24-hour oscillation of mouse methionine aminopeptidase2, a regulator of tumor progression, is regulated by clock gene proteins

Methionine aminopeptidase2 (MetAP2) plays an important role in the growth of endothelial cells during the tumor angiogenesis stage. Recently, we have clarified that mouse methionine aminopeptidases (mMetAPs) show a 24-hour rhythm in implanted tumor masses. In the present study, we investigated the mechanism underlying the 24-hour rhythm of mMetAP2 activity in tumor-bearing mice under a light-dark (lights on from 7 a.m. to 7 p.m.) cycle. The 5' flanking region of mMetAP2 included eight E-boxes. The transcription of the mMetAP2 promoter was enhanced by the mCLOCK:mBMAL1 heterodimer, and its activation was inhibited by mPER2 or mCRY1. Deletion and mutation of the E-boxes in the region indicated that the E-box nearest to the initiation start site played an important role in the transcriptional regulation by clock genes. In sarcoma180-bearing mice, the pattern of binding of mCLOCK and mBMAL1 to the E-box and transcription of the mMetAP2 promoter showed a 24-hour rhythm with higher levels from the mid-light to early dark phase. The pattern of mMetAP2 transcription was closely associated with that of mMetAP2 mRNA expression in three types of tumor-bearing mice. mMetAP2 protein expression varied with higher levels from the late-dark to early light phase. The rhythmicity of the protein expression was synchronous with that of the activity of mMetAPs but out of phase with that of the mMetAP2 mRNA expression. These results suggest that the 24-hour rhythm of mMetAP2 activity is regulated by the transcription of clock genes within the clock feedback loops.

Granzyme B and the Downstream Granzymes C and/or F Are Important for Cytotoxic Lymphocyte Functions

Although the functions of granzyme A (GzmA) and GzmB are well-defined, a number of orphan granzymes of unknown function are also expressed in cytotoxic lymphocytes. Previously, we showed that a targeted loss-of-function mutation for GzmB was associated with reduced expression of several downstream orphan granzyme genes in the lymphokine-activated killer cell compartment. To determine whether this was caused by the retained phosphoglycerate kinase I gene promoter (PGK-neo) cassette in the GzmB gene, we retargeted the GzmB gene with a LoxP-flanked PGK-neo cassette, then removed the cassette in embryonic stem cells by transiently expressing Cre recombinase. Mice homozygous for the GzmB null mutation containing the PGK-neo cassette (GzmB-/-/+PGK-neo) displayed reduced expression of the closely linked GzmC and F genes in their MLR-derived CTLs and lymphokine-activated killer cells; removal of the PGK-neo cassette (GzmB-/-/DeltaPGK-neo) restored the expression of both genes. Cytotoxic lymphocytes derived from mice with the retained PGK-neo cassette (GzmB-/-/+PGK-neo) had a more severe cytotoxic defect than those deficient for GzmB only (GzmB-/-/DeltaPGK-neo). Similarly, GzmB-/-/+PGK-neo mice displayed a defect in the allogeneic clearance of P815 tumor cells, whereas GzmB-/-/DeltaPGK-neo mice did not. These results suggest that the retained PGK-neo cassette in the GzmB gene causes a knockdown of GzmC and F expression, and also suggest that these granzymes are relevant for the function of cytotoxic lymphocytes in vitro and in vivo.

Controlling tumor growth by modulating endogenous production of reactive oxygen species

Paradoxically, reactive oxygen species (ROS) can promote normal cellular proliferation and carcinogenesis, and can also induce apoptosis of tumor cells. In this report, we study the contribution of ROS to various cellular signals depending on the nature and the level of ROS produced. In nontransformed NIH 3T3 cells, ROS are at low levels and originate from NADPH oxidase. Hydrogen peroxide (H(2)O(2)), controlled by the glutathione system, is pivotal for the modulation of normal cell proliferation. In CT26 (colon) and Hepa 1-6 (liver) tumor cells, high levels of ROS, close to the threshold of cytotoxicity, are produced by mitochondria and H(2)O(2) is controlled by catalase. N-acetylcysteine, which decreases H(2)O(2) levels, inhibits mitogen-activated protein kinase and normal cell proliferation but increases tumor cell proliferation as H(2)O(2) concentration drops from the toxicity threshold. In contrast, antioxidant molecules, such as mimics of superoxide dismutase (SOD), increase H(2)O(2) levels through superoxide anion dismutation, as well as in vitro proliferation of normal cells, but kill tumor cells. CT26 tumors were implanted in mice and treated by oxaliplatin in association with one of the three SOD mimics manganese(III)tetrakis(4-benzoic acid) porphyrin, copper(II)(3,5-diisopropylsalicylate)2, or manganese dipyridoxyl diphosphate. After 1 month, the volumes of tumors were respectively 35%, 31%, and 63% smaller than with oxaliplatin alone (P < 0.001). Similar data were gained with Hepa 1-6 tumors. In conclusion, antioxidant molecules may have opposite effects on tumor growth. SOD mimics can act in synergy with cytotoxic drugs to treat colon and liver cancers.

