Enhancement of poly-adenosine diphosphate-ribosylation in human hepatocellular carcinoma

Expression of LC3A, LC3B and p62/SQSTM1 autophagy proteins in hepatocellular carcinoma (HCC) tissues and the predicted microRNAs involved in the autophagy-related pathway

BACKGROUND

Autophagy plays multifaceted roles in regulating hepatocellular carcinoma (HCC) and the mechanisms involved are under-explored. Regulatory microRNAs (miRNAs) have been reported to target autophagy proteins but their roles in HCC is not well studied. Using HCC patient tissues, this study aims to investigate the association of autophagy with several clinicopathological parameters as well as identifying the autophagy-related miRNAs and the possible pathways.

METHODS AND RESULTS

Autophagy level in the HCC patient-derived cancer and non-cancer tissues was determined by immunohistochemistry (IHC) targeting SQSTM1, LC3A and LC3B proteins. Significance tests of clinicopathological variables were tested using the Fisher's exact or Chi-square tests. Gene and miRNA expression assays were carried out and analyzed using Nanostring platform and software followed by validation of other online bioinformatics tools, namely String and miRabel. Autophagy expression was significantly higher in cancerous tissues compared to adjacent non-cancer tissues. High LC3B expression was associated with advanced tumor histology grade and tumor location. Nanostring gene expression analysis revealed that SQSTM1, PARP1 and ATG9A genes were upregulated in HCC tissues compared to non-cancer tissues while SIRT1 gene was downregulated. These genes are closely related to an autophagy pathway in HCC. Further, using miRabel tool, three downregulated miRNAs (hsa-miR-16b-5p, hsa-miR-34a-5p, and hsa-miR-660-5p) and one upregulated miRNA (hsa-miR-539-5p) were found to closely interact with the abovementioned autophagy-related genes. We then mapped out the possible pathway involving the genes and miRNAs in HCC tissues.

CONCLUSIONS

We conclude that autophagy events are more active in HCC tissues compared to the adjacent non-cancer tissues. We also reported the possible role of several miRNAs in regulating autophagy-related genes in the autophagy pathway in HCC. This may contribute to the development of potential therapeutic targets for improving HCC therapy. Future investigations are warranted to validate the target genes reported in this study using a larger sample size and more targeted molecular technique.

Hepatitis B virus infection disrupts homologous recombination in hepatocellular carcinoma by stabilizing resection inhibitor ADRM1

Many cancers harbor homologous recombination defects (HRDs). A HRD is a therapeutic target that is being successfully utilized in treatment of breast/ovarian cancer via synthetic lethality. However, canonical HRD caused by BRCAness mutations do not prevail in liver cancer. Here we report a subtype of HRD caused by the perturbation of a proteasome variant (CDW19S) in hepatitis B virus-bearing (HBV-bearing) cells. This amalgamate protein complex contained the 19S proteasome decorated with CRL4WDR70 ubiquitin ligase, and assembled at broken chromatin in a PSMD4Rpn10- and ATM-MDC1-RNF8-dependent manner. CDW19S promoted DNA end processing via segregated modules that promote nuclease activities of MRE11 and EXO1. Contrarily, a proteasomal component, ADRM1Rpn13, inhibited resection and was removed by CRL4WDR70-catalyzed ubiquitination upon commitment of extensive resection. HBx interfered with ADRM1Rpn13 degradation, leading to the imposition of ADRM1Rpn13-dependent resection barrier and consequent viral HRD subtype distinguishable from that caused by BRCA1 defect. Finally, we demonstrated that viral HRD in HBV-associated hepatocellular carcinoma can be exploited to restrict tumor progression. Our work clarifies the underlying mechanism of a virus-induced HRD subtype.

Early in vitro evidence indicates that deacetylated sialic acids modulate multi-drug resistance in colon and lung cancers via breast cancer resistance protein

Cancers utilize sugar residues to engage in multidrug resistance. The underlying mechanism of action involving glycans, specifically the glycan sialic acid (Sia) and its various functional group alterations, has not been explored. ATP-binding cassette (ABC) transporter proteins, key proteins utilized by cancers to engage in multidrug resistant (MDR) pathways, contain Sias in their extracellular domains. The core structure of Sia can contain a variety of functional groups, including O-acetylation on the C6 tail. Modulating the expression of acetylated-Sias on Breast Cancer Resistance Protein (BCRP), a significant ABC transporter implicated in MDR, in lung and colon cancer cells directly impacted the ability of cancer cells to either retain or efflux chemotherapeutics. Via CRISPR-Cas-9 gene editing, acetylation was modulated by the removal of CAS1 Domain-containing protein (CASD1) and Sialate O-Acetyl esterase (SIAE) genes. Using western blot, immunofluorescence, gene expression, and drug sensitivity analysis, we confirmed that deacetylated Sias regulated a MDR pathway in colon and lung cancer in early in vitro models. When deacetylated Sias were expressed on BCRP, colon and lung cancer cells were able to export high levels of BCRP to the cell's surface, resulting in an increased BCRP efflux activity, reduced sensitivity to the anticancer drug Mitoxantrone, and high proliferation relative to control cells. These observations correlated with increased levels of cell survival proteins, BcL-2 and PARP1. Further studies also implicated the lysosomal pathway for the observed variation in BCRP levels among the cell variants. RNASeq data analysis of clinical samples revealed higher CASD1 expression as a favorable marker of survival in lung adenocarcinoma. Collectively, our findings indicate that deacetylated Sia is utilized by colon and lung cancers to engage in MDR via overexpression and efflux action of BCRP.

Fluorescence-Based Analyses of Poly(ADP-Ribose) Length by Gel Electrophoresis, High-Performance Liquid Chromatography, and Capillary Electrophoresis

Poly(ADP-ribose) (PAR) is a homopolymer made of two or more adenosine diphosphate ribose (ADP-ribose) units. The polymer is usually conjugated to protein as a posttranslational modification playing key roles in cellular processes, such as DNA repair, RNA metabolism, and biomolecular condensate formation. Emergent data revealed that PAR length is highly regulated and determines the selection of and affinity towards protein binders. Here, we describe several fluorescence-based methods that quantify PAR length distributions. Briefly, we use the bioconjugation technique ELTA (enzymatic labeling of terminal ADP-ribose) to fluorescently label PAR, which can be isolated from in vitro and cellular samples. We describe a novel capillary electrophoresis method to separate and quantify PAR length and compare the profile to gel electrophoresis- and high-performance liquid chromatography-based methods. The capillary electrophoresis method is rapid and automatable, enabling accurate determination of the length profiles from subfemtomole quantities of PAR.

Computational compensatory mutation discovery approach: Predicting a PARP1 variant rescue mutation

The prediction of protein mutations that affect function may be exploited for multiple uses. In the context of disease variants, the prediction of compensatory mutations that reestablish functional phenotypes could aid in the development of genetic therapies. In this work, we present an integrated approach that combines coevolutionary analysis and molecular dynamics (MD) simulations to discover functional compensatory mutations. This approach is employed to investigate possible rescue mutations of a poly(ADP-ribose) polymerase 1 (PARP1) variant, PARP1 V762A, associated with lung cancer and follicular lymphoma. MD simulations show PARP1 V762A exhibits noticeable changes in structural and dynamical behavior compared with wild-type (WT) PARP1. Our integrated approach predicts A755E as a possible compensatory mutation based on coevolutionary information, and molecular simulations indicate that the PARP1 A755E/V762A double mutant exhibits similar structural and dynamical behavior to WT PARP1. Our methodology can be broadly applied to a large number of systems where single-nucleotide polymorphisms have been identified as connected to disease and can shed light on the biophysical effects of such changes as well as provide a way to discover potential mutants that could restore WT-like functionality. This can, in turn, be further utilized in the design of molecular therapeutics that aim to mimic such compensatory effect.

Poly(ADP-Ribose) Polymerase Inhibition as a Promising Approach for Hepatocellular Carcinoma Therapy

Primary liver cancer is the sixth most common cancer in men and seventh in women, with hepatocellular carcinoma (HCC) being the most common form (75-85% of primary liver cancer cases) and the most frequent etiology being viral infections (HBV and HCV). In 2020, mortality represented 92% of the incidence-830,180 deaths for 905,677 new cases. Few treatment options exist for advanced or terminal-stage HCC, which will receive systemic therapy or palliative care. Although radiotherapy is used in the treatment of many cancers, it is currently not the treatment of choice for HCC, except in the palliative setting. However, as radiosensitizing drugs, such as inhibitors of DNA repair enzymes, could potentiate the effects of RT in HCC by exploiting the modulation of DNA repair processes found in this tumour type, RT and such drugs could provide a treatment option for HCC. In this review, we provide an overview of PARP1 involvement in DNA damage repair pathway and discuss its potential implication in HCC. In addition, the use of PARP inhibitors and PARP decoys is described for the treatment of HCC and, in particular, in HBV-related HCC.

