ABSTRACT
Despite their apparent success in pre-clinical trials, metalloproteinase (MMP) inhibitors proved to be inefficacious in clinical settings. In an effort to understand the underlying causes of this unanticipated outcome, we modeled the consequences of long-term MMP inhibition by removing one of the major players in tumorigenesis, MMP9, in two complimentary mouse models of pancreatic neuroendocrine carcinogenesis: Myc;BclXl and RIP1-Tag2. By employing gel zymography and a fluoregenic solution assay, we first established that MMP9 is expressed and activated in Myc;BclXl tumors in an interleukin-1ß-dependent manner. The genetic deletion of MMP9 in Myc;BclXl mice impairs tumor angiogenesis and growth analogous to its absence in the RIP1-Tag2 model. Notably, tumors that developed in the context of MMP9-deficient backgrounds in both models were markedly more invasive than their typical wild-type counterparts, and expressed elevated levels of pro-invasive cysteine cathepsin B. The increased invasion of MMP9-deficient tumors was associated with a switch in the spectrum of inflammatory cells at the tumor margins, involving homing of previously undetected, cathepsin-B expressing CD11b;Gr1-positive cells to the invasive fronts. Thus, plasticity in the tumor inflammatory compartment is partially responsible for changes in the expression pattern of tumor-associated proteases, and may contribute to the compensatory effects observed on MMP inhibition, hence accounting for the heightened tumor progression described in late stage clinical trials.
Subject(s)
Cell Transformation, Neoplastic/metabolism , Matrix Metalloproteinase 9/deficiency , Neuroendocrine Tumors/metabolism , Neuroendocrine Tumors/pathology , Pancreatic Neoplasms/metabolism , Animals , CD11b Antigen/genetics , CD11b Antigen/metabolism , Cathepsin B/genetics , Cathepsin B/metabolism , Cell Transformation, Neoplastic/drug effects , Cell Transformation, Neoplastic/genetics , Cell Transformation, Neoplastic/pathology , Cysteine/genetics , Cysteine/metabolism , Disease Models, Animal , GTPase-Activating Proteins/genetics , GTPase-Activating Proteins/metabolism , Inflammation/genetics , Inflammation/metabolism , Inflammation/pathology , Interleukin-1beta/genetics , Interleukin-1beta/metabolism , Leukocytes/drug effects , Leukocytes/metabolism , Leukocytes/pathology , Matrix Metalloproteinase 9/genetics , Matrix Metalloproteinase 9/metabolism , Matrix Metalloproteinase Inhibitors/pharmacology , Mice , Mice, Inbred C57BL , Neoplasm Invasiveness , Neovascularization, Pathologic/genetics , Neovascularization, Pathologic/metabolism , Neovascularization, Pathologic/pathology , Neuroendocrine Tumors/blood supply , Neuroendocrine Tumors/enzymology , Pancreatic Neoplasms/blood supply , Pancreatic Neoplasms/enzymology , Pancreatic Neoplasms/pathology , Proto-Oncogene Proteins c-myc/genetics , Proto-Oncogene Proteins c-myc/metabolism , bcl-X Protein/genetics , bcl-X Protein/metabolismSubject(s)
Angiogenesis Inhibitors/administration & dosage , Antineoplastic Agents/administration & dosage , Carcinoma, Islet Cell/blood supply , Carcinoma, Islet Cell/drug therapy , Chronotherapy , Neovascularization, Pathologic/drug therapy , Pancreatic Neoplasms/blood supply , Pancreatic Neoplasms/drug therapy , Phenylalanine/analogs & derivatives , Animals , Indoles/antagonists & inhibitors , Matrix Metalloproteinase Inhibitors , Mice , Phenylalanine/antagonists & inhibitors , Protease Inhibitors/administration & dosage , Pyrroles/antagonists & inhibitors , Receptors, Vascular Endothelial Growth Factor/antagonists & inhibitors , Thiophenes/antagonists & inhibitorsABSTRACT
