Adenoviral-mediated gene transfer of Gadd45a results in suppression by inducing apoptosis and cell cycle arrest in pancreatic cancer cell

Molecular Screening for Nigericin Treatment in Pancreatic Cancer by High-Throughput RNA Sequencing

Objectives: Nigericin, an antibiotic derived from Streptomyces hygroscopicus, has been proved to exhibit promising anti-cancer effects on a variety of cancers. Our previous study investigated the potential anti-cancer properties in pancreatic cancer (PC), and demonstrated that nigericin could inhibit the cell viabilities in concentration- and time-dependent manners via differentially expressed circular RNAs (circRNAs). However, the knowledge of nigericin associated with long non-coding RNA (lncRNA) and mRNA in pancreatic cancer (PC) has not been studied. This study is to elucidate the underlying mechanism from the perspective of lncRNA and mRNA.

Methods: The continuously varying molecules (lncRNAs and mRNAs) were comprehensively screened by high-throughput RNA sequencing.

Results: Our data showed that 76 lncRNAs and 172 mRNAs were common differentially expressed in the nigericin anti-cancer process. Subsequently, the bioinformatics analyses, including Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, coding and non-coding co-expression network, cis- and trans-regulation predictions and protein-protein interaction (PPI) network, were applied to annotate the potential regulatory mechanisms among these coding and non-coding RNAs during the nigericin anti-cancer process.

Conclusions: These findings provided new insight into the molecular mechanism of nigericin toward cancer cells, and suggested a possible clinical application in PC.

GADD45α-targeted suicide gene therapy driven by synthetic CArG promoter E9NS sensitizes NSCLC cells to cisplatin, resveratrol, and radiation regardless of p53 status

Background: GADD45α is a tumor suppressor protein often upregulated by environmental stresses and DNA-damage agents to cause growth arrest, apoptosis, tumor growth inhibition, and anti-angiogenesis. A novel suicide gene therapy vector pE9NS.G45α was engineered by cloning GADD45α opening reading frame downstream to the synthetic CArG promoter E9NS, which contains nine repeats of CArG element with modified core A/T sequence and functions as a molecular switch to drive the expression of GADD45α. The current study aims to determine the efficacy of this suicide gene therapy vector in combination with cisplatin, resveratrol, and radiation in NSCLC cell lines with various p53 statuses. Methods: Three NSCLC cell lines, H1299 (deleted p53), A549 (wild-type p53), and H23 (mutated p53), were examined in the present investigation to represent NSCLC with different p53 functions. MTT assay was conducted to select suitable doses of cisplatin, resveratrol, and radiation for gene therapy, and dual luciferase assay was performed to validate the activation of promoter E9NS. The efficacy of gene therapy combinations was evaluated by the amount of GADD45α expression, cell survival, and apoptosis. Results: All the combinations successfully activated promoter E9NS to elevate intracellular GADD45α protein levels and subsequently enhanced cell viability reduction and apoptosis induction regardless of p53 status. Conclusion: Our study demonstrates that GADD45α-targeted suicide gene therapy controlled by synthetic promoter E9NS sensitizes NSCLC cells to cisplatin, resveratrol, and radiation and is effective against NSCLC at least in vitro.

Effects of low-intensity ultrasound combined with low-dose carboplatin in an orthotopic hamster model of tongue cancer: A preclinical study