Pleiotropic role of PARP1: an overview

Poly (ADP-ribose) polymerase 1 (PARP1) protein is encoded by the PARP1 gene located on chromosome 1 (1q42.12) in human cells. It plays a crucial role in post-translational modification by adding poly (ADP-ribose) (PAR) groups to various proteins and PARP1 itself by utilizing nicotinamide adenine dinucleotide (NAD +) as a substrate. Since the discovery of PARP1, its role in DNA repair and cell death has been its identity. This is evident from an overwhelmingly high number of scientific reports in this regard. However, PARP1 also plays critical roles in inflammation, metabolism, tumor development and progression, chromatin modification and transcription, mRNA stability, and alternative splicing. In the present study, we attempted to compile all the scattered scientific information about this molecule, including the structure and multifunctional role of PARP1 in cancer and non-cancer diseases, along with PARP1 inhibitors (PARPis). Furthermore, for the first time, we have classified PARP1-mediated cell death for ease of understanding its role in cell death pathways.

Identification of a novel histone phosphorylation prognostic signature in hepatocellular carcinoma based on bulk and single-cell RNA sequencing

BACKGROUND

Hepatocellular carcinoma (HCC) is the third leading cause of death in the world, characterized by high morbidity, poor prognosis and high mortality. Histone modifications regulate intracellular gene expression at the post-transcriptional level, and disturbances in the regulatory pattern of histone modifications at individual locus or across the genome can lead to tumorigenesis of HCC. In this study, we constructed a prognosis-related histone phosphorylation regulated (HPR) genes signature and elucidated whether HPR genes can predict overall survival in HCC patients.

METHODS

Differentially expressed genes were screened using TCGA, ICGC and GEO databases, and a new risk signature was constructed by univariate Cox regression and Lasso regression analysis. Predictive nomograms were established by multivariate Cox regression of risk scores and clinical parameters, calibration curve and decision curve analysis were used to evaluate the models. The ssGSEA methods were used to determine the effect of risk scores on the tumor immune microenvironment. Data for HCC single-cell RNA sequencing (scRNA-seq) have been downloaded from Gene Expression Omnibus (GEO) to understand the role of HPR genes in tumorigenesis.

RESULTS

Our analyses of nine HPR genes provided prognostic insights. Overall survival in the low-risk and high-risk groups was statistically higher, respectively (P<0.001). Cox regression analysis revealed that the risk score is a significant predictor of HCC outcomes (HR=2. 2.62, 95%CI: 1.248-5.514, P=0.011). In addition, a nomogram combining risk scores with TNM stages was constructed and tested from calibration curves and decision curves (AUC=0.780). MHC-class-I genes, iDCs, Macrophages, Tfh, Treg, Th2 were overexpressed in the high-risk group.

CONCLUSION

HPR genes risk score is closely related to the prognosis of HCC, tumor immune process and tumor cell progression.

Insight Into Nicotinamide Adenine Dinucleotide Homeostasis as a Targetable Metabolic Pathway in Colorectal Cancer

Tumour cells modify their cellular metabolism with the aim to sustain uncontrolled proliferation. Cancer cells necessitate adequate amounts of NAD and NADPH to support several enzymes that are usually overexpressed and/or overactivated. Nicotinamide adenine dinucleotide (NAD) is an essential cofactor and substrate of several NAD-consuming enzymes, such as PARPs and sirtuins, while NADPH is important in the regulation of the redox status in cells. The present review explores the rationale for targeting the key enzymes that maintain the cellular NAD/NADPH pool in colorectal cancer and the enzymes that consume or use NADP(H).

Inhibiting Src-mediated PARP1 tyrosine phosphorylation confers synthetic lethality to PARP1 inhibition in HCC

Hepatocellular carcinoma (HCC), a heterogeneous cancer with high mortality, is resistant to single targeted therapy; thus, combination therapy based on synthetic lethality is a promising therapeutic strategy for HCC. Poly (adenosine diphosphate [ADP]-ribose) polymerase 1 (PARP1) is the most recognized target for synthetic lethality; however, the therapeutic effect of PARP1 inhibition on HCC is disappointing. Therefore, exploring new synthetic lethal partners for the efficient manipulation of HCC is urgently required. In this study, we identified Src and PARP1 as novel synthetic lethal partners, and the combination therapy produced significant anti-tumor effects without causing obvious side effects. Mechanistically, Src interacted with PARP1 and phosphorylated PARP1 at the Y992 residue, which further mediated resistance to PARP1 inhibition. Overall, this study revealed that Src-mediated PARP1 phosphorylation induced HCC resistance to PARP1 inhibitors and indicated a therapeutic window of the Y992 phosphorylation of PARP1 for HCC patients. Moreover, synthetic lethal therapy by co-targeting PARP1 and Src have the potential to broaden the strategies for HCC and might benefit HCC patients with high Src activation and resistance to PARP1 inhibitors alone.

Therapeutic Potential of PARP Inhibitors in the Treatment of Gastrointestinal Cancers

Gastrointestinal (GI) malignancies are a major global health burden, with high mortality rates. The identification of novel therapeutic strategies is crucial to improve treatment and survival of patients. The poly (ADP-ribose) polymerase (PARP) enzymes involved in the DNA damage response (DDR) play major roles in the development, progression and treatment response of cancer, with PARP inhibitors (PARPi) currently used in the clinic for breast, ovarian, fallopian, primary peritoneal, pancreatic and prostate cancers with deficiencies in homologous recombination (HR) DNA repair. This article examines the current evidence for the role of the DDR PARP enzymes (PARP1, 2, 3 and 4) in the development, progression and treatment response of GI cancers. Furthermore, we discuss the role of HR status as a predictive biomarker of PARPi efficacy in GI cancer patients and examine the pre-clinical and clinical evidence for PARPi and cytotoxic therapy combination strategies in GI cancer. We also include an analysis of the genomic and transcriptomic landscape of the DDR PARP genes and key HR genes (BRCA1, BRCA2, ATM, RAD51, MRE11, PALB2) in GI patient tumours (n = 1744) using publicly available datasets to identify patients that may benefit from PARPi therapeutic approaches.

microRNAs Biogenesis, Functions and Role in Tumor Angiogenesis

microRNAs (miRNAs) are small non-coding RNA molecules, evolutionary conserved. They target more than one mRNAs, thus influencing multiple molecular pathways, but also mRNAs may bind to a variety of miRNAs, either simultaneously or in a context-dependent manner. miRNAs biogenesis, including miRNA transcription, processing by Drosha and Dicer, transportation, RISC biding, and miRNA decay, are finely controlled in space and time. miRNAs are critical regulators in various biological processes, such as differentiation, proliferation, apoptosis, and development in both health and disease. Their dysregulation is involved in tumor initiation and progression. In tumors, they can act as onco-miRNAs or oncosuppressor-miRNA participating in distinct cellular pathways, and the same miRNA can perform both activities depending on the context. In tumor progression, the angiogenic switch is fundamental. miRNAs derived from tumor cells, endothelial cells, and cells of the surrounding microenvironment regulate tumor angiogenesis, acting as pro-angiomiR or anti-angiomiR. In this review, we described miRNA biogenesis and function, and we update the non-classical aspects of them. The most recent role in the nucleus, as transcriptional gene regulators and the different mechanisms by which they could be dysregulated, in tumor initiation and progression, are treated. In particular, we describe the role of miRNAs in sprouting angiogenesis, vessel co-option, and vasculogenic mimicry. The role of miRNAs in lymphoma angiogenesis is also discussed despite the scarcity of data. The information presented in this review reveals the need to do much more to discover the complete miRNA network regulating angiogenesis, not only using high-throughput computational analysis approaches but also morphological ones.

A functional polymorphism in the poly(ADP-ribose) polymerase-1 gene is associated with platinum-based chemotherapeutic response and prognosis in epithelial ovarian cancer patients

OBJECTIVE

To explore the effects of two functional genetic variants of poly(ADP-ribose) polymerase-1 (PARP-1) on the susceptibility to epithelial ovarian cancer (EOC), the platinum-based chemotherapeutic response, and the prognosis of northern Chinese patients.

