Effect of reactive oxygen intermediates on the in vitro invasive capacity of tumor cells and liver metastasis in mice

Molecular hydrogen: a preventive and therapeutic medical gas for various diseases

Since the 2007 discovery that molecular hydrogen (H2) has selective antioxidant properties, multiple studies have shown that H2 has beneficial effects in diverse animal models and human disease. This review discusses H2 biological effects and potential mechanisms of action in various diseases, including metabolic syndrome, organ injury, and cancer; describes effective H2 delivery approaches; and summarizes recent progress toward H2 applications in human medicine. We also discuss remaining questions in H2 therapy, and conclude with an appeal for a greater role for H2 in the prevention and treatment of human ailments that are currently major global health burdens. This review makes a case for supporting hydrogen medicine in human disease prevention and therapy.

Mitochondrial Superoxide Dismutase Has a Protumorigenic Role in Ovarian Clear Cell Carcinoma

Epithelial ovarian cancer (EOC) is the fourth leading cause of death due to cancer in women and comprises distinct histologic subtypes, which vary widely in their genetic profiles and tissues of origin. It is therefore imperative to understand the etiology of these distinct diseases. Ovarian clear cell carcinoma (OCCC), a very aggressive subtype, comprises >10% of EOCs. In the present study, we show that mitochondrial superoxide dismutase (Sod2) is highly expressed in OCCC compared with other EOC subtypes. Sod2 is an antioxidant enzyme that converts highly reactive superoxide (O2 (•-)) to hydrogen peroxide (H2O2) and oxygen (O2), and our data demonstrate that Sod2 is protumorigenic and prometastatic in OCCC. Inhibiting Sod2 expression reduces OCCC ES-2 cell tumor growth and metastasis in a chorioallantoic membrane (CAM) model. Similarly, cell proliferation, migration, spheroid attachment and outgrowth on collagen, and Akt phosphorylation are significantly decreased with reduced expression of Sod2. Mechanistically, we show that Sod2 has a dual function in supporting OCCC tumorigenicity and metastatic spread. First, Sod2 maintains highly functional mitochondria, by scavenging O2 (•-), to support the high metabolic activity of OCCC. Second, Sod2 alters the steady-state ROS balance to drive H2O2-mediated migration. While this higher steady-state H2O2 drives prometastatic behavior, it also presents a doubled-edged sword for OCCC, as it pushed the intracellular H2O2 threshold to enable more rapid killing by exogenous sources of H2O2. Understanding the complex interaction of antioxidants and ROS may provide novel therapeutic strategies to pursue for the treatment of this histologic EOC subtype.

Romo1 and the NF-κB pathway are involved in oxidative stress-induced tumor cell invasion

Reactive oxygen species (ROS) are important contributors to tumor cell invasion. ROS enhanced by reactive oxygen species modulator 1 (Romo1) expression has been reported to increase invasive potential and constitutive activation of nuclear factor-κB (NF-κB) in hepatocellular carcinoma (HCC). Therefore, we investigated whether constitutive NF-κB activation due to Romo1 expression is associated with breast cancer tumor cell invasion. In this study, we show that oxidative stress-induced invasion is mediated by Romo1 expression. The Romo1-induced increase of invasive activity was blocked by an inhibitor of κB kinase (IKK). These results demonstrate that tumor cell invasion in response to oxidative stress is associated with Romo1 expression and the NF-κB signaling pathway. Romo1 is therefore a promising therapeutic target for diseases characterized by NF-κB deregulation.

Fixed dose combination therapy loperamide and niacin ameliorates diethylnitrosamine-induced liver carcinogenesis in albino Wistar rats

Hepatocellular carcinoma (HCC) is among the most lethal cancers (five-year survival rates under 11%), which makes it the third most frequent cause of cancer related deaths in men and sixth in women.

Inhibitory effect of ethanol extract of Ocimum sanctum on osteopontin mediated metastasis of NCI-H460 non-small cell lung cancer cells

Background

Osteopontin (OPN) is one of important molecular targets in cancer progression, metastasis as a calcium-binding, extracellular-matrix-associated protein of the small integrin-binding ligand and, N-linked glycoprotein. In the present study, anti-metastatic mechanism of ethanol extracts of Ocimum sanctum (EEOS) was elucidated on OPN enhanced metastasis in NCI-H460 non- small cell lung cancer cells.

Methods

Cell viability was measured by MTT assay. Adhesion and invasion assays were carried out to see that EEOS inhibited cell adhesion and invasion in OPN treated and non-treated NCI-H 460 cells. RT-PCR was used to determine the mRNA levels of uPA, uPAR, and EGFR.

Results

EEOS significantly inhibited cell adhesion and invasion in OPN treated and non treated NCI-H460 cells, though EEOS did not show any toxicity up to 200 μg/ml. EEOS effectively attenuated the expression of OPN and CD44 and also OPN activated the expression of CD44 in NCI-H460 cells. In addition, EEOS effectively suppressed the expression of phosphatidylinositide 3-kinases (PI3K) and cyclooxygenase 2 (COX-2) and the phosphorylation of Akt at protein level in OPN treated NCI-H460 cells. Also, EEOS significantly attenuated the expression of urokinase plasminogen activator (uPA), its receptor (uPAR) and epidermal growth factor receptor (EGFR) at mRNA level and reduced vascular endothelial growth factor (VEGF) production and MMP-9 activity in OPN treated NCI-H460 cells. Furthermore, PI3K/Akt inhibitor LY294002 enhanced anti-metastatic potential of EEOS to attenuate the expression of uPA and MMP-9 in OPN treated NCI-H 460 cells.

Conclusion

Overall, our findings suggest that anti-metastatic mechanism of EEOS is mediated by inhibition of PI3K/Akt in OPN treated NCI-H460 non-small cell lung cancer cells.

Inhibition of Liver Cancer Cell Proliferation and Migration by a Combination of (-)-Epigallocatechin-3- Gallate and Ascorbic Acid

A mixture of (-)-epigallocatechin-3-gallate (EGCG) and ascorbic acid exhibited 73.2% inhibition of SMMC-7721 cell proliferation in a soft agar colony formation assay, which was much higher than EGCG (40.4%) or ascorbic acid (12.4%) alone. In the cell migration assay, the mixture also significantly suppressed the migration of SMMC-7721 cells by 65.9% while EGCG and/or ascorbic acid did by 28.9% and 18.7%, respectively. Ascorbic acid was able to enhance the antioxidant activity of EGCG by decreasing the intracellular oxidative stress according to fluorographic analysis of oxidative stress. In conclusion, the combination of EGCG and ascorbic acid can strongly suppress the proliferation and metastasis of liver cancer cells, possibly with a mechanism associated with the scavenging of reactive oxygen species. All these events add to our knowledge of liver cancer chemotherapy.

