Cancer metastasis. Organ colonization and the cell-surface properties of malignant cells

Sulforaphane as a Promising Natural Molecule for Cancer Prevention and Treatment

Tumorigenicity-inhibiting compounds have been identified in our daily diet. For example, isothiocyanates (ITCs) found in cruciferous vegetables were reported to have potent cancer-prevention activities. The best characterized ITC is sulforaphane (SF). SF can simultaneously modulate multiple cellular targets involved in carcinogenesis, including (1) modulating carcinogen-metabolizing enzymes and blocking the action of mutagens; (2) inhibition of cell proliferation and induction of apoptosis; and (3) inhibition of neo-angiogenesis and metastasis. SF targets cancer stem cells through modulation of nuclear factor kappa B (NF-κB), Sonic hedgehog (SHH), epithelial-mesenchymal transition, and Wnt/β-catenin pathways. Conventional chemotherapy/SF combination was tested in several studies and resulted in favorable outcomes. With its favorable toxicological profile, SF is a promising agent in cancer prevention and/or therapy. In this article, we discuss the human metabolism of SF and its effects on cancer prevention, treatment, and targeting cancer stem cells, as well as providing a brief review of recent human clinical trials on SF.

Correlation between Laminin and Cathepsin D Expressions in Breast Carcinoma

Aims and Background

Laminin is a major glycoprotein component of basement membrane which is an important barrier to tumor cells which must be breached before metastatic spread can occur. Proteolytic enzymes play an important role in mediating the passage of cancer cells through the basement membrane(BM) and extracellular matrix. We have compared the patterns of laminin and cathepsin D (CD) expressions in a range of benign and malignant breast lesions to better understand the process of tumor progression.

Methods

One hundred and sixty-two cases of breast samples comprising 18 fibroadenomas, 22 cases of fibrocystic disease, 96 cases of invasive ductal carcinoma and 26 carcinomas with intraductal components were evaluated for laminin and cathepsin D expressions by immunohistochemical staining.

Results

The prevalence of CD positivity in both neoplastic and stromal cell components were significantly higher in higher histological grade tumors compared to lower grades (P <0.01). Various severity of BM disruption correlated with histological grade of the carcinomas (P <0.001). There was a negative correlation between the laminin expression and CD presence.

Conclusions

It was confirmed that in a process of cancer cell invasion and metastasis, it could be necessary with the basement membrane disruption by proteinase secreted by cancer cells and especially by stroma cells of cancer.

High Chemotactic Motility and Growth in Hard Agar of a Variant of RSV-Transformed Fibroblasts are Lost in Late Passages

Cloning efficiency in hard agar (0.6%) and high chemotactic migration toward fibroblast conditioned medium have been shown to characterize metastatic tumor cells. We studied growth in 0.6% agar and chemotaxis of two lines of Rous Sarcoma virus-transformed Balb/ c3T3 cells, B77/3T3 (low metastatic) and AA12 (high metastatic), and compared them to their non-transformed counterpart, in order to verify whether these properties were maintained during several subcultivations. Cells were cryopreserved at early passages and thawed for experiments. Both assays were performed on freshly thawed cells (4-6 weeks in culture) and on cells which had been cultured 15-20 weeks after thawing. B77/3T3, which are tumorigenic but low metastatic and which have a very low cloning efficiency in hard agar (0.1-1%), showed a chemotactic response to Balb/c3T3 conditioned medium about two-fold higher than control Balb/c3T3. This response did not change with time in culture. AA12 cells, a genetic unstable variant of B77/3T3 selected for its growth in hard agar (0.6%), had a high cloning efficiency in hard agar and showed a high chemotactic motility (three-fold the controls). High growth in 0.6 % agar and high chemotaxis of AA12 were lost in late passages, where cells behaved as the controls. It seems that besides the already reported variation in anchorage-independent growth, genetically unstable tumor cells can also have important variations in chemotactic motility during subcultivations.

Discovery of potential biomarkers in human melanoma cells with different metastatic potential by metabolic and lipidomic profiling

Malignant melanoma, characterized by its ability to metastasize to other organs, is responsible for 90% of skin cancer mortality. To investigate alterations in the cellular metabolome and lipidome related to melanoma metastasis, gas chromatography-mass spectrometry (GC-MS) and direct infusion-mass spectrometry (DI-MS)-based metabolic and lipidomic profiling were performed on extracts of normal human melanocyte (HEMn-LP), low metastatic melanoma (A375, G361), and highly metastatic melanoma (A2058, SK-MEL-28) cell lines. In this study, metabolomic analysis identified aminomalonic acid as a novel potential biomarker to discriminate between different stages of melanoma metastasis. Uptake and release of major metabolites as hallmarks of cancer were also measured between high and low metastatic melanoma cells. Lipid analysis showed a progressive increase in phosphatidylinositol (PI) species with saturated and monounsaturated fatty acyl chains, including 16:0/18:0, 16:0/18:1, 18:0/18:0, and 18:0/18:1, with increasing metastatic potential of melanoma cells, defining these lipids as possible biomarkers. In addition, a partial-least-squares projection to latent structure regression (PLSR) model for the prediction of metastatic properties of melanoma was established, and central metabolic and lipidomic pathways involved in the increased motility and metastatic potential of melanoma cells were identified as therapeutic targets. These results could be used to diagnose and control of melanoma metastasis.

Amigo2-upregulation in Tumour Cells Facilitates Their Attachment to Liver Endothelial Cells Resulting in Liver Metastases

Since liver metastasis is the main cause of death in cancer patients, we attempted to identify the driver gene involved. QRsP-11 fibrosarcoma cells were injected into the spleens of syngeneic mice to isolate tumour sub-populations that colonize the liver. Cells from liver metastatic nodules were established and subsequently injected intrasplenically for selection. After 12 cycles, the cell subline LV12 was obtained. Intravenous injection of LV12 cells produced more liver metastases than QRsP-11 cells, whereas the incidence of lung metastases was similar to that of QRsP-11 cells. LV12 cells adhered to liver-derived but not to lung-derived endothelial cells. DNA chip analysis showed that amphoterin-induced gene and open reading frame 2 (Amigo2) was overexpressed in LV12 cells. siRNA-mediated knockdown of Amigo2 expression in LV12 cells attenuated liver endothelial cell adhesion. Ex vivo imaging showed that suppression of Amigo2 in luciferase-expressing LV12 cells reduced attachment/metastasis to liver to the same level as that observed with QRsP-11 cells. Forced expression of Amigo2 in QRsP-11 cells increased liver endothelial cell adhesion and liver metastasis. Additionally, Amigo2 expression in human cancers was higher in liver metastatic lesions than in primary lesions. Thus, Amigo2 regulated tumour cell adhesion to liver endothelial cells and formation of liver metastases.

Histological phenotype is correlated with the wall-invasion pattern of gallbladder adenocarcinoma

Gallbladder carcinoma (GBC) is one of the most aggressive malignancies, and frequently shows vascular invasion and lymph node metastasis. Our previous study has classified the wall-invasion pattern of GBC into two groups, i.e., infiltrative growth type (IG type) and destructive growth type (DG type). The DG type was significantly associated with poor clinical outcome. In this study, we analyzed the relationship between the wall-invasion pattern and the histological phenotype of GBC, using 61 surgically-resected primary gallbladder adenocarcinomas. Histologically, the 61 cases were classified into the biliary (44 cases, 72.1%), gastric foveolar (13 cases, 21.3%), and intestinal (4 cases, 6.6%) types. Biliary type frequently exhibited MUC1, but less frequently showed MUC2, MUC5AC, and MUC6. The biliary type and MUC1 expression were significantly correlated with DG type wall-invasion pattern (P = 0.020 and P < 0.001, respectively). In conclusion, histological phenotype and mucin expression were thought to be indicators of aggressiveness of GBC.

