Lab tests for MPN

Abstract

Molecular laboratory investigations for myeloproliferative neoplasm (MPN) can ideally be divided into two distincts groups, those for the detection of the BCR-ABL rearrangement (suspect of chronic myeloid leukemia) and those for the variants determination of the driver genes of the negative Philadelphia forms (MPN Ph neg). The BCR-ABL detection is based on RT-Polymerase Chain Reaction techniques and more recently on droplet digital PCR (ddPCR). For this type of analysis, combined with chromosome banding analysis (CBA) and Fluorescent in situ hybridization (FISH), it is essential to quantify BCR-ABL mutated copies by standard curve method. The investigation on driver genes for MPN Ph neg forms includes activity for erythroid forms such as Polycythemia Vera (test JAK2V617F and JAK2 exon 12), for non-erythroid forms such as essential thrombocythemia and myelofibrosis (test JAK2V617F, CALR exon 9, MPL exon 10), for "atypical" ones such as mastocytosis (cKIT D816V test) and for hypereosinophilic syndrome (FIP1L1-PDGFRalpha test). It's crucial to assign prognosis value through calculating allelic burden of JAK2 V617F variant and determining CALR esone 9 variants (type1/1like, type2/2like and atypical ones). A fundamental innovation for investigating triple negative cases for JAK2, CALR, MPL and for providing prognostic score is the use of Next Generation Sequencing panels containing high molecular risk genes as ASXL1, EZH2, TET2, IDH1/IDH2, SRSF2. This technique allows to detect additional or subclonal mutations which are usually acquired in varying sized sub-clones of hematopoietic progenitors. These additional variants have a prognostic significance and should be indagated to exclude false negative cases.

Keywords: Additional or subclonal mutations; BCR-ABL rearrangements; CALR exon 9 variants; Driver genes variants; Droplet digital PCR; JAK2 V617F; MPL exon 10 variants; Next generation sequencing; RT-PCR.