Haploinsufficiency in DNA polymerase beta increases cancer risk with age and alters mortality rate

This study uses a base excision repair (BER)-deficient model, the DNA polymerase beta heterozygous mouse, to investigate the effect of BER deficiency on tumorigenicity and aging. Aged beta-pol(+/-) mice express 50% less beta-pol transcripts and protein (P < 0.05) than aged beta-pol(+/+) mice, showing maintenance of the heterozygous state over the life span of the mouse. This reduction in beta-pol expression was not associated with an increase in mutation rate but was associated with a 100% increase in the onset of hypoploidy. Aged beta-pol(+/-) mice exhibited a 6.7-fold increase in developing lymphoma (P < 0.01). Accordingly, 38% of beta-pol(+/-) mice exhibited lymphoid hyperplasia, whereas none of the beta-pol(+/+) exhibited this phenotype. beta-pol(+/-) mice were also more likely to develop adenocarcinoma (2.7-fold increase; P < 0.05) and more likely to develop multiple tumors, as 20% of the beta-pol(+/-) animals died bearing multiple tumors compared with only 5% of the beta-pol(+/+) animals (P < 0.05). In spite of accelerated tumor development, no gross effect of beta-pol heterozygosity was seen with respect to life span. However, the survival curves for the beta-pol(+/+) and beta-pol(+/-) mice are not identical. A maximum likelihood estimation analysis showed a modest but significant (P < 0.05) acceleration of the age-dependent mortality rate in beta-pol(+/-) mice. Thus, the beta-pol(+/-) mouse represents a model in which mortality rate and tumor development are accelerated and provides evidence supporting the role of genomic maintenance in both aging and carcinogenesis.

Inhibition of NF-kappa B activation through targeting I kappa B kinase by celastrol, a quinone methide triterpenoid

Celastrol, a quinone methide triterpenoid, was isolated as an inhibitor of NF-kappaB from Celastrus orbiculatus. This compound dose-dependently inhibited a variety of stimuli-induced NF-kappa B-regulated gene expression and the DNA-binding of NF-kappa B in different cell lines without affecting DNA-binding activity of AP-1. Preincubation of celastrol completely blocked the LPS-, TNF-alpha-, or PMA-induced degradation and phosphorylation of I kappa B alpha. Importantly, celastrol inhibited IKK activity and the constitutively active IKK beta activity in a dose-dependent manner without either affecting the NF-kappa B activation induced by RelA over-expression or directly suppressing the DNA-binding of activated NF-kappa B. However, mutation of cysteine 179 in the activation loop of IKK beta abolished sensitivity towards to celastrol, suggesting that celastrol suppressed the NF-kappa B activation by targeting cysteine 179 in the IKK. To verify that celastrol is a NF-kappa B inhibitor, we investigated its effect on some NF-kappa B target genes expressions. Celastrol prevented not only LPS-induced mRNA expression of iNOS and TNF-alpha, but also TNF-alpha-induced Bfl-1/A1 expression, a prosurvival Bcl-2 homologue. Consistent with these results, celastrol significantly suppressed the production of NO and TNF-alpha in LPS-stimulated RAW264.7 cells, and increased the cytotoxicity of TNF-alpha in HT-1080 cells. We also demonstrated that celastrol showed anti-inflammatory and anti-tumor activities in animal models. Taken together, this study extends our understanding on the molecular mechanisms underlying the anti-inflammatory and anti-cancer activities of celastrol and celastrol-containing medicinal plant, which would be a valuable candidate for the intervention of NF-kappa B-dependent pathological conditions.

[Suicidal cancer vaccine enhances anti-tumor immunotherapeutic effect and its safety in the treatment of ovarian cancer]

OBJECTIVE

To study the anti-tumor immunotherapeutic effect induced by the suicidalcancer vaccine FC/TK, and to evaluate the safety of this vaccine.

METHODS

The suicidal cancer vaccine, named FC/TK, was prepared by fusion of suicide gene (HSVI,-TK gene) -modified ovarian carcinoma NuTu-19 cells with rat bone marrow-derived dendritic cells (DCs). The morphology of FC/TK was evaluated by scanning electron microscopy. The stimulatory effect of FC/TK on T cells was determined by T cell proliferation assay. In immunotherapeutic studies in vivo, Fischer344 rats were injected subcutaneously with NuTu-19 cells, followed by treatment of FC/TK on days 7 and 14, compared to controls treated with irradiated FC/TK, FC or PBS, respectively. Tumor incidence and volume were measured in 90 days after challenge. To determine the killing effect of FC/TK in vivo, TUNEL assays were applied to detect apoptotic cell death in spleen of vaccinated rats with prodrug ganciclovir administration.

