Activation of caspase-8 during N-(4-hydroxyphenyl)retinamide-induced apoptosis in Fas-defective hepatoma cells

Anti-proliferative Effect of 15,16-Dihydrotanshinone I Through Cell Cycle Arrest and the Regulation of AMP-activated Protein Kinase/Akt/mTOR and Mitogen-activated Protein Kinase Signaling Pathway in Human Hepatocellular Carcinoma Cells

Background

15,16-dihydrotanshinone I (DHTS) is a natural abietane diterpenoid that is mainly found in the roots of Salvia miltiorrhiza Bunge (Labiatae). DHTS exhibits a potential anti-proliferative effect in various human cancer cells. However, the mechanisms of action of DHTS as an anti-cancer agent have not been fully elucidated. Therefore, the present study investigated the anti-cancer effect of DHTS in terms of cell cycle regulation and the regulation of the AMP-activated protein kinase (AMPK)/Akt/mTOR signaling pathway in SK-HEP-1 human hepatocellular carcinoma cells.

Methods

The anti-proliferative effects of DHTS were evaluated by the sulforhodamine B assay in SK-HEP-1 cells. Cell cycle distribution was analyzed by flow cytometry. The elucidation of mechanisms of action such as the AMPK/AKT/mTOR and mitogen-activated protein kinase (MAPK) pathway was assessed by Western blot analysis.

Results

DHTS showed a significant anti-proliferative activity against SK-HEP-1 cells. DHTS induced cell cycle arrest in the G0/G1 phase, which was mediated by downregulation of cyclin D1, cyclin A, cyclin E, CDK4, CDK2, c-Myc and p-Rb expression and with increased expression of the CDK inhibitor p21. DHTS also activated the AMPK signaling. In addition, DHTS downregulated the Akt/mTOR and MAPK signaling pathways.

Conclusions

Our results suggest that the anti-proliferative activity of DHTS might be associated with the induction of G0/G1 phase cell cycle arrest and regulation of AMPK/Akt/mTOR and MAPK signaling pathways in SK-HEP-1 cells.

Blazeispirol A from Agaricus blazei fermentation product induces cell death in human hepatoma Hep 3B cells through caspase-dependent and caspase-independent pathways

Currently, liver cancer is a leading cause of cancer-related death in the world. Hepatocellular carcinoma is the most common type of liver cancer. Previously, it was reported that blazeispirol A (BA) is the most active antihepatoma compound in an ethanolic extract of Agaricus blazei fermentation product. The aim of this study was to understand the antihepatoma mechanism of BA in human liver cancer Hep 3B cells. The results showed that BA inhibited the growth of Hep 3B cells and increased the percentage of cells in sub-G1 phase in a concentration- and time-dependent manner. In addition, BA treatment resulted in DNA fragmentation, caspase-9 and caspase-3 activations, poly(ADP-ribose)polymerase (PARP) degradation, down-regulation of Bcl-2 and Bcl-xL expressions, up-regulation of Bax expression, and disruption of the mitochondrial membrane potential (MMP) in Hep 3B cells. Furthermore, z-VAD-fmk, a caspase inhibitor, did not enhance the viability of BA-treated Hep 3B cells, and BA induced the release of HtrA2/Omi and apoptosis-inducing factor (AIF) from mitochondria into the cytosol. These findings suggested that BA with novel chemopreventive and chemotherapeutic potentials causes both caspase-dependent and caspase-independent cell death in Hep 3B cells.

Hypoxia and retinoic acid-inducible NDRG1 expression is responsible for doxorubicin and retinoic acid resistance in hepatocellular carcinoma cells

Hypoxia may activate survival signals in cancer cells. Moreover, hypoxic cells are less sensitive than normoxic cells to doxorubicin cytotoxicity, a potent activator of the p53 tumor suppressor gene. N-myc downstream-regulated gene-1 (NDRG1) is a hypoxia- and retinoic acid-inducible protein, and has been previously implicated in carcinogenesis. As this protein is also a downstream target of p53 and hepatocellular carcinoma (HCC) cells frequently evidence resistance to retinoic acid (RA) cytotoxicity, we attempted to determine whether the suppression of NDRG1 expression may sensitize HCC cells to doxorubicin and/or RA cytotoxicity. HCC cells expressed NDRG1 protein, and the expression of this protein was hypoxia- and RA-inducible. Doxorubicin treatment induced HCC cell cytotoxicity via the activation of mitochondrial apoptotic signals, including caspase-9 activation. Hypoxic HCC cells are less sensitive to doxorubicin-induced apoptosis. The suppression of NDRG1 expression either by siRNA or flavopiridol sensitized hypoxic HCC cells to doxorubicin cytotoxicity, and this was attributed to more profound augmentation of JNK and caspase-9 activation. The suppression of NDRG1 expression also sensitized RA-resistant HCC cells to RA-induced apoptosis, and this sensitization was more apparent in hypoxic HCC cells than in normoxic cells. Glutaredoxin2 expression was down-regulated in NDRG1-suppressed HCC cells. These results show that hypoxia- and RA-inducible NDRG1 expression is responsible for doxorubicin and RA resistance in HCC cells. Thus, the selective interruption of NDRG1 signaling may prove to be therapeutically useful in HCCs, particularly in the advanced infiltrative type of tumors exposed to hypoxic environments.

Genetic and expression alterations in association with the sarcomatous change of cholangiocarcinoma cells

Cholangiocarcinoma (CC) is an intrahepatic bile duct carcinoma with a high mortality rate and a poor prognosis. Sarcomatous change/epithelial mesenchymal transition (EMT) of CC frequently leads to aggressive intrahepatic spread and metastasis. The aim of this study was to identify the genetic alterations and gene expression pattern that might be associated with the sarcomatous change in CC. Previously, we established 4 human CC cell lines (SCK, JCK1, Cho-CK, and Choi-CK). In the present study, we characterized a typical sarcomatoid phenotype of SCK, and classified the other cell lines according to tumor cell differentiation (a poorly differentiated JCK, a moderately differentiated Cho-CK, and a well differentiated Choi-CK cells), both morphologically and immunocytologically. We further analyzed the genetic alterations of two tumor suppressor genes (p53 and FHIT) and the expression of Fas/FasL gene, well known CC-related receptor and its ligand, in these four CC cell lines. The deletion mutation of p53 was found in the sarcomatoid SCK cells. These cells expressed much less Fas/FasL mRNAs than did the other ordinary CC cells. We further characterize the gene expression pattern that is involved in the sarcomatous progression of CC, using cDNA microarrays that contained 18,688 genes. Comparison of the expression patterns between the sarcomatoid SCK cells and the differentiated Choi-CK cells enabled us to identify 260 genes and 247 genes that were significantly over-expressed and under-expressed, respectively. Northern blotting of the 14 randomly selected genes verified the microarray data, including the differential expressions of the LGALS1, TGFBI, CES1, LDHB, UCHL1, ASPH, VDAC1, VIL2, CCND2, S100P, CALB1, MAL2, GPX1, and ANXA8 mRNAs. Immunohistochemistry also revealed in part the differential expressions of these gene proteins. These results suggest that those genetic and gene expression alterations may be relevant to the sarcomatous change/EMT in CC cells.

