Oncogene ras p21- and v-src pp60-transformed cells exhibit altered expression of proteases

To evaluate the proteolytic activities of oncogene-transfected 3T3 cells, we have developed a copolymerized substrate electrophoretic assay that permits the detection of picogram quantities of proteases produced by cells in culture. Our assay involves a gelatin substrate copolymerized in a polyacrylamide gel. Purified cell membrane preparations were run on gels and various protease activities were detected by amido black. Ras-transfected 3T3 cells appear to have a soluble metalloprotease that may be transiently membrane bound and responsible for destruction of red blood cells (RBC). Oncogene-transfected NIH-3T3 cells have been demonstrated to have RBC cytolytic activity. We have previously shown that v-src-transfected 3T3 cells and their cell membranes cause RBC cytolysis which is inhibited by the protease inhibitor leupeptin. Here we report that both H-ras- and K-ras-transfected 3T3 cells and their cell membranes are cytolytic for RBC, but are inhibited by the metalloprotease inhibitor ethylene diamine tetraacetic acid. Using the gelatin substrate gel assay, we determined that some of the proteases were intrinsic to the oncogene expressing cells, while other proteases were secreted into the culture growth medium.     

Diversity of melanoma plasma membrane proteinases: inhibition of collagenolytic and cytolytic activities by minocycline

The tissue-destructive proteinases of B16-BL6 melanoma cells from C57BL/6 mice and subcellular fractions were examined. Cancer cell organelles were isolated following nitrogen cavitation with the use of sucrose density gradient centrifugation. Serine, cysteine, and metalloproteinases were assayed with the use of radiolabeled proteins and synthetic substrates. Tumor-induced red blood cell lysis was quantitated by measurement of the release of isotope from 59Fe-labeled red blood cells (RBC) cocultivated with melanoma cells; the RBC were from Wistar rats. Enzyme inhibitors with specificity toward different classes of proteinases were used in the above assays to categorize the enzymes responsible for substrate degradation. Results indicated that intact melanoma cells, cell organelles, and cytosol contain proteinases that can degrade collagen and gelatin and lyse normal RBC. Melanoma plasma membranes are highly enriched in collagenase, gelatinase, cysteine proteinase, plasminogen activator, and cytolytic activity. The inhibition of tumor collagenolytic, gelatinolytic, and cytolytic activities by EDTA and 1,10-phenanthroline but not by diisopropyl fluorophosphate and N alpha-p-tosyl-L-lysine chloromethyl ketone indicates that metalloproteinases are the active enzymes in these assays. Minocycline, a synthetic tetracycline with demonstrable inhibitory activity with other mammalian collagenases, also inhibited melanoma collagenolytic and cytolytic activities.     

Metastatic inefficiency in mice bearing B16 melanomas.

When injected i.v. into mice, the F10 subline of B16 melanoma cells produced significantly more lung tumours over a 3-week period than cells of the F101.r-6 subline. However, in animals bearing intramuscular tumours produced by these sublines, the high pulmonary-colonization potential of the F10 cells was not realized, and no significant differences in natural pulmonary metastasis formation were observed in animals with untreated primary cancers, even when they progressed to the moribund state. Massage of i.m. tumours derived from the two sublines produced no change in metastasis and no changes in the numbers of cancer cells in the blood detectable by bioassay. In contrast, massage increased metastasis from tumours derived from an invasive BL6 subline and B16 wild-type cells and, in the case of the wild-type, the numbers of circulating cancer cells. In vitro experiments show that blood cells from non-tumour-bearing animals are toxic to both sublines; but less to F10 than to F101.r-6. In addition, after i.v. injection of radiolabelled cells, more of the F10 subline were retained in the lungs of recipients than the F101.r-6. In spite of these apparent metastatic advantages of the F10 subline following intravasation, the incidence of natural metastases from i.m. F10 and F101.r-6 tumours was similar, suggesting that substantially fewer F10 than F101.r-6 cells gained access to the circulation. Thus, the higher colonization potential of the F10 cells was not matched by its intravasation potential, since metastatic efficiency is determined by the least efficient step in the metastatic process.     

Membrane gangliosides and immuno-mediated cytolysis in drug sensitive and treatment-induced multidrug resistant human ovarian cancer cells.

