Stimulation of angiogenesis as an explanation of Matrigel-enhanced tumorigenicity

Expression of CXCL1 in human endothelial cells induces angiogenesis through the CXCR2 receptor and the ERK1/2 and EGF pathways

Endothelial cell growth and proliferation are critical for angiogenesis; thus, greater insight into the regulation of pathological angiogenesis is greatly needed. Previous studies have reported on chemokine (C-X-C motif) ligand 1 (CXCL1) expression in epithelial cells and that secretion of CXCL1 from these epithelial cells induces angiogenesis. However, limited reports have demonstrated CXCL1 expression in endothelial cells. In this report, we present data that expand on the role of CXCL1 in human endothelial cells inducing angiogenesis. Specifically, CXCL1 is expressed and secreted from human endothelial cells. Interference of CXCL1 function using neutralizing antibodies resulted in a reduction in endothelial cell migration and viability/proliferation, the latter associated with a decrease in levels of cyclin D and cdk4. In vitro studies revealed that CXCL1 influenced neoangiogenesis through the regulation of epidermal growth factor and ERK1/2. In a xenograft angiogenesis model, interference of CXCL1 function resulted in inhibition of angiogenesis. A better understanding of the role of CXCL1 in the interactions between the endothelial and epithelial components will provide insight into how human tissues use CXCL1 to survive and thrive in a hostile environment.

Expression of Tax-interacting protein 1 (TIP-1) facilitates angiogenesis and tumor formation of human glioblastoma cells in nude mice

Glioblastoma is the most common and fatal type of primary brain tumors featured with hyperplastic blood vessels. Here, we performed meta-analyses of published data and established a correlation between high TIP-1 expression levels and the poor prognosis of glioblastoma patients. Next, we explored the biological relevance of TIP-1 expression in the pathogenesis of glioblastoma. By using orthotopic and heterotopic mouse models of human glioblastomas, this study has characterized TIP-1 as one contributing factor to the tumor-driven angiogenesis. In vitro and in vivo functional assays, along with biochemical analyses with microarrays and antibody arrays, have demonstrated that TIP-1 utilizes multiple pathways including modulating fibronectin gene expression and uPA protein secretion, to establish or maintain a pro-angiogenic microenvironment within human glioblastoma. In conclusion, this work supports one hypothesis that TIP-1 represents a novel prognostic biomarker and a therapeutic target of human glioblastoma.

Cooperative signaling for angiogenesis and neovascularization by VEGF and HGF following islet transplantation

BACKGROUND

Delayed angiogenesis remains a significant challenge to the survival of transplanted islets. In this study, using a murine model of subcutaneous islet transplantation with matrigel basement membrane matrix, we determined the role of the proangiogenic growth factors in enhancing the islet engraftment.

METHODS

BALB/c islets were transplanted subcutaneously in growth factor reduced (GFR) or growth factor supplemented (GFS) matrigel into diabetic severe combined immunodeficient mice. GFS matrigel was prepared by supplementing GFR with proangiogenic factors, vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). The functioning grafts were harvested at 15 days and vessel formation was analyzed histopathologically.

RESULTS

Our results demonstrate that suboptimal (250) islet equivalents in GFS-VEGF+HGF were able to restore normoglycemia, whereas those transplanted in GFR failed to reverse diabetes. Histopathology of the GFS-VEGF+HGF graft revealed 12±3 blood vessels per field, whereas GFR, GFS-VEGF, and GFS-HGF grafts had only 3±1, 6±2, and 4±1 blood vessels, respectively. Insulin staining demonstrated increased number of islets in matrigel supplemented with VEGF and HGF. Protein and mRNA analysis demonstrated enhanced intercellular adhesion molecule and vascular cell adhesion molecule within the islets when supplemented with both VEGF+HGF suggesting stable blood vessel formation. Transcription factors focal adhesion kinase phosphorylation and extracellular signal-regulated kinase1/2 phosphorylation were also increased (8-fold and 4.6-fold, respectively) when both the growth factors were present. There was weak expression of transcription factors when VEGF or HGF were supplemented alone.

CONCLUSION

We conclude that proangiogenic growth factors, VEGF and HGF, synergistically enhance angiogenesis after islet transplantation leading to stable engraftment.

Small intestinal submucosa gel as a potential scaffolding material for cardiac tissue engineering

Cardiac tissue engineering typically utilizes protein-rich scaffolding materials and growth factors to improve cardiac tissue function in vitro and in vivo. The objectives of this preliminary study were (i) to investigate the potential of porcine small intestinal submucosa gel (SIS gel) in cardiac tissue engineering and (ii) to compare the function of tissues based on either SIS gel or Matrigel, a tumor-derived benchmark material. Neonatal rat cardiac cells were combined with either SIS gel or Matrigel and cultured on porous elastomeric scaffolds composed of poly(glycerol sebacate) for 13days. Tissue function was assessed by measuring contraction rates twice daily. Tissue morphology was compared qualitatively by hematoxylin and eosin staining. Normalized troponin T expression (troponin T:DNA) was compared using image analysis. SIS gel constructs contracted at significantly higher rates than Matrigel constructs on days 8-11. Normalized troponin T expression was significantly higher in SIS gel constructs compared with Matrigel constructs. In summary, this research demonstrated that: (i) SIS gel can be used to create contractile engineered cardiac tissue; (ii) SIS gel produced engineered cardiac tissues with a more physiological contraction rate and higher phenotypic protein expression based on the basic in vitro examinations performed in this study.

