Tatsuhiko Narita

Wakame seaweed suppresses the proliferation of 7,12-dimethylbenz(a)-anthracene-induced mammary tumors in rats.

We examined the anti‐tumor proliferation effects of wakame seaweed on 7,12‐dimethylbenz(a)‐anthracene (DMBA)‐induced rat mammary tumor. DMBA was administered to 8‐week‐old female Sprague‐Dawley rats, and rats which developed mammary tumors were assigned randomly to three groups. Commercial rat feed was used in a control group (group I‐A), and two feed mixtures were prepared, which contained commercial rat feed blended with wakame at 1.0% (group I‐B) and 5.0% (group I‐C) by weight. The respective feeds were given to each group for 8 weeks, and changes in mammary tumor size were compared. At the end of the experiment, mammary tumors and thyroid glands were resected to compare their weights. Serum total iodine and thyroxin (T4) levels were measured. Immunohistochemical studies for bromodeoxyuridine (BrdU) labeling, transforming growth factor (TGF)‐β, and apoptosis were carried out in the resected tumor. Significant suppression of tumor growth was observed in groups I‐B and I‐C compared with I‐A. In groups I‐B and I‐C, the weights of resected mammary tumors were significantly lower and serum total iodine concentration was significantly higher than in I‐A. BrdU indices were significantly lower in groups I‐B and I‐C, compared with I‐A. TGF‐β and apoptotic index were inversely related to BrdU. These results suggest that iodine is transported from the serum into mammary tissues and induces apoptosis through the expression of TGF‐β. In conclusion, wakame suppressed the proliferation of DMBA‐induced mammary tumors.

C-erbB-2 protein in the sera of breast cancer patients

SummaryThe c-erbB-2 protein was measured in sera of patients with breast cancer or benign breast diseases to study the significance of this protein as a tumor marker. The mean value and positive rate for this protein (assuming 20 U/ml as the cut-off value) were 11.8 U/ml (0%) in benign breast disease (n=30), 11.8 U/ml (3.1%) in stage I/II primary breast cancer (n=64), 38.2 U/ml (29.4%) in stage III/IV primary breast cancer (n=17), 17.9 U/ml (33.3%) in locally recurrent breast cancer (n=12), 298.4 U/ml (51.0%) in recurrent breast cancer with distant metastases (n=51), and 12.9 U/ml (0%) in those with no evidence of recurrence (n=57). Thus, the serum c-erbB-2 protein level was significantly higher in the distant metastatic group. In patients with distant metastases, there was a close association between expression of c-erbB-2 protein in the primary tumor and the serum c-erbB-2 protein level. On the basis of these results, serum c-erbB-2 protein was thought to be useful as a tumor marker for postoperative monitoring of breast cancer, especially in patients positive for expression of this protein in primary cancer tissue.

Involvement of hepatocyte growth factor in increased integrin expression on HepG2 cells triggered by adhesion to endothelial cells.

Adhesion of cancer cells to vascular endothelium is an important step in haematogenous metastasis of cancer. A human hepatocellular carcinoma cell line, HepG2, strongly adheres to human umbilical vein endothelial cells (HUVECs) through the interaction of E-selectin and its carbohydrate ligand sialyl Lewis X. In this study, we investigated alteration in integrin expression on HepG2 cells, which follows the selectin-mediated initial adhesion of HepG2 cells to HUVECs. Expression of alpha2beta1 integrin was markedly increased when the HepG2 cells adhered to HUVECs. Among the tested cytokines that are known to be produced by endothelial cells, recombinant hepatocyte growth factor (rHGF) could replace the effect of HUVECs, and a similar increase in integrin expression was observed by the addition of 20 ng ml-1 rHGF to HepG2. The increment of alpha2beta1 integrin expression was significantly inhibited by anti-HGF neutralizing antibody treatment. HepG2 cells expressed alpha2, alpha6, beta1, and beta4 integrin subunits, but expression of integrins other than alpha2beta1 was not affected by the rHGF treatment. The rHGF treatment of HepG2 cells resulted in augmented adhesion to immobilized collagen. This augmentation in adhesion to collagen was completely blocked by the addition of anti-alpha2- or anti-beta1-integrin antibody. In double-chamber chemoinvasion experiments, transmigration of the HepG2 cells through extracellular matrix (ECM) gel was significantly accelerated by co-cultivation with HUVECs. A similar level of enhancement in transmigration activity of the cancer cells was observed by the addition of rHGF. Our interpretation of the results described above is that the cancer cells received stimulation from cytokines, such as HGF, presented by vascular endothelial cells, following the initial adhesion of cancer cells via selectins. This resulted in the secondary increment in the expression of cell adhesion molecules, such as the alpha2beta1 integrin, and led to the augmented adhesive activities of cancer cells towards extracellular matrices at vascular walls. We suggest that this sequence of events is involved in the facilitated migration of some cancer cells to extravascular tissues.