Fenretinide-induced caspase-8 activation and apoptosis in an established model of metastatic neuroblastoma

BACKGROUND

Resistance of high-risk metastatic neuroblastoma (HR-NB) to high dose chemotherapy (HD-CT) raises a major therapeutic challenge in pediatric oncology. Patients are treated by maintenance CT. For some patients, an adjuvant retinoid therapy is proposed, such as the synthetic retinoid fenretinide (4-HPR), an apoptotic inducer. Recent studies demonstrated that NB metastasis process is enhanced by the loss of caspase-8 involved in the Integrin-Mediated Death (IMD) process. As the role of caspase-8 appears to be critical in preventing metastasis, we aimed at studying the effect of 4-HPR on caspase-8 expression in metastatic neuroblasts.

METHODS

We used the human IGR-N-91 MYCN-amplified NB experimental model, able to disseminate in vivo from the primary nude mouse tumor xenograft (PTX) into myocardium (Myoc) and bone marrow (BM) of the animal. NB cell lines, i.e., IGR-N-91 and SH-EP, were treated with various doses of Fenretinide (4-HPR), then cytotoxicity was analyzed by MTS proliferation assay, apoptosis by the propidium staining method, gene or protein expressions by RT-PCR and immunoblotting and caspases activity by colorimetric protease assays.

RESULTS

The IGR-N-91 parental cells do not express detectable caspase-8. However the PTX cells established from the primary tumor in the mouse, are caspase-8 positive. In contrast, metastatic BM and Myoc cells show a clear down-regulation of the caspase-8 expression. In parallel, the caspases -3, -9, -10, Bcl-2, or Bax expressions were unchanged. Our data show that in BM, compared to PTX cells, 4-HPR up-regulates caspase-8 expression that parallels a higher sensitivity to apoptotic cell death. Stable caspase-8-silenced SH-EP cells appear more resistant to 4-HPR-induced cell death compared to control SH-EP cells. Moreover, 4-HPR synergizes with drugs since apoptosis is restored in VP16- or TRAIL-resistant-BM cells. These results demonstrate that 4-HPR in up-regulating caspase-8 expression, restores and induces apoptotic cell death in metastatic neuroblasts through caspase-8 activation.

CONCLUSION

This study provides basic clues for using fenretinide in clinical treatment of HR-NB patients. Moreover, since 4-HPR induces cell death in caspase-8 negative NB, it also challenges the concept of including 4-HPR in the induction of CT of these patients.

Polyinosinic-polycytidylic acid liposome induces human hepatoma cells apoptosis which correlates to the up-regulation of RIG-I like receptors

Toll-like receptor 3 and RIG-I like receptors (RLRs; MDA5, RIG-I) are involved in cell growth inhibition and apoptosis. However, the toll-like receptor 3-related apoptotic pathway is insensitive to direct polyinosinic-polycytidylic acid (dsRNA analog) stimulation in hepatoma cells. To determine whether the strategy of transferring polyinosinic-polycytidylic acid into cells (polyinosinic-polycytidylic acid-liposome) could induce apoptosis in hepatoma cells through cytoplasm receptors, we examined the responses of innate immune receptors RLRs and toll-like receptor 3 in response to different stimulation. We found that the apoptosis could exclusively be detected under polyinosinic-polycytidylic acid-liposome stimulation, which involved the activation of the caspase pathway. Besides, the expression of RIG-I, MDA5, IFNbeta and interferon-stimulated gene 15 was increased significantly at an early stage. Moreover, the growth inhibition of polyinosinic-polycytidylic acid-liposome was confirmed in a mouse model. Taken together, these results suggest polyinosinic-polycytidylic acid-liposome could be used as a potential apoptotic agent in hepatocellular carcinoma cells and imply a potential therapeutic strategy.

Involvement of caspases and apoptosis-inducing factor in bufotalin-induced apoptosis of Hep 3B cells

Bufotalin is one of the bufadienolides isolated from Formosan Ch'an Su, which is made of the skin and parotid glands of toads. Ingestion of toad venom results in severe morbidity and high mortality. Although Ch'an Su is clinically toxic, it has been used as an important traditional Chinese medicine for heart failure and pains. In this study, bufotalin-induced apoptosis in human hepatocellular carcinoma Hep 3B cells was investigated. The results indicate that externalization of phosphatidylserine, accumulation of sub-G(1) cells, fragmentation of DNA, and formation of apoptotic bodies were observed in bufotalin-treated Hep 3B cells. The signaling pathway might be via the activation of caspase-8, increase in mitochondrial tBid, disruption of mitochondrial membrane potential, and translocation of apoptosis-inducing factor (AIF). Active caspase-8 might activate caspase-9 and caspase-3 leading to the cleavage of nuclear PARP. Presence of AIF and cleaved PARP in the nuclei might lead to DNA fragmentation. Caspase-8 inhibitor (Z-IETD) or wide-ranging caspase inhibitor (Z-VAD) significantly suppressed the bufotalin-induced apoptosis, while the anti-Fas neutralization antibody had no effect. These data suggest that bufotalin-induced apoptosis in Hep 3B cells might involve caspases and AIF.

Fenretinide-induced apoptosis of Huh-7 hepatocellular carcinoma is retinoic acid receptor beta dependent

BACKGROUND

Retinoids are used to treat several types of cancer; however, their effects on liver cancer have not been fully characterized. To investigate the therapeutic potential of retinoids on hepatocellular carcinoma (HCC), the present study evaluates the apoptotic effect of a panel of natural and synthetic retinoids in three human HCC cell lines as well as explores the underlying mechanisms.

METHODS

Apoptosis was determined by caspase-3 cleavage using western blot, DNA double-strand breaks using TUNEL assay, and phosphatidylserine translocation using flow cytometry analysis. Gene expression of nuclear receptors was assessed by real-time PCR. Transactivation assay and chromatin immunoprecipitation (ChIP) were conducted to evaluate the activation of RXRalpha/RARbeta pathway by fenretinide. Knockdown of RARbeta mRNA expression was achieved by siRNA transfection.

RESULTS

Our data revealed that fenretinide effectively induces apoptosis in Huh-7 and Hep3B cells. Gene expression analysis of nuclear receptors revealed that the basal and inducibility of retinoic acid receptor beta (RARbeta) expression positively correlate with the susceptibility of HCC cells to fenretinide treatment. Furthermore, fenretinide transactivates the RXRalpha/RARbeta-mediated pathway and directly increases the transcriptional activity of RARbeta. Knockdown of RARbeta mRNA expression significantly impairs fenretinide-induced apoptosis in Huh-7 cells.

