Laparoscopic cholecystectomy only could be an appropriate treatment for selected clinical R0 gallbladder carcinoma

BACKGROUND

Laparoscopic cholecystectomy (LC) for gallbladder carcinoma still is controversial except for the early stages of gallbladder carcinoma (Tis). This study was designed to evaluate and revisit the role of LC in treating gallbladder carcinoma.

METHODS

Available medical records of patients with surgeries for gallbladder carcinoma were retrospectively investigated from August 1992 to February 2005.

RESULTS

Among 219 patients treated for gallbladder carcinoma, 57 (26%) underwent LC. A total of 16 patients (28.1%) underwent subsequent radical cholecystectomy (LC-RC), and 41 (71.9%) were only followed up without radical surgery (LC). Tis was found in 11 patients (19.3%), T1a in 3 patients (5.3%), T1b in 8 patients (14%), T2 in 19 patients (33.3%), and T3 in 16 patients (28.1%). The findings showed R0 in 14 cases of the radical cholecystectomy group, and clinical R0 was noted in 30 cases of the LC-only group. No survival differences were noted between LC and LC-RC (p = 0.2575), especially in the case of T2 lesions (p = 0.6274), nor between the R0 and clinical R0 (p = 0.5839). However, significant survival differences were noted between the R2 and R0 groups, and between R2 and clinical R0, respectively (p < 0.001).

CONCLUSIONS

The findings show that LC could be appropriate treatment for gallbladder carcinoma only in selected cases of clinical R0 lesions.

Ionizing radiation-induced micronucleus formation is mediated by reactive oxygen species that are produced in a manner dependent on mitochondria, Nox1, and JNK

Ionizing radiation (IR) is known to induce genotoxic damage to DNA, chromosomes, and the nucleus. However, the damage that IR causes to the nucleus has received much less attention. Given that reactive oxygen species (ROS) are involved in IR-induced DNA breaks and chromosomal aberrations, this study examined the role of ROS in IR-induced damage to the nucleus. Human Jurkat T cells were irradiated with gamma-rays at a dose of 2.5 Gy, which resulted in a dramatic increase in both the cellular ROS levels and the number of micronuclei. This latter event was attenuated when the IR-induced ROS were eliminated through the exogenous application of an antioxidant enzyme catalase. The ability of IR to induce the accumulation of ROS and micronucleus formation was also reduced either when the cells were irradiated in the presence of rotenone, a mitochondrial respiratory chain inhibitor, or when the cellular Nox1 levels were reduced by RNA interference. These results suggest that IR stimulates both the mitochondria and Nox1 to produce ROS, and that these ROS are involved in the IR-induced formation of micronuclei. IR also activated c-Jun N-terminal kinase (JNK), which was reversed by catalase, rotenone, or Nox1 RNA interference. SP600125, a JNK-specific inhibitor, suppressed the IR-induced accumulation of ROS. This inhibitor consistently attenuated the IR-induced formation of micronuclei. Therefore, ROS and JNK appear to act in a positive mutual manner in IR-induced signaling processes. Overall, IR appears to induce the formation of micronuclei by inducing ROS through mitochondria, Nox1, and JNK.

Metronomic treatment of temozolomide inhibits tumor cell growth through reduction of angiogenesis and augmentation of apoptosis in orthotopic models of gliomas

Glioblastoma is a highly angiogenic tumor with a dismal prognosis. Temozolomide (TMZ), a methylating agent is one of the most effective chemotherapeutic agents against glioblastoma. To overcome the problem that most of these tumors become resistant to chemotherapeutic regimens within a year, we investigated the antitumor efficacy of metronomic administration of low-dose TMZ in in vitro cell proliferation/cytotoxicity assay and in vivo rat and nude mouse orthotopic glioma model. By in vitro assay, we elucidated that C6/LacZ rat glioma cells were more resistant to metronomic treatment of TMZ than U-87MG human glioblastoma cells and bEnd.3 mouse brain endothelial cells. Compared with the conventional chemotherapeutic regimen of TMZ, we found that frequent administration of TMZ at a low dose (metronomic treatment) markedly inhibited angiogenesis as well as tumor growth in a TMZ-resistant C6/LacZ rat glioma model. In addition, metronomic treatment of TMZ significantly augmented apoptosis of tumor cells in this model. For the TMZ-sensitive U-87MG cells, even with a very low dose of TMZ, which is not effective to reduce tumor mass, the metronomic treatment of TMZ reduced the microvessel density, i.e. angiogenesis, in a nude mouse orthotopic model. In conclusion, for both models, the metronomic treatment of TMZ decreased angiogenesis. Especially, in TMZ-resistant glioma cells, this regimen increased apoptosis of tumor cells and decreased tumor growth. The metronomic treatment of TMZ in orthotopic glioma models demonstrated a successful antiangiogenic effect which can overcome the chemoresistance in conventional TMZ chemotherapy.

