BMAL1 and breast cancer: In addition, the protein and mRNA levels of BMAL1 in MCF-7 and MDA-MB-231 breast cancer cells were reduced in chronic hypoxia but unchanged when the pH of the medium was neutralized by NaOH (Figure 2c,d) or buffered by NaHCO3 (Figure 2e,f and Supplementary Figure S2b).