ABCB1 and neoplasm: Further, consistent with triptolide-induced suppression of ABCB1 in vitro, IHC revealed a significant increase in ABCB1 protein levels in tumor sections from A549/PR xenograft mice compared with A549 xenograft mice, while triptolide treatment dramatically decreased the protein level of ABCB1 in the A549/PR group (Fig. 2h).