Electrophoretic analysis of proteins associated with tumor cell invasion

EphA2 as a target for ovarian cancer therapy

EphA2 is a receptor tyrosine kinase that is overexpressed by many human cancers, and is often associated with poor prognostic features. It is involved in many processes crucial to malignant progression, such as migration, invasion, metastasis, proliferation, survival and angiogenesis. Inducing EphA2 downregulation by any one of several mechanisms (antibody-mediated inhibition of signalling, antibody-mediated downregulation of total EphA2 expression and siRNA-mediated inhibition of expression) has been shown to decrease tumour growth, prolong survival and inhibit angiogenesis in multiple preclinical models of ovarian, breast and pancreatic cancer. Targeting EphA2 is especially attractive in ovarian cancer, in which overexpression is present in > 75% of cases. This disease is highly responsive to chemotherapy, and EphA2 inhibition is especially effective in combination with taxanes. This demonstrated efficacy, along with the low expression of EphA2 by normal adult tissues and lack of demonstrable toxicities in preclinical models, suggest that long-term treatment with EphA2-targeting agents is an attractive approach for ovarian cancer therapy.

Protection effect of piper betel leaf extract against carbon tetrachloride-induced liver fibrosis in rats

Piper betel leaves (PBL) are used in Chinese folk medicine for the treatment of various disorders. PBL has the biological capabilities of detoxication, antioxidation, and antimutation. In this study, we evaluated the antihepatotoxic effect of PBL extract on the carbon tetrachloride (CCl(4))-induced liver injury in a rat model. Fibrosis and hepatic damage, as reveled by histology and the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were induced in rats by an administration of CCl(4) (8%, 1 ml/kg body weight) thrice a week for 4 weeks. PBL extract significantly inhibited the elevated AST and ALT activities caused by CCl(4) intoxication. It also attenuated total glutathione S-transferase (GST) activity and GST alpha isoform activity, and on the other hand, enhanced superoxide dismutase (SOD) and catalase (CAT) activities. The histological examination showed the PBL extract protected liver from the damage induced by CCl(4) by decreasing alpha-smooth muscle actin (alpha-sma) expression, inducing active matrix metalloproteinase-2 (MMP2) expression though Ras/Erk pathway, and inhibiting TIMP2 level that consequently attenuated the fibrosis of liver. The data of this study support a chemopreventive potential of PBL against liver fibrosis.

Multiple Aspects of the Phenotype of Mammary Epithelial Cells Transformed by Expression of Activated M-Ras Depend on an Autocrine Mechanism Mediated by Hepatocyte Growth Factor/Scatter Factor

Multiple aspects of the transformed phenotype induced in a murine mammary epithelial cell line scp-2 by expression of activated G22V M-Ras, including maintainance of cell number at low density, anchorage-independent growth, invasion of Matrigel, and secretion of matrix metalloproteinases (MMP) 2 and 9, were dependent on an autocrine mechanism. Conditioned medium from dense cultures of scp-2 cells expressing G22V M-Ras, but not from parental cells, induced activation of Erk and Akt in cells expressing G22V M-Ras, maintained the cell number and promoted anchorage-independent growth of cells expressing G22V M-Ras (although not the parental cells), and induced scattering of MDCK cells. The latter activities were blocked by neutralizing antibodies to hepatocyte growth factor/scatter factor (HGF/SF) and could be mimicked by HGF/SF. Anti-HGF/SF antibodies also inhibited invasion of Matrigel, and the production of MMP-2 and MMP-9, together with urokinase-type plasminogen activator, was secreted by G22V M-Ras scp-2 cells but not by parental cells. Invasion of Matrigel was blocked by an inhibitor of MMPs, BB94, and by the mitogen-activated protein kinase kinase 1/2 kinase inhibitor PD98059 but was only marginally affected by the phosphatidylinositol 3-kinase inhibitor LY294002. Autocrine HGF/SF was thus critical for expression of key features of the phenotype of mammary epithelial cells transformed by expression of activated M-Ras.

Characterization of matrix metalloproteinase-2 and -9 in cerebrospinal fluid of clinically normal dogs

OBJECTIVE

To characterize matrix metalloproteinase (MMP)-2 and -9 in CSF of clinically normal dogs.

SAMPLE POPULATION

Samples of CSF collected from 23 dogs.

PROCEDURE

Dogs were anesthetized, CSF samples were collected, and dogs were then euthanatized. Each CSF sample was evaluated immediately for RBC count, WBC count, and protein and glucose concentrations, and cytologic examination also was performed. Samples were considered normal when protein concentration was < 25 mg/dL and CSF contained < 6WBCs/microL and < 25 RBCs/microL. Samples were stored at -70 degrees C. Sections of brain tissue were collected and processed for histologic examination. The MMPs were evaluated by use of gelatin zymography and a polyclonal antibody-based sandwich ELISA.

