Upregulation of GADD153 expression in the apoptotic signaling of N-(4-hydroxyphenyl)retinamide (4HPR)

Differences in Zbtb7a expression cause heterogeneous changes in human nasopharyngeal carcinoma CNE3 sublines

The present study aimed to determine the association between changes in Zbtb7a expression levels and heterogeneity of nasopharyngeal carcinoma (NPC) CNE3 sublines. CNE3 sublines were established by screening of serial dilution and continuous passage. Proliferative ability and tumorigenicity of the sublines were analyzed separately by soft-agar colony formation and mouse studies. The NPC tissues from mice were analyzed by histological evaluation and immunohistochemistry. The expression levels of Zbtb7a mRNA and protein were analyzed separately by quantitative reverse transcription polymerase chain reaction and western blotting. According to findings from the soft-agar colony formation and mouse studies, two sublines with increased tumorigenicity compared with other sublines were transfected transiently with Zbtb7a short hairpin RNA (shRNA) recombinant plasmid. The changes in viability, migration and invasion abilities were evaluated separately by MTT, colorimetric focus-formation, Transwell migration and invasion assays. The sublines CNE3-GX6 and CNE3-GX11 were selected for subsequent study due to increased tumorigenicity and increased Zbtb7a expression levels compared with the other sublines. High metastatic potency was not observed in all of the sublines. Zbtb7a expression levels were positively associated with tumorigenic degree of the sublines. The growth, migration and invasion abilities of the sublines transfected with Zbtb7a shRNA plasmid were decreased compared with the cells transfected with empty vector in the negative control group. The findings suggest Zbtb7a expression levels may be associated with heterogeneity of CNE3 sublines. Therefore, Zbtb7a may have an important role in the regulatory mechanism of NPC heterogeneity.

Molecular markers to assess short-term disease local recurrence in nasopharyngeal carcinoma

An important challenge in nasopharyngeal carcinoma (NPC) research is to develop effective predictors of tumor recurrence following treatment to determine whether immediate adjuvant therapy is necessary. We retrospectively analyzed archived specimens collected from 45 patients with paired samples of primary NPC (pNPC) and recurrent NPC (rNPC). Clinical samples were collected from the Cancer Center Databases of the First People’s Hospital of Foshan and Shantou Central Hospital (affiliates of Sun Yat-Sen University) between 2001 and 2012. Expression levels of phosphor-Stat3 (p-Stat3), signalosome complex subunit 5 (Jab1/Csn5), Akt1, C/EBP homologous protein (CHOP), Ki-67, and apoptosis were determined by immunohistochemistry in pNPC and rNPC samples from the same patients. Differences in these markers between the short-term interval to recurrence (ITR) group (ITR <18 months) and long-term ITR group (ITR ≥18 months) were further analyzed. In Cox’s regression analysis, the ITR was significantly associated as an independent-negative prognostic factor for overall survival (hazard ratio, 0.211; 95% confidence interval, 0.053–0.841; P=0.027). p-Stat3 was increased in the short-term ITR group (ITR <18 months) and tended to be lower in the long-term ITR group (ITR ≥18 months). In the short-term ITR group, nuclear Akt expression was significantly increased in paired rNPC (P=0.028). In the long-term ITR group, the expression of nuclear Jab1/Csn5 (P=0.047) and assessment of apoptosis measured with TdT-mediated dUTP nick end-labeling (TUNEL) (P=0.003) was significantly increased in paired rNPC. The results suggest that differences between short- and long-term ITR may predict outcome in rNPC. Furthermore, the overexpression of Jab1/Csn5 and Akt may contribute to the carcinogenesis of rNPC, and Akt seems to promote the progression of short-term ITR. Intra-individual changes of Jab1/Csn5, Akt, and TUNEL may help to identify short-term ITR.