Advances in diagnosis, treatment and palliation of pancreatic carcinoma: 1990-2010

Several advances in genetics, diagnosis and palliation of pancreatic cancer (PC) have occurred in the last decades. A multidisciplinary approach to this disease is therefore recommended. PC is relatively common as it is the fourth leading cause of cancer related mortality. Most patients present with obstructive jaundice, epigastric or back pain, weight loss and anorexia. Despite improvements in diagnostic modalities, the majority of cases are still detected in advanced stages. The only curative treatment for PC remains surgical resection. No more than 20% of patients are candidates for surgery at the time of diagnosis and survival remains quite poor as adjuvant therapies are not very effective. A small percentage of patients with borderline non-resectable PC might benefit from neo-adjuvant chemoradiation therapy enabling them to undergo resection; however, randomized controlled studies are needed to prove the benefits of this strategy. Patients with unresectable PC benefit from palliative interventions such as biliary decompression and celiac plexus block. Further clinical trials to evaluate new chemo and radiation protocols as well as identification of genetic markers for PC are needed to improve the overall survival of patients affected by PC, as the current overall 5-year survival rate of patients affected by PC is still less than 5%. The aim of this article is to review the most recent high quality literature on this topic.

Metastasis suppressors and the tumor microenvironment

The most lethal and debilitating attribute of cancer cells is their ability to metastasize. Throughout the process of metastasis, tumor cells interact with other tumor cells, host cells and a variety of molecules. Tumor cells are also faced with a number of insults, such as hemodynamic sheer pressure and immune selection. This brief review explores how metastasis suppressor proteins regulate interactions between tumor cells and the microenvironments in which tumor cells find themselves.

N-Acetylgalactosaminyltransferase-14 as a potential biomarker for breast cancer by immunohistochemistry

Background

The post-translational modification of proteins, including glycosylation, differs between normal and tumor cells. The UDP-N-acetyl-D-galactosamine polypeptide N-acetylgalactosaminyltransferases (GalNAc-Tases) family of enzymes regulates the initial steps of mucin O-glycosylation and is responsible for the altered glycosylation state observed in cancer cells. Recently it was found that GalNAc-T14 mRNA is heterogeneously expressed in breast carcinomas compared to normal tissue, however the expression profile of GalNAc-T14 protein in breast carcinomas compared to normal tissue is still unknown. In this study, we assessed the expression profile of GalNAc-T14 protein in malignant and non-malignant breast tissues by immunohistochemistry to evaluate whether GalNAc-T14 might be a potential biomarker for breast cancer.

Methods

In formalin-fixed tissues, the expression level of GalNAc-T14 protein was evaluated by immunohistochemistry assay in breast tissues. Expression profiles were assessed in normal tissues, benign fibroadenomas and several types of carcinomas.

Results

Our results showed that GalNAc-T14 was heterogeneously expressed in breast carcinomas compared to non-malignant tissue. GalNAc-T14 expression was observed in 47/56 (83.9%) carcinoma samples, 7/48 (14.6%) non-malignant breast tissue samples. GalNAc-T14 expression level was associated with histological grade. For this enzyme a significant association with invasive ductal type, mucinous adenocarcinoma and ductal carcinoma in situ (DCIS) type was found.

Conclusion

Our results provide evidence that GalNAc-T14 may be a potential biomarker for breast cancer by immunohistochemistry. GalNAc-T14 expression level was associated with histological grade. GalNAc-T14 expression can provide new insights about breast cancer glycobiology.

Isolation and Characterization of Subpopulations of Rat Ascites Hepatoma Cell Line of AH109A with Different Metastatic Potentials

Rat ascites hepatoma cell line of AH109A proved to be divided into two subpopulations with different invasive and metastatic potentials, when cultured in the medium containing allogeneic rat sera. One population adheres to the culture dish, actively extending pseudopodia, and the other remains in a floating state. Utilizing this character, we have separated these two populations. After three successive separation steps, adhesive AH109A cells and floating AH109A cells were obtained. Adhesive AH109A cells proliferated more rapidly and invaded more actively than did floating AH109A cells. Adhesive AH109A cells metastasized mainly to lung, while floating AH109A cells to mesentery, when intravenously injected into tail veins. Histological studies revealed that adhesive AH109A cells showed lymphatic metastases to lung. These results suggest that the two populations separated from parental AH109A cells provide good models for the study of tumor invasion and tissue-specific metastasis and that adhesive AH109A cells can be used for the creation of lymphatic metastasis model of rats.

The laminin receptor and basement membrane dissolution: role in tumour metastasis

Tumour invasion and metastasis is a complex process involving multiple interactions of tumour cells with host cellular and extracellular elements. Metastasizing tumour cells traverse basement membranes at many stages in the metastatic cascade. Immunohistology studies demonstrate that the basement membranes are defective in all human malignant epithelial neoplasms studied to date. The basement membrane is absent in regions of microinvasion and adjacent to actively invading tumour cells. In contrast, benign neoplasms retain a continuous basement membrane. This distinction may have diagnostic value in surgical pathology. Tumour cells are hypothesized to traverse basement membranes by a three-step process: attachment, local degradation of the basement membrane by type IV collagenase and other proteases, and locomotion. The first step may be mediated in part by specific cell surface receptors which bind to laminin in the basement membrane. The laminin receptor has been purified from a series of different human carcinomas. The receptor has an Mr of 67 000 and a binding coefficient of 2 nM. The content of unoccupied receptors is markedly augmented in invasive human breast cancer compared to benign controls.

Do we need to redefine a cancer metastasis and staging definitions?

Metastasis is the most lethal attribute of cancer cells and clinical decisions regarding treatment are based largely upon the likelihood of developing metastases. However, improvements in detection as well as recent experimental data have raised questions about the most appropriate definition of a metastasis, especially whether the mere presence of cells at secondary sites constitute a metastatic lesion. After reviewing the experimental basis of metastasis, a definition of metastasis is proffered along with a proposal to consider regarding modification of staging parameters.

Metastasis: recent discoveries and novel treatment strategies

Most cancer deaths are due to the development of metastases, hence the most important improvements in morbidity and mortality will result from prevention (or elimination) of such disseminated disease. Some would argue that treatments directed against metastasis are too late because cells have already escaped from the primary tumour. Such an assertion runs contrary to the significant but (for many common adult cancers) fairly modest improvements in survival following the use of adjuvant radiation and chemotherapy designed to eliminate disseminated cells after surgical removal of the primary tumour. Nonetheless, the debate raises important issues concerning the accurate early identification of clonogenic, metastatic cells, the discovery of novel, tractable targets for therapy, and the monitoring of minimal residual disease. We focus on recent findings regarding intrinsic and extrinsic molecular mechanisms controlling metastasis that determine how, when, and where cancers metastasise, and their implications for patient management in the 21st century.

Alpha1-and beta2-adrenoceptors in the human liver with mass-forming intrahepatic cholangiocarcinoma: density and coupling to adenylate cyclase and phospholipase C

Besides the regulation of hepatic metabolic pathways in which adrenoceptors are mainly involved, their effect on the second messenger cAMP is thought to be related to the growth and differentiation of neoplastic cells. However, few studies have been done on the status of these structures in the human liver affected by cholangiocarcinoma (CC). Thus, in this study, changes in densities of alpha1- and beta2-adrenoceptors (alpha1-and beta2-ARs) were investigated in membranes of human liver with cholangiocarcinoma, and for comparison, in membranes of non-adjacent non-tumour liver using the potent antagonists [3H]-prazosin and [1I]-iodocyanopindolol (ICYP) respectively. In addition, the activity of membrane-bound phospholipase C (PLC) and adenylate cyclase (AC) was also studied. In CC liver, the density of alpha1-and beta2-ARs was significantly reduced, compared with non-tumour liver tissues (alpha1-ARs: 23.38+/-4.69 vs 80.35+/-10.52, P=0.0002 beta2-ARs: 14.27+/-2.93 vs 33.22+/-4.32 fmol/mg protein, P=0.03), whereas the ligand affinities (KD) remained unchanged. The beta2-selective antagonist ICI 118,551 was about 100 times more potent in inhibiting ICYP binding than the beta1-selective antagonist CGP 20712A; thus, more than 98% of the beta-ARs were of the beta2-subtypes. The AC activity upon stimulants acting on beta-AR (isoprenaline), G-protein (GTP, NaF) and AC (forskolin) was decreased in CC liver. Similarly, noradrenaline-stimulated PLC activity was significantly reduced in tumour tissues. In conclusion, in CC liver the alpha1- and beta2-ARs density was down-regulated and the neoplastic invasion blunted AC and PLC activity. These quantitative changes may help to elucidate not fully understood pathogenetic mechanisms of disturbed hepatic metabolic processes, such as hypoglycemia during cancer in human liver.

