The metastasis suppressor, NDRG1, attenuates oncogenic TGF-ß and NF-κB signaling to enhance membrane E-cadherin expression in pancreatic cancer cells.

The metastasis suppressor, N-myc downstream-regulated gene-1 (NDRG1), plays multifaceted roles in inhibiting oncogenic signaling and can suppress the epithelial mesenchymal transition (EMT), a key step in metastasis. In this investigation, NDRG1 inhibited the oncogenic effects of transforming growth factor-ß (TGF-ß) in PANC-1 pancreatic cancer cells, promoting expression and co-localization of E-cadherin and ß-catenin at the cell membrane. A similar effect of NDRG1 at supporting E-cadherin and ß-catenin co-localization at the cell membrane was also demonstrated for HT-29 colon and CFPAC-1 pancreatic cancer cells. The increase in E-cadherin in PANC-1 cells in response to NDRG1 was mediated by the reduction of three transcriptional repressors of E-cadherin, namely SNAIL, SLUG and ZEB1. To dissect the mechanisms how NDRG1 inhibits nuclear SNAIL, SLUG and ZEB1, we assessed involvement of the nuclear factor-κB (NF-κB) pathway, as its aberrant activation contributes to the EMT. Interestingly, NDRG1 comprehensively inhibited oncogenic NF-κB signaling at multiple sites in this pathway, suppressing NEMO, Iĸĸα and IĸBα expression, as well as reducing the activating phosphorylation of Iĸĸα/ß and IĸBα. NDRG1 also reduced the levels, nuclear co-localization and DNA-binding activity of NF-κB p65. Further, Iĸĸα, which integrates NF-κB and TGF-ß signaling to upregulate ZEB1, SNAIL and SLUG, was identified as an NDRG1 target. Considering this, therapies targeting NDRG1 could be a new strategy to inhibit metastasis, and as such, we examined novel anticancer agents, namely di-2-pyridylketone thiosemicarbazones, which upregulate NDRG1. These agents downregulated SNAIL, SLUG and ZEB1 in vitro and in vivo using a PANC-1 tumor xenograft model, demonstrating their marked potential.

Novel Thiosemicarbazones Inhibit Lysine-Rich Carcinoembryonic Antigen-Related Cell Adhesion Molecule 1 (CEACAM1) Coisolated (LYRIC) and the LYRIC-Induced Epithelial-Mesenchymal Transition via Upregulation of N-Myc Downstream-Regulated Gene 1 (NDRG1).

Tumor necrosis factor α (TNFα) plays a vital role in cancer progression as it is associated with inflammation and promotion of cancer angiogenesis and metastasis. The effects of TNFα are mediated by its downstream target, the oncogene lysine-rich CEACAM1 coisolated protein (LYRIC, also known as metadherin or astrocyte elevated gene-1). LYRIC plays an important role in activating the nuclear factor-ĸB (NF-κB) signaling pathway, which controls multiple cellular processes, including proliferation, apoptosis, migration, etc. In contrast, the metastasis suppressor N-myc downstream regulated gene 1 (NDRG1) has the opposite effect on the NF-κB pathway, being able to inhibit NF-κB activation and reduce angiogenesis, proliferation, migration, and cancer cell invasion. These potent anticancer properties make NDRG1 an ideal therapeutic target. Indeed, a novel class of thiosemicarbazone anticancer agents that target this molecule has been developed; the lead agent, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone, has recently entered clinical trials for advanced and resistant cancers. To further elucidate the interaction between NDRG1 and oncogenic signaling, this study for the first time assessed the effects of NDRG1 on the tumorigenic properties of TNFα and its downstream target, LYRIC. We have demonstrated that NDRG1 inhibits the TNFα-mediated epithelial-to-mesenchymal transition. Further, NDRG1 also potently inhibited LYRIC expression, with a negative feedback loop existing between these two molecules. Examining the mechanism involved, we demonstrated that NDRG1 inhibited phosphatidylinositol 3-kinase/AKT signaling, leading to reduced levels of the LYRIC transcriptional activator, c-Myc. Finally, we demonstrated that novel thiosemicarbazones that upregulate NDRG1 also inhibit LYRIC expression, further highlighting their marked potential for cancer treatment.

Metals and metastasis: Exploiting the role of metals in cancer metastasis to develop novel anti-metastatic agents.

Metastasis is currently the leading cause of cancer related death and is the most feared and difficult to treat outcome for cancer patients. This complex process is regulated by a plethora of signaling pathways and molecules that control cell proliferation, invasion, motility and adhesion. Many of these vital processes that enable metastasis to occur are influenced by metals, which play crucial roles in the function of numerous proteins and enzymes. Importantly, an excess of essential metals such as iron and copper is often associated with carcinogenesis and metastatic disease. As such, metals have emerged as promising and viable therapeutic targets for a new generation of anti-cancer and anti-metastatic agents. Further, the unique properties of metals, including their abilities to redox cycle or to mimic other metals, can also be utilized to more effectively target aggressive and metastatic cancer cells. This review will provide an overview of the role that metals play in the metastatic progression of cancer and the development of novel therapies that either target or utilize metal ions as part of their mechanism of action to inhibit metastasis.