Mechanism of the Attenuation of Proteolysis-Inducing Factor Stimulated Protein Degradation in Muscle by β-Hydroxy-β-Methylbutyrate

The leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) prevents muscle protein degradation in cancer-induced weight loss through attenuation of the ubiquitin-proteasome proteolytic pathway. To investigate the mechanism of this effect, the action of HMB on protein breakdown and intracellular signaling leading to increased proteasome expression by the tumor factor proteolysis-inducing factor (PIF) has been studied in vitro using murine myotubes as a surrogate model of skeletal muscle. A comparison has been made of the effects of HMB and those of eicosapentaenoic acid (EPA), a known inhibitor of PIF signaling. At a concentration of 50 mumol/L, EPA and HMB completely attenuated PIF-induced protein degradation and induction of the ubiquitin-proteasome proteolytic pathway, as determined by the "chymotrypsin-like" enzyme activity, as well as protein expression of 20S proteasome alpha- and beta-subunits and subunit p42 of the 19S regulator. The primary event in PIF-induced protein degradation is thought to be release of arachidonic acid from membrane phospholipids, and this process was attenuated by EPA, but not HMB, suggesting that HMB might act at another step in the PIF signaling pathway. EPA and HMB at a concentration of 50 mumol/L attenuated PIF-induced activation of protein kinase C and the subsequent degradation of inhibitor kappaBalpha and nuclear accumulation of nuclear factor kappaB. EPA and HMB also attenuated phosphorylation of p42/44 mitogen-activated protein kinase by PIF, thought to be important in PIF-induced proteasome expression. These results suggest that HMB attenuates PIF-induced activation and increased gene expression of the ubiquitin-proteasome proteolytic pathway, reducing protein degradation.

Hepsin paradox reveals unexpected complexity of metastatic process

The existing models of cancer progression assume that a linear sequence of genetic and epigenetic events occurs during this process. In this representation every new event (either loss of a tumor-suppressor, or activation of a proto-oncogene) makes cells even more malignant. The result is a "super" cell that can form metastases at the distant sites. Metastatic cells are believed to carry all genetic and epigenetic characteristics that are necessary for metastasis formation. Recently, we have shown that cell-surface protease hepsin causes disorganization of the basement membrane and promotes prostate cancer progression and metastasis. In human prostate cancer hepsin is upregulated in the precancerous lesions and this upregulation is maintained in the primary tumors. Remarkably and completely unexpected for a metastasis-promoting gene, hepsin is expressed at low levels in metastatic lesions and the message is completely absent in metastasis-derived prostate cancer cell lines. These results demonstrate that genes that play an important role in metastatic process may exercise their role only at the specific fragments of cancer progression pathway (for example, during initial invasion and tissue disorganization in the primary organ) and may have no role in metastatic lesions. Future treatment of cancer patients may rely heavily on monitoring of tumor progression, as treatment efficient in attenuation of initial tumor progression may be inefficient or even adverse at the advance stages of disease.

Decreased nucleotide excision repair activity and alterations of topoisomerase IIalpha are associated with the in vivo resistance of a P388 leukemia subline to F11782, a novel catalytic inhibitor of topoisomerases I and II

PURPOSE

The purpose of the study was to investigate the mechanisms associated with antitumor activity and resistance to F11782, a novel dual catalytic inhibitor of topoisomerases with DNA repair-inhibitory properties.

EXPERIMENTAL DESIGN

For that purpose, an F11782-resistant P388 leukemia subline (P388/F11782) has been developed in vivo and characterized.

