FBXO21 and acute myeloid leukemia: However mass spectrometry combined with our genomic dataset revealed p85α (PIK3R1) as the ubiquitination target of FBXO21. p85α (PIK3R1) expression is significantly upregulated in AML and increased expression correlates with a worse survival rate, and PI3K pathway is among one of the most frequently upregulated intracellular pathways [6, 37, 38].