The renaissance of polypharmacology in the development of anti-cancer therapeutics: Inhibition of the "Triad of Death" in cancer by Di-2-pyridylketone thiosemicarbazones.

Cancer is a disease that is a "moving target", since as the condition progresses, the molecular targets change and evolve. Moreover, due to clonal selection, a specific anti-cancer drug with one molecular target may only be effective for a limited time period before drug resistance results and the agent becomes ineffective. Hence, the concept of an anti-tumor therapeutic exhibiting polypharmacology can be highly advantageous, rather than a therapeutic obstacle. A novel class of agents possessing these desirable properties are the di-2-pyridylketone thiosemicarbazones, which bind iron and copper to affect a variety of critical molecular targets in tumors. In fact, these compounds possess multiple properties that enable them to overcome the "triad of death" in cancer, namely: primary tumor growth, drug resistance and metastasis. In fact, at the molecular level, their potent anti-oncogenic activity includes: up-regulation of the metastasis suppressor, N-myc downstream regulated gene 1; up-regulation of the tumor suppressor, PTEN; down-regulation of the proto-oncogene, cyclin D1; inhibition of the rate-limiting step in DNA synthesis catalyzed by ribonucleotide reductase; and the inhibition of multiple oncogenic signaling pathways, e.g., Ras/MAPK signaling, protein kinase B (AKT)/phosphatidylinositol-3-kinase, ROCK/pMLC2, etc. This Perspective article discusses the advantages of incorporating polypharmacology into anti-cancer drug design using the di-2-pyridylketone thiosemicarbazones as a pertinent example.

Targeting Oncogenic Nuclear Factor Kappa B Signaling with Redox-Active Agents for Cancer Treatment.

SIGNIFICANCE: Nuclear factor kappa B (NF-κB) signaling is essential under physiologically relevant conditions. However, aberrant activation of this pathway plays a pertinent role in tumorigenesis and contributes to resistance. Recent Advances: The importance of the NF-κB pathway means that its targeting must be specific to avoid side effects. For many currently used therapeutics and those under development, the ability to generate reactive oxygen species (ROS) is a promising strategy. CRITICAL ISSUES: As cancer cells exhibit greater ROS levels than their normal counterparts, they are more sensitive to additional ROS, which may be a potential therapeutic niche. It is known that ROS are involved in (i) the activation of NF-κB signaling, when in sublethal amounts; and (ii) high levels induce cytotoxicity resulting in apoptosis. Indeed, ROS-induced cytotoxicity is valuable for its capabilities in killing cancer cells, but establishing the potency of ROS for effective inhibition of NF-κB signaling is necessary. Indeed, some cancer treatments, currently used, activate NF-κB and may stimulate oncogenesis and confer resistance. FUTURE DIRECTIONS: Thus, combinatorial approaches using ROS-generating agents alongside conventional therapeutics may prove an effective tactic to reduce NF-κB activity to kill cancer cells. One strategy is the use of thiosemicarbazones, which form redox-active metal complexes that generate high ROS levels to deliver potent antitumor activity. These agents also upregulate the metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), which functions as an NF-κB signaling inhibitor. It is proposed that targeting NF-κB signaling may proffer a new therapeutic niche to improve the efficacy of anticancer regimens.

Copper and conquer: copper complexes of di-2-pyridylketone thiosemicarbazones as novel anti-cancer therapeutics.

Copper is an essential trace metal required by organisms to perform a number of important biological processes. Copper readily cycles between its reduced Cu(i) and oxidised Cu(ii) states, which makes it redox active in biological systems. This redox-cycling propensity is vital for copper to act as a catalytic co-factor in enzymes. While copper is essential for normal physiology, enhanced copper levels in tumours leads to cancer progression. In particular, the stimulatory effect of copper on angiogenesis has been established in the last several decades. Additionally, it has been demonstrated that copper affects tumour growth and promotes metastasis. Based on the effects of copper on cancer progression, chelators that bind copper have been developed as anti-cancer agents. In fact, a novel class of thiosemicarbazone compounds, namely the di-2-pyridylketone thiosemicarbazones that bind copper, have shown great promise in terms of their anti-cancer activity. These agents have a unique mechanism of action, in which they form redox-active complexes with copper in the lysosomes of cancer cells. Furthermore, these agents are able to overcome P-glycoprotein (P-gp) mediated multi-drug resistance (MDR) and act as potent anti-oncogenic agents through their ability to up-regulate the metastasis suppressor protein, N-myc downstream regulated gene-1 (NDRG1). This review provides an overview of the metabolism and regulation of copper in normal physiology, followed by a discussion of the dysregulation of copper homeostasis in cancer and the effects of copper on cancer progression. Finally, recent advances in our understanding of the mechanisms of action of anti-cancer agents targeting copper are discussed.