RESULTS

Weekly subtherapeutic doses of F11782 (10 mg/kg) induced complete resistance to F11782 after 8 weekly passages. This resistant P388/F11782 subline retained some in vivo sensitivity to several DNA-topoisomerase II and/or I complex-stabilizing poisons and showed marked collateral sensitivity to cisplatin, topotecan, colchicine, and Vinca alkaloids, while proving completely cross-resistant only to merbarone and doxorubicin. Therefore, resistance to F11782 did not appear to be associated with a classic multidrug resistance profile, as further reflected by unaltered drug uptake and no overexpression of resistance-related proteins or modification of the glutathione-mediated detoxification process. In vivo resistance to F11782 was, however, associated with a marked reduction in topoisomerase IIalpha protein (87%) and mRNA (50%) levels, as well as a diminution of the catalytic activity of topoisomerase IIalpha. In contrast, only minor reductions in topoisomerases IIbeta and I levels were recorded. However, of major interest, nucleotide excision repair activity was decreased 3-fold in these P388/F11782 cells and was more specifically associated with a decreased (67%) level of XPG (human xeroderma pigmentosum group G complementing protein), an endonuclease involved in this DNA repair system.

CONCLUSIONS

These findings suggest that both topoisomerase IIalpha and XPG are major targets of F11782 in vivo and further demonstrate the original mechanism of action of this novel compound.

Catalytic domain of PRL-3 plays an essential role in tumor metastasis: formation of PRL-3 tumors inside the blood vessels

PRL-3, a protein tyrosine phosphatase, has attracted much attention as its transcript is consistently upregulated in the process of colorectal cancer metastases to secondary organs. We studied mice injected via the tail vein with CHO cells stably expressing EGFP-tagged PRL-3 or catalytically inactive mutant PRL-3 (C104S). Our data showed that the EGFP-PRL-3-expressing cells rapidly induce metastatic tumor formation in lung, while EGFP-PRL-3 (C104S)-expressing cells lose this metastastic activity. Furthermore, detailed microscopic examinations revealed that some EGF-PRL-3-, but not EGFP-PRL-3 (C104S)-, expressing cells form micro- and macro-metastatic solid tumors that sprout into blood vessels. Our studies provide clear evidence for a causative role of PRL-3 phosphatase activity in cancer metastasis and tumor-related angiogenesis events. The catalytic domain of PRL-3 could serve as an ideal therapeutic target for drug development to block the spread of colorectal cancer.

Rapamycin inhibits Akt-mediated oncogenic transformation and tumor growth

Akt is a serine/threonine kinase that plays a critical role in cell survival and proliferation. Three isoforms of Akt have been identified and have been shown to be up-regulated in human malignancies. We examined the requirement of these pathways for Akt transformation. We generated NIH-3T3 cells over-expressing constitutively active Myr-Akt1 (3T3-Akt1 cells) or Myr-Akt2 (3T3-Akt2 cells). These cells are able to form colonies in soft-agar and 3T3-Akt1 cells formed tumors in SCID mice. Rapamycin efficiently inhibited the activation of the mTOR-p70S6K pathway and the anchorage-independent growth of both 3T3-Akt cells, demonstrating the importance of the mTOR-p70S6K pathway for transformation by Akt1 as well as by Akt2. Moreover, rapamycin dramatically inhibited the tumor formation by 3T3-Akt1 cells in SCID mice. Thus, we demonstrated the importance of mTOR-p70S6 kinase pathway in the transformation by Akt, both in tissue-cultured cells and in animal tumor models. In contrast, neither the MAPK pathway nor the p38 MAPK pathway is required for Akt-dependent transformation of NIH3T3 cells.

Accumulation of the oxidative base lesion 8-hydroxyguanine in DNA of tumor-prone mice defective in both the Myh and Ogg1 DNA glycosylases

The OGG1 and MYH DNA glycosylases prevent the accumulation of DNA 8-hydroxyguanine. In Myh(-/-) mice, there was no time-dependent accumulation of DNA 8-hydroxyguanine in brain, small intestine, lung, spleen, or kidney. Liver was an exception to this general pattern. Inactivation of both MYH and OGG1 caused an age-associated accumulation of DNA 8-hydroxyguanine in lung and small intestine. The effects of abrogated OGG1 and MYH on hepatic DNA 8-hydroxyguanine levels were additive. Because there is an increased incidence of lung and small intestine cancer in Myh(-/-)/Ogg1(-/-) mice, these findings support a causal role for unrepaired oxidized DNA bases in cancer development.

