Implications For Anticancer Therapy Research Articles

Unravelling the Role of PARP1 in Homeostasis and Tumorigenesis: Implications for Anti-Cancer Therapies and Overcoming Resistance.

Detailing the connection between homeostatic functions of enzymatic families and eventual progression into tumorigenesis is crucial to our understanding of anti-cancer therapies. One key enzyme group involved in this process is the Poly (ADP-ribose) polymerase (PARP) family, responsible for an expansive number of cellular functions, featuring members well established as regulators of DNA repair, genomic stability and beyond. Several PARP inhibitors (PARPi) have been approved for clinical use in a range of cancers, with many more still in trials. Unfortunately, the occurrence of resistance to PARPi therapy is growing in prevalence and requires the introduction of novel counter-resistance mechanisms to maintain efficacy. In this review, we summarize the updated understanding of the vast homeostatic functions the PARP family mediates and pin the importance of PARPi therapies as anti-cancer agents while discussing resistance mechanisms and current up-and-coming counter-strategies for countering such resistance.

DNA damage independent inhibition of NF-kB transcription by anthracyclines.

Anthracyclines are among the most used and effective anticancer drugs. Their activity has been attributed to DNA double-strand breaks resulting from topoisomerase II poisoning and to eviction of histones from select sites in the genome. Here we show that the extensively used anthracyclines Doxorubicin, Daunorubicin and Epirubicin decrease the transcription of nuclear factor kappa B (NF-κB)-dependent gene targets, but not interferon responsive genes in primary mouse (Mus musculus) macrophages. Using an NMR-based structural approach, we demonstrate that anthracyclines disturb the complexes formed between the NF-kB subunit RelA and its DNA binding sites. The anthracycline variants Aclarubicin, Doxorubicinone and the newly developed Dimethyl-doxorubicin, which share anticancer properties with the other anthracyclines but do not induce DNA damage, also suppressed inflammation, thus uncoupling DNA damage from the effects on inflammation. These findings have implications for anticancer therapy and for the development of novel anti-inflammatory drugs with limited side effects for life-threatening conditions such as sepsis.

Extracellular DNA Traps: Origin, Function and Implications for Anti-Cancer Therapies.

Extracellular DNA may serve as marker in liquid biopsies to determine individual diagnosis and prognosis in cancer patients. Cell death or active release from various cell types, including immune cells can result in the release of DNA into the extracellular milieu. Neutrophils are important components of the innate immune system, controlling pathogens through phagocytosis and/or the release of neutrophil extracellular traps (NETs). NETs also promote tumor progression and metastasis, by modulating angiogenesis, anti-tumor immunity, blood clotting and inflammation and providing a supportive niche for metastasizing cancer cells. Besides neutrophils, other immune cells such as eosinophils, dendritic cells, monocytes/macrophages, mast cells, basophils and lymphocytes can also form extracellular traps (ETs) during cancer progression, indicating possible multiple origins of extracellular DNA in cancer. In this review, we summarize the pathomechanisms of ET formation generated by different cell types, and analyze these processes in the context of cancer. We also critically discuss potential ET-inhibiting agents, which may open new therapeutic strategies for cancer prevention and treatment.

CuO Nanoparticles as Copper-Ion Reservoirs for Elesclomol-Mediated Intracellular Oxidative Stress: Implications for Anticancer Therapies

CuO Nanoparticles as Copper-Ion Reservoirs for Elesclomol-Mediated Intracellular Oxidative Stress: Implications for Anticancer Therapies

Factors governing the affinity and selectivity of histone deacetylase inhibitors for the HDAC8 enzyme active site: Implications for anticancer therapy

AbstractDisruptions in post‐translational modifications of chromatin structure promote uncontrollable cell growth branded as a hallmark of tumor lesions. The overexpression/hyperactivity of histone deacetylases (HDACs) is a common feature for the tumorogenesis and cancer progression. Several inhibitors of histone deacetylases (mainly hydroxamic acid derivatives) have been successfully used as drugs in fighting tumor formations. However, there is no systematic study on the factors controlling the affinity and selectivity of this type of inhibitors to the host enzyme thus hampering successful rational design of more potent and selective anticancer drugs. Herein, in an attempt to unravel the mechanism of the host–guest interactions in these systems at atomic level, we systematically study the effect of various factors in the process and elucidate its key determinants. Density functional theory calculations have been employed. Our findings have the potential to be employed as guidelines in designing new HDAC inhibitors with improved anticancer properties.

