Gene Expression Profiling in Polycythemia Vera (PV)

To define the molecular abnormalities at the stem cell level in polycythemia vera (PV), we examined global gene expression in circulating CD34+ cells from 19 JAK2 V617F-positive PV patients and 6 normal individuals using Affymetrix oligonucleotide microarray technology. We observed that CD34+ cell gene expression not only differed between the PV patients and the normal controls but also between men and women PV patients. Based on these gender-specific differences in gene expression, we were able to identify 102 genes differentially regulated concordantly by both men and women, which likely represent a core set of genes whose dysregulation is involved in the pathogenesis of PV. Gene expression was verified by Q-PCR of patient CD34+ cell RNA. Using the 102 gene set and unsupervised hierarchical clustering, the 19 PV patients could be separated in two groups that differed significantly with respect to hemoglobin level, thrombosis frequency, splenomegaly, splenectomy or chemotherapy exposure, leukemic transformation and overall survival. These results were confirmed using top scoring pairs, which identified a different set of 29 genes that independently segregated the 19 patients into the same two clinical groups: those with an aggressive form of the disease (7 patients), and those with an indolent form (12 patients). Samples from 19 PV patients (8 men and 11 women) and 6 normal controls (3 men and 3 women) were analyzed using Affymetrix oligonucleotide microarray U133A.