Angiontensin-converting enzyme activity in dunning rat prostate tumor

A dipeptidyl carboxypeptidase activity in the Dunning rat prostate tumor was characterized. This enzyme demonstrated the most prominent properties of angiotensin converting enzyme (ACE): that is, it was stimulated by NaCl and Co(2+) and was potently inhibited by captopril. The enzyme solubilized by Triton X-100 had a molecular mass of 110 kDa as determined by gel filtration chromatography. The specific activity of ACE did not change with castration, indicating that ACE activities are not controlled by androgen. The role of ACE in the prostate and its tumors is not understood, but the ability of this enzyme to hydrolyze a number of bioactive peptides suggests that it may function in controlling the molecular forms or activity of regulatory peptides.

Cysteine cathepsins (proteases)--on the main stage of cancer?

Cysteine cathepsins are involved in degradation of extracellular matrix, facilitating growth, invasion, and metastasis of tumor cells, in tumor angiogenesis, in apoptosis, and in events of inflammatory and immune responses. In this issue of Cancer Cell, demonstrate association of increased cathepsins activity with angiogenic vasculature and invasive fronts of carcinomas during tumorigenesis in transgenic mouse models using activity-based chemical probes and in vivo imaging. Moreover, this study shows that a broad-spectrum cysteine cathepsin inhibitor effectively blocks several stages of tumorigenesis in the RIP1-Tag2 transgenic mouse model, offering new therapeutic opportunities in cancer treatment.

[Extracellular DNA fragments and DNAse activity in blood serum of rats with transplantated Guerin's carcinoma after multiple exposures to low doses of X-irradiation]

The fraction composition of extracellular free DNA (cfDNA) and activity of serum DNAses in blood of rats with the tumor transplantated against a background of the low-dose X-irradiation were investigated. Heterogeneous fragments of cfDNA and high level of DNAse activity were revealed in the serum of irradiated rats. The definite sizes of high-molecular homogenous fraction of cfDNA, which is observed in the serum of irradiated and unirradiated rats with tumor, and its presence from the first stages of tumor growth independent of serum DNAses activity show, that the emergence of this fraction is not accidental. Previous fractionated irradiation makes influence on the investigation data only on the primary stages of tumor growth.

Combined effects of cyclooxygenase-1 and cyclooxygenase-2 selective inhibitors on intestinal tumorigenesis in adenomatous polyposis coli gene knockout mice

As with cyclooxygenase (COX)-2, genetic disruption of COX-1 gene or pharmacologic inhibition of its activity has been shown to decrease the number of intestinal polyps in Apc gene-deficient mice. The present study was designed to investigate the combined effects of COX-1 and COX-2 selective inhibitors on spontaneous polyp formation in APC1309 female mice. The animals were treated with 300 or 600 ppm mofezolac (a COX-1 selective inhibitor) alone, 200 or 400 ppm nimesulide (a COX-2 selective inhibitor) alone, 300 ppm mofezolac plus 200 ppm nimesulide, 600 ppm mofezolac plus 400 ppm nimesulide, or 10 ppm indomethacin (a dual-COX inhibitor) in the diet from 7 weeks of age for 4 weeks. Percentage inhibition of polyp area in the intestine was 17% with 600 ppm mofezolac alone and 25% with 400 ppm nimesulide alone, their sum of 42% being almost equal to the 37% observed for the combination treatment. Administration of 300 ppm mofezolac plus 200 ppm nimesulide also significantly decreased polyp area in the intestine by 30%. Moreover, the numbers of polyps more than 2.5 mm in diameter were markedly decreased by combined treatment of both COX inhibitors. With 10 ppm indomethacin, the dual inhibitor, polyp area was also clearly reduced by 46%. Our results indicate that COX-1 and COX-2 may to some extent contribute to polyp formation independently and inhibitor combination treatment thus has particular potential for chemoprevention of colon carcinogenesis.

Thymidylate synthase as an oncogene: a novel role for an essential DNA synthesis enzyme

Thymidylate synthase (TS) is an E2F1-regulated enzyme that is essential for DNA synthesis and repair. TS protein and mRNA levels are elevated in many human cancers, and high TS levels have been correlated with poor prognosis in patients with colorectal, breast, cervical, bladder, kidney, and non-small cell lung cancers. In this study, we show that ectopic expression of catalytically active TS is sufficient to induce a transformed phenotype in mammalian cells as manifested by foci formation, anchorage independent growth, and tumor formation in nude mice. In contrast, comparable levels of two TS mutants carrying single point mutations within the catalytic domain had no transforming activity. In addition, we show that overexpression of TS results in apoptotic cell death following serum removal. These data demonstrate that TS exhibits oncogene-like activity and suggest a link between TS-regulated DNA synthesis and the induction of a neoplastic phenotype.

