Treatments with Hcy-thiolactone, N-Hcy-protein, or Hcy (which were all severely elevated in Cbs−/− mice; [15,16,17,18]) or Cbs gene silencing by RNA interference significantly reduced Phf8 expression and increased total H4K20me1 as well as mTOR promoter-bound H4K20me1 in mouse neuroblastoma N2a and N2a-APPswe cells. The gene discussed is MTOR; the disease is neuroblastoma.