Suppressive effect of iodine on DMBA-induced breast tumor growth in the rat

Concerning the suppressive effect of inorganic iodine on the growth of 7,12‐dimethyl‐benz(a)anthracene (DMBA)‐induced breast tumor in female Sprague‐Dawley (SD) rats, we previously reported that although iodine itself had a suppressive effect on the tumor growth, its effect was not as strong as that of MPA (medroxy‐progesterone acetate). However, the combined medication of iodine at a low concentration + MPA showed a stronger effect than MPA alone. The purpose of the present study is to elucidate this mechanism of action by determining the uptake of the administered iodine into breast tumor tissue. Breast tumors were induced with DMBA in female SD rats, and these animals were treated with MPA + inorganic iodine at various concentrations for 4 weeks to determine tumor growth and tumor iodine content. In the comparison of tissue iodine content in growth‐suppressive tumors with that in nonsuppressive tumors, the former showed a much higher iodine content. This suggests that direct uptake of inorganic iodine by breast tumors led to the suppression of tumor growth.

Involvement of adhesion molecules in metastasis of SW1990, human pancreatic cancer cells

Background and Objective: Peritoneal dissemination and hepatic metastasis commonly occur after patients with pancreatic cancer have undergone surgery. It is thought that specific adhesion molecules play corresponding roles in cancer metastasis.

Alteration of integrins by heparin-binding EGF-like growth factor in human breast cancer cells

The adhesion of cancer cells to the vascular endothelium is an important step in the hematogenous metastasis of cancer. Human breast cancer cells adhere to human umbilical vein endothelial cells (HUVECs) through the interaction of E selection on HUVECs and the carbohydrate ligand sialyl Lewisx on the cancer cells. We investigated the alteration of integrin expression on human breast cancer cells, following selectin-mediated initial adhesion to HUVECs. Four cell lines derived from human breast cancer expressed alpha 2-, alpha 3-, alpha 5-, alpha 6- and beta 1-integrins. The expression of alpha 2 beta 1- and alpha 3 beta 1-integrins on BT-20 cells, strongly expressing epidermal growth factor (EGF) receptors, was markedly increased by addition of the heparin-binding EGF-like growth factor (HB-EGF). The expression of alpha 2 beta 1-integrin on SK-BR-3 cells also was increased by the addition of HB-EGF. However, no such effect of HB-EGF on the expression of integrins was observed in T-47D and MCF-7 cells, nor on expression of the EGF receptor. The increase of integrin expression in BT-20 cells was inhibited by the addition of the tyrosine kinase inhibitor genistein. HB-EGF treatment of BT-20 or SK-BR-3 cells resulted in the augmentation of cancer cell adhesion to immobilized collagen. When BT-20 cells were cocultured with HUVECs, a similar level of augmentation of cancer cell adhesion to collagen was observed. The augmentation of cancer cell adhesion to collagen was inhibited by addition of an anti-HB-EGF-neutralizing antibody. Our interpretation of the results described above is that the cancer cells receive stimulation from cytokines, such as HB-EGF, produced by vascular endothelial cells, following the initial adhesion of cancer cells via selectins. This results in a secondary increase in the expression of cell adhesion molecules, such as the beta 1-integrin family, and leads to augmentation in the adhesive activities of cancer cells at the vessel walls. We postulate that these events are the ones involved in the enhanced transmigration of cancer cells to extravascular tissues following the selectin-mediated adhesion to the endothelium.

Modulation of MUC1 mucin as an escape mechanism of breast cancer cells from autologous cytotoxic T-lymphocytes.