Carcinomas that develop in the pancreatic islets of transgenic mice expressing the SV40 T-antigens (Tag) under transcriptional control of the rat insulin II promoter (RIP) progress through well-characterized stages that are similar to aspects of human tumor progression, including hyperplastic growth, increased angiogenesis and reduced apoptosis. The latter two stages have been associated with recurrent loss of heterozygosity (LOH) and reduced genome copy number on chromosomes 9 (LOH9) and 16 (LOH16), aberrations which we believe contribute to these phenotypes. Earlier analyses localized LOH9 to approximately 3 Mb and LOH16 to approximately 30 Mb (both syntenic with human 3q21-q25) but were limited by low throughput and a lack of informative polymorphic markers. Here we show that comparative genomic hybridization to DNA microarrays (array CGH) overcomes these limitations by allowing efficient, genome-wide analyses of relative genome copy number. The CGH arrays used in these experiments carried BACs distributed at 2-20-MB intervals across the mouse genome and at higher density in regions of interest. Using array CGH, we further narrowed the loci for LOH9 and LOH16 and defined new or previously unappreciated recurrent regions of copy-number decrease on chromosomes 6, 8 and 14 (syntenic with human chromosomes 12p11-p13, 16q24.3 and 13q11-q32, respectively) and regions of copy-number increase on chromosomes 2 and 4 (syntenic to human chromosomes 20q13.2 and 1p32-p36, respectively). Our analyses of human genome sequences syntenic to these regions suggest that CYP24, PFDN4, STMN1, CDKN1B, PPP2R3 and FSTL1 are candidate oncogenes or tumor-suppressor genes. We also show that irradiation and genetic background influence the spectrum of aberrations present in these tumors.
Subject(s)
Genome , Islets of Langerhans/pathology , Nucleic Acid Hybridization , Oligonucleotide Array Sequence Analysis , Pancreatic Neoplasms/genetics , Animals , Base Sequence , DNA Primers , Humans , Loss of Heterozygosity , Mice , Mice, TransgenicABSTRACT
L-selectin mediates homing of lymphocytes to lymph nodes (LN). Transgenic mice that express rat insulin promoter regulated simian virus 40 Tag (RIP-Tag) develop large, local cancers that metastasize to liver but not LN. To test whether this lack of LN metastases reflects their absence from the circulation, transgenic mice were produced that express Tag (T), L-selectin (L), and Escherichia coli LacZ (Z), in pancreatic beta cells. LTZ mice developed insulinomas that specifically had LN metastases; metastasis was blocked by an anti L-selectin mAb. LacZ(+) tumor cells from these LN homed to secondary LN upon transfer. These results suggest that the highly vascularized islet carcinomas are shedding tumor cells into the bloodstream, which is a necessary but insufficient condition for metastasis to occur; L-selectin can facilitate homing of such tumor cells to LN, resulting in metastasis.
Subject(s)
L-Selectin/physiology , Lymphatic Metastasis/physiopathology , Animals , Antigens, Surface/immunology , Carcinogenicity Tests , Disease Models, Animal , Immunohistochemistry , Lymphatic System , Membrane Proteins , Mice , Mice, TransgenicSubject(s)
Angiogenesis Inhibitors/administration & dosage , Brain Neoplasms/therapy , Cell Transplantation , Collagen/administration & dosage , Collagen/genetics , Peptide Fragments/administration & dosage , Peptide Fragments/genetics , Alginates , Angiogenesis Inhibitors/therapeutic use , Animals , Brain Neoplasms/blood supply , Capsules , Cell Line , Endostatins , Glucuronic Acid , Hexuronic Acids , Humans , TransfectionABSTRACT
The matrix metalloproteinase MMP-9/gelatinase B is upregulated in angiogenic dysplasias and invasive cancers of the epidermis in a mouse model of multi-stage tumorigenesis elicited by HPV16 oncogenes. Transgenic mice lacking MMP-9 show reduced keratinocyte hyperproliferation at all neoplastic stages and a decreased incidence of invasive tumors. Yet those carcinomas that do arise in the absence of MMP-9 exhibit a greater loss of keratinocyte differentiation, indicative of a more aggressive and higher grade tumor. Notably, MMP-9 is predominantly expressed in neutrophils, macrophages, and mast cells, rather than in oncogene-positive neoplastic cells. Chimeric mice expressing MMP-9 only in cells of hematopoietic origin, produced by bone marrow transplantation, reconstitute the MMP-9-dependent contributions to squamous carcinogenesis. Thus, inflammatory cells can be coconspirators in carcinogenesis.