DNA Damage Independent Inhibition of NF-κB Transcription by Anthracyclines

Anthracyclines are among the most used and effective anticancer drugs. Their activity has been attributed to DNA double-strand breaks resulting from topoisomerase II poisoning and to eviction of histones from select sites in the genome. Here we show that the extensively used anthracyclines Doxorubicin, Daunorubicin and Epirubicin, decrease the transcription of nuclear factor kappa B (NF-κB)-dependent gene targets, but not interferon responsive genes. Using an NMR-based structural approach, we demonstrate that anthracyclines disturb the complexes formed between the NF-kB subunit RelA and its DNA binding sites. The variant anthracyclines Aclarubicin, Doxorubicinone and the newly developed Dimethyl-doxorubicin, which share anticancer properties with the other anthracyclines but do not induce DNA damage, also suppressed inflammation, thus uncoupling DNA damage from the effects on inflammation. These findings have implications for anticancer therapy and for the development of novel anti-inflammatory drugs with limited side effects for life-threatening conditions such as sepsis.

Colon cancer stemness as a reversible epigenetic state: Implications for anticancer therapies.

The recent discovery of cancer cell plasticity, i.e. their ability to reprogram into cancer stem cells (CSCs) either naturally or under chemotherapy and/or radiotherapy, has changed, once again, the way we consider cancer treatment. If cancer stemness is a reversible epigenetic state rather than a genetic identity, opportunities will arise for therapeutic strategies that remodel epigenetic landscapes of CSCs. However, the systematic use of DNA methyltransferase and histone deacetylase inhibitors, alone or in combination, in advanced solid tumors including colorectal cancers, regardless of their molecular subtypes, does not seem to be the best strategy. In this review, we first summarize the knowledge researchers have gathered on the epigenetic signatures of CSCs with the difficulty of isolating rare populations of cells. We raise questions about the relevant use of currently available epigenetic inhibitors (epidrugs) while the expression of numerous cancer stem cell markers are often repressed by epigenetic mechanisms. These markers include the three cluster of differentiation CD133, CD44 and CD166 that have been extensively used for the isolation of colon CSCs.and . Finally, we describe current treatment strategies using epidrugs, and we hypothesize that, using correlation tools comparing associations of relevant CSC markers with chromatin modifier expression, we could identify better candidates for epienzyme targeting.

Investigation of inhibitory potential of quercetin to the pyruvate dehydrogenase kinase 3: Towards implications in anticancer therapy

Pyruvate dehydrogenase kinase 3 (PDK3) is a mitochondrial protein, has recently been considered as a potential pharmacological target for varying types of cancer. Here, we report the binding mechanism of quercetin to the PDK3 by using molecular docking, simulation, fluorescence spectroscopy and isothermal titration calorimetric assays. Molecular docking along with simulation provided an in-depth analysis of protein-ligand interactions. We have observed that quercetin interacts to the important residues of active site cavity of PDK3 and shows a well-ordered conformational fitting. The stability of quercetin-PDK3 complex is maintained by several non-covalent interactions throughout the simulation. To complement in silico findings with the experiments, we have successfully expressed and purified human PDK3. Both fluorescence and isothermal titration calorimetric experiments showed excellent binding affinity of quercetin to the PDK3. Kinase inhibition assay further revealed a significant inhibitory potential of quercetin to the PDK3 with the IC50 values in μM range. Quercetin is non-toxic to HEK293, and significantly inhibits the proliferation of cancer (HepG2 and A549) cell lines. All these observations clearly indicate that quercetin may be further evaluated as promising therapeutic molecule for PDK3 with required modifications and in vivo validation.

Mistletoe and Immunomodulation: Insights and Implications for Anticancer Therapies.

