Survey of the Human Pancreatic β-Cell G1/S Proteome Reveals a Potential Therapeutic Role for Cdk-6 and Cyclin D1 in Enhancing Human β-Cell Replication and Function In Vivo

  1. Nathalie Fiaschi-Taesch,
  2. Todd A. Bigatel,
  3. Brian Sicari,
  4. Karen K. Takane,
  5. Fatima Salim,
  6. Silvia Velazquez-Garcia,
  7. George Harb,
  8. Karen Selk,
  9. Irene Cozar-Castellano and
  10. Andrew F. Stewart
  1. Division of Endocrinology, The University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
  1. Corresponding author: Nathalie M. Fiaschi-Taesch, taeschn{at}
  1. N.F.-T. and T.A.B. contributed equally to this article.


OBJECTIVES To comprehensively inventory the proteins that control the G1/S cell cycle checkpoint in the human islet and compare them with those in the murine islet, to determine whether these might therapeutically enhance human β-cell replication, to determine whether human β-cell replication can be demonstrated in an in vivo model, and to enhance human β-cell function in vivo.

RESEARCH DESIGN AND METHODS Thirty-four G1/S regulatory proteins were examined in human islets. Effects of adenoviruses expressing cdk-6, cdk-4, and cyclin D1 on proliferation in human β-cells were studied in both invitro and in vivo models.

RESULTS Multiple differences between murine and human islets occur, most strikingly the presence of cdk-6 in human β-cells versus its low abundance in the murine islet. Cdk-6 and cyclin D1 in vitro led to marked activation of retinoblastoma protein phosphorylation and cell cycle progression with no induction of cell death. Human islets transduced with cdk-6 and cyclin D1 were transplanted into diabetic NOD-SCID mice and markedly outperformed native human islets in vivo, maintaining glucose control for the entire 6 weeks of the study.

CONCLUSIONS The human G1/S proteome is described for the first time. Human islets are unlike their rodent counterparts in that they contain easily measurable cdk-6. Cdk-6 overexpression, alone or in combination with cyclin D1, strikingly stimulates human β-cell replication, both in vitro as well as in vivo, without inducing cell death or loss of function. Using this model, human β-cell replication can be induced and studied in vivo.


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    • Received May 12, 2008.
    • Accepted December 23, 2008.
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