Innovative therapies targeting tumor-microenvironment crosstalk in indolent B-cell non-Hodgkin lymphomas

Abstract

[eng] Follicular Lymphoma (FL) and Chronic Lymphocytic Leukemia (CLL) share several features in common: 1) they are indolent B-cell neoplasms, 2) patients usually relapse after treatment, 3) both pathologies as yet remain incurable. The initial driving event in both malignancies is the early acquisition of genetic alterations; however, the proliferative drive for malignant cells is largely dependent on external signals from the tumor microenvironment, which favor the survival of malignant cells. For this reason, the main aim of this thesis was to explore new therapies targeting the interactions between the tumor cell and its microenvironment in FL and CLL. For the work in FL, we chose to use the Follicular Dendritic Cell (FDC) line HK, isolated from human tonsils. The results obtained indicate that the microenvironment in FL, and more specifically FDCs, can profoundly modify the FL transcriptome by activating different pathways among that: angiogenesis, migration, adhesion and serum-like responses. Then, it was demonstrated that the PI3K pathway is a common signaling mediator of the identified pathways and may constitute a good target for therapy in this setting. The results obtained demonstrated that PI3K inhibition by buparlisib significantly reduced FDC- induced expression and secretion of proangiogenic factors in FL cells and also reduced vasculature formation in vivo. Moreover, it was demonstrated that buparlisib hampers FDC-derived serum-like responses and survival signaling. It was also uncovered that FDCs increase the motility properties of FL cells and consequently lymphoma dissemination, by two complementary mechanisms: first, by increasing the expression of adhesion molecules, which favor the adhesion of FL cells to the extracellular matrix (ECM), and second, by secreting chemotactic molecules such as CXCL12. Buparlisib also shows inhibitory activity in this scenario; on the one hand, it reduces FL adhesion to ECM, and reduces CXCL12 secretion and induced migration and signaling. Moreover, buparlisib shows in vivo activity in subcutaneous and systemic mouse models. In summary, this work demonstrates that FDCs contribute to FL lymphomagenesis trough the modulation of a plethora of events leading to lymphoma growth and dissemination, and how the inhibition of PI3K/AKT axis could interfere with this crosstalk and constitute a valuable therapeutic tool. For the work in CLL we chose to work with daratumumab, an anti-CD38 monoclonal antibody CD38 expression is dynamic and regulated by the tumor microenvironment, and is considered a negative prognostic marker for CLL. The results obtained with daratumumab show that it induces lysis of CLL cells mainly via Antibody-Dependent Cellular Cytotoxicity (ADCC) and Antibody-Dependent Cellular Phagocytosis (ADCP) in the presence of external effectors both in vitro and in vivo. However, daratumumab is not able to engage significant Complement-Dependent Cytotoxicity (CDC) on CLL cells. Daratumumab activity may extend beyond its effect on the tumor cells, as we have demonstrated its potential to counteract microenvironment-derived signaling in protective cancer niches, such as lymph nodes and bone marrow. In this context, daratumumab interferes with in vitro cell migration and in vivo homing of CLL cells to spleen in NSG mice. Moreover, daratumumab interferes with transendothelial migration and organ invasion of malignant cells by significantly reducing CD49d/CD29-mediated adhesion to VCAM-1, indicating that daratumumab treatment may impede CLL tissue infiltration that leads to progressive disease. Daratumumab also demonstrated impressive in vivo activity in a CLL systemic mouse model, where it prevented tumor progression and significantly improved overall survival. Taken together, daratumumab immunotherapy opens a new horizon as a novel therapeutic approach for CD38+ CLL by not only inducing the classical antibody-mediated cytotoxicity but also by harnessing microenvironment-derived survival signaling and blocking CLL dissemination to secondary lymphoid organs.

[spa] El linfoma folicular (FL) y la leucemia linfática crónica (CLL) son dos neoplasias indolentes de células B que siguen siendo incurables. En los dos tipos tumorales, la progresión de la enfermedad depende de las señales de supervivencia recibidas del microambiente tumoral. El objetivo principal de esta tesis ha sido explorar nuevas terapias terapéuticas dirigidas a las interacciones entre las células tumorales y su microambiente en FL y CLL. Para el trabajo en FL, se optó por utilizar la línea celular HK, que son un tipo de células dendríticas foliculares (FDCs) aisladas de amígdalas humanas. Los resultados obtenidos indican que el microambiente en FL, y más concretamente las FDCs, puede modificar profundamente el transcriptoma del FL mediante la activación de diferentes vías, entre ellas: la angiogénesis, la migración, la adhesión y la respuesta a suero de las células. Seguidamente, se demostró que la vía de PI3K es un denominador común de las diferentes vías identificadas, constituyendo una buena diana terapéutica para interferir en la interacción del FL con su microambiente. Los resultados obtenidos demostraron que la inhibición de PI3K por buparlisib (pan-inhibidor de PI3K) reduce significativamente la activación de estas vías, después del contacto con el microambiente, en células de FL tanto in vitro como in vivo. Para el trabajo en CLL se optó por trabajar con daratumumab, el primer anticuerpo monoclonal humano anti-CD38. La expresión de CD38 es dinámica en la CLL y está regulada por el microambiente tumoral, considerándose un marcador de mal pronóstico. Los resultados obtenidos con daratumumab muestran que induce lisis celular de las CLL principalmente mediante ADCC y ADCP en presencia de efectores externos, tanto in vitro como in vivo. La actividad de daratumumab va más allá de su efecto directo sobre las células tumorales, demostrando su potencial para contrarrestar la interacción de las células de CLL con el microambiente y las señales protectoras derivadas de éste, interferiendo en procesos de migración, adhesión e invasión celular, indicando que el tratamiento con daratumumab puede impedir la infiltración de las células de CLL en los tejidos, impidiendo así la diseminación de la enfermedad.