Inducible expression of a MAP kinase phosphatase-3-GFP chimera specifically blunts fibroblast growth and ras-dependent tumor formation in nude mice

The p42/p44 mitogen activated protein kinase (MAPK) pathway participates in a wide range of cellular programs including proliferation, migration, differentiation, and survival. Specific pharmacological inhibitors, like PD98059 and U0126, are often used to inhibit p42/p44 MAPK signaling. However, these inhibitors are not appropriate to study the function of these kinases in whole organisms. We thus developed an inducible system designed to inhibit p42/p44 MAPK activity through the expression of a phosphatase specific for these two kinases, the MAPK phosphatase 3 (MKP-3). A fibroblast cell line was established in which MKP-3 expression is controlled by tetracycline. Tetracycline-induced MKP-3 resulted in partial de-phosphorylation of p42/p44 MAPKs in serum-stimulated cells. However, we could improve MKP-3 stability and thereby the rate of MAPK de-phosphorylation, when the C-terminal end of MKP-3 was fused to the green fluorescent protein (GFP). Importantly, the fusion of GFP to MKP-3 did not alter the specificity of the phosphatase towards its MAPK substrates. We further show that conditional expression of MKP-3-GFP in this fibroblast cell line results in the inhibition of: (a) the phosphorylation of the p42/p44 MAPK substrates Elk1 and HIF-1alpha, (b) vascular endothelial growth factor (VEGF), cyclin D1, and c-fos gene transcription in response to MAPK pathway activation, and (c) cell proliferation. Finally, the MKP-3-GFP inducible cell line was transformed by Ha-ras and injected into nude mice. Treatment of mice with the tetracycline analog doxycycline resulted in a large delay in tumor emergence and growth as compared to the untreated control group, indicating that MKP-3-GFP activity is maintained in vivo. Altogether, these results show that inducible expression of MKP-3-GFP constitutes a valuable tool to study the role of p42/p44 MAPKs in various cellular responses in both cultured cell and animal models, a tool that may also be used to block unwanted cell growth in pathological conditions.

The oncolytic effect of recombinant vesicular stomatitis virus is enhanced by expression of the fusion cytosine deaminase/uracil phosphoribosyltransferase suicide gene

Vesicular stomatitis virus (VSV) has recently been demonstrated to exhibit significant oncolytic capabilities against a wide variety of tumor models in vitro and in vivo. To potentially enhance the oncolytic effect, we generated a novel recombinant VSV (rVSV) that expressed the fusion suicide gene Escherichia coli cytosine deaminase (CD)/uracil phosphoribosyltransferase (UPRT). rVSV encoding the CD/UPRT fusion gene (VSV-C:U) exhibited normal growth properties and generated high levels of biologically active CD/UPRT that could catalyze the modification of 5-fluorocytosine into chemotherapeutic 5-fluorouracil (5-FU), which exhibited considerable bystander effect. Intratumoral inoculation of VSV-C:U in the presence of the systemically administered prodrug 5-fluorocytosine produced statistically significant reductions in the malignant growth of syngeneic lymphoma (A20) or mammary carcinoma (TSA) in BALB/c mice compared with rVSV treatments or with control 5-FU alone. Aside from detecting prolonged therapeutic levels of 5-FU in VSV-C:U-treated animals harboring TSA tumors and enhancing bystander killing of tumor cells, we demonstrated marked activation of IFN-gamma-secreting cytotoxic T cells by enzyme-linked immunospot analysis that may have also facilitated tumor killing. In conclusion, the insertion of the fusion CD/UPRT suicide gene potentiates the oncolytic efficiency of VSV by generating a strong bystander effect and by contributing to the activation of the immune system against the tumor without detrimentally altering the kinetics of virus-mediated oncolysis and may be useful in the treatment of malignant disease.

