Awakening the sleeping/cancer-protecting angels in mutant p53-expressing human tumors: Sitagliptin (trade name: Januvia), a DPP4 inhibitor, increases the expression of tumor suppressors genes, such as  p53, TA-p73 and TA-p63, BTG2 and INK4a, and others, induces regression of p53-mutated human tumors, via down regulation of its target gene, 16/June/2017, 11.48 pm