PIK3CD and posterior cortical atrophy: PI3K, a plasma membrane-associated protein kinase, is formed by two functional subunits: a catalytic subunit (p110α, p110β, or p110δ) and a regulatory subunit (p85α, p55α, p50α, p85β, or p55γ isoform).383 The catalytic subunit p110β is believed to be the most relevant isoform for PCa progression.384,385 PI3K inhibitors, such as BKM120 and PX866, target the catalytic subunits of all three isoforms (p110α, p110β, and p110δ).