Clinical significance of serum soluble interleukin-2 receptor in chronic myeloproliferative disorders

Inflammatory Pathophysiology as a Contributor to Myeloproliferative Neoplasms

Myeloid neoplasms, including acute myeloid leukemia (AML), myeloproliferative neoplasms (MPNs), and myelodysplastic syndromes (MDS), feature clonal dominance and remodeling of the bone marrow niche in a manner that promotes malignant over non-malignant hematopoiesis. This take-over of hematopoiesis by the malignant clone is hypothesized to include hyperactivation of inflammatory signaling and overproduction of inflammatory cytokines. In the Ph-negative MPNs, inflammatory cytokines are considered to be responsible for a highly deleterious pathophysiologic process: the phenotypic transformation of polycythemia vera (PV) or essential thrombocythemia (ET) to secondary myelofibrosis (MF), and the equivalent emergence of primary myelofibrosis (PMF). Bone marrow fibrosis itself is thought to be mediated heavily by the cytokine TGF-β, and possibly other cytokines produced as a result of hyperactivated JAK2 kinase in the malignant clone. MF also features extramedullary hematopoiesis and progression to bone marrow failure, both of which may be mediated in part by responses to cytokines. In MF, elevated levels of individual cytokines in plasma are adverse prognostic indicators: elevated IL-8/CXCL8, in particular, predicts risk of transformation of MF to secondary AML (sAML). Tumor necrosis factor (TNF, also known as TNFα), may underlie malignant clonal dominance, based on results from mouse models. Human PV and ET, as well as MF, harbor overproduction of multiple cytokines, above what is observed in normal aging, which can lead to cellular signaling abnormalities separate from those directly mediated by hyperactivated JAK2 or MPL kinases. Evidence that NFκB pathway signaling is frequently hyperactivated in a pan-hematopoietic pattern in MPNs, including in cells outside the malignant clone, emphasizes that MPNs are pan-hematopoietic diseases, which remodel the bone marrow milieu to favor persistence of the malignancy. Clinical evidence that JAK2 inhibition by ruxolitinib in MF neither reliably reduces malignant clonal burden nor eliminates cytokine elevations, suggests targeting cytokine mediated signaling as a therapeutic strategy, which is being pursued in new clinical trials. Greater knowledge of inflammatory pathophysiology in MPNs can therefore contribute to the development of more effective therapy.

Cytokines frequently implicated in myeloproliferative neoplasms

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MPN is a chronic inflammation-driven tumor model.

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Many cytokines are involved in pathogenesis and progression of MPN.

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IL-1β, TNF-α, IL-6, IL-8, VEGF, PDGF, TGF-β and IFNs are critical in MPN.

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Cytokine directed therapy could be an alternative treatment for MPN in future.

Classical myeloproliferative neoplasms (MPN) include polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). MPN has been defined as a chronic inflammation-driven tumor model. It is clear that there is a close link between chronic inflammation and MPN pathogenesis. Several studies have demonstrated cytokine profiles in MPN patients. Other studies have used cell lines or animal models aiming to clarify the underlying mechanism of cytokines in the pathogenesis of MPN. However, important questions remain: (1) among all these cytokines, which are more predictive? and (2) which are more critical? In this review, we summarize cytokines that have been investigated in MPN and highlight several cytokines that may be more significant in MPN. We suggest that cytokines are more critical in PMF than PV or ET. These cytokines include IL-1β, TNF-α, IL-6, IL-8, VEGF, PDGF, IFNs and TGF-β, all of which should be more closely investigated in MPN. Based on our extensive literature search, several key factors have emerged in our understanding of MPN: first, TNF-α could correlate with MPN progression including PMF, PV and ET. IL-1β plays a role in PMF progression, while it showed no relation with PV or ET. Second, IL-8 could be a prognostic factor for PMF, and IL-6 could be important for MPN progression. Third, VEGF and PDGF play an indirect role in MPN development and their inhibitors could be effective. Fourth, different subtypes of IFNs could have different effects in MPN. Finally, TGF-β is closely linked to MF, although the data are inconsistent. Agents that have targeted these cytokines described above are already in clinical trials, and some of them have even been used to treat MPN patients. Taken together, it will be critical to continue to investigate the precise role of these cytokines in the pathogenesis and progression of MPN.

Circulating Cytokine Levels as Markers of Inflammation in Philadelphia Negative Myeloproliferative Neoplasms: Diagnostic and Prognostic Interest

Cytokines are well known mediators of numerous physiological and pathological processes. They contribute to the regulation of normal hematopoiesis but increasing data suggest that they also have a clinical impact in some hematopoietic malignancies. In particular, there is evidence that cytokines are implicated in the functional symptoms of Philadelphia negative myeloproliferative neoplasms (Ph- MPNs), suggesting that evaluation of circulating levels of cytokines could be of clinical interest for the characterization of patients at the time of diagnosis and for disease prognosis. In this review, we present the current knowledge on alteration of circulating cytokine profiles in MPNs and their role in myelofibrosis pathogenesis. Phenotypic correlation, prognostic value of cytokines, and impact of JAK inhibitors are also discussed.

