PGP and neoplasm: Resveratrol (RSV), which is a polyphenol comes from grape and Chinese medicine Rhizoma polygoni cuspidati, was found to downregulate the expression of MRP1 and P-gp in DOX-resistant breast cancer cells, promoting the accumulation of DOX in resistant cells and thus enhancing the effects of chemotherapy in MDA-MB-231/ADR tumor-bearing mice 75.