Impact of the rs1024611 Polymorphism of CCL2 on the Pathophysiology and Outcome of Primary Myelofibrosis.

Elena Masselli,Giovanni Roti,Giovanni Barosi,Cecilia Carubbi,Margherita Massa,Marco Vitale,Antonio Percesepe,Laura Villani,Rita Campanelli,Giuliana Gobbi,Vittorio Rosti,Giulia Pozzi,Sabrina Bonomini

doi:10.3390/cancers13112552

Abstract

Simple SummaryAmong myeloproliferative neoplasms, primary myelofibrosis (PMF) is considered the paradigm of inflammation-related cancer development. Host genetic variants such as single nucleotide polymorphisms (SNPs) can affect cytokine/chemokine gene expression and may therefore have a role in a disease with a strong inflammatory component such as PMF. Here we demonstrate that the homozygosity for the rs1024611 SNP of the chemokine CCL2 represents a high-risk variant and a novel host genetic determinant of reduced survival in PMF, providing opportunities for CCL2 SNP genotyping as a potential novel strategy to risk-stratify patients. The rs1024611 genotype also influences CCL2 production in PMF cells, which are electively sensitive to CCL2 effects because of their unique expression of its receptor CCR2. Finally, ruxolitinib is capable of effectively down-regulating CCR2 expression, de-sensitizing PMF cells to the IL-1β-dependent pro-inflammatory stimulus.Single nucleotide polymorphisms (SNPs) can modify the individual pro-inflammatory background and may therefore have relevant implications in the MPN setting, typified by aberrant cytokine production. In a cohort of 773 primary myelofibrosis (PMF), we determined the contribution of the rs1024611 SNP of CCL2—one of the most potent immunomodulatory chemokines—to the clinical and biological characteristics of the disease, demonstrating that male subjects carrying the homozygous genotype G/G had an increased risk of PMF and that, among PMF patients, the G/G genotype is an independent prognostic factor for reduced overall survival. Functional characterization of the SNP and the CCL2-CCR2 axis in PMF showed that i) homozygous PMF cells are the highest chemokine producers as compared to the other genotypes; ii) PMF CD34+ cells are a selective target of CCL2, since they uniquely express CCR2 (CCL2 receptor); iii) activation of the CCL2-CCR2 axis boosts pro-survival signals induced by driver mutations via Akt phosphorylation; iv) ruxolitinib effectively counteracts CCL2 production and down-regulates CCR2 expression in PMF cells. In conclusion, the identification of the role of the CCL2/CCR2 chemokine system in PMF adds a novel element to the pathophysiological picture of the disease, with clinical and therapeutic implications.

Highlights

Myelofibrosis (MF) is the most aggressive Philadelphia-chromosome negative myeloproliferative neoplasm (MPN), typified by abnormal proliferation and differentiation of hematopoietic progenitors, variable degree of bone marrow fibrosis and cytopenias, elevated circulating CD34+ cells, splenomegaly and risk of blast transformation (BT) [1,2]
We proved the functional relevance of our findings in primary MF (PMF) pathophysiology by: (i) demonstrating that rs1024611 genotypes affect CCL2 production in PMF cells, (ii) assessing the effects of CCL2/CCR2 axis activation PMF hematopoietic progenitors, (iii) testing the down-regulation of the CCL2-CCR2 chemokine system by immunomodulatory therapy with ruxolitinib
We investigated whether the homozygosity for the single nucleotide polymorphisms (SNPs) could impact the disease outcome, assessing whether PMF harboring the G/G genotype have a higher chance of incurring in: (i) severe anemia (Hb < 100 g/L), massive splenomegaly (≥10 cm below costal margin) or leukocytosis (WBC ≥ 12 × 109/L); (ii) blast transformation; (iii) death for any cause

Summary

Introduction

Myelofibrosis (MF) is the most aggressive Philadelphia-chromosome negative myeloproliferative neoplasm (MPN), typified by abnormal proliferation and differentiation of hematopoietic progenitors, variable degree of bone marrow fibrosis and cytopenias, elevated circulating CD34+ cells, splenomegaly and risk of blast transformation (BT) [1,2]. Dysregulation of the JAK/STAT pathway, resulting from the occurrence of one of the three so called “driver mutations”, i.e., JAK2 exon 14 and exon 12 mutations, thrombopoietin receptor gene (Myeloproliferative Leukemia Protein, MPL) mutations or calreticulin (CALR) mutations, has been traditionally identified as the link between the neoplastic clone and cytokine overproduction in MF (and MPN in general) [7]. Host genetic variants such as single nucleotide polymorphisms (SNPs) are emerging as important players in modulating the individual pro-inflammatory background by affecting cytokine/chemokine gene expression and mRNA levels [8]. Inherited genetic variants predisposing to MF onset, phenotype and outcome, such as the JAK2 GGCC_46/1 haplotype [9,10] and the rs6198 SNP of NR3C1 [11], have the potential to predispose to enhanced inflammatory state and autoimmune disorders [12,13,14]

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