Quercetin induced apoptosis in association with death receptors and fludarabine in cells isolated from chronic lymphocytic leukaemia patients.

BACKGROUND: Quercetin is a flavonoid naturally present in food and beverages belonging to the large class of phytochemicals with potential anti-cancer properties. Here, we investigated the ability of quercetin to sensitise primary cells from chronic lymphocytic leukaemia (CLL) to death receptor (DR) agonists, recombinant TNF-related-apoptosis-inducing ligand (rTRAIL) and anti-CD95, and to fludarabine, a widely used chemotherapeutic drug against CLL. METHODS: Peripheral white blood cells were isolated from patients and incubated with medium containing 50 ng ml anti-CD95 agonist antibody; 10 ng ml recombinant TRAIL; 10-25 microM quercetin and 3.5-14 microM fludarabine. Neutral Red assay was used to measure cell viability, where as apoptosis was assessed by determining caspase-3 activity, exposure to Annexin V and PARP fragmentation. RESULTS: Quercetin significantly enhanced anti-CD95- and rTRAIL-induced cell death as shown by decreased cell viability, increased caspase-3 and -9 activities, and positivity to Annexin V. In addition, association of quercetin with fludarabine increases the apoptotic response in CLL cells of about two-fold compared with quercetin monotreatment. CONCLUSION: This work shows that resistance to DR- and fludarabine-induced cell death in leukaemic cells isolated from CLL patients can be ameliorated or bypassed by the combined treatment with quercetin. Considering the low toxicity of the molecule, our study results are in favour of a potential use of quercetin in adjuvant chemotherapy in combination with other drugs.