RESULTS

Mean WBC count for CSF samples was < 1 WBC/microL (range, 0 to 3 WBCs/mL). Mean protein concentration was 12 mg/dL (range, 8 to 17 mg/dL). Mean RBC count was 3.65 RBCs/microL (range, 0 to 21 RBCs/microL). All CSF samples generated a clear band on zymography gels that corresponded to the human commercial standard of proenzyme MMP-2. Other major clear bands were not detected on zymography gels. Bands correlating to MMP-9 were not detected in any samples. The ELISA results revealed a mean +/- SD proenzyme MMP-2 concentration of 5.61 +/- 1.92 ng/mL (range, 3.36 to 10.83 ng/mL).

CONCLUSIONS AND CLINICAL RELEVANCE

The proenzyme form of MMP-2 is detectable in CSF of clinically normal dogs, whereas MMP-9 is not detectable. Additional investigation of MMPs in CSF from dogs with various diseases of the nervous system is indicated.

Activation of matrix metalloproteinase-2 by overexpression of manganese superoxide dismutase in human breast cancer MCF-7 cells involves reactive oxygen species

Matrix metalloproteinases (MMPs) participate in cell migration and remodeling processes by affecting the extracellular matrix. MMP-2 is thought to be involved in cancer cell invasiveness. It has been proposed that the activity of MMP-2 can be modulated by intracellular reactive oxygen species (ROS)/reactive nitrogen species. We hypothesized that manganese superoxide dismutase (MnSOD) could mediate MMP-2 activity by changing the intracellular ROS level and that nitric oxide ((.)NO) may be involved in this process. Human breast cancer MCF-7 cells were stably transfected with plasmids containing MnSOD cDNA. A 2-30-fold increase of MnSOD protein and activity was observed in four clones. Our data demonstrated that overexpression of MnSOD stimulated the activation of MMP-2 with a corresponding elevation of ROS. A decrease in ROS by ebselen, a glutathione peroxidase mimetic, or by transduction of adenovirus containing human catalase or glutathione peroxidase cDNA abolished the effect of MnSOD on MMP-2 activation. Treatment of MCF-7 cells with antimycin A or rotenone increased intracellular ROS production and MMP-2 activation simultaneously. Our data also showed a suppression of endothelial nitric-oxide synthase expression that was accompanied by decreased (.)NO production in MnSOD-overexpressing cells. However, the changes in endothelial nitric-oxide synthase and (.)NO did not correlate with the MnSOD activity. Corresponding changes of MMP-2 activity after the addition of a NOS inhibitor (N(G)-amino-l-arginine) or a (.)NO donor ((Z)-1-[(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate) to the cells suggested the possibility that (.)NO may be involved in the MnSOD-mediated MMP-2 activation pathway. These results indicate that MnSOD induces MMP-2 activity by regulation of intracellular ROS and imply that signaling pathways involving (.)NO may also be involved in the MnSOD mediation of MMP-2 activity.

Proteolysis in human breast cancer

BACKGROUND

The process of proteolysis is important at several stages of the metastatic cascade. A balance between the expression of the genes encoding endogenous proteinases and inhibitors exists and when the production of proteinases exceeds that of inhibitors proteolysis occurs.

AIMS

To determine whether differences in the profile and activity of proteinases and inhibitors exist within breast tumour tissue (n = 51), surrounding background breast tissue (n = 43), normal breast tissue from breast reduction mammoplasty operations (n = 10), and cells of the breast cancer cell line, MCF-7.

METHODS

Proteinase (matrix metalloproteinase 1 (MMP-1), MMP-2, MMP-3, MMP-9, urokinase-type plasminogen activator (uPA), and tissue-type PA (tPA)) and inhibitor (tissue inhibitor of metalloproteinases; TIMP-1 and TIMP-2) expression and proteinase activity were compared using substrate zymography, western blotting, immunohistochemistry, and quenched fluorescent substrate hydrolysis.

RESULTS

The presence of all proteinases and inhibitors was greater in breast tumour tissue when compared with all other types of breast tissue (p < 0.05). The activity of total MMPs as determined by quenched fluorescent substrate hydrolysis was also greater in breast tumours (p < 0.05).

CONCLUSIONS

There is increased proteolysis in human breast tumours when compared with other breast tissues.

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.