Regulating surgical oncotaxis to improve the outcomes in cancer patients

Excessive surgical stress and postoperative complications cause a storm of perioperative cytokine release, which has been shown to enhance tumor metastasis in experimental models. We have named this phenomenon "surgical oncotaxis". The mechanisms that underpin this process are thought to be excessive corticosteroid secretion, coagulopathy in the peripheral vasculature, immune suppression and excessive production of reactive oxygen species. Nuclear factor-kappa B (NFkB) activation plays a key role in these mechanisms. Minimally invasive surgical techniques should be used, and postoperative complications should be avoided whenever possible to lessen the impact of surgical oncotaxis. Furthermore, there may be a role for a small preoperative dose of corticosteroid or the use of free radical scavengers in the perioperative period. Recently, there has been a great deal of interest in omega-3 fatty acid, because it regulates NFkB activation. The use of multimodal treatments that regulate surgical oncotaxis may be as important as chemotherapy for determining the outcome of patients with cancer undergoing surgery.

Are there new therapeutic options for treating lung cancer based on herbal medicines and their metabolites?

ETHONOPHARMACOLOGICAL RELEVANCE: Lung cancer is one of the most lethal cancers in terms of mortality and incidence worldwide. Despite intensive research and investigation, treatment of lung cancer is still unsatisfactory due to adverse effects and multidrug resistance. Recently, herbal drugs have been recognized as one of attractive approaches for lung cancer therapy with little side effects. Furthermore, there are evidences that various herbal medicines have proven to be useful and effective in sensitizing conventional agents, prolonging survival time, preventing side effects of chemotherapy, and improving quality of life (QoL) in lung cancer patients.

AIM AND METHODS OF THE STUDY

Nevertheless, the underlying molecular targets and efficacy of herbal medicines in lung cancer treatment still remain unclear. Thus, we reviewed traditionally used herbal medicines and their phytochemicals with antitumor activity against lung cancer from peer-reviewed papers through Scientific Database Medline, Scopus and Google scholar.

CONCLUSIONS

We suggest that herbal medicines and phytochemicals can be useful anti-cancer agents for lung cancer treatment by targeting molecular signaling involved in the regulation of angiogenesis, metastasis and severe side effects, only provided quality control and reproducibility issues were solved.

Inhibitory effect of ascorbic Acid on the proliferation and invasion of hepatoma cells in culture

Effect of ascorbic acid (AsA) on the proliferation and invasion of rat ascites hepatoma AH109A cells was investigated by measuring [(3)H]thymidine incorporation into acid-insoluble fraction of the cells and by co-culturing the hepatoma cells with rat mesentery-derived mesothelial cells, respectively. AsA suppressed the invasion of AH109A cells in a dose-dependent manner at concentrations of 62.5-500 muM, while it inhibited the proliferation of the cells at higher concentrations of 250 and 500 muM. Hepatoma cells previously cultured with hypoxanthine (HX) and xanthine oxidase (XO) or with hydrogen peroxide showed increased invasive activities. AsA suppressed the reactive oxygen species-potentiated invasive capacity by simultaneously treating AH109A cells with AsA, HX and XO or with AsA and hydrogen peroxide. Furthermore, AsA reduced the intracellular peroxide levels in AH109A cells. These results suggest that the antioxidative property of AsA may be involved in its anti-invasive action on hepatoma cells.

Anethole exerts antimetatstaic activity via inhibition of matrix metalloproteinase 2/9 and AKT/mitogen-activated kinase/nuclear factor kappa B signaling pathways

Anethole is known to possess anti-inflammatory and anti-tumor activities and to be a main constituent of fennel, anise, and camphor. In the present study, we evaluated anti-metastatic and apoptotic effects of anethole on highly-metastatic HT-1080 human fibrosarcoma tumor cells. Despite weak cytotoxicity against HT-1080 cells, anethole inhibited the adhesion to Matrigel and invasion of HT-1080 cells in a dose-dependent manner. Anethole was also able to down-regulate the expression of matrix metalloproteinase (MMP)-2 and -9 and up-regulate the gene expression of tissue inhibitor of metalloproteinase (TIMP)-1. The similar inhibitory effect of anethole on MMP-2 and -9 activities was confirmed by zymography assay. Furthermore, anethole significantly decreased mRNA expression of urokinase plasminogen activator (uPA), but not uPA receptor (uPAR). In addition, anethole suppressed the phosphorylation of AKT, extracellular signal-regulated kinase (ERK), p38 and nuclear transcription factor kappa B (NF-κB) in HT-1080 cells. Taken together, our findings indicate that anethole is a potent anti-metastatic drug that functions through inhibiting MMP-2/9 and AKT/mitogen-activated protein kinase (MAPK)/NF-κB signal transducers.

Anti-invasive activity of α-tocopherol against hepatoma cells in culture via protein kinase C inhibition

Effects of α-, β-, γ- and δ-tocopherols on the proliferation and invasion of AH109A hepatoma cells and their modes of action were investigated. Four tocopherols inhibited the invasion as well as the proliferation of AH109A cells. Their inhibitory effects were more prominent on the invasion than on the proliferation. At 1 µM, α-tocopherol showed most potent anti-invasive activity without any influence on the proliferation. We have previously demonstrated that reactive oxygen species increase the invasion of AH109A cells. α-Tocopherol suppressed the reactive oxygen species-induced invasion but failed to suppress the reactive oxygen species-induced rises in intracellular peroxide level. GF 109203X, a protein kinase C inhibitor, decreased the invasive activity of AH109A cells. In contrast, phorbol-12-myristate-13-acetate, a protein kinase C activator, increased the invasive capacity of AH109A cells. α-Tocopherol suppressed the phorbol-12-myristate-13-acetate-induced increase in the invasion, and canceled the phorbol-12-myristate-13-acetate-induced rises in protein kinase C activity and phosphorylation of extracellular signal-regulated kinase. These results suggest that tocopherols, especially α-tocopherol, possess inhibitory effect more strongly on the invasion of AH109A cells than on the proliferation. They also suggest that the anti-invasive activity of α-tocopherol is raised through suppression of PKC/ERK signaling.

Recent advances in hydrogen research as a therapeutic medical gas

Recent basic and clinical research has revealed that hydrogen is an important physiological regulatory factor with antioxidant, anti-inflammatory and anti-apoptotic protective effects on cells and organs. Therapeutic hydrogen has been applied by different delivery methods including straightforward inhalation, drinking hydrogen dissolved in water and injection with hydrogen-saturated saline. This review summarizes currently available data regarding the protective role of hydrogen, provides an outline of recent advances in research on the use of hydrogen as a therapeutic medical gas in diverse models of disease and discusses the feasibility of hydrogen as a therapeutic strategy. It is not an overstatement to say that hydrogen's impact on therapeutic and preventive medicine could be enormous in the future.

