The heat shock protein-90 co-chaperone, Cyclophilin 40, promotes ALK-positive, anaplastic large cell lymphoma viability and its expression is regulated by the NPM-ALK oncoprotein.
BACKGROUND
Anaplastic lymphoma kinase-positive, anaplastic large cell lymphoma (ALK+ ALCL) is a T cell lymphoma defined by the presence of chromosomal translocations involving the ALK tyrosine kinase gene. These translocations generate fusion proteins (e.g. NPM-ALK) with constitutive tyrosine kinase activity, which activate numerous signalling pathways important for ALK+ ALCL pathogenesis. The molecular chaperone heat shock protein-90 (Hsp90) plays a critical role in allowing NPM-ALK and other signalling proteins to function in this lymphoma. Co-chaperone proteins are important for helping Hsp90 fold proteins and for directing Hsp90 to specific clients; however the importance of co-chaperone proteins in ALK+ ALCL has not been investigated. Our preliminary findings suggested that expression of the immunophilin co-chaperone, Cyclophilin 40 (Cyp40), is up-regulated in ALK+ ALCL by JunB, a transcription factor activated by NPM-ALK signalling. In this study we examined the regulation of the immunophilin family of co-chaperones by NPM-ALK and JunB, and investigated whether the immunophilin co-chaperones promote the viability of ALK+ ALCL cell lines.


METHODS
NPM-ALK and JunB were knocked-down in ALK+ ALCL cell lines with siRNA, and the effect on the expression of the three immunophilin co-chaperones: Cyp40, FK506-binding protein (FKBP) 51, and FKBP52 examined. Furthermore, the effect of knock-down of the immunophilin co-chaperones, either individually or in combination, on the viability of ALK+ ALCL cell lines and NPM-ALK levels and activity was also examined.


RESULTS
We found that NPM-ALK promoted the transcription of Cyp40 and FKBP52, but only Cyp40 transcription was promoted by JunB. We also observed reduced viability of ALK+ ALCL cell lines treated with Cyp40 siRNA, but not with siRNAs directed against FKBP52 or FKBP51. Finally, we demonstrate that the decrease in the viability of ALK+ ALCL cell lines treated with Cyp40 siRNA does not appear to be due to a decrease in NPM-ALK levels or the ability of this oncoprotein to signal.


CONCLUSIONS
This is the first study demonstrating that the expression of immunophilin family co-chaperones is promoted by an oncogenic tyrosine kinase. Moreover, this is the first report establishing an important role for Cyp40 in lymphoma.
Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Canada.
Joel D
JD
Pearson
Zubair
Z
Mohammed
Julinor T C
JT
Bacani
Raymond
R
Lai
Robert J
RJ
Ingham
D000077548:Anaplastic Lymphoma Kinase; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D017728:Lymphoma, Large-Cell, Anaplastic / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D022021:Tacrolimus Binding Proteins / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014443:Tyrosine / Q000378:metabolism; D000099159:Tacrolimus Binding Protein 5
D000077548:Anaplastic Lymphoma Kinase; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins; D018841:HSP90 Heat-Shock Proteins; D011505:Protein-Tyrosine Kinases; D016755:Proto-Oncogene Proteins c-jun; D020794:Receptor Protein-Tyrosine Kinases; D022021:Tacrolimus Binding Proteins; D014443:Tyrosine; D000099159:Tacrolimus Binding Protein 5; C107023:p80(NPM-ALK) protein; C000626173:ALK protein, human; C403485:tacrolimus binding protein 4