Higher MMP9 and FGF2 Protein Levels and Elevated MMP9/TIMP Ratios Were Associated with JAK2V617F Mutation Regardless of Allele Burden in Myelofibrosis

Background: Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are involved in tumor neoangiogenesis which plays an important role in hematological neoplasias progression and prognosis. Myelofibrosis (MF) and essential thrombocythemia (ET) are myeloproliferative neoplasms (MPNs) resulting from acquired hematopoietic stem cell mutations. Most patients share the JAK2V617F mutation and may exhibit substantial overlap. The molecular mechanisms involved in MPNs pathogenesis are not completely elucidated. In this context, evaluation of genes and proteins related with angiogenesis could be useful to better understand MPN pathobiology.

Aims: To investigate the mRNA and protein expressions of MMPs and TIMPs and their relationship with plasma markers of angiogenesis (VEGFA and FGF2) and JAK2V617F mutation status in MF and ET patients.

Methods: Forty-three MPNs patients (MF=29 and ET=14) and 36 control subjects were studied. The controls were matched with patients according to age and gender. MPN diagnosis was defined according to the 2008 WHO criteria. The MMP2, MMP9, TIMP1 and TIMP2 mRNA expression from peripheral leukocytes and serum proteins levels were measured by real time PCR and Luminex technology. VEGFA and FGF2 concentration were measured in plasma from MPN patients and controls. JAK2V617F mutation status and allele burden and MPL W515K/L analysis were performed in total leukocytes DNA by real time PCR, using Taqman MGB probes.

Results: Higher MMP2, MMP9 and TIMP1 mRNA expression were observed in MF patients compared to controls (P<0.05). The frequencies of JAK2V617F mutated patients were 62.1% for MF and 35.7% for TE. The allele burden was similar in MF and ET groups. MF patients positive for JAK2V617F presented higher protein levels of MMP9 (N=18, P=0.008) and FGF2 (N=18, P=0.009) when compared with non-carriers of mutation (N=11). In contrast, no correlations were found between allele burden and MMP9 (r=0.153, P=0.558, N= 18) or allele burden and FGF2 (r=0.069, P=0.794, N=18). Carriers of JAK2V617F in MF group (N=17) showed elevated MMP-9/TIMP1 and MMP9/TIMP2 ratios of protein levels than those MF JAK2V617F negative (N=11, P<0.025). ET patients JAK2V617F positive presented higher MMP9 mRNA level (N=5) compared with negative ones (N=9, P=0.009), but no difference was observed in protein levels. None of patients presented MPL W515K/L mutation.

Conclusions:Our findings suggest that MF patients with JAK2V617F mutation exhibit higher MMP9 and FGF2 protein levels and elevated MMP9/TIMP ratios, which are not associated with JAK2V617F allele burden.

Financing: FAPESP 2012/12957-5