Expression of MUC1 recognized by monoclonal antibody MY.1E12 is a useful biomarker for tumor aggressiveness of advanced colon carcinoma

To address the need for new prognostic parameters in advanced colon carcinoma that could add insights into the aggressiveness of tumors, the expression levels of MUC1 recognized by a monoclonal antibody (mAb) MY.1E12 in archival specimens from 123 Japanese patients with colon carcinomas were evaluated by immunohistochemistry to correlate the results with clinicopathological characteristics. The localization of mAb MY.1E12-reactive-MUC1 (MY.1E12-MUC1) was classified into apical, cytoplasmic and stromal types based on the predominant cellular distribution. The MUC1 mRNA levels revealed by in situ hybridization were not a determinant for the localization types of MY.1E12-MUC1. Immunostaining of MY.1E12-MUC1 was recognized in the cancerous epithelia of pT1 carcinoma in 61%, pT2 in 78%, pT3 in 98% and pT4 in 90% of the cases at the deepest invading sites. At the deepest invading sites, apical-type localization was found to predominate in pT1 carcinoma, but stromal-type localization was found to increase in pT2-4 carcinomas in parallel with the depth of invasion. The frequency of synchronous distant organ metastasis at the time of diagnosis tended to be higher in cases of pT3 and pT4 carcinomas in the stromal-type localization-dominant group than in cases in the apical-type localization-dominant group. The post-surgical survival outcome of cases of pT3 and pT4 carcinomas was significantly poorer in the former than in the latter (P = 0.002). The stromal-type localization of MY.1E12-MUC1 may be a phenotype serving as a unique biological feature associated with the tumor aggressiveness of advanced colon carcinoma.

Expression of UDP-N-acetyl-alpha-D-galactosamine-polypeptide N-acetylgalactosaminyltransferase isozyme 3 in the subserosal layer correlates with postsurgical survival of pathological tumor stage 2 carcinoma of the gallbladder

PURPOSE AND EXPERIMENTAL DESIGN

Little is known about the molecular events leading to the development and progression of pathological tumor stage 2 (pT(2)) gallbladder carcinoma. An alteration in the site of O-glycosylation may be associated with malignant behavior of carcinoma cells by modulation of the biological properties of the target mucin. The UDP-N-acetyl-alpha-D-galactosamine-polypeptide N-acetylgalactosaminyltransferase isozyme 3 (GalNAc-T3) has the epithelial gland-specific expression and catalyzes mucin-type O-glycosylation. In this study, immunohistochemistry was performed to determine the expression level of GalNAc-T3 in 34 cases of pT(2) gallbladder carcinoma to determine the correlation of the GalNAc-T3 expression level with mode of recurrence and postsurgical survival.

RESULTS

The expression levels of GalNAc-T3 protein and mRNA were increased in gallbladder carcinomas compared with the levels in adjacent noncancerous tissues and in intact gallbladders. Immunostaining of GalNAc-T3 was recognized in the cancerous epithelia, and the subcellular localization was classified into granular and diffuse types. In the 34 cases of pT(2) carcinoma, the localization of GalNAc-T3 was granular type in 50% and diffuse type in 50% of the cases at the deepest invading sites in the subserosal layer. Postsurgical recurrence was significantly more frequent in cases showing diffuse-type localization of GalNAc-T3 at the deepest invading sites (65%) than in those showing granular-type localization (23%; P < 0.05). Postsurgical survival was significantly poorer in cases showing diffuse-type localization than in those showing granular-type localization (P = 0.033)

CONCLUSIONS

In pT(2) gallbladder carcinoma, the presence of diffuse-type localization of GalNAc-T3 in the subserosal layer is correlated with aggressiveness of the disease. This phenotype may serve as a unique biological feature associated with the malignant behavior.

Down regulation of endothelial adhesion molecules in node positive breast cancer: possible failure of host defence mechanism

Endothelial cell adhesion molecules (CAMs) are important in tumorigenesis and host defense mechanism. Their status in breast cancer with regard to nodal invasion is not yet known. Hence we looked at the expression of three important CAMs: VCAM, ICAM and E-selectin. A downregulation of all these CAMs was noted in node positive breast cancer in comparison to node negative cases. This suggests shedding of these molecules in cases with nodal metastasis which might help the tumor cells to escape the host defense mechanism. On multi-variate analysis, VCAM alone emerged as an independent predictor of nodal metastasis.

Increased expression of a nucleolar Nop5/Sik family member in metastatic melanoma cells: evidence for its role in nucleolar sizing and function

F10 and BL6 cells of B16 mouse melanoma cells are metastatic after intravenous injection, but only BL6 cells can metastasize to lungs after subcutaneous injection. Differences in gene expression between the two cell lines were examined, and a greater expression of the Sik-similar protein (Sik-SP) gene was found in BL6 cells. Structurally, Sik-SP belongs to the nucleolar Nop5/Sik family whose members play central roles in ribosome biogenesis; however, the function of Sik-SP has not been examined. Cytology with green fluorescent protein-fused proteins showed that Sik-SP was localized to the nucleolus. To examine whether Sik-SP is involved in ribosome biogenesis, two parameters were measured: magnitude of ribosomal RNA synthesis per nucleus and magnitude of protein production from the same amount of mRNA of an exogenous luciferase gene. Both values and, in addition, nucleolar size were larger in COS-7 monkey kidney cells overexpressing Sik-SP and BL6 cells than in mock-transfected COS-7 and F10 cells, respectively. Sik-SP seemed to promote ribosome biogenesis in the nucleolus. Furthermore, the expression of Sik-SP seemed to confer a greater cell growth response to serum, because such a response was greater in BL6 cells and F10 cells overexpressing Sik-SP than in untreated and mock-transfected F10 cells. Sik-SP may render melanoma cells more competent to survive through augmenting the activity of nucleolus.

Antioxidants inhibit TNFalpha-induced motility and invasion of human osteosarcoma cells: possible involvement of NFkappaB activation

Osteosarcoma is the most frequent malignant bone tumor in children. It is highly invasive, however, the mechanisms behind osteosarcoma cell invasion are as yet still unknown. In the present study, treatment with TNFalpha enhanced the invasiveness of two human osteosarcoma cell lines, OST and MNNG. TNFalpha treatment also induced tumor cell motility, adhesion to laminin, the expression of matrix metalloproteinase 9 (MMP9), and the nuclear translocation of nuclear factor kappaB (NFkappaB) in the osteosarcoma cells. Moreover, antioxidants inhibited TNFalpha-induced osteosarcoma cell invasion, motility and NFkappaB nuclear translocation, but not adhesion to laminin or MMP9 expression. NFkappaB decoy, another NFkappaB inhibitor, also inhibited TNFalpha-induced osteosarcoma cell invasion and motility. Therefore, motility and NFkappaB activation were possibly related to TNFalpha-induced osteosarcoma cell invasion. However, adhesion to laminin or MMP did not demonstrate any correlation with TNFalpha-induced osteosarcoma cell invasion. Although NFkappaB is known to regulate TNFalpha-induced phenotypes, it may influence only motility and invasion, but not the MMP or laminin-mediated adhesion of these osteosarcoma cells.

