Mono-ADP-ribosyltransferase 1 ( Artc1 )-deficiency decreases tumorigenesis, increases inflammation, decreases cardiac contractility, and reduces survival

Arginine-specific mono-ADP-ribosylation is a reversible post-translational modification; arginine-specific, cholera toxin-like mono-ADP-ribosyltransferases (ARTCs) transfer ADP-ribose from NAD ⁺ to arginine, followed by cleavage of ADP-ribose-(arginine)protein bond by ADP-ribosylarginine hydrolase 1 (ARH1), generating unmodified (arginine)protein. ARTC1 has been shown to enhance tumorigenicity as does Arh1 deficiency. In this study, Artc1 -KO and Artc1/Arh1 -double-KO mice showed decreased spontaneous tumorigenesis and increased age-dependent, multi-organ inflammation with upregulation of pro-inflammatory cytokine TNF- α . In a xenograft model using tumorigenic Arh1 -KO mouse embryonic fibroblasts (MEFs), tumorigenicity was decreased in Artc1 -KO and heterozygous recipient mice, with tumor infiltration by CD8 ⁺ T cells and macrophages, leading to necroptosis, suggesting that ARTC1 promotes the tumor microenvironment. Furthermore, Artc1/Arh1 -double-KO MEFs showed decreased tumorigenesis in nude mice, showing that tumor cells as well as tumor microenvironment require ARTC1. By echocardiography and MRI, Artc1 -KO and heterozygous mice showed male-specific, reduced myocardial contractility. Furthermore, Artc1 -KO male hearts exhibited enhanced susceptibility to myocardial ischemia-reperfusion-induced injury with increased receptor-interacting protein kinase 3 (RIP3) protein levels compared to WT mice, suggesting that ARTC1 suppresses necroptosis. Overall survival rate of Artc1 -KO was less than their Artc1 -WT counterparts, primarily due to enhanced immune response and inflammation. Thus, anti-ARTC1 agents may reduce tumorigenesis but may increase multi-organ inflammation and decrease cardiac contractility.

Uncovering the Invisible: Mono-ADP-ribosylation Moved into the Spotlight

Adenosine diphosphate (ADP)-ribosylation is a nicotinamide adenine dinucleotide (NAD+)-dependent post-translational modification that is found on proteins as well as on nucleic acids. While ARTD1/PARP1-mediated poly-ADP-ribosylation has extensively been studied in the past 60 years, comparably little is known about the physiological function of mono-ADP-ribosylation and the enzymes involved in its turnover. Promising technological advances have enabled the development of innovative tools to detect NAD+ and NAD+/NADH (H for hydrogen) ratios as well as ADP-ribosylation. These tools have significantly enhanced our current understanding of how intracellular NAD dynamics contribute to the regulation of ADP-ribosylation as well as to how mono-ADP-ribosylation integrates into various cellular processes. Here, we discuss the recent technological advances, as well as associated new biological findings and concepts.

Identification of Glioma Specific Genes as Diagnostic and Prognostic Markers for Glioma

Background:

Malignant gliomas are the most prevalent malignancy of the brain. However, there was still lack of sensitive and accurate biomarkers for gliomas.

Objective:

To explore the mechanisms underlying glioma progression and identify novel diagnostic and prognostic markers for glioma.

Methods:

By analyzing TCGA dataset, whole-genome genes expression levels were evaluated in 19 different types of human cancers. A protein-protein interacting network was constructed to reveal the potential roles of these glioma special genes. KEGG and GO analysis revealed the potential effect of these genes.

Results:

We identified 698 gliomas specially expressed genes by analyzing TCGA dataset. A protein-protein interacting network was constructed to reveal the potential roles of these glioma special genes. KEGG and GO analysis showed gliomas specially expressed genes were involved in regulating neuroactive ligand-receptor interaction, retrograde endocannabinoid signaling, Glutamatergic synapse, chemical synaptic transmission, nervous system development, central nervous system development, and learning. Of note, GRIA1, GNAO1, GRIN1, CACNA1A, CAMK2A, and SYP were identified to be down-regulated and associated with poor prognosis in gliomas.

Conclusion:

GRIA1, GNAO1, GRIN1, CACNA1A, CAMK2A, and SYP were identified to be down-regulated and associated with poor prognosis in gliomas. We thought this study will provide novel biomarkers for gliomas.

