Potential role of serum level of soluble CD44 and IFN-γ in B-cell chronic lymphocytic leukemia

CD44: a cancer stem cell marker and therapeutic target in leukemia treatment

CD44 is a ubiquitous leukocyte adhesion molecule involved in cell-cell interaction, cell adhesion, migration, homing and differentiation. CD44 can mediate the interaction between leukemic stem cells and the surrounding extracellular matrix, thereby inducing a cascade of signaling pathways to regulate their various behaviors. In this review, we focus on the impact of CD44s/CD44v as biomarkers in leukemia development and discuss the current research and prospects for CD44-related interventions in clinical application.

Interferon gamma regulates a complex pro-survival signal network in chronic lymphocytic leukemia

BACKGROUND

It is known that the microenvironmental cytokine interferon gamma (IFN-γ) provides a survival advantage for chronic lymphocytic leukemia (CLL) cells. However, the mechanisms involved in this effect have not been properly investigated.

METHODS

Herein, we conducted a comprehensive screening of the effects of IFN-γ on signaling pathways and gene expression profiles in CLL cells by using western blotting, real-time quantitative reverse transcription (RT-qPCR) and high-throughput RNA sequencing (RNA-seq).

RESULTS

We found that IFN-γ not only activated the pro-survival signal transducer and activator of transcription 3 (STAT3), but also activated the protein kinase B and extracellular signal-regulated kinase signaling pathways. RNA-seq analysis showed that IFN-γ stimulation changed the expression profiles of more than 500 genes, with 391 being up-regulated and 123 down-regulated. These genes are involved in numerous biological processes, including anti-apoptosis, cell migration, and proliferation. IFN-γ significantly up-regulated the expression of CD38, BCL6, CXCL9, BCL2A1, SCOS3, IL-10, HGF, EGFR, THBS-1, FN1, and MUC1, which encode proteins potentially associated with disease progression, worse prognosis or poor response to treatment. Blocking janus kinases1/2 (JAK1/2) or STAT3 signal by specific inhibitors affected the expression of most genes, suggesting a pivotal role of the JAK1/2-STAT3 pathway in IFN-γ pro-survival effects in CLL.

CONCLUSIONS

Our data demonstrate that IFN-γ regulates a complex pro-survival signal network in CLL through JAK1/2-STAT3, which provides a rational explanation for IFN-γ promoting CLL cells survival and drug resistance.

Activation of Interferon Signaling in Chronic Lymphocytic Leukemia Cells Contributes to Apoptosis Resistance via a JAK-Src/STAT3/Mcl-1 Signaling Pathway

Besides their antiviral and immunomodulatory functions, type I (α/β) and II (γ) interferons (IFNs) exhibit either beneficial or detrimental effects on tumor progression. Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of abnormal CD5⁺ B lymphocytes that escape death. Drug resistance and disease relapse still occur in CLL. The triggering of IFN receptors is believed to be involved in the survival of CLL cells, but the underlying molecular mechanisms are not yet characterized. We show here that both type I and II IFNs promote the survival of primary CLL cells by counteracting the mitochondrial (intrinsic) apoptosis pathway. The survival process was associated with the upregulation of signal transducer and activator of transcription-3 (STAT3) and its target anti-apoptotic Mcl-1. Furthermore, the blockade of the STAT3/Mcl-1 pathway by pharmacological inhibitors against STAT3, TYK2 (for type I IFN) or JAK2 (for type II IFN) markedly reduced IFN-mediated CLL cell survival. Similarly, the selective Src family kinase inhibitor PP2 notably blocked IFN-mediated CLL cell survival by downregulating the protein levels of STAT3 and Mcl-1. Our work reveals a novel mechanism of resistance to apoptosis promoted by IFNs in CLL cells, whereby JAKs (TYK2, JAK2) and Src kinases activate in concert a STAT3/Mcl-1 signaling pathway. In view of current clinical developments of potent STAT3 and Mcl-1 inhibitors, a combination of conventional treatments with these inhibitors might thus constitute a new therapeutic strategy in CLL.

