Reprogramming Nurse-like Cells with Interferon γ to Interrupt Chronic Lymphocytic Leukemia Cell Survival

Abstract

Nurse like cells (NLCs) 3 are tumor-nurturing cells derived from CD14 ϩ monocytes in chronic lymphocytic leukemia (CLL) patients. In vitro studies have classified NLCs as CLLspecific, tumor-associated macrophage-like cells functioning as immune regulators and also possible inducers of emerging drug resistance (1-3). It has been shown recently that, in patients with diffuse large B cell lymphoma, a high density of CD68 ϩ /CD163 ϩ tumor-associated macrophages was significantly correlated with unfavorable prognosis and poor clinical outcome (4). Interferons have been widely accepted as modulators of macrophage plasticity and activation, and it is known that IFN␥ is capable of promoting the differentiation of monocytic cells (7). With regard to therapeutic use, Miller et al. (8) have shown that IFN␥ is beneficial for treating immune disorders such as systemic sclerosis and that it displays antitumor and antiangiogenic effects both in vitro and in vivo . IFN␥ treatment has also been shown to induce antineoplastic immune responses by sensitizing tumor cells to apoptosis via up-regulation of both MHC class I and II molecules and by enhancing antitumor immune activity while decreasing M2 characteristics in immune cells (9, 10). IFN␥ has been successfully used in cases of ovarian cancer, multiple myeloma (11), and bladder carcinoma and, recently, in malignant gliomas (12).Here we examined the effects of IFN␥ on the phenotype and function of NLCs. We found that IFN␥ significantly increased the expression of the M1-related markers CD86 and HLA-DR as well as the phagocytic receptor Fc␥RI. Concurrently, the prosurvival ligand CD31 was down-regulated. Consistent with this, IFN␥-treated NLCs showed superior phagocytic ability toward both opsonized sheep RBCs (SRBCs) and rituximab-coated CLL cells as well as withdrawal of support for CLL cell survival. These results show that IFN␥ can reprogram NLCs to function as immune effectors and suggest that therapies that enhance IFN␥ production locally may be valuable treatments for CLL, particularly when combined with monoclonal antibodies such as rituximab. Experimental ProceduresPatient Samples-Peripheral blood was collected from CLL patients with informed consent in accordance with the Declaration of Helsinki and under approval from the Institutional Review Board of Ohio State University.NLC Culture-Peripheral blood mononuclear cells were isolated from CLL patient blood by density gradient centrifugation over Ficoll-Hypaque (Nycomed, Oslo, Norway) and resus-

Chronic lymphocytic leukemia cells are active participants in microenvironmental cross-talk

“…Interestingly, the tumor supportive phenotype in MDC is reversible, as IFN-γ stimulation results in transdifferentiation of pro-tumorigenic (M2) CLL-associated monocytes towards M1 macrophages. 71 Similarly, inhibiting PD1 signals could restore macrophage function, 69 suggesting there is potential for therapeutic intervention in these pathways.…”

CD31 Acts as a Checkpoint Molecule and Is Modulated by FcγR-Mediated Signaling in Monocytes

“…Downregulation of CD31 expression by FcgR signaling initiated by therapeutic Abs may increase FcgR-mediated effector functions against cancer cells while simultaneously impairing cell-survival signals because of reduced interactions with CD38. Indeed, in a recent study, we demonstrated that downregulation of CD31 expression by IFN-g correlated with decreased chronic lymphocytic leukemia cell survival (39).…”

The duality of macrophage function in chronic lymphocytic leukaemia

“…Another implication of targeting TAMs/NLCs is the potential to remove a major immunosuppressive stimulus from the tumour microenvironment. In particular, it has been noted that TAMs possess a PI3Kγ-dependent immune suppressor phenotype which is independent of an additional role in permitting immune checkpoint activity within the tumour microenvironment [19,68]. Recognition of these new roles of M2-like TAMs supports studies focusing on "driving" the macrophage phenotype towards a more "M1" phenotype [69,70] rather than ablating all macrophages [20,30,68].…”

“…In particular, it has been noted that TAMs possess a PI3Kγ-dependent immune suppressor phenotype which is independent of an additional role in permitting immune checkpoint activity within the tumour microenvironment [19,68]. Recognition of these new roles of M2-like TAMs supports studies focusing on "driving" the macrophage phenotype towards a more "M1" phenotype [69,70] rather than ablating all macrophages [20,30,68]. For example, recent studies in models of pancreatic cancer and melanoma have shown that targeted inhibition of PI3Kγ by pharmacological inhibitors or genetic depletion of macrophage PI3Kγ promoted the conversion of M2-like TAMs to an M1-like phenotype [29,52,63].…”