In early tumor development, cancer cells develop a plethora of strategies to escape surveillance from the adaptive and innate immune system. Cancer immunotherapies, in particular immune checkpoint inhibitors, are becoming a highly promising cancer therapeutic approach that has remarkable increased progress in combating various cancer types. Unfortunately, their mechanisms of action induce some complications, such as inflammatory reactions and immune-related adverse events. In the management of side effects during anticancer therapy, complementary and integrative therapy approaches are becoming of growing interest. Particularly, mistletoe, Viscum album L. (VA), has a long traditional history of about 100 years as an add-on therapy of cancer treatment in German-speaking countries. Besides antitumoral and quality of life-promoting activities, VA applications reduce side effects of modern conventional anticancer therapies and exert immunomodulatory characteristics. As these properties may provide a good basis for a combination with modern oncological therapies, the biological activities of VA applications and mechanisms involved have to be understood. In this review, the impact of VA compounds on different cellular pathways and immunological reactions in the fight against cancerous cells is discussed.

Regulatory T cells in cancer immunosuppression - implications for anticancer therapy.

Regulatory T (Treg) cells, an immunosuppressive subset of CD4+ T cells characterized bythe expression of the master transcription factor forkhead box protein P3 (FOXP3), are a component of the immune system with essential roles in maintaining self-tolerance. In addition, Treg cells can suppress anticancer immunity, thereby hindering protective immunosurveillance ofneoplasia and hampering effective antitumour immune responses in tumour-bearing hosts, thus promoting tumour development and progression. Identification of the factors that are specifically expressed in Treg cells and/or that influence Treg cell homeostasis and function is important to understanding cancer pathogenesis and to identifying therapeutic targets. Immune-checkpoint inhibitors (ICIs) have provided a paradigm shift in the treatment of cancer. Most immune-checkpoint molecules are expressed in Treg cells, but the effects of ICIs on Treg cells, and thus the contributions of these cells to treatment responses, remain unclear. Notably, evidence indicates that ICIs targeting programmed cell death 1 (PD-1) might enhance the immunosuppressive function of Treg cells, whereas cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibitors might deplete these cells.Thus, although manipulation of Treg cells is a promising anticancer therapeutic strategy, approaches to controlling these cells require further research. Herein, we discuss novel insights into the roles of Treg cells in cancer, which can hopefully be used to develop Treg cell-targeted therapies and facilitate immune precision medicine.

A current understanding of drug-induced QT prolongation and its implications for anticancer therapy.

The QT interval, a global index of ventricular repolarization, varies among individuals and is influenced by diverse physiologic and pathophysiologic stimuli such as gender, age, heart rate, electrolyte concentrations, concomitant cardiac disease, and other diseases such as diabetes. Many drugs produce a small but reproducible effect on QT interval but in rare instances this is exaggerated and marked QT prolongation can provoke the polymorphic ventricular tachycardia 'torsades de pointes', which can cause syncope or sudden cardiac death. The generally accepted common mechanism whereby drugs prolong QT is block of a key repolarizing potassium current in heart, IKr, generated by expression of KCNH2, also known as HERG. Thus, evaluation of the potential that a new drug entity may cause torsades de pointes has relied on exposure of normal volunteers or patients to drug at usual and high concentrations, and on assessment of IKr block in vitro. More recent work, focusing on anticancer drugs with QT prolonging liability, is defining new pathways whereby drugs can prolong QT. Notably, the in vitro effects of some tyrosine kinase inhibitors to prolong cardiac action potentials (the cellular correlate of QT) can be rescued by intracellular phosphatidylinositol 3,4,5-trisphosphate, the downstream effector of phosphoinositide 3-kinase. This finding supports a role for inhibition of this enzyme, either directly or by inhibition of upstream kinases, to prolong QT through mechanisms that are being worked out, but include enhanced inward 'late' sodium current during the plateau of the action potential. The definition of non-IKr-dependent pathways to QT prolongation will be important for assessing risk, not only with anticancer therapies but also with other QT prolonging drugs and for generating a refined understanding how variable activity of intracellular signalling systems can modulate QT and associated arrhythmia risk.

Vitamin D as a Novel Regulator of Tumor Metabolism: Insights on Potential Mechanisms and Implications for Anti-Cancer Therapy.