Expression of MUC1 mucins inversely correlated with post-surgical survival of renal cell carcinoma patients

Surgical specimens of the normal kidney and of renal cell carcinoma (RCC) tissues at different stages of progression and of various histological grades were examined for the expression of MUC1 mucins with sialylated carbohydrates (sialylated MUC1 mucins) using a monoclonal antibody MY.1E12. Immunohistochemical studies revealed that the binding sites for this antibody were localized to the apical side of the epithelial cells of the distal convoluted tubules, Henle's loops and collecting ducts. However, proximal convoluted tubules, where RCC is considered to originate, were not stained. This antibody also bound strongly to RCC at advanced stages of progression and at metastatic sites, and to RCC of histologically high grades (undifferentiated). The epitope, presumably sialylated MUC1 mucin, was detected not only along the surface of the cell membranes but also in the cytoplasm. The level of expression of sialylated MUC1 mucins was inversely correlated with the survival of the patients with RCC and the disease-free survival period after curative surgery. Western blot analysis demonstrated that the electrophoretic mobility of sialylated MUC1 mucins of RCC was greater than that from the normal kidney. It is suggested that high levels of expression of sialylated MUC1 mucins in certain human RCC populations correlate with the aggressiveness of the disease, such as the tendency to form metastasis.

Alterative expression of the collagenase and adhesion molecules in the highly metastatic clones of human colonic cancer cell lines

Human colonic carcinoma cell lines, KM12C, KM12SM and KM12L4, were previously established and their in vivo metastatic potentials have been well evaluated. The highly metastatic cell lines KM12SM and KM12L4 were derived from the parental low metastatic cell line KM12C in vivo. To evaluate the metastatic behavior of these cell lines in vitro, we examined colony formation on monolayers of the pulmonary arterial endothelial (CPAE) cells. On day 4, the highly metastatic cell lines showed an approximately 2-fold increase in number of colonies on CPAE cell monolayers relative to the parental KM12C cell line. To investigate what evidence is correlated with their metastatic and invasive abilities, Northern blot analysis and flow cytometry were performed in all cell lines. According to the results of Northern blot analysis, the levels of matrix metalloproteinase (MMP)-2 and c-met mRNA expression were increased in highly metastatic cell lines as compared with the parental cell line. We also examined the cell-surface expression of several adhesion molecules by flow cytometry. The levels of expression of sialyl Lewisa antigen (sLe(a)) in KM12SM and KM12L4 were twice higher than that in KM12C. However, the levels of expression of E-cadherin in KM12SM and KM12L4 were decreased to half that in KM12C. The alterative expression of the collagenase and adhesion molecules might contribute to their metastatic/invasive abilities of these cell lines both in vivo and in vitro.

Inhibitory effects of malotilate on invasion and metastasis of rat mammary carcinoma cells by modifying the functions of vascular endothelial cells

Malotilate (diisopropyl,1,3-dithiol-2-ylidenemalonate, MT) is clinically used as a hepatoprotective agent. Because we noticed that MT induced the differentiation of cultured vascular endothelial cells, we have examined its effects on lung metastasis of the highly metastatic rat mammary carcinoma c-SST-2. MT was orally administered to syngeneic SHR rats from 7 days before or after s.c. inoculation of c-SST-2 cells to the end of the experiments. In the MT-treated rats, pulmonary metastasis was markedly suppressed compared with the non-treated rats. In the rats treated with MT for 19 days after i.v. inoculation of c-SST-2 cells, lung metastasis was also significantly suppressed. An in vitro invasion assay using a rat lung endothelial (RLE) cell monolayer revealed that pretreatment of the RLE cells with MT, but not c-SST-2 cells, significantly reduced the invasion of the RLE monolayer by c-SST-2 cells. An in vitro vascular permeability assay demonstrated that MT prevented the increase in permeability of the RLE monolayer by serum starvation. On the other hand, in vivo and in vitro growth, gelatinase production and adhesion to the RLE cell monolayer of c-SST-2 cells were not affected by MT treatment. These findings suggest that MT suppressed tumour metastasis by intensifying the cell-to-cell contact of endothelial cells, thus preventing tumour cells from invading vascular endothelium.

Down-regulation of focal adhesion kinase, pp125FAK, in endothelial cell retraction during tumor cell invasion

Although endothelial cell retraction is required before tumor cell invasion, its molecular mechanism still remains obscure. We previously demonstrated that conditioned medium (CM) derived from a human pancreatic cancer cell line, PSN-1, induced endothelial cell retraction and facilitated tumor cell invasion. To investigate the molecular change of events in the transduction of extracellular signals during endothelial cell retraction, we examined the effect of the CM derived from PSN-1 cells on the tyrosine phosphorylation in endothelial cells. Immunoblot analyses revealed that the PSN-1 CM decreased tyrosine phosphorylation of a 120-130 kD protein, and induced the concomitant down-regulation of focal adhesion kinase, pp125FAK, during endothelial cell retraction in time- and dose-dependent fashions. These changes preceded endothelial cell retraction and were reversible after removal of the CM. Further quantitative densitometric analyses demonstrated that the extent of decrease in tyrosine phosphorylated 120-130 kD protein during the endothelial cell retraction was likely to be proportional to that of the down-regulation of pp125FAK. A tyrosine phosphorylated 120-130 kD protein immunoprecipitated by anti-phosphotyrosine antibody immunoreacted with anti-pp125FAK antibody. These results suggested that decreased amount of a tyrosine phosphorylated 120-130 kD protein probably due to the down-regulation of pp125FAK might be associated with the signal transduction pathway in the endothelial cells during their retraction. Furthermore, these findings were also observed in the CM from another four human cancer cell lines, suggesting the down-regulation of pp125FAK in endothelial cells during tumor cell invasion.

All-trans-retinoic acid-dependent inhibition of E-cadherin-based cell adhesion with concomitant dephosphorylation of beta-catenin in metastatic human renal carcinoma cells

We previously described an in vitro invasion assay model, using a monolayer of vascular endothelial cells grown on collagen gel, that mimics the metastatic abilities of the highly metastatic human renal carcinoma cell lines, MM-1,3 and 8 and their poorly metastatic counterparts, SN12C and Cl-8. MM-1, 3 and 8 cells were observed to penetrate the monolayer of vascular endothelial cells and grew in a spreading or scattering manner with loose cell-cell contact on collagen gel or on vascular endothelial cells. SN12C and Cl-8 cells failed to penetrate and grew in a clustering manner with tight cell-cell contact. Treatment with all-trans-retinoic acid (ATRA) at non-toxic concentrations induced clustering or growth of MM-1, 3 and 8 cells on collagen gel or on vascular endothelial cells with tight cell-cell contact, and inhibited penetration. The clustering induced by ATRA was virtually blocked in the presence of anti-E cadherin antibody. E-Cadherin and beta-catenin were each localized mainly at the cell-cell adherent junctions of colonizing cell populations that had been treated with ATRA. While the cellular levels of E-cadherin and beta-catenin did not change significantly following ATRA treatment, the tyrosine residue of beta-catenin was rapidly dephosphorylated. The concomitant administration of Na vanadate, an inhibitor of tyrosine dephosphorylase, inhibited both the ATRA-induced clustering and the dephosphorylation of beta-catenin tyrosine. ATRA-induced clustering of MM-3 cells may be linked to the state of tyrosine phosphorylation of beta-catenin.

Increased sialyl Lewis A expression and fucosyltransferase activity with acquisition of a high metastatic capacity in a colon cancer cell line

A human colon cancer cell line, OCUC-LM1(LM), was established from a liver metastasis in our laboratory. Intrasplenic injection of LM into nude mice was repeated three and five times, and the daughter cell lines were designated as LM-H3 and LM-H5 respectively. The level of sialyl Lewis A (SLA) in the supernatant of LM-H3 and LM-H5 was 3 and 4.5 times higher than that of LM respectively. Flow cytometric analysis of SLA expression showed that the peak channel for LM was 113; for LM-H3, 126; and for LM-H5, 146. The mean fluorescence intensity of LM was 102.3 +/- 43.5; for LM-H3, 126.2 +/- 28.4; and for LM-H5, 144.8 +/- 23.4. In endothelial cell adhesion assays, the percentages of adherent LM-H3 and LM-H5 cells were significantly higher than for LM. The activity of alpha1-->4 fucosyltransferase was higher in LM-H3 and LM-H5 than in LM, but there was no difference in alpha2-->3 sialyltransferase activities for type 1 chain among the cell lines. Our results suggest that SLA expression is associated with acquisition of a high capacity for liver metastasis of colon cancer; increased SLA expression is due mainly to increased fucosyltransferase activity.

