XIAP and cancer: Most importantly, treatments of cancer cells with several signaling perturbation agents such as Nanog siRNA or Stat-3siRNA or an anti-miR-21 inhibitor result in downregulation of survival proteins (e.g., cIAP-1, cIAP-2, and XIAP) and upregulation of PDCD4 leading to tumor cell apoptosis/death and chemosensitivity in head and neck cancer (19, 65–67).