Prolyl hydroxylase 2 dependent and Von-Hippel-Lindau independent degradation of Hypoxia-inducible factor 1 and 2 alpha by selenium in clear cell renal cell carcinoma leads to tumor growth inhibitionReport as inadecuate

Prolyl hydroxylase 2 dependent and Von-Hippel-Lindau independent degradation of Hypoxia-inducible factor 1 and 2 alpha by selenium in clear cell renal cell carcinoma leads to tumor growth inhibition - Download this document for free, or read online. Document in PDF available to download.

BMC Cancer

, 12:293

First Online: 17 July 2012Received: 28 November 2011Accepted: 27 June 2012DOI: 10.1186-1471-2407-12-293

Cite this article as: Chintala, S., Najrana, T., Toth, K. et al. BMC Cancer 2012 12: 293. doi:10.1186-1471-2407-12-293


BackgroundClear cell renal cell carcinoma ccRCC accounts for more than 80% of the cases of renal cell carcinoma. In ccRCC deactivation of Von-Hippel-Lindau VHL gene contributes to the constitutive expression of hypoxia inducible factors 1 and 2 alpha HIF-α, transcriptional regulators of several genes involved in tumor angiogenesis, glycolysis and drug resistance. We have demonstrated inhibition of HIF-1α by Se-Methylselenocysteine MSC via stabilization of prolyl hydroxylases 2 and 3 PHDs and a significant therapeutic synergy when combined with chemotherapy. This study was initiated to investigate the expression of PHDs, HIF-α, and VEGF-A in selected solid cancers, the mechanism of HIF-α inhibition by MSC, and to document antitumor activity of MSC against human ccRCC xenografts.

MethodsTissue microarrays of primary human cancer specimens ccRCC, head and neck and colon were utilized to determine the incidence of PHD2-3, HIF-α, and VEGF-A by immunohistochemical methods. To investigate the mechanisms of HIF-α inhibition by MSC, VHL mutated ccRCC cells RC2 HIF-1α positive, 786–0 HIF-2α positive and VHL wild type head and neck cancer cells FaDu HIF-1α were utilized. PHD2 and VHL gene specific siRNA knockdown and inhibitors of PHD2 and proteasome were used to determine their role in the degradation of HIF-1α by MSC.

ResultsWe have demonstrated that ccRCC cells express low incidence of PHD2 32%, undetectable PHD3, high incidence of HIF-α 92%, and low incidence of VEGF-A compared to head and neck and colon cancers. This laboratory was the first to identify MSC as a highly effective inhibitor of constitutively expressed HIF-α in ccRCC tumors. MSC did not inhibit HIF-1α protein synthesis, but facilitated its degradation. The use of gene knockdown and specific inhibitors confirmed that the inhibition of HIF-1α was PHD2 and proteasome dependent and VHL independent. The effects of MSC treatment on HIF-α were associated with significant antitumor activity against ccRCC xenograft.

ConclusionsOur results show the role of PHD2-3 in stable expression of HIF-α in human ccRCC. Furthermore, HIF-1α degradation by MSC is achieved through PHD2 dependent and VHL independent pathway which is unique for HIF-α regulation. These data provide the basis for combining MSC with currently used agents for ccRCC.

KeywordsProlyl hydroxylases Hypoxia-inducible factor Clear cell renal cell carcinoma Selenium AbbreviationsCCRCCClear cell renal cell carcinoma

HIF-1αHypoxia inducible factor-1 alpha

HIF-2αHypoxia inducible factor 2 alpha

HIF-αHIF-1α and HIF-2α

PHDProlyl hydroxylase


VEGFVascular endothelial growth factor

SiRNASmall interfering RNA


MSAMethylselenic acid

DMOGDimethyloxallyl glycine

MG132N-phenylmethoxycarbonyl-L-leucyl-N-1 S-1-formyl-3-methylbutyl-L-leucinamide

TMATissue microarray

DBBRData bank and bioRepository

EGLN1Egg-laying-defective nine1.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2407-12-293 contains supplementary material, which is available to authorized users.

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Author: Sreenivasulu Chintala - Tanbir Najrana - Karoly Toth - Shousong Cao - Farukh A Durrani - Roberto Pili - Youcef M Rustum



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