Subject(s)
Bone Marrow Cells/enzymology , Carcinoma, Squamous Cell/pathology , Cell Transformation, Neoplastic/pathology , Matrix Metalloproteinase 9/metabolism , Skin Neoplasms/pathology , Animals , Bone Marrow Transplantation , Carcinoma, Squamous Cell/classification , Carcinoma, Squamous Cell/metabolism , Cell Differentiation , Cell Division , Disease Models, Animal , Disease Progression , Gene Deletion , Gene Expression Regulation, Neoplastic , Immunohistochemistry , In Situ Hybridization , Inflammation/enzymology , Inflammation/pathology , Keratinocytes/metabolism , Keratinocytes/pathology , Matrix Metalloproteinase 9/deficiency , Matrix Metalloproteinase 9/genetics , Mice , Mice, Knockout , Mice, Transgenic , Neoplasm Invasiveness , Papillomaviridae/physiology , Paracrine Communication , Phenotype , Skin Neoplasms/classification , Skin Neoplasms/metabolism , Stromal Cells/enzymology , Stromal Cells/transplantation , Up-Regulation , X-RaysABSTRACT
During carcinogenesis of pancreatic islets in transgenic mice, an angiogenic switch activates the quiescent vasculature. Paradoxically, vascular endothelial growth factor (VEGF) and its receptors are expressed constitutively. Nevertheless, a synthetic inhibitor (SU5416) of VEGF signalling impairs angiogenic switching and tumour growth. Two metalloproteinases, MMP-2/gelatinase-A and MMP-9/gelatinase-B, are upregulated in angiogenic lesions. MMP-9 can render normal islets angiogenic, releasing VEGF. MMP inhibitors reduce angiogenic switching, and tumour number and growth, as does genetic ablation of MMP-9. Absence of MMP-2 does not impair induction of angiogenesis, but retards tumour growth, whereas lack of urokinase has no effect. Our results show that MMP-9 is a component of the angiogenic switch.
Subject(s)
Cell Transformation, Neoplastic , Islets of Langerhans/pathology , Matrix Metalloproteinase 9/metabolism , Neovascularization, Pathologic , Pancreatic Neoplasms/blood supply , Acetamides/pharmacology , Animals , Endothelial Growth Factors/isolation & purification , Genes, Switch , Lymphokines/isolation & purification , Mice , Mice, Transgenic , Receptor Protein-Tyrosine Kinases/isolation & purification , Receptors, Growth Factor/isolation & purification , Receptors, Vascular Endothelial Growth Factor , Signal Transduction , Tissue Distribution , Vascular Endothelial Growth Factor A , Vascular Endothelial Growth FactorsSubject(s)
Neoplasms/enzymology , Neoplasms/genetics , Telomerase/metabolism , Telomere , Animals , Enzyme Activation , Humans , Mice , Neoplasms, Glandular and Epithelial/enzymology , Neoplasms, Glandular and Epithelial/genetics , Sarcoma, Experimental/enzymology , Sarcoma, Experimental/genetics , Telomerase/deficiency , Telomerase/genetics , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/physiologyABSTRACT
The functional role of glutamate decarboxylase (GAD) and its product GABA in pancreatic islets has remained elusive. Mouse beta-cells express the larger isoform GAD67, whereas human islets express only the smaller isoform GAD65. We have generated two lines of transgenic mice expressing human GAD65 in pancreatic beta-cells (RIP7-hGAD65, Lines 1 and 2) to study the effect that GABA generated by this isoform has on islet cell function. The ascending order of hGAD65 expression and/or activity in beta-cells was Line 1 heterozygotes < Line 2 heterozygotes < Line 1 homozygotes. Line 1 heterozygotes have normal glucose tolerance, whereas Line 1 homozygotes and Line 2 heterozygotes exhibit impaired glucose tolerance and inhibition of insulin secretion in vivo in response to glucose. In addition, fasting levels of blood glucose are elevated and insulin is decreased in Line 1 homozygotes. Pancreas perfusion experiments suggest that GABA generated by GAD65 may function as a negative regulator of first-phase insulin secretion in response to glucose by affecting a step proximal to or at the K(ATP)(+) channel.