1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the bioactive form of vitamin D, has been shown to possess significant anti-tumor potential. While most studies so far have focused on the ability of this molecule to influence the proliferation and apoptosis of cancer cells, more recent data indicate that 1,25(OH)2D3 also impacts energy utilization in tumor cells. In this article, we summarize and review the evidence that demonstrates the targeting of metabolic aberrations in cancers by 1,25(OH)2D3, and highlight potential mechanisms through which these effects may be executed. We shed light on the ability of this molecule to regulate metabolism-related tumor suppressors and oncogenes, energy- and nutrient-sensing pathways, as well as cell death and survival mechanisms such as autophagy.

Abstract 4403: FDG uptake in human lung adenocarcinoma associated with invasion through the hexosamine biosynthesis pathway

Abstract Introduction Metabolic reprogramming is a cancer hallmark that is not fully understood. Moreover, increasing evidence suggests that metabolic dysregulation is histology-specific, particularly in the case of non-small cell lung cancer (NSCLC). In this study, we investigated the differences in glucose metabolism between the two major histology subtypes of NSCLC, namely adenocarcinoma (AD) and squamous cell carcinoma (SQ). We explored transcriptomics in association with FDG-PET SUVmax (maximum standardized uptake value), a common clinical marker of glucose uptake in cancer. Methods We identified metabolically-associated differentially expressed genes (DEGs) by histology subtypes using RNAseq data from resected tumors in our study cohort of 127 NSCLC patients (96 AD and 31 SQ) and validated the DEGs on The Cancer Genome Atlas. We also identified gene-enriched cellular processes correlated with SUVmax separately for AD and SQ. We validated our findings in public domain cell line microarray data. In a separate cohort of 40 NSCLC patients (20 patients overlap with study cohort) whose tumors were sorted by cell type (cancer, endothelial, fibroblast and immune cells), we identified specific cell types where the genes of interest were expressed. Results Metabolically-associated DEGs in AD were enriched in the hexosamine biosynthesis pathway (HBP), which is involved in glycosylating proteins related to invasion. SUVmax correlated genes in AD were enriched for epithelial-mesenchymal transition (EMT) and extracellular matrix remodeling. In particular, GFPT2 (the rate-limiting gene in HBP) and 4 EMT-related glycoprotein genes were highly correlated with SUVmax, suggesting potency of HBP for EMT related glucose metabolic reprogramming. We validated the findings on cell line microarray data (GSE49644) before and after TGF-β induced EMT, showing that many genes in HBP increased after induced EMT, while genes in the glycolysis pathway and the pentose phosphate pathway (PPP) were unchanged or reduced. HBP genes and many SUVmax correlated EMT genes were most highly expressed in tumor-associated fibroblasts compared to other cells in the tumor microenvironment. In SQ, metabolically-associated DEGs were enriched in the glycolysis pathway and PPP. SUVmax correlated genes were enriched for cell development. Conclusion An integrative analysis of PET-RNAseq showed that in AD glucose uptake was related to invasion through metabolic reprogramming of HBP. In SQ, glucose uptake was associated with glycolysis and higher proliferation potential. Our work confirms that metabolic dysregulation in NSCLC is histology-specific and extends the finding to identify cellular processes associated with FDG uptake that differ by histology as well. Understanding histology-specific differences of tumor metabolism provides new insights into tumor behavior that can have implications for anti-cancer therapy. Citation Format: Weiruo Zhang, Gina Bouchard, Alice Yu, Majid Shafiq, Mehran Jamali, Joseph Shrager, Kelsey Ayers, Viswam S. Nair, Andrew Gentles, Maximilian Diehn, Andrew Quon, Sandy Napel, Sylvia Plevritis. FDG uptake in human lung adenocarcinoma associated with invasion through the hexosamine biosynthesis pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4403. doi:10.1158/1538-7445.AM2017-4403

Contradictory Relationships between Cancer and Normal Cells and Implications for Anti-cancer Therapy.

Cancer treatment remains a serious problem worldwide. Analysis of the relationship between cancer cells and normal cells reveals that these two share characteristics in contradiction, thus could be analyzed by using contradictory principles. Under the theory of contradictory principles, induction of a dormant state or reversal of cancer cells is an important treatment strategy beyond traditional cytotoxic therapy. Normal cells are also the targets and under the influence of anti-cancer treatments and should be considered during therapy. Findings based on crosstalk between these two cell types may offer opportunities for the development of new biomarkers and therapies.