Anti-invasion effect of rosmarinic acid via the extracellular signal-regulated kinase and oxidation-reduction pathway in Ls174-T cells

Rosmarinic acid is a major phenylpropanoid isolated from Prunella vulgaris L., which is a composition of herbal tea for centuries in China. However, the anti-invasion activity on Ls174-T human colon carcinoma cells has not been studied. In this study, we investigated the anti-metastasis functions according to wound healing assay, adhesion assay, and Transwell assay and found that rosmarinic acid could inhibit migration, adhesion, and invasion dose-dependently. Rosmarinic acid also could decrease the level of reactive oxygen species by enhancing the level of reduced glutathione hormone. In addition, rosmarinic acid repressed the activity and expression of matrix metalloproteinase-2,9. According to Western blot and quantitative real-time PCR assay, rosmarinic acid may inhibit metastasis from colorectal carcinoma mainly via the pathway of extracellular signal-regulated kinase. In animal experiment, intraperitoneal administration of 2 mg of rosmarinic acid reduced weight of tumors and the number of lung nodules significantly compared with those of control group. Therefore, these results demonstrated that rosmarinic acid can effectively inhibit tumor metastasis in vitro and in vivo.

Redox metabolism and malignancy

Redox balance underlies cellular homeostasis. Cancer initiation and progression has been linked to the disruption of redox balance and oxidative stress. Recent findings exemplify the distinctive roles of intracellular and extracellular redox state in the etiology and maintenance of oxidative stress associated with malignancy and metastasis. Within these compartments, redox sensitive cysteines play a crucial role in regulating cell signaling events that act to promote the malignant phenotype via the activation of survival pathways, disruption of cell-death signaling, and increases in cell proliferation. New approaches that aim to accurately evaluate subcellular and microenvironment redox potential may be useful in developing cancer diagnostics and therapeutics.

Ethanol extract of Ocimum sanctum exerts anti-metastatic activity through inactivation of matrix metalloproteinase-9 and enhancement of anti-oxidant enzymes

Ocimum sanctum has been known to possess various beneficial properties including anti-oxidative, anti-inflammatory and anti-cancer activities. In the present study, we investigated that ethanol extracts of O. sanctum (EEOS) had anti-metastatic activity through activation of anti-oxidative enzymes. EEOS exerted cytotoxicity against Lewis lung carcinoma (LLC) cells. Also, EEOS significantly inhibited cell adhesion and invasion as well as activities of matrix metalloproteinase-9 (MMP-9), but not MMP-2, indicating the important role of MMP-9 in anti-metastatic regulation of EEOS. In addition, EEOS significantly reduced the tumor nodule formation and lung weight in LLC-injected mice. Inhibitory effect of EEOS on metastasis was further confirmed by using hematoxylin and eosin (H&E) staining. Notably, we also found that EEOS enhanced activities of anti-oxidative enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in a concentration-dependent manner. Taken together, our findings support that EEOS can be a potent anti-metastatic candidate through inactivation of MMP-9 and enhancement of anti-oxidant enzymes.

Reactive oxygen species regulate a slingshot-cofilin activation pathway

Cellular stimuli generate reactive oxygen species (ROS) via the local action of NADPH oxidases (Nox) to modulate cytoskeletal organization and cell migration through unknown mechanisms. Cofilin is a major regulator of cellular actin dynamics whose activity is controlled by phosphorylation/dephosphorylation at Ser3. Here we show that Slingshot-1L (SSH-1L), a selective cofilin regulatory phosphatase, is involved in H(2)O(2)-induced cofilin dephosphorylation and activation. SSH-1L is activated by its release from a regulatory complex with 14-3-3zeta protein through the redox-mediated oxidation of 14-3-3zeta by H(2)O(2). The ROS-dependent activation of the SSH-1L-cofilin pathway stimulates the SSH-1L-dependent formation of cofilin-actin rods in cofilin-GFP-expressing HeLa cells. Similarly, the formation of endogenous ROS stimulated by angiotensin II (AngII) also activates the SSH-1L-cofilin pathway via oxidation of 14-3-3zeta to increase AngII-induced membrane ruffling and cell motility. These results suggest that the formation of ROS by NADPH oxidases engages a SSH-1L-cofilin pathway to regulate cytoskeletal organization and cell migration.

Oral administration of a catalase-producing Lactococcus lactis can prevent a chemically induced colon cancer in mice

Reactive oxygen species, such as hydrogen peroxide (H2O2), are involved in various aspects of tumour development. Decreasing their levels can therefore be a promising approach for colon cancer prevention. The objective of this study was to evaluate the effect of catalase-producing Lactococcus lactis on the prevention of an experimental murine 1,2-dimethylhydrazine (DMH)-induced colon cancer. DMH-treated BALB/c mice received either a catalase-producing L. lactis strain or the isogenic non-catalase-producing strain as a control, whereas other untreated mice did not receive bacterial supplementation. Catalase activity and H2O2 levels in intestinal fluids and blood samples were measured, and changes in the histology of the large intestines during tumour progression were evaluated. The catalase-producing L. lactis strain used in this study was able to slightly increase catalase activities in DMH-treated mice (1.19+/-0.08 U ml(-1)) and reduce H2O2 levels (3.4+/-1.1 microM) compared to (i) animals that received the non-catalase-producing strain (1.00+/-0.09 U ml(-1), 9.0+/-0.8 microM), and (ii) those that did not receive bacterial supplementation (1.06+/-0.07 U ml(-1), 10.0+/-1.1 microM). Using the histopathological grading scale of chemically induced colorectal cancer, animals that received the catalase-producing L. lactis had a significantly lesser extent of colonic damage and inflammation (2.0+/-0.4) compared to animals that received the non-catalase-producing L. lactis (4.0+/-0.3) or those that did not receive bacterial supplementation (4.7+/-0.5). The catalase-producing L. lactis strain used in this study was able to prevent tumour appearance in an experimental DMH-induced colon cancer model.

