Differential targeting of the cyclin-dependent kinase inhibitor, p21CIP1/WAF1, by chelators with anti-proliferative activity in a range of tumor cell-types

Sex-Specific Associations of MDM2 and MDM4 Variants with Risk of Multiple Primary Melanomas and Melanoma Survival in Non-Hispanic Whites

MDM2-SNP309 (rs2279744), a common genetic modifier of cancer incidence in Li-Fraumeni syndrome, modifies risk, age of onset, or prognosis in a variety of cancers. Melanoma incidence and outcomes vary by sex, and although SNP309 exerts an effect on the estrogen receptor, no consensus exists on its effect on melanoma. MDM2 and MDM4 restrain p53-mediated tumor suppression, independently or together. We investigated SNP309, an a priori MDM4-rs4245739, and two coinherited variants, in a population-based cohort of 3663 primary incident melanomas. Per-allele and per-haplotype (MDM2_SNP309-SNP285; MDM4_rs4245739-rs1563828) odds ratios (OR) for multiple-melanoma were estimated with logistic regression models. Hazard ratios (HR) for melanoma death were estimated with Cox proportional hazards models. In analyses adjusted for covariates, females carrying MDM4-rs4245739*C were more likely to develop multiple melanomas (ORper-allele = 1.25, 95% CI 1.03-1.51, and Ptrend = 0.03), while MDM2-rs2279744*G was inversely associated with melanoma-death (HRper-allele = 0.63, 95% CI 0.42-0.95, and Ptrend = 0.03). We identified 16 coinherited expression quantitative loci that control the expression of MDM2, MDM4, and other genes in the skin, brain, and lungs. Our results suggest that MDM4/MDM2 variants are associated with the development of subsequent primaries and with the death of melanoma in a sex-dependent manner. Further investigations of the complex MDM2/MDM4 motif, and its contribution to the tumor microenvironment and observed associations, are warranted.

CDK regulators—Cell cycle progression or apoptosis—Scenarios in normal cells and cancerous cells

Serine/threonine kinases called cyclin-dependent kinases (CDKs) interact with cyclins and CDK inhibitors (CKIs) to control the catalytic activity. CDKs are essential controllers of RNA transcription and cell cycle advancement. The ubiquitous overactivity of the cell cycle CDKs is caused by a number of genetic and epigenetic processes in human cancer, and their suppression can result in both cell cycle arrest and apoptosis. This review focused on CDKs, describing their kinase activity, their role in phosphorylation inhibition, and CDK inhibitory proteins (CIP/KIP, INK 4, RPIC). We next compared the role of different CDKs, mainly p21, p27, p57, p16, p15, p18, and p19, in the cell cycle and apoptosis in cancer cells with respect to normal cells. The current work also draws attention to the use of CDKIs as therapeutics, overcoming the pharmacokinetic barriers of pan-CDK inhibitors, analyze new chemical classes that are effective at attacking the CDKs that control the cell cycle (cdk4/6 or cdk2). It also discusses CDKI's drawbacks and its combination therapy against cancer patients. These findings collectively demonstrate the complexity of cancer cell cycles and the need for targeted therapeutic intervention. In order to slow the progression of the disease or enhance clinical outcomes, new medicines may be discovered by researching the relationship between cell death and cell proliferation.

Azulene hydrazide-hydrazones for selective targeting of pancreatic cancer cells

Dysregulation of iron homeostasis is one of the important processes in the development of many oncological diseases, such as pancreatic cancer. Targeting it with specific agents, such as an iron chelator, are promising therapeutic methods. In this study, we tested the cytotoxicity of novel azulene hydrazide-hydrazone-based chelators against pancreatic cancer cell lines (MIA PaCa-2, PANC-1, AsPC-1). All prepared chelators (compounds 4-6) showed strong cytotoxicity against pancreatic cancer cell lines and high selectivity for cancer cell lines compared to the healthy line. Their cytotoxicity is lower than thiosemicarbazone-based chelators Dp44mT and DpC, but significantly higher than hydroxamic acid-based chelator DFO. The chelator tested showed mitochondrial and lysosomal co-localization and its mechanism of action was based on the induction of hypoxia-inducible factor-1-alpha (HIF-1α), N-myc downstream-regulated gene-1 (NDRG1) and transferrin receptor 1 (TfR1). This strongly implies that the cytotoxic effect of tested chelators could be associated with mitophagy induction. Lipinski's rule of five analyses was performed to determine whether the prepared compounds had properties ensuring their bioavailability. In addition, the drug-likeness and drug-score were calculated and discussed.

