Tumor angiogenic activity (TAA) production in vitro and growth in the nude mouse by human malignant melanoma

Extracellular vesicles as emerging intercellular communicasomes

All living cells release extracellular vesicles having pleiotropic functions in intercellular communication. Mammalian extracellular vesicles, also known as exosomes and microvesicles, are spherical bilayered proteolipids composed of various bioactive molecules, including RNAs, DNAs, proteins, and lipids. Extracellular vesicles directly and indirectly control a diverse range of biological processes by transferring membrane proteins, signaling molecules, mRNAs, and miRNAs, and activating receptors of recipient cells. The active interaction of extracellular vesicles with other cells regulates various physiological and pathological conditions, including cancer, infectious diseases, and neurodegenerative disorders. Recent developments in high-throughput proteomics, transcriptomics, and lipidomics tools have provided ample data on the common and specific components of various types of extracellular vesicles. These studies may contribute to the understanding of the molecular mechanism involved in vesicular cargo sorting and the biogenesis of extracellular vesicles, and, further, to the identification of disease-specific biomarkers. This review focuses on the components, functions, and therapeutic and diagnostic potential of extracellular vesicles under various pathophysiological conditions.

Nanodelivery strategies in cancer chemotherapy: biological rationale and pharmaceutical perspectives

Nanotechnology is revolutionizing our approach to drug delivery, a key determinant of drug efficacy. Here, we present cancer drug delivery strategies that exploit nanotechnology, providing first an overview of tumor biology aspects that critically affect the design of drug delivery carriers, namely the enhanced permeability and retention effect, the lower tumor extracellular pH and tumor-specific antigens. In general, nanoscience-based approaches have circumvented limitations in the delivery of cancer therapeutics, related to their poor aqueous solubility and toxicity issues with conventional vehicles and resulted in improved pharmacokinetics and biodistribution. Included in the discussion are promising examples and pharmaceutical perspectives on liposomes, nanoemulsions, solid lipid nanoparticles, polymeric nanoparticles, dendrimers, carbon nanotubes and magnetic nanoparticles. As the cardinal features of the ideal multifunctional cancer drug nanocarrier are becoming clear, and drug development challenges are proactively addressed, we anticipate that future advances will enhance therapeutic outcomes by refining the delivery and targeting of complex payloads.

Immunobiology of malignant gliomas

The immune system of patients with malignant gliomas is profoundly suppressed. The suppression involves both the cellular and humoral immunity and it is mainly attributable to selective depletion and malfunction of helper T cells. Malignant glioma cells express potent immunosuppressive factors such as transforming growth factor-beta(2), inteleukin-10 and prostaglandin E(2). Malignant glioma cells also produce chemoattractants and immunostimulatory cytokines which may activate the immune cells. However, the production of these stimulatory cytokines is not self-destructive to glioma cells because of the immunosuppression. Rather, the tumour cells use them to gain a growth advantage. Indeed the cytokines may act as a growth stimulator of the tumour cells themselves (autocrine mechanism), they may act as angiogenic factors to endothelial cells (paracrine mechanism) or induce the attracted immune cells to secrete angiogenic factors. Some cytokines produced by malignant glioma cells are known to be growth inhibitory to normal astrocytes. Recent studies on tumour suppressor genes suggest a close link between the aberrant genes and the immunobiologic features of malignant glioma cells.

Early effects of boron neutron capture therapy on rat glioma models

Early effects of boron neutron capture therapy (BNCT) on malignant glioma are characterized by reduction of the enhancement area and regression of the peritumoral edema radiologically. The aim of this study was to investigate the early histological changes of tumors and inflammatory cells after BNCT in the rat brain. Rats were treated with BNCT using boronophenylalanine (BPA) 7 days after implantation of C6 glioma cells. The tumors were assessed with magnetic resonance imaging and histopathological examination at 4 days after BNCT. The mean tumor volumes were 39 +/- 2 mm3 in the BNCT group and 134 +/- 18 mm3 in the control group. In the BNCT group, tumor cells showed a less pleomorphic appearance with atypical nuclei and mitotic figures. The Ki-67 labeling index was 6.5% +/- 4.7% in the BNCT and 35% +/- 3.8% in the control group. The reactions of the inflammatory cells were examined with ED-1 as macrophage marker and OX42 as microglia marker. ED-1- and OX-42-positive cells were reduced both in the core and the marginal area of the tumor in the BNCT group. It is suggested that BNCT reduced tumor progression by suppression of proliferation. Inhibition of the activated macrophages may relate to reduced peritumoral edema in the early phase.