CONCLUSION

Our findings reveal that endogenous expression of retinoids receptor RARbeta gene determines the susceptibility of HCC cells to fenretinide-induced apoptosis. Our results also demonstrate fenretinide directly activates RARbeta and induces apoptosis in Huh-7 cells in a RARbeta-dependent manner. These findings suggest a novel role of RARbeta as a tumor suppressor by mediating the signals of certain chemotherapeutic agents.

MAPK inhibitors and pifithrin-alpha block cinnamaldehyde-induced apoptosis in human PLC/PRF/5 cells

Cinnamaldehyde (Cin) has been shown to be effective in inducing apoptotic cell death in a number of human cancer cells. The aim of this study was to investigate the effect of pifithrin-alpha (PFTalpha; a specific p53 inhibitor) and mitogen-activated protein kinases (MAPKs) inhibitors [namely SP600125 (a specific JNK inhibitor), SB203580 (a specific p38 inhibitor) and PD98059 (a specific ERK inhibitor)] on apoptotic signaling transduction mechanism induced by Cin in human hepatoma PLC/PRF/5 (CD95-negative) cells. Using XTT assay, Cin exhibited a powerful cytotoxic effect and apoptotic induction in PLC/PRF/5 cells. Apoptosis was elicited when cells were treated with 1 microM Cin as characterized by morphological changes and the appearance of phosphatidylserine on the outer surface of the plasma membrane. Cin down-regulated the expression of Bcl-(XL), up-regulated mutant p53 and Bax proteins and promoted caspase-3 to active forms, as well as cleaving poly (ADP-ribose) polymerase (PARP) in a time-dependent pattern. This could be supported by the activation and phosphorylation of MAPKs, including JNK, ERK and p38 kinases. Pre-incubation with PFTalpha and specific MAPK inhibitors significantly diminished the effect of Cin-induced apoptosis. The activities of anti-apoptotic (Bcl-(XL)) and pro-apoptotic (Bax) proteins were remarkably affected by PFTalpha and PD98059 pre-treatment. PFTalpha effectively blocked PARP cleavage in cells treated with Cin, and also markedly prevented the phosphorylation of JNK, p38 and ERK proteins. These results suggest that p53 induction and MAPK signaling pathways are required for Cin-mediated apoptosis in PLC/PRF/5 cells.

The unhydrolyzable fenretinide analogue 4-hydroxybenzylretinone induces the proapoptotic genes GADD153 (CHOP) and Bcl-2-binding component 3 (PUMA) and apoptosis that is caspase- dependent and independent of the retinoic acid receptor

The synthetic retinoid N-(4-hydroxyphenyl)retinamide (4-HPR) induces apoptosis in a variety of cell lines and has shown promise as an anticancer agent both in vitro and in vivo. The clinical dose of 4-HPR, however, is limited by residual-associated toxicities, indicating a need for a less toxic drug. In this study, we show that 4-hydroxybenzylretinone (4-HBR), the unhydrolyzable analogue of 4-HPR, is effective in producing apoptosis in a variety of 4-HPR-sensitive cell lines, including breast cancer, neuroblastoma, and leukemia cells. We also show through the use of a pan-caspase inhibitor that this 4-HBR-induced apoptosis is dependent, at least in part, on caspase activity. 4-HBR is shown to exhibit binding to the retinoic acid receptors (RAR) at concentrations necessary to induce cell death and induces expression of all-trans-retinoic acid-responsive genes that can be blocked by a RAR pan-antagonist. However, through the use of this RAR pan-antagonist, 4-HBR-induced apoptosis and cell death is shown to be independent of the RAR signaling pathway. To further characterize the mechanism of action of 4-HBR, expression of the endoplasmic reticulum stress-induced genes GADD153 and Bcl-2-binding component 3 was examined. These mRNAs are shown to be rapidly induced in 4-HBR-treated and 4-HPR-treated breast cancer cells, and this up-regulation is also shown to be independent of the RARs. These results suggest that a stress-mediated apoptotic cascade is involved in the mechanism of action of these retinoids.

Characterization of cell death events induced by anti-neoplastic drugs cisplatin, paclitaxel and 5-fluorouracil on human hepatoma cell lines: Possible mechanisms of cell resistance

Two different hepatoma cell lines were incubated for 48h with chemotherapeutic drugs cisplatin, paclitaxel and 5-FU to determine their ability to induce cytotoxicity and DNA fragmentation as well as to modify the expression of some cell death-related genes that could be involved in the resistance to therapy. We observed that cisplatin and paclitaxel induced cytotoxicity, but significant differences between both cell lines, were found only in the case of paclitaxel. At 48h, apoptosis was clearly present in Hep3B cells treated with cisplatin and HepG2 cells treated with paclitaxel. 5-FU induced cytotoxicity in both cell lines but only at higher concentrations than the other two drugs, triggering apoptosis and necrosis in HepG2 cells and only necrosis in Hep3B. When a time course was performed for the first 8h of treatment to elucidate the initial mechanism of cell death responsible for DNA fragmentation, we observed that 5-FU in Hep3B, and cisplatin in both cell lines, induces primary necrosis, whereas at the concentration tested here, paclitaxel clearly triggers apoptosis in both cell lines. HepG2 cells were weakly sensitive to 5-FU in the first 8h of treatment, so the primary mechanism of cell death was not clear, but results seem to indicate that it could be apoptosis. At 48h, Bax was not up-regulated with any of the treatments, whereas cisplatin was able to induce Bcl-xL down-regulation in both cell lines. Treatment with 5-FU also down-regulated Bcl-xL in HepG2 cells. We also measured variations in the expression of survivin, an inhibitor of apoptosis that has also been involved in mitototic catastrophe. Hep3B cells seem to show an increase in protein levels with all treatments. Exposure to paclitaxel resulted in the highest effect. In the case of HepG2 cells, there was a decrease in survivin expression when cells were treated with 5FU and paclitaxel, both treatments showing complete loss of the protein. Using an antibody that recognizes unprocessed caspase-3, we observed that the enzyme was assumingly activated in HepG2 cells treated with 5FU and paclitaxel, but only weakly after treatment with cisplatin. Hep3B cells did not show activation since the levels of the pro-enzyme remained the same as that in the control. In conclusion, the three drugs tested in this study could induce cell death, with paclitaxel being more effective inducing apoptosis. 5FU was only effective at high doses and its mechanism seems to be primarily related to necrosis in Hep3B and probably apoptosis in HepG2. Cisplatin mechanism of cell death is probably mediated by the decrease in anti-apoptotic protein Bcl-xL whereas paclitaxel and 5FU are decreasing the apoptosis inhibitor survivin. According to pro-enzyme levels, caspase-3 was only activated in HepG2 cells, whereas in the case of Hep3B cells the mechanisms of toxicity appear to be caspase-3-independent at the time and concentrations tested in this study. The resistance of Hep3B cells to death induced by chemotherapy could be related to an increase in the expression of IAP survivin, which can decrease cell response to the treatment or even switch the type of death from apoptosis to another kind, making therapy less efficient.