Crystal structure of (E)-N′-(1-(2-hydroxy-4-methoxyphenyl)ethylidene) isonicotinohydrazide, C15H15N3O3

C15H15N3O3, triclinic, P 1 ‾ $\overline{1}$ (no. 2), a = 9.0752(2) Å, b = 9.1969(2) Å, c = 9.9519(2) Å, α = 112.7059(8)°, β = 92.4309(8)°, γ = 115.2776(7)°, V = 671.16(3) Å3, Z = 2, R gt (F) = 0.0347, wR ref (F 2) = 0.1113, T = 100 K.

Reversing oncogenic transformation with iron chelation

Cancer cells accumulate iron to supplement their aberrant growth and metabolism. Depleting cells of iron by iron chelators has been shown to be selectively cytotoxic to cancer cells in vitro and in vivo. Iron chelators are effective at combating a range of cancers including those which are difficult to treat such as androgen insensitive prostate cancer and cancer stem cells. This review will evaluate the impact of iron chelation on cancer cell survival and the underlying mechanisms of action. A plethora of studies have shown iron chelators can reverse some of the major hallmarks and enabling characteristics of cancer. Iron chelators inhibit signalling pathways that drive proliferation, migration and metastasis as well as return tumour suppressive signalling. In addition to this, iron chelators stimulate apoptotic and ER stress signalling pathways inducing cell death even in cells lacking a functional p53 gene. Iron chelators can sensitise cancer cells to PARP inhibitors through mimicking BRCAness; a feature of cancers trademark genomic instability. Iron chelators target cancer cell metabolism, attenuating oxidative phosphorylation and glycolysis. Moreover, iron chelators may reverse the major characteristics of oncogenic transformation. Iron chelation therefore represent a promising selective mode of cancer therapy.

New derivatives of 4'-phenyl-2,2':6',2″-terpyridine as promising anticancer agents

Terpyridine derivatives are known from their broad application including anticancer properties. In this work we present the newly synthesized 4'-phenyl-2,2':6',2″-terpyridine group with high antiproliferative activity. We suggest that these compounds influence cellular redox homeostasis. Cancer cells are particularly susceptible to any changes in the redox balance because of their handicapped and inefficient antioxidant cellular systems. The antiproliferative activity of the studied compounds was tested on five different cell lines that represent several types of tumours; glioblastoma, leukemia, breast, pancreatic and colon. Additionally, we also tested their selectivity towards normal cells. We performed molecular biology studies in order to detect the response of a cell to its treatment with the compounds that were tested. We looked at the in-depth changes in the proteins and cellular pathways that lead to cell cycle inhibition (G0/G1 and S), and consequently, death on the apoptosis and autophagy pathways. We proved that the studied compounds targeted DNA as well. Special attention was paid to the targets connected with ROS generation.

Deferasirox-Dependent Iron Chelation Enhances Mitochondrial Dysfunction and Restores p53 Signaling by Stabilization of p53 Family Members in Leukemic Cells

Iron is crucial to satisfy several mitochondrial functions including energy metabolism and oxidative phosphorylation. Patients affected by Myelodysplastic Syndromes (MDS) and acute myeloid leukemia (AML) are frequently characterized by iron overload (IOL), due to continuous red blood cell (RBC) transfusions. This event impacts the overall survival (OS) and it is associated with increased mortality in lower-risk MDS patients. Accordingly, the oral iron chelator Deferasirox (DFX) has been reported to improve the OS and delay leukemic transformation. However, the molecular players and the biological mechanisms laying behind remain currently mostly undefined. The aim of this study has been to investigate the potential anti-leukemic effect of DFX, by functionally and molecularly analyzing its effects in three different leukemia cell lines, harboring or not p53 mutations, and in human primary cells derived from 15 MDS/AML patients. Our findings indicated that DFX can lead to apoptosis, impairment of cell growth only in a context of IOL, and can induce a significant alteration of mitochondria network, with a sharp reduction in mitochondrial activity. Moreover, through a remarkable reduction of Murine Double Minute 2 (MDM2), known to regulate the stability of p53 and p73 proteins, we observed an enhancement of p53 transcriptional activity after DFX. Interestingly, this iron depletion-triggered signaling is enabled by p73, in the absence of p53, or in the presence of a p53 mutant form. In conclusion, we propose a mechanism by which the increased p53 family transcriptional activity and protein stability could explain the potential benefits of iron chelation therapy in terms of improving OS and delaying leukemic transformation.