Molecular pathological study of the human nasopharyngeal carcinoma CNE3 cell line

The present study aimed to identify the molecular pathological changes of the nasopharyngeal carcinoma (NPC) epithelial CNE3 cell line, which has been used in experimental studies for 20 years in a culture environment. The pathological type of NPC and the presence of the Epstein-Barr virus (EBV) were identified. CNE3 short tandem repeats (STRs) were amplified, analyzed and compared using metastatic carcinoma tissue from primary NPC. Immunohistochemistry (IHC) and in situ hybridization (ISH) were used to identify the immunophenotype and EBV-encoded small RNA (EBER) expression in nude mice transplanted CNE3 tumor cells. Polymerase chain reaction (PCR) and DNA sequencing were used to identify the EBV oncogene, BamH1-A right frame 1 (BARF1) and electron microscopy was used to analyze the organization of the ultrastructure. CNE3 was not cross-contaminated by other human cell lines and the EBV was no longer present in the CNE3 cells. The pathological type of CNE3 was transformed from an undifferentiated non-keratinizing carcinoma with focal adenocarcinoma differentiation into a poorly-differentiated adenocarcinoma. In conclusion, this knowledge on the molecular pathological changes of CNE3 may aid in the development of new research approaches for NPC.

Clinical significance of GADD153 expression in stage I non-small cell lung cancer

The transcription factor growth arrest and DNA damage-inducible gene 153 (GADD153), also known as CHOP, is considered to function as a proapoptotic molecule. Overexpression of GADD153 leads to cell cycle arrest and/or apoptosis. However, its clinical implications in non-small cell lung cancer (NSCLC) remain controversial. Therefore, we investigated the expression of GADD153 in stage I NSCLC using immunohistochemistry. Paraffin-embedded tissue sections from 76 patients, who were diagnosed with primary stage I NSCLC and had undergone a curative lung resection, were stained using an anti-GADD153 antibody. The intensity of GADD153 immunostaining was evaluated within the cell membrane and cytoplasm of invasive cancer components. The correlation between the intratumoral expression of GADD153 and various clinical parameters were explored. GADD153 was detected in 29 (38.2%) cases. No statistically significant difference in expression was demonstrated between stage IA and stage IB tumors (35.0 vs. 39.3%; P=0.735). The expression of GADD153 was not affected by histological subtypes or histological grades of differentiation. The intratumoral expression of GADD153 did not influence the overall survival rate (53.29 vs. 52.18 months; P=0.743) or disease-free survival rate (46.97 vs. 54.19 months; P=0.084) of stage I NSCLC patients. However, patients with GADD153 expression demonstrated an improved disease-specific survival rate (28.80 vs. 53.85 months; P=0.020). No patients with GADD153 expression demonstrated distant metastasis (P=0.029). These data suggest that GADD153 expression may be a valuable prognostic factor of early-stage NSCLC in patients who have undergone curative lung resection.

Progression of apoptic signaling from mesenteric ischemia-reperfusion injury to lungs: correlation in the level of ER chaperones expression

Multiple organ dysfunction syndrome (MODS) is characterized by the development of probably reversible, progressive dysfunction of vital systems in two or more organs, directly undamaged by surgery or other trauma. The organs which have the most common potential dysfunction are lungs, liver, kidneys, heart and gastrointestinal tract. The small intestine is the source of production of proinflammatory mediators leading and contributing to multiorgan failure. The endoplasmic reticulum (ER), after ischemia and post-ischemic reperfusion, is significantly involved in the activation of enterocyte apoptosis. The purpose of this study was to determine the stage of apoptosis in the lungs, initiated through inflammatory response from the small intestine. We analyzed changes in mRNA levels of pro-apoptotic genes Gadd153 (Chop) and anti-apoptotic genes Grp78 (Bip) in the small intestine wall and lung parenchyma. During experimental procedure the rats underwent 60 min of ischemia, caused by complete occlusion of the mesenteric arteria cranialis, with subsequent reperfusion and evaluation after 1 h, 24 h and 30 days (from R1, R24 to R30, respectively, each group n = 8). The gene expression levels were measured using RT-PCR followed by electrophoresis and visualization under UV. In the lungs we detected significantly lower level of expression Grp78 by 45 ± 6.9%. This suggests that ischemic attack and subsequent reperfusion did not promote ER stress in the lungs through induction of Gadd153 expression in the small intestine. There is still no effective approach to the treatment of affected ischemic intestine tissue, to stop the processes with could eventually lead to MODS. Therefore it is necessary to study changes in the damaged tissue at the molecular level and try to suggest possible therapeutic defined routes to the protection of tissue.