Synergistic effect and condition of pegylated interferon alpha with paclitaxel on glioblastoma

Glioblastomas are highly vascularized tumors and anti-angiogenic strategy is one of the most promising therapeutic approaches to treat brain tumors. Interferon alpha (IFN-alpha) as a single agent or combined with standard chemo-therapy has been shown to inhibit various tumors, but the effect of combination anti-angiogenic therapy on brain tumors has not been well studied. We determined the optimal dose and schedule of pegylated IFN-alpha (PEG-IFN-alpha) against U-87MG human glioblastoma cells growing orthotopically in nude mice, since several clinical trials reported that PEG-IFN-alpha administered at higher or lower doses was less effective. The group treated two times per week with injections of 10 KU of PEG-IFN-alpha for 4 weeks showed significant decreases in cell proliferation and angiogenesis. Moreover, the optimal dose and schedule of PEG-IFN-alpha determined in this study and combined with paclitaxel treatment potently inhibited tumor growth in vivo. The mechanisms of the significant therapeutic effects were most likely caused by directly inhibiting cell proliferation and angiogenesis, and rendering apoptosis increased. Specifically PEG-IFN-alpha/paclitaxel combination induced apoptosis of tumor-associated endothelial cells more than that of tumor cells. These results suggest that optimal biological dosage and scheduling of PEG-IFN-alpha and paclitaxel combination is a potent strategy for glioblastoma patients as a new synergistic anti-endothelial treatment.

Overexpression of hepatitis C virus NS5A protein induces chromosome instability via mitotic cell cycle dysregulation

Hepatocellular carcinoma (HCC) is a common primary cancer associated with high incidences of genetic variations including chromosome instability. Moreover, it has been demonstrated that hepatitis C virus (HCV) is one of the major causes of HCC. However, no previous work has assessed whether HCV proteins are associated with the induction of chromosome instability. Here, we found that liver cell lines constitutively expressing full-length or truncated versions of the HCV genome show a high incidence of chromosome instability. In particular, the overexpression of HCV NS5A protein in cultured liver cells was found to promote chromosome instability and aneuploidy. Further experiments showed that NS5A-induced chromosome instability is associated with aberrant mitotic regulations, such as, an unscheduled delay in mitotic exit and other mitotic impairments (e.g. multi-polar spindles). Thus, our results indicate that HCV NS5A protein may be directly involved in the induction of chromosome instability via mitotic cell cycle dysregulation, and provide novel insights into the molecular mechanisms of HCV-associated hepatocarcinogenesis.

Activation of Bak and Bax through c-abl-protein kinase Cdelta-p38 MAPK signaling in response to ionizing radiation in human non-small cell lung cancer cells

Intracellular signaling molecules and apoptotic factors seem to play an important role in determining the radiation response of tumor cells. However, the basis for the link between signaling pathway and apoptotic cell death machinery after ionizing irradiation remains still largely unclear. In this study, we showed that c-Abl-PKCdelta-Rac1-p38 MAPK signaling is required for the conformational changes of Bak and Bax during ionizing radiation-induced apoptotic cell death in human non-small cell lung cancer cells. Ionizing radiation induced conformational changes and subsequent oligomerizations of Bak and Bax, dissipation of mitochondrial membrane potential, and cytochrome c release from mitochondria. Small interference (siRNA) targeting of Bak and Bax effectively protected cells from radiation-induced mitochondrial membrane potential loss and apoptotic cell death. p38 MAPK was found to be selectively activated in response to radiation treatment. Inhibition of p38 MAPK completely suppressed radiation-induced Bak and Bax activations, dissipation of mitochondrial membrane potential, and cell death. Moreover, expression of a dominant negative form of protein kinase Cdelta (PKCdelta) or siRNA targeting of PKCdelta attenuated p38 MAPK activation and conformational changes of Bak and Bax. In addition, ectopic expression of RacN17, a dominant negative form of Rac1, markedly inhibited p38 MAPK activation but did not affect PKCdelta activation. Upon stimulation of cells with radiation, PKCdelta was phosphorylated dramatically on tyrosine. c-Abl-PKCdelta complex formation was also increased in response to radiation. Moreover, siRNA targeting of c-Abl attenuated radiation-induced PKCdelta and p38 MAPK activations, and Bak and Bax modulations. These data support a notion that activation of the c-Abl-PKCdelta-Rac1-p38 MAPK pathway in response to ionizing radiation signals conformational changes of Bak and Bax, resulting in mitochondrial activation-mediated apoptotic cell death in human non-small cell lung cancer cells.

