STAT3 and cancer: The NCI have identified the quinone moiety as an important pharmacophore element for anti-cancer drugs [40] because it possesses several tumor-selective activities such as anti-proliferative and anti-angiogenesis activity [41, 42], ability to induce oxidative stress, apoptosis and necrosis [43], ability to inhibit DNA replication [44], ability to suppress glycolysis and mitochondrial function [15], and ability to inhibit NF-κB and STAT3 signaling [37, 45].