Low-intensity ultrasound (LIUS) combined with chemotherapy is an innovative modality for cancer treatment, but its effect on orthotopic carcinoma remains unknown. Our previous study revealed that LIUS enhanced the growth inhibitory effects of several chemotherapeutic drugs in nude mice with transplanted tumors. In the present study, we used 7,12-dimethylbenz(alpha)anthracene to induce orthotopic tongue carcinogenesis in hamsters. We used the first-line chemotherapy drug for tongue cancer, carboplatin (CBP) in combination with LIUS to investigate the synergistic effect. The results revealed that LIUS combined with low-dose CBP enhanced the inhibitory effects of CBP on tumor growth, prolonged survival, and did not increase the incidence of side-effects. It also enhanced the inherent DNA damage caused by CBP, suppressed the expression of the DNA repair proteins O⁶-methylguanine DNA methyltransferase (MGMT) and Chk1, and increased the expression of DNA damage-inducible protein GADD45α. Furthermore, compared with CBP alone, LIUS combined with CBP reduced the expression of cyclin D1 and cyclin B1, induced the expression of caspase-3, cleaved caspase-3, caspase-8, Bax, and Bak, and inhibited the expression of Bcl-2. Examination of clinical samples revealed that MGMT, Chk1, and Gadd45α were higher in OTSCC than in adjacent normal tissue. Hence, our results indicated that LIUS enhanced the ability of low-dose CBP to damage DNA in an orthotopic hamster model of tongue cancer, induced apoptosis, inhibited tumor growth and progression, while it did not increase the toxic side-effects of the drug, suggesting additional clinical benefits for patients treated with the combination of CBP with LIUS.

Methylation mediated Gadd45β enhanced the chemosensitivity of hepatocellular carcinoma by inhibiting the stemness of liver cancer cells

Background

Defects of the growth arrest DNA damage-inducible gene 45β (Gadd45β) play an important role in the progression of tumor and confer resistance to chemotherapy. However, the role of Gadd45β in the apoptosis of hepatocellular carcinoma is still not clear. Purpose of this study was to explore the effect of Gadd45β on the apoptosis of liver cancer cells, and the possible mechanism was examined.

Result

In this study, we first confirmed the decreased expression of Gadd45β in human liver cancer tissues and human liver cancer cell lines, when compared to the peri-tumor liver tissue and normal liver cells. And, it was found that Gadd45β could inhibit the stemness of liver cancer cells, enhancing the apoptosis of cancer cells induced by chemotherapy. Furthermore, the results showed that HCC tissues and cell lines showed a higher methylation status in Gadd45β promoter than that in peri-tumor tissues and normal liver cells. Methylation was then reversed by pretreatment of SMMC-7721 and Hep-3B with 5-azacytidine which is the DNA methyltransferase inhibitor. And the 5-azacytidine decreased the stemness of SMMC-7721 and Hep-3B, enhanced the sensitivity of SMMC-7721 and Hep-3B to cisplatin.

Conclusions

Methylation mediated Gadd45β expression inhibited the stemness of liver cancer cells, promoting the chemotherapy-induced apoptosis. Thus Gadd45β may be the potential target for enhancing the chemosensitivity of human hepatocellular carcinoma.

GADD45A plays a protective role against temozolomide treatment in glioblastoma cells

Glioblastoma multiforme (GBM) is one of the most aggressive cancers. Despite recent advances in multimodal therapies, high-grade glioma remains fatal. Temozolomide (TMZ) is an alkylating agent used worldwide for the clinical treatment of GBM; however, the innate and acquired resistance of GBM limits its application. Here, we found that TMZ inhibited the proliferation and induced the G2/M arrest of GBM cells. Therefore, we performed microarrays to identify the cell cycle- and apoptosis-related genes affected by TMZ. Notably, GADD45A was found to be up-regulated by TMZ in both cell cycle and apoptosis arrays. Furthermore, GADD45A knockdown (GADD45A^kd) enhanced the cell growth arrest and cell death induced by TMZ, even in natural (T98) and adapted (TR-U373) TMZ-resistant cells. Interestingly, GADD45A^kd decreased the expression of O⁶-methylguanine-DNA methyltransferase (MGMT) in TMZ-resistant cells (T98 and TR-U373). In MGMT-deficient/TMZ-sensitive cells (U87 and U373), GADD45A^kd decreased TMZ-induced TP53 expression. Thus, in this study, we investigated the genes influenced by TMZ that were important in GBM therapy, and revealed that GADD45A plays a protective role against TMZ treatment which may through TP53-dependent and MGMT-dependent pathway in TMZ-sensitive and TMZ-resistant GBM, respectively. This protective role of GADD45A against TMZ treatment may provide a new therapeutic strategy for GBM treatment.

