MCF‐7 breast cancer cell internal pH regulation

Tumors create an extracellular pH (pH e ) barrier and form an isolated microenvironment roughly 0.5 pH units lower than physiological pH, while the intracellular pH (pH i ) is maintained within 0.2 pH units of physiological levels. Reduced tumor pH i is associated with apoptosis, and lowered arterial and tissue pH are seen with heavy exercise. PURPOSE To determine the pH i response of MCF‐7 cells subjected to acidic environments. MCF‐7 cells loaded with BCECF, a pH indicator, were used to create a standard curve of fluorescent ratios at six pH levels. MCF‐7 cells were then subjected to pH e levels of 6.75 and 6.25 at 0, 15, 30, 45, 60, 120, 180, and 1,440 minutes of pH e exposure. Data were referenced to MCF‐7 cells at a physiological pH e of 7.25. A treatment effect was seen at pH e 6.25 (p = 0.0002). Compared to the control, cells subjected to pH e 6.25 for 15, 30, 45, and 1,440 minutes had lower pH i levels (p = 0.0464, p = 0.0002, p = 0.0257, and p = 0.0054, respectively). An interaction of pH e and time (p = 0.0483) on pH i was observed. The pH i values were lower at pH e 6.25 than at pH e 6.75 after 30, 180, and 1,440 minutes of exposure (p = 0.0193, p = 0.0200, and p < 0.0001, respectively). In conclusion, MCF‐7 cells subjected to a pH e of 6.75 maintained their pH i , but a different recovery response was seen at pH e 6.25. A decreased tolerance of lower pH levels may provide a mechanism by which heavy exercise would prove beneficial for breast cancer patients.