HIF1A and breast cancer: When these cells were incubated in a 1% O2 hypoxic condition for 24 h, levels of HIF-1α accumulation were substantially diminished in NRF2-silenced breast cancer cells compared to that in the control cell lines (Fig. 1A and B), which is in agreement with our previous report showing that HIF-1α accumulation is abrogated in NRF2-silenced colon cancer cells [29].