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  GRHL3, Long ncRNA Gas5, TA-p73, TAp63, p53, and others, induces regression of p53-mutated human tumors, via down regulation of its target gene, 27/June/2018, 10.14 pm