| Reference | 1. Cell Mol Life Sci. 2017 Oct 25. doi: 10.1007/s00018-017-2681-z. [Epub ahead of
print]
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Protein kinase D inhibitor CRT0066101 suppresses bladder cancer growth in vitro
and xenografts via blockade of the cell cycle at G2/M.
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Li QQ(1), Hsu I(2), Sanford T(2), Railkar R(2), Balaji N(2), Sourbier C(2), Vocke
C(2), Balaji KC(3), Agarwal PK(4).
<br>
Author information: <br>
(1)Urologic Oncology Branch, Center for Cancer Research, National Cancer
Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
[email protected].
(2)Urologic Oncology Branch, Center for Cancer Research, National Cancer
Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
(3)Wake Forest University School of Medicine, Winston Salem, NC, 27106, USA.
(4)Urologic Oncology Branch, Center for Cancer Research, National Cancer
Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
[email protected].
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The protein kinase D (PKD) family of proteins are important regulators of tumor
growth, development, and progression. CRT0066101, an inhibitor of PKD, has
antitumor activity in multiple types of carcinomas. However, the effect and
mechanism of CRT0066101 in bladder cancer are not understood. In the present
study, we show that CRT0066101 suppressed the proliferation and migration of four
bladder cancer cell lines in vitro. We also demonstrate that CRT0066101 blocked
tumor growth in a mouse flank xenograft model of bladder cancer. To further
assess the role of PKD in bladder carcinoma, we examined the three PKD isoforms
and found that PKD2 was highly expressed in eight bladder cancer cell lines and
in urothelial carcinoma tissues from the TCGA database, and that short hairpin
RNA (shRNA)-mediated knockdown of PKD2 dramatically reduced bladder cancer growth
and invasion in vitro and in vivo, suggesting that the effect of the compound in
bladder cancer is mediated through inhibition of PKD2. This notion was
corroborated by demonstrating that the levels of phospho-PKD2 were markedly
decreased in CRT0066101-treated bladder tumor explants. Furthermore, our cell
cycle analysis by flow cytometry revealed that CRT0066101 treatment or PKD2
silencing arrested bladder cancer cells at the G2/M phase, the arrest being
accompanied by decreases in the levels of cyclin B1, CDK1 and phospho-CDK1
(Thr161) and increases in the levels of p27Kip1 and phospho-CDK1 (Thr14/Tyr15).
Moreover, CRT0066101 downregulated the expression of Cdc25C, which
dephosphorylates/activates CDK1, but enhanced the activity of the checkpoint
kinase Chk1, which inhibits CDK1 by phosphorylating/inactivating Cdc25C. Finally,
CRT0066101 was found to elevate the levels of Myt1, Wee1, phospho-Cdc25C
(Ser216), Gadd45α, and 14-3-3 proteins, all of which reduce the CDK1-cyclin B1
complex activity. These novel findings suggest that CRT0066101 suppresses bladder
cancer growth by inhibiting PKD2 through induction of G2/M cell cycle arrest,
leading to the blockade of cell cycle progression.
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2. Mol Cancer Ther. 2015 Jun;14(6):1306-16. doi: 10.1158/1535-7163.MCT-14-0945. Epub
2015 Apr 7.
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Effective Targeting of Estrogen Receptor-Negative Breast Cancers with the Protein
Kinase D Inhibitor CRT0066101.
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Borges S(1), Perez EA(2), Thompson EA(1), Radisky DC(1), Geiger XJ(3), Storz
P(4).
<br>
Author information: <br>
(1)Department of Cancer Biology, Mayo Clinic, Jacksonville, Florida.
(2)Department of Cancer Biology, Mayo Clinic, Jacksonville, Florida. Department
of Hematology/Oncology, Mayo Clinic, Jacksonville, Florida.
(3)Laboratory Medicine and Pathology, Mayo Clinic, Jacksonville, Florida.
(4)Department of Cancer Biology, Mayo Clinic, Jacksonville, Florida.
[email protected].
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Invasive ductal carcinomas (IDC) of the breast are associated with altered
expression of hormone receptors (HR), amplification or overexpression of HER2, or
a triple-negative phenotype. The most aggressive cases of IDC are characterized
by a high proliferation rate, a great propensity to metastasize, and their
ability to resist to standard chemotherapy, hormone therapy, or HER2-targeted
therapy. Using progression tissue microarrays, we here demonstrate that the
serine/threonine kinase protein kinase D3 (PKD3) is highly upregulated in
estrogen receptor (ER)-negative (ER(-)) tumors. We identify direct binding of the
ER to the PRKD3 gene promoter as a mechanism of inhibition of PKD3 expression.
Loss of ER results in upregulation of PKD3, leading to all hallmarks of
aggressive IDC, including increased cell proliferation, migration, and invasion.
This identifies ER(-) breast cancers as ideal for treatment with the PKD
inhibitor CRT0066101. We show that similar to a knockdown of PKD3, treatment with
this inhibitor targets all tumorigenic processes in vitro and decreases growth of
primary tumors and metastasis in vivo. Our data strongly support the development
of PKD inhibitors for clinical use for ER(-) breast cancers, including the
triple-negative phenotype.
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