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.

Inhibition of cell proliferation and induction of apoptosis by genistein in experimental hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the leading cause of cancer related deaths in the world, with increasing incidence in many developed countries. Epidemiological data suggest that consumption of soy products may be associated with a decreased risk of cancer. We investigate the effects of genistein on cell proliferation, apoptosis and caspase-3 in DEN induced (200 mg/kg body weight; by single intraperitoneal injection) and Phenobarbital promoted (0.05% through drinking water for 14 successive weeks) cancer-bearing rats. Immunohistochemistry was employed to detect cell proliferating markers proliferating cell nuclear antigen (PCNA), DNA fragmentation was determined by agarose gel electrophoresis and terminal deoxynucleatide transferase dUTP nick labeling (TUNEL) staining and caspase by enzyme-linked immunosorbent assay. We found inhibition of cell proliferation, induction of apoptosis and activation of caspase-3 in genistein treated animals. From these results, we conclude that genistein inhibit cell proliferation, induced apoptosis. This activation of caspsase-3 in genistein treated liver cancer bearing animals correlated well with its apoptosis inducing effect.

Calpeptin provides functional neuroprotection to rat retinal ganglion cells following Ca2+ influx

Apoptosis of retinal ganglion cells (RGCs) impairs vision in glaucoma patients. RGCs are also degenerated in multiple sclerosis (MS), resulting in loss of visual perception in MS patients. We examined the involvement of calpain and caspase cascades in apoptosis of the rat retinal ganglion cell line RGC-5 following 24 h of exposure to 250 nM ionomycin (IMN) or 300 units/ml interferon-gamma (IFN-gamma) and then evaluated functional neuroprotection with 2 microM calpeptin (CP, a calpain-specific inhibitor). Morphological and biochemical features of apoptosis were detected in RGC-5 cells following exposure to IMN or IFN-gamma. Fura-2 assay determined significant increases in intracellular free [Ca2+] following exposure to IMN or IFN-gamma. Pretreatment with CP for 1 h prevented Ca2+ influx, proteolytic activities, and apoptosis in RGC-5 cells. Western blot analyses showed an increase in activities of calpain and caspase-12, upregulation of Bax:Bcl-2 ratio, release of cytochrome c from mitochondria, and increase in caspase-9 and caspase-3 activities during apoptosis. Increased caspase-3 activity was also confirmed by a colorimetric assay. Activation of caspase-8 and cleavage of Bid to tBid in RGC-5 cells following exposure to IFN-gamma indicated co-operation between extrinsic and intrinsic pathways of apoptosis. Patch-clamp recordings showed that pretreatment with CP attenuated apoptosis and maintained normal whole-cell membrane potential, indicating functional neuroprotection. Taken together, our results demonstrated that Ca2+ overload could be responsible for activation of calpain and caspase cascades leading to apoptotic death of RGC-5 cells and CP provided functional neuroprotection.

Novel mechanisms of target cell death and survival and of therapeutic action of IVIg in Pemphigus

Pemphigus vulgaris (PV) is a potentially lethal mucocutaneous blistering disease characterized by cell-cell detachment within the stratified epithelium (acantholysis) caused by IgG autoantibodies. Intravenous immunoglobulin (IVIg) therapy effectively treats PV, but the mechanism is not fully understood. To further understand acantholysis and the efficacy of IVIg, we measured effects of IgG fractions from PV patients on keratinocyte death processes. Using IgGs from representative PV patients who improved with IVIg, we identified apoptotic and oncotic signaling pathways in in vitro and in vivo PV models. We identified two groups of PV patients, each producing autoantibodies activating predominantly either apoptotic or oncotic cell death pathway. Experimental treatments with caspase 3 or calpain inhibitors demonstrated that PV IgGs induced acantholysis through both pathways. Upstream, the apoptotic signaling involved activation of caspases 8 and 3 and up-regulation of Fas ligand mRNA, whereas calpain-mediated cell death depended on elevated intracellular free Ca(2+). IVIg reduced PV IgG-mediated acantholysis and cell death and up-regulated the caspase inhibitor FLIP and the calpain inhibitor calpastatin. These results indicate that in different PV patients, IgG-induced acantholysis proceeds predominantly via distinct, yet complementary, pathways of programmed cell death differentially mediated by apoptosis and oncosis effectors, with IVIg protecting target cells by up-regulating endogenous caspase and calpain inhibitors.

Susceptibility of cholangiocarcinoma cells to parthenolide-induced apoptosis

Cholangiocarcinomas are intrahepatic bile duct carcinomas that are known to have a poor prognosis. Sesquiterpene lactone parthenolide, which is the principal active component in medicinal plants, has been used to treat tumors. Parthenolide effectively induced apoptosis in all four cholangiocarcinoma cell lines in a dose-dependent manner. However, the sarcomatous SCK cells were more sensitive to parthenolide than the other adenomatous cholangiocarcinoma cells. Therefore, this study investigated whether or not the expression of p53, the Fas/Fas ligand (FasL), Bcl-2/Bcl-X(L) determines the enhanced drug susceptibility of SCK cells. The results showed that Bcl-2 family molecules, such as Bid, Bak, and Bax, are involved in the parthenolide-induced apoptosis and that the defective expression of Bcl-X(L) might contribute to the higher parthenolide sensitivity in the SCK cells than in the other adenomatous cholangiocarcinoma cells. SCK cells, which stably express Bcl-X(L), were resistant to parthenolide, whereas Bcl-X(L)-positive Choi-CK cells transfected with the antisense Bcl-X(L) showed a higher parthenolide sensitivity than the vector control cells. Molecular dissection revealed that Bcl-X(L) inhibited the translocation of Bax to the mitochondria, decreased the generation of intracellular reactive oxygen species, reduced the mitochondrial transmembrane potential (deltapsi(m)), decreased the release of cytochrome c, decreased the cleavage of poly(ADP-ribose) polymerase, and eventually inhibited apoptotic cell death. These results suggest that parthenolide effectively induces oxidative stress-mediated apoptosis, and that the susceptibility to parthenolide in cholangiocarcinoma cells might be modulated by Bcl-X(L) expression in association with Bax translocation to the mitochondria.