Tryptophan deprivation induces inhibitory receptors ILT3 and ILT4 on dendritic cells favoring the induction of human CD4+CD25+ Foxp3+ T regulatory cells

Tryptophan catabolism through IDO activity can cause nonresponsiveness and tolerance acting on T cells. Given the crucial importance of dendritic cells (DCs) in the initiation of a T cell response, surprisingly little is known about the impact of IDO activity and tryptophan deprivation on DCs themselves. In the present study, we show that human DCs differentiated under low-tryptophan conditions acquire strong tolerogenic capacity. This effect is associated with a markedly decreased Ag uptake as well as the down-regulation of costimulatory molecules (CD40, CD80). In contrast, the inhibitory receptors ILT3 and ILT4 are significantly increased. Functionally, tryptophan-deprived DCs show a reduced capacity to stimulate T cells, which can be restored by blockade of ILT3. Moreover, ILT3(high)ILT4(high) DCs lead to the induction of CD4(+)CD25(+) Foxp3(+) T regulatory cells with suppressive activity from CD4(+)CD25(-) T cells. The generation of ILT3(high)ILT4(high) DCs with tolerogenic properties by tryptophan deprivation is linked to a stress response pathway mediated by the GCN2 kinase. These results demonstrate that tryptophan degradation establishes a regulatory microenvironment for DCs, enabling these cells to induce T regulatory cells. The impact of IDO thus extends beyond local immune suppression to a systemic control of the immune response.

Upregulation of GADD153 by butyrate: involvement of MAPK

Butyrate inhibits the proliferation of cancer cells, but the early molecular events initiated by butyrate have not been fully identified. Herein, butyrate is shown to affect the growth arrest and DNA damage-inducible gene 153 (GADD153) in HCT-116 human colon adenocarcinoma cells. Despite absence of any detectable cellular DNA damage, the expression of GADD153 was upregulated before several features characteristic of apoptosis appeared. Butyrate-induced upregulation of GADD153 mRNA was attenuated by actinomycin D, but apparently not by cycloheximide. In investigating possible involvement of MAPK in mediating the effect of butyrate on GADD153 mRNA expression, the extracellular regulated kinase (ERK) inhibitor PD98059, but neither the JNK inhibitor SP600125 nor the p38 MAPK inhibitor SB203580, blunted the ability of butyrate to upregulate GADD153 mRNA expression. U0126, a selective inhibitor of upstream MEK, had a similar effect as PD98059 on butyrate-induced GADD153 mRNA upregulation. Collectively, these findings suggest that butyrate caused activation of the GADD153 gene at the level of transcription involving mainly the MEK/ERK branch of the MAPK signal transduction pathway. Moreover, these molecular events were not the result of any DNA damage and occurred before several features characteristic of apoptosis became evident.

CAAT/enhancer binding protein homologous protein-dependent death receptor 5 induction is a major component of SHetA2-induced apoptosis in lung cancer cells

The flexible heteroarotinoids (Flex-Het) represent a novel type of atypical retinoids lacking activity in binding to and transactivating retinoid receptors. Preclinical studies have shown that Flex-Hets induce apoptosis of cancer cells while sparing normal cells and exhibit anticancer activity in vivo with improved therapeutic ratios over conventional retinoid receptor agonists. Flex-Hets have been shown to induce apoptosis through activation of the intrinsic apoptotic pathway. The present study has revealed a novel mechanism underlying Flex-Het-induced apoptosis involving induction of death receptor 5 (DR5). The representative Flex-Het SHetA2 effectively inhibited the growth of human lung cancer cells in cell culture and in mice. SHetA2 induced apoptosis, which could be abrogated by silencing caspase-8 expression, indicating that ShetA2 triggers a caspase-8-dependent apoptosis. Accordingly, SHetA2 up-regulated DR5 expression, including cell surface levels of DR5, and augmented tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Importantly, small interfering RNA (siRNA)-mediated blockade of DR5 induction conferred cell resistance to SHetA2-induced apoptosis, as well as SHetA2/TRAIL-induced apoptosis. These results show that DR5 induction is a key component of apoptosis induced by SHetA2 or by SHetA2 combined with TRAIL. SHetA2 exerted CAAT/enhancer-binding protein homologous protein (CHOP)-dependent transactivation of the DR5 promoter. Consistently, SHetA2 induced CHOP expression, which paralleled DR5 up-regulation, whereas siRNA-mediated blockage of CHOP induction prevented DR5 up-regulation, indicating CHOP-dependent DR5 up-regulation by SHetA2. Collectively, we conclude that CHOP-dependent DR5 up-regulation is a key event mediating SHetA2-induced apoptosis.