Paradoxical antiproliferative effect by a murine mammary tumor-derived epithelial cell line

BACKGROUND

Despite significant advancement in breast cancer therapy, there is a great need for a better understanding of the mechanisms involved in breast carcinogenesis and progression, as well as of the role of epigenetic contributions from stromal cells in mammary tumorigenesis. In this study, we isolated and characterized murine mammary tumor-derived epithelial and myofibroblast cell lines, and investigated the in vitro and in vivo effect of cellular soluble factors produced by the epithelial cell line on tumor cells.

METHODS

Morphology, immunophenotype, cytogenetics, invasiveness, and tumorigenicity of epithelial (LM-234ep) and myofibroblast (LM-234mf) cell lines isolated from two murine mammary adenocarcinomas with common ancestor were studied. The in vitro effects of LM-234ep conditioned medium on proliferation, cell cycle distribution, and expression of cell cycle proteins, were investigated in LM-234mf cells, mouse melanoma cells (B16-F10), and human cervical adenocarcinoma cells (HeLa). The in vivo anti-tumor activity of LM-234ep conditioned media was evaluated in subcutaneous tumors formed in nude mice by B16-F10 and HeLa cells.

RESULTS

LM-234ep cells were found to be cytokeratin positive and hipertriploid, whereas LM-234mf cells were alpha-smooth muscle actin positive and hypohexaploid. Chromosome aberrations were found in both cases. Only LM-234mf revealed to be invasive in vitro and to secrete active MMP-2, though neither of the cell types were able to produce progressing tumors. LM-234ep-derived factors were able to inhibit the in vitro growth of LM-234mf, B16-F10, and HeLa cells, inducing cell cycle arrest in G0/G1 phase. The administration of LM-234ep conditioned medium inhibited the growth of B16-F10 and HeLa tumors in nude mice.

CONCLUSION

Our data suggest the existence of epithelial cell variants with tumor suppressive properties within mammary tumors. To our knowledge, this is the first report showing antiproliferative and antineoplastic activities induced by tumor-derived epithelial cells.

Matrix metalloproteinase inhibitor MMI-166 inhibits lymphogenous metastasis in an orthotopically implanted model of lung cancer

Matrix metalloproteinases (MMP) are considered to be critically involved in tumor invasion and the metastasis of various cancers. MMI-166 is a selective inhibitor of matrix metalloproteinase (MMP-2, MMP-9, and MMP-14). The purpose of this study was to evaluate the effects of MMI-166 on both the growth of the implanted tumor and the lymph node metastasis of the mediastinum and prolonging the life span, using an orthotopic implantation model of the Ma44-3 cancer cell line. We examined the anti-invasive effect of MMI-166 in lung cancer cell lines using an in vitro invasion assay. Next, we examined the anticancer effect of MMI-166 in vivo. MMI-166 (200 mg/kg body weight) or a vehicle was administered orally to the orthotopically implanted lung cancer model. MMI-166 dose-dependently inhibited the invasion of cancer cell lines with expressions of MMP-2 and/or MMP-9 in vitro. In vivo, MMI-166 significantly inhibited mediastinal lymph node metastasis in this orthotopic model (weight of the mediastinum: control, 0.089 +/- 0.009 versus MMI-166, 0.069 +/- 0.008 mg; P = 0.005; metastatic area: control, 93,495 +/- 55,747 versus MMI-166, 22,747 +/- 17,478 pixels; P = 0.045). MMI-166 prolonged the life span by 6 days in median survival time in the orthotopically implanted model (P = 0.039). These results showed that MMI-166 could possibly inhibit lymph node metastasis and prolong the life span in lung cancer patients.

Vascular endothelial growth factor and enhanced angiogenesis do not promote metastatic conversion of a newly established azoxymethane-induced colon cancer cell line

The organo-specific carcinogen, azoxymethane (AOM), produces colon tumors in mice that share many pathological features with sporadic human colorectal cancer (CRC). An important distinction between AOM-induced CRC and human CRC is lack of mucosal invasion in the murine model. To assess the role of the microenvironment in preventing the invasive phenotype, multiple benign in situ adenocarcinomas were harvested from AOM-treated mice and cultured in vitro. However, tumor cell growth was extremely limiting under standard culturing conditions. Thus, we injected tumor cells directly into nude mice and performed two serial transplants, and successfully explanted a rapidly growing epithelial tumor cell line (AJ02nm(0)). When injected subcutaneously (sc) into nude mice, AJ02nm(0) cells formed well-differentiated adenocarcinomas with minimal tumor invasive capacity. To define whether metastatic and invasive potential were related to lack of angiogenic stimuli, the AJ02nm(0) cells were transfected to overexpress murine vascular endothelial growth factor-164 (VEGF(164)). AJ02nm-VEGF cells produced rapidly growing tumors in nude mice that exhibited extensive pseudo-epithelial ductal architecture and supporting vasculature, but without increased invasive potential compared to controls. The established murine colon epithelial cell line provides a useful experimental model to further elaborate genetic and epigenetic factors that may promote or inhibit colon tumorigenesis and metastasis.