Apoptotic events induced by naturally occurring retinoids ATRA and 13-cis retinoic acid on human hepatoma cell lines Hep3B and HepG2

Two hepatoma cell lines were incubated for 72 h with ATRA and its analog 13cisRA and according to MTT assay, Hep3B cells were highly susceptible whereas HepG2 cells were more resistant to the treatment. At the high concentration of 166 microM, retinoids were able to induce apoptosis in both cell lines and the highest effect was observed in HepG2 cells treated with ATRA. TUNEL-based photometric ELISA showed that at the same retinoid concentration tested by flow cytometry, both cell lines showed apoptosis whereas plasma membranes were not significantly disrupted. Inhibitors of apoptosis Bcl-xL and survivin were downregulated in Hep3B cells by treatment with both retinoids. Bax, a pro-apoptotic protein, was not significantly upregulated in Hep3B cells, but was slightly increased in HepG2 cells treated with 13cisRA. Both procaspase-3 and procaspase-8 were cleaved in Hep3B cells, suggesting apoptosis could be triggered through the extrinsic pathway. In the case of HepG2 cells, lack of caspase activation suggests a mechanism dependent on other kind of proteases.

Effects of antioxidants and caspase-3 inhibitor on the phenylethyl isothiocyanate-induced apoptotic signaling pathways in human PLC/PRF/5 cells

Phenylethyl isothiocyanate (PEITC) is a well recognized potential chemopreventive compound against human cancers. In this study, the molecular mechanism of PEITC-induced apoptosis was examined with two antioxidants (N-acetyl-cysteine and vitamin E) and a caspase-3 inhibitor (z-DEVD-fmk). Results demonstrated that PEITC significantly induced human hepatoma PLC/PRF/5 (CD95-negative) cells undergoing apoptosis. Treatment with 0 approximately 10 microM PEITC-triggered cell apoptosis as revealed by the externalization of annexin V-targeted phosphatidylserine and the subsequent appearance of sub-G1 population. Results also displayed that PEITC-induced apoptosis involves the up-regulation of p53 and Bax protein, down-regulation of the XIAP, Bcl-2, Bcl-(XL) and Mcl-1 proteins, cleavage of Bid, and the release of cytochrome c and Smac/Diablo, which were accompanied by the activation of caspases -9, -3 and -8. PEITC-induced the generation of reactive oxygen species and the decrease of mitochondrial membrane potential (Deltapsim) in a time-dependent pattern. N-acetyl-cysteine and vitamin E at 100 microM, and z-DEVD-fmk at 50 microM markedly blocked PEITC-induced apoptosis, which was demonstrated by a decline in the reactive oxygen species generation and the release of the cytochrome c and Smac/Diablo from mitochondria to the cytosol. N-acetyl-cysteine, vitamin E and z-DEVD-fmk also prevented the PEITC in inducing the loss of Deltapsim. They also affected the activity of XIAP and Bax proteins. Taken together, these studies suggest that PEITC is an apoptotic inducer that acts on the mitochondria and the feedback amplification loop of caspase-8/Bid pathways in PLC/PRF/5 cells.

Fast neutrons-induced apoptosis is Fas-independent in lymphoblastoid cells

We have previously shown that ionizing radiation-induced apoptosis in human lymphoblastoid cells differs according to their p53 status, and that caspase 8-mediated cleavage of BID is involved in the p53-dependent pathway. In the present study, we investigated the role of Fas signaling in caspase 8 activation induced by fast neutrons irradiation in these cells. Fas and FasL expression was assessed by flow cytometry and by immunoblot. We also measured Fas aggregation after irradiation by fluorescence microscopy. We found a decrease of Fas expression after irradiation, but no change in Fas ligand expression. We also showed that, in contrast to the stimulation of Fas by an agonistic antibody, Fas aggregation did not occur after irradiation. Altogether, our data strongly suggest that fast neutrons induced-apoptosis is Fas-independent, even in p53-dependent apoptosis.

Apoptotic and anti-angiogenic strategies in liver and gastrointestinal malignancies

Inappropriate suppression of apoptosis is strongly implicated in tumorigenesis. Tumor development is heralded by the mutation of tumor suppressor genes and overexpression of anti-apoptotic genes permitting cell survival. Thus, inducing the apoptotic process in various ways can be applied to cancer management. Besides, angiogenesis is a crucial process for tumor growth and metastasis. New strategies targeting fundamental play-markers of the angiogenic process are currently under investigation.

Apoptotic effects of extract from Antrodia camphorata fruiting bodies in human hepatocellular carcinoma cell lines

The fruiting body of Antrodia camphorata is well known in Taiwan as a traditional medicine for treating cancer and inflammation. The purpose of this study was to evaluate the apoptotic effects of ethylacetate extract from A. camphorata (EAC) fruiting bodies in two human liver cancer cell lines, Hep G2 and PLC/PRF/5. Treatment with EAC decreased the cell growth of Hep G2 and PLC/PRF/5 cells in a dose dependent manner. In Fas/APO-1 positive-Hep G2 cells, EAC increased the expression level of Fas/APO-1 and its two forms of ligands, membrane-bound Fas ligand (mFasL) and soluble Fas ligand (sFasL), in a p53-indenpendent manner. In addition, EAC also initiated mitochondrial apoptotic pathway through regulation of Bcl-2 family proteins expression, release of cytochrome c, and activation of caspase-9 both in Hep G2 and PLC/PRF/5 cells. Furthermore, EAC also inhibited the cell survival signaling by enhancing the amount of IkappaBalpha in cytoplasm and reducing the level and activity of NF-kappaB in the nucleus, and subsequently attenuated the expression of Bcl-X(L) in Hep G2 and PLC/PRF/5 cells. EAC therefore decreased the cell growth and induced apoptosis both in Hep G2 and PLC/PRF/5 cells.

Identification of the Genes Involved in Enhanced Fenretinide-Induced Apoptosis by Parthenolide in Human Hepatoma Cells

Fenretinide (N-4-hydroxyphenyl retinamide, 4HPR) is a synthetic anticancer retinoid that is a well-known apoptosis-inducing agent. Recently, we observed that the apoptosis induced by fenretinide could be effectively enhanced in hepatoma cells by a concomitant treatment with parthenolide, which is a known inhibitor of nuclear factor-kappaB (NF-kappaB). Furthermore, treatment with fenretinide triggered the activation of NF-kappaB during apoptosis, which could be substantially inhibited by parthenolide, suggesting that NF-kappaB activation during fenretinide-induced apoptosis has an antiapoptotic effect. This study investigated the molecular mechanism of this apoptotic potentiation by NF-kappaB inhibition. The genes involved in the enhanced fenretinide-induced apoptosis by parthenolide were identified using the differential display-PCR method and subsequent Northern blot or semiquantitative reverse transcriptase PCR analysis. This study identified 35 apoptosis-related genes including 12 unknown genes that were either up- or down-regulated by parthenolide. Interestingly, one up-regulated gene (HA1A2) was isolated and cloned from the liver cDNA, and was found to be identical to ANKRD1, which is also referred to as the CARP gene. Compared with controls treated with an empty vector or with antisense cDNA, the ectopic expression of ANKRD1 led to reduced colony formation and to enhanced apoptotic cell death in hepatoma cells. These results suggest that ANKRD1 and the other genes, whose expressions were substantially modulated by the parthenolide-mediated inhibition of NF-kappaB activation, play roles in the enhanced drug-induced apoptosis. In addition, this study suggests that those identified genes may be useful in anticancer strategies against hepatoma.

