Development of t(8;21) and RUNX1-RUNX1T1 in the Philadelphia-positive clone of a patient with chronic myelogenous leukemia: additional evidence for multiple steps involved in disease progression.

A 65-year-old patient with a high hemoglobin and hematocrit was treated for 14 months with therapeutic phlebotomy when cytogenetics of bone marrow revealed 100% cells with the Ph chromosome and 45% of the Ph+ cells contained trisomy 8. Treatment with tyrosine kinase inhibitors did not reduce the BCR-ABL1 fusion positive clone. Instead, the Ph positive cells acquired further the t(8;21)/RUNX1-RUNX1T1, del(4q) and trisomy 15 chromosomal abnormalities which were resistant to further treatment. Literature review revealed eight other patients who either had t(9;22) and t(8;21) simultaneously or developed t(8;21) in the Ph positive clone. We conclude that there are rare patients with CML who either present in blast crisis with coexistence of t(9;22) and t(8;21) with or without +8, or progress to blast crisis with acquiring RUNX1-RUNX1T1 in the BCR-ABL1 clone which may or may not be therapy related and represent a later event in a multistep pathogenesis.

Clonal analyses define the relationships between chromosomal abnormalities and JAK2V617F in patients with Ph-negative myeloproliferative neoplasms.

OBJECTIVE: JAK2V617F occurs in approximately 93% of patients with polycythemia vera and approximately 50% of patients with either primary myelofibrosis or essential thrombocythemia. Chromosomal abnormalities are detected in 50% of patients with primary myelofibrosis, 29% with polycythemia vera, and 8% to 10% with essential thrombocythemia. The relationship between the presence of such chromosomal abnormalities and the JAK2V617 allele burden, and the role that each of these genetic events play in the origins and progression of the myeloproliferative neoplasms (MPNs), remain unclear. MATERIALS AND METHODS: Individual hematopoietic colonies were assayed in vitro from the CD34(+) cells of six JAK2V617F-positive MPN patients with marker chromosomal abnormalities. Colonies were simultaneously analyzed for JAK2 genotype and chromosomal abnormalities. RESULTS: Among the 248 colonies assayed from cultures containing 500 CD34(+) cells, chromosomal abnormalities were detected in 5% of colonies with wild-type JAK2, 32% of JAK2V617F heterozygous colonies and 56% of JAK2V617F homozygous colonies. Overall, 92% of chromosomally abnormal colonies were also JAK2V617F homozygous. Although 54 colonies contained wild-type JAK2 exclusively, 4 of these colonies were characterized by chromosomal abnormalities. CONCLUSION: This study indicates that MPN hematopoietic progenitor cells do not necessarily always acquire genetic events in the same sequence. (Chromosomally abnormal progenitor cells are closely associated with JAK2V617F homozygosity; p=0.0001.). Chromosomal abnormalities such as +8, +9 can occasionally precede acquisition of JAK2V617F. These findings support the existence of earlier genetic events that precede JAK2V617F or cytogenetic abnormalities in MPN hematopoietic progenitor cells.

Pivotal role of mast cells in pruritogenesis in patients with myeloproliferative disorders.

Pruritus is a common symptom in patients with Philadelphia chromosome-negative myeloproliferative disorders (MPDs). The pathophysiology of MPD-associated pruritus is unclear. We have demonstrated that MPD mast cells (MCs) are involved by the malignant process. In the present study, we explored the hypothesis that MCs play an important role in the development of pruritogenesis in MPDs. We found that MPD MCs released significantly greater amounts of pruritogenic factors, including histamine, leukotrienes, and interleukin-31 (IL-31) than normal MCs. Elevated levels of IL-31 were also observed in MPD CD3(+) cell-conditioned media. MPD MCs exhibited increased migratory behavior in response to stem cell factor or interleukin-8, which was associated with increased filamentous-actin content. Furthermore, the presence of pruritus in MPDs was statistically correlated with a greater number of MCs being generated by CD34(+) cells, a greater number of MC colonies being formed by CD34(+) cells, decreased apoptosis and prostaglandin D(2) release by cultured MCs, and higher plasma levels of IL-31. These data demonstrate that functional abnormalities of MPD MCs probably lead to pruritogenesis in patients with MPDs. These studies provide cellular and molecular targets for the development of antipruritus drugs for patients with MPDs.

Circulating angiogenic monocyte progenitor cells are reduced in JAK2V617F high allele burden myeloproliferative disorders.

The clinical course of patients with Philadelphia chromosome negative myeloproliferative disorder is frequently complicated by thrombotic events. Post-natal vasculogenesis has been proposed to play a critical role in angiogenesis by acting through a hierarchy of endothelial progenitor cells. Some endothelial progenitor cells have been shown to share a number of features associated with monocytes while other more primitive progenitor cells produce endothelial cells in vitro exclusively. The cells which share features of monocytes and endothelial cells have been termed angiogenic monocytes. Reduced levels of angiogenic monocyte progenitor cells have been reported to be predictive of atherosclerotic disease progression. Angiogenic monocyte progenitor cells were assayed in vitro from the peripheral blood mononuclear cells of myeloproliferative disorder patients. Angiogenic monocyte colonies were plucked and analyzed for endothelial cells and hematopoietic cell markers, JAK2V617F and their ability to incorporate into vascular endothelium following their transplantation into non-obese diabetic, severe combine immunodeficient mice. Myeloproliferative disorder angiogenic monocyte colonies that were detected were uniformly JAK2V617F positive and produced cells that expressed phenotypic markers characteristic of both monocytes and endothelial cells. Reduced numbers of angiogenic monocyte colonies were present in the blood of myeloproliferative disorder patients with a high JAK2V617F burden (>50%), (p<0.01). Transplanted angiogenic monocytes were able to contribute to the vascular endothelium of non-obese diabetic, severe combine immunodeficient mice. These studies suggest that reduced numbers of circulating angiogenic monocyte progenitors contribute to the propensity to develop thrombotic complications in myeloproliferative disorder patients.