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Open Access Research article

Expression, regulation and function of phosphofructo-kinase/fructose-biphosphatases (PFKFBs) in glucocorticoid-induced apoptosis of acute lymphoblastic leukemia cells

Michela Carlet17, Kristina Janjetovic17, Johannes Rainer127, Stefan Schmidt237, Renate Panzer-Grümayer47, Georg Mann47, Martina Prelog57, Bernhard Meister67, Christian Ploner17* and Reinhard Kofler127

Author Affiliations

1 Division Molecular Pathophysiology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria

2 Tyrolean Cancer Research Institute, Innsbruck, 6020-Austria

3 Department of Hematology and Oncology, Medical University of Innsbruck, Innsbruck, Austria

4 Children's Cancer Research Institute and St. Anna Kinderspital, Vienna, Austria

5 Department of Pediatrics I, Medical University of Innsbruck, Innsbruck, Austria

6 Department of Pediatrics II, Medical University of Innsbruck, Innsbruck, Austria

7 Institute of Legal Medicine, Medical University Innsbruck, Innsbruck, Austria

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BMC Cancer 2010, 10:638  doi:10.1186/1471-2407-10-638

Published: 23 November 2010

Abstract

Background

Glucocorticoids (GCs) cause apoptosis and cell cycle arrest in lymphoid cells and constitute a central component in the therapy of lymphoid malignancies, most notably childhood acute lymphoblastic leukemia (ALL). PFKFB2 (6-phosphofructo-2-kinase/fructose-2,6-biphosphatase-2), a kinase controlling glucose metabolism, was identified by us previously as a GC response gene in expression profiling analyses performed in children with ALL during initial systemic GC mono-therapy. Since deregulation of glucose metabolism has been implicated in apoptosis induction, this gene and its relatives, PFKFB1, 3, and 4, were further analyzed.

Methods

Gene expression analyses of isolated lymphoblasts were performed on Affymetrix HGU133 Plus 2.0 microarrays. GCRMA normalized microarray data were analyzed using R-Bioconductor packages version 2.5. Functional gene analyses of PFKFB2-15A and -15B isoforms were performed by conditional gene over-expression experiments in the GC-sensitive T-ALL model CCRF-CEM.

Results

Expression analyses in additional ALL children, non-leukemic individuals and leukemic cell lines confirmed frequent PFKFB2 induction by GC in most systems sensitive to GC-induced apoptosis, particularly T-ALL cells. The 3 other family members, in contrast, were either absent or only weakly expressed (PFKFB1 and 4) or not induced by GC (PFKFB3). Conditional PFKFB2 over-expression in the CCRF-CEM T-ALL in vitro model revealed that its 2 splice variants (PFKFB2-15A and PFKFB2-15B) had no detectable effect on cell survival. Moreover, neither PFKFB2 splice variant significantly affected sensitivity to, or kinetics of, GC-induced apoptosis.

Conclusions

Our data suggest that, at least in the model system investigated, PFKFB2 is not an essential upstream regulator of the anti-leukemic effects of GC.