Modulation of multidrug resistance gene expression in human breast cancer cells by (-)-gossypol-enriched cottonseed oil.

BACKGROUND

Multidrug resistance (MDR) is a major impediment to successful cancer chemotherapy. P-glycoprotein (P-gp), the product of the multidrug resistance 1 (MDR1) gene, acts as an efflux pump and prevents sufficient intracellular accumulation of several anticancer agents, thus, playing a major role in MDR. Tamoxifen (Tam), ICI 182 780 (ICI) and Adriamycin (Adr) alone or with (-)-gossypol-enriched cottonseed oil [(-)-GPCSO] possible effects on cell growth inhibition and regulation of MDR1, mRNA and P-gp expression were examined in both an MDR human breast cancer cell line, MCF-7/Adr cells, and primary cultured human breast cancer epithelial cells (PCHBCEC).

METHODS

Cells were treated with 0.05% of (-)-GPCSO either in the absence or presence of either 0.1 microM Tam, ICI or Adr for 24 h.

RESULTS

Using the non-radioactive cell proliferation MTS assay, none of these chemotherapeutic agents alone inhibited MCF-7/Adr cell and PCHBCEC proliferation; meanwhile, the combination of 0.1 microM Tam, ICI or Adr with 0.05% (-)-GPCSO significantly reduced MCF-7/Adr cell growth by approximately 34%, 32% and 23%, respectively, of that of the vehicle-treated cells. For PCHBCEC, the combination of 0.05% (-)-GPCSO with 0.1 microM of Tam, ICI and Adr reduced cell growth to about 94%, 90%, and 71% respectively, of the vehicle treated PCHBCEC. Furthermore, (-)-GPCSO inhibited MDR1/P-gp expression in both MCF- 7/Adr and PCHBCEC in a dose-dependent manner. Our results provide insight into the MDR-reversing potential of (-)-GPCSO in human breast cancer cells resistant to current chemotherapeutic agents.