title: Activation status of the JAK/STAT3 pathway in mantle cell lymphoma.
abstract: BACKGROUND
  Signal transducer and activator of transcription 3 (STAT3) is oncogenic, and we previously found evidence of constitutive STAT3 activation in a relatively small number of frozen mantle cell lymphoma (MCL) cell tumors.
  
  
  OBJECTIVE
  To comprehensively survey the activation and phosphorylation status of STAT3 in MCL and to assess if STAT3 activation in these tumors is due to cytokine stimulation by examining the phosphorylation and activation status of Janus kinase (JAK), the physiologic activator of STAT3.
  
  
  METHODS
  We evaluated 43 formalin-fixed, paraffin-embedded MCL tumors using immunohistochemistry and phospho-specific antibodies against STAT3 and JAK.
  
  
  RESULTS
  There were 37 small cell and 6 blastoid cases. There was heterogeneous expression of phospho-STAT3 (pSTAT3), with 23 negative cases (53%), 12 weakly positive cases (28%), and 8 strongly positive cases (19%). JAK3 was the only member detectable in 3 MCL cell lines, and immunoprecipitation data showed a relatively low level of tyrosine phosphorylation of JAK3 in these cells. Using immunohistochemistry, phospho-JAK3 (pJAK3) was detectable in 18 (44%) of 41 MCL tumors examined, and pJAK3 expression correlated with that of pSTAT3 (P = .008). A notable exception to this correlation was seen in the blastoid variant, since 4 (67%) of 6 blastoid cases were pSTAT3 positive but pJAK3 negative.
  
  
  CONCLUSIONS
  We have confirmed our previous finding that STAT3 is constitutively activated in MCL tumors, with an overall frequency of 47% in this series. STAT3 activation in the small cell but not the blastoid variant of MCL is likely mediated by JAK3.
authors.affiliation: Department of Hematopathology, The University of Texas, M. D. Anderson Cancer Center, Houston, USA.
authors.forename: Marwan A
authors.initials: MA
authors.lastname: Yared
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Khoury
authors.forename: L Jeffrey
authors.initials: LJ
authors.lastname: Medeiros
authors.forename: George Z
authors.initials: GZ
authors.lastname: Rassidakis
authors.forename: Raymond
authors.initials: R
authors.lastname: Lai
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism; D045744:Cell Line, Tumor; D056741:Cyclin D; D016213:Cyclins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D053613:Janus Kinase 1; D020522:Lymphoma, Mantle-Cell / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010766:Phosphorylation; D040081:Protein Array Analysis; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D050796:STAT3 Transcription Factor; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D014408:Biomarkers, Tumor; D056741:Cyclin D; D016213:Cyclins; D004268:DNA-Binding Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; D053613:Janus Kinase 1