Subject(s)
Glutamate Decarboxylase/biosynthesis , Insulin/metabolism , Islets of Langerhans/metabolism , Isoenzymes/biosynthesis , gamma-Aminobutyric Acid/biosynthesis , Animals , Blood Glucose/metabolism , Fluorescent Antibody Technique , Glucose Tolerance Test , Glutamate Decarboxylase/genetics , Humans , Immunohistochemistry , Insulin/genetics , Insulin Secretion , Isoenzymes/genetics , Mice , Mice, Transgenic , Promoter Regions, Genetic , Protein Biosynthesis , Rats , Reverse Transcriptase Polymerase Chain Reaction , gamma-Aminobutyric Acid/geneticsABSTRACT
CXCR5, the receptor for B lymphocyte chemoattractant (BLC), is required for normal development of Peyer's patches, inguinal lymph nodes, and splenic follicles. To test the in vivo activity of BLC in isolation of other lymphoid organizers, transgenic mice were generated expressing BLC in the pancreatic islets. In addition to attracting B cells, BLC expression led to development of lymph node-like structures that contained B and T cell zones, high endothelial venules, stromal cells, and the chemokine SLC. Development of these features was strongly dependent on B lymphocytes and on lymphotoxin alpha1beta2 and could be reversed by blocking lymphotoxin alpha1beta2. These findings establish that BLC is sufficient to activate a pathway of events leading to formation of organized lymphoid tissue.
Subject(s)
B-Lymphocytes/immunology , Islets of Langerhans/immunology , Lymphotoxin-alpha/immunology , Receptors, Cytokine/immunology , Animals , B-Lymphocytes/pathology , Chemotactic Factors/immunology , Islets of Langerhans/pathology , Lymphoid Tissue/immunology , Lymphoid Tissue/pathology , Mice , Mice, Transgenic , Receptors, CXCR5 , Receptors, ChemokineSubject(s)
Antineoplastic Agents/pharmacology , Neovascularization, Pathologic/drug therapy , Animals , Antibodies, Monoclonal/immunology , Antibodies, Monoclonal/therapeutic use , Breast Neoplasms/drug therapy , Carcinoma, Lewis Lung/drug therapy , Cyclohexanes , Cyclophosphamide/adverse effects , Cyclophosphamide/therapeutic use , Female , Humans , Maximum Tolerated Dose , Mice , Neuroblastoma/blood supply , Neuroblastoma/drug therapy , O-(Chloroacetylcarbamoyl)fumagillol , Receptor Protein-Tyrosine Kinases/antagonists & inhibitors , Receptor Protein-Tyrosine Kinases/immunology , Receptors, Growth Factor/antagonists & inhibitors , Receptors, Growth Factor/immunology , Receptors, Vascular Endothelial Growth Factor , Sesquiterpenes/adverse effects , Sesquiterpenes/therapeutic use , Tumor Cells, Cultured , Vinblastine/pharmacologyABSTRACT
To study effects of Bcl-x(L) in the pancreatic beta-cell, two transgenic lines were produced using different forms of the rat insulin promoter. Bcl-x(L) expression in beta-cells was increased 2- to 3-fold in founder (Fd) 1 and over 10-fold in Fd 2 compared with littermate controls. After exposure to thapsigargin (10 microM for 48 h), losses of cell viability in islets of Fd 1 and Fd 2 Bcl-x(L) transgenic mice were significantly lower than in islets of wild-type mice. Unexpectedly, severe glucose intolerance was observed in Fd 2 but not Fd 1 Bcl-x(L) mice. Pancreatic insulin content and islet morphology were not different from control in either transgenic line. However, Fd 2 Bcl-x(L) islets had impaired insulin secretory and intracellular free Ca(2+) ([Ca(2+)](i)) responses to glucose and KCl. Furthermore, insulin and [Ca(2+)](i) responses to pyruvate methyl ester (PME) were similarly reduced as glucose in Fd 2 Bcl-x(L) islets. Consistent with a mitochondrial defect, glucose oxidation, but not glycolysis, was significantly lower in Fd 2 Bcl-x(L) islets than in wild-type islets. Glucose-, PME-, and alpha-ketoisocaproate-induced hyperpolarization of mitochondrial membrane potential, NAD(P)H, and ATP production were also significantly reduced in Fd 2 Bcl-x(L) islets. Thus, although Bcl-x(L) promotes beta-cell survival, high levels of expression of Bcl-x(L) result in reduced glucose-induced insulin secretion and hyperglycemia due to a defect in mitochondrial nutrient metabolism and signaling for insulin secretion.