Proteolysis in human breast and colorectal cancer

Proteolysis occurs when proteinase activity exceeds inhibitor activity. Proteolysis is normally tightly regulated and is involved in cancer invasion and metastasis. The aim of this study was to compare proteolysis in breast and colorectal cancer. Proteinase and inhibitor expression were analysed in paired tumour and normal tissue samples from 43 breast and 24 colorectal cancer patients using substrate zymography, Western blotting and quenched fluorescence substrate hydrolysis. The expression of the latent forms of matrix metalloproteinase-2 (MMP-2), MMP-3 and MMP-9, urokinase plasminogen activator (uPA), tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2 expression were observed in both tumour and normal tissue samples from breast and colorectal tissue; however, expression was greater in the tumour tissue. Expression of active MMP-2 and MMP-9 and the total MMP activity were greater in tumour compared to normal samples in both tissues (P < 0.05). The expression of all proteinases and total MMP activity was greater in colorectal tissue than breast tissue samples. Breast and colorectal cancer demonstrated different proteinase profiles, however proteolysis in both tissues was greater in tumour tissue than normal tissue.

Proteolysis in colorectal cancer

BACKGROUND

The process of metastasis is complex, involving many interrelated stages, including proteolysis. Proteolysis occurs in both normal and pathological processes and involves the breakdown of the extracellular matrix and/or basement membrane by proteolytic enzymes. Normally, proteolysis is tightly controlled by specific endogenous proteinase inhibitors. However, in certain disease processes, including cancer, controlled but abnormal proteolysis seems to occur. Proteinases involved in tumour invasion and metastasis include the matrix metalloproteinases (MMPs) and the serine proteinases.

AIMS

To gain a greater understanding of the proteolytic process occurring in colorectal cancer and to determine which, if any, proteinases are upregulated.

METHODS

The synthesis of proteinases and their inhibitors was compared in paired tumour and normal tissue samples from patients with colorectal cancer (n = 24). Substrate zymography was used to determine the synthesis of MMPs (MMP-2, MMP-9, and MMP-3) and the plasminogen activators (urokinase and tissue-type plasminogen activators); enzyme linked immunosorbent assays (ELISAs) were used to determine the concentrations of MMP-1 and tissue inhibitor of metalloproteinase 1 (TIMP-1); and the technique of quenched fluorescence substrate hydrolysis was performed to determine the total MMP activity of each sample.

RESULTS

In general, both proteinase and inhibitor expression was greater in the tumour tissue when compared with the corresponding normal colorectal tissue. The amount of active MMPs was greater in the tumour tissue.

CONCLUSIONS

The increased extracellular proteinase concentrations and activity may encourage tumour invasion and metastasis. This study points to MMP-9 as being of potential major importance in the development of this form of cancer.

Epidermal growth factor (EGF) increases the in vitro invasion, motility and adhesion interactions of the primary renal carcinoma cell line, A704

Metastasis is a multistep process that involves alterations in a tumour cell's invasion, motility and adhesive capabilities. This study examined the effect of EGF on the in vitro invasion, motility and adhesion of the primary renal adenocarcinoma cell line, A704. Stimulation of the tumour cells by EGF (40 ng/ml) for a period of 24 h increased the in vitro invasion (P = 0.040) and motility (P = 0.039). Cell adhesion was examined on fibronectin, laminin, collagen IV and a 1:1:1 mix of the three extracellular matrix components. After EGF (40 ng/ml) stimulation, adhesion was significantly decreased on fibronectin (P = 0.022) and collagen type IV (P = 0.026), but increased on the 1:1:1 mix of extracellular matrix components (P = 0.022). The 92 kDa matrix metalloproteinase (MMP-9) present in the cell-conditioned medium was also increased after a 24 h stimulation with EGF (40 ng/ml) when measured. Hence, EGF can modulate the in vitro invasion, motility, adhesiveness and matrix metalloproteinase production in the A704 cell line, and subsequently may have a role in the metastatic potential of some renal carcinomas.

Acidic pH enhances the invasive behavior of human melanoma cells

As a consequence of poor perfusion and elevated acid production, the extracellular pH (pHex) of tumors is generally acidic. Despite this, most in vitro experiments are still performed at the relatively alkaline pHex of 7.4. This is significant, because slight changes in pHex can have profound effects on cell phenotype. In this study we examined the effects of mildly acidic conditions on the in vitro invasive potential of two human melanoma cell lines; the highly invasive C8161, and poorly invasive A375P. We observed that culturing of either cell line at acidic pH (6.8) caused dramatic increases in both migration and invasion, as measured with the Membrane Invasion Culture System (MICS). This was not due to a direct effect of pH on the invasive machinery, since cells cultured at normal pH (7.4) and tested at acidic pH did not exhibit increased invasive potential. Similarly, cells cultured at acidic pH were more aggressive than control cells when tested at the same medium pH. These data indicate that culturing of cells at mildly acidic pH induces them to become more invasive. Since acid pH will affect the intracellular pH (pHin) and intracellular calcium ([Ca2+]in), we examined the effect of these parameters on invasion. While changes in [Ca2+]in were not consistent with invasive potential, the changes in pHin were. While these conditions decrease the overall amount of gelatinases A and B secreted by these cells, there is a consistent and significant increase in the proportion of the activated form of gelatinase B.