RESULTS

FC/TK cells were of irregular shape with surface membrane processes. Compared to the control groups, FC/TK significantly promoted T cell proliferation (P <0.01). The rats vaccinated with FC/TK and FC significantly inhibited the tumor growth compared to rats vaccinated with irradiated FC/TK (P <0.05) or with PBS ( P <0.01). The immunotherapeutic effect induced by FC/TK was similar to that using FC. Fluorescence microscopy showed that fluorescein-stained FC/TK cells migrated into spleen also showed to be TUNEL-positive, suggesting that the FC/TK cells were killed by ganciclovir in vivo.

CONCLUSION

Our data indicate that suicidal cancer vaccine is an effective and safe therapy for ovarian carcinoma and may serve as a broadly applicable approach for other cancer vaccines in the future.

Loss of cell polarity drives tumor growth and invasion through JNK activation in Drosophila

Apparent defects in cell polarity are often seen in human cancer. However, the underlying mechanisms of how cell polarity disruption contributes to tumor progression are unknown. Here, using a Drosophila genetic model for Ras-induced tumor progression, we show a molecular link between loss of cell polarity and tumor malignancy. Mutation of different apicobasal polarity genes activates c-Jun N-terminal kinase (JNK) signaling and downregulates the E-cadherin/beta-catenin adhesion complex, both of which are necessary and sufficient to cause oncogenic Ras(V12)-induced benign tumors in the developing eye to exhibit metastatic behavior. Furthermore, activated JNK and Ras signaling cooperate in promoting tumor growth cell autonomously, as JNK signaling switches its proapoptotic role to a progrowth effect in the presence of oncogenic Ras. Our finding that such context-dependent alterations promote both tumor growth and metastatic behavior suggests that metastasis-promoting mutations may be selected for based primarily on their growth-promoting capabilities. Similar oncogenic cooperation mediated through these evolutionarily conserved signaling pathways could contribute to human cancer progression.

Black rice anthocyanins inhibit cancer cells invasion via repressions of MMPs and u-PA expression

Tumor metastasis is the most important cause of cancer death and various treatment strategies have targeted on preventing the occurrence of metastasis. Anthocyanins are natural colorants belonging to the flavonoid family, and are wildly used for their antioxidant properties. Here, we provided molecular evidence associated with the anti-metastatic effects of peonidin 3-glucoside and cyanidin 3-glucoside, major anthocyanins extracted from black rice (Oryza sativa L. indica), by showing a marked inhibition on the invasion and motility of SKHep-1 cells. This effect was associated with a reduced expression of matrix metalloproteinase (MMP)-9 and urokinase-type plasminogen activator (u-PA). Peonidin 3-glucoside and cyanidin 3-glucoside also exerted an inhibitory effect on the DNA binding activity and the nuclear translocation of AP-1. Furthermore, these compounds also exerted an inhibitory effect of cell invasion on various cancer cells (SCC-4, Huh-7, and HeLa). Finally, anthocyanins from O. sativa L. indica (OAs) were evidenced by its inhibition on the growth of SKHep-1 cells in vivo.

5'-AMP-activated protein kinase (AMPK) is induced by low-oxygen and glucose deprivation conditions found in solid-tumor microenvironments

Low oxygen gradients (hypoxia and anoxia) are important determinants of pathological conditions under which the tissue blood supply is deficient or defective, such as in solid tumors. We have been investigating the relationship between the activation of hypoxia-inducible factor 1 (HIF-1), the primary transcriptional regulator of the mammalian response to hypoxia, and 5'-AMP-activated protein kinase (AMPK), another regulatory system important for controlling cellular energy metabolism. In the present study, we used mouse embryo fibroblasts nullizygous for HIF-1alpha or AMPK expression to show that AMPK is rapidly activated in vitro by both physiological and pathophysiological low-oxygen conditions, independently of HIF-1 activity. These findings imply that HIF-1 and AMPK are components of a concerted cellular response to maintain energy homeostasis in low-oxygen or ischemic-tissue microenvironments. Finally, we used transformed derivatives of wild-type and HIF-1alpha- or AMPKalpha-null mouse embryo fibroblasts to determine whether AMPK is activated in vivo. We obtained evidence that AMPK is activated in authentic hypoxic tumor microenvironments and that this activity overlaps with regions of hypoxia detected by a chemical probe. We also showed that AMPK is important for the growth of this tumor model.