Antiproliferative activity of goniothalamin enantiomers involves DNA damage, cell cycle arrest and apoptosis induction in MCF-7 and HB4a cells

(R)-goniothalamin (R-GNT) is a styryl lactone that exhibits antiproliferative property against several tumor cell lines. (S)-goniothalamin (S-GNT) is the synthetic enantiomer of R-GNT, and their biological properties are poorly understood. The aim of this study was to evaluate the antiproliferative mechanisms of (R)-goniothalamin and (S)-goniothalamin in MCF-7 breast cancer cells and HB4a epithelial mammary cells. To determine the mechanisms of cell growth inhibition, we analyzed the ability of R-GNT and S-GNT to induce DNA damage, cell cycle arrest and apoptosis. Moreover, the gene expression of cell cycle components, including cyclin, CDKs and CKIs, as well as of genes involved in apoptosis and the DNA damage response were evaluated. The natural enantiomer R-GNT proved more effective in both cell lines than did the synthetic enantiomer S-GNT, inhibiting cell proliferation via cell cycle arrest and apoptosis induction, likely in response to DNA damage. The cell cycle inhibition caused by R-GNT was mediated through the upregulation of CIP/KIP cyclin-kinase inhibitors and through the downregulation of cyclins and CDKs. S-GNT, in turn, was able to cause G0/G1 cell cycle arrest and DNA damage in MCF-7 cells and apoptosis induction only in HB4a cells. Therefore, goniothalamin presents potent antiproliferative activity to breast cancer cells MCF-7. However, exposure to goniothalamin brings some undesirable effects to non-tumor cells HB4a, including genotoxicity and apoptosis induction.

CArG-driven GADD45α activated by resveratrol inhibits lung cancer cells

We report anticarcinogenic effects of suicide gene therapy that relies on the use of resveratrol-responsive CArG elements from the Egr-1 promoter to induce GADD45α. In A549 lung cancer cells, endogenous GADD45α was not induced upon resveratrol treatment. Therefore, induction of exogenous GADD45α resulted in growth inhibition. Resveratrol transiently induced Egr-1 through ERK/JNK-ElK-1. Hence, we cloned natural or synthetic Egr-1 promoter upstream of GADD45α cDNA to create a suicide gene therapy vector. Since natural promoter may have antagonized effects, we tested synthetic promoter that contains either five, six or nine repeats of CArG elements essential in the Egr-1 promoter to drive the expression of GADD45α upon resveratrol treatment. Further analysis confirmed that both synthetic promoter and natural Egr-1 promoter were able to “turn on” the expression of GADD45α when combined with resveratrol, and subsequently led to suppression of cell proliferation and apoptosis.

Overexpression of OLC1 promotes tumorigenesis of human esophageal squamous cell carcinoma

PURPOSE

OLC1 was recently identified to be a potential oncogene. However, the role of OLC1 in human esophageal cell carcinoma (ESCC) is unknown. The aim of this study was therefore to evaluate the expression of OLC1 in human ESCC from normal, premalignant, and malignant lesions, and to clarify the mechanisms by which OLC1 contributes to the progression of ESCC.

EXPERIMENTAL DESIGN

Two hundred and fourteen paired ESCC specimens, and an independent set from 28 ESCC patients, were used to analyze the correlation between OLC1 expression and the pathological characteristics of tumors using immunohistochemistry. Stable OLC1-overexpressing and OLC1-interfering esophageal cancer cells were established and a series of experimental methods were used to investigate the biological functions and mechanisms of action of OLC1.