STUDY DESIGN

This case-control study included 710 EOC patients in the case group and 700 healthy women in the control group. Two polymorphisms (rs1136410 and rs8679) of PARP-1 were genotyped by polymerase chain reaction and ligase detection reaction.

RESULTS

The genotype frequencies of rs1136410 and rs8679 were not significantly different between the case and control groups. However, the CC genotype of rs1136410 was significantly associated with a favorable response to platinum drugs. Compared with the TT genotype, the CC genotype of rs1136410 was related to a reduced risk of platinum resistance (adjusted OR: 0.40; 95% CI = 0.24-0.67; P = 0.001). In addition, multivariable analysis containing clinical variables showed that patients who carried the rs1136410 CC genotype had a significantly improved progression-free survival compared with patients who carried the TT genotype (HR = 0.67, 95% CI = 0.47-0.97, P = 0.031).

CONCLUSION

The rs1136410 polymorphism may serve as a potential marker for predicting the response to platinum agents and prognosis of EOC patients treated with surgery and platinum-based chemotherapy.

Targeting the DNA Damage Response to Overcome Cancer Drug Resistance in Glioblastoma

Glioblastoma multiforme (GBM) is a severe brain tumor whose ability to mutate and adapt to therapies is at the base for the extremely poor survival rate of patients. Despite multiple efforts to develop alternative forms of treatment, advances have been disappointing and GBM remains an arduous tumor to treat. One of the leading causes for its strong resistance is the innate upregulation of DNA repair mechanisms. Since standard therapy consists of a combinatory use of ionizing radiation and alkylating drugs, which both damage DNA, targeting the DNA damage response (DDR) is proving to be a beneficial strategy to sensitize tumor cells to treatment. In this review, we will discuss how recent progress in the availability of the DDR kinase inhibitors will be key for future therapy development. Further, we will examine the principal existing DDR inhibitors, with special focus on those currently in use for GBM clinical trials.

Proteomics Profiling of KAIMRC1 in Comparison to MDA-MB231 and MCF-7

Proteomics characterization of KAIMRC1 cell line, a naturally immortalized breast cancer cells, is described in comparison to MCF-7 and MDA-MB-231 breast cancer cells. Quantitative proteomics analysis using the tandem mass tag (TMT)-labeled technique in conjunction with the phosphopeptide enrichment method was used to perform comparative profiling of proteins and phosphoproteins in the three cell lines. In total, 673 proteins and 33 Phosphoproteins were differentially expressed among these cell lines. These proteins are involved in several key cellular pathways that include DNA replication and repair, splicing machinery, amino acid metabolism, cellular energy, and estrogen signaling pathway. Many of the differentially expressed proteins are associated with different types of tumors including breast cancer. For validation, 4 highly significant expressed proteins including S-methyl-5'-thioadenosine phosphorylase (MTAP), BTB/POZ domain-containing protein (KCTD12), Poly (ADP-ribose) polymerase 1 (PARP 1), and Prelamin-A/C were subjected to western blotting, and the results were consistent with proteomics analysis. Unlike MCF-7 and MDA-MB-231, KAIMRC1 showed different phospho- and non-phosphoproteomic phenotypes which make it a potential model to study breast cancer.

Precision medicine in gastric cancer

Gastric cancer (GC) is a complex disease linked to a series of environmental factors and unhealthy lifestyle habits, and especially to genetic alterations. GC represents the second leading cause of cancer-related deaths worldwide. Its onset is subtle, and the majority of patients are diagnosed once the cancer is already advanced. In recent years, there have been innovations in the management of advanced GC including the introduction of new classifications based on its molecular characteristics. Thanks to new technologies such as next-generation sequencing and microarray, the Cancer Genome Atlas and Asian Cancer Research Group classifications have also paved the way for precision medicine in GC, making it possible to integrate diagnostic and therapeutic methods. Among the objectives of the subdivision of GC into subtypes is to select patients in whom molecular targeted drugs can achieve the best results; many lines of research have been initiated to this end. After phase III clinical trials, trastuzumab, anti-Erb-B2 receptor tyrosine kinase 2 (commonly known as ERBB2) and ramucirumab, anti-vascular endothelial growth factor receptor 2 (commonly known as VEGFR2) monoclonal antibodies, were approved and introduced into first- and second-line therapies for patients with advanced/metastatic GC. However, the heterogeneity of this neoplasia makes the practical application of such approaches difficult. Unfortunately, scientific progress has not been matched by progress in clinical practice in terms of significant improvements in prognosis. Survival continues to be low in contrast to the reduction in deaths from many common cancers such as colorectal, lung, breast, and prostate cancers. Although several target molecules have been identified on which targeted drugs can act and novel products have been introduced into experimental therapeutic protocols, the overall approach to treating advanced stage GC has not substantially changed. Currently, surgical resection with adjuvant or neoadjuvant radiotherapy and chemotherapy are the most effective treatments for this disease. Future research should not underestimate the heterogeneity of GC when developing diagnostic and therapeutic strategies aimed toward improving patient survival.

Identification and quantification of DNA repair protein poly(ADP ribose) polymerase 1 (PARP1) in human tissues and cultured cells by liquid chromatography/isotope-dilution tandem mass spectrometry

Poly(ADP ribose) polymerase 1 (PARP1) is a multifunctional DNA repair protein of the base excision repair pathway and plays a major role in the repair of DNA strand breaks and in replication and transcriptional regulation among other functions. Mounting evidence points to the predictive and prognostic value of PARP1 expression in human cancers. Thus, PARP1 has become an important target in cancer therapy, leading to the development of inhibitors as anticancer drugs. In the past, PARP1 expression levels in tissue samples have generally been estimated by indirect and semi-quantitative immunohistochemical methods. Accurate measurement of PARP1 in normal tissues and malignant tumors of patients will be essential for evaluating PARP1 as a predictive and prognostic biomarker in cancer and other diseases, and for the development and use of its inhibitors in cancer therapy. In this work, we present an approach involving liquid chromatography-isotope-dilution tandem mass spectrometry to positively identify and accurately quantify PARP1 in human tissues and cultured cells. We identified and quantified PARP1 in human normal ovarian tissues and malignant ovarian tumors, and in three pairs of human cell lines, each pair consisting of a normal cell line and its cancerous counterpart. Significantly greater expression of PARP1 was observed in malignant ovarian tissues than in normal ovarian tissues. In the case of one pair of cell lines, the cancerous cell line also exhibited greater expression of PARP1 than in normal cell line. We also show the simultaneous measurement of PARP1 and apurinic/apyrimidinic endonuclease 1 (APE1) in a given protein extract. The approach presented in this work is expected to contribute to the accurate quantitative assessment of PARP1 levels in basic research and clinical studies.

PARP-1 Overexpression as an Independent Prognostic Factor in Adult Non-M3 Acute Myeloid Leukemia

AIMS

Poly (ADP-ribose) polymerase-1 (PARP-1) plays an important role in the repair of damaged DNA and has prognostic significance in a variety of human malignancies. However, little is known about its expression levels and clinical implication in patients with acute myeloid leukemia (AML).

MATERIALS AND METHODS

Quantitative reverse transcription-polymerase chain reaction was done to evaluate PARP-1 expression levels in the bone marrow of 65 patients with non-M3 AML and 54 healthy counterparts. The correlation of PARP-1 expression with clinicopathological features of non-M3 AML patients was also analyzed.

RESULTS

Non-M3 AML patients have higher PARP-1 expression than the healthy controls (p < 0.01). Patients with adverse cytogenetic risk have higher PARP-1 expression than other cytogenetic risk groups (p = 0.004). The PARP-1 median expression level divided AML patients into PARP-1 low-expressed and PARP-1 high-expressed groups. High expression levels of PARP-1 were associated with worse overall survival (OS) (p = 0.01) and relapse-free survival (RFS) (p = 0.005). Moreover, multivariate analysis revealed that high PARP-1 expression was an independent risk factor for both OS and RFS.

CONCLUSIONS

Our results suggest that PARP-1 overexpression may define an important risk factor in non-M3 AML patients and PARP-1 is a potential therapeutic target for AML treatment.