Increased laser Doppler flow in skin tumors corresponds to elevated vessel density and reactive hyperemia

BACKGROUND/PURPOSE

Tumor angiogenesis plays a key role in tumor growth and formation of metastasis. Quantitative analysis of tumor blood flow is a prerequisite for developing novel treatment strategies such as antiangiogenic and antivascular treatment options. Laser Doppler flow in malignant melanomas has been shown to be increased compared with normal skin and melanocytic nevi. This study investigated whether this phenomenon is originated by elevated blood vessel density or by reactive hyperemia.

METHODS

Laser Doppler flow was studied in 35 melanocytic nevi, 22 malignant melanomas and three basal cell carcinomas. After excision digital imaging analysis was performed in microtome sections (factor VIII-associated antigen and CD 31 labelled). The ratio of vessel area in histological sections from tumor tissue and in non-lesional skin was calculated and related to Doppler flow values.

RESULTS

Malignant melanomas demonstrated an enlargement of vessel cross-sectional area by factor 3.7+/-1.9 and of Doppler flow by factor 10.56+/-10.7, and melanocytic nevi accomplished increase of vessel cross-sectional area by factor 1.7+/-0.9 and of Doppler flow by factor 2.7+/-3.5.

CONCLUSION

The laser Doppler flow is influenced by the number and the velocity of erythrocytes in the tissue. The greater increase of laser Doppler flow than of vessel density in histological sections demonstrates that the flow signal in skin tumors is caused by neovascularization as well as by functional hyperemia. Laser Doppler perfusion imaging is a useful method for non-invasive, repeated and quantitative assessment of tumor vascular network and effects of antiangiogenic treatment directed vs. tumor vasculature in vivo, but it cannot distinguish between increased vessel density and reactive hyperemia.

Angiogenesis, lymphangiogenesis, and melanoma metastasis

The induction of angiogenesis is a critical point in the development of most human tumors - including melanomas. Some of the earliest studies in the field of tumor angiogenesis showed that transplantation of human melanoma fragments into the hamster cheek pouch stimulated blood vessel growth. Since then, numerous studies have demonstrated that human melanomas also induce angiogenesis. The prognostic importance of the degree of melanoma vascularization, however, has remained controversial. Elevated expression of several angiogenic factors, including vascular endothelial growth factor, basic fibroblast growth factor, and interleukin-8, has been detected in primary cutaneous melanomas, and the importance of these mediators in promoting melanoma angiogenesis and metastasis has been confirmed in tumor xenotransplant models. Based upon these findings, several clinical trials of angiogenesis inhibitors have been initiated in human melanoma patients and are currently underway. Recent experimental evidence indicates that tumor-associated lymphangiogenesis also plays an important role in mediating tumor spread to regional lymph nodes. These observations have important implications for prognosis and treatment of human melanomas.

Tumor-associated macrophages: a molecular perspective

The "macrophage balance hypothesis" was proposed in the early 1990s to depict the complex relationship that tumor-associated macrophages (TAM) have with the neoplastic cells of the tumor. TAM represent a prominent component of the mononuclear leukocyte population of solid tumors, which displays an ambivalent relationship with tumors. They originate in the circulation and are recruited to the tumor site by tumor-derived attractants such as chemokines and interact with the tumor cells and preferentially localize at the tumor-host tissue interface, in regions often associated with low oxygen tensions. The tumor microenvironment, including cytokines and hypoxia, regulates the localization and function of TAM. Emerging evidence starts to define the molecular basis for the peculiar functional phenotype of TAM and identifies possible therapeutic targets.