RESULTS

We showed that OLC1 was overexpressed in 145 of 214 (67.8%) of human ESCC specimens, compared with in only 59 of 214 (27.57%) paired adjacent normal tissues (P<0.001). OLC1 overexpression occurred at a rate of 35% (10/28) at the stage of mild/moderate dysplasia, but was significantly upregulated to 66% (22/33) at the stages of severe dysplasia and in situ carcinoma, while 71% positive staining (22/28) was observed in invasive carcinoma tissues compared with normal tissues (P<0.05). We also provided evidence that OLC1 abnormalities significantly altered the cell proliferation and apoptosis induced by cytotoxic agents. OLC1 overexpression suppressed apoptosis, and was associated with attenuated caspase-3 activation and increased Bcl-2 stability.

CONCLUSION

Our study provides strong evidence suggesting OLC1 abnormalities may contribute to the development of human ESCC and have some important clinical significance.

Unraveling the effects of 1,25OH2D3 on global gene expression in pancreatic islets

INTRODUCTION

Vitamin D deficiency has been linked to type 1 and 2 diabetes, whereas supplementation may prevent both diseases. However, the extent of the effects of vitamin D or its metabolites directly on pancreatic islets is still largely unknown. The aim of the present study was to investigate how active vitamin D, 1,25(OH)2D3, affects beta cells directly by establishing its effects on global gene expression in healthy murine islets.

MATERIALS AND METHODS

Pancreatic islets were isolated from 2 to 3 week old C57BL/6 mice and cultured in vitro with 1,25(OH)2D3 or vehicle for 6 and 24h. Total RNA was extracted from the islets and the effects on global gene expression were analyzed using Affymetrix microarrays.

RESULTS AND DISCUSSION

Exposure to 1,25(OH)2D3 compared to vehicle resulted in 306 and 151 differentially expressed genes after 6 and 24h, respectively (n=4, >1.3-fold, p<0.02). Of these 220 were up-regulated, whereas 86 displayed a decreased expression after 6h. Furthermore, expression levels were increased for 124 and decreased for 27 genes following 24h of exposure. Formation of intercellular junctions, cytoskeletal organization, and intracellular trafficking as well as lipid metabolism and ion transport were among the most affected gene classes. Effects on several genes already identified as being part of vitamin D signaling in other cell types were observed along with genes known to affect insulin release, although with our assay we were not able to detect any effects of 1,25(OH)2D3 on glucose-stimulated insulin release from healthy pancreatic islets.

CONCLUSION

The effects of 1,25(OH)2D3 on the expression of cytoskeletal and intracellular trafficking genes along with genes involved in ion transport may influence insulin exocytosis. However, an effect of 1,25(OH)2D3 on insulin release could not be detected for healthy islets in contrast to islets subjected to pathological conditions such as cytokine exposure and vitamin D deficiency as suggested by other studies. Thus, in addition to previously identified tolerogenic effects on the immune system, 1,25(OH)2D3 may affect basic functions of pancreatic beta cells, with the potential to render them more resistant to the detrimental conditions encountered during type 1 and 2 diabetes. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Gadd45 in modulation of solid tumors and leukemia

The stress response gadd45 gene family participates in cell cycle control, cell survival, apoptosis, maintenance of genomic stability, DNA repair, and active DNA demethylation, in response to environmental and physiological stress including oncogenic stress. Given these diverse functions, it is anticipated that gadd45 genes can influence the initiation and progression of malignancy and the response to different treatments. This chapter will provide an overview of how the different members of the gadd45 gene family are expressed in different tumors and leukemia, how this may impact on progression of disease, and what happens when expression is manipulated. Studies from human tumor/leukemia samples, cell lines, and animal models are included in this review. An overriding theme is that each of the gadd45 genes has both tumor suppressor and tumor promoter functions, dependent on the tissue/cell type and transforming event.

Why has it taken so long for biological psychiatry to develop clinical tests and what to do about it?