Subject(s)
Apoptosis , Gene Expression , Insulin/metabolism , Islets of Langerhans/metabolism , Mitochondria/physiology , Proto-Oncogene Proteins c-bcl-2/genetics , Animals , Apoptosis/drug effects , Blood Glucose/metabolism , Calcium/metabolism , DNA Fragmentation/drug effects , Glucose/pharmacology , Glucose Tolerance Test , Immunohistochemistry , Insulin/analysis , Insulin Secretion , Islets of Langerhans/cytology , Islets of Langerhans/ultrastructure , Membrane Potentials/drug effects , Mice , Mice, Transgenic , Potassium Chloride/pharmacology , Proto-Oncogene Proteins c-bcl-2/analysis , Rats , Thapsigargin/pharmacology , bcl-X ProteinSubject(s)
Neoplasms, Experimental , Neoplasms , Animals , Apoptosis , Cell Transformation, Neoplastic , Gene Expression Regulation, Neoplastic , Humans , Neoplasms/blood supply , Neoplasms/etiology , Neoplasms/genetics , Neoplasms/pathology , Neoplasms, Experimental/blood supply , Neoplasms, Experimental/genetics , Neoplasms, Experimental/pathology , Neovascularization, PathologicABSTRACT
Insulin receptor substrate-1 (IRS-1) is pivotal in mediating the actions of insulin and growth factors in most tissues of the body, but its role in insulin-producing beta islet cells is unclear. Freshly isolated islets from IRS-1 knockout mice and SV40-transformed IRS-1-deficient beta-cell lines exhibit marked insulin secretory defects in response to glucose and arginine. Furthermore, insulin expression is reduced by about 2-fold in the IRS-1-null islets and beta-cell lines, and this defect can be partially restored by transfecting the cells with IRS-1. These data provide evidence for an important role of IRS-1 in islet function and provide a novel functional link between the insulin signaling and insulin secretion pathways. This article may have been published online in advance of the print edition. The date of publication is available from the JCI website, http://www.jci.org.