Effect of the Synthetic Retinoid Fenretinide on Circulating Free Prostate-Specific Antigen, Insulin-Like Growth Factor-I, and Insulin-Like Growth Factor Binding Protein-3 Levels in Men with Superficial Bladder Cancer

PURPOSE

Fenretinide (4-HPR) is a synthetic retinoid that has shown a preventive activity in prostate cancer animal models.

EXPERIMENTAL DESIGN

We measured the changes in total and free prostate-specific antigen (PSA) and its association with insulin-like growth factor I (IGF-I) and IGFBP-3 levels after 1 year of treatment in 24 subjects given 4-HPR and 24 control subjects enrolled in a randomized bladder cancer prevention trial.

RESULTS

No significant effect of 4-HPR was observed on total and free fraction of PSA levels. The median percentage [95 confidence interval (95% CI)] change for % free PSA and total PSA in the 4-HPR and the control group were, respectively, 7.6 (95% CI, -4.0 to 69.3) versus 5.1 (95% CI, -21.4 to 59.8) and -7.8 (95% CI, -18.2 to 52.5) versus -12.3 (95% CI, -44.6 to 9.6). However, in patients ages <60 years, there was a trend to an increase of total free PSA and % free PSA after treatment with 4-HPR that was different from a trend to a decrease in the control group (P = 0.002 and 0.052, respectively). The interaction between age and treatment was statistically significant on free PSA (P = 0.001). A similar pattern was noted with smoking status (P = 0.011 for the interaction on free PSA). No association was observed between PSA levels and IGF-I or IGFBP-3 levels.

CONCLUSIONS

We conclude that 4-HPR has no significant effect on circulating PSA, but it increases significantly free PSA levels in subjects younger than 60 years and in nonsmokers. These effects might support an activity in prostate cancer prevention but further studies are required.

8-Amino-adenosine is a potential therapeutic agent for multiple myeloma

Multiple myeloma (MM) is a malignancy of clonal B-cells that accounts for 10% of all hematologic malignancies. We have shown previously that a novel purine analogue, 8-chloro-adenosine, has significant activity for MM in preclinical studies. Objective: Using MM cell lines, we investigated the molecular mechanism of related congener of adenosine, 8-amino-adenosine (8-NH2-Ado). Methods: We employed biological and biochemical assays in MM cell lines to evaluate the clinical potential of 8-NH2-Ado. Results: In MM cell lines both sensitive and resistant to conventional chemotherapies, 8-NH2-Ado is cytotoxic, with IC50 ranging from 300 nmol/L to 3 μmol/L. A mouse leukemic cell line lacking adenosine kinase activity was resistant to 8-NH2-Ado, indicating that phosphorylation of 8-NH2-Ado to its triphosphate form is required for cytotoxicity. A 4-hour incubation of MM cells with 10 μmol/L analogue resulted in an accumulation of &gt;7 mmol/L 8-NH2-ATP with a parallel decline in the endogenous ATP levels. Accumulation of 8-NH2-ATP was dependent on both exogenous concentration of 8-NH2-Ado and incubation time. The accumulation of 8-NH2-ATP was accompanied by a decrease in both RNA and DNA synthesis. The mechanism of 8-NH2-Ado-mediated cytotoxicity was due to apoptosis as measured by an increase in Annexin V binding, a decrease in mitochondrial membrane potential, an increase in caspase activity, cleavage of caspase substrates, and an increase in cells with a sub-G1 DNA content. Conclusion: Based on these results, we conclude that 8-NH2-Ado may hold great potential as a therapeutic agent for the treatment of MM.

An antagonist of retinoic acid receptors more effectively inhibits growth of human prostate cancer cells than normal prostate epithelium

Screening of synthetic retinoids for activity against prostate carcinoma cell lines has identified antagonists of retinoic acid receptors (RARs) as potent growth inhibitors (Hammond et al, 2001, Br J Cancer 85, 453–462). Here we report that 5 days of exposure to a high-affinity pan-RAR antagonist (AGN194310) abolished growth of prostate carcinoma cells from 14 out of 14 patients, with half-maximal inhibition between 200 and 800 nM. It had similar effects (at ∼250 nM) on the prostate carcinoma lines LNCaP, DU-145 and PC-3. AGN194310 inhibited the growth of normal prostate epithelium cells less potently, by 50% at ∼1 μM. The growth of tumour cells was also inhibited more than that of normal cells when RARβ together with RARγ, but not RARα alone, were antagonised. Treatment of LNCaP cells with AGN194310 arrested them in G1 of cell cycle within 12 h, with an accompanying rise in the level of p21^waf1. The cells underwent apoptosis within 3 days, as indicated by mitochondrial depolarisation, Annexin V binding and DNA fragmentation. Apoptosis was caspase-independent: caspases were neither cleaved nor activated, and DNA fragmentation was unaffected by the pan-caspase inhibitor Z-VAD-FMK. The ability of AGN 194310 to induce apoptosis of prostate cancer cells and its differential effect on malignant and normal prostate epithelial cells suggests that this compound may be useful in the treatment of prostate cancer.

Cadmium induces caspase-independent apoptosis in liver Hep3B cells: role for calcium in signaling oxidative stress-related impairment of mitochondria and relocation of endonuclease G and apoptosis-inducing factor

Cadmium-induced cellular toxicity has been related to necrosis and/or caspase-dependent apoptosis. In the present study, we show that, on cadmium exposure, the human hepatocarcinoma Hep3B cells undergo caspase-independent apoptosis associated with nuclear translocation of endonuclease G and apoptosis-inducing factor, two mitochondrial apoptogenic proteins. Release of these proteins is likely related to calcium-induced alteration of mitochondrial homeostasis. Indeed, it was first preceded by a rapid and sustained increase in cytoplasmic calcium and then by a coincident loss in mitochondrial membrane potential and production of reactive oxygen species. Bapta-AM (acetoxymethyl ester of 5, 5'-dimethyl-bis (o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid), a calcium chelator, blocked all these events and prevented cadmium-induced apoptosis. Production of reactive oxygen species was inhibited by ruthenium red and rotenone, two mitochondrial inhibitors, and by diphenyleneiodonium, a flavoprotein inhibitor, which also prevented both loss in mitochondrial membrane potential and apoptosis. In addition, Bapta-AM and diphenyleneiodonium were found to almost totally block decreased expression of the mitochondrial anti-apoptotic nuclear factor-kappaB-regulated bcl-x(L) protein in cadmium-treated cells. Taken together, our results show that cadmium induces Hep3B cells apoptosis mainly by calcium- and oxidative stress-related impairment of mitochondria, which probably favors release of apoptosis-inducing factor and endonuclease G.