Effects of ionizing radiation on the adhesive interaction of human tumor and endothelial cells in vitro

A centrifugation assay was used to determine the effects of ionizing radiation on the adhesive interaction of A549 human lung adenocarcinoma tumor cells and human umbilical vein endothelial cells (HUVEC). The tumor cells were fluorescently labeled and divided into control (sham-irradiated) and irradiated groups. The irradiated groups were exposed to irradiation levels ranging from 5 to 20 Gy using a 137Cs source. A specified number of these A549 tumor cells were then delivered into each well of 96-well cell culture plates containing confluent monolayers of human umbilical cord vein endothelial cells (HUVEC), and were given time to adhere to the endothelial cells. The wells were then sealed and were exposed to an acceleration field varying from 1 to 42 g (0-500 rpm) for 10 min. Finally, the wells were drained, and the number of tumor cells adhering to the endothelial monolayer were counted using a fluorescent microscope system. Our results indicate that the irradiation of A549 tumor cells significantly increased their adhesive interaction with endothelial cells (number of adhering irradiated cells/number of adhering control cells = 1.0, 1.3, 1.9, 2.2 for 0, 5, 10, 20 Gy respectively). In contrast, when endothelial cells were irradiated, rather than tumor cells, adhesive interaction decreased with an increase in the radiation dose (irradiated/control = 1.0, 0.9, 0. 8, 0.5 for 0, 5, 10, 20 Gy respectively). Simultaneous irradiation of both the tumor cells and the endothelial cells did not alter their adhesive interaction significantly. These findings may have important implications for the metastatic ability of irradiated tumor cells.

Dissection of tumour and host cells from target organs of metastasis for testing gene expression directly ex vivo

We report on a new methodology which allows the direct analysis ex vivo of tumour cells and host cells (lymphocytes, macrophages, endothelial cells) from a metastasised organ (liver or spleen) at any time point during the metastatic process and without any further in vitro culture. First, we used a tumour cell line transduced with the bacterial gene lacZ, which permits the detection of the procaryotic enzyme beta-galactosidase in eukaryotic cells at the single cell level thus allowing flow adhesion cell sorting (FACS) analysis of tumour cells from metastasised target organs. Second, we established a method for the separation and enrichment of tumour and host cells from target organs of metastasis with a high viability and reproducibility. As exemplified with the murine lymphoma ESb, this new methodology permits the study of molecules of importance for metastasis or anti-tumour immunity (adhesion, costimulatory and cytotoxic molecules, cytokines, etc.) at the RNA or protein level in tumour and host cells during the whole process of metastasis. This novel approach may open new possibilities of developing strategies for intervention in tumour progression, since it allows the determination of the optimal window in time for successful treatments. The possibility of direct analysis of tumour and host cell properties also provides a new method for the evaluation of the effects of immunisation with tumour vaccines or of gene therapy.

An in vitro invasion model for human renal cell carcinoma cell lines mimicking their metastatic abilities

We developed a modified in vitro invasion assay system using monolayers of vascular endothelial cells. A type I collagen gel was formed in plastic dishes, and overlaid with type IV collagen. Calf pulmonary arterial endothelial (CPAE) cells were seeded onto these plates, and incubated until they reached confluence. Five human renal cell carcinoma cell lines with various metastatic potentials in vivo were then seeded on the monolayer CPAE cells, and their colony formation and invasion activities were examined for 9 days. At day 4, the highly metastatic cell lines increased the number of colony foci on monolayer CPAE cells several fold higher than their poorly metastatic counterpart. The horizontal spreading patterns were also different between poorly and highly metastatic cell lines. On day 9, the number of carcinoma foci that penetrated the monolayer of CPAE cells and type IV collagen sheets into type I collagen gels in highly metastatic cell lines greatly increased as compared with that of poorly metastatic cell lines. Our in vitro invasion assay using monolayer CPAE cells would be useful to evaluate protease activities and colony formation during invasion.

Inhibition of colony formation in agarose of metastatic human breast carcinoma and melanoma cells by synthetic glycoamine analogs

We studied the influence of 10 synthetic glycoamine analogs on colony formation in 0.3 and 0.9% agarose by metastatic human breast carcinoma (MDA-MB-435) and melanoma (TXM-13) cells. Nine synthetic analogs significantly inhibited the colony formation in 0.9% agarose of MDA-MB-435 human breast carcinoma cells; five compounds caused a 73-83% reduction of colony formation. Seven synthetic glycoamines caused a significant inhibition of colony formation in 0.9% agarose by TXM-13 melanoma cells with the inhibitory effect ranging from 71 to 87%. The 50% inhibition (I50) doses and relative activity rank of the compounds were similar for both breast carcinoma and melanoma cell lines. The murine B16 melanoma cell aggregation assay was employed to elucidate the potential mechanism(s) of the inhibitory activity of synthetic glycoamines. The relative activity ranks of the compounds based on the independently determined I50 doses for both cell aggregation and clonogenic growth assays were very similar for the four most active synthetic analogs and clearly indicated the importance of hydrophobic amino acid in mediating the bioactivity of synthetic glycoamines. In both experimental systems (clonogenic growth in agarose and cell aggregation assay) the leading compound was N-(1-deoxy-D-fructos-1-yl)-D-leucine (Fru-D-Leu) and the least active analog was N-(l-deoxy-D-fructos-1-yl)-glycine (Fru-Gly). These results show that synthetic glycoamines may act by competing for specific carbohydrate-lectin interactions, particularly those involving beta-galactoside-specific lectins expressed on metastatic cells.

Effect of in vivo activation of natural killer (NK) cells by a tilorone analogue on the survival of mice injected intravenously with different experimental murine tumours

We studied the effect of a tilorone analogue (RMI 10,874DA) and anti-asialo GM(1) serum on the survival of BALB/c and C57B1/6 mice after i.v. injections of different syngeneic murine tumour cells. Tumour lines used were different clones from chemically (GR9 wild type, GR9.B9, B7.1.B4, B7.1.B5, B7.2.38), and ultraviolet light (GRUV3)-induced sarcomas; B16 melanoma and LSTRA and YC8 lymphomas. Pretreatment of mice with tilorone inhibited metastatic colonization and increased survival significantly in all cases. In some tumour systems, the effect was attenuated when high numbers of cells were injected. Abrogation of NK cells with anti-asialo GM(1) serum significantly decreased (in all tumours and at different cell doses) survival in comparison with untreated mice injected with tumours, regardless of cell dose used. These results clearly suggest that NK cell activation in vivo by the tilorone analogue we tested prolongs survival and inhibits metastasis formation in mice, even when pretreatment consists of a single dose of the analogue.

Evaluation of metastatic ability at specific times during primary tumor growth: a novel spontaneous metastasis assay

A transformed NIH 3T3 fibroblast cell line, Cl-e, normally does not produce spontaneous metastasis from subcutaneous or footpad tumors in nude mice. However, pulmonary tumor nodules are formed when more than 1 x 10(3) cells are injected intravenously into nude mice. Co-injection of 1 x 10(6) heavily irradiated and inactivated cells increases the clonogenic ability of the viable cells in that tumor colonies then occur with as few as 1 x 10(2) viable cells. Utilizing the action of these inactivated cells to enhance the lung colonizing ability of a relatively small number of viable tumor cells, we have developed a novel experimental model of spontaneous metastasis. In this model, a footpad tumor of the nude mouse metastasizes to the lungs following intravenous injection of 1 x 10(6) inactivated cells at a specific time of tumor growth and following tumor foot amputation, whereas no spontaneous metastasis develops without injection of inactivated cells. This model enables us to detect metastatic ability which would otherwise be too low to detect using other assays. In addition, it allows us to evaluate metastatic ability at a specific time point during primary tumor growth, since no metastases can develop during the periods before inactivated cell injection and after tumor amputation. Using this model, we have determined that the metastatic ability of Cl-e tumors in the footpad is constant throughout the exponential and stationary growth phases, even though cells isolated from exponentially growing tumors possess a 3.3-fold greater lung colonizing ability following intravenous injection than those from stationary tumors. This new experimental model may be applicable to other tumor cell lines and to other analyses where metastatic ability during a defined interval of tumor growth is of importance.

