Aberrant expression of PDZ-binding kinase/T-LAK cell-originated protein kinase modulates the invasive ability of human pancreatic cancer cells via the stabilization of oncoprotein c-MYC

High frequency of mortality in patients with pancreatic ductal adenocarcinoma (PDAC) is vastly associated with the invasive and metastatic nature of these cancer cells. Little is known about the factors involved in this invasive/metastatic process. The current challenge in the treatment of these patients is the lack of viable options besides gemcitabine. The aim of this study was to evaluate the role of PDZ-binding kinase (PBK)/T-LAK cell-originated protein kinase (TOPK) in invasive PDAC cells and to determine whether PBK/TOPK expression drives invasiveness in PDAC. Using gain-of-function and loss-of-function studies in established and patient-derived xenograft-PDAC cell lines, and examining patient-derived archival tissue samples, we demonstrate for the first time that PBK/TOPK is upregulated in pancreatic cancer and expression levels are closely associated with the invasive property of pancreatic cancer cells. Modulation of PBK/TOPK causally regulates the invasive ability of PDAC cells. We also demonstrate that two key players in metastatic invasion, matrix metalloproteinases-2 (MMP-2) and MMP-9 gelatinase activity and gene promoter activities, are regulated by PBK/TOPK. Moreover, we demonstrate for the first time that PBK/TOPK provides stability of an oncoprotein, c-MYC, which transcriptionally regulates MMP-2 and MMP-9 in these invasive PDAC cells. Our in vitro and in situ data corroborate that PBK/TOPK is closely associated with the invasive nature of PDAC and reveal a novel mechanism by which the metastatic behavior of human pancreatic cancer cells is regulated. These findings provide a rationale for targeting PBK/TOPK for the therapeutic intervention of invasive/metastatic pancreatic cancer in human.

PBK/TOPK enhances aggressive phenotype in prostate cancer via β-catenin-TCF/LEF-mediated matrix metalloproteinases production and invasion

A Current challenge in prostate cancer treatment is how to differentiate aggressive disease from indolent prostate cancer. There is an urgent need to identify markers that would accurately distinguish indolent prostate cancer from aggressive disease. The aim of this study was to evaluate the role of PDZ Domain-binding kinase (PBK) in prostate cancer and to determine if PBK expression enhances aggressiveness in prostate cancer. Using archival tissue samples, gain-of-function and loss-of-function studies, we show that PBK expression is up-regulated in prostate cancer, and its expression level is commensurate with invasiveness. Modulation of PBK expression and function causally regulates the invasive ability of prostate cancer cells. Production of matrix metalloproteinases-2 and -9, which are key players in metastatic invasion, is up-regulated, and the promoters of these genes are transcriptionally activated by PBK via increased β-catenin-TCF/LEF signaling. Prostate cancer tissue specimens show that PBK's expression correlates with aggressive disease and distant metastasis in bone, lymph node and abdomen. Our in vitro and in situ data are in agreement that PBK could be a prognostic biomarker for prostate cancer that would discriminate aggressive prostate cancer from indolent disease, and is a potential target for the therapeutic intervention of aggressive prostate cancer in men.

Gadd45 in stress signaling, cell cycle control, and apoptosis

The first identified Gadd45 gene, Gadd45a, encodes a ubiquitously expressed protein that is often induced by DNA damage and other stress signals associated with growth arrest and apoptosis. This protein and the other two members of this small gene family, Gadd45b and Gadd45g, have been implicated in a variety of the responses to cell injury including cell cycle checkpoints, apoptosis, and DNA repair. In vivo, many of the prominent roles for the Gadd45 proteins are associated with signaling mediated by p38 mitogen-activated protein kinases (MAPK). Gadd45 proteins can contribute to p38 activation either by activation of upstream kinase(s) or by direct interaction. In vivo, there are important tissue and cell-type-specific differences in the roles for Gadd45 in MAPK signaling. In addition to being p53-regulated, Gadd45a has been found to contribute to p53 activation via p38. Like other stress and signaling proteins, Gadd45 proteins show complex regulation and numerous effectors.

Abstract 4935: PDZ–domain binding kinase promotes invasion in prostate cancer cells through up–regulation of matrix metalloproteinases–2 and –9

Members of the protein kinase superfamily of enzymes modulate many of the facets of the tumor phenotype, such as survival, proliferation, invasion and metastasis. Genetic, epigenetic or regulatory alterations can result in aberrant kinase behavior; the targeted inhibition of which has been a growing focus in anti-cancer drug development. PDZ-domain binding kinase (PBK) is an under-studied, dual-specificity serine/threonine kinase that has been shown to play a key role in cell division and regulation of multiple signaling pathways. It is expressed physiologically in spermatogenic germ and proliferating neural precursor cells, as well as aberrantly in a variety of cancer types. However, the role of PBK in prostate cancer has not been clearly defined. We have found that PBK expression varies greatly across a panel of human prostate cancer cell lines. Interestingly, the level of expression of PBK in prostate cancer cells directly correlates with their invasive ability. Since matrix metalloproteinases (MMP) -2 and -9 are key invasive effectors in a variety of cancers, we investigated their protein levels in relation to that of PBK. Expression of exogenous PBK in low PBK-expressing prostate cancer cell lines (LNCaP and VCaP) significantly upregulated levels of both the propeptide and active forms of MMP-2 and MMP-9; conversely, knockdown of PBK expression in a high PBK-expressing prostate cancer cell line (PC3M) significantly down-regulated both forms of these two MMPs. To determine if a change in PBK levels produces a significant phenotypic effect, we measured the effect of PBK overexpression or knockdown on the prostate cancer cell lines’ invasive ability, as measured in a modified Boyden chamber invasion assay. Overexpression of PBK increased prostate cancer cell invasion approximately ten fold, while PBK knockdown reduced PC3M invasive ability more than three fold. Moreover, immunohistochemical analysis revealed that PBK is present in the majority of human prostate cancer samples tested but not at all in the benign or normal human prostate tissue. These data indicate a novel function of PBK where its presence plays a role in invasion of human prostate cancer cells through up-regulation of MMP-2 and MMP-9. Therefore, the role of PBK in promoting cell invasion, combined with its general lack of expression in normal cells, nominates PBK as a potentially important therapeutic target for prostate cancer.

Citation Format: Joshua D. Brown-Clay, Deepika N. Shenoy, Partha P. Banerjee. PDZ–domain binding kinase promotes invasion in prostate cancer cells through up–regulation of matrix metalloproteinases–2 and –9. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4935. doi:10.1158/1538-7445.AM2013-4935

Design, synthesis, and in vitro evaluation of potential West Nile virus protease inhibitors based on the 1-oxo-1,2,3,4-tetrahydroisoquinoline and 1-oxo-1,2-dihydroisoquinoline scaffolds

The 1-oxo-1, 2, 3, 4-tetrahydroisoquinoline and 1-Oxo-1, 2-dihydroisoquinoline scaffolds were utilized in the design and solution phase synthesis of focused libraries of compounds for screening against West Nile Virus (WNV) protease. Exploratory studies have led to the identification of a WNV protease inhibitor (a 1-oxo-1, 2-dihydroisoquinoline-based derivative, 12j) which could potentially serve as a launching pad for a hit-to-lead optimization campaign. The identified hit was devoid of any inhibitory activity toward a panel of mammalian serine proteases.