Protein kinase D-dependent CXCR4 down-regulation upon BCR triggering is linked to lymphadenopathy in chronic lymphocytic leukaemia

// Stephane Saint-Georges 1,2 , Maude Quettier 1,2 , Marouane Bouyaba 3 , Stephanie Le Coquil 1,2 , Vanessa Lauriente 1,2 , Lionel Guittat 1,2 , Vincent Levy 3 , Florence Ajchenbaum-Cymbalista 1,2,4 , Nadine Varin-Blank 1,2 , Christine Le Roy 1,2,* and Dominique Ledoux 1,2,* 1 INSERM U978, Bobigny, France 2 Universite Paris 13, Sorbonne Paris Cite, Labex “Inflamex”, Bobigny, France 3 Assistance Publique-Hopitaux de Paris, Hopital Avicenne, Unite de Recherche Clinique, Bobigny, France 4 Assistance Publique-Hopitaux de Paris, Hopital Avicenne, Service d’Hematologie Biologique, Bobigny, France * These authors are co-senior authors Correspondence to: Christine Le Roy, email: // Nadine Varin-Blank, email: // Keywords : CLL, lymphadenopathy, B-cell receptor, CXCR4/CXCR5, protein kinase D Received : December 23, 2015 Accepted : April 16, 2016 Published : April 26, 2016 Abstract In Chronic Lymphocytic Leukemia (CLL), infiltration of lymph nodes by leukemic cells is observed in patients with progressive disease and adverse outcome. We have previously demonstrated that B-cell receptor (BCR) engagement resulted in CXCR4 down-regulation in CLL cells, correlating with a shorter progression-free survival in patients. In this study, we show a simultaneous down-regulation of CXCR4, CXCR5 and CD62L upon BCR triggering. While concomitant CXCR4 and CXCR5 down-regulation involves PKDs, CD62L release relies on PKC activation. BCR engagement induces PI3K-δ-dependent phosphorylation of PKD2 and 3, which in turn phosphorylate CXCR4 Ser 324/325 . Moreover, upon BCR triggering, PKD phosphorylation levels correlate with the extent of membrane CXCR4 decrease. Inhibition of PKD activity restores membrane expression of CXCR4 and migration towards CXCL12 in BCR-responsive cells in vitro . In terms of pathophysiology, BCR-dependent CXCR4 down-regulation is observed in leukemic cells from patients with enlarged lymph nodes, irrespective of their IGHV mutational status. Taken together, our results demonstrate that PKD-mediated CXCR4 internalization induced by BCR engagement in B-CLL is associated with lymph node enlargement and suggest PKD as a potential druggable target for CLL therapeutics.