The pattern of cytoplasmic membrane gangliosides and two cellular features which have been reported to be related to the expression of different membrane gangliosides, namely adhesion to solid substrates and susceptibility to the lytic activity of immune effector cells, have been investigated in drug sensitive A2780 human ovarian cancer cells and in two treatment-induced multidrug resistant sublines (A2780-DX1 and A2780-DX3). The total membrane gangliosides content of A2780 sensitive cells was comparable to that of the two multidrug resistant (MDR) sublines, but the acquisition of the MDR phenotype was characterized by an increased expression of the polysialylated gangliosides (particularly the disialoganglioside GDIa) and decreased expression of the monosialoganglioside GM2. The kinetics of cellular adhesion (both to plastic culture dishes and to extracellular matrix coated dishes) were similar in the three cell lines, indicating that the gangliosides profile seems not to be relevant for cell adhesivity to the above mentioned substrates. When human peripheral blood lymphocytes in toto (PBL) and two lymphokine activated (LAK) T cell subpopulations (CD3+4-8- and CD3-16+) were used as effector cells against A2780 (sensitive) and A2780-DX3 (highly resistant) cells, cytolysis of target cells was more efficient against the A2780-DX3 subline, suggesting a possible role of the ganglioside GD1a as a target structure for LAK immunotherapy.     

Characterization in vitro and in vivo of progressively adriamycin-resistant B16-BL6 mouse melanoma cells

Adriamycin (ADR)-resistant sublines of B16-BL6 mouse melanoma selected by exposure to increasing concentrations of ADR were characterized in vitro for growth properties and in vivo for tumorigenicity and pulmonary metastases. The progressively resistant sublines adapted to grow in the presence of 0.025, 0.05, 0.1, and 0.25 microgram/ml ADR in monolayer culture were found to be 5-, 10-, 20-, and 40-fold ADR-resistant, respectively, compared to the parental sensitive cells, using a soft-agar colony assay and continuous ADR treatment for 7 days. The doubling time in monolayer culture of the parent sensitive and progressively ADR-resistant sublines of B16-BL6 melanoma cells was approximately 16-18 h. Although the colony-forming efficiency in soft agar of parental sensitive cells was only 0.5-4%, the 5-, 10-, 20-, and 40-fold ADR-resistant sublines had colony-forming efficiencies of 15, 20, 30, and 77%, respectively. Tumorigenicity in C57BL/6 mice of progressively ADR-resistant sublines was similar to parental sensitive cells following s.c. and i.p. implantation of 10(5)-10(6) tumor cells. Experimental pulmonary metastases were significantly lower in ADR-resistant sublines with progressive resistance. Additionally, unlike the parental sensitive and 5-fold ADR-resistant B16-BL6 cells, the 10-, 20-, and 40-fold ADR-resistant sublines were spontaneously nonmetastatic. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunochemical detection of P-glycoprotein revealed the presence of a Mr 170,000 plasma membrane glycoprotein in the 40-fold ADR-resistant subline and its counterpart maintained for 1 year in ADR-free medium. Results from this study suggest that progressively ADR-resistant B16-BL6 mouse melanoma cells selected in vitro demonstrate a marked increase in colony formation in soft agar and a decrease in the ability to produce pulmonary metastases, without alterations in tumorigenicity.     

Susceptibility of chemoresistant murine and human tumor cells to lysis by interleukin 2-activated lymphocytes

