title: [Assessment of P70S6 kinase phosphorylation after liver transplantation by phospho-flow cytometry].
abstract: OBJECTIVE
  To explore the role of P70S6 kinase phosphorylation as a downstream of mammalian target of rapamycin (mTOR) pathway in CD3 positive cells of liver transplant patients.
  
  
  METHODS
  A total of 84 liver transplant recipients were recruited from our hospital and divided into 3 treatment groups of sirolimus (n = 26), tacrolimus (n = 35) and cyclosporine (n = 23). The P70S6 kinase phosphorylation of CD3 positive cell of patients and healthy control (HC) were analyzed by phospho-flow cytometry. A correlation analysis between P70S6 kinase phosphorylation and sirolimus trough level was performed. Intra-individual variability and inter-individual variability of P70S6 kinase phosphorylation were measured.
  
  
  RESULTS
  The P70S6 kinase phosphorylation in HC showed a low degree of intra-individual variability (3.5% to 5.6%) while the inter-individual variability between different healthy volunteers was higher (18.9% to 22.5%). The P70S6 kinase phosphorylation in patients treated with sirolimus (28.9 ± 10.5) was significantly lower than in HC (57.2 ± 8.4, P < 0.001), tacrolimus (42.5 ± 14.1, P < 0.001) or cyclosporine treated ones (51.4 ± 10.9, P < 0.001). The P70S6 kinase phosphorylation in HC (57.2 ± 8.4) was significantly higher than in tacrolimus (42.5 ± 14.1, P < 0.01) or cyclosporine treated patients (51.4 ± 10.9, P < 0.05). No correlation existed between P70S6 kinase phosphorylation and trough level of sirolimus (r = -0.18, P = 0.39).
  
  
  CONCLUSIONS
  Phospho-flow cytometry assay has been established for determining the degree of mTOR inhibition by assessing P70S6 kinase phosphorylation. Quantification of P70S6 kinase phosphorylation may play an adjunct role in pharmacodynamically guiding an individualized mTOR inhibitor based immunosuppression.
authors.affiliation: Department of Emergency Medicine, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, China.
authors.forename: Junyu
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Hepatobiliary Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, China. Email: fanhua@medmail.com.cn.
authors.forename: Hua
authors.initials: H
authors.lastname: Fan
mesh_terms: D016572:Cyclosporine; D005434:Flow Cytometry; D006801:Humans; D016031:Liver Transplantation; D010766:Phosphorylation; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; D016559:Tacrolimus
chemical_list: D016572:Cyclosporine; C546842:MTOR protein, human; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus; D016559:Tacrolimus