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A DPhil project available with Peter Ratcliffe, Tammie Bishop and Tom Keeley, Ludwig Institute for Cancer Research, Nuffield Department of Medicine, University of Oxford

Laboratories

The student will be supervised by Professor Peter Ratcliffe, Dr Tammie Bishop and Dr Tom Keeley at Ludwig Oxford. Their research group aims to understand the mechanisms of hypoxia signalling and their relevance to the developmental origins of inherited ‘pseudohypoxic’ cancers.

Project

Hypoxia-inducible factor (HIF), a transcription factor that mounts gene expression changes to low oxygen, is commonly activated in cancer and its role in oncogenesis has attracted widespread interest, particularly in view of the recent development and clinical licensing of drugs with the potential to activate or inactivate components of the HIF pathway therapeutically. Although HIF operates ubiquitously across cell types and is commonly upregulated in cancer, direct genetic activation by mutation of any of the key components of the HIF pathway is rare in most forms of cancer. An important exception to this are tumours of the autonomic paraganglia that arise in diverse anatomical locations from the skull base to the pelvis, known as pheochromocytomas and paragangliomas (PPGLs). These tumours are highly heritable with almost half of these tumours bearing an inherited, germline (or post zygotic but early somatic) mutation and mutations that result in activation of HIF (in the absence of hypoxia per se i.e. ‘pseudohypoxia’) are particularly common1.

In an effort to understand this paradox and gain insights into the pathogenesis of pseudohypoxic PPGL, we have constructed mice in which the dominant negative regulator of HIF (HIF prolyl hydroxylase 2, Phd2) is inactivated and show that activation of HIF-2 during development drives a lineage shift towards the formation of immature/noradrenergic adrenal medullas with close similarities to pseudohypoxic PPGLs2,3. Interestingly, these abnormalities include a HIF-2 dependent pattern of gene expression with similar features to the carotid body, an arterial chemoreceptor that mounts rapid (<1 min) neurosecretory responses to low oxygen to mediate hypoxic ventilatory control and whose signalling mechanisms remain unknown but involve HIF-24,5. This project will test whether developmental activation of HIF-2 in chromaffin cells confers not just a carotid body-like transcriptome but also function i.e. oxygen sensitivity. This project is expected to deliver insights into the mechanisms of acute oxygen sensing and also inform translational strategies in the treatment of PPGLs, given the recent clinical licensing of HIF-2alpha antagonists in the treatment of cancer6,7,8,9.

Training

In this project, transgenic mice will be used to dissect the role of HIF-2 in PPGL tumourigenesis and acute oxygen sensing. The student will be trained in modern techniques involving fluorescence microscopy to detect changes in intracellular Ca2+ in tissue slices in response to acute hypoxic exposure and concurrent to amperometry in collaboration with Professors Keith Buckler and Patrik Rorsman; use of clinically licensed HIF-2alpha antagonists in vivo to test reversability; and single cell RNAseq for transcriptomic profiling. A long-term aim is to develop cell lines from PPGLs which retain oxygen sensitivity, for example, using a tissue-restricted, ON-OFF controllable, oncogenic driver (e.g. c-Myc, SV40 large T antigen) using specialist approaches in order to preserve characteristics of electrophysiological sensing.

References

  1. Dahia, PLM et al. Recognising hypoxia in phaeochromocytomas and paragangliomas. Nat Rev Endocrinol 16, 191-192 (2020).
  2. Eckardt, L. et al. Developmental role of PHD2 in the pathogenesis of pseudohypoxic pheochromocytoma. Endocr Relat Cancer 28, 757-772, doi:10.1530/ERC-21-0211 (2021).
  3. Fielding, J. W. et al. PHD2 inactivation in Type I cells drives HIF-2alpha-dependent multilineage hyperplasia and the formation of paraganglioma-like carotid bodies. J Physiol, doi:10.1113/JP275996 (2018).
  4. Cheng, X. et al. Marked and rapid effects of pharmacological HIF-2alpha antagonism on hypoxic ventilatory control. J Clin Invest 130, 2237-2251, doi:10.1172/JCI133194 (2020).
  5. Hodson, E. et al. Regulation of ventilatory sensitivity and carotid body proliferation in hypoxia by the PHD2/HIF-2 pathway. J Physiol 594, 1179-1195 (2016).
  6. Courtney, K. D. et al. Phase I Dose-Escalation Trial of PT2385, a First-in-Class Hypoxia-Inducible Factor-2alpha Antagonist in Patients With Previously Treated Advanced Clear Cell Renal Cell Carcinoma. J Clin Oncol 36, 867-874, doi:10.1200/JCO.2017.74.2627 (2018).
  7. Cho, H. et al. On-target efficacy of a HIF-2alpha antagonist in preclinical kidney cancer models. Nature 539, 107-111, doi:10.1038/nature19795 (2016).
  8. Wallace, E. M. et al. A Small-Molecule Antagonist of HIF2alpha Is Efficacious in Preclinical Models of Renal Cell Carcinoma. Cancer Res 76, 5491-5500, doi:10.1158/0008-5472.CAN-16-0473 (2016).
  9. Kamihara, J et al. Belzutifan, a potent HIF-2alpha inhibitor, in the Pacak-Zhuang syndrome. N Eng J Med 385, 2059-2065 (2021).