The sensitivity of three different human and murine doxorubicin (Dx)-sensitive or -resistant pairs of tumor cells to recombinant interleukin 2 (rIL2)-activated lymphocytes was studied. In two pairs of these sublines (LoVo human colon carcinoma and B16 mouse melanoma sublines), resistance to Dx was induced in vitro, while in the third pair (9229 human metastatic melanoma clones), Dx resistance was spontaneously present in clone 9229.24. Dx-resistant cells were efficiently lysed by rIL2-activated lymphocytes in a short-term 51Cr release assay; in some experiments a trend toward higher lysis of Dx-resistant cells was present. We then tested the tumor cell growth-inhibitory activity of rIL2-activated lymphocytes in the human tumor clonogenic assay after lymphocyte-tumor coculture. Complete inhibition of tumor cell growth was obtained with five of six sublines or clones (both Dx sensitive and resistant) after 3 to 6 days of coculture at effector lymphocyte/target tumor cell ratios of 5 to 50/1; a maximum 99% inhibition was observed with the melanoma clone 9229.4 even after coculture for 6 days at an effector lymphocyte/target tumor cell ratio of 50/1. By using lower effector lymphocyte/target tumor cell coculture ratios (1, 5, 25/1), it was shown that all the three Dx-resistant cell types were significantly more affected by activated lymphocytes than their Dx-sensitive counterparts. The LoVo/DX subline was also more lysed than its Dx-sensitive counterpart LoVo/H subline by an antitumor monoclonal antibody in a complement-mediated cytotoxicity assay, despite the fact that both sublines expressed a similar amount of antigen on the cell surface. These data indicate that Dx-resistant cancer cells are more susceptible to the lysis by rIL2-activated lymphocytes than their Dx-sensitive counterparts and that a complete inhibition of their clonogenic potential can be obtained in vitro.     

Expression of collagenase IV (basement membrane collagenase) activity in murine tumor cell hybrids that differ in metastatic potential

Expression of a basement membrane collagen-degrading metalloprotease activity (collagenase IV) was studied in a series of murine cell hybrids derived from fusions between highly metastatic cells (B16-F10RR) or moderately metastatic cells (UV-2237RR) and tumorigenic cells (K-1735 clone 16) or normal cells [peritoneal macrophages (PEC) or C3H mouse embryo fibroblasts (C3H-F)]. The collagenase IV activity of the parent cells and the hybrids was assayed in vitro and compared to the metastatic propensity of the same cells evaluated in both syngeneic (C57BL/6 X C3H/HeN)F1 mice and BALB/c nude mice. The level of collagenase IV activity secreted by the parent lines correlated with their metastatic capacity. The highly metastatic B16-F10RR line secreted the highest enzyme activity, whereas the tumorigenic but nonmetastatic K-1735 clone 16 and the normal parents PEC and C3H-F secreted the lowest enzyme activity. The enzyme activity was completely inhibited with EDTA. The hybrid derived from fusion of cells from two metastatic cell lines as well as hybrids derived from a metastatic and a nonmetastatic tumor cell line expressed higher levels of collagenase IV activity than either parent, and this expression was associated with a high ability to produce metastases in both nude and syngeneic mice. Fusion of metastatic cells with normal cells produced hybrid cells that exhibited suppression of both collagenase IV activity and metastatic capacity. Collagenase IV activity and metastatic propensity can, therefore, be altered by somatic cell hybridization; in the series of hybrids examined in these experiments the expression of type IV collagen-degrading metalloprotease activity and the metastatic ability were closely correlated, which suggests that collagenase IV activity and other properties required for metastasis are genetically linked.     

Differential sensitivity of two murine leukaemia sublines to cytolysis by Corynebacterium parvum-activated macrophages.

We observed the growth of 2 sublines of leukaemia L1210 in histocompatible DBA2 mice given 10(3) cells i.p. and studied the protective effect of Corynebacterium parvum (CP). The growth of subline L1210-M was unaffected by pretreatment with CP or admixture with 10(5) peritoneal cells (PC) from CP-treated mice. In contrast, the growth of subline L1210-C was inhibited; CP pretreatment increased the proportion of long-term survivors (70% vs 20%) and admixture with CP-PC prolonged the survival time (59 days vs 49 days; P less than 0.05). In vitro experiments indicated that Sublines M and C were equally sensitive to cytostasis by CP-PC, as measured in a terminal labelling assay (greater than 90% inhibition of proliferation). However, subline C was much more sensitive to cytolysis (18h 125IUDR-release assay) by CP-PC; percentage specific release from L1210-C was at least 90%, whilst from L1210-M it was generally less than 25%. The differential susceptibility of the 2 sublines to cytolytic PC was maintained through 75 passages in culture. The effector cells were considered to be macrophages, because they were adherent, phagocytic, and sensitive to silica. Cytolysis was unrelated to endotoxin contamination, because it was not inhibited by polymyxin B, and was inhibited by pre-incubating PC in culture medium for 24 or 48 h before adding target cells. Thus the relevance of nonspecific macrophage-mediated cytotoxicity in vitro to tumour resistance in vivo may depend on the strength of the cytotoxic reaction.     