Patients with mental disorders show many biological abnormalities which distinguish them from normal volunteers; however, few of these have led to tests with clinical utility. Several reasons contribute to this delay: lack of a biological 'gold standard' definition of psychiatric illnesses; a profusion of statistically significant, but minimally differentiating, biological findings; 'approximate replications' of these findings in a way that neither confirms nor refutes them; and a focus on comparing prototypical patients to healthy controls which generates differentiations with limited clinical applicability. Overcoming these hurdles will require a new approach. Rather than seek biomedical tests that can 'diagnose' DSM-defined disorders, the field should focus on identifying biologically homogenous subtypes that cut across phenotypic diagnosis--thereby sidestepping the issue of a gold standard. To ensure clinical relevance and applicability, the field needs to focus on clinically meaningful differences between relevant clinical populations, rather than hypothesis-rejection versus normal controls. Validating these new biomarker-defined subtypes will require longitudinal studies with standardized measures which can be shared and compared across studies--thereby overcoming the problem of significance chasing and approximate replications. Such biological tests, and the subtypes they define, will provide a natural basis for a 'stratified psychiatry' that will improve clinical outcomes across conventional diagnostic boundaries.

Gene transfection enhanced by ultrasound exposure combined with drug treatment guided by gene chip analysis

PURPOSE

Heterogeneous bioeffects have been reported in previous studies of ultrasound-mediated gene delivery. The goal of this study is to identify the differences between cells that take up plasmid DNA (pDNA) after sonication but are not transfected and cells that similarly take up pDNA but are transfected. We used these findings to select drugs that regulate intracellular processes expected to enhance gene transfection in combination with US.

MATERIALS AND METHODS

Gene expression among DU145 human prostate cancer cells after ultrasound-mediated transfection was analyzed using Affymetrix GeneChip Human Genome U133 Plus 2.0 Arrays. Drug treatments suggested by the microarray analysis were combined with US exposure to regulate the corresponding intracellular processes. Cell viability and transfection efficiency were determined by flow cytometry to analyze the effects of US combined with drug treatment.

RESULTS

Genes such as GADD45α (growth arrest and DNA-damage inducible, alpha) and Topoisomerase IIα were found to be associated with successful transfection. Drugs that regulate GADD45α and Topoisomerase IIα (e.g., ethyl methanesulfomate, amsacrine and chloroquine) were shown to increase ultrasound-mediated transfection efficiency by up to 2 fold.

CONCLUSIONS

Among cells with pDNA uptake after sonication, we found that genes are differentially expressed among transfected cells versus non-transfected cells. Regulation of the expression level of GADD45α and TOP2α and other intracellular processes can yield higher efficiency of ultrasound-mediated gene transfection. This suggests that a strategy to increase gene transfection efficiency involving the combination of sonication and regulation of intracellular processes using drugs could further enhance US-mediated gene transfection.

GADD45 proteins: central players in tumorigenesis

The Growth Arrest and DNA Damage-inducible 45 (GADD45) proteins have been implicated in regulation of many cellular functions including DNA repair, cell cycle control, senescence and genotoxic stress. However, the pro-apoptotic activities have also positioned GADD45 as an essential player in oncogenesis. Emerging functional evidence implies that GADD45 proteins serve as tumor suppressors in response to diverse stimuli, connecting multiple cell signaling modules. Defects in the GADD45 pathway can be related to the initiation and progression of malignancies. Moreover, induction of GADD45 expression is an essential step for mediating anti-cancer activity of multiple chemotherapeutic drugs and the absence of GADD45 might abrogate their effects in cancer cells. In this review, we present a comprehensive discussion of the functions of GADD45 proteins, linking their regulation to effectors of cell cycle arrest, DNA repair and apoptosis. The ramifications regarding their roles as essential and central players in tumor growth suppression are also examined. We also extensively review recent literature to clarify how different chemotherapeutic drugs induce GADD45 gene expression and how its up-regulation and interaction with different molecular partners may benefit cancer chemotherapy and facilitate novel drug discovery.

