Study of the Metabolism in the Lymphatic Niche of CLL

Chronic lymphoid leukemia (CLL) is the most common adult leukemia that is characterized by a malignant monoclonal accumulation of tumoral and quiescent B cells in the peripheral blood. In advanced stages of the disease (Binet stage C), this population invades the bone marrow (BM) and proliferate into the lymphoid organs that results in widespread adenopathy. Richter's transformation is a most aggressive serious complication of CLL (transformation of the disease into an aggressive lymphoma) detected based on TEP/CT (Positron Emission Tomography/ computerized tomography) that shows highly derived glucose consumption by cancer cells. Clinical data from CLL patients with disease acutisation showed hypermetabolic lymphadenopathy with high standardized uptake value (SUV) whereas there is low grade tracer uptake into BM. We supposed that the tumor microenvironment of the lymphatic niche promotes the proliferation and glycolytic activity of CLL cells which become particularly resistant to treatment. The development of an ex-vivo tumor model that reproduces the microenvironment of the lymph node niche appears essential to identify and validate new therapeutic targets because despite the therapeutic arsenal available some patients still relapse or are refractory to treatment. Our objectives are to i / Characterize this niche of resistance by the development of an ex-vivo tumor model and ii / Evaluate in-vitro the effectiveness of the association of current treatments (RFC, Ibrutinib or Venetoclax) with anti-metabolic therapies (inhibitors of glycolysis) Our lab is developing an ex-vivo models of the lymphatic niche in CLL based on co-cultures of leukemic cells from patients stimulated with CpG ODN and IL2 with primary human lymphatic fibroblasts (HLF) (EC 12PP15). This co-culture has never been described in the literature and allows us to study the lymphatic niche of CLL patients. Lymph node (LN) exploration in CLL requires invasive access and does not bring any additional information in initial diagnosis. Then, we validated our co-culture model using complementary approaches: increased viability, proliferation, and resistance to Ibrutinib, associated with increased production of anti-apoptotic proteins such as MCL1 and BCL2 after 48 hours of co-culture. Secondly, we studied the metabolism in this resistance niche. We find an increased production of lactate and an acute consumption of glucose, associated with a strong metabolic activation detected by SEAHORSE and by the production of glycolysis enzymes such as hexokinase 2. Our study constitutes an original project because it characterized the energy metabolism of the CLL lymphatic niche by developing an original ex-vivo model and enhanced our understanding of the contribution of the specific microenvironment in the dissociation of metabolic activity using SUV max in BM and lymphatic niche. Anti-metabolic therapies are efficient on co-culture CLL cells and could be an alternative for refractory or relapsed patients under current treatment.