Tocotrienols inhibit growth of ZR-75-1 breast cancer cells

Int J Food Sci Nutr. 2000;51 Suppl:S95-103.

Abstract

The vitamin E component of palm oil provides a rich source of tocotrienols which have been shown previously to be growth inhibitory to two human breast cancer cell lines: responsive MCF7 cells and unresponsive MDA-MB-231 cells. Data presented here shows that the tocotrienol-rich fraction (TRF) of palm oil and individual fractions (alpha, gamma and delta) can also inhibit the growth of another responsive human breast cancer cell line, ZR-75-1. At low concentrations in the absence of oestrogen tocotrienols stimulated growth of the ZR-75-1 cells, but at higher concentrations in the presence as well as in the absence of oestradiol, tocotrienols inhibited cell growth strongly. As for MCF7 cells, alpha-tocopherol had no effect on growth of the ZR-75-1 cells in either the absence or presence of oestradiol. In studying the effects of tocotrienols in combination with antioestrogens, it was found that TRF could further inhibit growth of ZR-75-1 cells in the presence of tamoxifen (10(-7) M and 10(-8) M). Individual tocotrienol fractions (alpha, gamma, delta) could inhibit growth of ZR-75-1 cells in the presence of 10(-8) M oestradiol and 10(-8) M pure antioestrogen ICI 164,384. The immature mouse uterine weight bioassay confirmed that TRF could not exert oestrogen antagonist action in vivo. These results provide evidence of wider growth-inhibitory effects of tocotrienols beyond MCF7 and MDA-MB-231 cells, and with an oestrogen-independent mechanism of action, suggest a possible clinical advantage in combining administration of tocotrienols with antioestrogen therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antineoplastic Agents, Phytogenic / pharmacology
  • Antineoplastic Agents, Phytogenic / therapeutic use*
  • Breast Neoplasms / drug therapy*
  • Cell Division / drug effects
  • Estradiol / physiology
  • Estrogen Antagonists / pharmacology
  • Female
  • Humans
  • Mice
  • Tamoxifen / pharmacology
  • Tumor Cells, Cultured / drug effects
  • Uterus / drug effects
  • Vitamin E / pharmacology
  • Vitamin E / therapeutic use*

Substances

  • Antineoplastic Agents, Phytogenic
  • Estrogen Antagonists
  • Tamoxifen
  • Vitamin E
  • Estradiol