Role of proteases in red blood cell target cell destruction by cells transformed by Rous sarcoma virus mutants

The tumor induced RBC cytotoxicity assay has been used to explore the mechanism by which Rous sarcoma virus mutant transformed chick embryo fibroblasts and mouse 3T3 cells cause the cytolysis of RBC in vitro. All Rous sarcoma virus and viral mutant transformed cells were cytolytic for RBC. Three mutant viruses, tsGl251, rASV1702, and rASV157, appeared to cause quantitatively less cytolysis after transformation of chick embryo fibroblasts than other virally transformed cells. This decreased cytolytic activity may be correlated with decreased in vivo tumorigenicity. Temperature sensitive mutant transformed chick embryo fibroblasts and mouse 3T3, which were phenotypically normal and which secrete little if any plasminogen activator at non-permissive temperatures, were cytolytic at non-permissive temperatures. In addition, inhibitors of plasminogen activator and plasmin were ineffective inhibitors of cytotoxicity. The only effective inhibitor of cytotoxicity for both transformed chick embryo fibroblasts and mouse 3T3 cells was leupeptin. In Rous sarcoma virus transformed mouse 3T3 cells, the leupeptin inhibitable enzyme appears to be a plasma membrane enzyme.     

Barbigerone Inhibits Tumor Angiogenesis,Growth and Metastasis in Melanoma

Tumor angiogenesis, growth and metastasis are three closely related processes. We therefore investigated theeffects of barbigerone on all three in the B16F10 tumor model established in both zebrafish and mouse models,and explored underlying molecular mechanisms. In vitro, barbigerone inhibited B16F10 cell proliferation,survival, migration and invasion and suppressed human umbilical vascular endothelial cell migration, invasionand tube formation in concentration-dependent manners. In the transgenic zebrafish model, treatment with10μM barbigerone remarkably inhibited angiogenesis and tumor-associated angiogenesis by reducing blood vesseldevelopment more than 90%. In vivo, barbigerone significantly suppressed angiogenesis as measured by H andE staining of matrigel plugs and CD31 staining of B16F10 melanoma tumors in C57BL/6 mice. Furthermore,it exhibited highly potent activity at inhibiting tumor growth and metastasis to the lung of B16F10 melanomacells injected into C57BL/6 mice. Western blotting revealed that barbigerone inhibited phosphorylation of AKT,FAK and MAPK family members, including ERK, JNK, and p38 MAPKs, in B16F10 cells mainly through theMEK3/6/p38 MAPK signaling pathway. These findings suggested for the first time that barbigerone could inhibittumor-angiogenesis, tumor growth and lung metastasis via downregulation of the MEK3/6/p38 MAPK signalingpathway. The findings support further investigation of barbigerone as a potential anti-cancer drug.     

Antitumor effects of Marginisporum crassissimum (Rhodophyceae), a marine red alga

Marginisporum crassissimum (Yendo) Ganesan, a marine red alga found in the ordinal coastal sea around Japan, revealed antitumor (antimetastatic) effects in vitro and in vivo. In in vitro experiments, extracts of this alga inhibited not only the growth of several tumor cell lines, such as B16-BL6 (a mouse melanoma cell line), JYG-B (a mouse mammary carcinoma cell line) and KPL-1 (a human mammary carcinoma cell line), but also invasion of B16-BL6 cells in a culture system. In in vivo experiments, the lung metastasis of B16-BL6 cells inoculated to the tail vein of B57BL/6J mice was inhibited by intraperitoneal administration of an extract from the alga. In addition, life prolongation of B57BL/6J mice inoculated with B16-BL6 cells was also observed by the intraperitoneal administration of the extract. An effective substance showing B16-BL6 growth inhibition in vitro was partially purified by filtration and hydrophobic column chromatography, and was revealed to be sensitive to trypsin-digestion and heat-treatment. The molecular weight of the substance was greater than 100 kDa. This is the first study demonstrating antitumor (antimetastatic) effects of M. crassissimum.     

