Multicellular Aggregates Of Lymphoma Cells (MALC): An Invaluable Model For Studying Follicular Lymphoma Biology and Mechanisms Of Action Of Therapeutic Drugs Such As Anti-CD20 Antibodies

Follicular lymphoma (FL) is the second most common type of B non-Hodgkin’s lymphomas (NHL) and makes up 40% of all adult lymphomas. Like most carcinomas, NHL grow as spherical tumors. Based on carcinoma 3D models (often described as spheroids) it is acknowledged that spatial organization may profoundly affect tumor cell behavior since important functions are dictated by the collective properties of a cell population rather than those of a single cell. These include growth, metastasis, cell-to-matrix and cell-to-cell interaction, as well as intracellular signaling and resistance to anti-tumor agents or even immune escape. Spatial organization can exert these effects in cancer cells by affecting gene expression profiles or influencing major signaling pathways such as those driven by MAPK, Akt and oncogenic products such as HER-2. More importantly, spatial organization is known to influence the response to antibodies such as Trastuzumab or Pertuzumab.

Conventional 2D NHL cell culture models do not reflect the true effects of antibodies as they occur in vivo and may be of limited use. Thus, we recently created a NHL 3D culture system, the so-called Multicellular Aggregates of Lymphoma Cells (MALC) model, using a modification of the “hanging drop” method. This model is not only useful for studying FL biology, but also for evaluating tumor sensitivity to antibodies since diffusion/distribution is different within a solid 3D tumor.

In this study, we present transcriptomic and extracellular matrix proteins expression profiles in 2D, 3D FL cell cultures and patients biopsies, and observed that MALC, but not 2D cultures, display similarities to patients samples. Indeed, we observe an upregulation of genes involved in the response to hypoxia, activation of NFκB pathway and negative regulation of cell cycle promoting the emergence of chemoresistant quiescent cells. Moreover, MALC, in contrast to 2D cultures but as observed in biopsies, exhibit higher expression of fibronectin, laminin, vitronectin and collagen. Recently, we showed that spatial organization also influence response to anti-CD20 monoclonal antibodies such as Rituximab and Obinutuzumab. Here, we investigate the antibody-dependant cell cytotoxicity induced by these two monoclonal anti-CD20 antibodies in the MALC model: cell cytotoxicity, effector and target cells signaling, and spatial localization are presented.

Thus, we present an invaluable model for further investigation of FL biology, and also for the development/screening of new genotoxic drugs and therapeutic monoclonal antibodies in lymphoma.