Lymph node-induced immune tolerance in chronic lymphocytic leukaemia: a role for caveolin-1

Emerging evidence indicates that the tumour microenvironment (TME) regulates the behaviour of chronic lymphocytic leukaemia (CLL). However, the precise mechanism and molecules involved in this process remain unknown. Gene expression profiles of CLL cells from lymph node (LN), bone marrow (BM) and peripheral blood (PB) indicate overexpression of a tolerogenic signature in CLL cells in lymph nodes (LN-CLL). Based on their role in B cell biology, the progression of CLL, or immune regulation, a few genes of this 83-gene signature were selected for further analyses. We observed a significant correlation between the clinical outcomes and the expression of CAV1 (P=0.041), FGFR1 isoform 8 (P=0.032), PTPN6 (P=0.031) and ZWINT (P<0.001). CAV1, a molecule involved in the regulation of tumour progression in other cancers, was seven-fold higher in LN-CLL cells compared to BM- and PB-CLL cells. Knockdown of CAV1 expression in CLL cells resulted in significantly decreased migration (P=0.016) and proliferation (P=0.04). When CAV1 was knocked down in B and T cell lines, we observed an inability to form immune synapses. Furthermore, CAV1 knockdown in CLL cells impaired their ability to form immune synapses with autologous T lymphocytes and allogeneic, healthy T cells. Subsequent analyses of microarray data showed differential expression of cytoskeletal genes, specifically those involved in actin polymerization. Therefore, we report a novel role for CAV1 in tumour-induced immunosuppression during the progression of CLL.