Faculty Bibliography

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

Inflammatory breast cancer (IBC) is the most lethal form of primary breast cancer. IBC lethality derives from generation of tumour emboli, which are non-adherent cell clusters that rapidly spread by a form of continuous invasion known as passive metastasis. In most cancers, expression of E-cadherin, an epithelial marker, is indicative of low metastatic potential. In IBC, E-cadherin is overexpressed and supports formation of tumour emboli by promoting tumour cell interactions rather than adherence to stroma. E-cadherin, a surface component of adherens junctions, is anchored by interaction with p120 catenin (p120). We show that the unique pathogenic properties of IBC result in part from overexpression of the translation initiation factor eIF4GI in most IBCs. eIF4GI reprograms the protein synthetic machinery for increased translation of mRNAs with internal ribosome entry sites (IRESs) that promote IBC tumour cell survival and formation of tumour emboli. Overexpression of eIF4GI promotes formation of IBC tumour emboli by enhancing translation of IRES-containing p120 mRNAs. These findings provide a new understanding of translational control in the development of advanced breast cancer