Increased level of myeloid-derived suppressor cells, programmed death receptor ligand 1/programmed death receptor 1, and soluble CD25 in Sokal high risk chronic myeloid leukemia

Immunotherapy (eg interferon α) in combination with tyrosine kinase inhibitors is currently in clinical trials for treatment of chronic myeloid leukemia (CML). Cancer patients commonly have problems with so called immune escape mechanisms that may hamper immunotherapy. Hence, to study the function of the immune system in CML is of interest. In the present paper we have identified immune escape mechanisms in CML with focus on those that directly hamper T cells since these cells are important to control tumor progression. CML patient samples were investigated for the presence of myeloid-derived suppressor cells (MDSCs), expression of programmed death receptor ligand 1/programmed death receptor 1 (PD-L1/PD-1), arginase 1 and soluble CD25. MDSC levels were increased in samples from Sokal high risk patients (p<0,05) and the cells were present on both CD34 negative and CD34 positive cell populations. Furthermore, expression of the MDSC-associated molecule arginase 1, known to inhibit T cells, was increased in the patients (p = 0,0079). Myeloid cells upregulated PD-L1 (p<0,05) and the receptor PD-1 was present on T cells. However, PD-L1 blockade did not increase T cell proliferation but upregulated IL-2 secretion. Finally, soluble CD25 was increased in high risk patients (p<0,0001). In conclusion T cells in CML patients may be under the control of different immune escape mechanisms that could hamper the use of immunotherapy in these patients. These escape mechanisms should be monitored in trials to understand their importance and how to overcome the immune suppression.

Serum interleukin (IL)-1, IL-2, sIL-2Ra, IL-6 and thrombopoietin levels in patients with chronic myeloproliferative diseases

A number of growth factors are involved in clonal haematopoietic expansion and their clinical significance in patients with chronic myeloproliferative diseases requires further evaluation. Using enzyme-linked immunosorbent assays, we analysed serum levels of interleukin (IL)-1a, IL-1b, IL-2, IL-6, the soluble IL-2 receptor alpha (sIL-2Ra), and thrombopoietin (TPO), in 25 individuals with myelofibrosis with myeloid metaplasia (MMM), 40 with essential thrombocythaemia (ET), eight with polycythaemia vera (PV), 10 patients with chronic myeloid leukaemia (CML) and 27 normal controls. These were correlated with clinicopathological characteristics including overall survival, and histopathological bone marrow features, including angiogenesis. The serum derived from patients with MMM, ET, PV and CML contained significantly higher IL-2 and sIL-2Ra than healthy subjects, while IL-6 levels were higher only in MMM and CML than controls. IL-2, sIL-2Ra and IL-6 levels were raised during the transformation phase of CML, during progression of MMM to AML, and ET and PV to myelofibrosis (P < 0.001). There was a positive correlation between IL-2, sIL-2Ra, IL-6 and angiogenesis in bone marrow samples. Cytokines may be useful markers for predicting clinical evolution, reflecting increased angiogenesis. This requires further evaluation to guide diagnostic and therapeutic options.

Serum beta-2-microglobulin, TNF-alpha and interleukins in myeloproliferative disorders

Whereas beta-2-microglobulin (beta2M) has mainly been used as a prognostic factor in patients with lymphoproliferative disorders, some studies have reported the value of beta2M in myeloproliferative disorders (MPD). In order to investigate a potential role in the pathogenesis of MPD and to find a possible value as indicators in monitoring the course of the disease, we measured beta2M, TNF-alpha, IL-1alpha, IL-1beta, IL-2, sIL-2R, IL-6 and IL-10 in 55 patients with MPD, at diagnosis and during the course of the disease. In progressive disease and particularly when transformation to acute leukemia occurred, high levels of beta2M, IL-2 and sIL-2R were found in all patients; the elevation was progressive, which suggests a potential prognostic usefulness in the individual patient.

Pharmacokinetics of recombinant human interleukin-2 in advanced renal cell carcinoma patients following subcutaneous application

AIMS

The aim of the study was to investigate the pharmacokinetics of recombinant human interleukin-2 (rhIL-2) in patients with metastatic renal cell carcinoma following different subcutaneous (s.c.) administration regimens.

METHODS

RhIL-2 was administered subcutaneously to 10 patients according to two different dosing regimens: group A received 20 x 10(6) IU m(-2) once daily and group B 10 x 10(6) IU m(-2) twice daily (every 12 h). Additionally, in all patients the influence of soluble interleukin-2 receptor (sIL-2R) on the pharmacokinetics of rhIL-2 was investigated.

RESULTS

The mean area under the serum concentration-time curve to 24 h (AUC(0,24 h)) was 627 IU ml(-1) h in treatment group A and 1130 IU ml(-1) h (P=0.029) in treatment group B. In both study groups Cmax and AUC(0,12 h) were not significantly different. Seventy-two hours after the beginning of s.c. rhIL-2 therapy the sIL-2R increased significantly (P=0.016), and sIL-2R levels over 1200 pmol l(-1) seemed to reduce the AUC.

CONCLUSIONS

In patients with metastatic renal cell cancer administration of 20 x 10(6) IU m(-2) of rhIL-2 s.c. in two daily doses (10 x 10(6) IU m(-2) every 12 h) provides better bioavailability and is preferable to the single dose administration.