Cyclosporine induces the expression of the cyclin inhibitor p21.
BACKGROUND
Current immunosuppression strategies involve inhibition of T cell activation and/or lymphocyte proliferation. During T cell cycle progression/activation, the expression of cyclins and cyclin dependent kinases is increased. In this study, we examined whether cyclosporine A (CsA) suppresses the cell cycle progression through the induction of the cell cycle inhibitor p21. Because CsA induces the expression of transforming growth factor (TGF)-beta, and TGF-beta induces p21 expression, we also determined whether CsA's induction of p21 is dependent on or independent of TGF-beta.


METHODS
Using reverse transcription assisted polymerase chain reaction and western blot analysis, we studied the induction of p21 mRNA and protein in human T cells and A-549 cells (human lung adenocarcinoma cells) by CsA. The stimulation of p21 promoter activity was studied by luciferase assay using p21-luc, chimeric plasmid DNA containing a p21 promoter segment, and luciferase reporter gene. The dependence of CsA's induction of p21 was studied using anti-TGF-beta antibody and TGF-beta altered A-549 cells.


RESULTS
CsA induced p21 mRNA protein expression and stimulated its promoter activity in lymphoid (T cells) and nonlymphoid (human lung adenocarcinoma, A-549 cells).CsA's induction of p21 was inhibited both by a neutralizing anti-TGF-beta antibody and in TGF-beta-altered A-549 cells, consistent with its effects on p21 requiring TGF-beta.


CONCLUSIONS
These data support the hypothesis that at least one component of CsA's antiproliferative effects may occur through the induction of p21 and that this induction is dependent on TGF-beta. Should p21 induction be a viable immunosuppressive strategy, inducing this molecule independent from the fibrogenic cytokine TGF-beta might reduce the toxicity associated with current immunosuppression.
Khanna
A K
AK
Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee 53226, USA. akkhanna@mcw.edu
Hosenpud
J D
JD
D000230:Adenocarcinoma / Q000378:metabolism; D000906:Antibodies / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D016213:Cyclins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis* / Q000235:genetics; D016572:Cyclosporine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000502:physiology; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000906:Antibodies; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D007166:Immunosuppressive Agents; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D016572:Cyclosporine; D018844:Cyclin-Dependent Kinases