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Question 6#

The loss of function of the VHL protein in renal cell carcinoma is mediated by which of the following? 

A. Bcl-2
B. Hypoxia-inducible factor alpha
C. Fibroblast growth factor-3
D. Transforming growth factor beta-1
E. Vascular endothelial growth factor

Correct Answer is B

Comment:

Answer B

Hypoxia inducible factors are transcription factors that respond to a decrease in oxygen levels on the cellular environment. Inactivation of the VHL protein leads to upregulation of HIF-2 alpha, which in turn leads to upregulation of VEGF, erythropoietin and PEGF. VEGF binds to a tyrosine kinase enzyme (VEGFR-2) on endothelial cells promoting tumour angiogenesis.