Correlation of JAK2 Mutation and PRV-1 and WT1 Transcript Amount in Myeloproliferative Disorders.

Recently, a JAK2V617F mutation has been described in the majority of patients with polycythemia vera (PV), and in a subset of patients with essential thromocythemia (ET) and idiopathic myelofibrosis (IMF). Similarly, PRV-1 has been found overexpressed in many of these patients. The aim of the study was to correlate PRV-1 and WT1 expression with the presence of JAK2 mutation in order to establish whether these markers identify the same subset of patients. Using a Real Time PCR we studied the expression level of PRV1 and WT1 in 330 patients including 26 IMF, 156 PV, 122 ET, 16 HES. 10 familiar forms of PV were included. In addition a control group of 50 healthy subject and 60 reactive conditions were studied All the patients were analyzed for the presence of JAK2 mutation using the ABI Prims 3100 genetic analyzer. We found that JAK2 mutation was present in 50 % of IMF, 93% of PV and 55% of ET and 6% of HES. PRV-1 was increased in 84% of IMF, 98% of PV and 90% of ET and it was not increased in HES. WT1 was increased in 99% of IMF, 45% of PV and 42% of ET and 100% of HES. No mutations of JAK2 were detected in normal subjects or in reactive conditions. Both WT1 and PRV1 were expressed at low levels in normal subject (for PRV1 the mean value of 2^{-Delta Delta Ct} was 2,05; range 0,05–5,46; for WT1 mean value WT1 copies/10⁴ ABL copies of 4; range 0–20). The mean value of WT1 copies/10⁴ ABL copies in IMF was 306 (p=0,00004 compared to normal controls), in PV was 156 (p=0,0001), in ET was 202 (p=0,0002) and in HES was 161 (p=0,0004). PRV1 mean value in IMF was 144 expressed as 2^{−Delta Delta Ct}, and it was 423 in PV and 290 in ET. Moreover the correlation between the three markers allowed to establish that both WT1 and PRV1 were higher in JAK2 mutated samples when compared to wild type JAK2 with a p value of 0,001 for WT1 and 0,004 for PRV1. In spite of these we were able to identify a subset of patients affected by IFM characterized by increased values of PRV1 and WT1 but not by JAK2 mutation (34%) and a small subset 15% characterized only by WT1 overexpression. Only 5% of PV and 35% of ET patients expressed only PRV-1 but not JAK2 mutation and WT1 expression. HES patients overexpressed WT1 but not PRV1 and only one patient presented the JAK2 mutation. Finally 10 patients affected by familiar form of PV were studied. All the subjects showed normal PRV-1 expression but high level of WT1 transcript and 9 out of 10 presented the JAK2 mutation. This study demonstrates that the combination of all these markers is probably useful for a correct diagnosis of these patients but further studies are required to stratify these patients and to better classify them according to the presence of molecular lesions.