Tobacco smoke tumor promoters, catechol and hydroquinone, induce oxidative regulation of protein kinase C and influence invasion and metastasis of lung carcinoma cells

Cigarette smoke polyphenolic agents (catechol and hydroquinone) that generate oxidants have been shown to be tumor promoters. Furthermore, oxidants can influence protein kinase C (PKC)-mediated signal transduction. Since terpenoid tumor promoters, phorbol esters, increase invasion and metastasis by activating PKC, we have determined whether polyphenolic agents present in the cigarette smoke condensate (CSC) could also influence these events. Hydroquinone (50 microM), catechol (500 microM), or CSC (50 micrograms/ml) induced an initial cytosol-to-membrane translocation of PKC in LL/2 lung carcinoma cells, followed by a later down-regulation of the enzyme. LL/2 cells treated with these CSC-related agents for a limited time (45 min) and exhibiting high membrane-associated PKC activity, when injected into mice through the tail vein, produced an increase in metastatic nodules in the lungs after 20 days. However, cells treated with CSC-related agents for a prolonged period did not exhibit an increase in metastasis. Agents that decrease the rate of production of reactive oxygen species, such as catalase either alone or in combination with superoxide dismutase, and a cell-permeable iron-chelator, o-phenanthroline, inhibited CSC-mediated membrane association of PKC and metastasis. Prior treatment of CSC with tyrosinase to modify polyphenols resulted in a partial loss of CSC stimulation of metastasis. Furthermore, a cell-permeable Ca2+ chelator and diverse PKC inhibitors, such as calphostin C, hypericin, chelerythrine, and bisindolylmaleimide, inhibited CSC-enhanced metastasis. CSC increased in vitro tumor cell adhesion to endothelial monolayers and to reconstituted basement membrane (Matrigel) and also enhanced the invasion through Matrigel coated on the polycarbonate filters in Transwells. All these CSC effects were found to be temporary and were blocked by the above mentioned antioxidant systems and PKC inhibitors. Thus, these results suggest that the oxidants generated by autooxidation of polyphenolic agents present in tobacco smoke increase tumor cell invasion and metastasis, at least in part by activation of Ca2+/PKC signal transduction. Conceivably, cigarette smoke constituents not only promote tumorigenesis but also may increase the spread of cancer in the body.

In vitro assay of the invasive potential of malignant bone and soft tissue tumours through basement membranes

We have used reconstituted basement membrane molecules which have formed into barriers in order to investigate the invasive potential of malignant bone and soft tissue tumour cells in vitro. A number of cell lines established from human malignant tumours demonstrated a high degree of invasiveness, although fibroblasts showed no ability to penetrate the basement membrane barrier. H-ras oncogene transfected cells into the fibroblasts were much more invasive than the parent lines. Primary cultures of malignant tumour cells demonstrated invasiveness, while those of nonmetastatic cells and fibroblasts did not. The binding of tumour cells to laminin in the basement membranes was found to induce secretion of collagenase and motility which are crucial factors for invasion. A synthetic peptide, Tyr-Ile-Gly-Ser-Arg, was able to suppress the invasiveness of HT1080 human fibrosarcoma cells, and also reduced lung colonisation in vitro. The results suggest that the in vitro assay was useful, firstly to determine the invasive potential, secondly to investigate the mechanism of invasion, and finally to development treatment against invasion and metastases.

Selection for enhanced adhesion to microvessel endothelial cells or resistance to interferon-gamma modulates the metastatic potential of murine RAW117 large-cell lymphoma cells

Poorly liver metastatic large-cell lymphoma RAW117-P cells were sequentially selected in vitro for increased adhesion to murine hepatic sinusoidal endothelial cells. After three or four sequential selections, the selected sublines showed increased rates of adhesion to target hepatic microvessel endothelial cells and increased formation of experimental metastases in the liver. However, the endothelial cell adhesion-selected RAW117 sublines were generally unstable and gradually lost their enhanced adhesive and metastatic properties during passage in culture. Highly metastatic, liver-selected RAW117-H10 large-cell lymphoma cells were more resistant to the cytostatic effects of interferon-gamma (IFN-gamma) than poorly metastatic unselected parental RAW117-P cells. When tested for their sensitivity to IFN-gamma, the endothelial cell adhesion variants were significantly more resistant than the unselected RAW117-P cells, but after a 72-h treatment with IFN-gamma, the in vitro-selected cells lost their enhanced endothelial cell adhesion characteristics, their potential to colonize the liver, and their ability to grow when injected at subcutaneous or intramuscular sites. In contrast, the metastatic potential of similarly treated RAW117-P cells was unaffected by IFN-gamma during a 72-h treatment. Sequential selection of RAW117-P cells for increased resistance to IFN-gamma in vitro resulted in variant lines that were refractory to the growth-inhibiting effects of IFN-gamma, and these IFN-gamma-selected variants were also less adhesive to liver microvessel endothelial cells. The IFN-gamma-selected variants also lost their experimental metastatic potentials completely and their tumorigenicities at sites of subcutaneous or intramuscular injection. Cytofluorographic analysis indicated reduced cell surface expression of H-2Kd antigen and fibronectin receptor on the selected variant cells but no change in cell surface mu heavy chain immunoglobulin. The unselected and selected RAW117 lines had similar sensitivities to natural killer (NK) cell-mediated cytolysis, indicating that the in vivo differences were probably not due to differences in NK cell-mediated cytolysis. The results suggest that selection for adhesion to organ microvessel endothelial cells or sequential exposure to certain cytokines can affect the adhesive, growth and metastatic properties of RAW117 cells without modifying their responses to NK cells.

Establishment and characterization of BALB/c retroperitoneal sarcoma with spontaneous liver metastases

The objective of this study was to examine the identity and characteristics of a spontaneously occurring murine retroperitoneal tumor of BALB/c mouse origin that selectively metastasized to the liver. From the primary tumor, a permanent cell line, termed LMFS (liver metastasis from sarcoma) was established in vivo and in vitro. After a subcutaneous injection of more than 1 x 10(5) cells in the side back of mice, the LMFS cells proliferated at the inoculation site (100% take) and induced metastatic nodules spontaneously in the liver, but not in the lung. By the limiting dilution technique, a cloned cell line, LMFS-1, was established in vitro. The LMFS-1 cell line had similar morphological characteristics to the LMFS cells both in vitro and in vivo. The doubling time of the LMFS-1 cell line was 10 h in passage 60. The number of chromosomes ranged from 71 to 108 and 93% of metaphases showed near-tetraploidy. In microscopic examination, no specific arrangement of the LMFS tumor cells was seen; the LMFS cell had medium- to large-sized atypical nuclei and clear and large cytoplasm. Electronmicroscopy showed that the cytoplasm of the LMFS cell had a moderate amount of rough-surfaced endoplasmic reticulum but no desmosomes or microvilli. Immunohistochemically, the LMFS cells were positive for vimentin, but showed no reaction for keratin or cytokeratin. Therefore, the LMFS tumor was considered to be an undifferentiated sarcoma. The LMFS cell line should be a useful tool not only for studies of metastasis, but also for experiments on the therapy of hepatic tumors.