Novel In Vivo Murine Model to Study Islet Potency: Engraftment and Function

Standard islet potency testing uses transplantation of islets under the kidney capsule in diabetic severe combined immunodeficient (d-SCID) mice. Even though it is possible to achieve normoglycemia in the majority of recipients by this method, the surgical procedure, by itself, is technically difficult and associated with an appreciable mortality of animals. In addition, the spatially limited renal subcapsular site restricts the mass of islet tissue that can be transplanted. Matrigel basement membrane matrix (MATRIGEL), extracted from a mouse sarcoma, is rich in angiogenic growth factors and has been shown to support the growth of mammalian cells using murine models. In this report we demonstrate that subcutaneous islet transplantation with MATRIGEL can effectively achieve normoglycemia and that this is a simple and reproducible model for in vivo islet potency testing in d-SCID mice that overcomes many drawbacks of the conventional method of kidney subcapsular islet transplantation.

Highly sensitive biosafety model for stem-cell-derived grafts

BACKGROUND

The recent success in the derivation of differentiated cell types from stem cells has raised prospects for the application of regenerative cell therapy. In particular, embryonic stem cells are attractive sources for cell transplantation, due to their immortality and rapid growth. These cells, however, also possess tumorigenic properties, which raises serious safety concerns and makes biosafety testing mandatory. Our goal was to establish a highly sensitive animal model for testing the proliferative potential of stem-cell grafts.

METHODS

BALB/c nude mice received cell grafts of non-neoplastic MRC-5 cells containing defined numbers of mouse embryonic stem cells. We either injected 1 million viable cells into the kidney capsule, or mixed 2 million cells with Matrigel for s.c. transplantation. To analyze the possible impact of an intact immune response on tumor development, we also transplanted the cells into immunocompetent mice. Animals were sacrificed when the tumors became >1 cm and were analyzed in detail.

RESULTS

The nude mouse model reproducibly allowed detection of 20 tumorigenic cells, and even as few as 2 ES cells were found to form teratoma. Interestingly, the administration of cell grafts at two different application sites resulted in different growth kinetics and tumor phenotypes. The highest level of sensitivity (100% detection of 20 tumorigenic ES cells) was achieved by s.c. injection of cells mixed with Matrigel. The influence of the immune system on tumor-cell development was demonstrated by a higher tumor rate of transplants in immunodeficient nude mice compared with immunocompetent mice.

DISCUSSION

We have established a reliable animal model for routine assessment of the biosafety profile of stem-cell-derived cell transplants. This model will facilitate the generation of homogenous non-tumorigenic cell populations, and will help to integrate standardized safety systems into the application of stem-cell-derived grafts for clinical purposes.

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Characterization of 11 human sarcoma cell strains: evaluation of cytogenetics, tumorigenicity, metastasis, and production of angiogenic factors

BACKGROUND

Human sarcomas have a propensity for aggressive local invasion and early pulmonary metastasis. Frequently, deaths are due to uncontrolled pulmonary metastases. The purpose of the current study was to evaluate cytogenetics, tumorigenicity, metastatic potential, and production of angiogenic factors in human sarcoma cell strains. A secondary purpose was to establish low passage cell strains for studying new therapeutic approaches.

METHODS

The authors established 11 cell strains from human sarcoma surgical specimens and characterized their in vitro tumor properties, including growth in soft agar, expression of angiogenic growth factors (vascular endothelial growth factor [VEGF] and basic-fibroblast growth factor [bFGF]), and cytogenetics.

RESULTS

All of the cell strains remained diploid. All exhibited the ability to grow in soft agar and expressed both VEGF as well as bFGF. In addition, 6 of the 11 established sarcoma cell strains were tumorigenic, 5 of which spontaneously metastasized to the lungs in nude mice. Four of the five cell strains that yielded lung metastases were derived from lung metastases in patients.

CONCLUSIONS

The 11 cell strains, which were derived from diverse sarcoma histologies, will provide a model for studying not only metastatic progression but also the in vitro and in vivo efficacy of new therapeutic modalities for human sarcomas.

Quantitative detection of lac-Z-transfected CC531 colon carcinoma cells in an orthotopic rat liver metastasis model

Disseminated colon carcinoma metastases in the liver are associated with low cure rates and constitute a serious therapeutic problem. Appropriate experimental models which mimic metastases development and outgrowth can provide insight into the mechanism of this lethal process and facilitate the finding of new approaches for its control. We established an orthotopic liver metastases model based on CC531 rat colon adenocarcinoma cells which were transfected with a beta-galactosidase gene as marker to facilitate their detection. Intraportal injection of CC531-lac-Z cells resulted in a rapid and locally aggressive growth within the liver and was characterised by a tumour volume doubling time of 20 h and abundant angiogenesis. A commercially available chemi-luminescence assay allowed rapid, quantitative and sensitive detection of the diffusely growing tumour cells. Immunogenicity of CC531-lac-Z cells induced by the marker gene was significantly reduced by co-administering the tumour cells with matrigel. Within an observation period of three weeks following tumour cell injection only 6% of the animals showed lung involvement, thus indicating a specific homing of CC531-lac-Z cells to the liver. This period appears long enough to allow therapeutic manipulations at various stages of tumour growth in the liver. It is envisaged that the model will have applications for various therapeutic strategies.