Interference with the complement system by tumor cell membrane type-1 matrix metalloproteinase plays a significant role in promoting metastasis in mice

Neoplasms have developed strategies to protect themselves against the complement-mediated host immunity. Invasion- and metastasis-promoting membrane type-1 (MT1) matrix metalloproteinase (MMP) is strongly associated with many metastatic cancer types. The relative importance of the individual functions of MT1-MMP in metastasis was, however, unknown. We have now determined that the expression of murine MT1-MMP in murine melanoma B16F1 cells strongly increased the number of metastatic loci in the lungs of syngeneic C57BL/6 mice. In contrast, MT1-MMP did not affect the number of metastatic loci in complement-deficient C57BL/6-C3-/- mice. Our results indicated, for the first time, that the anticomplement activity of MT1-MMP played a significant role in promoting metastasis in vivo and determined the relative importance of the anticomplement activity in the total metastatic effect of this multifunctional proteolytic enzyme. We believe that our results shed additional light on the functions of MT1-MMP in cancer and clearly make this protease a promising drug target in metastatic malignancies.

Complete Regression of Large Solid Tumors Using Engineered Drug-Resistant Hematopoietic Cells and Anti-CD137 Immunotherapy

Combining chemotherapy and immunotherapy is problematic because chemotherapy can ablate the immune responses initiated by modulators of the immune system. We hypothesized that protection of immunocompetent cells from the toxic effects of chemotherapy, using drug resistance gene therapy strategies, would allow the combined use of chemotherapy and immunotherapy. In wild-type mice, the antitumor effectiveness of an immunotherapy regimen employing an agonistic anti-CD137 antibody is diminished with escalating doses of the antifolate trimetrexate (TMTX). Using retroviral gene transfer of a mutant form of dihydrofolate reductase (L22Y-DHFR), hematopoietic stem cells were genetically engineered to withstand the toxic effects of TMTX. Mice transplanted with L22Y-DHFR-modified bone marrow were then challenged with AG104 sarcoma cells and treated with TMTX only, anti-CD137 only, or a combination of chemotherapy and immunotherapy. Although tumor burden was transiently decreased during TMTX administration, no mice treated with TMTX alone survived the tumor challenge, whereas approximately 40% of transplanted mice treated with anti-CD137 alone survived. However, 100% of mice survived with complete tumor regression after transplantation with L22Y-DHFR-transduced bone marrow followed by combined treatment with TMTX and anti-CD137. In addition, adoptive transfer of splenocytes from cured mice extended the survival of tumor- bearing animals by approximately 3 weeks compared with controls. Therefore, protection of the hematopoietic system can allow for the combined administration of chemotherapy and immunotherapy, which results in complete tumor clearance.

In-situ Demonstration of Mitogen-activated Protein Kinase Erk 1/2 Signalling Pathway in Contagious Respiratory Tumours of Sheep and Goats

Ovine pulmonary adenocarcinoma (OPA) and enzootic nasal adenocarcinoma (ENA) are two contagious neoplastic diseases of secretory epithelial cells in the respiratory system of sheep and goats. Jaagsiekte sheep retrovirus (JSRV) is the aetiological agent of OPA, and enzootic nasal tumour virus (ENTV) is associated with ENA. The genomes of these retroviruses do not contain known oncogenes but products of the env gene are important in the generation of transforming stimuli. However, the cell signalling pathways activated in vivo are not completely understood. This study was based on the use of activation stage antibodies specifically detecting proteins of the extracellular signal regulated kinase Erk 1/2 cell signalling pathway and transcription factors. Tissue sections were collected from four natural cases of OPA, four experimentally induced OPA tumours, four ENA tumours in sheep, four ENA tumours in goats, two normal sheep lungs and two lungs with chronic inflammation. Routine immunohistochemical procedures with phosphorylation stage-specific antibodies were carried out. Representative proteins of the Erk1/2 pathway (Raf-1, Mek1/2 and p44/42MAPK) were activated in natural cases of OPA and ENA in sheep and goats and also in experimentally induced OPA. Transcription factors 90Rsk and Elk-1 were activated in OPA and ENA tumours. However, c-Myc was activated only in OPA tumours. In contagious respiratory neoplasms of sheep and goats the Erk1/2 pathway appears to be important for the in-vivo generation of the transforming stimuli.

