And FAO, ATP level and cell growth increasing in sh-Sun2-downexpressing prostate cancer cells could be reversed by SAA1 interference Serum amyloid A protein (SAA) is an apolipoprotein that can replace apolipoprotein A1 (apoA1) as the major apolipoprotein of high density lipoprotein (HDL). The gene discussed is SAA1; the disease is prostate carcinoma.