A Retinoid-Related Molecule that Does Not Bind to Classical Retinoid Receptors Potently Induces Apoptosis in Human Prostate Cancer Cells through Rapid Caspase Activation

Synthetic retinoid-related molecules, such as N-(4-hydroxyphenyl)retinamide (fenretinide) and 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437) induce apoptosis in a variety of malignant cells. The mechanism(s) of action of these compounds does not appear to involve retinoic acid receptors (RARs) and retinoid X receptors (RXRs), although some investigators disagree with this view. To clarify whether some retinoid-related molecules can induce apoptosis without involving RARs and/or RXRs, we used 4-[3-(1-heptyl-4,4-dimethyl-2-oxo-1,2,3,4-tetrahydroquinolin-6-yl)-3-oxo-E-propenyl] benzoic acid (AGN193198) that neither binds effectively to RARs and RXRs nor transactivates in RAR- and RXR-mediated reporter assays. AGN193198 potently induced apoptosis in prostate, breast, and gastrointestinal carcinoma cells and in leukemia cells. AGN193198 also abolished growth (by 50% at 130-332 nM) and induced apoptosis in primary cultures established from prostatic carcinoma (13 patients) and gastrointestinal carcinoma (1 patient). Apoptosis was induced rapidly, as indicated by mitochondrial depolarization and DNA fragmentation. Molecular events provoked by AGN193198 included activation of caspase-3, -8, -9, and -10 (by 4-6 h) and the production of BID/p15 (by 6 h). These findings show that caspase-mediated induction of apoptosis by AGN193198 is RAR/RXR-independent and suggest that this compound may be useful in the treatment of prostate cancer.

Heterogeneous role of caspase-8 in fenretinide-induced apoptosis in epithelial ovarian carcinoma cell lines

The mechanism of action of fenretinide, a synthetic retinoid currently undergoing testing as a chemopreventive and chemotherapeutic agent, is incompletely understood. In the present study, fenretinide caused apoptotic changes, including DNA fragmentation and cleavage of caspase substrates, in six low-passage ovarian cancer cell lines. However, the caspase activation pathway used by this agent varied. Transient transfection of cDNA-encoding cytokine response modifier A (CrmA), a caspase-8 inhibitor, diminished fenretinide-induced death in OV177 cells. Likewise, IETD(OMe)-fluoromethylketone (fmk) inhibited fenretinide-induced apoptosis by >80% in OV177 or OV266 cells and by approximately 50% in OV17, OV167, or OV207 cells. Further analysis demonstrated that inhibition of Fas ligand, tumor necrosis factor-alpha, or TRAIL signaling with blocking reagents did not affect fenretinide-induced apoptosis, raising the possibility that fenretinide activates caspase-8 in a death receptor-independent manner. In contrast, CrmA transfection or IETD(OMe)-fmk treatment did not inhibit fenretinide-induced apoptosis in OV202 cells. These divergent behaviors did not correlate with increased levels of procaspase-10, which is relatively resistant to CrmA and IETD(OMe)-fmk, nor with the expression of procaspase-8 and -9, apoptotic protease activating factor-1, or cellular FLICE-like inhibitory protein. Similarly, fenretinide treatment increased ceramide levels equally in cells that do (OV177) and do not (OV202) rely on caspase-8 to initiate apoptosis. These results indicate that synthetic retinoids can use caspase-8 as an initiating caspase, but they also indicate unexpected heterogeneity in caspase activation pathways among closely related cell lines.

Potent effect of 5-HPBR, a butanoate derivative of 4-HPR, on cell growth and apoptosis in cancer cells

Fenretinide, 4-(N-hydroxyphenyl) retinamide (4-HPR), has demonstrated anticancer activity associated with a favorable toxicity profile and is now being investigated in several clinical trials. However, its plasma levels in patients have been far lower than the effective concentration required to induce apoptosis (usually 10 microM). This result has led to the synthesis of derivatives with better efficacy. Sodium butyrate's potential as an anticancer agent prompted us to synthesize a butanoate derivative of 4-HPR, 5-hydroxyphenyl butanoate retinamide (5-HPBR) and compare it to the parent compound for antitumor potential in vitro. The cytotoxicity of 5-HPBR was 2- to 6-fold greater than that of 4-HPR against cancer cell lines derived from various tissues. In premalignant bronchial cells (BEAS2B), 5-HPBR exhibited about a 10-fold stronger cytotoxicity than did 4-HPR. Normal CHANG liver cells were unaffected by either 4-HPR or 5-HPBR. Subsequent assays using DNA fragmentation, DAPI staining, FACS and Western blotting suggested that the potent inhibitory effect of 5-HPBR is mediated by apoptosis; the exact mechanism appears to differ among cancer cell types. In transcription assays with COS-1 cells, 5-HPBR selectively activated RARbeta and RARgamma but was a weaker ligand for all 3 subtypes of RAR than either all-trans retinoic acid or 4-HPR. Overall, these data suggest that 4-BHPR may be a promising retinoid with enhanced antitumor activity and reduced toxicity.

Novel retinoic acid derivative ABPN has potent inhibitory activity on cell growth and apoptosis in cancer cells

Retinoids are natural and synthetic derivatives of vitamin A that have great promise for cancer therapy and chemoprevention. Of the retinoids developed so far, 4-(N-hydroxyphenyl)retinamide (4-HPR or fenretinide) appears to have the best therapeutic potential in vitro and in vivo and is currently being tested in clinical trials for cancer prevention and therapy. To develop other potentially potent antitumor agents, we synthesized 85 retinoid derivatives. In an initial screening of these synthetic retinoids using the HCT116 colon cancer cell line, we found that 4-amino-2-(butyrylamino)phenyl(2E,4E,6E,8E)-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexenyl)-2,4,6,8-nonatetraenoate (ABPN or CBG41) induced the greatest growth inhibition, with an IC(50) value of 0.6 microM. Subsequent studies in other cancer cell lines indicated that ABPN was much more growth-inhibitory than all-trans retinoic acid or 4-HPR. Compared to 4-HPR, ABPN induced 5.5- to 70.0-fold more growth inhibition in most cancer cells, with the exception of gynecologic cancer cells. In these cells, the antiproliferative effect was only 1.5- to 2.8-fold more than 4-HPR. We examined the molecular mechanism underlying the difference in growth inhibition between 4-HPR and ABPN. DAPI staining, DNA fragmentation, FACS and Western blotting analyses suggest that ABPN induced apoptosis by activating caspase-3 and -8, which may result in increased PARP cleavage. Unlike 4-HPR, ABPN activated all 3 RAR isotypes to an extent similar to AtRA. In addition, ABPN significantly inhibited AP-1 transcriptional activity and thus greatly suppressed the expression of the matrix metalloproteinase -1, -2 and -3 genes, which are involved in tumor invasion. These results suggest that ABPN may be a promising retinoid derivative offering not only enhanced cytotoxicity, but also increased inhibition of tumor invasiveness.