WITHDRAWN: The Impact of Gender and Age Matching for Long-Term Graft Survival in Living Donor Renal Transplantation

In renal transplantation, donor age and allograft size are known to have an important influence on the outcome of the graft reflecting functional renal mass. Women tend to have smaller kidneys with 17% fewer nephrons than male kidneys. The number of glomeruli per kidney as well as the mean glomerular volume closely correlate with kidney weight and negatively correlate with subject age. We evaluated the impact of gender and age matching in living-donor renal transplantation on long-term graft survival.

MATERIALS AND METHODS

Four groups were discerned among 614 renal transplants, according to donor and recipient gender: Group 1 was male donor to male recipient; Group 2 was male donor to female recipient; Group 3 was female donor to male recipient; and Group 4 was female donor to female recipient. We analyzed long-term graft survival and risk factors between the four groups as well as according to age matching. Statistical significance was determined by the Kaplan-Meier method and log rank test (P < .05).

RESULT

The graft survival rates at 1, 3, 5, and 10 years were 92.62%, 88.13%, 82.37%, and 76.07%, respectively. The risk factors affecting long-term graft survival were donor age, donor gender, acute rejection rate, and HLA-DR matching. Among the four groups, the graft survival rates of Group 3 (female donor to male recipient) were significantly different from the other groups (P = .0165). Also, the long-term graft survival rates according to age differences were significantly different between older donors than recipients and younger donors than recipients in each group (P = .0213).

CONCLUSION

The importance of inadequate renal mass is magnified in high-risk recipients. Age matching could perhaps improve the results of transplantation, particularly when kidneys from older donors are used. Consideration of age and gender as criteria for the choice of donors and recipients may be considered in organ allocation.

Long-Term Graft Outcome of Living Donor Renal Transplantation: Single Center Experience

The number of potential renal transplant recipients far exceeds the number of cadaveric donors. For this reason, living-related donors (LRD) and living-unrelated donors (LURD) have been used to decrease the cadaveric donor shortage. We analyzed 571 living donor transplants for 25 years in our center.

MATERIALS AND METHODS

From 1978 to 2003, 571 patients underwent LRD (n = 253), or LURD (n = 318) kidney transplantation. The patients were divided into precyclosporine era (from 1978 to 1987, n = 44; era I), cyclosporine era (from 1988 to 1997, n = 367, era II), and cyclosporine plus mycophenolate-mofetil era (from 1998 to 2003, n = 160, era III). We compared the graft survival rate of the recipients according to the immunosuppressants, analyzing the variables of donor and recipient age, sex, HLA matching, and acute rejection rate. We also compared long-term survival rates between LRD and LURD.

RESULTS

The 1- and 10-year graft survival rates of all patients were 93.4% and 77.4%, respectively. The 1- and 10- year graft survival rates were 75.0% and 36.3% in era I; and 94.8 % and 80.2% in era II. The 1- and 5-year graft survival rates were 96.6% and 93.3% in era III (P < .001). The occurrence rate of an acute rejection episode was 11.4% (era I), 21.8% (era II), and 14.4% (era III) (P = .056). The 1- and 5-year graft survival rates were 92.3% and 81.7% among LRD transplants, and 94.2% and 86.9% among LURD transplants, respectively (P = .122).

DISCUSSION

The graft survival rates of living-donor transplants are improving due to advances in patient care and new immunosuppressive agents.

Analysis of Allograft Biopsy Specimens in Renal Transplants With Proteinuria: Is Proteinuria a Culprit of Graft Loss?