Immunohistochemical assessment of tumor vascularity in recurrent Clark II melanomas using antibody to type IV collagen

Thin melanomas, measuring 0.76 mm or less, are generally associated with an excellent prognosis. However, a certain subset of these seemingly innocuous lesions have been reported to develop recurrences. Therefore, the predictive values of currently accepted prognostic indicators have been questioned in thin melanomas. Several studies concerning tumor vascularity in melanoma and certain non-melanocytic malignancies suggest that the degree of vascularization correlates with growth rate and biologic aggressiveness. In the present study, we determined the vascularity of a small group of Clark level II melanomas that resulted in recurrence, and compared these results to an equal number of nonrecurrent lesions with similar prognostic indicators. Blood vessels were labeled by immunoperoxidase staining techniques for Type IV collagen, and quantified by image analysis. No statistical difference was found between the two groups when mean blood vessel counts and percent vascular area were measured. The recurrent tumors had a mean PVA of 4.68 compared to 4.34 for the nonrecurrent group (p = 0.677). The mean blood vessel count beneath the recurrent group was 29.6 per 400 x field, and the corresponding value for the nonrecurrent group was 31.8 (p = 0.681). Our data is preliminary within this limited group of tumors, yet it suggests that tumor vascularity is not a distinctive prognostic indicator by which eventual outcome can be predicted in thin Clark level II malignant melanomas.

Macrophage-derived angiogenesis factors

A majority of angiogenic factors has been shown to be produced by macrophages. This review will give a concise description of their biochemical nature, their isolation from macrophages and their angiogenic activity. Among the factors with mitogenic effects on endothelial cells are basic fibroblast growth factor (bFGF), transforming growth factor-alpha (TGF-alpha) and very probably insulin-like growth factor-1 (IGF-1). Other secretory products such as angiotropin and human angiogenic factor (HAF) are nonmitogenic but promote angiogenesis by inducing migration of endothelial cells. Prostaglandins, platelet-derived growth factor (PDGF), granulocyte-macrophage- and granulocyte-colony stimulating factor (GM-CSF, G-CSF), interleukin 6 (IL-6) and angiotensin converting enzyme (ACE) have also been shown to be angiogenic, but their mode of action is still to be clearly defined. As the extracellular matrix appears to be involved in the control of angiogenesis, macrophage-derived factors that can alter this structure via degradation or via the clotting system will also be discussed. Tumor necrosis factor alpha (TNF-alpha), interleukin 1 (IL-1) and transforming growth factor-beta (TGF-beta) have complex actions on endothelial cells, and can partially inhibit angiogenesis. Among the factors which solely inhibit neovascularization are the interferons. As it is not known whether all of these factors play a role in angiogenesis in vivo attempts to detect them in situ during the course of neovascularization will be described. Finally macrophages will be discussed as cells that may not be mandatory for each phase of the angiogenic process but whose angiogenic capabilities are comprehensive and unsurpassed by any other cell.

Gangliosides, copper ions and angiogenic capacity of adult tissues

The report summarizes the work of our laboratory aimed at improving the understanding of the angiogenic response of adult tissues, an event that transforms a micro-embolus of neoplastic cells into a growing metastasis. Attention has been focused on tumor-induced angiogenesis. The following aspects of the subject are discussed: (a) relationship between size of vascular network and tumor growth rate or tumor cell population; (b) angiogenic capacity of tumors and role that prostaglandin E1 may have as an angiogenesis factor; (c) relationship between acquisition of angiogenic capacity and neoplastic transformation of a cell population; (d) modification of tissue composition at the onset of angiogenesis; (e) behaviour of copper ions and copper carriers in the course of the angiogenic response; (f) the influence of gangliosides on endothelial cell motility, survival and growth in vitro; (g) modulation of the angiogenic response by gangliosides (GM1, GT1b) in vivo.

Vascular architecture of melanocytic skin tumors. A quantitative immunohistochemical study using automated image analysis

The present study examines the distribution of blood vessels in melanocytic skin tumors. Fresh frozen sections of 11 cases each of benign nevocellular nevus, primary malignant melanoma and metastatic malignant melanoma were stained with the endothelium-specific monoclonal antibody BMA 120 and evaluated by an automated image analysis system. Additionally, the proliferative activity was assessed in parallel sections using Ki 67 monoclonal antibody. There were only slight differences between the diagnostic groups as to the vascular distribution in the tumor center, but there were remarkable differences in the connective tissue at the base of the lesions: The area occupied by small vessels (minimum diameter less than 20 microns) was 0.3 +/- 0.05% in benign nevi, 0.6 +/- 0.05% in primary malignant melanoma, and 1.2 +/- 0.10% in metastatic malignant melanoma (U-test: p less than or equal to 0.05). The proliferative activity within each lesion showed a strong positive correlation with the number of small vessels at the base of the tumor (linear regression analysis: r = 0.86; p less than or equal to 0.0001). The findings demonstrate that neovascularization in malignant melanocytic tumors takes place predominantly in the surrounding host tissue and is closely related to the proliferative activity.

