ZAP-70 enhances migration of malignant B lymphocytes towards CCL21 by inducing CCR7 expression via IgM-ERK1/2 activation

ZAP-70 in chronic lymphocytic leukemia (CLL) has been associated with enhanced Bcell receptor (BCR) signaling, survival and migration. We investigated whether ZAP-70 can directly govern migration and the underlying mechanisms. In the ZAP-70 stablytransfected Ramos cell line, IgM stimulation but no IgD enhanced phosphorylation of ERK1/2, Akt and Syk, and delayed IgM and CD79b internalization. In contrast, in the Raji cell line, where ZAP-70 was constitutively phosphorylated, ERK1/2 but not Akt was phosphorylated, suggesting that MAPK pathway mediates ZAP-70 effects. BCR stimulation modulated the expression of CCR7, CXCR4, CXCR5, CD44, CD49d and CD62L, which were upregulated in ZAP-70-positive CLL primary subclones. The most dramatic change after BCR engagement in ZAP-70-transfected cells was CCR7 upregulation, this being impaired by ERK1/2 inhibition and translating into both increased signaling and migration towards CCL21. Primary CLL subclones with high ZAP-70 expression showed increased migration towards CCL21. In conclusion, ZAP70 ectopic expression led to enhanced BCR signaling after IgM stimulation and increased the expression of CCR7 predominantly via ERK1/2, increasing the response and migration towards CCL21. In primary CLL samples, cellular subsets with high ZAP70 expression had increased expression of adhesion molecules and chemokine receptors in addition to an enhanced ability to migrate towards CCL21. For personal use only. on April 1, 2017. by guest www.bloodjournal.org From