Comprehensive Plasma Cytokine Profiling in Polycythemia Vera: Comparison with Myelofibrosis and Clinical Correlates,

We have recently shown that primary myelofibrosis (PMF) was associated with increased plasma levels of IL-1b/IL-1RA/IL-2R/IL-6/IL-8/IL-10/IL-12/IL-13/IL-15/TNF-α/G-CSF/INF-α/MIP-1α/MIP-1b/HGF/IP-10/MIG/MCP-1/VEGF in PMF (J Clin Oncol 2011; 29: 1356). In addition, increased levels of IL-8, IL-2R, IL-12, IL-15 and IP-10 were independently associated with inferior survival. In the current study, we focused on the plasma cytokine profile in polycythemia vera (PV) and examined how it compares with PMF or in a cohort of PV patients whose samples were collected during follow-up. We also looked for phenotypic and prognostic correlates.

Study inclusion for patients with PV required availability of archived plasma within one year of diagnosis. Samples from PV patients seen at different points post-diagnosis were also collected, in order to compare their cytokine profile with that of patients whose samples were collected within one year of diagnosis. Standard procedures were followed to centrifuge peripheral blood samples at 4°C and store aliquots at −80°C. Concentrations of 30 plasma cytokines/chemokines were analyzed in duplicates using Multiplex Bead-based Luminex Technology (Invitrogen, Carlsbad, CA, USA): IL-1β, IL-1RA, IL-2, IL-2R, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-15, IL-17, EGF, eotaxin, FGF-b, GM-CSF, G-CSF, HGF, IFN-α, IFN-γ, IP-10, MCP-1, MIG, MIP-1α, MIP-1β, RANTES, TNF-α, and VEGF. Measurements were performed on a Luminex 200 analyzer (Luminex Corporation, Austin, TX, USA) and resulting data were evaluated using STarStation Software Version 2.3 (Luminex Corporation, Austin, TX, USA).

Plasma cytokines in PV (n=36 for samples collected within one year of diagnosis and n=40 for samples collected beyond that time point) vs. PMF (n=92) vs. normal controls (n=35) There was no significant difference between the three groups in the plasma levels of the following cytokines: IL-1β, IL-2, IL-4, EGF, and IL-17. PV and normal controls had similar levels of IL-2R, IL-5, FGF-b, and TNF-α; all four cytokines were elevated in PMF. The levels of the following cytokines were equally increased in PV and PMF: IL-1RA, IL-7, HGF, MIG, and VEGF. The following cytokines were also elevated in both PMF and PV but predominantly so in PV (MIP-1α) or PMF (IL-6, IL-8, IL-12, IL-13, IL-15, MIP-1β, IP-10, and MCP-1). Eotaxin and GM-CSF were elevated in PV but not PMF. Compared to normal controls, significantly lower levels were noted for IL-10 in PV and IFN-α and IFN-γ for PMF. IFN-α and IFN-γ levels were both elevated in PV. Comparison of PV samples collected within one year of diagnosis (n =36) vs. those collected beyond that time point (n =40) showed significantly increased levels of IL-8 (p=0.0005) and borderline significant increases in IP-10 (p=0.09) and IL-2R (p=0.09).

Clinical correlates of plasma cytokines in PV Among the above-listed cytokines that were abnormally increased or decreased in PV, significant correlations were seen with sex (IP-10 and GM-CSF), age (IP-10, eotaxin), platelet count (MIG), hemoglobin level (IL-6), arterial thrombosis (IFN-γ, IL-1RA, VEGF, MIP-1α), and abnormal karyotype (IL-13, MIP-1α). None of the cytokines correlated with leukocyte count, venous thrombosis, pruritus or microvascular symptoms. The following, treated as continuous variables, were associated with inferior survival: IL-7, HGF, IFN-α, MCP-1, GM-CSF and IL-10 (p<0.05 for all). The number of events and sample size were too small to perform multivariable analysis.

Plasma cytokine levels in PV are markedly abnormal and show both similarities and differences with PMF; the similarities became more pronounced in patients whose samples were examined at later stages of their disease. The current study suggests prognostic implications that warrant validation in a larger number of patients.

No relevant conflicts of interest to declare.