6-Shogaol induces apoptosis in human colorectal carcinoma cells via ROS production, caspase activation, and GADD 153 expression

Ginger, the rhizome of Zingiber officinale, is a traditional medicine with anti-inflammatory and anticarcinogenic properties. This study examined the growth inhibitory effects of the structurally related compounds 6-gingerol and 6-shogaol on human cancer cells. 6-Shogaol [1-(4-hydroxy-3-methoxyphenyl)-4-decen-3-one] inhibits the growth of human cancer cells and induces apoptosis in COLO 205 cells through modulation of mitochondrial functions regulated by reactive oxygen species (ROS). ROS generation occurs in the early stages of 6-shogaol-induced apoptosis, preceding cytochrome c release, caspase activation, and DNA fragmentation. Up-regulation of Bax, Fas, and FasL, as well as down-regulation of Bcl-2 and Bcl-X(L )were observed in 6-shogaol-treated COLO 205 cells. N-acetylcysteine (NAC), but not by other antioxidants, suppress 6-shogaol-induced apoptosis. The growth arrest and DNA damage (GADD)-inducible transcription factor 153 (GADD153) mRNA and protein is markedly induced in a time- and concentration-dependent manner in response to 6-shogaol.

N-(4-hydroxyphenyl)retinamide induces apoptosis in human retinal pigment epithelial cells: retinoic acid receptors regulate apoptosis, reactive oxygen species generation, and the expression of heme oxygenase-1 and Gadd153

N-(4-hydroxyphenyl)retinamide (4HPR, fenretinide), a retinoic acid (RA) derivative and a potential cancer preventive agent, is known to exert its chemotherapeutic effects in cancer cells through induction of apoptosis. Earlier work from our laboratory has shown that relatively low concentrations of 4HPR induce neuronal differentiation of cultured human retinal pigment epithelial (ARPE-19) cells (Chen et al., 2003, J Neurochem 84:972-981). However, at higher concentrations of 4HPR, these cells showed morphological changes including cell shrinkage and cell death. Here we demonstrate that ARPE-19 cells treated with 4HPR exhibit a dose- and time-dependent induction of apoptosis as evidenced by morphological changes, mono- and oligonucleosome generation, and increased activity of caspases 2 and 3. The 4HPR-induced apoptosis as well as the activation of caspases 2 and 3 were blocked by both retinoic acid receptors (RAR) pan-antagonists, AGN193109 and AGN194310, and by an RARalpha-specific antagonist AGN194301. 4HPR treatment also increased reactive oxygen species (ROS) generation in ARPE-19 cells in a time-dependent manner as determined from the oxidation of 2',7'-dichlorofluorescin. In addition, the increase in the expression of heme oxygenase-1 (HO-1), a stress response protein, and the growth arrest and DNA damage-inducible transcription factor 153 (Gadd153) in response to the ROS generation were also blocked by these receptor antagonists. Pyrrolidine dithiocarbamate (PDTC), a free-radical scavenger, inhibited 4HPR-induced ROS generation, the expression of its downstream mediator, Gadd153, and apoptosis in the pretreated cells. Therefore, our results, clearly demonstrate that 4HPR induces apoptosis in ARPE-19 cells and that RARs mediate this process by regulating ROS generation as well as the expression of Gadd153 and HO-1.

