ABCB1 and cancer: In addition, RT-PCR analysis demonstrated that treatment with fucoxanthin, crocin, canthaxanthin, and β-carotene (listed in order of effectiveness) at a concentration of 40 μM for 48 h resulted in a reduction of ABCB1 mRNA expression levels in these cancer cells, which points to another factor responsible for ABCB1 suppression.