Inhibitory effects of olive oil phenolics on invasion in human colon adenocarcinoma cells in vitro

Studies in human, animal and cellular systems suggest that phenols from virgin olive oil are capable of inhibiting several stages in carcinogenesis, including metastasis. The invasion cascade comprises cell attachment to extracellular matrix components or basement membrane, degradation of basement membrane by proteolytic enzymes and migration of cells through the modified matrix. In the present study, we investigated the effect of phenolics extracted from virgin olive oil (OVP) and its main constituents: hydroxytyrosol (3,4-dihydroxyphenylethanol), tyrosol (p-hydroxyphenylethanol), pinoresinol and caffeic acid. The effects of these phenolics were tested on the invasion of HT115 human colon carcinoma cells in a Matrigel invasion assay. OVP and its compounds showed different dose-related anti-invasive effects. At 25 microg/ml OVP and equivalent doses of individual compounds, significant anti-invasive effects were seen in the range of 45-55% of control. Importantly, OVP, but not the isolated phenolics, significantly reduced total cell number in the Matrigel invasion assay. There were no significant effects shown on cell viability, indicating the reduction of cell number in the Matrigel invasion assay was not due to cytotoxicity. There were also no significant effects on cell attachment to plastic substrate, indicating the importance of extracellular matrix in modulating the anti-invasive effects of OVP. In conclusion, the results from this study indicate that phenols from virgin olive oil have the ability to inhibit invasion of colon cancer cells and the effects may be mediated at different levels of the invasion cascade.

Nox1 expression determines cellular reactive oxygen and modulates c-fos-induced growth factor, interleukin-8, and Cav-1

Increased cellular reactive oxygen species (ROS) can act as mitogenic signals in addition to damaging DNA and oxidizing lipids and proteins, implicating ROS in cancer development and progression. To analyze the effects of Nox1 expression and its relation to cellular ROS and signal transduction involved in cellular proliferation, Nox1RNAi constructs were transfected into DU145 prostate cancer cells overexpressing Nox1, causing decreased Nox1 message and protein levels in the Nox1RNAi cell lines. Increased ROS and tumor growth in the Nox1-overexpressing DU145 cells were reversed in the presence of the Nox1RNAi. Analysis and comparison of the message levels in the overexpression and RNAi cells demonstrated that Nox1 overexpression leads to changes in message levels of a variety of proteins including c-fos-induced growth factor, interleukin-8, and Cav-1. Finally, we found that Nox1 protein overexpression is an early event in the development of prostate cancer using a National Cancer Institute prostate cancer tissue microarray (CPCTR). Tumor (86%) was significantly more likely to have Nox1 staining than benign prostate tissue (62%) (P = 0.0001). These studies indicate that Nox1 overexpression may function as a reversible signal for cellular proliferation with relevance for a common human tumor.

Manganese superoxide dismutase enhances the invasive and migratory activity of tumor cells

Clinically significant elevations in the expression of manganese superoxide dismutase (Sod2) are associated with an increased frequency of tumor invasion and metastasis in certain cancers. The aim of this study was to examine whether increases in Sod2 activity modulate the migratory potential of tumor cells, contributing to their enhanced metastatic behavior. Overexpression of Sod2 in HT-1080 fibrosarcoma cells significantly enhanced their migration 2-fold in a wound healing assay and their invasive potential 3-fold in a transwell invasion assay. Severity of invasion was directly correlated to Sod2 expression levels and this invasive phenotype was similarly observed in 253J bladder tumor cells, in which Sod expression resulted in a 3-fold increase in invasion compared with controls. Further, migration and invasion of the Sod2-expressing cells was inhibited following overexpression of catalase, indicating that the promigratory/invasive phenotype of Sod2-expressing cells is H(2)O(2) dependent. Sod2 overexpression was associated with a loss of vinculin-positive focal adhesions that were recovered in cells coexpressing catalase. Tail vein injections of Sod2-GFP-expressing HT-1080 cells in NCR nude mice led to the development of pulmonary metastatic nodules displaying high Sod2-GFP expression. Isolated tumors were shown to retain high Sod2 activity in culture and elevated levels of the matrix degrading protein matrix metalloproteinase-1, and a promigratory phenotype was observed in a population of cells growing out from the tumor nodule. These findings suggest that the association between increased Sod2 activity and poor prognosis in cancer can be attributed to alterations in their migratory and invasive capacity.

Application of in vivo ESR/spin-probe technique to monitor tumor in vivo in mouse footpad

The redox status of tumors inoculated into the footpads of mice was investigated by using an in vivo ESR/spin-probe technique. A single-cell suspension of a metastatic subclone of colon carcinoma NL-17 was inoculated into the footpads of Balb/c mice. At 12, 24, 48, and 96 h after the inoculation, a spin probe, either carbamoylor carboxy-PROXYL, was intravenously injected, and then the ESR spectra of each footpad were separately obtained under a one-dimensional magnetic-field gradient. The change in the ESR signal intensity of the spin probe was closely related to the tumor volume in the footpads, but no significant difference was observed between carbamoyl- and carboxy-PROXYL. The in vivo ESR signal decay of carbamoyl-PROXYL, which is related to the conversion of the nitroxyl radical to hydroxylamine, was enhanced in the inoculated footpads but not in the reference one. The ESR signal decay was not influenced by coadministration of radical scavengers, SOD, catalase, mannitol, or dimethylthiourea, suggesting that the redox status but not reactive oxygen species generation played a role in the enhanced signal decay.

Activation of FOXO3a by the green tea polyphenol epigallocatechin-3-gallate induces estrogen receptor alpha expression reversing invasive phenotype of breast cancer cells

Previously, we showed that the bioactive green tea polyphenol epigallocatechin-3-gallate (EGCG) inhibits growth in soft agar of breast cancer cells with Her-2/neu overexpression. Using gene expression profiling, here we show that EGCG treatment of Her-2/neu-driven mammary tumor cells alters the expression of key regulators in the epithelial to mesenchymal transition (EMT) pathway, reducing invasive phenotype. Specifically, the epithelial genes E-cadherin, gamma-catenin, MTA3, and estrogen receptor alpha (ERalpha) were up-regulated by EGCG, whereas the proinvasive snail gene was down-regulated. Consistently, EGCG inhibited branching colony growth and invasion in Matrigel. EGCG treatment similarly inhibited invasive phenotype of mouse mammary tumor cells driven by Nuclear Factor-kappaB c-Rel and protein kinase CK2, frequently found overexpressed in human breast disease. Recently, we identified the Forkhead box O transcription factor FOXO3a as a major transcriptional regulator of ERalpha. Given the pivotal role of ERalpha in preventing EMT, we hypothesized that the activation of FOXO3a by EGCG plays an important role in the observed reversal of invasive phenotype in ERalpha-positive breast cancer cells. EGCG treatment activated FOXO3a. Ectopic expression of a constitutively active FOXO3a overrode transforming growth factor-beta1-mediated invasive phenotype and induced a more epithelial phenotype, which was dependent on ERalpha expression and signaling. Conversely, a dominant negative FOXO3a reduced epithelial phenotype of ERalpha-low breast cancer cells. These results identify, for the first time, a role for FOXO3a in the inhibition of invasive phenotype in breast cancer cells with active ERalpha signaling and elucidate a novel mechanism whereby EGCG represses EMT of breast cancer cells.

