Folate-Gold-Bilirubin Nanoconjugate Induces Apoptotic Death in Multidrug-Resistant Oral Carcinoma Cells.

BACKGROUND: Gold nanoparticles (GNPs) are receiving increasing attention as drug delivery carriers due to their high surface-to-volume ratio, hydrophilicity, and functionality. Drug delivery by nanocarriers has the potential to bypass P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) by altering the drug internalization mechanism and/or intracellular release pattern, inhibiting the activity of ABC-transporter efflux pumps, or downregulating the expression of genes responsible for the activity of efflux pumps. OBJECTIVE: We developed a folate-gold-bilirubin (FGB) nanoconjugate to reverse MDR in P-expressing KB-Ch(R)-8-5 cells. METHODS: The P-gp overexpressing KB-Ch(R)-8-5 cells were incubated with the FGB nanoconjugate, bilirubin, or GNPs. Various cellular endpoints, such as cytotoxicity, ROS generation, DNA damage, and apoptosis, were analyzed using analytical methods. Further, a KB-Ch(R)-8-5 cell-bearing tumor xenograft was developed and the anticancer potential of the prepared FGB nanoparticles was compared to that of bilirubin or GNPs in this preclinical model. RESULTS: The FGB nanoconjugate was found to be a stronger inhibitor of the viability of multidrug-resistant KB-Ch(R)-8-5 cells than bilirubin and GNPs treatment alone. The nanoconjugate induced reactive oxygen species (ROS) formation, DNA strand breaks, and apoptotic morphological changes in the P-gp-overexpressing drug-resistant cells to a greater degree than bilirubin treatment alone. Also, the FGB nanoparticles led to stronger suppression of tumor development in the KB-Ch(R)-8-5 xenograft mouse model than achieved with bilirubin treatment alone. Thus, the present results suggest that the FGB nanoconjugate suppresses tumor growth in drug-resistant tumor cells by inducing apoptotic cell death. CONCLUSION: FGB nanoparticles significantly inhibit tumor growth, probably through the folate receptor, which is highly expressed in KB cells. Hence, folate-gold-bilirubin nanoparticles could be a promising agent for inducing apoptosis in P-gp-overexpressing drug-resistant cancer cells.