The Association between PARP1 and LIG3 Expression Levels and Chromosomal Translocations in Acute Myeloid Leukemia Patients

OBJECTIVES

Chromosomal translocations are among the most common mutational events in cancer development, especially in hematologic malignancies. However, the precise molecular mechanism of these events is still not clear. It has been recently shown that alternative non-homologous end-joining (alt-NHEJ), a newly described pathway for double-stranded DNA break repair, mediates the formation of chromosomal translocations. Here, we examined the expression levels of the main components of alt-NHEJ (PARP1 and LIG3) in acute myeloid leukemia (AML) patients and assessed their potential correlation with the formation of chromosomal translocations.

MATERIALS AND METHODS

This experimental study used reverse transcription-quantitative polymerase chain reaction (RTqPCR) to quantify the expression levels of PARP1 and LIG3 at the transcript level in AML patients (n=78) and healthy individuals (n=19).

RESULTS

PARP1 was the only gene overexpressed in the AML group when compared with healthy individuals (P=0.0004), especially in the poor prognosis sub-group. Both genes were, however, found to be up-regulated in AML patients with chromosomal translocations (P=0.04 and 0.0004 respectively). Moreover, patients with one isolated translocation showed an over-expression of only LIG3 (P=0.005), whereas those with two or more translocations over-expressed both LIG3 (P=0.002) and PARP1 (P=0.02).

CONCLUSIONS

The significant correlations observed between PARP1 and LIG3 expression and the rate of chromosomal translocations in AML patients provides a molecular context for further studies to investigate the causality of this association.

A phase 1 dose-escalation study of veliparib with bimonthly FOLFIRI in patients with advanced solid tumours

Background

Veliparib is a potent poly(ADP-ribose) polymerase inhibitor. This phase 1 study aimed to establish the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of veliparib combined with various FOLFIRI regimens in patients with solid tumours.

Methods

Patients received veliparib (10–270 mg BID, days 1–5, 15–19) and FOLFIRI (days 1–3, 15–17) in three regimens containing 5-fluorouracil 2,400 mg/m²: irinotecan 150 mg/m² and folinic acid 400 mg/m² (part 1); irinotecan 180 mg/m², folinic acid 400 mg/m², and 5-fluorouracil 400 mg/m² bolus (part 2), or irinotecan 180 mg/m² (part 3). The RP2D was further evaluated in safety expansion cohorts. Preliminary antitumour activity was also assessed.

Results

Ninety-two patients received ≥1 veliparib dose. MTD was not reached; RP2D was set at 200 mg BID veliparib plus FOLFIRI (without 5-fluorouracil bolus). Most common treatment-emergent adverse events were neutropenia (66.3%), diarrhoea, and nausea (60.9% each). Dose-limiting toxicities (n = 4) were grade 3 gastritis and grade 4 neutropenia and febrile neutropenia. Veliparib exposure was dose-proportional, with no effects on the pharmacokinetics of FOLFIRI components. Fifteen patients had a partial response (objective response rate, 17.6%).

Conclusions

The acceptable safety profile and preliminary antitumour activity of veliparib plus FOLFIRI support further evaluation of this combination.

Poly-(ADP-Ribose) Polymerase-1 Promotes Prothrombin Gene Transcription and Produces Des-Gamma-Carboxy Prothrombin in Hepatocellular Carcinoma

BACKGROUND AND AIM

Although des-gamma-carboxy prothrombin (DCP) is a well-known tumor marker for hepatocellular carcinoma (HCC), the mechanism of DCP production is unclear. This study aimed to investigate the mechanism how DCP is produced in HCC cells.

METHODS

Levels of mRNA and DCP were analyzed by real-time polymerase chain reaction and electro-chemiluminescence immunoassay respectively. Secreted alkaline phosphatase (SEAP) expression vectors including deletion mutants of the prothrombin gene promoter were constructed for reporter gene assay. The transcription factors bound to DNA fragments were analyzed by mass spectrometry. An electrophoretic mobility shift assay (EMSA) was performed using a biotin end-labeled DNA.

RESULTS

The prothrombin mRNA levels in all 5 DCP producing cell lines were appreciably high. However, those in 2 DCP non-producing cell lines were below detectable levels. A SEAP vector with -2985 to +27 showed a very high transcription activity in DCP-producing Huh-1 cells. However, transcription abruptly decreased when the vector with -2955 to +27 was transfected, and then remained at the similar levels with larger deletion mutants, indicating the existence of a cis-element at -2985 to -2955 (31-bp). Mass spectrometry analysis identified the protein that bound to the 31-bp DNA as poly-(ADP-ribose) polymerase-1 (PARP-1). Knockdown of the PARP-1 gene by small interfering RNA in Huh-1 cells induced marked inhibition of prothrombin gene transcription. The EMSA clearly showed that PARP-1 specifically binds to the 31-bp DNA fragment in the prothrombin gene promoter.

CONCLUSIONS

Our data suggest that PARP-1 activates prothrombin gene transcription and that the excessive prothrombin gene transcription induces DCP production in DCP-producing HCC cells.

Functional, Metabolic, and Dynamic Mitochondrial Changes in the Rat Cirrhosis-Hepatocellular Carcinoma Model and the Protective Effect of IFC-305

Background: Mitochondrion is an important metabolic and energetic organelle that regulates several cellular processes. Mitochondrial dysfunction has been related to liver diseases including hepatocellular carcinoma. As a result, the energetic demand is not properly supplied and mitochondrial morphologic changes have been observed, resulting in an altered metabolism. We previously demonstrated the chemopreventive effect of the hepatoprotector IFC-305. Aim: In this work we aimed to evaluate the functional, metabolic, and dynamic mitochondrial alterations in the sequential model of cirrhosis-hepatocellular carcinoma induced by diethylnitrosamine in rats and the possible beneficial effect of IFC-305. Methods: Experimental groups of rats were formed to induce cirrhosis-hepatocellular carcinoma and to assess the IFC-305 effect during cancer development and progression through the evaluation of functional, metabolic, and dynamic mitochondrial parameters. Results: In this experimental model, dysfunctional mitochondria were observed and suspension of the diethylnitrosamine treatment was not enough to restore them. Administration of IFC-305 maintained and restored the mitochondrial function and regulated parameters implicated in metabolism as well as the mitochondrial dynamics modified by diethylnitrosamine intoxication. Conclusion: This study supports IFC-305 as a potential hepatocellular carcinoma treatment or as an adjuvant in chemotherapy.

Effectiveness and safety of poly (ADP-ribose) polymerase inhibitors in cancer therapy: A systematic review and meta-analysis

Poly (ADP-ribose) polymerase (PARP) inhibitors are a class of small-molecule drugs suppressing PARP enzymes activity, inducing the death of cells deficient in homologous recombination repair (HRR). HRR deficiency is common in tumor cells with BRCA gene mutation. Since their first clinical trial in 2003, PARP inhibitors have shown benefit in the treatment of HRR-deficient tumors. Recently, several randomized clinical trials (RCTs) have been conducted to investigate the potential benefit of administration of PARP inhibitors in cancer patients. However, the results remain controversial. To evaluate the efficiency and safety of PARP inhibitors in patients with cancer, we performed a comprehensive meta-analysis of RCTs. According to our study, PARP inhibitors could clearly improve progression-free survival (PFS), especially in patients with BRCA mutation. However, our study showed no significant difference in overall survival (OS) between the PARP inhibitors and controls, even in the BRCA mutation group. Little toxicity was reported in the rate of treatment correlated adverse events (AEs) in PARP inhibitor group compared with controls. In conclusion, PARP inhibitors do well in improving PFS with little toxicity, especially in patients with BRCA deficiency.

PET of Poly (ADP-Ribose) Polymerase Activity in Cancer: Preclinical Assessment and First In-Human Studies

Purpose To demonstrate that positron emission tomography (PET) with fluorine 18 (¹⁸F) fluorthanatrace (FTT) depicts activated poly (adenosine diphosphate-ribose)polymerase (PARP) expression and is feasible for clinical trial evaluation. Materials and Methods All studies were conducted prospectively from February 2012 through July 2015 under protocols approved by the local animal studies committee and institutional review board. The area under the receiver operating characteristic curve (AUC, in g/mL· min) for ¹⁸F-FTT was assessed in normal mouse organs before and after treatment with olaparib (n = 14), a PARP inhibitor, or iniparib (n = 11), which has no PARP inhibitory activity. Murine biodistribution studies were performed to support human translational studies. Eight human subjects with cancer and eight healthy volunteers underwent imaging to verify the human radiation dosimetry of ¹⁸F-FTT. The Wilcoxon signed rank test was used to assess for differences among treatment groups for the mouse studies. Results In mice, olaparib, but not iniparib, significantly reduced the ¹⁸F-FTT AUC in the spine (median difference before and after treatment and interquartile range [IQR]: -17 g/mL· min and 10 g/mL · min, respectively [P = .0001], for olaparib and -3 g/mL · min and 13 g/mL · min [P = .70] for iniparib) and in nodes (median difference and interquartile range [IQR] before and after treatment: -23 g/mL · min and 13 g/mL · min [P = .0001] for olaparib; -9 g/mL · min and 17 g/mL · min [P = .05] for iniparib). The effective dose was estimated at 6.9 mSv for a 370-MBq ¹⁸F-FTT dose in humans. In humans, the organs with the highest uptake on images were the spleen and pancreas. Among five subjects with measurable tumors, increased ¹⁸F-FTT uptake was seen in one subject with pancreatic adenocarcinoma and another with liver cancer. Conclusion The results suggest that ¹⁸F-FTT uptake reflects PARP expression and that its radiation dosimetry profile is compatible with those of agents currently in clinical use. ^© RSNA, 2016 Online supplemental material is available for this article.