Dynamic impacts of the inhibition of the molecular chaperone Hsp90 on the T-cell proteome have implications for anti-cancer therapy.

The molecular chaperone Hsp90-dependent proteome represents a complex protein network of critical biological and medical relevance. Known to associate with proteins with a broad variety of functions termed clients, Hsp90 maintains key essential and oncogenic signalling pathways. Consequently, Hsp90 inhibitors are being tested as anti-cancer drugs. Using an integrated systematic approach to analyse the effects of Hsp90 inhibition in T-cells, we quantified differential changes in the Hsp90-dependent proteome, Hsp90 interactome, and a selection of the transcriptome. Kinetic behaviours in the Hsp90-dependent proteome were assessed using a novel pulse-chase strategy (Fierro-Monti et al., accompanying article), detecting effects on both protein stability and synthesis. Global and specific dynamic impacts, including proteostatic responses, are due to direct inhibition of Hsp90 as well as indirect effects. As a result, a decrease was detected in most proteins that changed their levels, including known Hsp90 clients. Most likely, consequences of the role of Hsp90 in gene expression determined a global reduction in net de novo protein synthesis. This decrease appeared to be greater in magnitude than a concomitantly observed global increase in protein decay rates. Several novel putative Hsp90 clients were validated, and interestingly, protein families with critical functions, particularly the Hsp90 family and cofactors themselves as well as protein kinases, displayed strongly increased decay rates due to Hsp90 inhibitor treatment. Remarkably, an upsurge in survival pathways, involving molecular chaperones and several oncoproteins, and decreased levels of some tumour suppressors, have implications for anti-cancer therapy with Hsp90 inhibitors. The diversity of global effects may represent a paradigm of mechanisms that are operating to shield cells from proteotoxic stress, by promoting pro-survival and anti-proliferative functions. Data are available via ProteomeXchange with identifier PXD000537.

Macro-management of microRNAs in cell cycle progression of tumor cells and its implications in anti-cancer therapy

The cell cycle, which is precisely controlled by a number of regulators, including cyclins and cyclin-dependent kinases (CDKs), is crucial for the life cycle of mammals. Cell cycle dysregulation is implicated in many diseases, including cancer. Recently, compelling evidence has been found that microRNAs play important roles in the regulation of cell cycle progression by modulating the expression of cyclins, CDKs and other cell cycle regulators. Herein, the recent findings on the regulation of the cell cycle by microRNAs are summarized, and the potential implications of miRNAs in anti-cancer therapies are discussed.

Key mechanisms underlying cancer stem cell overpopulation in colon carcinomas: Implications for anticancer therapy.

e13548 Background: Since cancer stem cell (SC) overpopulation appears to drive tumor growth in the colon (Boman and Huang, JCO 26:2828-38, 2008), effective or even curative treatments will likely require targeting mechanisms that underlie SC overpopulation. To identify such mechanisms, the organization and distribution of colonocyte cell subpopulations in human colon tissues were investigated as a way to evaluate crypt cell maturation. We hypothesized that maturation of these subpopulations becomes dysregulated during colon tumorigenesis. Methods: Quantitative immunohistochemical mapping of crypt cell subpopulations was done using markers for SC (ALDH1), proliferating cells (DNA-synthesis-licensing proteins: CDT1/geminin/MCM2), cell-cycle arrest (P21), and apoptosis (M30/TUNEL). Staining indices were used to evaluate changes in maturation during the step-wise progression to colon cancer. The rate of crypt cell maturation was measured using clearance of BrdU from pre-labeled wildtype (C57BL/6) and premalignant (ApcMin/+) mouse intestine. Results: In normal human colon, the proportion of cells expressing licensing proteins was low at crypt bottom (where SC reside), high in the lower crypt where proliferating cells reside, and nil in the upper crypt (where differentiated/apoptotic cells reside). In FAP and adenomatous human crypts, SC and proliferating cell populations expanded towards the crypt top while differentiated/apoptotic subpopulations in the upper crypt contracted. ApcMin/+ mouse crypts had slower BrdU clearance than controls. Conclusions: Colonocytes become licensed for DNA synthesis in the transition from SC to proliferating cells; licensing is delayed in premalignant crypts. Moreover, all transitions between cell phenotypes occur more slowly in premalignant human colonic crypts, indicating that crypt cell maturation becomes progressively delayed during colon tumorigenesis. Our data indicate that cancer stem cell overpopulation arises from impaired colonocyte maturation; therapeutically targeting mechanisms to restore cell maturation may reverse SC overpopulation and tumor growth. Supported by NIH DK062146.

