Highly Deregulated Fibulins in Patients with Philadelphia-Negative Chronic Myeloproliferative Neoplasms

Introduction

The Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) develop in a biological continuum from the early cancer stages (ET/PV) to the advanced myelofibrosis stage characterized by huge splenomegaly, bone marrow failure and -fibrosis. Importantly, bone marrow fibrosis also increases from the early stages with reticulin fibrosis only and later deposition of mature collagen as well. Fibulins are glycoproteins that are important constituents of the extracellular matrix (ECM). Thus, fibulins have been shown to modulate cell morphology, growth, adhesion and motility. Dysregulation of fibulins has been reported in several cancers. In addition, upregulation of fibulins and elevated circulating fibulins have been reported in diseases - other than cancers -, in which chronic inflammation is an important pathogenetic factor, such as cardiovascular diseases. Thus, deregulated fibulins have been described in patients with type 2 diabetes mellitus. Herein, using whole blood gene expression profiling, we for the first time report deregulated fibulins in patients with MPNs.

Aim

To detect if genes associated with pre-atherosclerotic changes in type II diabetes are deregulated in patients with MPNs.

Material and methods

Gene expression microarrays were applied to generate gene expression profiles of whole blood from control subjects (n=21) and patients with ET (n=19), PV (n=41), and PMF (n=9). Total RNA was purified, amplified to biotin-labeled aRNA and hybridized to microarray chips. The statistical software R was applied to perform initial data processing and statistical analysis of gene expression changes between patients and control subjects. An FDR <0.05 was considered significant.

Results

We identified 23,657, 25,567, and 17,417 probe sets which were significantly differentially expressed between controls and patients with ET, PV, and PMF, respectively (FDR < 0.05). We focused upon the top 15 upregulated genes from a previous gene expression microarray study performed on arterial tissue from patients with type 2 diabetes compared to non-diabetic patients undergoing artery bypass graft surgery. Several of these genes were significantly deregulated in patients with MPNs (Table 1). In patients with ET, FBLN1, FBLN2,FAM107A, IGF2, MEG3, and ELN were significantly upregulated and ZFP36L2 were significantly downregulated. In patients with PV, FBLN1, FBLN2, ELN, LEPR, FAM107A, IGF2, CRISPLD2, and MEG3 were significantly upregulated and ZFP36L2 and SERPINF1 were significantly downregulated. In patients with PMF, MEG3, LEPR, FBLN1, FAM107A, ELN, IGF2, and VWF were significantly upregulated and ZFP36L2 and SERPINF1 were significantly downregulated.

Discussion and conclusions

Fibulins regulate several cellular functions including tissue homeostasis and remodeling after injury, angiogenesis, and tumorigenesis. Thus, fibulins have been reported to be upregulated in several cancer types, in which deregulated fibulins have been associated with cancer invasiveness and disease progression. We have for the first time shown that fibulins are also highly deregulated in patients with MPNs. The significance of our findings is presently unknown but since interactions between fibulins and transforming growth factor (TGFbeta) have been demonstrated, upregulated fibulins may enhance the capacities of TGFbeta, which shares several of the regulatory functions excerted by fibulins. In the context of chronic inflammation being a driving force for MPN development during the biological continuum from early cancer stages to the advanced myelofibrosis stage and chronic inflammation likely also accelerates the development of atherosclerosis in MPNs, it is highly intriguing to note that fibulins are also elevated in arteries from patients with type 2 diabetes mellitus. Thus, upregulated fibulins in blood cells may actually indirectly reflect ongoing matrix modelling during atherosclerosis development, including remodeling and turnover of basement membranes in the inflamed endothelium. In conclusion, highly deregulated fibulins have been demonstrated in circulating blood cells by whole blood gene expression profiling. Further studies are needed to assess the significance of our findings in terms of potential associations to modelling of ECM in the bone marrow and during development of atherosclerosis in MPNs.

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