Spinning leukaemic cells to study their drug resistance

Chronic lymphocytic leukaemia (CLL) is the most common type of leukaemia in adults and still lacks a cure, despite the rapid development of therapeutic approaches over the past few decades. CLL is characterised by the progressive proliferation of CD5+ B cells (which usually occurs in proliferation centres in lymph nodes), followed by their recirculation into the peripheral blood and accumulation in the bone marrow and secondary lymphoid organs. The efficacy of CLL therapies is often reduced by the supportive environment in the bone marrow and lymph nodes, through interactions between CLL cells and surrounding tissues, although the exact underlying mechanism is not fully understood.To address this knowledge gap and provide a platform for investigating CLL resistance mechanisms, Daniela Belloni, Dafne Barozzi, Paolo Ghia, Cristina Scielzo and their colleagues developed a 3D lymph node surrogate model using a rotary cell-culture bioreactor. The authors note that traditional 2D cultures do not capture the spatial organisation or signalling complexity of tissue microenvironments, and murine models often fail to recapitulate key aspects of human-specific CLL biology. Therefore, 3D culture systems can be a powerful alternative that more accurately represents the human-specific tissue microenvironment and, consequently, allows observation of human-specific in vivo drug responses. To improve existing 3D lymph node CLL models, the authors used a gelatine-based matrix incorporating stromal and endothelial cells lacking in current systems. This combination promoted CLL cell survival, proliferation and matrix deposition, including components of the lymph node niche (such as hyaluronic acid, collagen IV and fibronectin) that are essential for accommodating key immune populations (such as CD4+ and CD8+ T cells, and macrophages). The dynamic bioreactor setup enabled the recreation of lymph node–peripheral blood differences, with CLL cells within the scaffold expressing lower levels of CXCR4 than those remaining in suspension outside the scaffold. To demonstrate the preclinical value of this model, the authors evaluated the effects of two first-line chemotherapy drugs for CLL, venetoclax and ibrutinib. The results were close to those observed in patients: CLL cells showed greater resistance to venetoclax in the lymph node microenvironment than in the bone marrow, which could not be accounted for solely by T-cell content, suggesting that other mechanisms are involved.Overall, the authors developed a model that provides a physiologically relevant platform for studying CLL biology, the interplay between CLL cells and their niche, tissue-specific drug responses, and, in particular, microenvironment-mediated drug resistance.