Inhibition of tumour metastasis by targeted delivery of antioxidant enzymes

Metastasis is one of the most harmful aspects of malignant neoplasm. Interaction of tumour cells with normal cells such as tissue macrophages may generate reactive oxygen species, which would affect various aspects of tumour metastasis. Reactive oxygen species cause damage to both tumour and normal cells and some of them, especially hydrogen peroxide, can also act as intracellular second messengers at sublethal concentrations to increase the transcription of various genes, which can then accelerate the proliferation of tumour cells in metastatic colonies. Therefore, eliminating hydrogen peroxide is one approach to inhibiting tumour metastasis. In this article, the roles of reactive oxygen species in tumour metastasis are reviewed, and the strategies to inhibit tumour metastasis by the targeted delivery of catalase, an enzyme that detoxifies hydrogen peroxide, are discussed.

Antimetastatic effect of a lipophilic ascorbic acid derivative with antioxidation through inhibition of tumor invasion

PURPOSE

Ascorbic acid (AA), the natural antioxidant, has been demonstrated to exert an antimetastatic action; however, AA is quite unstable in physiological condition. The aim of the present study is to investigate the stability, the antioxidation and the antimetastatic effects of three lipophilic AA derivatives in vitro as well as in vivo.

METHODS

The 95D cells were treated with ascorbic acid-2-O-phosphate-6-O-laureate (AA2P6L), ascorbic acid-2-O-phosphate-6-O-myristate (AA2P6M) and ascorbic acid-2-O-phosphate-6-O-stearate (AA2P6S). AA derivatives' stability in medium under cell culture condition, in the presence and in the absence of 95D cells, was assessed by high-performance liquid chromatography assay. Cell viability and intracellular oxidative stress were measured by MTT assay and CDCFH assay, respectively. Wound healing assay and cell adhesion assay were used to investigate the antimetastatic activities against 95D cells in vitro, and the C57BL/6 mice model was used to evaluate the antimetastatic action in vivo.

RESULTS

All the three AA derivatives exhibited excellent stability, significantly different from AA. Results of MTT assay showed that IC(50) values of the cytotoxicity of those AA derivatives, namely AA2P6L, AA2P6M and AA2P6S, were 38.46, 28 and 22.97 microg/ml, while the CDCFH assay indicated that EC(50) values of antioxidant effects on 95D cells were 31.12, 33.51 and 38.31 microg/ml, respectively. Through the ratio of IC(50) vs EC(50) for AA derivatives, AA2P6L was demonstrated to be the most effective AA derivative, which retained the antioxidant ability as well as low cytotoxicity. AA2P6L dose-dependently inhibited 95D cells' migration and adhesion, by 50% at the concentration of 20 and 57 microg/ml, respectively. In the animal experiment, intraperitoneal administration of 75 mg/kg AA2P6L decreased the number of metastatic nodules by 62% and elevated the survival rate of C57BL/6 mice about onefold compared to the control group.

CONCLUSION

AA2P6L, a lipophilic AA derivative with antioxidation, is shown to be a potent antimetastatic agent through the inhibition of tumor invasion. These results support future investigations on the feasibility of cancer chemotherapy with AA2P6L.

Repressions of MMP-9 expression and NF-kappa B localization are involved in inhibition of lung carcinoma 95-D cell invasion by (-)-epigallocatechin-3-gallate

Epigallocatechin-3-gallate (EGCG) repressed the invasion of lung carcinoma 95-D cells in invasion assay. RT-PCR analysis illuminated that 40 microM EGCG down-regulated the expression of MMP-9 by 45.7% and the result of Western blot analysis provided further evidence. NF-kappa B localized in the nucleus of the 95-D cells was diminished in a dose-dependent manner in EGCG-treated cells as shown by Western blot. Intracellular oxidants were more abundant in invasive cells than in invasion-suppressed cells fed with EGCG for 18 h. Thus, the inhibition of tumor invasion by EGCG was shown to be attributed to decreases of the expression of MMP-9 and NF-kappa B, which may result from decrease of intracellular oxidants.

Antiangiogenic activity of 4-O-methylgallic acid from Canavalia gladiata, a dietary legume

Development of nontoxic and biologically safe antiangiogenic agent has been highlighted as a promising way to treat angiogenesis related diseases including cancer. Herein, we isolated 4-O-methylgallic acid (4-OMGA) from the seed of Canavalia gladiata, a dietary legume, on the basis of the growth inhibitory activity for bovine aortic endothelial cells (BAECs). The compound potently inhibits endothelial cell invasion and tube formation stimulated with basic fibroblast growth factor (bFGF) at low micromolar concentrations where it shows no cytotoxicity to the cells. In addition, 4-OMGA inhibits vascular endothelial cell growth factor (VEGF) production under hypoxic condition and the production of reactive oxygen species (ROS) in the endothelial cells stimulated with VEGF. These results demonstrate that 4-OMGA is a compound having potential for an antiangiogenic agent.

Development of cell-specific targeting systems for drugs and genes

Cell-specific targeting systems for drugs and genes have been developed by using glycosylated macromolecule as a vehicle that can be selectively recognized by carbohydrate receptors. Pharmacokinetic analyses of the tissue distribution of glycosylated proteins came to the conclusion that the surface density of the sugar moiety on the protein derivative largely determines the binding affinity for the receptors and plasma lectin. Many glycosylated delivery systems have been developed and their usefulness investigated in various settings. Galactosylated polymers, when properly designed, were found to be effective in delivering prostaglandin E1 and other low-molecular-weight drugs selectively to hepatocytes. In addition, glycosylated superoxide dismutase and catalase were successfully developed with minimal loss of enzymatic activity. A simultaneous targeting of these two enzymes to liver nonparenchymal cells significantly prevented hepatic ischemia/reperfusion injury. On the other hand, galactosylated catalase, a derivative selectively delivered to hepatocytes, effectively inhibited hepatic metastasis of colon carcinoma cells in mice. Finally, hepatocyte-targeted in vivo gene transfer was achieved by synthesizing a multi-functional carrier molecule, which condenses plasmid DNA, delivering DNA to hepatocytes through recognition by asialoglycoprotein receptors, and releasing DNA from endosomes/lysosomes into cytoplasm.

Inhibition of experimental hepatic metastasis by targeted delivery of catalase in mice

Bovine liver catalase derivatives possessing diverse tissue distribution properties were synthesized, and their effects on hepatic metastasis of colon carcinoma cells were examined in mice. An intraportal injection of 1 x 10(5) colon 26 cells resulted in the formation of more than 50 metastatic colonies on the surface of the liver at 14 days after injection. An intravenous injection of catalase (CAT; 35000 units/kg of body weight) significantly (P < 0.001) reduced the number of the colonies in the liver. Galactosylated (Gal-), mannosylated (Man-) and succinylated (Suc-) CAT were also tested in the same system. Of these derivatives, Gal-CAT showed the greatest inhibitory effect on hepatic metastasis, and the number of colonies was significantly (P < 0.001) smaller than following treatment with catalase. High activities of matrix metalloproteinases (MMPs), especially MMP-9, were detected in the liver of mice bearing metastatic tumor tissues, which was significantly (P < 0.05) reduced by Gal-CAT. These results, combined with our previous finding that Gal-CAT can be efficiently delivered to hepatocytes, indicate that the targeted delivery of catalase to the liver by galactosylation is a promising approach to suppress hepatic metastasis. Decreased MMP activity by catalase delivery seems to be involved in its anti-metastatic effect.

