Recently it has been shown that both primary tumors and surrounding microenvironment are mmunosuppressive to the innate immune system thereby preventing effective function in direct and antibody mediated tumor cell killing. Immunesuppression is particularly present in primary CLL where the primary tumor cells have production of TGF-B, IL-10, lL-6, and PDL1 along with expanded T-regulatory cells which antagonize immune surveillance and effective antibody dependent cellular cytotoxicity (ADCC) and antibody dependent cellular phaogocytosis (ADCP). Of interest, immune suppression promoted by CLL tumor cells is mediated in part through constitutive activation of B-cell receptor (BCR) signaling. This project is directed to reverse the immunosuppressive tumor and immune cell function through interventions using novel kinase inhibitors targeting two B-cell receptor (BCR) kinases: delta isoform specific PI3-kinase (CAL-101) and Bruton's tyrosine kinase (BTK) (PCI 32765). We will pursue both preclinical in vitro and in vivo studies of these compounds in the context of CLL and assess their effects on both monocyte/macrophage function (with Project Z) and NK cell function (with Project 3). Given that CAL-101 and PCI 32765 reverse tumor cell immunosuppressive properties and are very active therapeutic agents for CLL, we will pursue how to best integrate these two agents monoclonal antibodies directed at CD20 and potentially other targets through pre-clinical mouse in vivo studies and early phase l/ll human clinical trials where CAL-101 and PCI32765 are given as single agents followed by detailed ex-vivo assessment of innate immune function. In addition, we have discovered that IL-21, a novel common-y chain family of cytokine, lacks properties to promote tolerance induced by regulatory T-cell expansion, activates NK-cells with enhanced anti-CD20 ADCC, promotes direct CLL cell apoptosis, and also directly enhances CD20 mediated apoptosis. We have tested our initial hypotheses of IL-21's ability to enhance innate immune cell function through a phase I study of the anti-CD20 rituximab mAb in combination with IL-21 where durable remissions have been observed in CLL. We will attempt to expand the effectiveness of IL-21 through mechanistic studies with the immunomodulating agent lenalidomide which we have demonstrated to upregulate the IL-21 R on CLL cells, promotes IL-21 production by T-cells, directly enhances NK killing and increases NK-cell ADCC with antibodies directed at B-cell targets. This work builds on the overall hypothesis that combination approaches which 1) enhance innate immune function, 2) diminish tumor cell mediated immune suppression, and 3) induce apoptosis in primary CLL will have significant clinical activity. A clinical trial of IL-21, lenalidomide and anti-CD20 therapy will follow our mechanistic preclinical studies.
This work builds on the overall hypothesis that combination approaches which 1) enhance innate immune function , 2) diminish tumor cell mediated immune suppression, and 3) induce apoptosis in primary CLL will have significant clinical activity. At completion of this project we will have advanced a new paradigm for treating CLL without chemotherapy that incorporates: 1) novel B-cell receptor kinase inhibitors to antagonize tumor-cell mediated immune suppression and/or 2) immune modulating agents which also enhance tumor killing to improve the therapeutic effectiveness of anti-CD20 monoclonal antibody therapy.
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