Telomere dysfunction results in enhanced organismal sensitivity to the alkylating agent N-methyl-N-nitrosourea

Here, we use telomerase-deficient mice, Terc(-/-), to study the impact of telomerase abrogation in response to treatment with the alkylating agent N-Methyl-N-Nitrosourea (MNU), a potent carcinogen in the mouse. Wild-type mice treated with MNU developed lymphomas and carcinomas. In contrast, similarly treated G5 Terc(-/-) mice with critically short telomeres did not develop tumors and died of acute toxicity to the small intestine. G2 Terc(-/-) mice, which have long telomeres, were less susceptible to MNU-induced tumors than wild-type mice, as well as less sensitive to MNU toxicity than G5 Terc(-/-) mice. The results indicate that short telomeres suppress tumor growth and that lack of telomerase retards tumor progression, even in the presence of long telomeres. Finally, G5 Terc(-/-) hypersensitivity to MNU supports the notion that short telomeres interfere with proper DNA damage repair.

CEP-7055: a novel, orally active pan inhibitor of vascular endothelial growth factor receptor tyrosine kinases with potent antiangiogenic activity and antitumor efficacy in preclinical models

Inhibition of the vascular endothelial growth factor VEGF-VEGF receptor (VEGF-R) kinase axes in the tumor angiogenic cascade is a promising therapeutic strategy in oncology. CEP-7055 is the fully synthetic orally active N,N-dimethyl glycine ester of CEP-5214, a C3-(isopropylmethoxy) fused pyrrolocarbazole with potent pan-VEGF-R kinase inhibitory activity. CEP-5214 demonstrates IC(50) values of 18 nM, 12 nM, and 17 nM against human VEGF-R2/KDR kinase, VEGF-R1/FLT-1 kinase, and VEGF-R3/FLT-4 kinase, respectively, in biochemical kinase assays. CEP-5214 inhibited VEGF-stimulated VEGF-R2/KDR autophosphorylation in human umbilical vein endothelial cells (HUVECs) with an IC (50) of approximately 10 nM and demonstrated an equivalent inhibition of murine FLK-1 autophosphorylation in transformed SVR endothelial cells. Evaluation of the antiangiogenic activity of CEP-5214 revealed a dose-related inhibition of microvessel growth ex vivo in rat aortic ring explant cultures and in vitro on HUVEC capillary-tube formation on Matrigel at low nanomolar concentrations. The antiangiogenic activity of CEP-5214 in these bioassays was observed in the absence of apparent cytotoxicity. Single-dose p.o. or s.c. administration of CEP-7055 or CEP-5214 to CD-1 mice at 23.8 mg/kg/dose b.i.d. resulted in a reversible inhibition of VEGF-R2/FLK-1 phosphorylation in murine lung tissues. Administration p.o. of CEP-7055 at 2.57 to 23.8 mg/kg/dose b.i.d. resulted in dose-related reductions in neovascularization in vivo in porcine aortic endothelial cell (PAEC)-VEGF/basic fibroblast growth factor-Matrigel implants in nude mice (maximum, 82% inhibition), significant reductions in granuloma formation (30%) and granuloma vascularity (42%) in a murine chronic inflammation-induced angiogenesis model, and significant and sustained (6 h) inhibition of VEGF-induced plasma extravasation in rats, with an ED(50) of 20 mg/kg/dose. Chronic p.o. administration of CEP-7055 at doses of 11.9 to 23.8 mg/kg/dose b.i.d. resulted in significant inhibition (50-90% maximum inhibition relative to controls) in the growth of a variety of established murine and human s.c. tumor xenografts in nude mice, including A375 melanomas, U251MG and U87MG glioblastomas, CALU-6 lung carcinoma, ASPC-1 pancreatic carcinoma, HT-29 and HCT-116 colon carcinomas, MCF-7 breast carcinomas, and SVR angiosarcomas. Significant antitumor efficacy was observed similarly against orthotopically implanted LNCaP human prostate carcinomas in male nude mice and orthotopically implanted renal carcinoma (RENCA) tumors in BALB/c mice, in terms of a significant reduction in the metastatic score and the extent of pulmonary metastases. These antitumor responses were associated with marked increases in tumor apoptosis, and significant reductions in intratumoral microvessel density (CD34 and Factor VIII staining) of 22-38% relative to controls depending on the specific tumor xenograft. The antitumor efficacy of chronic CEP-7055 administration was independent of initial tumor volume (in the ASPC-1 pancreatic carcinoma model) and reversible on withdrawal of treatment. Chronic p.o. administration of CEP-7055 in preclinical efficacy studies for periods of up to 65 days was well tolerated with no apparent toxicity or significant morbidity. Orally administered CEP-7055 has entered Phase I clinical trials in cancer patients.

