VEGFB and neoplasm: Although FH deficiencies promote a stabilization of HIF1A expression secondary to increased cellular fumarates27, the expression of most HIF1 downstream targets, including vascular endothelial growth factor A (VEGFA) and VEGFB, were unexpectedly decreased in tumor tissue due to a truncated HIF1ɑ splice variant lacking exon 10 in Patient-128.