Inhibition of poly(ADP-ribose) polymerase 1 protects against acute myeloid leukemia by suppressing the myeloproliferative leukemia virus oncogene

An abnormal expression of poly(ADP-ribose) polymerase 1 (PARP-1) has been described in many tumors. PARP-1 promotes tumorigenesis and cancer progression by acting on different molecular pathways. PARP-1 inhibitors can be used with radiotherapy or chemotherapy to enhance the susceptibility of tumor cells to the treatment. However, the specific mechanism of PARP-1 in acute myeloid leukemia (AML) remains unknown. Our study showed that expression of PARP-1 was upregulated in AML patients. PARP-1 inhibition slowed AML cell proliferation, arrested the cell cycle, induced apoptosis in vitro and improved AML prognosis in vivo. Mechanistically, microarray assay of AML cells with loss of PARP-1 function revealed that the myeloproliferative leukemia virus oncogene (MPL) was significantly downregulated. In human AML samples, MPL expression was increased, and gain-of-function and loss-of-function analysis demonstrated that MPL promoted cell growth. Moreover, PARP-1 and MPL expression were positively correlated in AML samples, and their overexpression was associated with an unfavorable prognosis. Furthermore, PARP-1 and MPL consistently acted on Akt and ERK1/2 pathways, and the anti-proliferative and pro-apoptotic function observed with PARP-1 inhibition were reversed in part via MPL activation upon thrombopoietin stimulation or gene overexpression. These data highlight the important function of PARP-1 in the progression of AML, which suggest PARP-1 as a potential target for AML treatment.

Interaction of hepatitis B virus X protein with PARP1 results in inhibition of DNA repair in hepatocellular carcinoma

Hepatitis B virus X protein (HBx) contributes to the development of hepatocellular carcinoma (HCC), probably by regulating activities of many host or viral proteins through protein-protein interactions. In this study, we identified poly(ADP-ribose) polymerase (PARP1), a crucial factor in DNA repair, as an HBx-interacting protein using a proteomics approach. Coimmunoprecipitation and proximity ligation assays confirmed the binding and colocalization of HBx and PARP1 in the nucleus. The carboxyl-terminus of HBx protein bound to the catalytic domain of PARP1, and this binding reduced the enzymatic activity of PARP1 in both in vitro and in vivo assays. HBx interrupted the binding of PARP1 to Sirt6, which catalyzes the mono-ADP-ribosylation required for DNA repair. Consistently, overexpression of HBx inhibited the clearance of γH2AX DNA repair foci generated under oxidative stress in Chang liver cells. Recruitment of the DNA repair complex to the site-specific double-strand breaks was inhibited in the presence of HBx, when measured by laser microirradiation assay and damage-specific chromatin immunoprecipitation assays. Consequently, HBx increased signs of DNA damage such as accumulation of 8-hydroxy-2'-deoxyguanosine and comet formation, which were reversed by overexpression of PARP1 and/or Sirt6. Finally, the interaction between PARP1 and Sirt6 was markedly lower in the livers of HBx-transgenic mice and specimens obtained from HCC patients to compare with the corresponding control. Our data suggest that the physical interaction of HBx and PARP1 accelerates DNA damage by inhibiting recruitment of the DNA repair complex to the damaged DNA sites, which may lead to the onset of hepatocarcinogenesis.

Phase II study of temozolomide and veliparib combination therapy for sorafenib-refractory advanced hepatocellular carcinoma

Purpose

To determine the antitumor efficacy and tolerability of combination temozolomide (TMZ) and veliparib (ABT-888) in patients with advanced, sorafenib-refractory hepatocellular carcinoma (HCC).

Methods

This single-arm phase II trial enrolled patients with pathologically confirmed, sorafenib-refractory HCC. All patients received 40 mg ABT-888 PO daily on days 1–7 and 150 mg/m² TMZ PO daily on days 1–5 of a 28-day cycle. The primary endpoint was objective response rate (ORR) at 2 months. Secondary endpoints included overall survival (OS), progression-free survival (PFS), and toxicity profile. Tumor response was assessed every 2 cycles using RECIST criteria, and toxicities were assessed using CTCAE v4.03.

Results

We enrolled 16 patients in the first phase of the trial, but the study was discontinued due to a poor ORR; only four patients (25 %) had SD after 2 cycles. Twelve patients (75 %) were taken off study after 2 months of treatment; 10 of these had disease progression. Two patients (13 %) were taken off study due to severe toxicity, and one patient (6 %) died from non-treatment-related liver failure. One patient had SD for 16 months, receiving 11 cycles of therapy before being taken off study. The most common grade 3 treatment-related toxicities included vomiting (n = 2), thrombocytopenia (n = 2), nausea (n = 1), and anemia (n = 1). The median PFS was 1.9 months, and median OS was 13.1 months.

Conclusion

The combination of TMZ and ABT-888 is well tolerated in patients with advanced HCC. However, the regimen failed to show survival benefit.

ClinicalTrials.gov Identifier

NCT01205828.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-015-2852-2) contains supplementary material, which is available to authorized users.

Trial watch - inhibiting PARP enzymes for anticancer therapy

Poly(ADP-ribose) polymerases (PARPs) are a members of family of enzymes that catalyze poly(ADP-ribosyl)ation (PARylation) and/or mono(ADP-ribosyl)ation (MARylation), two post-translational protein modifications involved in crucial cellular processes including (but not limited to) the DNA damage response (DDR). PARP1, the most abundant family member, is a nuclear protein that is activated upon sensing distinct types of DNA damage and contributes to their resolution by PARylating multiple DDR players. Recent evidence suggests that, along with DDR, activated PARP1 mediates a series of prosurvival and proapoptotic processes aimed at preserving genomic stability. Despite this potential oncosuppressive role, upregulation and/or overactivation of PARP1 or other PARP enzymes has been reported in a variety of human neoplasms. Over the last few decades, several pharmacologic inhibitors of PARP1 and PARP2 have been assessed in preclinical and clinical studies showing potent antineoplastic activity, particularly against homologous recombination (HR)-deficient ovarian and breast cancers. In this Trial Watch, we describe the impact of PARP enzymes and PARylation in cancer, discuss the mechanism of cancer cell killing by PARP1 inactivation, and summarize the results of recent clinical studies aimed at evaluating the safety and therapeutic profile of PARP inhibitors in cancer patients.

Supplementation of nicotinic acid with NAMPT inhibitors results in loss of in vivo efficacy in NAPRT1-deficient tumor models

Nicotinamide adenine dinucleotide (NAD) is a metabolite essential for cell survival and generated de novo from tryptophan or recycled from nicotinamide (NAM) through the nicotinamide phosphoribosyltransferase (NAMPT)-dependent salvage pathway. Alternatively, nicotinic acid (NA) is metabolized to NAD through the nicotinic acid phosphoribosyltransferase domain containing 1 (NAPRT1)-dependent salvage pathway. Tumor cells are more reliant on the NAMPT salvage pathway making this enzyme an attractive therapeutic target. Moreover, the therapeutic index of NAMPT inhibitors may be increased by in NAPRT-deficient tumors by NA supplementation as normal tissues may regenerate NAD through NAPRT1. To confirm the latter, we tested novel NAMPT inhibitors, GNE-617 and GNE-618, in cell culture- and patient-derived tumor models. While NA did not protect NAPRT1-deficient tumor cell lines from NAMPT inhibition in vitro, it rescued efficacy of GNE-617 and GNE-618 in cell culture- and patient-derived tumor xenografts in vivo. NA co-treatment increased NAD and NAM levels in NAPRT1-deficient tumors to levels that sustained growth in vivo. Furthermore, NAM co-administration with GNE-617 led to increased tumor NAD levels and rescued in vivo efficacy as well. Importantly, tumor xenografts remained NAPRT1-deficient in the presence of NA, indicating that the NAPRT1-dependent pathway is not reactivated. Protection of NAPRT1-deficient tumors in vivo may be due to increased circulating levels of metabolites generated by mouse liver, in response to NA or through competitive reactivation of NAMPT by NAM. Our results have important implications for the development of NAMPT inhibitors when considering NA co-treatment as a rescue strategy.