Recent advances in iron-complexes as drug candidates for cancer therapy: reactivity, mechanism of action and metabolites

In this perspective, we discuss iron-complexes as drug candidates that are promising alternatives to conventional platinum-based chemotherapies owing to their broad range of reactivities and to the targeting of different biological systems. Breakthroughs in the comprehension of iron complexes' structure-activity relationship contributed to the clarification of their metabolization pathways, sub-cellular localization and influence on iron homeostasis, while enlightening the primary molecular targets of theses likely multi-target metallodrugs. Both the antiproliferative activity and elevated safety index observed among the family of iron complexes showed encouraging results as per their therapeutic potential and selectivity also with the aim of reducing chemotherapy side-effects, and facilitated more pre-clinical investigations. The purpose of this perspective is to summarize the recent advances that contributed in unveiling the intricate relationships between the structural modifications on iron-complexes and their reactivity, cellular trafficking and global mechanisms of action to broaden their use as anticancer drugs and advance to clinical evaluation.

Acireductone dioxygenase 1 (ADI1) is regulated by cellular iron by a mechanism involving the iron chaperone, PCBP1, with PCBP2 acting as a potential co-chaperone

The iron-containing protein, acireductone dioxygenase 1 (ADI1), is a dioxygenase important for polyamine synthesis and proliferation. Using differential proteomics, the studies herein demonstrated that ADI1 was significantly down-regulated by cellular iron depletion. This is important, since ADI1 contains a non-heme, iron-binding site critical for its activity. Examination of multiple human cell-types demonstrated a significant decrease in ADI1 mRNA and protein after incubation with iron chelators. The decrease in ADI1 after iron depletion was reversible upon incubation of cells with the iron salt, ferric ammonium citrate (FAC). A significant decrease in ADI1 mRNA levels was observed after 14 h of iron depletion. In contrast, the chelator-mediated reduction in ADI1 protein occurred earlier after 10 h of iron depletion, suggesting additional post-transcriptional regulation. The proteasome inhibitor, MG-132, prevented the iron chelator-mediated decrease in ADI1 expression, while the lysosomotropic agent, chloroquine, had no effect. These results suggest an iron-dependent, proteasome-mediated, degradation mechanism. Poly r(C)-binding protein (PCBPs) 1 and 2 act as iron delivery chaperones to other iron-containing dioxygenases and were shown herein for the first time to be regulated by iron levels. Silencing of PCBP1, but not PCBP2, led to loss of ADI1 expression. Confocal microscopy co-localization studies and proximity ligation assays both demonstrated decreased interaction of ADI1 with PCBP1 and PCBP2 under conditions of iron depletion using DFO. These data indicate PCBP1 and PCBP2 interact with ADI1, but only PCBP1 plays a role in ADI1 expression. In fact, PCBP2 appeared to play an accessory role, being involved as a potential co-chaperone.

Anticancer Thiosemicarbazones: Chemical Properties, Interaction with Iron Metabolism, and Resistance Development

SIGNIFICANCE

During the past decades, thiosemicarbazones were clinically developed for a variety of diseases, including tuberculosis, viral infections, malaria, and cancer. With regard to malignant diseases, the class of α-N-heterocyclic thiosemicarbazones, and here especially 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (Triapine), was intensively developed in multiple clinical phase I/II trials. Recent Advances: Very recently, two new derivatives, namely COTI-2 and di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) have entered phase I evaluation. Based on the strong metal-chelating/metal-interacting properties of thiosemicarbazones, interference with the cellular iron (and copper) homeostasis is assumed to play an important role in their biological activity.

CRITICAL ISSUES

In this review, we summarize and analyze the data on the interaction of (α-N-heterocyclic) thiosemicarbazones with iron, with the special aim of bridging the current knowledge on their mode of action from chemistry to (cell) biology. In addition, we highlight the difference to classical iron(III) chelators such as desferrioxamine (DFO), which are used for the treatment of iron overload.