Incidence of Mutation and Deletion in Topoisomerase IIα mRNA of Etoposide and mAMSA–resistant Cell Lines

The efficacy of all chemotherapeutic agents is limited by the occurrence of drug resistance. To further understand resistance to topoisomerase II inhibitors, 50 sublines were isolated as single clones from parental cells by exposure to VP–16 (etoposide) or mAMSA ( m –amsacrine). Subsequently, a population of cells from each subline was exposed to three–fold higher drug concentrations allowing 16 stable sublines to be established at higher extracellular drug concentration. Finally, 66 sublines were picked up. The frequency and nature of mutations in the topoisomerase II gene in the drug–selected cell lines were evaluated. In order to screen a large number of cell lines, an RNAse protection assay was developed and mismatches were observed in 13.6% of resistant cell lines (12% of resistant cell lines exposed to lower drug concentrations and 18.8% of resistant cell lines exposed to higher drug concentrations). Some of these mutations are located in vital regions of topoisomerase II (phosphorylation sites in the C–terminal or N–terminal, and nuclear localizing signal of topoisomerase II). Our findings suggest that mutations of topoisomerase II gene are an important and frequent mechanism of resistance to topoisomerase II inhibitors.     

鼻咽癌细胞亚株不同成瘤与转移潜能的分子机制

背景与目的：我们已从鼻咽癌细胞株SUNE－1的克隆株中筛选出3个具有不同生物学特性的细胞亚株：5－8F（高成瘤,高转移）,6－10B（成瘤,不转移）和13－9B（不成瘤）;在本研究中,我们从病毒和遗传两方面探讨鼻咽癌细胞株SUNE－1及其3个亚株的生物学特性差异的分子机制。方法：（1）PCR检测亚株中EB病毒（Epstein-Barr virus,EBV)的Bam HI W片段;（2）应用原位杂交技术检测SUNE－1及其3个亚株中EBV潜伏膜蛋白1（latent membrane protein l,LMP1)的表达情况。（3）应用比较基因组杂交（comparative genomic hybridization,CGH)检测SUNE－1及其3个亚株的基因扩增情况。结果：（1）在SUNE－1及其3个亚株中存在EBV BamHI W片段;（2）在3个亚株中,都能够检测到EBV－LMP1的表达,且表达强度一致。（3）CGH检测发现;SUNE－1的DNA拷贝数变呈现以1,2p,,3,4,5p,6,7,9,10q,11,12q,13q,17q和18q增加和22q拷贝数减少为主;5－8F染色体变化以3p,7q,8q,9q和10q拷贝数增加为主;而6－10B降13－9B除少数几人染色体区域发生缺失外,均无DNA拷贝数的增加。结论：鼻咽癌细胞株SUNE－1及其3个亚株,均有EBV的表达和存在不同的染色体变化,提示其生物学特性的差异可能主要由于染色体的变化引起,但EBV的感染对维持鼻咽癌的恶性程度可能起着重要的作用。     

Inhibition of Tumor Cell Invasion by Ubenimex (Bestatin) in vitro

We have investigated the effect of the immunomodulator ubenimex (bestatin) on tumor cell invasion of reconstituted basement membrane (Matrigel). The invasion of B16-BL6 melanoma cells and Lewis lung carcinoma (3LL) cells into Matrigel-coated filters was inhibited by the presence of bestatin in a concentration-dependent manner. The prctrcatment of either tumor cells or Matrigel with bestatin, however, had little effect on the invasion of tumor cells. Since bestatin was found to inhibit aminopeptidase in addition to its immunomodulating activities, the inhibition of tumor invasion by bestatin is likely to be associated with the action as an enzyme inhibitor. Other aminopeptidase inhibitors, arphamcnine B and amastatin A, could also inhibit tumor cell invasion into Matrigel. Bestatin inhibited hydrolyzing activities towards substrates of aminopeptidases in B16-BL6 melanoma cells. However, bestatin did not have any effect on the haptotactic migration and adhesion of tumor cells to the substrates. These results indicated that bestatin may inhibit tumor cell invasion through a mechanism involving its inhibitory action on aminopeptidases in tumor cells.     

