p53-Dependent ENOX2 Downregulation Mediates the Apoptotic Responses to Heteroarene-Fused Anthraquinones in Colon Cancer Cells

Anthraquinone-based intercalating compounds, such as doxorubicin and mitoxantrone, have long been used clinically due to their ability to induce DNA damage. More recently, heteroarene-fused anthraquinones have been developed to further enhance their anticancer activity. Among these compounds, 4,11-bis(2-(2-chloroacetamidine)ethylamino)anthra[2,3-b]thiophene-5,10-dione dihydrochloride (designated as derivative a) was identified as a potent apoptotic inducer. Based on this scaffold, two additional derivatives were synthesized by replacing the sulfur atom within the heterocyclic ring with nitrogen (derivative b) or oxygen (derivative c). Building upon our previous identification of ENOX2 as the primary target of this scaffold, the present study investigated the anti-proliferative effects and underlying mechanisms of these derivatives in colon cancer cells with varying p53 statuses. Derivatives a and b effectively induced apoptosis and suppressed proliferation in p53 wild-type HCT116 cells, which was concomitantly accompanied by significant ENOX2 downregulation and the activation of intrinsic apoptotic signaling. In contrast, p53-null HCT116 cells exhibited reduced sensitivity, attenuated apoptotic responses, and minimal ENOX2 downregulation. Notably, derivative c primarily induced G2/M arrest rather than apoptosis regardless of p53 status, indicating a predominantly cytostatic mechanism. Collectively, these findings suggest that the degree of ENOX2 modulation is linked to the distinct anti-proliferative responses induced by heteroarene-fused anthraquinones, and that p53 status serves as a critical molecular switch influencing the transition between cytostatic growth arrest and apoptotic cell death.