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Figure 5 | Breast Cancer Research

Figure 5

From: Insulin-like growth factor 1 attenuates antiestrogen- and antiprogestin-induced apoptosis in ER+ breast cancer cells by MEK1 regulation of the BH3-only pro-apoptotic protein Bim

Figure 5

MEK1 regulates oxidative stress and mitochondrial membrane function in ER+ breast cancer cells. (a through c) MEK1 downregulation blocked the prosurvival effects of IGF-1 and enhanced ROS and mitochondrial membrane depolarization in hormonally treated breast cancer cells. (a) Western blot shows effective RNAi targeting of MEK1, which was carried out for 48 hours before cells were treated with E2, E2 + 4-OHT, or E2 + 4-OHT + MIF for 24 hours. Protein was isolated from cells and analyzed for MEK1 expression with immunoblot analysis. (b, c) Cell populations with reduced MEK1 expression were analyzed at 6 and 72 hours for ROS and mitochondrial membrane depolarization, respectively. (d through f) MEK1 overexpression reduced ROS and mitochondrial membrane depolarization in hormonally treated breast cancer cells. Transient transfection of MEK1 cDNA (MEK1-GFP vector) increased MEK1 expression above levels seen in vector-only (pEGFP-1)-transfected control cells at 24 and 48 hours, as determined by immunoblot analysis (d), and reduced ROS levels and mitochondrial membrane depolarization at 24 and 72 hours, respectively (e, f). Values are expressed as mean ± SD (n = 3). Significant differences are designated as follows: (a) Scrambled versus SiMEK, E2 (± IGF-1); (b) Scrambled versus SiMEK, E2 + 4-OHT (± IGF-1); (c) Scrambled versus SiMEK, E2 + MIF (± IGF-1); (d) Scrambled versus SiMEK, E2 + 4-OHT + MIF; (e) pEGFP-N1 versus MEK1-GFP, E2 + 4-OHT; (f) pEGFP-N1 versus MEK1-GFP, E2 + MIF; (g) pEGFP-N1, E2 + 4-OHT + MIF versus MEK1-GFP, E2 + 4-OHT + MIF. *P < 0.001.

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