Interactions between stromal and tumor cells in the microenvironment play a key role in B-cell chronic lymphocytic leukemia (B-CLL) onset and progression. This complex cross-talk is based on cytokine release and intercellular contacts that contribute to regulate the mechanisms of cell survival and apoptosis. Among the cytokines involved in this network, CXCL8/IL-8 is particularly noteworthy as potential pro-survival molecule able to decrease spontaneous apoptosis as well as chlorambucil or fludarabine-mediated cytoxicity in B-CLL cells. In this study, we explored whether the CXCL12 chemokine of stromal origin can regulate the expression of CXCL8 in B-CLL cells. We analyzed primary peripheral blood B-cells from 15 B-CLL patients. Engagement of CXCR4 expressed by B-CLL with exogenous CXCL12 induced a significant increased production of CXCL8 in 10/15 B-CLL cases (average fold-induction ± SD = 2.3 ± 0.9, range 1.5 - 4.5), but was ineffective on IL-1, TNF, or IL-10 production, as simultaneously measured by cytometric bead array kit and flow cytometry analysis. Real time PCR analysis confirmed the CXCL8 increased expression also at the level of mRNA. In contrast, the stromal CXCL13 chemokine used as control did not affect CXCL8 expression in B-CLL. We then investigated the role of the p38 mitogen activated protein kinases (MAPK) pathway, which can contribute to regulate CXCL8 production in some cells. To this aim, we used SB203580, a pyridinyl imidazole drug compound that specifically binds to p38 MAPK and reversibly blocks its enzymatic activity. Inhibition of p38 MAPK by SB203580 suppressed both constitutive and inducible CXCL8 production, thus suggesting that the p38 pathway is required for CXCL8 expression in B-CLL. In contrast, worthmannin, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K), had no effect on CXCL8 production. Our data show that CXCL8 is physiologically regulated by the CXCL12/CXCR4 axis and suggest that the p38 pathway is required for CXCL8 expression. Since CXCL8 has been implicated in progression of B-CLL disease, our findings suggest that, by up-regulating CXCL8, the CXCL12/CXCR4 axis may contribute to the pathogenesis of B-CLL.

CXCL8/interleukin 8 in B-cell chronic lymphocytic leukemia is up-regulated through the activity of the CXCL12/CXCR4 axis

SCUPOLI, Maria;PERBELLINI, Omar;LOVATO, Ornella;ZANOTTI, ROBERTA;MALPELI, Giorgio;AMBROSETTI, Achille;SCARPA, Aldo;PIZZOLO, Giovanni
2007

Abstract

Interactions between stromal and tumor cells in the microenvironment play a key role in B-cell chronic lymphocytic leukemia (B-CLL) onset and progression. This complex cross-talk is based on cytokine release and intercellular contacts that contribute to regulate the mechanisms of cell survival and apoptosis. Among the cytokines involved in this network, CXCL8/IL-8 is particularly noteworthy as potential pro-survival molecule able to decrease spontaneous apoptosis as well as chlorambucil or fludarabine-mediated cytoxicity in B-CLL cells. In this study, we explored whether the CXCL12 chemokine of stromal origin can regulate the expression of CXCL8 in B-CLL cells. We analyzed primary peripheral blood B-cells from 15 B-CLL patients. Engagement of CXCR4 expressed by B-CLL with exogenous CXCL12 induced a significant increased production of CXCL8 in 10/15 B-CLL cases (average fold-induction ± SD = 2.3 ± 0.9, range 1.5 - 4.5), but was ineffective on IL-1, TNF, or IL-10 production, as simultaneously measured by cytometric bead array kit and flow cytometry analysis. Real time PCR analysis confirmed the CXCL8 increased expression also at the level of mRNA. In contrast, the stromal CXCL13 chemokine used as control did not affect CXCL8 expression in B-CLL. We then investigated the role of the p38 mitogen activated protein kinases (MAPK) pathway, which can contribute to regulate CXCL8 production in some cells. To this aim, we used SB203580, a pyridinyl imidazole drug compound that specifically binds to p38 MAPK and reversibly blocks its enzymatic activity. Inhibition of p38 MAPK by SB203580 suppressed both constitutive and inducible CXCL8 production, thus suggesting that the p38 pathway is required for CXCL8 expression in B-CLL. In contrast, worthmannin, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K), had no effect on CXCL8 production. Our data show that CXCL8 is physiologically regulated by the CXCL12/CXCR4 axis and suggest that the p38 pathway is required for CXCL8 expression. Since CXCL8 has been implicated in progression of B-CLL disease, our findings suggest that, by up-regulating CXCL8, the CXCL12/CXCR4 axis may contribute to the pathogenesis of B-CLL.
B CELL CHRONIC LYMPHOCYTIC LEUKEMIA; cytokines; Tumor Microenvironment
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11562/627258
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