BackgroundRapid identification of diverse fusion genes with involvement of PDGFRA or PDGFRB in eosinophilia-associated myeloproliferative neoplasms is essential for adequate clinical management but is complicated by the multitude and heterogeneity of partner genes and breakpoints. Design and MethodsWe established a generic quantitative reverse transcriptase polymerase chain reaction to detect overexpression of the 3'-regions of PDGFRA or PDGFRB as a possible indicator of an underlying fusion. ResultsAt diagnosis, all patients with known fusion genes involving PDGFRA (n=5; 51 patients) or PDGFRB (n=5; 7 patients) showed significantly increased normalized expression levels compared to 191 patients with fusion gene-negative eosinophilia or healthy individuals (PDGFRA/ABL: 0.73 versus 0.0066 versus 0.0064, P<0.0001; PDGFRB/ABL: 196 versus 3.8 versus 5.85, P<0.0001). The sensitivity and specificity of the activation screening test were, respectively, 100% and 88.4% for PDGFRA and 100% and 94% for PDGFRB. Furthermore, significant overexpression of PDGFRB was found in a patient with an eosinophilia-associated myeloproliferative neoplasm with uninformative cytogenetics and an excellent response to imatinib. Subsequently, a new SART3-PDGFRB fusion gene was identified by 5´-rapid amplification of cDNA ends polymerase chain reaction (5'-RACE-PCR). ConclusionsQuantitative reverse transcriptase polymerase chain reaction analysis is a simple and useful adjunct to standard diagnostic assays to detect clinically significant overexpression of PDGFRA and PDGFRB in eosinophilia-associated myeloproliferative neoplasms or related disorders. © F e r r a t a S t o r t i F o u n d a t i o n

treated with vitamin E, which reduced ROS by approximately twofold (Figure 1a). 9,11 Human CD45 þ cells collected from bone marrows and spleens of NSG mice formed colonies in vitro, and vitamin E treatment did not affect the engraftment (Figure 1b). Imatinib-resistant clones carrying either E255K or T315I BCR-ABL1 kinase mutations were detected in three out of five untreated xenografts, but in none of the vitamin E-treated samples (Table 1). In conclusion, we postulate that anti-oxidants such as vitamin E may be applicable in prevention of TKI-resistance, in particular of that driven by BCR-ABL1 kinase mutations. Moreover, as imatinibtreated CML-CP LSCs and LPCs continue to accumulate high levels of ROS resulting in TKI-resistant mutations, 9,10 anti-oxidant treatment could be combined with TKIs to extend/improve the therapeutic effects of ABL1 kinase inhibitors. This speculation is reinforced by the observation that anti-oxidants vitamin E and N-acetyl-cysteine reduced the percentage of the resistant clones emerging in vitro from imatinib-treated BCR-ABL1-positive cells. 11

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