Immortalization of normal human cytotrophoblast cells by reconstitution of telomeric reverse transcriptase activity

Placental trophoblast cells are unique endocrine cells that play vital roles during the processes of embryonic implantation and placentation. However, research into the function of human trophoblast has been largely restrained mainly due to a lack of adequate cell models. A normal placenta-origin cytotrophoblast cell line (NPC) was previously established by our group, but these cells showed replicating senescence after 50 population doublings (PDs). In this study, the human telomerase catalytic subunit gene (htert) was transferred into B6 strain of NPC cells, and strains with reconstituted telomerase activity (B6Tert) were established. It was shown that B6Tert-1 cells produce various biomarkers of normal extravillous cytotrophoblasts during the early weeks of gestation. Meanwhile, the cell invasiveness was inhibited by transforming growth factor beta (TGFbeta). However, their ability to form syncytium was relatively low when stimulated with fetal calf serum (FCS). The cells maintained normal cell growth properties and failed to elicit tumours in nude mice. They proliferated continuously with no signs of senescence until the final count at 210 PDs. The growth rate of B6Tert-1 cells was increased when compared with the parental cells, which results, at least partly, from facilitating release of the G1/S checkpoint during the cell-cycle regulation. This is the first report of immortalizing human normal cytotrophoblast (CTB) cells by activation of telomerase activity. The cells will provide an ideal in vitro model for the study of human extravillous trophoblast (EVT) functions and consequently the mechanisms of embryonic implantation and placentation.

Medicinal chemistry approaches to target the kinase activity of IGF-1R

Various drug discovery approaches have been explored in recent years to modulate the function of insulin-like growth factor-1 receptor (IGF-1R). This article focuses on the contributions of low-molecular-mass inhibitors in the modulation of IGF-1R kinase activity, and provides an update on recent reviews for this type of agent. Different classes of compounds have been demonstrated to be capable of modulating the kinase activity of IGF-1R in ways that were not possible previously. Preclinical data with some of these inhibitors support the potential application of IGF-1R-targeted therapeutic strategies in the treatment of human cancers.

Circadian regulation of mouse topoisomerase I gene expression by glucocorticoid hormones

Because glucocorticoid hormones modulate various biological processes, the endogenous rhythm of their secretion is thought to be an important factor affecting the efficacy and/or toxicity of many drugs. Topoisomerase I (Topo I) is a nuclear target of the anticancer drug camptothecin (CPT). In this study, we demonstrate that Topo I expression in tumor-bearing mice and the efficacy of CPT on the tumor are affected by the 24-h variation in circulating glucocorticoid levels. A single administration of corticosterone (CORT) to the tumor-bearing mice resulted in a significant increase in Topo I mRNA levels not only in the tumor masses but also in other healthy tissues such as liver and skeletal muscle. The CORT-induced increase in Topo I mRNA was suppressed by pretreating the mice with RU486, a glucocorticoid receptor antagonist. Significant 24-h oscillations in the Topo I mRNA levels were observed in the tumor and healthy liver without exogenous CORT, and were eliminated by adrenalectomy of the mice. This result suggests that endogenous glucocorticoid hormones are involved in the circadian regulation of Topo I gene expression. Furthermore, the anti-tumor efficacy of the Topo I inhibitor CPT-11 on the tumor-bearing mice was enhanced by administering the drug at the time when the Topo I activity was increased. Our present results demonstrate that glucocorticoid is involved in the 24-h oscillation mechanism of Topo I gene expression and suggest that monitoring the circadian rhythm in Topo I activity is useful for choosing the most appropriate time of day to administer of Topo I inhibitors.

The targeting of phosphoinositide-3 kinase attenuates pulmonary metastatic tumor growth following laparotomy

OBJECTIVE

We aimed to characterize a potential role for phosphatidylinositol 3-kinase (PI3k) in leading to accelerated postoperative metastatic tumor growth.

BACKGROUND

PI3k enhances tumor cell survival in part by phosphorylating Akt and reducing apoptosis. Postoperatively, apoptosis is reduced within local recurrences and distant metastases. This reduction is associated with the phenomenon of accelerated postoperative tumor growth.

