Induction of the plasminogen activator inhibitor-2 in cells expressing the ZNF198/FGFR1 fusion kinase that is involved in atypical myeloproliferative disease

The ZNF198/FGFR1 fusion kinase associated with an atypical myeloproliferative disease is constitutively activated and regulates several STAT transcription factors. We used oligonucleotide microarrays to compare the gene-expression profiles between HEK-293 cells that stably express either the ZNF198/FGFR1 chimeric protein or the wild-type ZNF198 gene. Expression of the plasminogen activator inhibitor-2 (PAI-2/SERPINB2) was highly increased in cells expressing the fusion gene. Western blot analysis demonstrated that HEK-293 cells do not express PAI-2 endogenously, but in ZNF198/FGFR1-expressing cells 2 molecular forms of PAI-2, which were 47 kDa and 32 kDa, were expressed intracellularly, and a 60-kDa form was secreted. Similarly, expression of ZNF198/FGFR1 in BaF/3 mouse hematopoietic cells also induced the expression of the PAI-2 protein. Immunoprecipitation analysis revealed that both intracellular forms of PAI-2 bind to the ZNF198/FGFR1 kinase. Treatment of HEK-293 and BaF/3 cells with TNF-alpha in the presence of cycloheximide, induced apoptosis in both cases. In contrast, HEK-293 and BaF/3 cells expressing ZNF198/FGFR1 were resistant to TNF-alpha-induced apoptosis. These observations suggest that expression of the ZNF198/FGFR1 fusion gene is associated with specific PAI-2-mediated resistance to apoptosis which may contribute to the highly malignant nature of leukemic cells carrying this fusion kinase gene.