Luteolin induces apoptosis in multidrug resistant cancer cells without affecting the drug transporter function: involvement of cell line-specific apoptotic mechanisms.

Bioflavonoids are of considerable interest to human health as these serve as antioxidant and anticancer agents. Although epidemiological and experimental studies suggest that luteolin, a natural bioflavonoid, exhibits chemopreventive properties, its effectiveness as an antiproliferative agent against multidrug resistant (MDR) cancers is unclear. Thus, we assessed the antiproliferative effects of luteolin and associated molecular mechanisms using two MDR cancer cell lines that express high levels of P-glycoprotein and ABCG2. In this article, we demonstrate that luteolin induces apoptosis in P-glycoprotein- and ABCG2-expressing MDR cancer cells without affecting the transport functions of these drug transporters. Analysis of various proliferative signaling pathways indicated that luteolin-induced apoptosis involves reactive oxygen species generation, DNA damage, activation of ATR → Chk2 → p53 signaling pathway, inhibition of NF-kB signaling pathway, activation of p38 pathway and depletion of antiapoptotic proteins. Importantly, use of luteolin in these analyses also identified specific molecular characteristics of NCI-ADR/RES and MCF-7/Mito(R) cells that highlight their different tissue origins. These results suggest that luteolin possesses therapeutic potential to control the proliferation of MDR cancers without affecting the physiological function of drug transporters in the body tissues.