Preparation of caffeic acid phenethyl ester‐incorporated nanoparticles and their inhibitory effects on multiple myeloma cell growth

Abstract

Multiple myeloma (MM) is a plasma cell cancer characterized by accumulation of malignant cells, preferentially in the bone marrow, that leads to severe bone disease in humans. This disease resulted in approximately 13,000 deaths last year in the United States. Caffeic acid phenethyl ester (CAPE), a phenolic compound found in bee glue, is reported to have an array of bioactive properties including anticancer effect. We previously reported that CAPE inhibits MM cell growth through induction of apoptosis and oxidative stress. It is established that iron oxide nanoparticles (IONPs) enhance drug delivery to tissues/cells and conjugation of a small peptide RGD with drug loaded IONPs improves cancer cell targeting. The purpose of this study is to improve the biocompatibility of CAPE through encapsulation onto IONPs (IONP/CAPE) and evaluate the cytotoxic and apoptogenic effects of IONP/CAPE with RGD conjugated as a targeting ligand for human MM cells. We hypothesize that RGD-IONP/CAPE may enhance the intracellular delivery of CAPE to MM cells thus demonstrating more potent inhibition on the growth of MM cells than CAPE alone. We prepared RGD-IONP/CAPE and characterized these NPs through determination of the hydrodynamic sizes and zeta potentials. We optimized the stability of these nanomaterial complexes with various stabilizers at different pH and evaluated the inhibitory effect of the most stable formulation on MM cell growth. Our results show that the developed RGD-IONP/CAPE were stable at neutral and basic conditions, and subject to release of CAPE at acidic pH (5.5) in vitro. The RGD-IONP/CAPE caused a decreased MM cell viability in a time (24, 48, 72 hours) and dose (1, 5, 10, 20 and 30 μM) -dependent manner. Interestingly, the growth-inhibitory effects of RGD-IONP/CAPE at 10 μM was equivalent to the parent drug at 30 μM, indicating a 3-fold enhancement in CAPE delivery efficiency under the experimental condition. Apoptogenic effect of RGD-IONP/CAPE was assessed using western blotting. Protein expression of apoptosis-executioner caspase 3 was examined, and the results indicated that caspase 3 was activated. In conclusion, we constructed a novel CAPE-loaded IONPs with RGD conjugation which showed more potent antimyeloma effect than parental CAPE.