title: Expression, regulation and function of phosphofructo-kinase/fructose-biphosphatases (PFKFBs) in glucocorticoid-induced apoptosis of acute lymphoblastic leukemia cells.
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.
authors.affiliation: Division Molecular Pathophysiology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Michela
authors.initials: M
authors.lastname: Carlet
authors.forename: Kristina
authors.initials: K
authors.lastname: Janjetovic
authors.forename: Johannes
authors.initials: J
authors.lastname: Rainer
authors.forename: Stefan
authors.initials: S
authors.lastname: Schmidt
authors.forename: Renate
authors.initials: R
authors.lastname: Panzer-Grümayer
authors.forename: Georg
authors.initials: G
authors.lastname: Mann
authors.forename: Martina
authors.initials: M
authors.lastname: Prelog
authors.forename: Bernhard
authors.initials: B
authors.lastname: Meister
authors.forename: Christian
authors.initials: C
authors.lastname: Ploner
authors.forename: Reinhard
authors.initials: R
authors.lastname: Kofler
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D002470:Cell Survival; D002648:Child; D003907:Dexamethasone / Q000627:therapeutic use*; D004318:Doxycycline / Q000494:pharmacology; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D005938:Glucocorticoids / Q000627:therapeutic use*; D006801:Humans; D019169:Jurkat Cells; D008214:Lymphocytes / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D025481:Phosphofructokinase-2 / Q000235:genetics / Q000378:metabolism*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D051381:Rats; D013997:Time Factors; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D005938:Glucocorticoids; C506672:PFKFB4 protein, human; D003907:Dexamethasone; C555744:PFKFB2 protein, human; C107345:PFKFB3 protein, human; D025481:Phosphofructokinase-2; D004318:Doxycycline