Augmented expression of a type IV collagen-binding protein in a highly metastatic murine fibrosarcoma clone

The adhesive properties of highly and weakly metastatic murine sarcoma (Meth A) clones were investigated. A highly metastatic clone, MH-02, preferentially adhered to type IV collagen-coated plastic dishes and to bovine pulmonary arterial endothelial cell-coated plastic dishes as compared to a weakly metastatic clone, ML-01. Pretreatment of MH-02 and ML-01 cells with antisera against MH-02 cells resulted in almost equivalent adhesiveness to type IV collagen. Preincubation of 125I-radiolabeled tumor cells with the antisera against MH-02 significantly reduced the arrest of MH-02 cells in the lung, but ML-01 cells were not affected. The number of pulmonary metastatic nodules of MH-02 cells was reduced to the same level as that of ML-01 cells by preincubation of the tumor cells with the antisera in an experimental metastasis experiment. These results indicated that the high metastatic ability of MH-02 can be attributed to its preferential adhesiveness to type IV collagen. The type IV collagen-binding proteins of MH-02 and ML-01 were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and autoradiography. Among several proteins which bound to type IV collagen, expression of a protein with a molecular weight of 29 kD was significantly greater in MH-02 than in ML-01. These results suggest that the greater adhesion of highly metastatic MH-02 cells to type IV collagen is due to enhanced expression of the type IV collagen-binding 29 kD protein.

Interleukin 1-induced cancer cell/endothelial cell adhesion in vitro and its relationship to metastasis in vivo: role of vessel wall 13-HODE synthesis and integrin expression

Previously, we have demonstrated that stimulation of endothelial cells (ECs) with interleukin-1 alpha (IL-1 alpha) enhances the synthesis and expression of the vitronectin receptor (VnR), promotes VnR-dependent adhesion of human A549 adenocarcinoma cells to ECs, and is associated with decreased EC 13-hydroxyoctadecadienoic acid (13-HODE) synthesis in vitro. To determine whether these observations are relevant in vivo, we examined the acute retention and subsequent metastasis of intravenously-injected B16F10 melanoma cells in murine lungs, in relation to vessel wall 13-HODE. In C57BL/6 mice pretreated with IL-1 alpha, vessel wall 13-HODE was decreased and B16F10 lung entrapment and metastasis were increased. The latter two events were blocked by pretreating the animals with the GRGDS peptide. These data suggest a relationship between vessel wall 13-HODE synthesis, adhesion molecule expression, and adhesion of B16F10 cells to the endothelium.

Electrophoretic heterogeneity of pigmented hamster melanoma cells

Pigmented hamster melanoma tumors growing in situ contain two subpopulations of melanoma cells that have different electrophoretic mobilities (EPM). A mild neuraminidase treatment, which removes sialic acid residues from the cell surface glycoproteins, reduces the EPM of both groups of melanoma cells yielding an electrophoretically uniform population. This shows that the differences in the EPM between the subpopulations of pigmented melanoma cells stem from the different content of sialic acid residues on the cell surface. The relationship between the different EPM melanoma cell subpopulations was, therefore, examined during tumor growth, development, and formation of metastases. The relative content of cells having high electrophoretic mobility, the "fast moving" cells, increases as the tumors grow larger. However, tumors of the same diameter contain nearly the same fraction of "fast moving" cells despite their age. The proportion of the "fast moving" cells is significantly higher in the central part than in the outermost layer of pigmented melanoma tumors. These data suggest that the development of "fast moving" cells is promoted by some size-dependent changes in the intratumor environment. In vivo selection of melanoma cells for their ability to colonize lungs renders tumors that reveal elevated metastatic potential and contain a significantly higher fraction of cells possessing high electrophoretic mobility than the parent tumor. Moreover, the metastatic nodules contain a remarkably elevated fraction of the "fast moving" cells. The reported correlation between the "fast moving" cell fraction and the metastatic potential suggests that the relative content of cells having high electrophoretic mobility may determine the metastaticity of pigmented hamster melanoma.

A serine protease-inhibitory benzamidine derivative inhibits the growth of human colon carcinoma cells

The inhibitory effect of a serine protease-inhibiting tetra-benzamidine derivative, TAPP-Br, on the cell growth of 8 human colon carcinoma cell lines was examined and the mechanism of the inhibition was analyzed. TAPP-Br inhibited the cell growth of all the colon carcinoma cell lines, and this effect was irreversible. The expression of mRNAs for nuclear oncogenes such as MYC, FOS and JUN was decreased by TAPP-Br after treatment for 3 h and the effect continued for 48 h. mRNA expression of epidermal growth factor receptor, transforming growth factor-beta and type IV collagenase was suppressed at 48 h after the initiation of TAPP-Br treatment, suggesting an indirect action of TAPP-Br. TAPP-Br decreased protein kinase C activity in the particulate fraction, whereas it increased the enzyme activity in the soluble fraction. These findings overall suggest that the serine protease inhibitor, TAPP-Br, might inhibit the cell growth of colon carcinoma cell lines through suppressing the expression of genes whose promoter contains a 12-O-tetradecanoylphorbol-13-acetate-responsive element or serum-responsive element.

Cell-to-cell communication competence in simian virus 40-transfected rat ovarian cells is reduced following tumor selection

A pSV3neo-transfected rat ovarian cell line (SV-GC) was developed from a primary granulosa culture (GC) to study gap junctional intercellular communication (GJIC) during Simian virus 40 (SV40) transformation. SV-GC expressed SV40 large T-antigen (T-ag), grew indefinitely in culture without luteinization, was anchorage independent, and formed tumors in nude mice. Ultrastructural analysis identified abundant gap junctional membrane and suggested that SV-GC was arrested at an early stage of differentiation. Functional GJIC, measured by a dye transfer technique (gap FRAP), was comparable to that observed in normal granulosa cells, suggesting that the expression of T-ag alone was insufficient to reduce GJIC. However, there was approximately a 50% loss in the rate of GJIC in the nude mouse SV-GC-tumor derived and G418 selected cell line (T-SV-GC). SV-GC----T-SV-GC also resulted in a transition from migration of cells as an epithelial sheet to the dissociation of individual fibroblastoid cells. Tumor cell detachment was also seen in migrating malignant human (A2780 and 547) and rat (DC3) ovarian cell lines. Co-culture combinations of normal (GC)----transformed (SV-GC)----tumor-derived (T-SV-GC) cells indicated that the rate of heterologous GJIC was characteristic of the least communicating partner. Taken together, these data suggested that SV-GC----T-SV-GC represented progression toward metastasis with concomitant reduction of GJIC and adhesiveness. These sequentially derived cell lines may be a useful in vitro model system for studies focusing on the mechanism involved in the detachment of cells during the progression of ovarian cancer.

Inhibitory effect of antimetastatic fusion polypeptide of human fibronectin on tumor cell adhesion to extracellular matrices

We investigated the inhibitory mechanism of liver metastasis by using recombinant fragments with cell- and/or heparin-binding domains (C-274, H-271 or the fusion fragment CH-271). Intravenous co-injection of L5178Y-ML25 cells with CH-271 was more effective for the inhibition of liver metastasis than C-274, H-271 or C-274 + H-271. Reduction of the arrest and retention of the radiolabeled tumor cells in the liver of mice was found when CH-271 was co-injected with tumor cells. L5178Y-ML25 cells adhered both concentration- and time-dependently to the substrates precoated with fibronectin, laminin and reconstituted basement membrane, Matrigel. The tumor cell adhesions to the substrates were inhibited in the presence of CH-271. The tumor cell interaction with CH-271-substrate was inhibited by heparin, and monoclonal antibodies (IST-1 or IST-2) against the heparin-binding domain of fibronectin. However, monoclonal antibodies against the cell-binding domain failed to block the interaction. Similarly, CH-271-mediated antimetastatic activity was also inhibited by the treatment of CH-271 with IST-1 before the co-injection with tumor cells, whereas monoclonal antibody against the cell-binding domain had no effect. Thus, the antimetastatic effect of CH-271 fusion fragment on liver metastasis of L5178Y-ML25 cells may be partly due to interference with the adhesive interaction of tumor cells with extracellular matrix or basement membrane components by a heparin-binding domain-dependent mechanism.