Reduction of lung metastasis,cell invasion,and adhesion in mouse melanoma by statin-induced blockade of the Rho/Rho-associated coiled-coil-containing protein kinase pathway

Background

Melanomas are highly malignant and have high metastatic potential; hence, there is a need for new therapeutic strategies to prevent cell metastasis. In the present study, we investigated whether statins inhibit tumor cell migration, invasion, adhesion, and metastasis in the B16BL6 mouse melanoma cell line.

Methods

The cytotoxicity of statins toward the B16BL6 cells were evaluated using a cell viability assay. As an experimental model, B16BL6 cells were intravenously injected into C57BL/6 mice. Cell migration and invasion were assessed using Boyden chamber assays. Cell adhesion analysis was performed using type I collagen-, type IV collagen-, fibronectin-, and laminin-coated plates. The mRNA levels, enzyme activities and protein levels of matrix metalloproteinases (MMPs) were determined using RT-PCR, activity assay kits, and Western blot analysis, respectively; the mRNA and protein levels of vary late antigens (VLAs) were also determined. The effects of statins on signal transduction molecules were determined by western blot analyses.

Results

We found that statins significantly inhibited lung metastasis, cell migration, invasion, and adhesion at concentrations that did not have cytotoxic effects on B16BL6 cells. Statins also inhibited the mRNA expressions and enzymatic activities of matrix metalloproteinases (MMPs). Moreover, they suppressed the mRNA and protein expressions of integrin α₂, integrin α₄, and integrin α₅ and decreased the membrane localization of Rho, and phosphorylated LIM kinase (LIMK) and myosin light chain (MLC).

Conclusions

The results indicated that statins suppressed the Rho/Rho-associated coiled-coil-containing protein kinase (ROCK) pathways, thereby inhibiting B16BL6 cell migration, invasion, adhesion, and metastasis. Furthermore, they markedly inhibited clinically evident metastasis. Thus, these findings suggest that statins have potential clinical applications for the treatment of tumor cell metastasis.     

Differences between the F10, BL6 and F1 sublines of the B16 melanoma in the enhancement of plasminogen activator and plasminogen activator inhibitor secretion by phorbol myristate acetate

Analysis of conditioned medium from three sublines of the B16 melanoma [F1 (parental), BL6 (invasive), F10 (metastatic)] by SDS-PAGE and zymography revealed the presence of plasminogen activator activity at 60,000 daltons. The relative activity was F10 greater than F1 greater than or equal to BL6. Treatment of the cells with the tumor promoter, phorbol myristate acetate (PMA) led to increased secretion of PA by F10 cells and a lesser increase in secretion by F1 cells and BL6 cells. In addition, a second plasminogen activator activity at 45,000 daltons was detected in conditioned medium from PMA treated F10 cells. Conditioned medium from F10 and F1 cells was also shown to contain a 33,000 dalton plasminogen activator binding protein. Upon PMA treatment the concentration of the binding protein increased in medium from F10 cells but not in similarly treated F1 cells. The binding protein, very likely a plasminogen activator inhibitor, was nearly undetectable in conditioned medium from control and PMA-treated BL6 cells. Therefore, the three sublines, which differ in in vivo phenotypic characteristics, also differ in their in vitro regulation of proteinase and proteinase inhibitor synthesis.     

Establishment of a quantitative mouse dorsal air sac model and its application to evaluate a new angiogenesis inhibitor

We have developed an improved mouse dorsal air sac model for quantifying in vivo tumor-induced angiogenesis. In our improved model, tumor angiogenesis is determined by measuring the blood volume in an area of skin held in contact with a tumor cell-containing chamber, using 51Cr-labeled red blood cells (RBC). The blood volume induced by murine B16-BL6 melanoma cells increased linearly with the cell number in the range from 2 x 10(5) to 5 x 10(6). Ten of 11 human tumor cell lines examined induced a significant increment in blood volume. For three representative human tumor cell lines (A549, WiDr. and HT1080 cells) that showed different angiogenic potencies, the levels of vascular endothelial growth factor (VEGF) produced by the tumor cells cultured under conditions of hypoxia and high cell density were correlated with the degree of in vivo angiogenesis. Using the improved model, it was confirmed that TNP-470, a well-known inhibitor, and borrelidin, an antibiotic from Streptomyces rochei, significantly inhibited the WiDr cell-induced angiogenesis. Borrelidin also inhibited spontaneous lung metastasis of B16-BL6 melanoma at the same dose that inhibited angiogenesis. Our results suggest that the improved mouse dorsal air sac model can be used for simple and quantitative measurement of tumor-induced angiogenesis and its inhibition.     