It has been proposed that proteinuria occurring after renal transplantation may be not only a marker but also a culprit of allograft dysfunction. We retrospectively analyzed the data from 55 patients who underwent transplant renal biopsy for proteinuria and/or azotemia occurring beyond 1 year after transplantation. Proteinuria was considered as significant when > or = 30 mg/dL, and the results of transplant biopsy were categorized according to the Banff 97 classification. Logistic regression was used to estimate odds ratios (OR) for graft loss associated with proteinuria and transplant pathology. The patients were followed for 86.0 +/- 32.8 months after transplantation, and transplant biopsy was performed at 54.1 +/- 31.0 months. Proteinuria at 1 year after transplantation noted in 29.1% of patients was not significantly associated with graft loss (OR = 1.94, 95% CI from 0.59 to 6.41). In addition, proteinuria at the time of transplant biopsy was not significantly associated with graft loss. Chronic allograft nephropathy was the most frequent transplant pathology. Only glomerulonephritis was significantly associated with proteinuria at the time of the transplant biopsy. On the other hand, graft loss was significantly associated with the presence of proteinuria both at 1 year after transplant biopsy and at the final follow-up. These results suggest that posttransplantation proteinuria is an important marker of graft dysfunction, but is not predictive of graft loss in biopsy-proven cases. Appropriate management guided by the results of a transplant biopsy may improve the outcome.

Phytosphingosine in combination with ionizing radiation enhances apoptotic cell death in radiation-resistant cancer cells through ROS-dependent and -independent AIF release

The use of chemical modifiers as radiosensitizers in combination with low-dose irradiation may increase the therapeutic effect on cancer by overcoming a high apoptotic threshold. Here, we showed that phytosphingosine treatment in combination with γ-radiation enhanced apoptotic cell death of radiation-resistant human T-cell lymphoma in a caspase-independent manner. Combination treatment induced an increase in intracellular reactive oxygen species (ROS) level, mitochondrial relocalization of B-cell lymphoma-2(Bcl-2)-associated X protein (Bax), poly-adenosine diphosphate (ADP)-ribose polymerase 1 (PARP-1) activation, and nuclear translocation of apoptosis-inducing factor (AIF). siRNA targeting of AIF effectively protected cells from the combination treatment-induced cell death. An antioxidant, N-acetyl-L-cysteine (NAC), inhibited Bax relocalization and AIF translocation but not PARP-1 activation. Moreover, transfection of Bax-siRNA significantly inhibited AIF translocation. Pretreatment of PARP-1 inhibitor, DPQ (3,4-dihydro-5-[4-(1-piperidinyl)-butoxy]-1(2H)-isoquinolinone), or PARP-1-siRNA also partially attenuated AIF translocation, whereas the same treatment did not affect intracellular ROS level and Bax redistribution. Taken together, these results demonstrate that enhancement of cell death of radiation-resistant cancer cells by phytosphingosine treatment in combination with γ-radiation is mediated by nuclear translocation of AIF, which is in turn mediated both by ROS-dependent Bax relocalization and ROS-independent PARP-1 activation. The molecular signaling pathways that we elucidated in this study may provide potential drug targets for radiation sensitization of cancers refractive to radiation therapy. (Blood. 2005;105:1724-1733)

Caspase-independent cell death by arsenic trioxide in human cervical cancer cells: reactive oxygen species-mediated poly(ADP-ribose) polymerase-1 activation signals apoptosis-inducing factor release from mitochondria

Although mechanisms of arsenic trioxide (As(2)O(3))-induced cell death have been studied extensively in hematologic cancers, those in solid cancers have yet to be clearly defined. In this study, we showed that the translocation of apoptosis-inducing factor (AIF) from mitochondria to the nucleus is required for As(2)O(3)-induced cell death in human cervical cancer cells. We also showed that reactive oxygen species (ROS)-mediated poly(ADP-ribose) polymerase-1 (PARP-1) activation is necessary for AIF release from mitochondria. The treatment of human cervical cancer cells with As(2)O(3) induces dissipation of mitochondrial membrane potential (Deltapsi(m)), translocation of AIF from mitochondria to the nucleus, and subsequent cell death. Small interfering RNA targeting of AIF effectively protects cervical cancer cells against As(2)O(3)-induced cell death. As(2)O(3) also induces an increase of intracellular ROS level and a marked activation of PARP-1. N-acetyl-l-cystein, a thiol-containing antioxidant, completely blocks As(2)O(3)-induced PARP-1 activation, Deltapsi(m) loss, nuclear translocation of AIF from mitochondria, and the consequent cell death. Furthermore, pretreatment of 1,5-dihydroxyisoquinoline or 3,4-dihydro-5-[4-(1-piperidinyl)butoxy]-1(2H)-isoquinolinone, PARP-1 inhibitors, effectively attenuates the loss of Deltapsi(m), AIF release, and cell death. These data support a notion that ROS-mediated PARP-1 activation signals AIF release from mitochondria, resulting in activation of a caspase-independent pathway of cell death in solid tumor cells by As(2)O(3) treatment.