Establishment and characterization of a new spontaneous metastasis model of human gastric carcinoma in nude mice

A poorly differentiated medullary carcinoma of human stomach, designated HY-1, was successfully transplanted to nude mice by either the subcutaneous or intramuscular route for five generations. The transplanted tumor showed spontaneous lung metastases in nearly 100% of KSN and Balb/c female nude mice. There were over 20 visible lung metastatic nodules in KSN and Balb/c nude mice bearing tumors for over 80 days. Immunostaining of type IV collagen and electron microscopy revealed that tumor cells were often in direct contact with basement membrane (BM) of tumor blood vessels in the primary tumor tissue. At the site of contact between tumor cells and vascular BM, focal disappearance of the BM, disruption of endothelial cells and entry of tumor cell clusters into vascular lumen were observed. Immunostaining of 72 kDa gelatinase/type IV collagenase demonstrated that tumor cells expressed this enzyme in their cytoplasm. These results suggest that spontaneous metastasis of this tumor may be partly due to a marked tendency to vascular invasion involving the following sequential events: tumor cell contact with vascular BM, BM degradation possibly by 72 kDa gelatinases and endothelial disruption. This model could be a useful tool for understanding the mechanism of hematogenous metastasis of human gastric cancer.

Mucin production by human colonic carcinoma cells correlates with their metastatic potential in animal models of colon cancer metastasis

Patients with mucinous colorectal cancers characteristically present with advanced disease, however, the relationship between mucin production by colon cancer cells and their metastatic potential remains unclear. We therefore sought to define the relationship between mucin production by human colon cancer cells and metastatic ability by employing animal models of colon cancer metastasis. LS LiM 6, a colon carcinoma cell line with high liver metastasizing ability during cecal growth in nude mice produced twofold more metabolically labeled intracellular mucin and secreted four- to fivefold more mucin into the culture medium compared to poorly metastatic parental line LS174T. This was accompanied by a similar elevation in poly(A)+ RNA detected by blot hybridization with a human intestinal mucin cDNA probe, and increases in mucin core carbohydrate antigens determined immunohistochemically. Variants of LS174T selected for high (HM 7) or low (LM 12) mucin synthesizing capacity also yielded metastases after cecal growth and colonized the liver after splenic-portal injection in proportion to their ability to produce mucin. Inhibition of mucin glycosylation by the arylglycoside benzyl-alpha-N-acetyl-galactosamine greatly reduced liver colonization after splenic-portal injection of the tumor cells. These data suggest that mucin production by human colon cancer cells correlates with their metastatic potential and affects their ability to colonize the liver in experimental model systems.

Ultrastructure of invasion in different tissue types by Lewis lung tumour variants

Ultrastructural studies on the interactions of low and highly metastatic 3LL tumour lines with the basement membranes (BMs) of capillaries, veins, muscles, nerves and adipose tissue were performed by injecting tumour cells into the foot pad of mice. Haematogenous dissemination is the principle route of metastasis formation. Cells from the highly metastatic line were able to penetrate the blood vessels more efficiently than those from the low metastatic line. This difference was mainly due to a more pronounced diapedesis-like activity of the 3LL-HH cells, and partly to the altered intratumour vessel architecture in the highly metastatic tumour line. There was no difference between the two lines in the ultrastructure and frequency of invasion of nerves and adipose tissue BMs. However, in the highly metastatic line an extremely efficient penetration of muscle cell BM was observed. These results provide further evidence that the interaction of tumour cells with the BMs of different tissue types is one of the main determinants in local and distant dissemination.

Tumor progression: potential role of unstable genomic changes

It is generally accepted that the genome of tumor cells is less stable than that of most normal cells, and it has been hypothesized that this genomic instability is probably involved in the process of tumor progression. However, the rate of occurrence of classical spontaneous mutations in tumor cells is too low to account for the rapid changes that can occur during tumor progression. Thus it is likely that other types of changes, such as gene amplification, must be involved in tumor progression. Gene amplification has been extensively studied in relation to the development of drug resistance. Low levels of amplification can occur spontaneously in tumor cell populations, but the amplified genes are lost rapidly unless prolonged selective pressure is applied. This paper argues that unstable increases in the expression of genes, probably as a result of low levels of amplification, may be all that is required for some of the stages in the process of tumor progression. This may be particularly true for the steps involved in metastasis formation. Recent studies have suggested that microenvironmental conditions known to occur in tumors (hypoxia, nutrient deprivation) may induce gene amplification in cells. This suggests the possibility that such conditions could promote tumor progression.

Cellular interactions in metastasis

The metastatic cascade is a sequence of events that must be completed for metastases to be established. The realization that tumors are heterogeneous, consisting of many different subpopulations differing in many characteristics, and the belief that there are selective events in the metastatic process have led several laboratories to isolate and characterize variants with both high and low metastatic potential. Typically, the highly metastatic variants have been able to form distant metastases when implanted into the subcutis. Such lines have been popular for studies of metastatic mechanisms and anti-metastatic therapy, but they may be atypical examples, and thus not the best experimental models. Recent studies indicate that normal tissue influences metastasis such that many tumors metastasize only if placed in the orthotopic site. Furthermore, some cells that do not metastasize individually are able to do so in conjunction with other variant subpopulations. Thus, mixtures of tumor cells in the tissue of origin can express a more malignant character. We review possible mechanisms for such influential interactions, as well as the role of cellular interactions in generating heterogeneity and stabilizing tumor characteristics.

Adhesion of frog pronephric tumor cells to normal cells cultivated on microcarrier beads

The processes of cell adhesion and active spreading were assessed between frog normal pronephric, pronephric tumor and heterologous liver cells. Confluent monolayers were developed on collagen-coated microcarrier beads, then exposed to homologous or heterologous cells and cultivated with a rotary (orbital) flask culture technique at 23 degrees C. All three cell lines attach and actively spread on the collagen-coated microcarrier beads. Secondary attachment of normal (non-transformed) proliferating cells to their confluent monolayers occurs but cell spreading is restrained. Dissociated pronephric tumor cells adhere and actively spread on the surfaces of normal pronephric cells, and eventually encapsulate them. Normal pronephric cells do not adhere readily to the cell surfaces of pronephric tumor cells grown on microcarrier beads. Tumor cells also attach, actively spread and overgrow heterologous liver cells attached to microcarrier beads. Suboptimal temperatures (17 degrees C) slow tumor cell attachment and spreading on normal cells. Colder temperature (8 degrees C) permits tumor cell attachment and adhesion to normal cell-coated beads but active cell spreading is prohibited. The same temperature retards cell spreading directly on the collagen-coated beads.

Microvascular endothelial cell heterogeneity: interactions with leukocytes and tumor cells

Endothelium constitutes a highly specialized organ that lines the vascular system and lymphatic channels. This organ is a complex network of arteries, veins, and microvessels that differ in size, structure, and function. The unique and strategic location imposes functional demands on the endothelium that are far greater than just being a passive barrier. Endothelial cells have the ability to differentiate both in structure and function in response to the needs of diverse tissue environments, making this organ extremely heterogeneous. Although vascular endothelial cells share certain common properties, they differ in regard to structure, antigenic and cell surface determinants, adhesion molecules, and metabolic function. The unique cell surface profiles expressed by endothelial cells in different tissue locations can be recognized by specific populations of circulating leukocytes or tumor cells, which contribute to their arrest and invasion patterns. This article attempts to review our current understanding of endothelial cell heterogeneity and its significance to patterns of leukocyte and tumor cell trafficking.

Expression of human recombinant plasminogen activators enhances invasion and experimental metastasis of H-ras-transformed NIH 3T3 cells

The gene transfer technique was used to examine the role of plasminogen activator (PA) in the invasive and metastatic behavior of tumorigenic cells. H-ras-transformed NIH 3T3 clonal cells producing a very low level of PA were generated and further transfected with an expression plasmid containing a cDNA sequence encoding either the urokinase-type or the tissue-type human PA. Compared with the parental transformed cells, clonal cells expressing high levels of both types of recombinant PA invaded more rapidly through a basement membrane reconstituted in vitro. Furthermore, cells expressing high levels of recombinant urokinase-type PA also caused a higher incidence of pulmonary metastatic lesions after intravenous injection into nude mice. Both activities were reduced by the serine proteinase inhibitor EACA; invasion was also suppressed by antibodies blocking the activity of human PAs and by the synthetic collagenase inhibitor SC-44463. These findings provide direct genetic evidence for a causal role of PA in invasive and metastatic activities.