The disordering of chromosomes in the course of reading and translating DNA during reproduction – during mitosis — is a critical factor in some blood diseases. (For example, translocation of genetic material on chromosomes is responsible for the creation of the BCR-ABL oncogene and the onset of chronic myeloid leukemia.)
Karyotyping is the analysis of chromosomes in the mitotic stage to determine deletions, insertions, and other disorders. While still not a routinely ordered test, this is a test that can uncover significant issues. Chromosomal anomalies occur in an estimated 17% of MF high risk patients. Their early discovery can help in determining the timing of stem cell transplant.
JAK2 and Other MPN Mutations
JAK2 and other mutations: The more familiar landscape of MPN mutations includes recognizable features like the JAK2 and CALR mutations. Mutations generally occur in the course of reproduction, arising within genes – sections of DNA residing within chromosomes. Genes are coded with the recipe to create proteins, like the JAK2 kinase. Mistakes in translating and combining the elements of that recipe are common. In the JAK2 mutation a simple transposition of two letters – two amino acids — creates the mutant JAK2 clone carried by about half of all MPN patients.
Recent advances in biotechnology have permitted the discovery of several MPN mutations, some relatively benign, some considered High Molecular Risk, such as ASXL1, EZH2, SRSF2, IDH1/2. This is an on-going search of a moving and expanding target whose precise role in driving myelofibrosis progression is not yet fully understood.
Enter MIPSS70. A relatively new MF prognostic scale, the MIPSS70 (Mutation-enhanced International Prognostic Scoring System) adds three new hazard factors to the DIPSS Plus scale : High Molecular Risk mutations, the absence of CALR Type 1 mutation, and the impact of bone marrow fibrosis levels. By incorporating genetic, cytogenetic and clinical information in a single scale MIPSS70 may improve the accuracy of stem cell transplant timing.
While the MIPSS70 scale is gaining increased acceptance, particularly in Europe, current expert opinion awaits further validation before the scale can be reliably used on its own to predict the timing of stem cell transplant.
With the current upgrade, The SSTT (SCT Spectrum Timing Tool) now includes both the DIPSS and DIPSS Plus scales. The MS3T Taskforce continues to assess the MIPSS70 scale and other instruments for future inclusion in the tool.
As always, to help resolve questions of stem cell transplant timing on an individual molecular and clinical basis, patients need consult with their hematologist and transplant specialist.