A Novel Small-Molecule Inhibitor of Protein Kinase D Blocks Pancreatic Cancer GrowthIn vitroandIn vivo

Abstract

Protein kinase D (PKD) family members are increasingly implicated in multiple normal and abnormal biological functions, including signaling pathways that promote mitogenesis in pancreatic cancer. However, nothing is known about the effects of targeting PKD in pancreatic cancer. Our PKD inhibitor discovery program identified CRT0066101 as a specific inhibitor of all PKD isoforms. The aim of our study was to determine the effects of CRT0066101 in pancreatic cancer. Initially, we showed that autophosphorylated PKD1 and PKD2 (activated PKD1/2) are significantly upregulated in pancreatic cancer and that PKD1/2 are expressed in multiple pancreatic cancer cell lines. Using Panc-1 as a model system, we showed that CRT0066101 reduced bromodeoxyuridine incorporation; increased apoptosis; blocked neurotensin-induced PKD1/2 activation; reduced neurotensin-induced, PKD-mediated Hsp27 phosphorylation; attenuated PKD1-mediated NF-κB activation; and abrogated the expression of NF-κB-dependent proliferative and prosurvival proteins. We showed that CRT0066101 given orally (80 mg/kg/d) for 24 days significantly abrogated pancreatic cancer growth in Panc-1 subcutaneous xenograft model. Activated PKD1/2 expression in the treated tumor explants was significantly inhibited with peak tumor concentration (12 μmol/L) of CRT0066101 achieved within 2 hours after oral administration. Further, we showed that CRT0066101 given orally (80 mg/kg/d) for 21 days in Panc-1 orthotopic model potently blocked tumor growth in vivo. CRT0066101 significantly reduced Ki-67-positive proliferation index (P < 0.01), increased terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive apoptotic cells (P < 0.05), and abrogated the expression of NF-κB-dependent proteins including cyclin D1, survivin, and cIAP-1. Our results show for the first time that a PKD-specific small-molecule inhibitor CRT0066101 blocks pancreatic cancer growth in vivo and show that PKD is a novel therapeutic target in pancreatic cancer. Mol Cancer Ther; 9(5); 1136-46. ©2010 AACR.

Protein Kinase D1 Mediates Anchorage-dependent and -independent Growth of Tumor Cells via the Zinc Finger Transcription Factor Snail1

“…In conclusion, our data demonstrate that PKD1 enhances proliferation (10,36) of pancreatic and other cancer cells, and this regulation is mediated by Snail1 via phosphorylation at Ser-11. Snail1 is therefore required and sufficient for PKD1-driven proliferation and anchorage-independent growth of different tumor cells.…”

“…PKDs are involved in the regulation of important cellular features such as proliferation (10,11,13,(35)(36)(37), motility, and invasiveness (2-5) of different tumor types. However, specific and detailed functions for distinct PKD isoforms have not been addressed so far.…”

Protein kinase D in vascular biology and angiogenesis

“…PKD is therefore an attractive therapeutic target since anti-PKD therapy may not only impinge on tumor cell survival and proliferation directly, but also indirectly through its potential antiangiogenic effects on tumor vascularisation. This interest has stimulated the development of several specific PKD inhibitors [reviewed in (40)] and one such inhibitor, CRT0066101, inhibited pancreatic carcinoma (Panc-1) tumor growth in a mouse xenograft model (41). PKD inhibitors are currently still at a very early stage in development, and there are currently no inhibitors which display isoform specificity.…”

Spatiotemporally Distinct Protein Kinase D Activation in Adult Cardiomyocytes in Response to Phenylephrine and Endothelin

“…HDAC subtype-specific inhibition might be a way to resolve this benefit conflict, but targeting upstream of HDACs may hold unique benefits. Along these lines, cardiac-specific deletion of PKD1 (and CaMKII␦ knock-out) limit cardiac remodeling after aortic constriction (5, 22) and novel PKD inhibitors have had some success in the prevention of pathological hypertrophy (23-25) as well as of pancreatic and prostatic cancer growth (17,26). In the heart, a better mechanistic understanding of how cardiomyocyte PKD and CaMK are activated in response to pathogenic neurohumoral stimuli (5-6) is needed to evaluate the therapeutic potential of specific PKD/ CaMKII inhibition.…”