Mechanisms of fenretinide-induced apoptosis

Fenretinide, a synthetic retinoid, has emerged as a promising anticancer agent based on numerous in vitro and animal studies, as well as chemoprevention clinical trials. In vitro observations suggest that the anticancer activity of fenretinide may arise from its ability to induce apoptosis in tumor cells. Diverse signaling molecules including reactive oxygen species, ceramide, and ganglioside GD3 can mediate apoptosis induction by fenretinide in transformed, premalignant, and malignant cells. In many cell types, these signaling intermediates appear to be induced by mechanisms that are independent of retinoic acid receptor activation, and ultimately initiate the intrinsic or mitochondrial-mediated pathway of cell elimination. Numerous investigations conducted during the past 10 years have discovered a great deal about the apoptogenic activity of fenretinide. In this review we explore the mechanisms associated with fenretinide-induced apoptosis and highlight certain mechanistic underpinnings of fenretinide-induced cell death that remain poorly understood and thus warrant further characterization.

Green tea polyphenol stimulates cancer preventive effects of celecoxib in human lung cancer cells by upregulation ofGADD153 gene

To more clearly understand the molecular mechanisms involved in synergistic enhancement of cancer preventive activity with the green tea polyphenol (-)-epigallocatechin gallate (EGCG), we examined the effects of cotreatment with EGCG plus celecoxib, a cyclooxygenase-2 selective inhibitor. We specifically looked for induction of apoptosis and expression of apoptosis related genes, with emphasis on growth arrest and DNA damage-inducible 153 (GADD153) gene, in human lung cancer cell line PC-9: Cotreatment with EGCG plus celecoxib strongly induced the expression of both GADD153 mRNA level and protein in PC-9 cells, while neither EGCG nor celecoxib alone did. However, cotreatment did not induce expression of other apoptosis related genes, p21(WAF1) and GADD45. Judging by upregulation of GADD153, only cotreatment with EGCG plus celecoxib synergistically induced apoptosis of PC-9 cells. Synergistic effects with the combination were also observed in 2 other lung cancer cell lines, A549 and ChaGo K-1. Furthermore, EGCG did not enhance GADD153 gene expression or apoptosis induction in PC-9 cells in combination with N-(4-hydroxyphenyl)retinamide or with aspirin. Thus, upregulation of GADD153 is closely correlated with synergistic enhancement of apoptosis with EGCG. Cotreatment also activated the mitogen-activated protein kinases (MAPKs), such as ERK1/2 and p38 MAPK: Preteatment with PD98059 (ERK1/2 inhibitor) and UO126 (selective MEK inhibitor) abrogated both upregulation of GADD153 and synergistic induction of apoptosis of PC-9 cells, while SB203580 (p38 MAPK inhibitor) did not do so, indicating that GADD153 expression was mediated through the ERK signaling pathway. These findings indicate that high upregulation of GADD153 is a key requirement for cancer prevention in combination with EGCG.

ROS mediates 4HPR-induced posttranscriptional expression of the Gadd153 gene

All-trans-N-(4-hydroxyphenyl)retinamide (4HPR) is a synthetic retinoid that can induce apoptosis in many cancer cell lines. The cytotoxicity of 4HPR is dependent on the production of ROS but the underlying reasons are not entirely certain. We have investigated the role of 4HPR-induced production of ROS in mediating the expression of the recently identified 4HPR-responsive gene Gadd153. In 4HPR-treated cells, the elevation of Gadd153 protein level was prevented by vitamin C, which had no effect on the activation of the Gadd153 gene promoter. The 4HPR-induced elevation of Gadd153 mRNA level persisted even after transcription was blocked with actinomycin D, but declined rapidly upon the addition of antioxidants to the transcription-arrested cells. The mRNA expressed from the full-length Gadd153 cDNA was degraded constitutively in cells in the absence but not in the presence of 4HPR. Such an inhibitory effect of 4HPR was abolished by antioxidants and by inhibitors of 12-lipoxygenase, baicalein (specific) and esculetin (panspecific). The inhibition of 4HPR-induced expression of Gadd153 protein by vitamin C was independent of intracellular proteasome activity and vitamin C had no effect on the intracellular decay of Gadd153 protein. Our data provide the first evidence that the posttranscriptional expression of the Gadd153 gene can be regulated by ROS produced by 4HPR.