Opposite effects of Ha-Ras and Ki-Ras on radiation-induced apoptosis via differential activation of PI3K/Akt and Rac/p38 mitogen-activated protein kinase signaling pathways

It has been well known that Ras signaling is involved in various cellular processes, including proliferation, differentiation, and apoptosis. However, distinct cellular functions of Ras isozymes are not fully understood. Here we show the opposing roles of Ha-Ras and Ki-Ras genes in the modulation of cell sensitivity to ionizing radiation. Overexpression of active isoform of Ha-Ras (12V-Ha-Ras) in Rat2 cells increases resistance to the ionizing radiation. Constitutive activation of phosphoinositide-3-kinase (PI3K) and Akt is detected specifically in 12V-Ha-Ras-overexpressing cells. The specific PI3K inhibitor LY294002 inhibits PI3K/Akt signaling and potentiates the radiation-induced apoptosis, suggesting that activation of the PI3K/Akt signaling pathway is involved in the increased radio-resistance in cells overexpressing 12V-Ha-Ras. Overexpression of activated Ki-Ras (12V-Ki-Ras), on the other hand, markedly increases radiation sensitivity. The p38 mitogen-activated protein kinase (MAPK) activity is selectively enhanced by ionizing radiation in cells overexpressing 12V-Ki-Ras. The specific p38 MAPK inhibitor, PD169316, or dominant-negative p38 MAPK decreases radiation-induced cell death. We further show that the mechanism that underlies potentiation of cell death in cells overexpressing 12V-Ki-Ras involves Bax translocation to the mitochondrial membrane. Elevated Bax translocation following ionizing irradiation in 12V-Ki-Ras-overexpressing cells is completely inhibited by PD169316 or dominant-negative p38 MAPK. In addition, introduction of cells with RacN17, a dominant-negative mutant of Rac, resulted in a marked inhibition of radiation-induced Bax translocation and apoptotic cell death as well as p38 MAPK activation. Taken together, these findings explain the opposite effects of Ha-Ras and Ki-Ras on modulation of radiosensitivity, and suggest that differential activation of PI3K/Akt and Rac/p38 MAPK signaling by Ha-Ras and Ki-Ras may account for the opposing response to the ionizing radiation. These data provide an explanation for the diverse biological functions of Ras isozymes, and partly accounts for the differential response of transformed cells to anticancer treatments.

Suppression of Extracellular Signal-related Kinase and Activation of p38 MAPK Are Two Critical Events Leading to Caspase-8- and Mitochondria-mediated Cell Death in Phytosphingosine-treated Human Cancer Cells

We previously demonstrated that the phytosphingosine-induced apoptosis was accompanied by the concomitant induction of both the caspase-8-mediated and mitochondrial activation-mediated apoptosis pathways. In the present study, we investigated the role of mitogen-activated protein kinases (MAPKs) in the activation of these two distinct cell death pathways induced by phytosphingosine in human cancer cells. Phytosphingosine caused strong induction of caspase-8 activity and caspase-independent Bax translocation to the mitochondria. A rapid decrease of phosphorylated ERK1/2 and a marked increase of p38 MAPK phosphorylation were observed within 10 min after phytosphingosine treatment. Activation of ERK1/2 by pretreatment with phorbol 12-myristate 13-acetate or forced expression of ERK1/2 attenuated phytosphingosine-induced caspase-8 activation. However, Bax translocation and caspase-9 activation was unaffected, indicating that down-regulation of the ERK activity is specifically required for the phytosphingosine-induced caspase-8-dependent cell death pathway. On the other hand, treatment with SB203580, a p38 MAPK-specific inhibitor, or expression of a dominant negative form of p38 MAPK suppressed phytosphingosine-induced translocation of the proapoptotic protein, Bax, from the cytosol to mitochondria, cytochrome c release, and subsequent caspase-9 activation but did not affect caspase-8 activation, indicating that activation of p38 MAPK is involved in the mitochondrial activation-mediated cell death pathway. Our results suggest that phytosphingosine can utilize two different MAPK signaling pathways for amplifying the apoptosis cascade, enhancing the understanding of the molecular mechanisms utilized by naturally occurring metabolites to regulate cell death. Molecular dissection of the signaling pathways that activate the apoptotic cell death machinery is critical for both our understanding of cell death events and development of cancer therapeutic agents.

