Boric acid induces apoptosis in some breast cancer cell lines

Abstract

Boric acid has recently been reported to inhibit growth in prostate cancer cell lines. The following investigation demonstrates the ability of 1 mM boric acid to inhibit growth in some breast cancer cell lines. Estrogen receptor negative human breast cancer cell lines MDA-MB-231 and MDA-MB-435 cultured in MEM supplemented with 10% FBS and 25 mM Hepes did not show growth inhibition in the presence of boric acid. Estrogen receptor positive cell lines MCF-7 and T47-D cultured in MEM media or RPMI1640 media supplemented with 10% FBS and 25 mM Hepes were also growth inhibited when exposed to 1 mM boric acid. However, growth inhibition was detected in estrogen receptor positive ZR-75-1 (40% inhibition) and estrogen receptor negative SK-BR-3 (15% inhibition) human breast cancer cell lines cultured in similarly supplemented RPMI1640 media. To characterize growth inhibition, flow cytometric analysis was performed on attached and detached ZR-75-1 cells. Attached cells were not affected by boric acid while cells that had detached displayed apoptosis. Fluorescent microscopy also revealed the presence of cells undergoing apoptosis following treatment with boric acid. Boric acid appears capable of inducing apoptosis in some but not all human breast cancer cell lines independent of estrogen receptivity. Further studies will be needed to determine if boric acid treatment will be suitable for clinical application in breast cancer patients.