Modification of nuclearcytoplasmic protein transport: Specific inhibition of the cellular adaptation to intratumoral hypoxia

• Applicant: Dr. Friederike Katharina Kosyna
• Subject Area: Anatomy and Physiology ; Cell Biology
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 390362861

Oxygen-dependent gene expression is of physiological and pathophysiological importance. The adaptation to changes in oxygen tension is regulated by specific transcription factors that belong to the family of hypoxia-inducible factors (HIF). Under normoxic conditions, HIFs are hydroxylated by the HIF-prolyl hydroxylases PHD1, PHD2 and PHD3 following proteasomal degradation. The three prolyl hydroxylases show tissue- and compartment-specific expression patterns. For all three PHD-isoforms nuclear transport signals could be identified, whereby the transport of PHD1 and PHD3 into the nucleus is importin alpha/beta-dependent. The impact of PHDs varying subcellular distribution patterns as well as tightly regulated nuclear transport mechanisms is hitherto hardly known. Recently, clinical studies showed that the malignancy of several tumors is associated with the expression and nuclear translocation of specific PHDs. These results indicate that the nucleo-cytoplasmic protein transport is of particular importance for this regulatory network.Two-dimensional (2D)-cell culture systems reflect cellular in vivo conditions only to a limited extend. In contrast, three-dimensional (3D)-cell cultures more closely resemble in vivo conditions. Therefore, a multicellular tumor spheroid model should be established for this project providing gradients of nutrients, oxygen and metabolites as well as areas with different proliferation rates.This project focusses on the influence of subcellular PHD localization and expression patterns on adaptive processes of tumors to intratumoral hypoxia. For this, subcellular transport of the three PHD isoforms should be inhibited by specific peptides corresponding to the identified nuclear transport signals. Moreover, PHD expression should be modulated by knockdown or overexpression in spheroidal tumor cells. Effects of this modified PHD expression should be detected by characterization of cell viability and growth of tumor spheroids. Further on, the impact of these aspects on irradiated tumor spheroids should be evaluated. All in all, it has to be elucidated if the inhibition of nuclear PHD import or modification of the expression of the oxygen sensor proteins PHD1, PHD2 and PHD3 has therapeutic potential for the development of new strategies to fight cancer.

• DFG Programme: Research Grants