Alteration of gene expression during radiation-induced resistance and tumorigenesis in NIH3T3 cells revealed by cDNA microarrays: involvement of MDM2 and CDC25B

To identify a set of genes involved in the development of radiation-induced tumorigenesis, we used DNA microarrays consisting of 1176 mouse genes and compared expression profiles of radioresistant cells, designated NIH3T3-R1 and NIH3T3-R4. These cells were tumorigenic in a nude mouse grafting system, as compared with the parental NIH3T3 cells. Expression of MDM2, CDK6 and CDC25B was found to increase more than 3-fold. Entactin protein levels were down-regulated in NIH3T3-R1 and NIH3T3-R4 cells. Changes in gene expression were confirmed by reverse transcription-PCR or western blotting. When these genes were transfected into NIH3T3 cells, CDC25B and MDM2 overexpressing NIH3T3 cells showed radioresistance, while CDK6 overexpressing cells did not. In the case of entactin, overexpressing NIH3T3-R1 and NIH3T3-R4 cells were still radioresistant. Furthermore, CDC25B and MDM2 overexpressing cells grafted into nude mice were tumorigenic. NIH3T3-R1 and NIH3T3-R4 cells showed increased radiation-induced apoptosis accompanied by a faster growth rate, rather than an earlier radiation-induced G2/M phase arrest, suggesting that the radioresistance of NIH3T3-R1 and NIH3T3-R4 cells was due to a faster growth rate rather than induction of apoptosis. In the case of MDM2 and CDC25B overexpressing cells, similar phenomena, such as increased apoptosis and a faster growth rate, were shown. The above results, therefore, demonstrate involvement of CDC25B and MDM2 overexpression in radiation-induced tumorigenesis and provide novel targets for detection of radiation-induced carcinogenesis.

Possible biomarkers for ionizing radiation exposure in human peripheral blood lymphocytes

Biomarkers to indicate past exposure to radiation have not been entirely satisfactory. Using cDNA microarray hybridization to find new potential biomarkers, we identified highly expressed genes in human peripheral blood lymphocytes (PBLs) after irradiation 1 Gy ex vivo. The present set of radiation markers in PBLs was identified 12 h after radiation. A total of 44 genes were identified. However, when RT-PCR was performed with mRNA from the PBLs of five individuals, only four genes, including TRAIL receptor 2, DRAL (now known as FHL2), cyclin G, and cyclin protein gene, showed greater than 50% agreement between gene induction as detected by microarray analysis and by RT-PCR. When more than 32 donors were tested for the above four genes, greater than 85% agreement was obtained between gene induction measured by microarray analysis and by RT-PCR. There was a linear dose-response relationship between 0.5 and 4 Gy 12 h after irradiation; however, there was less linearity at later times. These results suggested that the relative expression levels of genes such as TRAIL receptor 2, FHL2, cyclin G, and cyclin protein gene in PBLs may provide estimates of radiation exposures.

Phytosphingosine induces apoptotic cell death via caspase 8 activation and Bax translocation in human cancer cells

PURPOSE

Sphingolipid metabolites, such as sphingosine and ceramide, are highly bioactive compounds and are involved in diverse cell processes, including cell-cell interaction, cell proliferation, differentiation, and apoptosis. However, the physiological roles of phytosphingosine are poorly understood. In this study, we report that phytosphingosine can potently induce apoptotic cell death in human cancer cells via caspase activation and caspase-independent cytochrome c release.

EXPERIMENTAL DESIGN

Phytosphingosine-induced apoptosis was determined by Hoechst 33258 staining, flow cytometric analysis, and DNA fragmentation assay. Involvement of caspases was determined by immunoblot analysis and cell death detection assays after treatment with synthetic inhibitor z-Val-Ala-Asp-fluoromethyl ketone, z-DEVD-fmk, or z-IETD-fmk. Death receptor (DR) dependency was analyzed by examining expression of DRs (Fas, DR4, DR5, TNFR1, and R2), and interaction of Fas-associated death domain and caspase 8. Involvement of the mitochondria pathway was examined by monitoring of the mitochondria membrane potential, cytochrome c release, and Bax translocation.