Development of diffuse invasive (grade 4D) human oral squamous cell carcinoma model in severe combined immunodeficiency mice: microangioarchitectural analysis and immunohistochemical study

Among oral squamous cell carcinomas (OSCCs), the diffuse invasive (grade 4D) tumour exhibits the highest degree of malignancy. The TSU cell line, which has been established from a grade 4D OSCC, has not been successfully grown even in immuno-suppressed hosts. Here, invasive cells were selected by the repeated inoculation of TSU cells with Matrigel and gelatin sponge into the subcutaneous tissue of nude mice. The selected cells formed oral tumours temporarily in nude mice and produced lethal tumourgenicity in severe combined immunodeficiency (SCID) mice without the addition of other materials. The microangioarchitecture of the tumours in SCID mice showed neovascularization and the formation of a vascular network. An immunohistochemical study demonstrated that the expressions of vascular endothelial growth factor and matrix metalloproteinase-2 were strong, whereas desmoglein-1 and type-IV collagen were absent. These findings suggested that the loss of intercellular junctions and dissolution of basement membranes may underlie the pathogenesis of diffuse invasive growth in grade 4D tumours.

Mediastinal lymph node metastasis model by orthotopic intrapulmonary implantation of Lewis lung carcinoma cells in mice

This study is designed to establish a pulmonary tumour model to investigate the biology and therapy of lung cancer in mice. Current methods for forming a solitary intrapulmonary nodule and subsequent metastasis to mediastinal lymph nodes are not well defined. Lewis lung carcinoma (LLC) cell suspensions were orthotopically introduced into the lung parenchyma of C57/BL6 mice via a limited skin incision without thoracotomy followed by direct puncture through the intercostal space. The implantation process was performed within approximately 50 s per mouse, and the operative mortality was less than 5%. Single pulmonary nodules developed at the implanted site in 93% of animals and subsequent mediastinal lymph node metastasis was observed in all mice that formed a lung nodule after intrapulmonary implantation. The size of tumour nodule and the weight of mediastinal lymph node increased in a time-dependent manner. The mean survival time of mice implanted successfully with LLC cells was 21+/-2 days (range 19-24 days). Histopathological analysis revealed that no metastatic tumour was detectable in the mediastinal lymph nodes on day 11, but metastatic foci at mediastinal lymph nodes were clearly observed on days 17 and 21 after implantation. Other metastases in distant organs or lymph nodes were not observed at 21 days after the implantation. Comparative studies with intrapleural and intravenous injections of LLC cells suggest that the mediastinal lymph node metastasis by intrapulmonary implantation is due to the release of tumour cells from the primary nodule, and not due to extrapulmonary leakage of cells. An intravenous administration of cis-diamine dichloro platinum on day 1 after tumour implantation tended to suppress the primary tumour nodule and significantly inhibited lymph node metastasis. Thus, a solitary pulmonary tumour nodule model with lymph node metastasis approximates clinical lung cancer and may provide a useful basis for lung cancer research.

Studies on the mechanisms responsible for inhibition of experimental metastasis of B16-F10 murine melanoma by pentoxifylline

Pentoxifylline (PTX), a methylxanthine derivative widely used as a hemorheological agent in the treatment of peripheral vascular disease, was studied to unveil the mechanisms responsible for its inhibitory action on B16-F10 experimental metastasis. In vitro pretreatment of B16-F10 cells with noncytotoxic concentrations of PTX significantly inhibited their adhesion to reconstituted basement membrane Matrigel(R) and type IV collagen as well as the relative activity of secreted 92 kD metalloproteinase. However, PTX pretreatment of B16-F10 cells did not affect their in vitro invasiveness. Heterotypic organ adhesion assays carried out with B16-F10 cells and suspended organ tissues demonstrated that pretreatment with noncytotoxic concentrations of PTX of both, tumor cells or lung tissue, brought about a dose-dependent inhibition of melanoma cell adhesion to lung. Immunohistochemical studies using antibodies against CD31 adhesion molecule (PECAM-1) revealed that B16-F10 cells adhere to lung endothelial cells. Our results suggest that PTX may exert its inhibitory effect on tumor lodgment, and as a consequence of that on experimental metastases, through an inhibitory action on cell adhesion molecules.

Failure of wild-type p53 gene therapy in human cancer cells expressing a mutant p53 protein

The introduction of exogenous wild-type p53 into human cancer cells bearing p53 mutation does not necessarily result in inhibition of tumor growth. We have demonstrated this in MDA-MB468 breast cancer cells which are hemizygous for p53 mutation and also in KM12SM colorectal carcinoma cells which are heterozygous for p53 mutation. The wtp53 transfectants decreased three- to four-fold the number of colonies compared with controls. Most wtp53-expressing cells died by apoptosis at early passages, but some cells were able to form colonies and their proliferation rate was similar to control transfectants. This reversion was observed in three of the six MDA-MB-468 clones selected. When MDA-wtp53 transfectants were implanted orthotopically in nude mice only one clone showed prolonged tumor latency. No differences were found in either tumor proliferation or apoptosis in tumors. Integration and expression of exogenous wtp53 was assessed in early and late passages in vitro, and in tumors growing in vivo. Consistently, we found mutations in the exogenous wtp53 gene of MDA-MB468 transfectants. Excision of the exogenous gene was an alternative to abrogate the wtp53 function that was extremely efficient in KM12 cells, although they maintained resistance to geneticin. These results were corroborated by the functional assay in yeast. In conclusion, wtp53 is inactivated in these cancer cells by different mechanisms. The presence of mutated p53 may confer genome instability and mutator ability, which allows cells to escape the effects of the exogenous wtp53 and contributes to the failure of wtp53 gene therapy.

