HMOX1 and cancer: Selectively cytotoxic to cancer cells but not in non-malignant oral cells; ↑ apoptosis in cancerous cells (↑ activation of caspase-8, -9, and -3); ↑ ROS levels in oral cancer cells (downregulation of antioxidant signaling genes NRF2, TXN, and HMOX1); DNA damage-inducible effects in cancer cells