Galactosyltransferase associated with tumor in patients with ovarian cancer: factors involved in elevation of serum galactosyltransferase

The serum level of beta1,4-galactosyltransferase (beta1,4-GalT) is increased in both malignancy and benign diseases. Galactosyltransferase associated with tumor (GAT) is one of the soluble forms of beta1,4-GalT, and is a marker of ovarian cancer with a high specificity. GAT and normal soluble beta1,4-GalT are both derived from the same membrane-bound form of the enzyme. This study investigated the mechanism of GAT elevation in patients with ovarian cancer. The serum levels of GAT and normal beta1,4-GalT were measured using specific monoclonal antibodies. In addition, nude mice bearing human ovarian cancer were used to assess the kinetics of tumor-derived enzymes. GAT and normal beta1,4-GalT were both detected in ovarian cancer patients, but only GAT reflected the tumor status. In tumor-bearing nude mice, both soluble forms of beta1,4-GalT were released from tumor cells, but the half-life of GAT was far shorter than that of normal beta1,4-GalT. Addition of serum from healthy women to colostrum (which has a high GAT content) reduced the GAT level, while adding patient serum caused a significantly smaller reduction of GAT. Addition of the serum from mouse which includes no human beta1,4-GalT to colostrum also reduced the GAT level with no significant change of total soluble beta1,4-GalT. These findings indicate that human serum contains certain factors that decrease the GAT level, but these factors are inhibited in ovarian cancer patients so that a high GAT level persists. It seems that the decrease of GAT occurs as a result of conversion into normal beta1,4-GalT.

Direct demonstration of negative regulation of tumor growth and metastasis by host-inducible nitric oxide synthase

Inducible nitric oxide synthase (NOS) II expression can be induced in the tumor bed, predominantly in host cells that infiltrate and surround a tumor. However, the impact of this physiological NOS II expression in host cells on tumor growth and metastasis remains unclear because of a lack of appropriate experimental approaches. In the present study, three NOS II-null (NOS II(-/-)) tumor cell lines, KX-dw1, KX-dw4, and KX-dw7, were established and verified using Southern, Northern, and Western blot analysis, and nitric oxide production assays. Cells from these lines were then s.c. and i.v. injected into NOS II(+/+) and NOS II(-/-) C57BL/6 mice. NOS II protein expression and enzyme activity were clearly detected in the tumors that formed in NOS II(+/+) mice but not in those that formed in NOS II(-/-) mice. Consistent with the absence of NOS II expression in the tumor stroma, KX-dw1, KX-dw4, and KX-dw7 cells grew much faster and produced many more experimental lung metastases in NOS II(-/-) mice than in NOS II(+/+) mice. Therefore, physiological expression of NOS II in host cells directly inhibits tumor growth and metastasis.

PRL-3 and PRL-1 promote cell migration, invasion, and metastasis

We demonstrate here that Chinese hamster ovary cells stably expressing PRL-3, a M(r) 20000 prenylated protein tyrosine phosphatase, or its relative, PRL-1, exhibit enhanced motility and invasive activity. A catalytically inactive PRL-3 mutant has significantly reduced migration-promoting activity. We observe that PRL-3 is associated with diverse membrane structures involved in cell movement. Furthermore, we show that PRL-3- and -1-expressing cells, but not control cells, induce metastatic tumor formation in mice. Thus, our results deliver the first evidence for a causative role of PRL-3 and -1 in promoting cell motility, invasion activity, and metastasis.

Hyaluronidase in sera of tumour-bearing nude mice

Cancer cell lines often secrete hyaluronidase, suggesting that this enzyme could be used as a marker of growing tumours. We have measured hyaluronidase in the sera of non-grafted mice and mice grafted with human tumour-derived hyaluronidase-secreting H460M and SA87 cells or non-secreting CB 193 cells. Mouse serum hyaluronidase was measured at pH 3.8 using the enzyme-linked sorbent assay (ELSA) technique by reference to human serum whose activity at pH 3.8 was determined by the Reissig technique. The serum hyaluronidase in non-grafted mice ranged from 310-520 mU l(-1) (mean+/-SD 432+/-70 mU l(-1), median 440 mU l(-1)). Hyaluronidase increased in the sera of tumour-bearing mice grafted with H460M cells or with SA87 cells, but not in the sera of mice grafted with CB 193 cells. Serum hyaluronidase activity in H460M or SA87 tumour-bearing mice correlated with the tumour mass, increased with time, and decreased after tumour removal. Zymography detected two different hyaluronidase forms in the sera of non-grafted mice: type 1 had only one hyaluronidase band and type 2 had five different bands. In both types, enzyme augmentation in tumour-bearing mice correlated with the presence of an additional enzyme band that was not seen in normal sera and that migrated as the cancer cell enzyme did; there was no augmentation of the normal isoform(s). These results show that serum hyaluronidase can be used to follow the development of tumours in mice grafted with hyaluronidase-secreting cells.