Subject(s)
Islets of Langerhans/physiology , Phosphoproteins/physiology , Animals , Cell Line , Glucagon/metabolism , Insulin/analysis , Insulin/metabolism , Insulin Receptor Substrate Proteins , Insulin Secretion , Islets of Langerhans/chemistry , Mice , Mice, Inbred C57BL , Mice, Knockout , Phosphoproteins/analysis , Phosphoproteins/deficiency , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
Rat brain was found to contain substantial amounts of potent bioactive lipids lysophosphatidic acid (acyl LPA) (3.73 nmol/g tissue) and lysoplasmanic acid (alkyl LPA) (0.44 nmol/g tissue). The presence of alkyl LPA was confirmed by mild alkaline hydrolysis analysis and by gas chromatography/mass spectrometry analysis of the trimethylsilyl derivative. This is the first clear evidence of the occurrence of an alkyl LPA in nature. The predominant molecular species of acyl LPA are 18:1-, 18:0- and 16:0-containing species (46. 9, 22.5 and 18.8%, respectively). A significant amount of a 20:4-containing species (7.2%) was also detected in the acyl LPA fraction. We also confirmed that rat brain alkyl LPA consists of 16:0-, 18:0- and 18:1-containing species. Noticeably, either acyl or alkyl LPA is capable of stimulating neuroblastomaxglioma hybrid NG108-15 cells to elicit a Ca(2+) transient, the potencies being almost the same. Both acyl and alkyl LPAs also induce cell rounding upon addition to the cells. These results suggest that acyl and alkyl LPAs play important physiological roles as intercellular signaling molecules as well as the roles as metabolic intermediates in the nervous system.
Subject(s)
Brain Chemistry , Brain/metabolism , Lysophospholipids/metabolism , Neurons/metabolism , Animals , Calcium/metabolism , Cell Size/drug effects , Ethers/metabolism , Fatty Acids/analysis , Gas Chromatography-Mass Spectrometry , Hydrolysis , Lysophospholipids/isolation & purification , Lysophospholipids/pharmacology , Male , Neurons/drug effects , Platelet Activating Factor/analogs & derivatives , Platelet Activating Factor/pharmacology , Rats , Rats, Wistar , Signal Transduction , Tumor Cells, CulturedABSTRACT
Expression of HPV16 early region genes in basal keratinocytes of transgenic mice elicits a multistage pathway to squamous carcinoma. We report that infiltration by mast cells and activation of the matrix metalloproteinase MMP-9/gelatinase B coincides with the angiogenic switch in premalignant lesions. Mast cells infiltrate hyperplasias, dysplasias, and invasive fronts of carcinomas, but not the core of solid tumors, where they degranulate in close apposition to capillaries and epithelial basement membranes, releasing mast-cell-specific serine proteases MCP-4 (chymase) and MCP-6 (tryptase). MCP-6 is shown to be a mitogen for dermal fibroblasts that proliferate in the reactive stroma, whereas MCP-4 can activate progelatinase B and induce hyperplastic skin to become angiogenic in an in vitro bioassay. Notably, premalignant angiogenesis is abated in a mast-cell-deficient (KITW/KITWWv) HPV16 transgenic mouse. The data indicate that neoplastic progression in this model involves exploitation of an inflammatory response to tissue abnormality. Thus, regulation of angiogenesis during squamous carcinogenesis is biphasic: In hyperplasias, dysplasias, and invading cancer fronts, inflammatory mast cells are conscripted to reorganize stromal architecture and hyperactivate angiogenesis; within the cancer core, upregulation of angiogenesis factors in tumor cells apparently renders them self-sufficient at sustaining neovascularization.
Subject(s)
Carcinoma, Squamous Cell/blood supply , Mast Cells/physiology , Neovascularization, Pathologic , Animals , Chymases , Extracellular Matrix/metabolism , Humans , Inflammation Mediators/metabolism , Mast Cells/immunology , Mice , Mice, Transgenic , Serine Endopeptidases/metabolism , Tryptases , Up-RegulationABSTRACT
Solid tumors depend on angiogenesis for their growth. In a transgenic mouse model of pancreatic islet cell carcinogenesis (RIP1-Tag2), an angiogenic switch occurs in premalignant lesions, and angiogenesis persists during progression to expansive solid tumors and invasive carcinomas. RIP1-Tag2 mice were treated so as to compare the effects of four angiogenesis inhibitors at three distinct stages of disease progression. AGM-1470, angiostatin, BB-94, and endostatin each produced distinct efficacy profiles in trials aimed at preventing the angiogenic switch in premalignant lesions, intervening in the rapid expansion of small tumors, or inducing the regression of large end-stage cancers. Thus, anti-angiogenic drugs may prove most efficacious when they are targeted to specific stages of cancer.
