DEVELOPMENT OF CHLORAMBUCIL/HYDROXYCHLOROQUINE-LOADED ANTI-CD20 NANOPARTICLES FOR THE TREATMENT OF CHRONIC LYMPHOCYTIC LEUKEMIA : IN VITRO MODEL

DEVELOPMENT OF CHLORAMBUCIL/HYDROXYCHLOROQUINE-LOADED ANTI-CD20 NANOPARTICLES FOR THE TREATMENT OF CHRONIC LYMPHOCYTIC LEUKEMIA : IN VITRO MODEL Mezzaroba N,1 Mansilla E,2 Zorzet S,1 Calvaruso M,3 Tripodo C,3 Núñez L,4 Tedesco F,1 Nabergoj M,6 Sblattero D,5 Granzotto M,7 Pozzato G,6 Macor P1 1 Department of Life Science, University of Trieste, Italy; 2 CUCAIBA, Ministry of Health, La Plata, Buenos Aires, Argentina; 3 Department of Human Pathology, University of Palermo, Italy; 4 University of Chicago, Chicago, USA and BioTarget, Chicago, USA; 5 Department of Medical Sciences, University of Eastern Piedmont, Novara, Italy; 6 Department of Medical and Surgical Sciences, University of Trieste; 7 Department of Molecular and Laboratory Medicine, IRCCSS Burlo Garofolo, Trieste, Italy Introduction. The actual challenge of tumor therapy is to design new therapeutic agents able to maximize the efficacy minimizing the adverse effects. Nanoparticles (NP) have emerged as important tools to modify the release profile for a large number of drugs. The aim of this study was to determine whether anti-CD20-coated biocompatible FDA-approved NP loaded with Chlorambucil (CLB) and Hydroxychloroquine (HCQ) could induce apoptosis of the B-Chronic Lymphocytic Leukemia (CLL) cell line MEC-1, as well as of circulating neoplastic B-cells isolated from patients with B-CLL. Methods. Nanoparticles were prepared by the copolymerization of polylactic acid and polycaprolactone and had an diameter of 250 nm. The NP with HCQ and CLB were prepared by encapsulation of the two drugs at concentrations of 165 µg per mg of polymer inside their core, and then modified by anti-CD20 adsorption. The NP were resuspended in PBS with 10% Bovine Serum Albumin (BSA) and maintained at 4°C before use. To investigate the ability of NP to affect cell viability and induce cellular apoptosis, MEC-1 cells (2 x 105) were incubated with anti-CD20 coated and CLB-HCQ loaded NP for 48 hours and the residual viable cells was determined with MTT assay. Cell death program activation was also evaluated by analyzing PARP-1 cleavage and Annexin V detection. Monoclonal B-cells were obtained from 44 patients affected by CLL. In each case the IGHV gene mutational status was assessed using standard methods and CD38 and ZAP-70 expressions were determined by flow cytometry. Interphase FISH was performed on nuclei preparations of PBMC and each case was investigated for 13q deletion, 11q deletion, 17p deletion or presence of trisomy 12. Results. Anti-CD20 NP with HCQ and CLB were able to induce a strong reduction (95%) in cell viability of MEC-1 cells. The cytotoxicity was present in a dose-dependent manner and was apoptosis-dependent as confirmed by the PARP- 1 activation and by the binding of Annexin V on cell surface. The same high cytotoxicity rate (>90%) was found also in patient-derived B-cells. The killing rate was independent from IGVH mutational status or from ZAP70 and CD38 expression or from the presence of 17p deletion. An efficient cytotoxicity was present even in CLL B-lymphocytes expressing low CD20 antigen levels on cell surface. The effects of NP were also tested on CD20-negative human and animal cells (CHO, HUVEC, MEL- 28, LoVo cell lines) and no specific cytotoxicity was obtained. On the contrary, incubation of CD20-negative cells with free HCQ + CLB induced cell killing between 58 and 71%. Conclusions. These results indicate that anti-CD20 coated and CLB-HCQ loaded NP show a high toxicity rate in CLL cell line as well as in B-cell obtained from CLL patients. The toxic effect is present also in 17p deleted cases, usually resistant to chemo-immuno-therapy. These results should be confirmed in animal models in order to introduce this promising technology into human clinical trials