METHODS

Balb/c mice underwent a tail vein injection of 1x10 metastatic murine mammary adenocarcinoma 4T1 cells. Animals were divided into the following treatment groups (n=10/group): group A, controls; group B, DMSO intraperitoneally (IP) daily from days 14 to 21; group C, IP LY294002 daily from days 14 to 21; group D, laparotomy only; group E, laparotomy followed by IP DMSO for 7 days; and group F, laparotomy followed by LY294002 IP for 7 days. All laparotomies were performed on day 14. Animals were killed at day 28. Metastatic tumor burden was assessed using the lung/body weight ratio and a histologic metastatic index. Mitotic counts and apoptotic indices were established using a combination of hematoxylin and eosin histology and TUNEL immunohistochemistry. A parallel survival study was performed, and PI3k activity was assessed using western blots for phospho-Akt.

RESULTS

Laparotomy was associated with increased systemic tumor burden (P=0.001). Postoperatively, LY294002 significantly attenuated metastatic tumor growth (P<0.001). Effective PI3k inhibition was confirmed by demonstrating a reduced Akt phosphorylation. Moreover, PI3k inhibition led to reduced proliferation, increased apoptosis (P<0.001), and enhanced postoperative survival (P<0.001).

CONCLUSIONS

Targeting PI3k with postoperative LY294002 significantly attenuates the acceleration in postoperative metastatic tumor growth seen following laparotomy.

Distinct roles for cysteine cathepsin genes in multistage tumorigenesis

Multiple types of degradative enzymes, including cathepsins of the cysteine protease family, have been implicated in the regulation of angiogenesis and invasion during cancer progression. Several cysteine cathepsins are up-regulated in a mouse model of pancreatic islet cell carcinogenesis (RIP1-Tag2), and tumor progression is impaired following their collective pharmacologic inhibition. Using null mutations of four of the implicated cysteine cathepsins, we have now dissected their individual roles in cancer development. Mutants of cathepsins B or S impaired tumor formation and angiogenesis, while cathepsin B or L knockouts retarded cell proliferation and tumor growth. Absence of any one of these three genes impaired tumor invasion. In contrast, removal of cathepsin C had no effect on either tumor formation or progression. We have identified E-cadherin as a target substrate of cathepsins B, L, and S, but not cathepsin C, potentially explaining their differential effects on tumor invasion. Furthermore, we detected analogous increases in cathepsin expression in human pancreatic endocrine neoplasms, and a significant association between increased levels of cathepsins B and L and tumor malignancy. Thus individual cysteine cathepsin genes make distinctive contributions to tumorigenesis.

Modulation of lactate dehydrogenase isozymes by modified base queuine

The modified base queuine is a nutrient factor for lower and higher eukaryotes except yeast. It is synthesized in eubacteria and inserted into the wobble position of specific tRNAs (tRNA(GUN)) in exchange of guanine at position 34. The tRNAs of Q family are completely modified in terminally differentiated somatic cells. However, mainly free queuine is present in embryonic and fast proliferating cells, tRNA remains Q deficient. Lactate dehydrogenase (LDH) A mRNA and LDH A protein is known to increase when cells are grown in hypoxic conditions. In the present study, the level of LDH isozymes is analyzed in different tissues of normal and cancerous (DLA) mice and the effect of queuine treatment on LDH isozyme is observed. LDH A isozyme is shown to increase in serum and liver of DLA mice. The level and activity of LDH A decreases on queuine treatment. In skeletal muscle and heart, LDH A isozyme decreases while LDH B increases in DLA mice. Queuine administration leads to change back towards normal. In case of brain, LDH A increases but LDH B decreases in DLA mice. Queuine treatment leads to decrease in A4 anaerobic isozymes of LDH. The results suggest that queuine suppresses anaerobic glycolytic pathway, which leads to tumor suppression of DLA mice.