Breast Cancer Cell-Derived Soluble CD44 Promotes Tumor Progression by Triggering Macrophage IL1β Production

IL1β is a central regulator of systemic inflammatory response in breast cancer, but the precise regulatory mechanisms that dictate the overproduction of IL1β are largely unsolved. Here, we show that IL1β secretion is increased by the coculture of human monocyte-like cells and triple-negative breast cancer (TNBC) cells. In addition, macrophages robustly produced IL1β when exposed to the conditioned media of TNBC cells. Consistent with these observations, macrophage depletion decreased serum IL1β and reduced breast cancer progression in an orthotopic breast cancer mouse model. Profiling the secretome of human breast cancer cells revealed that the CD44 antigen was the most differentially released protein in basal conditions of TNBC cells. Antibody-mediated neutralization of CD44 abrogated IL1β production in macrophages and inhibited the growth of primary tumors. These results suggest IL1β-mediated oncogenic signaling is triggered by breast cancer cell membrane-derived soluble CD44 (sCD44) antigen, and targeting sCD44 antigen may provide an alternative therapeutic strategy for breast cancer treatment by modulating inflammatory tumor microenvironment. SIGNIFICANCE: A novel positive feedback loop between IL1β and CD44 promotes TNBC malignant progression.

CD markers variations in chronic lymphocytic leukemia: New insights into prognosis

Chronic lymphocytic leukemia (CLL) is one of the most commonly occurring adult leukemias that is associated with clonal accumulation of mature apoptosis-resistant B-cells in bone marrow, peripheral blood, and specific tissues. Different pathogenesis factors can contribute to the aggression of the clinical course in this disease. Cytogenetic abnormalities and surface biomarkers of neoplastic CLL cells can be effective in the outcome of CLL, and the examination of changing CD markers expressions in the progression of CLL can be related to the prognosis of this disease. Changing expression levels of CD markers on lymphocytes and other cells in CLL patients can play a role in the aggressive clinical outcomes such as organomegaly, immunodeficiency, and advanced disease stages through their interaction with CLL microenvironment. Given the involvement of CD markers in the pathogenesis of CLL, it can be stated that recognizing the expression changes of CD markers in the cells involved in CLL can be a proper approach to evaluate prognosis among these patients.

C–C motif ligand 11 reduction in CLL patients serum after vitamin D supplementation

Background: Vitamin D (VD) deficiency results in a worse prognosis in patients with chronic lymphocytic leukemia (CLL) and may affect the production of cytokines. Nonetheless, there is the lack of studies dealing with VD supplementation and its impact on chemokines in CLL patients.

Aim: The primary endpoint of our interventional study was to evaluate the effect of cholecalciferol supplementation on serum chemokines levels in CLL patients.

Materials and methods: Eighteen subjects with CLL were enrolled for the study. Six-month-long cholecalciferol supplementation was performed in CLL patients with serum 25-OH-D₃ levels below 30 ng/ml. Cytokines levels were assessed at the beginning of the study and after 6 months. Baseline measurements of cytokines were compared to those in apparently healthy controls.

Results: Increased levels of CCL2, CCL3, CCL4, CXCL8, CXCL10, TNFα, bFGF, G-CSF, and VEGF were found in CLL patients in comparison with the healthy controls. In the course of the VD supplementation a decrease in serum levels of chemokines CCL11, CCL3, and cytokine PDGF-BB was observed. The decrease of CCL11 was found in CLL patients on VD supplementation solely, whereas the decrease of CCL3 and PDGF-BB was observed in CLL subjects on both chemotherapy and VD supplementation.

Conclusion: The VD supplementation may exert beneficial effect on chemokines levels in CLL patients with VD deficiency.

The Breast Cancer to Bone (B2B) Metastases Research Program: a multi-disciplinary investigation of bone metastases from breast cancer

Background

Bone is the most common site of breast cancer distant metastasis, affecting 50–70 % of patients who develop metastatic disease. Despite decades of informative research, the effective prevention, prediction and treatment of these lesions remains elusive. The Breast Cancer to Bone (B2B) Metastases Research Program consists of a prospective cohort of incident breast cancer patients and four sub-projects that are investigating priority areas in breast cancer bone metastases. These include the impact of lifestyle factors and inflammation on risk of bone metastases, the gene expression features of the primary tumour, the potential role for metabolomics in early detection of bone metastatic disease and the signalling pathways that drive the metastatic lesions in the bone.