Autophagy: Molecular Mechanisms and their Implications for Anticancer Therapies

Autophagy is a catabolic process whereby cells maintain homeostasis by eliminating unnecessary proteins and damaged organelles. It may be triggered under physiological conditions, such as nutrient starvation, or in response to a variety of stress stimuli, such as exposure to radiations or cytotoxic compounds. Although autophagy is basically a protective mechanism that sustains cell survival under adverse conditions, it has been recently demonstrated that the induction of autophagic process may ultimately lead to cell death. As for the role of autophagy in cancer, it is still very controversial whether it suppresses tumorigenesis or provides cancer cells with a rescue mechanism under unfavourable conditions. Therefore, the dual role of autophagy in tumor progression and in the response of cancer cells to chemotherapeutic drugs is still open to debate. The first part of this review describes the cellular events occurring during the various phases of the autophagic process. Special attention has been given to the morphological aspects and the regulatory molecules involved in autophagic cell death. Specifically, we have focused on the proteins necessary for autophagosome formation, encoded by the ATG (AuTophaGy-related gene) gene family, and their role in the regulation of the process of autophagy. We also examined the effects of autophagy modulators on cell survival and cell death and discussed the recent efforts aimed at finding novel agents that activate or inhibit autophagy by targeting regulatory molecules of the complex autophagy pathways.

362 Targeting the glycolytic cancer cell – cancer-specific modulation of NAD+ and NADH and implications for anti-cancer therapy

Adequate response to low oxygen levels (hypoxia) by hypoxia inducible factor (HIF) is essential for normal development and physiology, but this pathway may also contribute to pathological processes like tumor angiogenesis. Here we show that hypoxia is an inducer of Notch signaling. Hypoxic conditions lead to induction of the Notch ligand Dll4 and the Notch target genes Hey1 and Hey2 in various cell lines. Promoter analysis revealed that Hey1, Hey2 and Dll4 are induced by HIF-1α and Notch activation. Hypoxia-induced Notch signaling may also determine endothelial identity. Endothelial progenitor cells (EPCs) contain high amounts of COUP-TFII, a regulator of vein identity, while levels of the arterial regulators Dll4 and Hey2 are low. Hypoxia-mediated upregulation of Dll4 and Hey2 leads to repression of COUP-TFII in eEPCs. Finally, we show that Hey factors are capable of repressing HIF-1α-induced gene expression, suggesting a negative feedback loop to prevent excessive hypoxic gene induction. Thus, reduced oxygen levels lead to activation of the Dll4-Notch-Hey2 signaling cascade and subsequent repression of COUP-TFII in endothelial progenitor cells. We propose that this is an important step in the developmental regulation of arterial cell fate decision.

Insights into minimal residual disease in cancer patients: Implications for anti-cancer therapies

Tumor cell dissemination appears even in patients with small solid tumors, and bone marrow (BM) is a common homing organ for disseminated tumor cells (DTC) derived from various types of primary epithelial tumors. Tumor cells are frequently detected in the BM of cancer patients without any clinical or even histopathological signs of overt metastases. It is crucial, however, to improve and standardize methods for the detection of DTC. The characterization of DTC has shed new light on the process underlying early tumor cell dissemination and metastatic progression in cancer patients. Characterization of DTC should help to identify novel targets for biological therapies aimed at preventing metastatic relapse and to monitor the efficacy of these therapies. Evidence has emerged that the detection of DTC and circulating tumor cells (CTC) in blood may provide important prognostic information and, in addition, might help to monitor the efficacy of therapy. In this article, we summarize the clinical background and the technical aspects of current methods used for the detection and characterization of DTC in BM and CTC in blood, with a special focus on breast cancer.