Inhibition of Siah ubiquitin ligase function.
Tumor hypoxia induces the upregulation of hypoxia-inducible factor 1alpha (Hif-1alpha), which in turn induces the expression of genes including VEGF to recruit new blood vessel outgrowth, enabling tumor growth and metastasis. Interference with the Hif-1 pathway and neoangiogenesis is an attractive antitumor target. The hydroxylation of Hif-1alpha by prolyl-hydroxylase (PHD) proteins during normoxia serves as a recognition motif for its proteasomal degradation. However, under hypoxic conditions, hydroxylation is inhibited and furthermore, PHD proteins are themselves polyubiquitylated and degraded by Siah ubiquitin ligases. Our data demonstrate for the first time that inhibition of the interaction between Siah and PHD proteins using a fragment derived from a Drosophila protein (phyllopod) interferes with the PHD degradation. Furthermore, cells stably expressing the phyllopod fragment display reduced upregulation of Hif-1alpha protein levels and Hif-1-mediated gene expression under hypoxia. In a syngeneic mouse model of breast cancer, the phyllopod fragment reduced tumor growth and neoangiogenesis and prolonged survival of the mice. In addition, levels of Hif-1alpha and its target Glut-1 are reduced in tumors expressing the phyllopod fragment. These data show, in a proof-of-principle study, that Siah protein, the most upstream component of the hypoxia pathway yet identified, is a viable drug target for antitumor therapies.
Cancer Genomics and Biochemistry Laboratory, Peter MacCallum Cancer Centre, St Andrew's Place, Victoria, Australia.
A
A
Möller
C M
CM
House
C S F
CS
Wong
D B
DB
Scanlon
M C P
MC
Liu
Z
Z
Ronai
D D L
DD
Bowtell
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001943:Breast Neoplasms / Q000473:pathology; D015687:Cell Hypoxia / Q000235:genetics; D045744:Cell Line, Tumor / Q000378:metabolism / Q000637:transplantation; D049308:Dioxygenases / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D016503:Drug Delivery Systems; D005260:Female; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis / Q000235:genetics; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D008325:Mammary Neoplasms, Experimental / Q000098:blood supply / Q000201:enzymology; D051379:Mice; D008810:Mice, Inbred C57BL; D009363:Neoplasm Proteins / Q000502:physiology; D009389:Neovascularization, Pathologic / Q000201:enzymology / Q000517:prevention & control; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology*; D010446:Peptide Fragments / Q000235:genetics / Q000502:physiology*; D011393:Procollagen-Proline Dioxygenase / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors* / Q000502:physiology; D054875:Ubiquitination; D023041:Xenograft Model Antitumor Assays; D000098563:Seven in Absentia Proteins
D000970:Antineoplastic Agents; D029721:Drosophila Proteins; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011506:Proteins; D011993:Recombinant Fusion Proteins; C092070:phyl protein, Drosophila; D049308:Dioxygenases; C522722:PHD3 protein, mouse; D011393:Procollagen-Proline Dioxygenase; C488894:EGLN3 protein, human; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; C484442:Siah1a protein, mouse; D044767:Ubiquitin-Protein Ligases; D000098563:Seven in Absentia Proteins; D046988:Proteasome Endopeptidase Complex