PARP1 expression in mantle cell lymphoma: the utility of PARP1 immunohistochemistry and its relationship with markers of DNA damage

Mantle cell lymphoma (MCL) is an aggressive disease with poor overall survival, attributable in part to frequent defects of the DNA repair genes. In such malignancies, additional inhibition of the ubiquitous DNA damage repair protein, poly-ADP ribose polymerase-1 (PARP1) has shown enhanced cytotoxicity (so-called synthetic lethality). We studied PARP1 expression in a series of clinical cases of MCL, with the secondary aim to ascertain the relationship between PARP1 expression and DNA repair gene expression (namely ATM and p53) by immunohistochemical methods. We also examined the relationship between PARP1 expression and the well-established prognostic biomarker Ki-67, in addition to correlating PARP1 expression with the overall survival. From amongst our series of 79 unselected cases of MCL, we detected PARP1 expression in all but two cases with variable intensity. We also noted correlations between PARP1 expression and ATM and p53 expression. As described in previous studies, we identified a significant survival difference on the basis of Ki-67 and p53 expression. When digital H-score analysis of PARP1 expression was performed, there was a distinct survival advantage noted in patients with lower levels of expression. When our biomarker data were assessed by Cox regression, furthermore, the dominant effects of p53 and PARP1 expression were highlighted. Our data support the need for further research into the potential utility of PARP1 as a biomarker in MCL and for the potential direction of future PARP1 inhibitor-targeted therapy studies.

Parp-1 genetic ablation in Ela-myc mice unveils novel roles for Parp-1 in pancreatic cancer

Pancreatic cancer has a dismal prognosis and is currently the fourth leading cause of cancer-related death in developed countries. The inhibition of poly(ADP-ribose) polymerase-1 (Parp-1), the major protein responsible for poly(ADP-ribosy)lation in response to DNA damage, has emerged as a promising treatment for several tumour types. Here we aimed to elucidate the involvement of Parp-1 in pancreatic tumour progression. We assessed Parp-1 protein expression in normal, preneoplastic and pancreatic tumour samples from humans and from K-Ras- and c-myc-driven mouse models of pancreatic cancer. Parp-1 was highly expressed in acinar cells in normal and cancer tissues. In contrast, ductal cells expressed very low or undetectable levels of this protein, both in a normal and in a tumour context. The Parp-1 expression pattern was similar in human and mouse samples, thereby validating the use of animal models for further studies. To determine the in vivo effects of Parp-1 depletion on pancreatic cancer progression, Ela-myc-driven pancreatic tumour development was analysed in a Parp-1 knock-out background. Loss of Parp-1 resulted in increased tumour necrosis and decreased proliferation, apoptosis and angiogenesis. Interestingly, Ela-myc:Parp-1(-/-) mice displayed fewer ductal tumours than their Ela-myc:Parp-1(+/+) counterparts, suggesting that Parp-1 participates in promoting acinar-to-ductal metaplasia, a key event in pancreatic cancer initiation. Moreover, impaired macrophage recruitment can be responsible for the ADM blockade found in the Ela-myc:Parp-1(-/-) mice. Finally, molecular analysis revealed that Parp-1 modulates ADM downstream of the Stat3-MMP7 axis and is also involved in transcriptional up-regulation of the MDM2, VEGFR1 and MMP28 cancer-related genes. In conclusion, the expression pattern of Parp-1 in normal and cancer tissue and the in vivo functional effects of Parp-1 depletion point to a novel role for this protein in pancreatic carcinogenesis and shed light into the clinical use of Parp-1 inhibitors.

Update on hepatocellular carcinoma breakthroughs: poly(ADP-ribose) polymerase inhibitors as a promising therapeutic strategy

Hepatocellular carcinoma is the most common form of primary liver cancer which is the fifth most common cancer in men and the seventh in women and the third most common cause of cancer-related death worldwide. Only 10-20% of patients are eligible for curative treatments that result in a 5-year survival rate of 40% to 70%. Therefore, the development of novel treatment options is necessary for the majority of patients and remains a considerable challenge. Conformal radiotherapy is used in certain circumstances and preliminary data obtained from phase 1/2 trials are showing promising curative effects. There is thus an interest in identifying drugs that can be exploited to enhance radiation sensitivity that could be used in therapy and might improve clinical outcome. Small molecules inhibitors of poly(ADP-ribose) polymerases (PARP) are an example of a radio- and chemo-sensitizing drug, as well as being an efficient single agent treatment in certain genetic backgrounds. In this review, we discuss the role of PARP-1 in hepatocellular carcinoma and present the results of preclinical studies that have assessed the potential of PARP inhibition as a single treatment or combined with chemotherapy or radiotherapy for the treatment of hepatocellular carcinoma.

Review of poly (ADP-ribose) polymerase (PARP) mechanisms of action and rationale for targeting in cancer and other diseases

Poly (ADP-ribose) polymerases (PARPs) are a family of related enzymes that share the ability to catalyze the transfer of ADP-ribose to target proteins. PARPs play an important role in various cellular processes, including modulation of chromatin structure, transcription, replication, recombination, and DNA repair. The role of PARP proteins in DNA repair is of particular interest, in view of the finding that certain tumors defective in homologous recombination mechanisms, may rely on PARP-mediated DNA repair for survival, and are sensitive to its inhibition. PARP inhibitors may also increase tumor sensitivity to DNA-damaging agents. Clinical trials of PARP inhibitors are investigating the utility of these approaches in cancer. The hyperactivation of PARP has also been shown to result in a specific programmed cell death pathway involving NAD+/ATP depletion, mu-calpain activation, loss of mitochondrial membrane potential, and the release of apoptosis inducing factor. Hyperactivation of the PARP pathway may be exploited to selectively kill cancer cells. Other PARP forms, including tankyrase 1 (PARP 5a), which plays an important role in enhancing telomere elongation by telomerase, have been found to be potential targets in cancer therapy. The PARP pathway and its inhibition thus offers a number of opportunities for therapeutic intervention in both cancer and other disease states.

New opportunities in chemosensitization and radiosensitization: modulating the DNA-damage response

Many current cancer treatments, including certain classes of chemotherapeutics and radiation, induce cytotoxicity by damaging DNA. However, many cancers are resistant to these therapies, which represents a significant challenge in the clinic. Thus, modulating DNA-damage responses to selectively enhance the sensitivity of cancer cells to these therapies is highly desirable. When DNA damage is detected, DNA checkpoint mechanisms are activated to halt cells at various phases of the cell cycle. Simultaneously, DNA-damage sensors transduce signals to activate DNA-repair mechanisms via de novo expression or post-translational modification of enzymes required for DNA repair. p53 is the major player in a checkpoint that arrests cells at the G1/S boundary, while checkpoint kinase (Chk)1 is critical for the G2/M checkpoint and also the S checkpoint that prevents cell cycle progression after replication defects (intra-S-phase checkpoint) or S/M uncoupling (S/M checkpoint). Poly(ADP-ribose) polymerase is involved in sensing DNA single-strand breaks and inducing DNA repair via poly(ADP-ribosyl)ating various DNA-binding and DNA-repair proteins. In this review, strategies for implementing small-molecule inhibitors of poly(ADP-ribose) polymerase and Chk1, which are emerging as potential adjuncts to current therapies, are discussed.