MUC1 mucin is known to serve as a target molecule in the killing of breast cancer cells by cytotoxic T-lymphocytes (CTLs). We searched for a possible mechanism allowing tumour cells to escape from autologous CTLs. When the killing of breast cancer cells by autologous lymphocytes was examined in 26 patients with breast cancer, significant tumour cell lysis was observed in 8 patients, whereas virtually no autologous tumour cell lysis was detected in as many as 18 patients. In the patients who showed negligible tumour cell lysis, the autologous tumour cells expressed MUC1-related antigenic epitopes much more weakly than the tumour cells in the patients who exhibited strong cytotoxicity (significant statistically at P< 0.0005–0.0045), suggesting that the unresponsiveness of cancer cells to CTLs observed in these patients was mainly due to loss of MUC1 expression or modulation of its antigenicity. A breast cancer cell line, NZK-1, established from one of the cytotoxicity-negative patients, did not express MUC1 and was resistant to killing by CTLs, while control breast cancer cell lines expressing MUC-1 were readily killed by CTLs. Transfection of NZK-1 cells with MUC1 cDNA induced significant lysis by autologous T-lymphocytes. These results supported the importance of MUC1 mucin in autologous anti-tumour immunity, but suggested that the major escape mechanism of tumour cells from autologous T-lymphocytes is the loss and/or modulation of MUC1 antigenicity on tumour cells, which would limit the effectiveness of possible immunotherapy designed to target the MUC1 mucin.

Increased expression of integrins by heparin-binding EGF like growth factor in human esophageal cancer cells

The adhesion of cancer cells to vascular endothelium is an important step in the hematogenous metastasis of cancer. The authors investigated the alteration of integrin expression in human esophageal cancer cells, following the selectin-mediated initial adhesion to endothelial cells. The expression of alpha2 beta1 and alpha3 beta1 integrins in esophageal cancer cells (TE-1 and T.Tn), strongly expressing EGF-receptors, were markedly increased by the addition of the heparin-binding EGF like growth factor (HB-EGF). The increase of integrin expression in esophageal cancer cells was inhibited by the addition of the tyrosine kinase inhibitor, genistein. HB-EGF treatment of esophageal cancer cells resulted in the augmentation of cancer cell adhesion to immobilized collagen. When esophageal cancer cells were co-cultured with endothelial cells, similar levels of augmentation of cancer cell adhesion to collagen were observed. The augmentation of cancer cell adhesion to collagen was inhibited by the addition of anti-HB-EGF neutralizing antibody. Our interpretation of the results described above is that the cancer cells receive stimulation from cytokines, such as HB-EGF, produced by endothelial cells, following initial adhesion of cancer cells via selectins. This results in a secondary increase in the expression of cell adhesion molecules, such as the beta1 integrin family, and leads to augmentation in the adhesive activities of cancer cells at vessel walls. We postulate that this sequence of events involves the enhanced transmigration of cancer cells to extravascular tissues, following the selectin-mediated adhesion to the endothelium.

Induction of E-selectin expression on vascular endothelium by digestive system cancer cells

The adhesion of circulating cancer cells to the vascular endothelium is an important step in the hematogenous metastasis of cancer. Carbohydrate antigens, such as sialyl Le x and sialyl Le a, are expressed on the surface of cancer cells, and E-selectin is expressed on the surface of endothelial cells to effect this adhesion. ~ 3 The expression of E-selectin on endothelial cells is enhanced by inflammatory cytokines, such as IL-1 ~ or TNF or. 4 In this connection, a report has been found stating that certain cytokines promote tumor cell adhesion to endothelial cellsr Recent evidence suggests that Eselectin is expressed on the endothelial cells of small vessels adjacent to cancer nests, and that serum Eselectin levels are elevated in patients with metastatic cancer. 6 Accordingly, it is surmised that cancer cells induce the expression of E-selectin on the endothelium either directly or indirectly. However, there are few studies of the interaction between cancer and endothelial cells. 7,8 Hence, our investigation focused on this interaction, i.e., the cancer cells of the digestive system acting upon vascular endothelium in the expression of E-selectin.

Adhesion of human breast cancer cells to vascular endothelium mediated by Sialyl Lewisx/E-selectin

The adhesion molecules involved in the attachment of breast cancer cells to endothelial cells were investigated in vitro. All six human breast cancer cell lines expressed sialyl Lewisx antigen (s-Lex). Only two cell lines expressed sialyl Lewisa antigen. A correlation was found between the degree of s-Lex expression and the attachment of cancer cells to human umbilical vein endothelial cells (HUVECs) activated by IL-1β. Monoclonal antibodies against s-Lex or E-selectin inhibited this adhesion. These findings suggest that s-Lex on the surface of cancer cells and E selectin on the surface of endothelial cells play roles in adhesion of breast cancer cells to vascular endothelium.