Gadd45α activity is the principal effector of Shigella mitochondria-dependent epithelial cell death in vitro and ex vivo

Modulation of death is a pathogen strategy to establish residence and promote survival in host cells and tissues. Shigella spp. are human pathogens that invade colonic mucosa, where they provoke lesions caused by their ability to manipulate the host cell responses. Shigella spp. induce various types of cell death in different cell populations. However, they are equally able to protect host cells from death. Here, we have investigated on the molecular mechanisms and cell effectors governing the balance between survival and death in epithelial cells infected with Shigella. To explore these aspects, we have exploited both, the HeLa cell invasion assay and a novel ex vivo human colon organ culture model of infection that mimics natural conditions of shigellosis. Our results definitely show that Shigella induces a rapid intrinsic apoptosis of infected cells, via mitochondrial depolarization and the ensuing caspase-9 activation. Moreover, for the first time we identify the eukaryotic stress-response factor growth arrest and DNA damage 45α as a key player in the induction of the apoptotic process elicited by Shigella in epithelial cells, revealing an unexplored role of this molecule in the course of infections sustained by invasive pathogens.

α-Catulin knockdown induces senescence in cancer cells

Cellular senescence functions as a tumor suppressor that protects against cancer progression. α-Catulin, an α-catenin-related protein, is reported to have tumorigenic potential because it regulates the nuclear factor-κB (NF-κB) pathway, but little is known about its clinical relevance and the mechanism through which it regulates cancer progression. Here, we found that α-catulin mRNA levels were significantly upregulated in cancer cell lines and clinical oral squamous cell carcinomas, which positively correlated with tumor size (P=0.001) and American Joint Committee on Cancer (AJCC) stage (P=0.004). α-Catulin knockdown in the OC2 and A549 cancer cell lines dramatically decreased cell proliferation and contributed to cellular senescence, and inhibited OC2 xenograft growth. Mechanistic dissection showed that α-catulin depletion strongly induced the DNA-damage response (DDR) in both cell lines, via a p53/p21-dependent pathway in A549 cells, but a p53/p21-independent pathway in OC2 cells carrying mutant p53. Global gene expression analysis revealed that α-catulin knockdown altered cell-cycle regulation and DDR pathways at the presenescent stage as well as significantly downregulate several crucial genes related to mitotic chromosome condensation, DDR and DNA repair systems, which suggests that its depletion-induced cellular senescence might be caused by chromosome condensation failures, severe DNA damage and impaired DNA repair ability. Our study provides evidence that α-catulin promotes tumor growth by preventing cellular senescence and suggests that downregulating α-catulin may be a promising therapeutic approach for cancer treatment.

Gadd45 stress sensors in malignancy and leukemia

Gadd45 proteins, including Gadd45a, Gadd45b, and Gadd45g, have been implicated in stress signaling in response to physiological and environmental stress, including oncogenic stress, which can result in cell cycle arrest, DNA repair, cell survival, senescence, and apoptosis. The function of Gadd45 as a stress sensor is mediated via a complex interplay of physical interactions with other cellular proteins implicated in cell cycle regulation and the response of cells to stress, notably PCNA, p21, cdc2/cyclinB1, and the p38 and JNK stress response kinases. Altered expression of Gadd45 has been observed in multiple types of solid tumors as well as in hematopoietic malignancies. Using genetically engineered mouse models and bone-marrow transplantation, evidence has been obtained indicating that Gadd45 proteins can function to either promote or suppress tumor development and leukemia; this is dependent on the molecular nature of the activated oncogene and the cell type, via engagement of different signaling pathways.

Pancreatic cancer: gene therapy approaches and gene delivery systems

IMPORTANCE OF THE FIELD

Due to the absence of early diagnosis, the highly invasive and metastatic features and the lack of effective therapeutic modalities, the prognosis of patients with pancreatic cancer is poor. Gene therapy is currently regarded as a potential and promising therapeutic modality for pancreatic cancer.

AREAS COVERED IN THIS REVIEW

This article summarizes an update of gene therapy approaches and reviews the latest progress in gene delivery systems that have been tested on pancreatic cancer.

