Resumen de Development of diffuse large B-celllymphoma mouse models and role of CXCR4 in dissemination = Desarrollo de modelos murinos de linfoma difuso de células grandes B y papel de CXCR4 en diseminación
Diffuse large B-cell lymphoma (DLBCL) is a clinically and genetically heterogeneous disease, accounting for 30% of all non-Hodgkin lymphoma cases. Although the addition of rituximab to standard treatment (CHOP: cyclophosphamide, doxorubicin, vincristine, and prednisone) has increased survival of DLBCL patients, 30-40% of patients still relapse. Moreover, 1-10% of the relapsed patients show central nervous system (CNS) involvement which is almost always a fatal condition. Consequently, further studies are needed to understand the molecular mechanisms involved in the disease and to develop novel therapies to improve the patients¿ outcome. In this regard, modeling the disease in mice has reached a great relevance and it is necessary to develop novel models that represent the clinical features of the disseminated disease. In addition, novel biomarkers are needed to predict DLBCL outcome. Accumulating data have emerged about the correlation of CXCR4 receptor with disease dissemination and aggressiveness in several neoplasms. This receptor has also been described to play a role in the migration and trafficking of B cells and some hematological malignancies. However, no data are available about its involvement in DLBCL dissemination or its relevance as a prognostic marker in this disease. The goals of the current thesis were: 1) To develop bioluminescent mouse models of disseminated DLBCL which reflect this human pathology. 2) To evaluate the in vivo antitumor effect of a new inhibitor of focal adhesion signaling, E7123, in a model of DLBCL with central nervous system (CNS) involvement. And, 3) To study the role of CXCR4 receptor in the migration and dissemination of DLBCL cells and evaluated the expression of the receptor in lymph node biopsies of DLBCL patients and its prognostic value. We have developed bioluminescent xenograft models of disseminated DLBCL that derive from DLBCL cell lines and that reflect this human pathology. These models can be used to study cell dissemination and the effect of novel antitumor drugs against DLBCL. In fact, the focal adhesion inhibitor E7123 was tested in a disseminated DLBCL model with CNS involvement; this drug delayed the growth of DLBCL metastasis to the CNS and increased mouse survival time. These findings suggest that E7123 was able to cross the blood brain barrier and thus could be effective for the treatment of DLBCL patients with CNS involvement. However, further preclinical development and clinical assays will be necessary to evaluate E7123 antitumor effect in relapsed DLBCL patients. In addition, we observed that the level of membrane CXCR4 expression in DLBCL cell lines correlated positively with in vitro migration towards SDF-1¿ chemokine and this migration was inhibited by the CXCR4 antagonist, AMD3100. Expression of the receptor was also associated with increased engraftment and dissemination, and decreased survival time in DLBCL NOD/SCID mouse models. Moreover, the subcutaneous preconditioning of DLBCL cells produced changes in the levels of membrane CXCR4 that correlated with aggressiveness of the models; higher levels of CXCR4 led to shortened mouse survival and enhanced lymphoma dissemination. Furthermore, administration of the AMD3100 antagonist to a xenograft DLBCL model decreased dissemination of the tumor cells. Thus, AMD3100 could potentially be used in the treatment of DLBCL. We also evaluated the prognostic value of CXCR4 and found that the receptor is an independent prognostic factor associated with a decreased progression-free survival of patients. These results show that CXCR4 mediates dissemination of DLBCL cells and define for the first time its value as an independent prognostic marker in patients. This novel prognostic marker requires further studies and validation in an independent cohort of DLBCL patients to be used as a potentially clinical tool.
