Effects of chlorambucil/hydroxychloroquine-loaded anti-CD20 nanoparticles on a human/mouse model of Burkitt lymphoma

EFFECTS OF CHLORAMBUCIL/HYDROXYCHLOROQUINE-LOADED ANTI-CD20 NANOPARTICLES ON A HUMAN/MOUSE MODEL OF BURKITT LYMPHOMA Mezzaroba N,1 Mansilla E,2 Zorzet S,1 Larsen G,3 Tripodo C,4 Núñez L,5 Marín GH,2 Nabergoj M,6 Tedesco F,1 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 LNK Chemsolutions, Lincoln Nebraska, USA and Bio-Target, Chicago, USA; 4 Department of Human Pathology, University of Palermo, Italy; 5 University of Chicago, Chicago, USA and BioTarget, Chicago, USA; 6 Department of Medical and Surgical Sciences, University of Trieste, Italy Introduction. In Burkitt lymphoma (BL) chemotherapy shows variable responses since a fraction of younger patients are resistant or relapse and the patients over 40 have difficulties to follow the therapy. In nonresponders/relapsers BL cells often express low level of CD20 and/or mutant/deleted p53. To overcome these problems, we developed a new therapeutic approach in which the efficacy of chemotherapy is associated to the specificity and low side-effects of antibody-based therapy. This approach lies in biodegradable nanoparticles (NP) coated with an antibody to target the neoplastic cells and filled with Hydroxychloroquine (HCQ) (a p53-independent toxic substance) and chlorambucil (CLB) as modern “Trojan Horses” to destroy the cancer cells. Methods. NP were prepared by the copolymerization of polylactic acid and polycaprolactone (diameter:250nm). The NP with HCQ and CLB were prepared by encapsulation at concentrations of 165 μg per mg of polymer inside their core, and then modified by anti-CD20 adsorption. In vitro study: To investigate the ability of NP to kill Burkitt lymphoma cell lines, 5 x 105 BJAB cells were incubated for 48 hours and the number of residual viable cells was determined with MTT assay. Apoptosis was evaluated by analyzing PARP-1 cleavage and Annexin V detection. In vivo study: A xenograft model was developed in SCID mice inoculated i.p. with 2 x 106 labeled or unlabeled BJAB cells; a fraction of mice was treated with NP and all animals examined twice weekly up to 120 days. A small-animal time-domain eXplore Optix pre-clinical imager was used for the invivo and ex-vivo evaluation of labeled BJAB cell dissemination and Ritcy5.5 distribution. At 120 days the animals were sacrificed and peritoneal mass and organs, lymph nodes and bones were collected for immunohistochemical analysis. Results. In vitro study: The binding NP on cell surface and their internalization were documented with confocal microscopy. In BJAB cells, HCQ and CLM as free substances induced cell death in 82% and 38% respectively, while NP containing only 5,4 g of HCQ and CLB killed 100% of cells. This effect is due to the synergic proapoptotic effect as shown by Annexin V detection and by PARP activation. The effects of NP was tested on CD20-negative cell lines CHO, HUVEC, MEL-28, LoVo: No cell cytotoxicity was detectable using NP, whereas free HCQ+CLB induce cell killing between 58 and 71%. In vivo study: The intra-peritoneal injection of BJAB cells induced a fast (within 4 days) tumor cells spread in different organs and, without therapy, all animals died in 50-70 days as well as those receiving free HCQ and CLM. Conversely, survival at 120 days of the mice receiving 4 or 8 i.p. injections of NP was 50 and 90% respectively. Conclusions. These results indicate that NP are able to cure even the highly proliferating BL cell line BJAB in both in vitro and in vivo models. This suggests the introduction of this promising technology into human clinical trial.