Selective Estrogen Receptor Modulator Delivery of Quinone Warheads to DNA Triggering Apoptosis in Breast Cancer Cells

• Published in: ACS chemical biology 2009-12, Vol.4 (12), p.1039-1049
• Main Authors: Peng, Kuan-wei, Wang, Huali, Qin, Zhihui, Wijewickrama, Gihani T, Lu, Meiling, Wang, Zhican, Bolton, Judy L, Thatcher, Gregory R. J
• Format: Article
• Language: English
• Subjects: Apoptosis; Breast Neoplasms - metabolism; Caspase 3 - metabolism; Caspase 7 - metabolism; Catechols - chemistry; Catechols - metabolism; Cell Line, Tumor; DNA Damage; Female; Gene Deletion; Humans; Hydroquinones - chemistry; Hydroquinones - metabolism; Piperidines - chemistry; Piperidines - metabolism; Prodrugs - chemistry; Prodrugs - metabolism; Protein Binding; Reactive Oxygen Species - metabolism; Receptors, Estrogen - genetics; Receptors, Estrogen - metabolism; Selective Estrogen Receptor Modulators - chemistry; Selective Estrogen Receptor Modulators - metabolism; Thiophenes - chemistry; Thiophenes - metabolism
• ISSN: 1554-8929; 1554-8937
• DOI: 10.1021/cb9001848

Estrogen exposure is a risk factor for breast cancer, and estrogen oxidative metabolites have been implicated in chemical carcinogenesis. Oxidation of the catechol metabolite of estrone (4-OHE) and the β-naphthohydroquinone metabolite of equilenin (4-OHEN) gives o-quinones that produce ROS and damage DNA by adduction and oxidation. To differentiate hormonal and chemical carcinogensis pathways in estrogen receptor positive ER(+) cells, catechol or β-naphthohydroquinone warheads were conjugated to the selective estrogen receptor modulator (SERM) desmethylarzoxifene (DMA). ER binding was retained in the DMA conjugates; both were antiestrogens with submicromolar potency in mammary and endometrial cells. Cytotoxicity, apoptosis, and caspase-3/7 activation were compared in ER(+) and ER(−)MDA-MB-231 cells, and production of ROS was detected using a fluorescent reporter. Comparison was made to DMA, isolated warheads, and a DMA-mustard. Conjugation of warheads to DMA increased cytotoxicity accompanied by induction of apoptosis and activation of caspase-3/7. Activation of caspase-3/7, induction of apoptosis, and cytotoxicity were all increased significantly in ER(+) cells for the DMA conjugates. ROS production was localized in the nucleus for conjugates in ER(+) cells. Observations are compatible with β-naphthohydroquinone and catechol groups being concentrated in the nucleus by ER binding, where oxidation and ROS production result, concomitant with caspase-dependent apoptosis. The results suggest that DNA damage induced by catechol estrogen metabolites can be amplified in ER(+) cells independent of hormonal activity. The novel conjugation of quinone warheads to an ER-targeting SERM gives ER-dependent, enhanced apoptosis in mammary cancer cells of potential application in cancer therapy.