Entrapment of retroviral vector producer cells in three-dimensional alginate scaffolds for potential use in cancer gene therapy

We explored the possibility of entrapping retroviral vector producing cells (VPC) within porous 3D matrix to induce a local and sustained release of viral particles to the malignant milieu. PA317/STK, which constantly shed retroviral vectors, was used to transduce cancer cells with the herpes simplex virus thymidine kinase (HSV-tk) gene. Once HSV-tk is expressed, it preferentially phosphorylates nucleoside analog prodrugs, such as ganciclovir (GCV) and N-methanocarbathymidine (N-MCT), to their active triphosphate metabolites, which when incorporated into cellular DNA cause cell death. PA317/STK cells were seeded within 3D alginate scaffold at two different cell densities via static seeding procedure. In vitro assays determined that PA317/STK seeded at high-cell density in scaffolds maintained constant cell number, low cell leakage, and spheroid morphology with viral vector transfection activity. Postcell-seeding viral vector activity was confirmed by transfection of murine colon cancer cells (MC38) with conditioned media originated from VPC-containing scaffolds and the subsequent ability to generate N-MCT triphosphate. Preliminary in vivo transplantation of VPC-containing scaffolds into the peritoneal cavity of mice bearing intraperitoneal MC38 tumors with 2 weeks subsequent GCV administration resulted in a significantly higher survival rate relative to control groups. Our results demonstrate the feasibility of employing alginate scaffolds to efficiently entrap and support PA317/STK cells for cancer gene therapy.

[Effect of preliminary irradiation on DNA-ase activity and DNA fragmentation degree in the nuclei of Guerin's carcinoma cells]

The effect of preliminary irradiation on DNA-ase activity and DNA fragmentation degree in the nuclei of Guerin's carcinoma was evaluated. It was found that effective growth of malignant cells involved higher concentrations of acid DNA-ase matched by decreased levels of alkaline one which in turn lowered the rates of DNA fragmentation. Low-dose preliminary irradiation stimulated relevant processes.

Indoleamine 2,3-dioxygenase serves as a marker of poor prognosis in gene expression profiles of serous ovarian cancer cells

PURPOSE

We aimed to find key molecules associated with chemoresistance in ovarian cancer using gene expression profiling as a screening tool.

EXPERIMENTAL DESIGN

Using two newly established paclitaxel-resistant ovarian cancer cell lines from an original paclitaxel-sensitive cell line and four supersensitive and four refractory surgical ovarian cancer specimens from paclitaxel-based chemotherapy, molecules associated with chemoresistance were screened with gene expression profiling arrays containing 39,000 genes. We further analyzed 44 genes that showed significantly different expressions between paclitaxel-sensitive samples and paclitaxel-resistant samples with permutation tests, which were common in cell lines and patients' tumors.

RESULTS

Eight of these genes showed reproducible results with real-time reverse transcription-PCR, of which indoleamine 2,3-dioxygenase gene expression was the most prominent and consistent. Moreover, by immunohistochemical analysis using a total of 24 serous-type ovarian cancer surgical specimens (stage III, n = 21; stage IV, n = 7), excluding samples used for GeneChip analysis, the Kaplan-Meier survival curve showed a clear relationship between indoleamine 2,3-dioxygenase staining patterns and overall survival (log-rank test, P = 0.0001). All patients classified as negative survived without relapse. The 50% survival of patients classified as sporadic, focal, and diffuse was 41, 17, and 11 months, respectively.

CONCLUSION

The indoleamine 2,3-dioxygenase screened with the GeneChip was positively associated with paclitaxel resistance and with impaired survival in patients with serous-type ovarian cancer.

Expression of the ubiquitin-proteasome pathway and muscle loss in experimental cancer cachexia

Muscle protein degradation is thought to play a major role in muscle atrophy in cancer cachexia. To investigate the importance of the ubiquitin-proteasome pathway, which has been suggested to be the main degradative pathway mediating progressive protein loss in cachexia, the expression of mRNA for proteasome subunits C2 and C5 as well as the ubiquitin-conjugating enzyme, E2_14k, has been determined in gastrocnemius and pectoral muscles of mice bearing the MAC16 adenocarcinoma, using competitive quantitative reverse transcriptase polymerase chain reaction. Protein levels of proteasome subunits and E2_14k were determined by immunoblotting, to ensure changes in mRNA were reflected in changes in protein expression. Muscle weights correlated linearly with weight loss during the course of the study. There was a good correlation between expression of C2 and E2_14k mRNA and protein levels in gastrocnemius muscle with increases of 6–8-fold for C2 and two-fold for E2_14k between 12 and 20% weight loss, followed by a decrease in expression at weight losses of 25–27%, although loss of muscle protein continued. In contrast, expression of C5 mRNA only increased two-fold and was elevated similarly at all weight losses between 7.5 and 27%. Both proteasome functional activity, and proteasome-specific tyrosine release as a measure of total protein degradation was also maximal at 18–20% weight loss and decreased at higher weight loss. Proteasome expression in pectoral muscle followed a different pattern with increases in C2 and C5 and E2_14k mRNA only being seen at weight losses above 17%, although muscle loss increased progressively with increasing weight loss. These results suggest that activation of the ubiquitin-proteasome pathway plays a major role in protein loss in gastrocnemius muscle, up to 20% weight loss, but that other factors such as depression in protein synthesis may play a more important role at higher weight loss.