Fenretinide: a prototype cancer prevention drug

Fenretinide (N-4-hydroxyphenylretinamide [4-HPR]) is a synthetic retinoid that has been examined in in vitro assays, preclinical animal models and clinical trials as a cancer chemopreventive agent. Its pharmacology, toxicity and mechanisms of action initially suggested an increased therapeutic index relative to native retinoids for the control of tumours of the breast, prostate, bladder, colon, cervix and head and neck. Although fenretinide at the doses and schedules used in several pivotal Phase II and III clinical trials has not been proven to be efficacious in reducing the incidence of cancer or in retarding the development of preneoplastic lesions, encouraging observations regarding unanticipated preventative activity, such as for ovarian cancer control, have arisen from these studies. Research in cancer therapy and the elucidation of molecular pathways activated by fenretinide have also yielded clues about how this agent might be better used in a prevention setting. Current trials are underway to re-examine both dose and schedule of fenretinide administration as well as the target tissues of interest. Investigations of potential synergism between fenretinide and other candidate chemopreventative molecules with complementary mechanisms of action may support future assessments of this prototype cancer prevention drug or its newer analogues.

Induction of reactive oxygen species renders mutant and wild-type K-ras pancreatic carcinoma cells susceptible to Ad.mda-7-induced apoptosis

Pancreatic cancer is exceptionally aggressive with no long-term effective therapy. Current interventional approaches, including surgery, radiation and/or chemotherapy, have done little to quell the mortality associated with this malignancy. Subtraction hybridization identified a cancer-specific apoptosis-inducing cytokine gene, melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24), with a broad range of selective antitumor activity in diverse cancers both in vitro and in vivo in nude mice and recently in patients with advanced carcinomas and melanomas. Unlike most neoplasms, pancreatic cancers display innate resistance to mda-7/IL-24-induced apoptosis, which correlates with a diminished capacity to convert mda-7/IL-24 mRNA into protein. We presently demonstrate that this translational block can be reversed by treatment with agents that elevate reactive oxygen species (ROS). Induction of apoptosis in vitro and suppression of tumorigenesis in vivo in nude mice are induced in pancreatic cancers, irrespective of the status of their K-ras gene, only when tumor cells simultaneously express mda-7/IL-24 and are treated with a ROS-inducer, such as arsenic trioxide (ARS), N-(4-hydroxyphenyl) retinamide (HPR) or dithiophene (NSC656240 (NSC)). In pancreatic cancer cells constitutively expressing mda-7/IL-24 mRNA, a single treatment with arsenic trioxide, HPR or NSC656240 induces apoptosis, which correlates with production of MDA-7/IL-24 protein. The specificity of this action is documented by the ability of ROS inhibitors, including N-acetyl-L-cysteine and Tiron, to block this killing effect. Of potential clinical significance, similar treatment of normal cells does not elicit significant changes in growth nor does it induce apoptosis. Analysis of signal transduction changes in pancreatic carcinoma cells infected with Ad.mda-7 in combination with a ROS-inducer indicate that cell death correlates with modulation of discrete cassettes of multiple signaling pathways in a pancreatic cancer cell-specific manner, supporting global signaling dysregulation as a potential mediator of apoptosis induction. These findings suggest a promising combinatorial approach for safely promoting cell death in pancreatic tumors that provides a rational framework for developing a selective and effective therapy for this invariably fatal cancer.

Increased GADD gene expression in human colon epithelial cells exposed to deoxycholate