A novel attenuated replication-competent adenovirus for melanoma therapy

To generate a replication-competent adenovirus (Ad) with specificity for melanoma, we constructed a tissue-specific promoter restricting E1A expression to melanoma cells. The combination of four copies of a mouse tyrosinase enhancer element (TE) fused to the human tyrosinase promoter (TP) yielded up to 2000-fold higher luciferase reporter activity in tyrosinase-expressing melanoma cells than in nonmelanoma cells. Insertion of the composite TETP construct upstream of the E1A gene was combined with deleting as far as possible the intertwined endogenous Ad enhancer/promoter (EP). The resulting AdDeltaEP-TETP vector, also deleted for the E3 region, was found to replicate in tyrosinase-positive melanoma cells, such as SK-Mel23 as efficiently as wild-type Ad5, but at a more than 50-fold reduced level in nonmelanoma tumour cells and primary human cells. Injection of AdDeltaEP-TETP into xenotransplanted melanomas, but not into HeLa-derived tumours led to long-lasting tumour regression in nude mice. This AdDeltaEP-TETP virus might be useful for the treatment of accessible lesions in advanced melanoma patients.

Activity of antioxidant enzymes and concentrations of thiobarbituric acid reactive substances (TBARS) in melanotic and amelanotic Bomirski melanoma tissues in the golden hamster (Mesocricetus auratus, Waterhouse)

The activity of superoxide dismutase (SOD) and glutathione peroxidase (GSHPx), as well as the concentration of thiobarbituric acid reactive substances (TBARS) in tissues of transplantable melanoma in the golden hamster were measured and compared. Ten inbred male hamsters were used for the experiment. They were divided into two groups and were given Bomirski melanoma cells subcutaneously. The first group was given melanotic (Ma) melanoma cells. The second group was given amelanotic (Ab) melanoma cells. Thirty days after the transplantation the hamsters were dissected and the tumor tissues were taken and homogenized. A statistically significantly higher activity of the measured antioxidant enzymes was found in homogenates of Ma tumor than in homogenates of the Ab tumor. Activity of SOD is 8% higher in melanotic melanoma, 24% higher in CAT, and 45% higher in GSHPx. Statistically significant differences between TBARS concentrations were not confirmed. The higher activity of antioxidant enzymes in the melanotic tumor is a result of increased generation of oxygen-derived free radicals. It is presumed that it is strictly connected with intensified production of quinone and semiquinone radicals in the process of melanogenesis.

Ischaemia-reperfusion injury in photodynamic therapy-treated mouse tumours

Prompted by the observation of ischaemia development during the treatment of tumours by photodynamic therapy (PDT) that is typically followed by a restoration of tumour blood flow and by the indications of secondary superoxide generation after PDT, we aimed in this study to obtain evidence of the induction of ischaemia-reperfusion (I/R) injury in PDT-treated tumours. Using subcutaneous mouse FsaR fibrosarcoma model and Photofrin-based PDT treatment, we have examined the activity of xanthine oxidase (XO, a key enzyme in the I/R injury development) in tumours before and after the therapy. Compared to the levels in nontreated tumours, there was a five-fold increase in the activity of this enzyme in tumours excised immediately after PDT. This burst of elevated XO activity declined rapidly, returning to the pretreatment levels within the next 30 min. Visible reflectance spectroscopy confirmed the occurrence of a PDT-induced strong but temporary reduction in tumour oxygenation. The administration of XO inhibitor oxypurinol prevented this PDT-induced rise in XO activity. The oxypurinol treatment also decreased the extent of neutrophil accumulation in PDT-treated tumours and reduced the level of PDT-mediated cures. These results demonstrate the induction of I/R injury in PDT-treated tumours, and show that it can contribute to the therapy outcome. Since I/R injury is a well-recognised proinflammatory insult, we suggest that its induction in PDT-treated tumours promotes the development of inflammatory response that has become established as a key element of the antitumour effect of PDT.