Abstract: TH-PO603

Inhibition of PLK1 Delays Cyst Growth in Autosomal Dominant Polycystic Kidney Disease

Session Information

Category: Genetic Diseases of the Kidney

  • 801 Cystic Kidney Diseases

Authors

  • Zhou, Xia, University of Kansas Medical Center, Kansas City, Kansas, United States
  • Ma, Guangqiang, University of Kansas Medical Center, Kansas City, Kansas, United States
  • Li, Xiaoyan, University of Kansas Medical Center, Kansas City, Kansas, United States
  • Calvet, James P., University of Kansas Medical Center, Kansas City, Kansas, United States
  • Li, Xiaogang, University of Kansas Medical Center, Kansas City, Kansas, United States
Background

The G2/M DNA damage checkpoint serves to prevent the cell from entering mitosis with genomic DNA damage. G2-phase transition is dependent on the activity of the Cyclin B-cdc2 complex which is regulated by CDC25 phosphatases, CDC25B and CDC25C. Polo-Like Kinase 1 (PLK1) is a major kinase with pivotal roles in multiple aspects of cell division (mitosis) by activating CDC25. However, the roles of PLK1 and CDC25B/C in cystogenesis in ADPKD remain elusive.

Methods

To understand dysregulated signaling pathways in cystic kidneys, we performed RNA-seq and Ingenuity Pathway Analysis (IPA). To explore the roles of PLK1 and CDC25B in regulating cyst growth, we targeted PLK1 in Pkd1 mutant cells and mice with a PLK1 inhibitor volasertib.

Results

We found that DNA damage response was increased in Pkd1 mutant PN24 cells and kidneys of Pkd1flox/flox:Tamoxifen-Cre mice by phospho-H2AX staining. Our RNA-seq and IPA analysis indicated that the genes related to the cell cycle G2/M DNA damage checkpoint regulation pathway, including PLK1, CDC25B and CDC25C, were upregulated and activated in cystic kidneys compared to those in wild type kidneys. The upregulation of PLK1, CDC25B and CDC25C was confirmed by qRT-PCR, western blot and immunohistochemistry (IHC) staining in cystic kidneys versus controls. Treatment with the PLK1 inhibitor volasertib and the CDC25 inhibitor NSC663284 decreased cystic renal epithelial cell proliferation as examined by MTT assay. We also found that volasertib treatment increased the expression of p21, phospho-CDK2, active caspase 3, and cleaved PARP expression, and decreased the phosphorylation of ERK, S6 and Rb in PN24 cells. Furthermore, treatment with volasertib delayed cyst growth in Pkd1 conditional knockout mice. Volasertib treatment decreased cyst lining epithelial cell proliferation as examined by PCNA and Ki67 staining, decreased the phosphorylation of ERK, S6, STAT3 and Rb, but increased cyst lining epithelial cell apoptosis as examined by TUNEL assay in cystic kidneys.

Conclusion

The cell cycle G2/M DNA damage signaling pathway is dysregulated in ADPKD. Inhibition of PLK1 produces a potent anti-proliferative and pro-apoptotic effect, regulates the known PKD associated pathways in cystic renal epithelia, and delays cyst growth in vivo, which suggests that targeting PLK1 may be a potential therapeutic strategy for ADPKD treatment.

Funding

  • NIDDK Support