PARP and PARG inhibitors in cancer treatment

In this review, Slade provides an overview of the molecular mechanisms and cellular consequences of PARP and PARG inhibition. The author also highlights the clinical performance of four PARP inhibitors used in cancer therapy (olaparib, rucaparib, niraparib, and talazoparib) and discusses the predictive biomarkers of inhibitor sensitivity and mechanisms of resistance as well as the means of overcoming them through combination therapy.

Oxidative and replication stress underlie genomic instability of cancer cells. Amplifying genomic instability through radiotherapy and chemotherapy has been a powerful but nonselective means of killing cancer cells. Precision medicine has revolutionized cancer therapy by putting forth the concept of selective targeting of cancer cells. Poly(ADP-ribose) polymerase (PARP) inhibitors represent a successful example of precision medicine as the first drugs targeting DNA damage response to have entered the clinic. PARP inhibitors act through synthetic lethality with mutations in DNA repair genes and were approved for the treatment of BRCA mutated ovarian and breast cancer. PARP inhibitors destabilize replication forks through PARP DNA entrapment and induce cell death through replication stress-induced mitotic catastrophe. Inhibitors of poly(ADP-ribose) glycohydrolase (PARG) exploit and exacerbate replication deficiencies of cancer cells and may complement PARP inhibitors in targeting a broad range of cancer types with different sources of genomic instability. Here I provide an overview of the molecular mechanisms and cellular consequences of PARP and PARG inhibition. I highlight clinical performance of four PARP inhibitors used in cancer therapy (olaparib, rucaparib, niraparib, and talazoparib) and discuss the predictive biomarkers of inhibitor sensitivity, mechanisms of resistance as well as the means of overcoming them through combination therapy.

Twenty Metabolic Genes Based Signature Predicts Survival of Glioma Patients

Background: Glioma, caused by carcinogenesis of brain and spinal glial cells, is the most common primary malignant brain tumor. To find the important indicator for glioma prognosis is still a challenge and the metabolic alteration of glioma has been frequently reported recently.

Methods: In our current work, a risk score model based on the expression of twenty metabolic genes was developed using the metabolic gene expressions in The Cancer Genome Atlas (TCGA) dataset, the methods of which included the cox multivariate regression and the random forest variable hunting, a kind of machine learning algorithm, and the risk score generated from this model is used to make predictions in the survival of glioma patients in the training dataset. Subsequently, the result was further verified in other three verification sets (GSE4271, GSE4412 and GSE16011). Risk score related pathways collected in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database were identified using Gene Set Enrichment Analysis (GSEA).

Results: The risk score generated from our model makes good predictions in the survival of glioma patients in the training dataset and other three verification sets. By assessing the relationships between clinical indicators and the risk score, we found that the risk score was an independent and significant indicator for the prognosis of glioma patients. Simultaneously, we conducted a survival analysis of the patients who received chemotherapy and who did not, finding that the risk score was equally valid in both cases. And signaling pathways related to the genesis and development of multiple cancers were also identified.

Conclusions: In summary, our risk score model is predictive for 967 glioma patients' survival from four independent datasets, and the risk score is a meaningful and independent parameter of the clinicopathological information.

31 gene expression-based signatures serve as indicators of prognosis for patients with glioma

Glioma has one of the highest mortality rates of all cancer types; however, the prognosis cannot be predicted effectively using clinical indicators, due to the biological heterogeneity of the disease. A total of 31 gene expression-based signatures were identified using selected features in The Cancer Genome Atlas cohorts and machine learning methods. The signatures were assayed in the training dataset and were further validated in four completely independent datasets. Association analyses were implemented, and the results indicated that the signature was not significantly associated with age, radiation therapy or primary tumor size. A nomogram for the 1-year overall survival rate of patients with glioma following initial diagnosis was plotted to facilitate the clinical utilization of the signature. Gene Set Enrichment Analysis was performed based on the signature, in order to determine the potential altered pathways. Metabolic pathways were determined to be significantly enriched. In summary, the 31 gene expression-based signatures were effective and robust in predicting the clinical outcome of glioma in 1,016 glioma samples in five independent international cohorts.