Nicotinamide phosphoribosyltransferase inhibitors, design, preparation, and structure-activity relationship

Existing pharmacological inhibitors for nicotinamide phosphoribosyltransferase (NAMPT) are promising therapeutics for treating cancer. By using medicinal and computational chemistry methods, the structure-activity relationship for novel classes of NAMPT inhibitors is described, and the compounds are optimized. Compounds are designed inspired by the NAMPT inhibitor APO866 and cyanoguanidine inhibitor scaffolds. In comparison with recently published derivatives, the new analogues exhibit an equally potent antiproliferative activity in vitro and comparable activity in vivo. The best performing compounds from these series showed subnanomolar antiproliferative activity toward a series of cancer cell lines (compound 15: IC50 0.025 and 0.33 nM, in A2780 (ovarian carcinoma) and MCF-7 (breast), respectively) and potent antitumor in vivo activity in well-tolerated doses in a xenograft model. In an A2780 xenograft mouse model with large tumors (500 mm(3)), compound 15 reduced the tumor volume to one-fifth of the starting volume at a dose of 3 mg/kg administered ip, bid, days 1-9. Thus, compounds found in this study compared favorably with compounds already in the clinic and warrant further investigation as promising lead molecules for the inhibition of NAMPT.

Translocation t(11;14) (q13;q32) and genomic imbalances in multi-ethnic multiple myeloma patients: a Malaysian study

More than 50% of myeloma cases have normal karyotypes under conventional cytogenetic analysis due to low mitotic activity and content of plasma cells in the bone marrow. We used a polymerase chain reaction (PCR)-based translocation detection assay to detect BCL1/JH t(11;14) (q13;q32) in 105 myeloma patients, and randomly selected 8 translocation positive samples for array comparative genomic hybridization (aCGH) analysis. Our findings revealed 14.3% of myeloma samples were positive for BCL1/JH t(11;14) (q13;q32) translocation (n=15 of 105). We found no significant correlation between this translocation with age (P=0.420), gender (P=0.317), ethnicity (P=0.066) or new/relapsed status of multiple myeloma (P=0.412) at 95% confidence interval level by χ²test. In addition, aCGH results showed genomic imbalances in all samples analyzed. Frequent chromosomal gains were identified at regions 1q, 2q, 3p, 3q, 4p, 4q, 5q, 7q, 9q, 11q, 13q, 15q, 21q, 22q and Xq, while chromosomal losses were detected at 4q and 14q. Copy number variations at genetic loci that contain NAMPT, IVNS1ABP and STK17B genes are new findings that have not previously been reported in myeloma patients. Besides fluorescence in situ hybridization, PCR is another rapid, sensitive and simple technique that can be used for detecting BCL1/JH t(11;14)(q13;q32) translocation in multiple myeloma patients. Genes located in the chromosomal aberration regions in our study, such as NAMPT, IVNS1ABP, IRF2BP2, PICALM, STAT1, STK17B, FBXL5, ACSL1, LAMP2, SAMSN1 and ATP8B4 might be potential prognostic markers and therapeutic targets in the treatment and management of multiple myeloma patients positive for BCL1/JH t(11;14) (q13;q32) translocation.

Upregulation of Poly (ADP-Ribose) Polymerase-1 (PARP1) in Triple-Negative Breast Cancer and Other Primary Human Tumor Types

Poly (ADP-ribose) polymerase-1 (PARP1) is a key facilitator of DNA repair and is implicated in pathways of tumorigenesis. PARP inhibitors have gained recent attention as rationally designed therapeutics for the treatment of several malignancies, particularly those associated with dysfunctional DNA repair pathways, including triple-negative breast cancer (TNBC). We investigated the PARP1 gene expression profile in surgical samples from more than 8,000 primary malignant and normal human tissues. PARP1 expression was found to be significantly increased in several malignant tissues, including those isolated from patients with breast, uterine, lung, ovarian, and skin cancers, and non-Hodgkin's lymphoma. Within breast infiltrating ductal carcinoma (IDC) samples tested, mean PARP1 expression was significantly higher relative to normal breast tissue, with over 30% of IDC samples demonstrating upregulation of PARP1, compared with 2.9% of normal tissues. Because of known DNA repair defects, including BRCA1 dysfunction, associated with TNBC, exploration of PARP1 expression in breast cancers related to expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) led to the observation that negative expression of any of the 3 receptors was associated with upregulation of PARP1 expression, compared with receptor-positive tissues. To validate these observations, an independent set of breast adenocarcinomas was evaluated and demonstrated >2-fold upregulation of PARP1 in approximately 70% of primary breast adenocarcinomas, including TNBC, compared with syngeneic nonmalignant breast tissues. Immunohistochemistry (IHC) showed that upregulation of the PARP1 gene was consistent with increased protein expression in TNBC. These analyses suggest a potential biological role for PARP1 in several distinct malignancies, including TNBC. Further investigation of PARP1 as a biomarker for the therapeutic activity of PARP inhibitor-based therapy is warranted.

Target enzyme mutations are the molecular basis for resistance towards pharmacological inhibition of nicotinamide phosphoribosyltransferase

Background

Inhibitors of nicotinamide phosphoribosyltransferase (NAMPT) are promising cancer drugs currently in clinical trials in oncology, including APO866, CHS-828 and the CHS-828 prodrug EB1627/GMX1777, but cancer cell resistance to these drugs has not been studied in detail.

Methods

Here, we introduce an analogue of CHS-828 called TP201565 with increased potency in cellular assays. Further, we describe and characterize a panel of cell lines with acquired stable resistance towards several NAMPT inhibitors of 18 to 20,000 fold compared to their parental cell lines.

Results

We find that 4 out of 5 of the resistant sublines display mutations of NAMPT located in the vicinity of the active site or in the dimer interface of NAMPT. Furthermore, we show that these mutations are responsible for the resistance observed. All the resistant cell lines formed xenograft tumours in vivo. Also, we confirm CHS-828 and TP201565 as competitive inhibitors of NAMPT through docking studies and by NAMPT precipitation from cellular lysate by an analogue of TP201565 linked to sepharose. The NAMPT precipitation could be inhibited by addition of APO866.

Conclusion

We found that CHS-828 and TP201565 are competitive inhibitors of NAMPT and that acquired resistance towards NAMPT inhibitors can be expected primarily to be caused by mutations in NAMPT.

Poly(ADP-ribose) polymerase-1 polymorphisms, expression and activity in selected human tumour cell lines

Background:

Poly(ADP-ribose) polymerase-1 (PARP-1) is a DNA-binding enzyme activated by DNA breaks and involved in DNA repair and other cellular processes. Poly(ADP-ribose) polymerase activity can be higher in cancer than in adjacent normal tissue, but cancer predisposition is reported to be greater in individuals with a single-nucleotide polymorphism (SNP) V762A (T2444C) in the catalytic domain that reduces PARP-1 activity.

Methods:

To resolve these divergent observations, we determined PARP-1 polymorphisms, PARP-1 protein expression and activity in a panel of 19 solid and haematological, adult and paediatric human cancer cell lines.

Results:

There was a wide variation in PARP activity in the cell line panel (coefficient of variation, CV=103%), with the lowest and the highest activity being 2460 pmol PAR/10⁶ (HS-5 cells) and 85 750 pmol PAR/10⁶ (NGP cells). Lower variation (CV=32%) was observed in PARP-1 protein expression with the lowest expression being 2.0 ng μg⁻¹ (HS-5 cells) and the highest being 7.1 ng μg⁻¹ (ML-1 cells). The mean activity in the cancer cells was 45-fold higher than the mean activity in normal human lymphocytes and the PARP-1 protein levels were 23-fold higher.

Conclusions:

Surprisingly, there was no significant correlation between PARP activity and PARP-1 protein level or the investigated polymorphisms, T2444C and CA.

Potentiation of temozolomide cytotoxicity by poly(ADP)ribose polymerase inhibitor ABT-888 requires a conversion of single-stranded DNA damages to double-stranded DNA breaks

Poly(ADP-ribose) polymerase (PARP) senses DNA breaks and facilitates DNA repair via the polyADP-ribosylation of various DNA binding and repair proteins. We explored the mechanism of potentiation of temozolomide cytotoxicity by the PARP inhibitor ABT-888. We showed that cells treated with temozolomide need to be exposed to ABT-888 for at least 17 to 24 hours to achieve maximal cytotoxicity. The extent of cytotoxicity correlates with the level of double-stranded DNA breaks as indicated by gammaH2AX levels. In synchronized cells, damaging DNA with temozolomide in the presence of ABT-888 during the S phase generated high levels of double-stranded breaks, presumably because the single-stranded DNA breaks resulting from the cleavage of the methylated nucleotides were converted into double-stranded breaks through DNA replication. As a result, treatment of temozolomide and ABT-888 during the S phase leads to higher levels of cytotoxicity. ABT-888 inhibits poly(ADP-ribose) formation in vivo and enhances tumor growth inhibition by temozolomide in multiple models. ABT-888 is well tolerated in animal models. ABT-888 is currently in clinical trials in combination with temozolomide.

