BMC Cancer (Oct 2012)

Activation of AKT by hypoxia: a potential target for hypoxic tumors of the head and neck

  • Stegeman Hanneke,
  • Kaanders Johannes H,
  • Wheeler Deric L,
  • van der Kogel Albert J,
  • Verheijen Marieke M,
  • Waaijer Stijn J,
  • Iida Mari,
  • Grénman Reidar,
  • Span Paul N,
  • Bussink Johan

DOI
https://doi.org/10.1186/1471-2407-12-463
Journal volume & issue
Vol. 12, no. 1
p. 463

Abstract

Read online

Abstract Background Only a minority of cancer patients benefits from the combination of EGFR-inhibition and radiotherapy in head and neck squamous cell carcinoma (HNSCC). A potential resistance mechanism is activation of EGFR and/or downstream pathways by stimuli in the microenvironment. The aim of this study was to find molecular targets induced by the microenvironment by determining the in vitro and in vivo expression of proteins of the EGFR-signaling network in 6 HNSCC lines. As hypoxia is an important microenvironmental parameter associated with poor outcome in solid tumors after radiotherapy, we investigated the relationship with hypoxia in vitro and in vivo. Methods Six human HNSCC cell lines were both cultured as cell lines (in vitro) and grown as xenograft tumors (in vivo). Expression levels were determined via western blot analysis and localization of markers was assessed via immunofluorescent staining. To determine the effect of hypoxia and pAKT-inhibition on cell survival, cells were incubated at 0.5% O2 and treated with MK-2206. Results We observed strong in vitro-in vivo correlations for EGFR, pEGFR and HER2 (rs=0.77, p=0.10, rs=0.89, p=0.03) and rs=0.93, p=0.02, respectively), but not for pAKT, pERK1/2 or pSTAT3 (all rs0.30). In vivo, pAKT expression was present in hypoxic cells and pAKT and hypoxia were significantly correlated (rs=0.51, p=0.04). We confirmed in vitro that hypoxia induces activation of AKT. Further, pAKT-inhibition via MK-2206 caused a significant decrease in survival in hypoxic cells (p Conclusions These data suggest that (p)EGFR and HER2 expression is mostly determined by intrinsic features of the tumor cell, while the activation of downstream kinases is highly influenced by the tumor microenvironment. We show that hypoxia induces activation of AKT both in vitro and in vivo, and that hypoxic cells can be specifically targeted by pAKT-inhibition. Targeting pAKT is thus a potential way to overcome therapy resistance induced by hypoxia and improve patient outcome.

Keywords