A gp130 Interleukin-6 Transducer-Dependent SCID Model of Human Multiple Myeloma

Agonist antihuman gp130 transducer monoclonal antibodies (MoAbs) were used in SCID mice to grow myeloma cells whose survival and proliferation is dependent on gp130 transducer activation. The agonist anti-gp130 MoAbs neither bound to murine gp130 nor activated murine cells and, as a consequence, did not induce interleukin-6 (IL-6)–related toxicities in mice. They have a 2-week half-life in vivo when injected in the peritoneum. The agonist antibodies made possible the in vivo growth of exogenous IL-6–dependent human myeloma cells as well as that of freshly explanted myeloma cells from 1 patient with secondary plasma cell leukemia. Tumors occurred 4 to 10 weeks after myeloma cell graft and weighed 3 to 5 g. They grew as solid tumors in the peritoneal cavity and metastasized to the different peritoneal organs: liver, pancreas, spleen, and intestine. Tumoral cells were detected in blood and bone marrow of mice grafted with the XG-2 myeloma cells. Tumoral cells grown in SCID mice had kept the phenotypic characteristics of the original tumoral cells and their in vitro growth required the presence of IL-6 or agonist anti-gp130 MoAbs. Myeloma cells from 4 patients with medullary involvement persisted for more than 1 year as judged by detectable circulating human Ig. However, no tumors were detected, suggesting a long-term survival of human myeloma cells without major proliferation. These observations paralleled those made in in vitro cultures as well as the tumor growth pattern in these patients. This gp130 transducer-dependent SCID model of multiple myeloma should be useful to study various therapeutical approaches in multiple myeloma in vivo.

A gp130 Interleukin-6 Transducer-Dependent SCID Model of Human Multiple Myeloma

Agonist antihuman gp130 transducer monoclonal antibodies (MoAbs) were used in SCID mice to grow myeloma cells whose survival and proliferation is dependent on gp130 transducer activation. The agonist anti-gp130 MoAbs neither bound to murine gp130 nor activated murine cells and, as a consequence, did not induce interleukin-6 (IL-6)–related toxicities in mice. They have a 2-week half-life in vivo when injected in the peritoneum. The agonist antibodies made possible the in vivo growth of exogenous IL-6–dependent human myeloma cells as well as that of freshly explanted myeloma cells from 1 patient with secondary plasma cell leukemia. Tumors occurred 4 to 10 weeks after myeloma cell graft and weighed 3 to 5 g. They grew as solid tumors in the peritoneal cavity and metastasized to the different peritoneal organs: liver, pancreas, spleen, and intestine. Tumoral cells were detected in blood and bone marrow of mice grafted with the XG-2 myeloma cells. Tumoral cells grown in SCID mice had kept the phenotypic characteristics of the original tumoral cells and their in vitro growth required the presence of IL-6 or agonist anti-gp130 MoAbs. Myeloma cells from 4 patients with medullary involvement persisted for more than 1 year as judged by detectable circulating human Ig. However, no tumors were detected, suggesting a long-term survival of human myeloma cells without major proliferation. These observations paralleled those made in in vitro cultures as well as the tumor growth pattern in these patients. This gp130 transducer-dependent SCID model of multiple myeloma should be useful to study various therapeutical approaches in multiple myeloma in vivo.

Inhibition of stromal matrix metalloproteases: effects on breast-tumor promotion by fibroblasts

Co-injection of fibroblasts with human epithelial breast-tumor MCF7 cells in the presence of Matrigel enhances tumor growth in nude mice. While most of the matrix metalloproteinases (MMPs) have been shown to be produced by stromal cells, tumor cells such as MCF7 cells are unable to produce MMPs. We therefore, hypothesized that the tumor-promoting effect of fibroblasts could be related to their production of MMPs. In order to inhibit stromal proteases, over-production of TIMP-2 was induced in MCF7 cells by in vitro retroviral-mediated gene transfer. TIMP-2-producing MCF7 cells were then co-injected with fibroblasts into nude mice. Alternatively, we evaluated the effect of Batimastat, a synthetic inhibitor of MMPs, on the tumorigenicity of MCF7 cells co-inoculated with fibroblasts into nude mice. Both physiological (TIMP-2) and synthetic (Batimastat) inhibitors of MMPs were able to abolish the tumor-promoting effect of fibroblasts. On the contrary, they failed to modulate the tumorigenicity of MCF7 cells injected alone. Interestingly, Matrigel from which low-molecular-weight proteins or growth factors had been removed failed to favor the tumorigenicity of MCF7 cells inoculated with fibroblasts. These findings emphasize the importance of fibroblasts in cancer progression, and suggest that their role could be related at least in part to production of proteases which can induce the release of factors from the extracellular matrix.