Superoxide dismutases in malignant cells and human tumors

Reactive oxygen metabolites have multifactorial effects on the regulation of cell growth and the capacity of malignant cells to invade. Overexpression of the superoxide dismutases (SODs) in vitro increases cell differentiation, decreases cell growth and proliferation, and can reverse a malignant phenotype to a nonmalignant one. The situation in vivo is more complex due to multiple interactions of tumor cells with their environment. Numerous in vivo studies show that the superoxide dismutases can be highly expressed in aggressive human solid tumors. Furthermore, high SOD has occasionally been associated with a poor prognosis and with resistance to cytotoxic drugs and radiation. Most of the apparent conflicts between the above in vitro and in vivo observations can be reconciled by considering the net redox status of tumor cells in different environments. Administering high concentrations of SOD to cells in vitro is usually associated with a non- or less malignant phenotype, whereas secondary induction of SOD in tumors in vivo can be associated with an aggressive malignant transformation probably due to the altered (oxidative) redox state in the malignant cells. This concept suggests that for many types of tumors antioxidants could be used to diminish the invasive capability of malignant cells.

Reactive oxygen species and induction of lignin peroxidase in Phanerochaete chrysosporium

We studied oxidative stress in lignin peroxidase (LIP)-producing cultures (cultures flushed with pure O(2)) of Phanerochaete chrysosporium by comparing levels of reactive oxygen species (ROS), cumulative oxidative damage, and antioxidant enzymes with those found in non-LIP-producing cultures (cultures grown with free exchange of atmospheric air [control cultures]). A significant increase in the intracellular peroxide concentration and the degree of oxidative damage to macromolecules, e.g., DNA, lipids, and proteins, was observed when the fungus was exposed to pure O(2) gas. The specific activities of manganese superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase and the consumption of glutathione were all higher in cultures exposed to pure O(2) (oxygenated cultures) than in cultures grown with atmospheric air. Significantly higher gene expression of the LIP-H2 isozyme occurred in the oxygenated cultures. A hydroxyl radical scavenger, dimethyl sulfoxide (50 mM), added to the culture every 12 h, completely abolished LIP expression at the mRNA and protein levels. This effect was confirmed by in situ generation of hydroxyl radicals via the Fenton reaction, which significantly enhanced LIP expression. The level of intracellular cyclic AMP (cAMP) was correlated with the starvation conditions regardless of the oxygenation regimen applied, and similar cAMP levels were obtained at high O(2) concentrations and in cultures grown with atmospheric air. These results suggest that even though cAMP is a prerequisite for LIP expression, high levels of ROS, preferentially hydroxyl radicals, are required to trigger LIP synthesis. Thus, the induction of LIP expression by O(2) is at least partially mediated by the intracellular ROS.

The metastasis suppressor gene C33/CD82/KAI1 induces apoptosis through reactive oxygen intermediates

Here we describe the isolation of C33/CD82/KAI1 in a screen for apoptosis-inducing genes. C33 is a gene that is downregulated in many metastatic tumor cells and the expression of which can attenuate the process of metastases formation in a variety of tumors. In accordance, we observed cell death induction by C33 in many different cell types. C33 seems to promote cell death by the generation of reactive oxygen intermediates (ROIs). These ROIs, however, are not derived from the mitochondrial respiratory chain as in most other scenarios leading to apoptosis. We observed that C33 renders cells sensitive to ROIs by causing the specific release of the intracellular antioxidant glutathione (GSH) from cells. Moreover, C33 activates the GTPase Cdc42, which mediates GSH release and apoptosis induction and allows to detect the formation of ROIs.

Potentiation of invasive activity of hepatoma cells by reactive oxygen species is mediated by autocrine/paracrine loop of hepatocyte growth factor

We have already reported that reactive oxygen species (ROS) promote rat ascites hepatoma cell invasion beneath mesentery-derived mesothelial cell monolayer. To investigate the mechanism for this, we examined the involvement of motility factors, particularly hepatocyte growth factor (HGF). Rat ascites hepatoma cell line of AH109A expressed HGF and c-Met mRNAs. Treatment with ROS augmented amounts of HGF mRNA in AH109A and HGF concentration in the medium. ROS also induced HGF gene expression in mesothelial cells. Exogenously added HGF enhanced invasive activity of AH109A cells, but exerted no effect on proliferation. AH109A cells pretreated with ROS showed an increased invasive activity, which was cancelled by simultaneous pretreatment with anti-HGF antibody. These results suggest that the invasive activity of AH109A is mediated by the autocrine and paracrine pathways of HGF, and ROS potentiate invasive activity by inducing gene expression of HGF in AH109A and mesothelial cells.

Suppressive effect of Shichimotsu-koka-to (Kampo medicine) on pulmonary metastasis of B16 melanoma cells

Shichimotsu-koka-to (SKT) is a Kampo (traditional Japanese herbal) medicine, which is used in Japan to treat hypertension and atherosclerosis. We investigated the inhibitory effect of SKT on experimental pulmonary metastasis of B16 melanoma cells. The intake of SKT at a dose of 430 mg/kg for 6 weeks from 2 weeks before tumor inoculation significantly reduced the number of metastatic surface nodules in the lung and extended the life span. When the duration of SKT intake was examined, survival time was not affected by preintake before B16 melanoma cell inoculation and was slightly extended by postintake after B16 melanoma cell inoculation, although the life span was prolonged by intake throughout the experiment. To address the mechanism underlying the antimetastatic effect of SKT, we studied whether SKT modulated macrophage function, which is involved in killing tumor cells. The intake of SKT for 6 weeks dose dependently increased nitric oxide (NO) production by macrophages following stimulation with lipopolysaccharide. The elevated NO was found to serve as a cytotoxic mediator against B16 melanoma cells in co-culture with macrophages. On the contrary, B16 melanoma-conditioned medium reduced NO production by macrophages. However, SKT treatment reversed the reduction in NO production by the conditioned medium significantly. These findings may suggest that macrophage function-modulating activity by SKT appears to underlie its antimetastatic activity, which leads to a decrease in the number of lung metastatic surface nodules and the extension of life span.

