Estrogen-induced G1/S transition of G0-arrested estrogen-dependent breast cancer cells is regulated by mitochondrial oxidant signaling

Abstract

We previously reported that 17-b-estradiol (E2)-induced mitochondrial reactive oxygen species (mtROS) act as signaling molecules. The purpose of this study was to investigate the effects of E2-induced mtROS on cell cycle progression. E2-induced cell growth was reduced by antioxidants N-acetyl-L-cysteine (NAC), catalase, and the glutathione peroxidase mimic ebselen. Flow cytometry showed that mitochondrial blockers of protein synthesis (chloramphenicol), transcription and replication (ethidium bromide), and function (rotenone, rhodamine 6G) blocked E2-induced G 1 to S transition. Reduction of E2-induced DNA synthesis in the presence of mitochondrial blockers occurred without influencing the level of ATP. Additionally, the mitochondrial blockers inhibited the E2-induced expression of early cell cycle genes such as cyclins D1, D3, E1, E2, and B2. NAC or rotenone reduced E2-induced cyclin D1 expression. Furthermore, E2-induced binding of AP-1 and CREB to the TRE and CRE response sequences, respectively, in the promoter of cyclin D1 was inhibited by NAC or rotenone. In addition, E2-induced expression of PCNA, PRC1, and bcl-2 were inhibited by mitochondrial blockers. These data indicate that E2-induced mtROS are involved in the regulation of early G 1 -phase progression. Since neither antioxidants nor mitochondrial blockers used in this study are reported to bind the estrogen receptor (ER), our findings suggest that E2-induced mtROS modulates G 1 to S transition and some of the early G 1 genes through a nongenomic, ERindependent signaling pathway. Thus, our results suggest (1) a new paradigm that estrogen-induced mitochondrial oxidants control the early stage of cell cycle progression and (2) provide the basis for the discovery of novel antioxidant-based drugs or antioxidant gene therapies for the prevention and treatment of estrogen-dependent breast cancer.

Nitrite-Mediated Modulation of HL-60 Cell Cycle and Proliferation: Involvement of Cyclin-Dependent Kinase 2 Activation

“…Mitochondria have been found to play a central role in cell cycle regulation (Mitra et al, 2009). Moreover, disruption of the mitochondrial electron transport chain specifically retards the G 1 -to S-phase transition (Felty et al, 2005;Owusu-Ansah et al, 2008). Incidentally, we and others have reported that mitochondria are potential NO targets and affect ATP generation, apoptosis, and cell cycle (Brookes et al, 2000;Kumar et al, 2010).…”

“…It is noteworthy that growth factors stimulate rapid increase in intracellular ROS that modulate signaling involved in cell growth (Sattler et al, 1999;Felty et al, 2005). The G 1 -to S-phase transition in fibroblasts depends on the intracellular redox status (Menon et al, 2003).…”

“…Cell cycle and proliferation are under redox regulation (Felty et al, 2005;Lu et al, 2007;Menon and Goswami, 2007;Kumar et al, 2010). It is noteworthy that growth factors stimulate rapid increase in intracellular ROS that modulate signaling involved in cell growth (Sattler et al, 1999;Felty et al, 2005).…”

Estrogen Signaling and Thyrocyte Proliferation

“…Signaling cascades involving protein tyrosine kinases can be enhanced by oxidative inhibition of protein tyrosine phosphatases, and pathways involving NF-kB, JNK, p38 MAPK, and AP-1 are strongly responsive to redox regulation (Droge, 2002). Recent data have suggested that physiological concentrations of E2 trigger a rapid production of intracellular reactive oxygen species (ROS) in endothelial and epithelial cells, and that E2-induced DNA synthesis is at least in part mediated by ROS signaling in these cells (Felty et al, 2005;Felty, 2006). This notion is particularly intriguing, since E2-mediated ROS production in thyroid follicular cells would have two effects: an immediate stimulation of cell proliferation, and a long-term accumulation of oxidative DNA damage.…”

Treatment with bisphenol A and methoxychlor results in the growth of human breast cancer cells and alteration of the expression of cell cycle-related genes, cyclin D1 and p21, via an estrogen receptor-dependent signaling pathway

“…Data represent the mean ± SD of triplicate experiments. (25). The G1/S transition during the cell cycle involves many important cell cycle-related genes such as cyclin D1, p21, and cdk 4; the expression of these genes may be specifically altered in breast cancer cells (26).…”