The adjuvant effects of Antrodia Camphorata extracts combined with anti-tumor agents on multidrug resistant human hepatoma cells

AIM OF THE STUDY

The objectives of this study were to investigate the adjuvant anti-tumor effects of Antrodia camphorate in human hepatoma cells (C3A and PLC/PRF/5) which are resistance to most anti-tumor agents, elucidate the possible regulation pathways, and measure the tumor growth and survival rate in xenograft-nude mice after combined with anti-tumor agents.

MATERIALS AND METHODS

The AC extracts were measured by using a phenol/sulfuric acid method as previously described. The in vitro cell proliferation assay of ACs and anti-tumor agents was tested on C3A and PLC/PRF/5 cell lines. The percentage of human hepatoma cells undergoing apoptosis and distributing in different phases of cell cycle were determined by Flow cytometric analysis. Western blot analysis for MDR-1 and apoptosis- related proteins. The measurements of tumor growth and survival analysis of hepatoma implanted nude mice treated with Antrodia camphorata extracts and anti-tumor agents alone or in combinations.

RESULTS

We have found that Antrodia camphorata extracts, when combined with anti-tumor agents, showed adjuvant antiproliferative effects on hepatoma cells (in vitro) and on xenografted cells in tumor-implanted nude mice (in vivo), which then extended their median survival days. Furthermore, solid-state extracts of Antrodia camphorata (AC-SS) showed its adjuvant effects through the inhibition of MDR gene expressions and the pathway of COX-2- dependent inhibition of p-AKT, which ultimately resulted in the induction of apoptosis in hepatoma cells.

CONCLUSIONS

In this study, we have found that Antrodia camphorata extract, when combined with anti-tumor agents, showed adjuvant antiproliferative effects on hepatoma cells (in vitro) and on xenografted cells in tumor-implanted nude mice (in vivo).

O Labeling for a Quantitative Proteomic Analysis of Glycoproteins in Hepatocellular Carcinoma

INTRODUCTION: Quantitative proteomics using tandem mass spectrometry is an attractive approach for identification of potential cancer biomarkers. Fractionation of complex tissue samples into subproteomes prior to mass spectrometric analyses increases the likelihood of identifying cancer-specific proteins that might be present in low abundance. In this regard, glycosylated proteins are an interesting class of proteins that are already established as biomarkers for several cancers. MATERIALS AND METHODS: In this study, we carried out proteomic profiling of tumor and adjacent non-cancer liver tissues from hepatocellular carcinoma (HCC) patients. Glycoprotein enrichment from liver samples using lectin affinity chromatography and subsequent (18)O/(16)O labeling of peptides allowed us to obtain relative abundance levels of lectin-bound proteins. As a complementary approach, we also examined the relative expression of proteins in HCC without glycoprotein enrichment. Lectin affinity enrichment was found to be advantageous to quantitate several interesting proteins, which were not detected in the whole proteome screening approach. We identified and quantitated over 200 proteins from the lectin-based approach. Interesting among these were fetuin, cysteine-rich protein 1, serpin peptidase inhibitor, leucine-rich alpha-2-glycoprotein 1, melanoma cell adhesion molecule, and heparan sulfate proteoglycan-2. Using lectin affinity followed by PNGase F digestion coupled to (18)O labeling, we identified 34 glycosylation sites with consensus sequence N-X-T/S. Western blotting and immunohistochemical staining were carried out for several proteins to confirm mass spectrometry results. CONCLUSION: This study indicates that quantitative proteomic profiling of tumor tissue versus non-cancerous tissue is a promising approach for the identification of potential biomarkers for HCC.

Stable depletion of poly (ADP-ribose) polymerase-1 reduces in vivo melanoma growth and increases chemosensitivity

Poly(ADP-ribose) polymerase (PARP)-1, which plays a key role in DNA repair, inflammation and transcription, has recently been shown to be involved in angiogenesis. The aim of this study was to investigate PARP-1 role in melanoma aggressiveness and chemoresistance in vivo using clones stably silenced for PARP-1 expression. Whilst the growth characteristics of PARP-1-deficient melanoma cells were comparable to those of PARP-1-proficient cells in vitro, their tumourigenic potential in vivo was significantly compromised. In fact, mice challenged intra-muscle with PARP-1-deficient cells showed a delayed development of measurable tumour nodules, which were also significantly reduced in size with respect to those of mice inoculated with PARP-1-proficient cells. Moreover, animals challenged intra-cranially with PARP-1-deficient cells, a model that mimics CNS localisation of melanoma, showed an increased survival. Immunohistochemical analyses of PARP-1-depleted melanoma grafts indicated a reduced expression of the angiogenesis marker PECAM-1/CD31 and of the pro-inflammatory mediators TNF-alpha and GITR. Notably, PARP-1-silenced melanoma was extremely sensitive to temozolomide, an anticancer agent used for the treatment of metastatic melanoma. These results provide novel evidence for a direct role of PARP-1 in tumour aggressiveness and chemoresistance.

Comparative proteomic analysis on human L-02 liver cells treated with varying concentrations of trichloroethylene

To determine the differential proteomic expressions in human L-02 liver cells induced by varying concentrations of trichloroethylene (TCE), comparative proteomic analysis was performed on human L-02 liver cells which were treated with varying concentrations of TCE. According to the result of MTT test, we designed four different groups, in which the cells were treated with 0 microM (control group), 3, 10 or 40 microM TCE for 24 h, respectively. Comparative analysis of approximately 800 spots resolved by two-dimensional gel electrophoresis (2DE) in the soluble proteomes of L-02 cells from the four different groups resulted in 10 differential proteins. To identify the differential spots, matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) was carried out; if the results from the tool were insufficient, tandem MS (MALDI-TOF-TOF-MS) was then performed. The raw data of peptide mass fingerprints (PMFs) and MS/MS spectra were searched against the IPI human data base for exact matches. Then western blot was employed to verify the result of proteomic analysis, the following result confirmed that the results of proteomic analysis were reliable. These results might provide an insight into the underlying mechanism of TCE intoxication and find biological markers for diagnosis and therapy of TCE-induced diseases.

Anticancer agent CHS-828 inhibits cellular synthesis of NAD

Malignant cells display increased demands for energy production and DNA repair. Nicotinamide adenine dinucleotide (NAD) is required for both processes and is also continuously degraded by cellular enzymes. Nicotinamide phosphoribosyltransferase (Nampt) is a crucial factor in the resynthesis of NAD, and thus in cancer cell survival. Here, we establish the cytotoxic mechanism of action of the small molecule inhibitor CHS-828 to result from impaired synthesis of NAD. Initially, we detected cross-resistance in cells between CHS-828 and a known inhibitor of Nampt, FK866, a compound of a structurally different class. We then showed that nicotinamide protects against CHS-828-mediated cytotoxicity. Finally, we observed that treatment with CHS-828 depletes cellular NAD levels in sensitive cancer cells. In conclusion, these results strongly suggest that, like FK866, CHS-828 kills cancer cells by depleting NAD.

Poly(ADP-ribose) polymerase-1 regulates vimentin expression in lung cancer cells

Vimentin is one of the mammalian intermediate filament proteins. It is expressed in cells of mesenchymal origin and is characteristic of proliferating cells at the fetal stage. During malignancy, vimentin expression is activated in certain lung epithelial cells. Examination of a group of lung cancer cells showed a marked difference in their vimentin expression. The difference in vimentin expression among lung cancer cells is due to differential regulation at the transcriptional level. Analysis of the vimentin promoter revealed a 102-bp promoter sequence that is important for promoter activity in a lung cancer cell line in which vimentin is strongly expressed. This promoter region interacts with poly(ADP-ribose) polymerase-1 (PARP-1), which is also a transcription regulator. Exogenous expression of PARP-1 increased vimentin promoter activity. A shortened PARP-1 without the COOH-terminal catalytic domain showed the same promoter activation effect. Treatment of cells with H(2)O(2) reduced PARP-1 and vimentin expression at the protein level. H(2)O(2) also dose dependently suppressed vimentin promoter activity in cells overexpressing PARP-1. These results demonstrate that vimentin expression in lung cancer cells is regulated at the transcriptional level and that PARP-1 binds and activates the vimentin promoter independent of its catalytic domain and may play a role in H(2)O(2)-induced inhibition of vimentin expression.