Genistein, a soy isoflavone, induces glutathione peroxidase in the human prostate cancer cell lines LNCaP and PC-3

Genistein is a major component of soybean isoflavone and has multiple functions resulting in antitumor effects. Prostate cancer is 1 of the targets for the preventive role of genistein. We examined the effect of genistein on human prostate cancer (LNCaP and PC-3) cells. Proliferation of both cell lines was inhibited by genistein treatment in a dose-dependent manner. To obtain the gene expression profile of genistein in LNCaP cells, we performed cDNA microarray analysis. The expression of many genes, including apoptosis inhibitor (survivin), DNA topoisomerase II, cell division cycle 6 (CDC6) and mitogen-activated protein kinase 6 (MAPK 6), was downregulated. Expression levels were increased more than 2-fold in only 4 genes. The glutathione peroxidase (GPx)-1 gene expression level was the most upregulated. Quantitative real-time polymerase chain reaction revealed significant elevation of transcript levels of GPx-1 in both LNCaP and PC-3 cells. Upregulation of gene expression levels accompanied elevation of GPx enzyme activities. In contrast, no significant changes were observed in the gene expression levels and enzyme activities of the other antioxidant enzymes, superoxide dismutase and catalase. GPx activation might be one of the important characteristics of the effects of genistein on prostate cancer cells.

Inhibition of experimental pulmonary metastasis by controlling biodistribution of catalase in mice

In a previous study, we showed that targeted delivery of bovine liver catalase to hepatocytes by direct galactosylation augmented the inhibitory effect of the enzyme on experimental hepatic metastasis of colon carcinoma cells (unpublished data). Here, we examined the ability of catalase to inhibit tumor metastasis to the lung by controlling its biodistribution. Four types of catalase derivative, Gal-CAT, Man-CAT, Suc-CAT and PEG-CAT, were synthesized. Experimental pulmonary metastasis was induced in mice by i.v. injection of 1 x 10(5) colon 26 tumor cells. An i.v. injection of catalase (35,000 units/kg) partially, but significantly, decreased the number of colonies in the lung 2 weeks after tumor injection, from 93 +/- 29 (saline injection) to 63 +/- 23 (p < 0.01). Suc-CAT, Man-CAT and Gal-CAT showed effects similar to those of catalase on the number of colonies. However, PEG-CAT greatly inhibited pulmonary metastasis to 22 +/- 11 (p < 0.001). Furthermore, s.c. injection of catalase also greatly inhibited metastasis (11 +/- 6, p < 0.001). Neither inactivated catalase nor BSA showed any effects on the number of metastatic colonies, indicating that the enzymatic activity of catalase to detoxify H(2)O(2) is the critical factor inhibiting metastasis. (111)In-PEG-CAT showed a sustained concentration in plasma, whereas s.c.-injected (111)In-catalase was slowly absorbed from the injection site. These results suggest that retention of catalase activity in the circulation is a promising approach to inhibit pulmonary metastasis.

Antimetastatic activity of acteoside, a phenylethanoid glycoside

We examined the antimetastatic effect of acteoside, a phenylethanoid glycoside widely distributed in the plant kingdom, on lung metastasis using a mouse model injected with B16 melanoma cells intravenously. Male C57BL/6 mice were injected intravenously with 2 x 10(5) of B16 melanoma cells, while acteoside at a dose of 50 mg/kg was administered intraperitoneally every other day from 13 d before B16 melanoma cell injection until all mice had succumbed to the metastatic tumor burden in the lung. Administration of acteoside prolonged survival time significantly and the average survival time was 63.3 +/- 3.4d compared with 52.1 +/- 2.5d in control mice. This result suggests that acteoside showed suppressive effect on lung metastasis of B16 melanoma cells.

Inhibition of tumour invasion and angiogenesis by epigallocatechin gallate (EGCG), a major component of green tea

Epidemiological studies have suggested that consumption of green tea may decrease cancer risk. In addition, abundant pre-clinical data from several laboratories have provided convincing evidence that polyphenols present in green tea afford protection against cancer in both in vivo and in vitro studies. Recently, epigallocatechin gallate (EGCG), a putative chemopreventive agent and a major component of green tea, was reported to inhibit tumour invasion and angiogenesis, processes that are essential for tumour growth and metastasis. Understanding the basic principles by which EGCG inhibits tumour invasion and angiogenesis may lead to the development of new therapeutic strategies, in addition to supporting the role of green tea as a cancer chemopreventive agent.

Theophylline administration markedly reduces hepatic and pulmonary implantation of B16-F10 melanoma cells in mice

Theophylline-treated B16-F10 melanoma cells show a lower experimental metastatic potential in vivo. To identify the possible mechanism(s) involved and on the basis of previous reports, we tested the induction of apoptosis in B16-F10 cells. Fluorescence activated cell sorter (FACS) analysis and p53 overexpression in theophylline-treated B16-F10 melanoma cells appeared to suggest enhanced cell death by apoptosis. The in vivo effects of orally administered theophylline in mice were investigated using different treatment schedules in mice that had undergone hepatic or pulmonary colonization with tumour cells. Mice received theophylline in their drinking water according to different protocols: (i) from 3 days before tumour cell inoculation until animal sacrifice ('early treatment'); (ii) from 3 days before until 3 days after tumour cell inoculation ('short treatment'); or (iii) from 3 days after tumour cell inoculation until animal sacrifice ('late treatment'). In the 'early treatment' group, the number of melanoma foci was reduced by 92.3% in the liver and 81.4% in the lung compared with control animals (P < 0.001). In the 'short treatment' group, there was an 80.2% and 72.2% reduction in liver and lung metastases, respectively (P < 0.001). In the 'late treatment' group, the inhibition of metastasis was 59.7% for liver and 45.3% for lung (P < 0.005). Survival studies showed that 50% of the 'early' theophylline-treated animals died 33.2 +/- 2.0 days after intrasplenic injection (control group: 23.1 1.8 days; P < 0.001) and 33.9 +/- 2.5 days after tail vein injection (control group: 24.1 +/- 1.4 days; P < 0.001). Taken together, these observations provide useful information for the potential clinical application of theophylline as a chemotherapeutic agent against malignant melanoma.

