Putative supramolecular complexes formed by carotenoids and xanthophylls with ascorbic acid to reverse multidrug resistance in cancer cells.

Background: The molecular basis of interaction of selected carotenoids and xanthophylls with ascorbic acid on cancer cells was studied to determine their anticancer effects.

Materials And Methods: Drug accumulation was measured in a human ABCB1 gene-transfected mouse lymphoma cell line and in a human lung cancer cell line by flow cytometry; furthermore, their anticancer effects were determined in mice in vivo.

Results: Several carotenoids inhibited the multidrug resistance of cancer cells. Ascorbic acid improved the effect of certain xanthophylls, but the effect of capsanthin was not modified. Capsanthin had weak (12%) but capsorubin (85%) had a remarkable antiproliferative effect on A549 lung cancer cells. Capsorubin reduced immediate-early tumor antigen expression, while capsanthin was not effective. Capsorubin accumulates selectively in the nuclei of cancer cells.

Conclusion: The Authors suggest a special complex formation between membrane-bound capsorubin and ascorbic acid, which can be exploited in experimental chemotherapy.