[A change of tumor PyNPase level at intraperitoneal and intravenous administrations of paclitaxel]

A level of PyNPase activity was measured after intraperitoneal (ip) and intravenous (i.v.) administrations of paclitaxel on the animal model. Nude mice received the subcutaneous implantation of WiDr cells. About 3 weeks later, the ip and i.v. administrations of paclitaxel were performed 2 times at 20 mg/kg and 15 mg/kg, respectively. About 1 week later, the mice were sacrificed. The level of PyNPase activity was measured by the ELISA method. The level of PyNPase of ip and i.v. was higher than that of the control group, but the level of PyNPase revealed no significant difference between ip and i.v.. This result suggested that intraperitoneal administration of paclitaxel enhanced an efficiency of 5'-DFUR and capecitabine as much as intravenous administration of paclitaxel.

5-Aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside inhibits cancer cell proliferation in vitro and in vivo via AMP-activated protein kinase

5-Aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR) is widely used as an AMP-kinase activator, which regulates energy homeostasis and response to metabolic stress. Here, we investigated the effect of AICAR, an AMPK activator, on proliferation of various cancer cells and observed that proliferation of all the examined cell lines was significantly inhibited by AICAR treatment due to arrest in S-phase accompanied with increased expression of p21, p27, and p53 proteins and inhibition of PI3K-Akt pathway. Inhibition in in vitro growth of cancer cells was mirrored in vivo with increased expression of p21, p27, and p53 and attenuation of Akt phosphorylation. Anti-proliferative effect of AICAR is mediated through activated AMP-activated protein kinase (AMPK) as iodotubericidin and dominant-negative AMPK expression vector reversed the AICAR-mediated growth arrest. Moreover, constitutive active AMPK arrested the cells in S-phase by inducing the expression of p21, p27, and p53 proteins and inhibiting Akt phosphorylation, suggesting the involvement of AMPK. AICAR inhibited proliferation in both LKB and LKB knock-out mouse embryo fibroblasts to similar extent and arrested cells at S-phase when transfected with dominant negative expression vector of LKB. Altogether, these results indicate that AICAR can be utilized as a therapeutic drug to inhibit cancer, and AMPK can be a potential target for treatment of various cancers independent of the functional tumor suppressor gene, LKB.

Modulation of xenobiotic-metabolizing enzymes by ethanolic neem leaf extract during hamster buccal pouch carcinogenesis

Chemoprevention by medicinal plants is a promising approach for controlling cancer. There is substantial evidence to indicate that chemopreventive agents exert their anticarcinogenic effects by modulation of phase I and phase II xenobiotic-metabolizing enzymes. Therefore, we examined the chemopreventive potential of ethanolic neem leaf extract (ENLE) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Hamsters were divided into four groups of six animals each. The right buccal pouches of animals in Group I were painted with 0.5 per cent DMBA in liquid paraffin three times per week. Animals in Group 2 painted with DMBA as in group 1, received in addition, intragastric administration of ENLE at a concentration of 200 mg/kg bw three times per week on days alternate to DMBA application. Group 3 was given ENLE alone. Animals in Group 4 served as controls. All animals were killed after an experimental period of 14 weeks. Five out of six hamsters painted with DMBA alone developed squamous cell carcinomas in the buccal pouch. The HBP tumours showed an increase in phase I carcinogen activation (cytochrome P450 and b5) and phase II detoxification enzyme (glutathione-S-transferase, DT-diaphorase and NADPH-diaphorase) activities. In the liver of tumour-bearing animals, enhanced cytochrome P450 and b5 levels were accompanied by a decrease in phase II detoxification enzyme activities. Administration of ENLE effectively suppressed DMBA-induced HBP tumours, decreased cytochrome P450 and b5 levels, and enhanced phase II enzyme activities in the pouch and liver. Our results suggest that the modulation of DMBA metabolism is a possible mechanism for the chemopreventive effects of ethanolic neem leaf extract.

p53-defective tumors with a functional apoptosome-mediated pathway: a new therapeutic target

BACKGROUND

Although cancer cells appear to maintain the machinery for intrinsic apoptosis, defects in the pathway develop during malignant transformation, preventing apoptosis from occurring. How to specifically induce apoptosis in cancer cells remains unclear.

