Revisiting the IGF-1R Signaling Pathway in Myeloproliferative Neoplasms: Quantification of IGF-1 Receptor May be Useful in the Differential Diagnosis of Polycythemia

Abstract Endogenous erythroid colony formation in vitro is one of the important criteria for the diagnosis of polycythemia vera (PV). Extensive studies performed in the last decade suggest that IGF-1 plays a significant role in the erythropoiesis and endogenous colony formation in PV. Therefore, IGF-1R signal pathway is important in the pathogenesis of PV. We elected to revisit IGF-1R pathway by flow cytometry technique in PV and other myeolproliferative neoplasms (MPNs). 32 MPN patients (including 11 PV, 19 myelofibrosis (MF), 12 essential thrombocytopenia (ET), 8 secondary PV , and 17 age-matched normal controls were studied. Methods: 1) plasma IGF-1, IGFBP-1, IGFBP-3 were assayed by ELISA(RD 2) quantification of IGF-1R . Peripheral blood mononuclear cells (MNC) harvested from Ficoll-Paque separation were stained with phycoerythrin conjugated antibody against IGF-1 receptor (RD 3) quantification of IGF-1R phosphoration (pIGF-1R) after IGF-1 stimulation. MNC cells were suspended in serum-free α-MEM medium for 2 hours, then starved cells were treated with or without 10 nM IGF-1 for 3 min and assayed for pIGF-1R by flow cytometry using Alexa Fluor 647 conjugated antibody against phosphorylated IGF-1 receptor (BD Biosciences); 4) Interferon alpha (IFNα) Treatment. IFN-α (Schering Corporation, Kenilworth, NJ) was added to the cell culture at 100 unit per ml. Cells were incubated with IFN-α for either 2 hours or 3 days and then collected for further pIGF-1R analysis. The results showed 1) No difference in plasma IGF-1 levels in MPN and controls; IGFBP-1 and IGFBP-3 were significantly elevated in MPN than controls but the change of IGFBP-3 in MF patients was not significant. 2) the PV group had significantly elevated IGF-1R expression than secondary PV (Fig 1). Mean ± SE (MFI expression) were 529 ± 84 and 90 ± 30 in PV versus secondary PV, respectively (p=0.004). 3) The untreated PV group had significantly higher IGF-1R than MF, ET, and controls. MF and ET were not different from controls, but 8/19 (43%) in MF and 6/12 (50%) in ET have elevated IGF-1R than controls. 4) No difference in IGF-1R expression in Jak2 (+) versus Jak2 (-) in MPN patients. Mean ± SE (MFI) were 293.2 ± 62.1 and 164.8 ± 47.7 in JAK2(+) versus JAK2 (-) respectively (p=NS). 5) Preliminary studies showed PV has a significant elevated pIGF-1R than controls in unstimulated PB CD34+ cells, but not in MNC cells. 6) IFN-α decreased IGF-1R expression and pIGF-IR about 10% in the PV group. Conclusions: 1) IGF1R signal pathway is more active in PV than MF, ET and controls. 2) Quantification of IGF-1R expression by flow cytometry may be helpful in differential diagnosis in primary versus secondary PV. 3) IGF-1R expression is not correlated with JAK2 status. 4) IGF-1R phosphorylation is more elevated in unstimulated CD34+ cells of PV patients than in controls suggesting autonomous erythroid colony formation in PV may be associated with IGF-1R activation. 5) interferon-α has some inhibitory effects in IGF-1R expression and phosphorylation but is unlikely to be the main mechanism of its induced remission of JAK2 –mutant allele-burden effects. Download : Download high-res image (41KB) Download : Download full-size image Figure 1 . Disclosures No relevant conflicts of interest to declare.