. Functional inhibition of haem importing proteins LRP1 and HCP1 curbs neoplastic activity and significantly reduces in vivo tumour burden in murine models. Haem iron transport proteins are potential therapeutic targets in the treatment of oesophageal adenocarcinoma.
Competing interests None declared.
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2. Cross AJ, Leitzmann MF, Gail MH, et al. A prospective study of red and processed meat intake in relation to cancer risk. PLoS Med 2007;4:e325.
3. Boult J, Roberts K, Brookes MJ, et al. Overexpression of cellular iron import proteins is associated with malignant progression of esophageal adenocarcinoma. Clin Cancer Res 2008;14:379–87.