pi103 and Leukemia--Lymphocytic--Chronic--B-Cell

CLL cell survival and proliferation is enhanced through direct contact with supporting cells present in lymphoid tissues. PI3Ks are critical signal transduction enzymes controlling B cell survival and activation. PI3K inhibitors have entered clinical trials and show promising therapeutic activity; however, it is unclear whether PI3K inhibitor drugs differentially affect ZAP-70 positive versus negative CLL cells or target specific microenvironmental interactions. Here we provide evidence that CD40L+IL-4, IL-8 or IL-6 enhance adhesion to stromal cells, with IL-6 showing a selective effect on ZAP-70 positive cells. Stimulatory effects of IL-8 or IL-6 are fully reversed by PI3K inhibition, while the effects of CD40L+IL-4 are partially reversed. While CD40L+IL-4 is the only stimulation increasing CLL cell survival for all patient groups, IL-6 protects ZAP-70 positive cells from cell death induced by PI3K inhibition. Altogether, our results indicate that targeting the PI3K pathway can reverse protective CLL-microenvironment interactions in both ZAP-70 positive and negative CLL despite their differences in cytokine responsiveness.

Topics: Animals; CD40 Ligand; Cell Adhesion; Cell Survival; Coculture Techniques; Cytokines; Flow Cytometry; Furans; Humans; Interleukin-4; Interleukin-6; Interleukin-8; Leukemia, Lymphocytic, Chronic, B-Cell; Mice; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Pyridines; Pyrimidines; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Stromal Cells; Tumor Cells, Cultured; Tumor Microenvironment; ZAP-70 Protein-Tyrosine Kinase

Phosphoinositide 3-kinases (PI3Ks) are among the most frequently activated signaling pathways in cancer. In chronic lymphocytic leukemia (CLL), signals from the microenvironment are critical for expansion of the malignant B cells, and cause constitutive activation of PI3Ks. CXCR4 is a key receptor for CLL cell migration and adhesion to marrow stromal cells (MSCs). Because of the importance of CXCR4 and PI3Ks for CLL-microenvironment cross-talk, we investigated the activity of novel, isoform-selective PI3K inhibitors that target different isoforms of the p110-kDa subunit. Inhibition with p110alpha inhibitors (PIK-90 and PI-103) resulted in a significant reduction of chemotaxis and actin polymerization to CXCL12 and reduced migration beneath MSC (pseudoemperipolesis). Western blot and reverse phase protein array analyses consistently demonstrated that PIK-90 and PI-103 inhibited phosphorylation of Akt and S6, whereas p110delta or p110beta/p110delta inhibitors were less effective. In suspension and MSC cocultures, PI-103 and PIK-90 were potent inducers of CLL cell apoptosis. Moreover, these p110alpha inhibitors enhanced the cytotoxicity of fludarabine and reversed the protective effect of MSC on fludarabine-induced apoptosis. Collectively, our data demonstrate that p110alpha inhibitors antagonize stromal cell-derived migration, survival, and drug-resistance signals and therefore provide a rational to explore the therapeutic activity of these promising agents in CLL.

Topics: 1-Phosphatidylinositol 4-Kinase; Actin Cytoskeleton; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Chemokine CXCL12; Chemotaxis, Leukocyte; Chromones; Drug Evaluation, Preclinical; Drug Resistance, Neoplasm; Enzyme Inhibitors; Furans; Humans; Isoenzymes; Leukemia, Lymphocytic, Chronic, B-Cell; Morpholines; Pharmaceutical Preparations; Pyridines; Pyrimidines; Receptors, CXCR4; Signal Transduction; Stromal Cells; Substrate Specificity; Tumor Cells, Cultured