METHODS

We determined the apoptosome activity and p53 status of normal human cells and of lung, colon, stomach, brain, and breast cancer cells by measuring cytochrome c-dependent caspase activation and by DNA sequencing, respectively, and we used COMPARE analysis to identify apoptosome-specific agonists. We compared cell death, cytochrome c release, and caspase activation in NCI-H23 (lung cancer), HCT-15 (colon cancer), and SF268 (brain cancer) cells treated with Triacsin c, an inhibitor of acyl-CoA synthetase (ACS), or with vehicle. The cells were mock, transiently, or stably transfected with genes for Triacsin c-resistant ACSL5, dominant negative caspase-9, or apoptotic protease activating factor-1 knockdown. We measured ACS activity and levels of cardiolipin, a mitochondrial phospholipid, in mock and ACSL5-transduced SF268 cells. Nude mice carrying NCI-H23 xenograft tumors (n = 10) were treated with Triacsin c or vehicle, and xenograft tumor growth was assessed. Groups were compared using two-sided Student t tests.

RESULTS

Of 21 p53-defective tumor cell lines analyzed, 17 had higher apoptosome activity than did normal cells. Triacsin c selectively induced apoptosome-mediated death in tumor cells (caspase activity of Triacsin c-treated versus untreated SF268 cells; means = 1020% and 100%, respectively; difference = 920%, 95% CI = 900% to 940%; P<.001). Expression of ACSL5 suppressed Triacsin c-induced cytochrome c release and subsequent cell death (cell survival of Triacsin c-treated mock- versus ACSL5-transduced SF268 cells; means = 40% and 83%, respectively; difference = 43%, 95% CI = 39% to 47%; P<.001). ACS was also essential to the maintenance of cardiolipin levels. Finally, Triacsin c suppressed growth of xenograft tumors (relative tumor volume on day 21 of Triacsin c-treated versus untreated mice; means = 4.6 and 9.6, respectively; difference = 5.0, 95% CI = 2.1 to 7.9; P = .006).

CONCLUSIONS

Many p53-defective tumors retain activity of the apoptosome, which is therefore a potential target for cancer chemotherapy. Inhibition of ACS may be a novel strategy to induce the death of p53-defective tumor cells.

USP19 is a ubiquitin-specific protease regulated in rat skeletal muscle during catabolic states

Ubiquitin-dependent proteolysis is activated in skeletal muscle atrophying in response to various catabolic stimuli. Previous studies have demonstrated activation of ubiquitin conjugation. Because ubiquitination can also be regulated by deubiquitinating enzymes, we used degenerate oligonucleotides derived from conserved sequences in the ubiquitin-specific protease (UBP) family of deubiquitinating enzymes in RT-PCR with skeletal muscle RNA to amplify putative deubiquitinating enzymes. We identified USP19, a 150-kDa deubiquitinating enzyme that is widely expressed in various tissues including skeletal muscle. Expression of USP19 mRNA increased by approximately 30-200% in rat skeletal muscle atrophying in response to fasting, streptozotocin-induced diabetes, dexamethasone treatment, and cancer. Increased mRNA levels during fasting returned to normal with refeeding, but 1 day later than the normalization of rates of proteolysis and coincided instead with recovery of muscle mass. Indeed, in all catabolic treatments, USP19 mRNA was inversely correlated with muscle mass and provided an index of muscle mass that may be useful in many pathological conditions, using small human muscle biopsies. The increased expression of this deubiquitinating enzyme under conditions of increased proteolysis suggests that it may play a role in regeneration of free ubiquitin either coincident with or after proteasome-mediated degradation of substrates. USP19 may also be involved in posttranslational processing of polyubiquitin produced de novo in response to induction of the polyubiquitin genes seen under these conditions. Deubiquitinating enzymes thus appear involved in muscle wasting and implicate a widening web of regulation of genes in the ubiquitin system in this process.