FUTURE DIRECTIONS

We want to emphasize that thiosemicarbazones are not solely removing iron from the cells/organism. In contrast, they should be considered as iron-interacting drugs influencing diverse biological pathways in a complex and multi-faceted mode of action. Consequently, in addition to the discussion of physicochemical properties (e.g., complex stability, redox activity), this review contains an overview on the diversity of cellular thiosemicarbazone targets and drug resistance mechanisms.

Ironing out the role of the cyclin-dependent kinase inhibitor, p21 in cancer: Novel iron chelating agents to target p21 expression and activity

Iron (Fe) has become an important target for the development of anti-cancer therapeutics with a number of Fe chelators entering human clinical trials for advanced and resistant cancer. An important aspect of the activity of these compounds is their multiple molecular targets, including those that play roles in arresting the cell cycle, such as the cyclin-dependent kinase inhibitor, p21. At present, the exact mechanism by which Fe chelators regulate p21 expression remains unclear. However, recent studies indicate the ability of chelators to up-regulate p21 at the mRNA level was dependent on the chelator and cell-type investigated. Analysis of the p21 promoter identified that the Sp1-3-binding site played a significant role in the activation of p21 transcription by Fe chelators. Furthermore, there was increased Sp1/ER-α and Sp1/c-Jun complex formation in melanoma cells, suggesting these complexes were involved in p21 promoter activation. Elucidating the mechanisms involved in the regulation of p21 expression in response to Fe chelator treatment in neoplastic cells will further clarify how these agents achieve their anti-tumor activity. It will also enhance our understanding of the complex roles p21 may play in neoplastic cells and lead to the development of more effective and specific anti-cancer therapies.

Transcriptional regulation of the cyclin-dependent kinase inhibitor, p21CIP1/WAF1, by the chelator, Dp44mT

BACKGROUND

The cyclin-dependent kinase inhibitor, p21, is well known for its role in cell cycle arrest. Novel anti-cancer agents that deplete iron pools demonstrate marked anti-tumor activity and are also active in regulating p21 expression. These agents induce p21 mRNA levels independently of the tumor suppressor, p53, and differentially regulate p21 protein expression depending on the cell-type. Several chelators, including an analogue of the potent anti-tumor agent, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), have entered clinical trials, and thus, their molecular mechanism of action is crucial to assess. Hence, this investigation examined how several iron chelators transcriptionally regulate p21.

METHODS

Promoter-deletion constructs; luciferase assays; RT-PCR; western analysis; gene silencing; co-immunoprecipitation.

RESULTS

The transcriptional regulation of the p21 promoter by iron chelators was demonstrated to be dependent on the chelator and cell-type examined. The potent anti-cancer chelator, Dp44mT, induced p21 promoter activity in SK-MEL-28 melanoma cells, but not in MCF-7 breast cancer cells. Further analysis of the p21 promoter identified a 50-bp region between -104 and -56-bp that was required for Dp44mT-induced activation in SK-MEL-28 cells. This region contained several Sp1-binding sites and mutational analysis of this region revealed the Sp1-3-binding site played a significant role in Dp44mT-induced activation of p21. Further, co-immunoprecipitation demonstrated that Dp44mT induced a marked increase in the interactions between Sp1 and the transcription factors, estrogen receptor-α and c-Jun.

CONCLUSIONS AND GENERAL SIGNIFICANCE

Dp44mT-induced p21 promoter activation via the Sp1-3-binding site and increased Sp1/ER-α and Sp1/c-Jun complex formation in SK-MEL-28 cells, suggesting these complexes were involved in p21 promoter activation.

Interplay of the iron-regulated metastasis suppressor NDRG1 with epidermal growth factor receptor (EGFR) and oncogenic signaling

The iron-regulated metastasis suppressor N-myc downstream-regulated gene 1 (NDRG1) has been shown to inhibit numerous oncogenic signaling pathways in cancer cells. Recent findings have demonstrated that NDRG1 inhibits the ErbB family of receptors, which function as key inducers of carcinogenesis. NDRG1 attenuates ErbB signaling by inhibiting formation of epidermal growth factor receptor (EGFR)/human epidermal growth factor receptor 2 (HER2) and HER2/HER3 heterodimers and by down-regulating EGFR via a mechanism involving its degradation. Understanding the complex interplay between NDRG1, iron, and ErbB signaling is vital for identifying novel, more effective targets for cancer therapy.