The colonic epithelium is often exposed to high concentrations of secondary bile acids, which stresses the epithelial cells, leading potentially to activation of stress-response genes. To examine this possibility in vitro, the purpose of this study was to determine if expression of certain growth arrest and DNA damage-inducible genes (GADD) is upregulated in human colonic epithelial cells exposed to deoxycholate (DOC). DNA macroarray screening of a small cluster of stress/apoptosis-related genes in DOC-treated HCT-116 colonocytes revealed clearly higher expression of only GADD45, which was confirmed by gene-specific relative RT-PCR analysis. Subsequently, it was found that DOC also increased GADD34 mRNA expression. However, mRNA expression of GADD153 was increased most markedly in DOC-treated HCT-116 colonocytes, which express wild-type p53. However, the upregulation of GADD34, GADD45, and GADD153 mRNA expression apparently did not require p53, based on the finding that DOC increased expression of all three GADD genes in HCT-15 colonocytes, which express mutant p53. In further studying GADD153 in particular, the effect of DOC on GADD153 mRNA was prevented by actinomycin-D (Act-D), but not by antioxidants or MAPK inhibitors. DOC also caused GADD153 protein to be expressed in close parallel with increased GADD153 mRNA expression. Induction of GADD153 protein by DOC was prevented by either anisomycin or cycloheximide. These findings suggest that DOC-induced upregulation of GADD153 mRNA expression occurred at the level of transcription without involving reactive oxygen species and MAPK signaling, and that the expression of GADD153 protein was due also to translation of pre-existing, and not just newly synthesized, mRNA.

Increased GADD153 gene expression during iron chelation-induced apoptosis in Jurkat T-lymphocytes

Depriving cells of iron likely stresses them and can result in cell death. To examine the potential relationship between this form of stress and cell death, Jurkat T-lymphocytes were made iron-deficient by exposing them to the iron chelator, deferoxamine (DFO). Such treatment produced evidence of apoptosis, including cell shrinkage, membrane blebbing, chromatin condensation and fragmentation, and also formation of apoptotic bodies. Additionally, proteolytic cleavage of poly(ADP-ribose)polymerase was detected, suggesting involvement of caspases in initiating apoptosis. Indeed, a selective caspase-3 inhibitor prevented the effects of DFO. During the early induction period of apoptosis, GRP78 and HSP70 mRNA expression was not affected. In contrast, there was mainly increased mRNA expression of Growth Arrest and DNA Damage-inducible gene 153 (GADD153), which seemed to be at the level of transcription rather than mRNA stability. Furthermore, fortifying cells with antioxidants did not prevent the increased GADD153 mRNA expression, and no evidence of single-strand breaks in DNA was found, suggesting that neither reactive oxygen species nor DNA damage was involved in triggering GADD153 gene activation. DFO also caused GADD153 protein to be expressed. Because GADD153 is recognized as a pro-apoptotic gene, these findings generate the notion that GADD153 might help mediate apoptosis in iron-deficient cells.

Induction of GADD gene expression by phenethylisothiocyanate in human colon adenocarcinoma cells

Phenethylisothiocyanate (PEITC), a potential cancer chemopreventive agent, induces colon cancer cell death, but the mechanism is not entirely clear. Therefore, the aim of this study was to further clarify the molecular effects of PEITC in causing death of human colon adenocarcinoma cells. When incubated with PEITC, HCT-116 colonocytes showed morphological features characteristic of apoptosis, such as irregular cell shape, translocation of plasma membrane phosphatidylserine, and also chromatin condensation and fragmentation. These changes occurred after single-strand breaks in DNA were detected, suggesting that PEITC induced irreparable DNA damage, which in turn triggered the process of apoptosis. DNA macroarray analysis of a selected small cluster of apoptosis-related genes revealed noticeably higher expression of only GADD45, which was confirmed by gene-specific relative RT-PCR analysis. This led to investigation of other GADD gene members possibly affected by PEITC. Whereas GADD34 mRNA expression increased just slightly, there was an appreciable elevation of the mRNA for GADD153, which is recognized as a pro-apoptotic gene. The effect of PEITC on GADD153 was attenuated by either actinomycin D or N-acetylcysteine, suggesting that PEITC-induced upregulation of GADD153 mRNA expression was partly at the level of transcriptional activation involving reactive oxygen species. Additionally, PEITC-induced upregulation of GADD153 mRNA expression did not appear to require p53, based on the observation that PEITC also increased GADD153 mRNA expression in HCT-15 colonocytes, which are known to express mutant p53. These findings suggest that PEITC creates an oxidative cellular environment that induces DNA damage and GADD153 gene activation, which in turn helps trigger apoptosis.