Novel nitric oxide and superoxide generation inhibitors, persenone A and B, from avocado fruit

One known, (2R)-(12Z,15Z)-2-hydroxy-4-oxoheneicosa-12,15-dien+ ++-1-yl acetate (1), and two novel compounds, persenone A (2) and B (3), have been isolated from avocado fruit (Persea americana P. Mill), as inhibitors of superoxide (O(2)(-)) and nitric oxide (NO) generation in cell culture systems. They showed marked inhibitory activities toward NO generation induced by lipopolysaccharide in combination with interferon-gamma in mouse macrophage RAW 264.7 cells. Their inhibitory potencies of NO generation (1, IC(50) = 3.6; 2, IC(50) = 1.2; and 3, IC(50) = 3.5 microM) were comparable to or higher than that of a natural NO generation inhibitor, docosahexaenoic acid (DHA; IC(50) = 4.3 microM). Furthermore, compounds 1-3 and DHA markedly suppressed tumor promoter 12-O-tetradecanoylphorbol-13-acetate-induced O(2)(-) generation in differentiated human promyelocytic HL-60 cells (1, IC(50) = 33.7; 2, IC(50) = 1.4; 3, IC(50) = 1.8; and DHA, IC(50) = 10.3 microM). It is notable that they were found to be suppressors of both NO- and O(2)(-)-generating biochemical pathways but not to be radical scavengers. The results indicate that these compounds are unique antioxidants, preferentially suppressing radical generation, and thus may be promising as effective chemopreventive agent candidates in inflammation-associated carcinogenesis.

Enhanced invasion of Tax-expressing fibroblasts into the basement membrane is repressed by phosphorylated ascorbate with simultaneous decreases in intracellular oxidative stress and NF-kappa B activation

Invasion of rat fibroblastic cells Rat-1 through Matrigel was shown to be promoted by transfection with tax gene of human T-cell leukemia virus type 1. We found that an oxidation-resistant type of vitamin C (Asc), Asc-2-O-phosphate (Asc2P), inhibited the invasion of the tax-transfected Rat-1 cells (W4 cells). Intracellular Asc (Ascin), after enzymatic dephosphorylation of administered Asc2P, was more abundant in W4 cells than in Rat-1 cells, and the ratio of dehydroascorbic acid versus Asc was increased in W4 cells but scarcely in Rat-1 cells, according to the enhanced level of intracellular reactive oxygen species (ROSin) in W4 cells. Asc2P notably repressed the increases in both ROSin and secretion of matrix metalloproteases (MMPs), but did not affect Tax protein expression in tax-transfectants. NF-kappa B activation, as evidenced by its translocation to the nucleus in W4 cells, was also repressed by Asc2P. Thus, the tax-promoted invasion together with the enhanced production of MMPs occurred with NF-kappa B activation and the increase in ROSin, both of which were effectively reduced by Asc2P. These findings indicate the therapeutic efficacy of Ascin-enriching agents for the prevention against tumor invasion in which ROSin plays a major role.

Nitroxides and malignant human tissues: electron spin resonance in colorectal neoplastic and healthy tissues

Healthy and neoplastic colorectal human tissues of as many as 12 patients have been studied, immediately after surgery, by electron spin resonance (ESR) of stable nitroxides at physiological temperature. Cells were maintained in a living state using the McCoy's 5A culture medium. The very low concentration changes of hydrophilic and lipophilic nitroxides allowed us to establish that the response to the oxidative stress induced by the occurrence of nitroxides in healthy and tumor cells was very weak, thus suggesting these compounds are good candidates for contrast enhancement agents in magnetic resonance imaging of colorectal tumor. The analysis of the computed ESR line shape of lipophilic nitroxides in both healthy and malignant cells of the same patient agreed for an unmodified physical status of the membranes where they were mainly localized. The results reported here proved that the comparison between ESR results must be made in tissues from the same patient and that the physical status of the membranes depended more on the patient history than on changes in the colorectal cell membrane fluidity induced by the neoplastic process.

Effects of antioxidant enzyme overexpression on the invasive phenotype of hamster cheek pouch carcinoma cells

To examine the role of reactive oxygen species on the invasive phenotype of cancer cells, we overexpressed manganese- and copper-zinc-containing superoxide dismutases (MnSOD, CuZnSOD) and catalase (Cat) in hamster cheek pouch carcinoma (HCPC-1) cells in vitro using adenoviral vector-mediated gene transfer. Hamster cheek pouch carcinoma cells were transduced with these adenoviral vector constructs alone, or in combination, at concentrations [i.e., multiplicity of infectivity (MOI)] of 100 MOI each. The Escherichia coli beta-galactosidase reporter construct was used as a control virus. Protein expression was examined by Western blot analysis and enzymatic activities were measured using spectrophotometry. To observe the effects of transgene overexpression on in vitro tumor cell invasion, we used the membrane invasion culture system, an accurate and reliable method for examining tumor cell invasion, in vitro. This assay measures the ability of tumor cells to invade a basement membrane matrix consisting of type IV collagen, laminin, and gelatin. MnSOD overexpression resulted in a 50% increase in HCPC-1 cell invasiveness (p < .001); co-overexpression of MnSOD with Cat partially inhibited this effect (p < .05). Moreover, co-overexpression of both SODs resulted in a significant increase in invasiveness compared with the parental HCPC-1 cells (p < .05). These changes could not be correlated with the 72 kDa collagenase IV or stromolysin activities using zymography, or the downregulation of the adhesion molecules E-cadherin or the alpha4 subunit of the alpha4beta1 integrin. These results suggest that hydrogen peroxide may play a role in the process of tumor cell invasion, but that the process does not rely on changes in matrix metalloproteinase activity in the cells, or the expression of cell adhesion molecules.

Ascorbic acid recycling in Nb2 lymphoma cells: implications for tumor progression

Analysis of cultured rat "Nb2 lymphoma" cell lines, showing different degrees of malignant progression, can lead to identification of phenotypic changes associated with this phenomenon in T-cell cancers. In the present study we have compared the metastatic sublines, Nb2-11 and Nb2-SFJCD1, with regard to ascorbate and glutathione recycling, important processes in cellular protection from oxidative stresses. Whereas the Nb2-11 subline is prolactin (PRL)-dependent, the genetically related Nb2-SFJCD1 subline is growth factor-independent and shows more chromosomal alterations, indicative of more advanced progression. The Nb2-SFJCD1 cells, compared to the Nb2-11 cells, were less sensitive to toxic effects of dehydroascorbate, a potentially toxic oxidation product of ascorbate. Results were consistent with a significantly higher production of reducing equivalents (e.g., NADPH, GSH) and an accelerated reduction of dehydroascorbate by homogenates of Nb2-SFJCD1 cells. However, the increased resistance was apparently not directly related to the cellular uptake and reduction of dehydroascorbate by whole cells, which was similar in both cell lines. Observations indicate that Nb2 lymphoma cells, in their progression to malignancy, can acquire an enhanced capability to protect themselves from oxidative damage assisting them in withstanding the oxidative stress that anti-neoplastic drugs can cause. The adaptation may also be a mechanism that is utilized by tumor cells in suppressing apoptosis and other protective cellular functions facilitating, or potentiating, a tumor cell's ability to become more metastatic. However, the mechanism leading to this augmented capacity of Nb2 lymphoma cells to resist oxidative stress in not known and is the subject for further study.