Methods/Design

The B2B Research Program is enrolling a prospective cohort of 600 newly diagnosed, incident, stage I-IIIc breast cancer survivors in Alberta, Canada over a five year period. At baseline, pre-treatment/surgery blood samples are collected and detailed epidemiologic data is collected by in-person interview and self-administered questionnaires. Additional self-administered questionnaires and blood samples are completed at specified follow-up intervals (24, 48 and 72 months). Vital status is obtained prior to each follow-up through record linkages with the Alberta Cancer Registry. Recurrences are identified through medical chart abstractions. Each of the four projects applies specific methods and analyses to assess the impact of serum vitamin D and cytokine concentrations, tumour transcript and protein expression, serum metabolomic profiles and in vitro cell signalling on breast cancer bone metastases.

Discussion

The B2B Research Program will address key issues in breast cancer bone metastases including the association between lifestyle factors (particularly a comprehensive assessment of vitamin D status) inflammation and bone metastases, the significance or primary tumour gene expression in tissue tropism, the potential of metabolomic profiles for risk assessment and early detection and the signalling pathways controlling the metastatic tumour microenvironment. There is substantial synergy between the four projects and it is hoped that this integrated program of research will advance our understanding of key aspects of bone metastases from breast cancer to improve the prevention, prediction, detection, and treatment of these lesions.

CD44 regulates the apoptotic response and promotes disease development in chronic lymphocytic leukemia

The cell-surface glycoprotein CD44 is expressed in chronic lymphocytic leukemia (CLL), but its functional role in this disease is poorly characterized. We therefore investigated the contribution of CD44 to CLL in a murine disease model, the Eµ-TCL1 transgenic mouse, and in CLL patients. Surface CD44 increased during murine CLL development. CD44 expression in human CLL was induced by stimulation with interleukin 4/soluble CD40 ligand and by stroma cell contact. Engagement of CD44 by its natural ligands, hyaluronic acid or chondroitin sulfate, protected CLL cells from apoptosis, while anti-CD44 small interfering RNAs impaired tumor cell viability. Deletion of CD44 during TCL1-driven murine leukemogenesis reduced the tumor burden in peripheral blood and spleen and led to a prolonged overall survival. The leukemic cells from these CD44 knockout animals revealed lower levels of antiapoptotic MCL1, a higher propensity to apoptosis, and a diminished B-cell receptor kinase response. The inhibitory anti-CD44 antibodies IM7 and A3D8 impaired the viability of CLL cells in suspension cultures, in stroma contact models, and in vivo via MCL1 reduction and by effector caspase activation. Taken together, CD44 expression in CLL is mediated by the tumor microenvironment. As a coreceptor, CD44 promotes leukemogenesis by regulating stimuli of MCL1 expression. Moreover, CD44 can be addressed therapeutically in CLL by specific antibodies.

The PD-1/PD-L1 axis contributes to T-cell dysfunction in chronic lymphocytic leukemia

Chronic lymphocytic leukemia is marked by profound defects in T-cell function. Programmed death-1 is a receptor involved in tumor-mediated immunosuppression through binding of the PD-L1 ligand. Multiparametric flow cytometry and immunohistochemistry were used to study PD-1/PD-L1 expression. Functional assays were used to determine the involvement of the PD-1/PD-L1 axis in T-cell responses. PD-1 expression by CD4(+) and CD8(+) T lymphocytes was significantly higher in 117 chronic lymphocytic leukemia patients than in 33 donors of a comparable age. CD4(+) and CD8(+) T lymphocytes from chronic lymphocytic leukemia patients displayed increased numbers of effector memory and terminally differentiated cells, respectively, when compared to controls. The number of effector memory CD4(+) and terminally differentiated CD8(+) lymphocytes positively associated with a more advanced stage of disease, treatment requirements and unfavorable genomic aberrations. Furthermore, leukemic lymphocytes expressed higher levels of PD-L1 than circulating B lymphocytes from normal donors. PD-1 and PD-L1 surface expression spiked in proliferating T and B lymphocytes, suggesting that this interaction works efficiently in activated environments. Within chronic lymphocytic leukemia proliferation centers in the lymph node, CD4(+)/PD-1(+) T lymphocytes were found to be in close contact with PD-L1(+) chronic lymphocytic leukemia cells. Lastly, functional experiments using recombinant soluble PD-L1 and blocking antibodies indicated that this axis contributes to the inhibition of IFN-γ production by CD8(+) T cells. These observations suggest that pharmacological manipulation of the PD-1/PD-L1 axis may contribute to restoring T-cell functions in the chronic lymphocytic leukemia microenvironment.