The role of stroma in breast carcinoma growth in vivo

The malignant progression of tumors is thought to be related to the expression of oncogenes and loss of expression of tumor suppressor gene. These factors are intrinsic to the cancer cells themselves. However, carcinomas are also infiltrated by host cells (fibroblasts, endothelial cells, inflammatory cells) and surrounded by an extracellular matrix which is extensively remodeled. The extracellular matrix components and infiltrating host cells provide a microenvironment that conditions both tumor progression and the metastatic process. Transplantation of human tumors into athymic nude mice has become an important experimental approach to study the biology of human cancers. The different models developed so far are beginning to elucidate the role of matrix molecules, growth factors and enzymes as well as fibroblasts in tumor progression. These animal models are likely to provide a useful tool to evaluate new antitumor treatments.

Human prostate tumor angiogenesis in nude mice: metalloprotease and plasminogen activator activities during tumor growth and neovascularization of subcutaneously injected matrigel impregnated with human prostate tumor cells

BACKGROUND

A critical aspect for growth of solid tumors is the development of a blood supply. Our objective was to establish a model for the study of angiogenesis of human prostate tumors by examining the growth of microvessels into Matrigel containing human prostate tumor cells implanted subcutaneously in nude mice.

METHODS

Human prostate tumor cell lines PC-3 and LNCaP were injected in Matrigel under the abdominal skin of nude mice and were harvested at 4, 8, and 14 days post-injection. The growth of tumor cells and blood vessels was examined histologically and by immunohistochemical localization of von Willibrand Factor VIII (vWF). Since plasminogen activators and matrix metalloproteases are associated with angiogenesis, the activities and molecular forms of these proteases were determined in Matrigel control and Matrigel-tumor cell subcutaneous implants.

RESULTS

Blood vessel formation in the Matrigel implants containing LNCaP and PC-3 cells was demonstrable at 8 days post-injection. However, the pattern of blood vessel formation by the two tumor cell lines was different; PC-3 tumors showed a more invasive phenotype and smaller diameter blood vessels, whereas LNCaP tumors grew as large cellular spheroids surrounded by large, dilated blood vessels. Many blood vessels of PC-3 tumors expressed vWF by day 14 of growth, whereas most blood vessels in LNCaP tumors were immunohistochemically negative for this antigen. Mouse skin blood vessels in the same PC-3 and LNCaP tumor histological sections were positive for vWF. Matrigel contained both plasminogen activator and metalloprotease activities. The plasminogen activator activity in Matrigel control implants was totally inhibited by 4 days post-injection, indicating the presence of an inhibitor provided by the host mouse. LNCaP tumor cells injected did not have appreciable plasminogen activator activity, nor did LNCaP tumors develop plasminogen activator activity with tumor growth post-injection. PC-3 cells did have plasminogen activator activities, which were partially negated after subcutaneous injection (4 days), but then increased again by 8 days post-injection. This increase in plasminogen activator activity was due to urokinase (about 54 kDa) produced by the tumor and not by the mouse host (mouse urine urokinase about 44 kDa). Matrigel alone demonstrated gelatinase B (about 95 kDa) activity in zymograms, and gained considerable gelatinase A (about 70 and 74 kDa) activity after subcutaneous implantation. No metalloprotease activity from the tumor cells could be distinguished over that contributed by the mouse host cells in the Matrigel. Matrigel also contains caseinolytic activities of approximately 56, 80, 85, and 89 kDa. After subcutaneous injection of Matrigel, the 89 kDa form increases considerably in activity and the others are diminished. This pattern is also observed in LNCaP and PC-3 tumors post-injection, except the PC-3 tumors demonstrate increased 56 kDa activity.

CONCLUSION

The subcutaneous growth of LNCaP and PC-3 prostate tumor cells in Matrigel in nude mice can be used to study tumor-induced angiogenesis. However, the organization of LNCaP and PC-3 tumor growth and the pattern of microvessels associated with each tumor are different in this system, implying that each tumor has unique influences on the pattern of microvessel development. The mode of action by which this is brought about is not known, but may be due to specific factors produced/ released by the tumor cells.

Misregulation of stromelysin-1 expression in mouse mammary tumor cells accompanies acquisition of stromelysin-1-dependent invasive properties

Stromelysin-1 is a member of the metalloproteinase family of extracellular matrix-degrading enzymes that regulates tissue remodeling. We previously established a transgenic mouse model in which rat stromelysin-1 targeted to the mammary gland augmented expression of endogenous stromelysin-1, disrupted functional differentiation, and induced mammary tumors. A cell line generated from an adenocarcinoma in one of these animals and a previously described mammary tumor cell line generated in culture readily invaded both a reconstituted basement membrane and type I collagen gels, whereas a nonmalignant, functionally normal epithelial cell line did not. Invasion of Matrigel by tumor cells was largely abolished by metalloproteinase inhibitors, but not by inhibitors of other proteinase families. Inhibition experiments with antisense oligodeoxynucleotides revealed that Matrigel invasion of both cell lines was critically dependent on stromelysin-1 expression. Invasion of collagen, on the other hand, was reduced by only 40-50%. Stromelysin-1 was expressed in both malignant and nonmalignant cells grown on plastic substrata. Its expression was completely inhibited in nonmalignant cells, but up-regulated in tumor cells, in response to Matrigel. Thus misregulation of stromelysin-1 expression appears to be an important aspect of mammary tumor cell progression to an invasive phenotype.