RESULTS

Phytosphingosine-treated cells displayed several features of apoptosis, including increase of sub-G(1) population, DNA fragmentation, and poly(ADP-ribose) polymerase cleavage. We observed that phytosphingosine cause activation of caspase 8 in a DR-independent fashion. Phytosphingosine also induced activation of caspase 9 and 3, loss of mitochondrial membrane potential, and the cytochrome c release from mitochondria. However, we failed to detect Bid cleavage. Moreover, caspase 8 inhibitor z-IETD-fmk did not affect phytosphingosine-induced cytochrome c release and caspase 9 activation, suggesting that phytosphingosine-induced cytochrome c release is caused by caspase 8-independent manner. Phytosphingosine induced mitochondrial translocation of Bax from the cytosol without changes in the protein levels of Bcl-2, Bcl-xL, and Bax. In addition, Bcl-2/Bax interaction was diminished after addition of phytosphingosine.

CONCLUSION

These findings indicate that phytosphingosine induces apoptotic cell death in human cancer cells by direct activation of caspase 8, and by mitochondrial translocation of Bax and subsequent release of cytochrome c into cytoplasm, providing a potential mechanism for the anticancer activity of phytosphingosine.

Hspa4 (HSP70) is involved in the radioadaptive response: results from mouse splenocytes

In a continuation of our earlier study on the involvement of HSP25 (now known as Hspb1) and HSP70 (now known as Hspa4) in the induction of an adaptive response, we examined the involvement of these proteins in the induction of the adaptive response using an animal model system. C57BL6 mice were irradiated with 5 cGy of gamma radiation three times in 1 week (for a total of 15 cGy), and a high challenge dose (6 Gy) was given on the day after the last low-dose irradiation. The survival time of the low-dose preirradiated mice was increased to 30%. The induction of apoptosis induced by 6 Gy was also reduced by this low-dose preirradiation regimen. To elucidate any link existing between the HSPs and the induction of the adaptive response, reverse transcriptase (RT)-polymerase chain reaction (PCR) analysis was performed using splenocytes. High-dose radiation up-regulated the expression of Hspb1 and especially Hspa4, while expression of other HSPs such as HSC70 (now know as Hspa8), Hsp90, and alphaB-crystalline (now known as Cryab) did not change. When splenocytes from Hspa4 transgenic mice were preirradiated with a low dose of radiation, a reduction in cell death after high-dose irradiation was observed. These results suggest that Hspa4 is a key molecule in the induction of the adaptive response.

Induction of cell cycle arrest and apoptosis in human breast cancer cells by quercetin

Quercetin, a widely distributed bioflavonoid, has been shown to induce growth inhibition in certain cancer cell types. In the present study we have pursued the mechanism of growth inhibition in MCF-7 human breast cancer cells. Quercetin treatment resulted in the accumulation of cells specifically at G2/M phase of the cell cycle. Mitotic index measured by MPM2 staining clearly showed that cells were transiently accumulated in M phase, 24 h after treatment. The transient M phase accumulation was accompanied by a transient increase in the levels of cyclin B1 and Cdc2 kinase activity. However, 24 h or longer treatment caused a marked accumulation of cells in G2 instead of M phase. Levels of cyclin B1 and cyclin B1-associated Cdc2 kinase activity were also decreased. We also found that quercetin markedly increased Cdk-inhibitor p21CIP1/WAF1 protein level after treatment for 48 h or longer, and the induction of p21CIP1/WAF1 increased its association with Cdc2-cyclin B1 complex, however, up-regulation of p53 by quercetin was not observed. Quercetin also induced significant apoptosis in MCF-7 cells in addition to cell cycle arrest, and the induction of apoptosis was markedly blocked by antisense p21CIP1/WAF1 expression. The present data, therefore, demonstrate that a flavonoid quercetin induces growth inhibition in the human breast carcinoma cell line MCF-7 through at least two different mechanisms; by inhibiting cell cycle progression through transient M phase accumulation and subsequent G2 arrest, and by inducing apoptosis.

Ionizing radiation can overcome resistance to TRAIL in TRAIL-resistant cancer cells