Thrombin inhibitor, argatroban, prevents tumor cell migration and bone metastasis

It is well known that malignant cells show procoagulant activity, which is associated with their metastatic potential. Thrombin, the key enzyme of the blood coagulation system, is generated around tumor cells, promoting the migration and metastasis of tumor cells. In this study, we evaluated the effect of argatroban, a specific thrombin inhibitor, on the migration and metastasis of B16BL6 melanoma cells. In vitro argatroban dose-dependently inhibited cell migration, the maximum inhibition being observed in the presence of 10 microM argatroban (p < 0.0001). In order to investigate the antimetastatic effect of the thrombin inhibitor, we used an animal model that we have reported previously. C57BL6 mice which had received a bone (femur or tibia) transplanted into the dorsal subcutis were injected with B16 melanoma cells into the left heart ventricle. Intraperitoneal injection of argatroban (9 mg/kg/day for 4 weeks) significantly reduced the number of limbs with metastatic lesions as compared to a placebo (p < 0.05). These results suggest that argatroban was associated with reduced melanoma metastases by inhibiting cell migration. Our results showed that argatroban is effective for treatment of bone metastasis.     

Therapeutic efficacy of interleukin-2 activated killer cells against adriamycin resistant mouse B16-BL6 melanoma.

Development of multidrug-resistance (MDR) remains a major cause of failure in the treatment of cancer with chemotherapeutic agents. In our efforts to explore alternative treatment regimens for multidrug-resistant tumors we have examined the sensitivity of MDR tumor cell lines to lymphokine activated killer (LAK) cells. Adriamycin (ADM) resistant B16-BL6 melanoma, L1210 and P388 leukemic cell lines were tested for sensitivity to lysis by LAK cells in vitro. While ADM-resistant B16-BL6 and L1210 sublines were found to exhibit at least 2-fold greater susceptibility to lysis by LAK cells, sensitivity of ADM-resistant P388 cell was similar to that of parental cells. Since ADM-resistant B16-BL6 cells were efficiently lysed by LAK cells in vitro, the efficacy of therapy with LAK cells against the ADM-resistant B16-BL6 subline in vivo was evaluated. Compared to mice bearing parental B16-BL6 tumor cells, the adoptive transfer of LAK cells and rIL2 significantly reduced formation of experimental metastases (P less than 0.009) and extended median survival time (P less than 0.001) of mice bearing ADM-resistant B16-BL6 tumor cells. Results suggest that immunotherapy with LAK cells and rIL2 may be a useful modality in the treatment of cancers with the MDR phenotype.     

Characterization of selected strongly and weakly invasive sublines of a primary human melanoma cell line and isolation of subtractive cDNA clones

Invasion of basement membranes is a key step in systemic spread of tumour cells. To analyze genetic mechanisms involved in this process, we have selected strongly and weakly invasive sublines with stable phenotypes from a primary human melanoma cell line by repeated passage through a reconstituted basement membrane in vitro. The sublines differed approximately 5-fold in their invasive potential. Invasiveness correlated with better attachment and overexpression of the integrin α_v/β₃ (vitronectin/laminin-receptor). Treatment with retinoic acid inhibited proliferation in both sublines and invasion in the weakly invasive cells but stimulated invasion in the strongly invasive subline. Northern-blot analyses revealed equal levels of mRNA expression regarding collagenase type-IV and retinoic-acid receptors but enhanced expression of TIMP-2 mRNA in weakly invasive cells. The 2 sublines differed significantly in their respective DNA ploidy when compared to the wild-type Mel Im cell line, suggesting that they represent heterogeneous clones present in the primary tumour. We have started to exploit this in vitro system for tumour heterogeneity to clone genes involved in invasion. By a subtractive cDNA cloning strategy, 12 partial cDNA clones were obtained that are specifically overexpressed in the strongly or weakly invasive subline. These results illustrate that stable genetic alterations lead to heterogeneous subpopulations within primary melanomas which differ in their ability to invade basement membranes and interact with components of the extracellular matrix.