Exposure to vinorelbine inhibits in vitro proliferation and invasiveness of transitional cell bladder carcinoma

PURPOSE

To study the effect of vinorelbine (VNR) on in vitro cell proliferation, invasiveness, cell adhesion to substrate, cell motility and metalloproteinase secretion of MB-49, a murine transitional cell carcinoma of the bladder (TCC).

MATERIALS AND METHODS

The colorimetric MTS assay, which depends upon viable versus nonviable mitochondria, was used to evaluate the effect of graded concentrations of VNR on in vitro MB-49 cell growth. Chemoinvasion and cell motility were studied in TCC cells exposed for 24 hours to a noncytotoxic dose of VNR, through their ability to migrate across Matrigel-coated or Type IV collagen-coated 8-microns. pore filters. Zymographic studies in gelatin-embedded polyacrylamide gels were done to investigate gelatinolytic activity in conditioned media from treated and untreated MB-49 cells.

RESULTS

Vinorelbine inhibited MB-49 cell growth in a dose-dependent manner (IC(50)40 ng./ml.). In vitro cell invasive capacity of MB-49 cells pretreated for 24 hours with VNR at noncytotoxic doses (1 and 10 ng./ml.) was significantly lower than that of untreated cells. The decreased invasion of VNR-treated cells was not accompanied by a diminished adhesion to Matrigel or type IV collagen nor by a significant reduced secretion of gelatinolytic metalloproteinases. Instead, motility of MB-49 cells exposed to noncytotoxic concentrations of VNR was inhibited in a dose-response fashion similar to that of invasion.

CONCLUSION

Vinorelbine proved to be an effective drug to inhibit tumor cell growth and invasion in a transitional cell bladder carcinoma model. The results obtained would justify preclinical studies to evaluate the effectiveness of VNR as a potential treatment of TCC.

Metastatic potential of human melanoma cells in nude mice--characterisation of phenotype, cytokine secretion and tumour-associated antigens

Incidence and mortality of human malignant melanoma has risen rapidly over recent decades. Although the notorious resistance to treatment is characteristic for metastatic malignant melanoma, only a few experimental models have been established to study the metastatic cascade or to test new alternative treatment modalities. Thus, new human models are wanted. Here, we describe the metastatic behaviour of seven human melanoma cell lines derived from two primary cutaneous melanomas (WM 98-1, WM 1341) and five metastases established from liver (UKRV-Mel-4), skin (M7, M13), pleural effusion (UKRV-Mel-2) and lymph node (MV3). All cell lines were analysed for their capacity to grow in nude mice after s.c. and i.v. administration. M13 cells developed liver metastases spontaneously after s.c. injection, and subsequent passages of M13 and M7 melanoma cells caused liver metastases after i.v. injection, whereas MV3 and WM98-1 gave rise to lung metastases, using the same inoculation route. In contrast, WM 1341, UKRV-Mel-2 and UKRV-Mel-4 grew only very slowly in nude mice after s.c. injection and did not cause any metastases after i.v. or s.c. administration. The pattern of metastases or growth kinetics did not correlate with the interleukin 8 or tumour necrosis factor secretion of cell lines. Adhesion molecules and growth factor receptor expression on the cell lines differed widely, as determined by flow cytometry, with the low metastatic cell lines (UKRV-Mel-2, UKRV-Mel-4 and WM 1341) demonstrating a marked reduction in VLA-1 and VLA-5 expression compared with the metastatic lines (M7, M13, MV3 and WM 98-1). Expression of pigment-related proteins such as tyrosinase, TRP-1, TRP-2, Melan-A/MART-1, gp100, MAGE1 or MAGE-3 was not associated with growth and metastatic characteristics of the melanoma cell lines analysed. In conclusion, the established human melanoma cell lines exhibited diverse growth behaviour in nude mice in congruence with some early established prognostic markers such as VLA-1 and VLA-5. The xenografts provide good models for further study of metastatic processes as well as for evaluation of alternative treatment modalities including new pharmaceutical drugs and gene therapeutic targeting using tissue-specific gene regulatory elements for gene targeting.

Suppression of the metastatic phenotype of a mouse skin carcinoma cell line independent of E-cadherin expression and correlated with reduced Ha-ras oncogene products