Subject(s)
Antineoplastic Agents/pharmacology , Carcinoma, Islet Cell/drug therapy , Neovascularization, Pathologic/prevention & control , Pancreatic Neoplasms/drug therapy , Angiostatins , Animals , Anticarcinogenic Agents/pharmacology , Apoptosis , Carcinoma, Islet Cell/blood supply , Carcinoma, Islet Cell/pathology , Carcinoma, Islet Cell/prevention & control , Collagen/pharmacology , Cyclohexanes , Disease Progression , Drug Evaluation, Preclinical , Endostatins , Female , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , Neoplasm Staging , O-(Chloroacetylcarbamoyl)fumagillol , Pancreatic Neoplasms/blood supply , Pancreatic Neoplasms/pathology , Pancreatic Neoplasms/prevention & control , Peptide Fragments/pharmacology , Phenylalanine/analogs & derivatives , Phenylalanine/pharmacology , Plasminogen/pharmacology , Sesquiterpenes/pharmacology , Thiophenes/pharmacologyABSTRACT
There is considerable controversy concerning the importance of tumor-derived angiogenic factors to the neovascularization of solid tumors. Tumor, endothelial, and stromal expression of vascular endothelial growth factor (VEGF) have been hypothesized to be critical for tumor angiogenesis. To determine the relative contribution of tumor versus nontransformed tissue expression of VEGF to tumor growth, we used gene targeting and cre-loxP recombination to generate embryonic stem cell lines in which VEGF can be conditionally deleted. These lines were used to derive mouse embryonic fibroblast lines with null mutations in both alleles of VEGF. Upon immortalization and H-ras transformation, we used these VEGF null fibroblasts to make fibrosarcomas in immunocompromised mice. We report that tumorigenic VEGF expression is critical for ras-mediated tumorigenesis, and the loss of tumorigenic expression causes dramatic decreases in vascular density and vascular permeability and increases in tumor cell apoptosis.
Subject(s)
Capillary Permeability , Endothelial Growth Factors/physiology , Lymphokines/physiology , Neoplasms, Experimental/blood supply , Animals , Cell Hypoxia , Endothelial Growth Factors/genetics , Endothelium, Vascular/pathology , Gene Targeting , Genes, ras , Lymphokines/genetics , Mice , Neoplasms, Experimental/etiology , Neovascularization, Pathologic/etiology , Vascular Endothelial Growth Factor A , Vascular Endothelial Growth FactorsABSTRACT
Apoptosis, the process of programmed cell death, plays a critical role in many normal and pathological (disease) processes. In normal tissues, apoptosis functions in the homeostatic maintenance of proper tissue and organ size by eliminating aged cells to offset the birth of new cells that arise by mitosis. In disease, apoptosis can affect the pathological process is two disparate ways. There are diseases that have too much apoptosis such as autoimmune diabetes and Alzheimer's, or those that have too little apoptosis, such as cancer. This review will focus on the latter and, more specifically, detail and summarize some important lessons learned about apoptosis and cancer from studying a transgenic mouse model of islet cell carcinoma, RIP-Tag, as outlined below.
Subject(s)
Apoptosis , Insulinoma/pathology , Pancreatic Neoplasms/pathology , Animals , Antigens, Polyomavirus Transforming/genetics , Cell Transformation, Neoplastic , Humans , Islets of Langerhans/pathology , Mice , Mice, Transgenic , Neovascularization, Pathologic , Simian virus 40/geneticsABSTRACT
The epidemiology and histopathology of human cancers and studies of animal models of tumorigenesis have led to a widely-accepted notion that multiple genetic and epigenetic changes have to accrue for the successful development of a malignant phenotype. Tumor growth and expansion requires an ability not only to proliferate, but also to down-modulate cell death (apoptosis) and activate angiogenesis to produce a tumor neovasculature. This review will describe the interplay between apoptosis and proliferation, as well as the characteristics of the angiogenic phenotype in two transgenic mouse models of multi-step tumorigenesis, namely, pancreatic islet cell carcinomas and squamous cell carcinomas of the skin.