PGP and cancer: Gamma‐tocotrienol action in cancer treatment attenuated the expression levels of MDR‐1 and P‐gp mRNA, in an in vitro study utilizing MCF‐7/Adriamycin breast cancer cell line, which also demonstrated its ability to reverse the drug efflux by using NF‐kB agonists/antagonists, MDR‐1 promoter activity, and P‐gp transporter activity.163