Transcriptional regulation of the human transferrin gene by GADD153 in hepatoma cells

The transcription factor CHOP/GADD153 is reportedly induced by cellular stresses such as UV light, genotoxic agents, and protein misfolding in the endoplasmic reticulum. However, the mechanism whereby induction of the GADD153 gene is linked to a downstream pathway is still unclear. Previously, we observed that a synthetic retinoid N-(4-hydroxyphenyl)retinamide (4HPR) effectively impaired cell growth and survival (induction of growth arrest and apoptosis) in human hepatoma cells, which was accompanied by over expression of GADD153. Furthermore, GADD153-transfected Hep 3B cells were growth arrested and were sensitized to drug-induced apoptosis. Thus, in this study, we used suppression subtractive hybridization (SSH) to identify GADD153 target genes that were up-regulated or down-regulated in the GADD153 transfectants. We screened 614 sequence-verified clones by Northern blotting, of which 42 genes were scored as over expressed and 17 genes as under expressed in GADD153 transfectants compared with control vector transfectants. Of those genes, 49 corresponded to known genes in public databases. Among them, we further verified that the expression of transferrin (Tf), which is a negative acute-phase protein and is essential to cell survival as a growth factor, was highly modulated by drug-induced GADD153 over expression or by in vitro transfection. GADD153 significantly antagonized the C/EBP (C/EBP-alpha, -beta, and -delta)-mediated transcriptional activation of the Tf gene. In conclusion, Tf and other target genes identified may play a functional role in the downstream pathway of GADD153.

GADD153-mediated anticancer effects of N-(4-hydroxyphenyl)retinamide on human hepatoma cells

The anticancer effects of N-(4-hydroxyphenyl)retinamide (4HPR), a potential chemopreventive or chemotherapeutic retinamide, are thought to be derived from its ability to induce apoptosis. However, the mechanism of apoptosis induced by 4HPR remains unclear. Thus, this study was designed to identify the gene(s) responsible for induction of apoptosis by 4HPR. Apoptosis was effectively induced by 4HPR in human hepatoma cells. Using the differential display-PCR method, a gene involved in the response to 4HPR was identified, and cells in which the expression of that gene was modulated were analyzed for survival, induction of apoptosis, and cell cycle. GADD153, a gene involved in growth arrest and apoptosis, was preferentially expressed in human hepatoma cells as well as in other cancer cells during 4HPR-induced apoptosis. 4HPR regulates GADD153 expression at the post-transcriptional level in Hep 3B cells and at the transcriptional and post-transcriptional levels in SK-HEP-1 cells, when assayed by in vitro transfection and mRNA stability experiments. To determine the role of the GADD153 protein overexpression that is induced by 4HPR, Hep 3B cells with ectopic overexpression of GADD153 were found to be growth-arrested (at G(1)) and readily underwent apoptosis following treatment with 4HPR or even when they reached confluence. N-Acetyl-l-cysteine or GADD153 antisense significantly protected the cells from 4HPR-induced apoptosis, accompanying by the inhibition of GADD153 overexpression. Parthenolide-mediated overexpression of GADD153 resulted in enhanced 4HPR-induced apoptosis. These results suggest that GADD153 overexpression induced by 4HPR may contribute to the anticancer effects (induction of apoptosis and growth arrest) of 4HPR on cancer cells.

Oxidative stress-mediated apoptosis. The anticancer effect of the sesquiterpene lactone parthenolide

The sesquiterpene lactone parthenolide, the principal active component in medicinal plants, has been used conventionally to treat migraines, inflammation, and tumors. However, the antitumor effects of parthenolide and the mechanism(s) involved are poorly understood. We found that parthenolide effectively inhibits hepatoma cell growth in a tumor cell-specific manner and triggers apoptosis of hepatoma cells. Parthenolide triggered apoptosis in invasive sarcomatoid hepatocellular carcinoma cells (SH-J1) as well as in other ordinary hepatoma cells at 5-10 microm concentrations and arrested the cell growth (at G(2)/M) at sublethal concentrations (1-3 microm). During parthenolide-induced apoptosis, depletion of glutathione, generation of reactive oxygen species, reduction of mitochondrial transmembrane potential, activation of caspases (caspases-7, -8, and -9), overexpression of GADD153 (an oxidative stress or anticancer agent inducible gene), and subsequent apoptotic cell death was observed. This induced apoptosis could be effectively inhibited or abrogated by an antioxidant N-acetyl-l-cysteine, whereas l-buthionine-(S,R)-sulfoximine enhanced it. Furthermore, stable overexpression of GADD153 sensitized the cells to apoptosis induced by parthenolide, and this susceptibility could be reversed by transfection with an antisense to GADD153. Parthenolide did not alter the expression of Bcl-2 or Bcl-X(L) proteins during apoptosis in hepatoma cells. Oxidative stress may contribute to parthenolide-induced apoptosis and to GADD153 overexpression in a glutathione-sensitive manner. The sensitivity of tumor cells to parthenolide appears to result from the low expression level of the multifunctional detoxification enzyme glutathione S-transferase pi. Finally, parthenolide and its derivatives may be useful chemotherapeutic agents to treat these invasive cancers.

Study of apoptosis in human liver cancers

AIM: To investigate the action of apoptosis in occurrence of liver cacinomas in vivo and the biological effect of Solanum lyratum Thumb on BEL-7404 cell line inducing apoptosis in vitro.

METHODS: The apoptosis in the liver carcinoma was detected with terminal deoxynucl neotidyl transferase mediated dUTP nick end labelling (TUNEL); the cancer cells cultured in DMED medium were treated with extract of Solanum lyratum Thumb and observed under microscope, and their DNA was assayed by gel electrophoresis.

RESULTS: In vivo apoptotic cells in the cancer adjacent tissues inceased; in vitro treatment of liver cancers with extract of Solanum lyratum Thumb could induce the cells to manifest a typical apoptotic morphology. Their DNA was fractured and a characteristic ladder pattern could be found using electrophoresis.

CONCLUSION: In vivo the apoptosis of carcinomas was lower; maybe the cells divided quickly and then the cancers occurred. In the cancer adjacent tissues, the apoptosis pricked up, and in vitro Solanum lyratum Thumb could induce the apoptosis of BEL-7404 cells.