WHAT THE READER WILL GAIN

The treatment effectiveness of gene combination therapy is better than that of the regulation of single-gene or single gene therapy approaches. Naked DNA is limited because of degradation by intracellular and extracellular nucleases. Virus vectors show high transfection efficiency but are limited due to immunogenicity, inflammatory response and potential carcinogenicity. Non-viral vectors, such as cationic polymers or inorganic nanoparticles, show an important feature that they can be easily modified, and the progress of materials science will provide more and better non-viral vectors, accordingly improving the efficiency and safety of gene therapy, which will make them the most promising vectors for pancreatic cancer.

Cell cycle control pathways act as conditioning factors for TK/GCV sensitivity in pancreatic cancer cells

The suicide system TK/GCV is an enzyme/prodrug therapy that involves the transfer of the cDNA for the herpes simplex virus thymidine kinase gene (TK) into tumor cells which then sensitizes the cells to the non-toxic antiviral drug ganciclovir. Although extensively characterized, the suicide system TK/GCV conceals the details of its mechanism of action. In order to shed some light on this issue, we conducted experiments designed to identify key features of sensitive cells, as compared to cells that displayed reduced sensitivity to TK/GCV. Cell lines displaying different degrees of sensitivity underwent apoptotic cell death upon treatment with TK/GCV. S-phase delay, however, was almost exclusively restricted to sensitive cells and was impaired in a model of treatment-induced resistance. In this model genes with differential expression associated to induced resistance were identified. Noteworthy, two cell cycle-related genes (CCNE1 and GADD45) were functionally validated as conditioners of cellular sensitivity to TK/GCV. The relevance of cell cycle control was further demonstrated by experiments showing the association of Chk1 activation with greater TK/GCV cytotoxicity. Combination treatment with Chk1 inhibitor UCN-01 induced, in sensitive cells, an antagonistic effect on TK/GCV cytotoxicity highlighting the relevance of Chk1's activity on TK/GCV mechanism of action. These results reveal the relevance of cell cycle control pathways in the cytotoxicity induced by the TK/GCV system identifying candidate genes as conditioners of TK/GCV sensitivity. Moreover it points out, for the first time at Chk1 activation as a key factor to mediate TK/GCV cytotoxicity.

Oligonucleotide microarray analysis of apoptosis induced by 15-methoxypinusolidic acid in microglial BV2 cells

BACKGROUND AND PURPOSE

We conducted a genome wide gene expression analysis to explore the biological aspects of 15-methoxypinusolidic acid (15-MPA) isolated from Biota orientalis and tried to confirm the suitability of 15-MPA as a therapeutic candidate for CNS injuries focusing on microglia.

EXPERIMENTAL APPROACH

Murine microglial BV2 cells were treated with 15-MPA, and their transcriptome was analysed by using oligonucleotide microarrays. Genes differentially expressed upon 15-MPA treatment were selected for RT-PCR (reverse transcription-polymerase chain reaction) analysis to confirm the gene expression. Inhibition of cell proliferation and induction of apoptosis by 15-MPA were examined by bromodeoxyuridine assay, Western blot analysis of poly-ADP-ribose polymerase and flow cytometry.

KEY RESULTS

A total of 514 genes were differentially expressed by 15-MPA treatment. Biological pathway analysis revealed that 15-MPA induced significant changes in expression of genes in the cell cycle pathway. Genes involved in growth arrest and DNA damage [gadd45alpha, gadd45gamma and ddit3 (DNA damage-inducible transcript 3)] and cyclin-dependent kinase inhibitor (cdkn2b) were up-regulated, whereas genes involved in cell cycle progression (ccnd1, ccnd3 and ccne1), DNA replication (mcm4, orc1l and cdc6) and cell proliferation (fos and jun) were down-regulated. RT-PCR analysis for representative genes confirmed the expression levels. 15-MPA significantly reduced bromodeoxyuridine incorporation, increased poly-ADP-ribose polymerase cleavage and the number of apoptotic cells, indicating that 15-MPA induces apoptosis in BV2 cells.

CONCLUSION AND IMPLICATIONS

15-MPA induced apoptosis in murine microglial cells, presumably via inhibition of the cell cycle progression. As microglial activation is detrimental in CNS injuries, these data suggest a strong therapeutic potential of 15-MPA.