PARP-1 regulates DNA repair factor availability

PARP-1 holds major functions on chromatin, DNA damage repair and transcriptional regulation, both of which are relevant in the context of cancer. Here, unbiased transcriptional profiling revealed the downstream transcriptional profile of PARP-1 enzymatic activity. Further investigation of the PARP-1-regulated transcriptome and secondary strategies for assessing PARP-1 activity in patient tissues revealed that PARP-1 activity was unexpectedly enriched as a function of disease progression and was associated with poor outcome independent of DNA double-strand breaks, suggesting that enhanced PARP-1 activity may promote aggressive phenotypes. Mechanistic investigation revealed that active PARP-1 served to enhance E2F1 transcription factor activity, and specifically promoted E2F1-mediated induction of DNA repair factors involved in homologous recombination (HR). Conversely, PARP-1 inhibition reduced HR factor availability and thus acted to induce or enhance "BRCA-ness". These observations bring new understanding of PARP-1 function in cancer and have significant ramifications on predicting PARP-1 inhibitor function in the clinical setting.

Emerging roles of ADP-ribosyl-acceptor hydrolases (ARHs) in tumorigenesis and cell death pathways

Malignant transformation may occur in the background of post-translational modification, such as ADP-ribosylation, phosphorylation and acetylation. Recent genomic analysis of ADP-ribosylation led to the discovery of more than twenty ADP-ribosyltransferases (ARTs), which catalyze either mono- or poly-ADP-ribosylation. ARTs catalyze the attachment of ADP-ribose to acceptor molecules. The ADP-ribose-acceptor bond can then be cleaved by a family of hydrolases in a substrate-specific manner, which is dependent on the acceptor and its functional group, e.g., arginine (guanidino), serine (hydroxyl), aspartate (carboxyl). These hydrolases vary in structure and function, and include poly-ADP-ribose glycohydrolase (PARG), MacroD1, MacroD2, terminal ADP-ribose protein glycohydrolase 1 (TARG1) and ADP-ribosyl-acceptor hydrolases (ARHs). In murine models, PARG deficiency increased susceptibility to alkylating agents-induced carcinogenesis. Similarly, by cleaving mono-ADP-ribosylated arginine on target proteins, ARH1 appears to inhibit tumor formation, suggesting that ARH1 is a tumor-suppressor gene. Although ARH3 is similar to ARH1 in amino acid sequence and crystal structure, ARH3 does not cleave ADP-ribose-arginine, rather it degrades in an exocidic manner, the PAR polymer and cleaves O-acetyl-ADP-ribose (OAADPr) and the ADP-ribose-serine linkage in acceptor proteins. Under conditions of oxidative stress, ARH3-deficient cells showed increased cytosolic PAR accumulation and PARP-1 mediated cell death. These findings expand our understanding of ADP-ribosylation and provide new therapeutic targets for cancer treatment. In the present review, research on ARH1-regulated tumorigenesis and cell death pathways that are enhanced by ARH3 deficiency are discussed.

β-asarone inhibited cell growth and promoted autophagy via P53/Bcl-2/Bclin-1 and P53/AMPK/mTOR pathways in Human Glioma U251 cells

Glioma is the most common type of primary brain tumor and has an undesirable prognosis. Autophagy plays an important role in cancer therapy, but it is effect is still not definite. P53 is an important tumor suppressor gene and protein that is closely to autophagy. Our aim was to study the effect of β-asarone on inhibiting cell proliferation in human glioma U251 cells and to detect the effect of the inhibition on autophagy through the P53 signal pathway. For cell growth, the cells were divided into four groups: the model, β-asarone, temozolomide (TMZ), and co-administration groups. For cell autoghapy and the P53 pathway, the cells were divided into six groups: the model, β-asarone, 3MA, Rapa, Pifithrin-µ, and NSC groups. The counting Kit-8 assay and flow cytometry (FCM) were then used to measure the cell proliferation and cycle. Electron microscopy was used to observe autophagosome formation. Cell immunohistochemistry/-immunofluorescence, FCM and Western blot (WB) were used to examine the expression of Beclin-1 and P53. The levels of P53 and GAPDH mRNA were detected by RT-PCR. Using WB, we determined autophagy-related proteins Beclin-1, LC3-II/I, and P62 and those of the P53 pathway-related proteins P53, Bcl-2, mTOR, P-mTOR, AMPK, P-AMPK, and GAPDH. We got the results that β-asarone changed the cellular morphology, inhibited cell proliferation, and enhanced the expression of P53, LC3-II/I, Beclin-1, AMPK, and pAMPK while inhibiting the expression of P62, Bcl-2, mTOR, and pmTOR. All the data suggested that β-asarone could reduce the cell proliferation and promote autophagy possible via the P53 pathway in U251 cells.