Although the majority of cancer cells are killed by TRAIL (tumor necrosis factor-related apoptosis-inducing ligand treatment), certain types show resistance to it. Ionizing radiation also induces cell death in cancer cells and may share common intracellular pathways with TRAIL leading to apoptosis. In the present study, we examined whether ionizing radiation could overcome TRAIL resistance in the variant Jurkat clones. We first selected TRAIL-resistant or -sensitive Jurkat clones and examined cross-responsiveness of the clones between TRAIL and radiation. Treatment with gamma-radiation induced significant apoptosis in all the clones, indicating that there seemed to be no cross-resistance between TRAIL and radiation. Combined treatment of radiation with TRAIL synergistically enhanced killing of TRAIL-resistant cells, compared to TRAIL or radiation alone. Apoptosis induced by combined treatment of TRAIL and radiation in TRAIL-resistant cells was associated with cleavage of caspase-8 and the proapoptotic Bid protein, resulting in the activation of caspase-9 and caspase-3. No changes in the expressions of TRAIL receptors (DR4 and DR5) and Bcl-2 or Bax were found after treatment. The caspase inhibitor z-VAD-fmk completely counteracted the synergistic cell killing induced by combined treatment of TRAIL and gamma-radiation. These results demonstrated that ionizing radiation in combination with TRAIL could overcome resistance to TRAIL in TRAIL-resistant cells through TRAIL receptor-independent synergistic activation of the cascades of the caspase-8 pathway, suggesting a potential clinical application of combination treatment of TRAIL and ionizing radiation to TRAIL-resistant cancer cells.

Thymidine-dependent attenuation of the mitochondrial apoptotic pathway in adenosine-induced apoptosis of HL-60 cells

OBJECTIVE

We previously reported that adenosine-induced apoptosis in HL-60 cells was attenuated by cotreating the cells with pyrimidine nucleosides. The mechanism involved in this adenosine-induced apoptosis by the differential supply of nucleosides is studied here with a particular focus on the regulation of apoptosis-associated mitochondrial events.

METHODS

Time-dependent changes in the mitochondrial membrane potential (MMP) after treatment with adenosine and/or thymidine were monitored.

RESULTS

The cells did not show any decrease of MMP level up to 2.5 h after 1 mM adenosine exposure, whereas cytochrome c release, caspase-9 and caspase-3 activity, and DNA fragmentation were already activated, suggesting that mitochondrial depolarization is not a prerequisite of other apoptosis-related mitochondrial events. In contrast, the translocation of Bax to mitochondria and the release of cytochrome c began within the first hour of adenosine treatment.

CONCLUSION

Thus, it is believed that adenosine-induced apoptosis is mediated by the activation of the caspase cascade by cytochrome c release with concomitant increase of Bax in the mitochondria, which implies that the translocation of Bax might be a leading event in the adenosine-induced apoptosis. Moreover, we found that most of the apoptotic parameters in adenosine-induced cellular changes, such as translocation of Bax, the release of cytochrome c, and the consequent activation of caspase-9 and caspase-3, were attenuated by thymidine supplement, thus indicating that the sensing of a nucleoside or nucleotide balance might be an upstream event of cytochrome c release. Therefore, it can be concluded that thymidine can attenuate adenosine-induced apoptosis by modulating the earliest stage of the mitochondrial apoptotic pathway.

New family of regulators in the environmental signaling pathway which activates the general stress transcription factor sigma(B) of Bacillus subtilis

Expression of the general stress regulon of Bacillus subtilis is controlled by the alternative transcription factor sigma(B), which is activated when cells encounter growth-limiting energy or environmental stresses. The RsbT serine-threonine kinase is required to convey environmental stress signals to sigma(B), and this kinase activity is magnified in vitro by the RsbR protein, a positive regulator important for full in vivo response to salt or heat stress. Previous genetic analysis suggested that RsbR function is redundant with other unidentified regulators. A search of the translated B. subtilis genome found six paralogous proteins with significant similarity to RsbR: YetI, YezB, YkoB, YojH, YqhA, and YtvA. Their possible regulatory roles were investigated using three different approaches. First, genetic analysis found that null mutations in four of the six paralogous genes have marked effects on the sigma(B) environmental signaling pathway, either singly or in combination. The two exceptions were yetI and yezB, adjacent genes which appear to encode a split paralog. Second, biochemical analysis found that YkoB, YojH, and YqhA are specifically phosphorylated in vitro by the RsbT environmental signaling kinase, as had been previously shown for RsbR, which is phosphorylated on two threonine residues in its C-terminal region. Both residues are conserved in the three phosphorylated paralogs but are absent in the ones that were not substrates of RsbT: YetI and YezB, each of which bears only one of the conserved residues; and YtvA, which lacks both residues and instead possesses an N-terminal PAS domain. Third, analysis in the yeast two-hybrid system suggested that all six paralogs interact with each other and with the RsbR and RsbS environmental regulators. Our data indicate that (i) RsbR, YkoB, YojH, YqhA, and YtvA function in the environmental stress signaling pathway; (ii) YtvA acts as a positive regulator; and (iii) RsbR, YkoB, YojH, and YqhA collectively act as potent negative regulators whose loss increases sigma(B) activity more than 400-fold in unstressed cells.