The HaCa4 cell line, derived from a mouse skin carcinoma induced by Harvey murine sarcoma virus, is highly tumorigenic when injected into nude mice and produces multiple metastases in the lungs. HaCa4 cells express high levels of viral Ha-ras oncogene products, anomalously synthesize the embryonic/simple epithelial keratin K8, and have lost the expression of the cell-cell adhesion receptor E-cadherin (E-CD). E-CD(+) cell clones (E62 and E24), obtained by transfection of an exogenous E-CD cDNA into HaCa4 cells, had a decreased ability to migrate through type IV collagen matrices. However, the E-CD (+) E62 clone remained as metastatic as the parental cell line, whereas the E24 clone, which does not take up the exogenous cDNA but spontaneously switches on the endogenous E-CD gene, suppressed the metastatic phenotype although it maintained its tumorigenicity. E24 cells had fivefold to sixfold lower levels of viral Ha-ras mRNA and p21 protein than the other cell lines. In addition, they did not synthesize K8 but rather switched on keratin K19. The comparison of E-CD proteins synthesized by E62 and E24 cell lines revealed no structural or functional differences because both localized at cell-cell contacts and associated with alpha-catenin, beta-catenin, and plakoglobin. Furthermore, E-CD was still expressed in metastatic lung nodules produced by E62 cells. These results suggest that suppression of the metastatic phenotype in E24 cells occurs independently of E-CD expression and correlates with decreased levels of the oncogenic ras p21 protein.

Oncogenes as inducers of tumor angiogenesis

Dominantly acting transforming oncogenes are generally considered to contribute to tumor development and progression by their direct effects on tumor cell proliferation and differentiation. However, the growth of solid tumors beyond 1-2 mm in diameter requires the induction and maintenance of a tumor blood vessel supply, which is attributed in large part to the production of angiogenesis promoting growth factors by tumor cells. The mechanisms which govern the expression of angiogenesis growth factors in tumor cells are largely unknown, but dominantly acting oncogenes may have a much greater impact than hitherto realized. An example of this is the induction of expression of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) by mutant H- or K-ras oncogenes, as well as v-src and v-raf, in transformed fibroblasts or epithelial cells. Besides VEGF/VPF, mutant ras genes are known to upregulate the expression of a variety of other growth factors thought to have direct or indirect stimulating effects on angiogenesis, e.g. TGF-beta and TGF-alpha. This effect may be mediated through the ras-raf-MAP kinase signal transduction pathway, resulting in activation of transcription factors such as AP1, which can then bind to relevant sites in the promoter regions of genes encoding angiogenesis growth factors. In principle, similar events could take place after activation or overexpression of many other oncogenes, especially those which can mediate their function through ras-dependent signal transduction pathways. The regulatory effect of oncogenes on mediators of angiogenesis has some potentially important therapeutic consequences. For example, it strengthens the rationale of pharmacologically targeting oncogene products, such as mutant RAS proteins, as an anti-tumor therapeutic strategy. Such drugs may attack the source of one or more angiogenic growth factors and by doing so, function, at least in part, as anti-angiogenic agents in vivo.

Collagen promotes perianastomotic tumour growth in an experimental animal model

Local application of growth factors promote wound healing and may find clinical application for use in high-risk intestinal anastomoses such as that following anterior resection. Since viable tumour cells are present in the bowel lumen and circulation after curative colorectal cancer surgery, it is unclear what effect such factors may have on tumour recurrence. The aim of this study was to examine the effect of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) in a collagen suspension on perianastomotic tumour growth in an animal model. Significantly (P < 0.05) more animals in the collagen treated groups developed anastomotic tumours. The area of tumour growth at the anastomosis was also significantly greater for the collagen (median 14.7 mm2) and collagen + EGF (median 10.8 mm2) groups compared with controls (median 0.78 mm2). We were unable to demonstrate any promotion of tumour by growth factors alone. Collagen promotes perianastomotic tumour growth in this model and is not a suitable vehicle for growth factor application in colorectal cancer surgery.

Progression toward metastatic phenotype with loss of growth-inhibiting tumor-cell/cell interactions in vivo

Five autonomous sublines, T4-O1320, T4-O1320CY, T4-O1165, T4-O1145 and T4-O196, were established from the transplantable hormone-dependent mouse mammary tumor, TPDMT-4, by passaging under different conditions. These autonomous tumors were characterized by rapid growth in DDD virgin mice and the parental TPDMT-4 by no growth in these mice. Thus, 10(5) T4-O1320, 2 x 10(4) T4-O1320CY, 2 x 10(3) T4-O1165, 2 x 10(3) T4-O1145 and 10(3) T4-O196 cells were co-injected with 5 x 10(5) TPDMT-4 cells into virgin mice to determine whether or not hormone-dependent tumor cells influence the growth of autonomous tumor cells. TPDMT-4 cells retarded the growth of T4-O1320 and T4-O1320CY tumors but accelerated that of T4-O1165, T4-O1145 and T4-O196. Irradiated TPDMT-4 cells stimulated the growth of all the sublines except T4-O1320. In 3-dimensional collagen-gel culture, T4-O1320 and T4-O1320CY cells formed branched or stellate structures similar to normal mammary glands, as did TPDMT-4, but T4-O1165, T4-O1145 and T4-O196 cells grew as rounded masses with knobs and showed a completely different morphology. T4-O1165, T4-O1145 and T4-O196 cells, but not the others, had lung-colonizing ability. Chromosomal aberration was found in T4-O1320CY and T4-O196 but not in the others. Thus, the susceptibility of autonomous subline tumor cells to growth-inhibitory regulation from the parental hormone-dependent tumor cells correlated well with growth morphology within collagen gels and metastatic ability, but not with chromosomal aberration. The results suggest that metastatically-competent tumor-cell variants, once they appear, may have a growth advantage in hormone-dependent mammary tumors.