What's new in the local immune response in cancer?

Malignant tumors in humans are commonly associated with an inflammatory infiltrate. The mechanisms that account for the accumulation of T-lymphocytes and macrophages--these cells comprise the major components of tumor infiltrates--in the vicinity of a growing tumor are not fully understood. Tumor specific and immunogenic antigens could not be demonstrated in most solid tumors of humans, in contrast to several experimental tumor models. Thus it is not proven in human malignancies that neoantigens expressed on malignant cells are the signal which initiates an inflammatory response that, immunohistologically, is comparable to mononuclear infiltrates present in allograft rejection. A variety of nonspecific factors including lymphokines released by tumor cells may also account for the accumulation of inflammatory cells at the tumor site. The difficulties to evaluate the functional role of the "local immune response" for tumor and host are even greater. Most tumors progress in the presence of mononuclear infiltrates. Do they progress in spite of or because of the action of the local immune response? Clinical, immunopathological, and experimental data suggest that both is right, and that at least four distinct properties of tumor-associated immune reactions exist: Regression, Selection, Modulation and Progression. These distinct properties will be discussed below, using mainly the malignant melanoma of the skin as a model for a malignant tumor in humans.

Immunolocalization of an angiogenic factor (HAF) in normal, inflammatory and tumor tissues

The distribution of a novel human angiogenic factor (HAF) (Schulze Osthoff et al., 1987) has been investigated on various human cell lines, isolated blood cells as well as in normal, inflammatory and tumor tissues. Localization was performed by using the monoclonal antibody (MAb) 5F4 directed against HAF. It was found that 30% of freshly isolated human monocytes expressed the 5F4 antigen. The number of positive cells increased to 75-90% on day 4 to 7 upon culture and then decreased. Twenty percent of freshly isolated human lymphocytes also stained positively, whereas granulocytes and platelets were negative. In cryostat sections of normal human tissue (skin, lung, liver, spleen, placenta) 5F4 is positive with capillary endothelial cells and few macrophages. In inflammatory tissue derived from gingivitis and rheumatoid arthritis, more macrophages than in normal tissues and less endothelial cells were positive. In tumor tissues some endothelial cells and a subset of tumor-infiltrating macrophages expressed the antigen. Tumor cells were positive in advanced melanomas, but only occasionally in stomach carcinomas. We conclude that the angiogenic factor is produced mainly by a subset of inflammatory macrophages which appear to be the principal source of HAF in regenerating or growing tissues.

Association of macrophages detected with monoclonal antibody 25 F 9 with progression and pathobiological classification of gastric carcinoma

Using monoclonal antibody 25 F 9, which reacts with a determinant of mature macrophages, the inflammatory infiltrate of 66 gastric carcinomas was evaluated using a counting grid. The ratio tumor cells/macrophages was determined for every tumor. For a threshold value of 5, carcinomas with a better prognosis, such as the intestinal type according to Lauré, the expanding type according to Ming and the differentiated carcinomas according to the WHO had a significantly smaller relative content of 25 F 9-positive macrophages (a minimum of P less than 0.05) than the diffuse type, infiltrative type, and undifferentiated carcinomas. Furthermore, the relative macrophage content tended to increase with the stage of carcinomas spread (P less than 0.1). The results suggested that 25 F 9-positive macrophages in gastric carcinoma are of greater significance in tumor spread than in any defensive reaction against the tumor.

Purification and characterization of a novel human angiogenic factor (h-AF)

Serum-free supernatants of the human melanoma cell line A-375/2 contain an angiogenic activity as detected by the chorioallantois membrane assay which does not induce proliferation of cultured endothelial cells. This human angiogenic factor (h-AF) was purified by immunoaffinity chromatography as well as by conventional chromatographic procedures. A monoclonal antibody designated 5F4 was raised against h-AF, which binds but does not neutralize angiogenic activity. h-AF consists of a protein at MW 67 kD which focuses at pH 5.0. By biological and biochemical criteria it is shown that h-AF differs from other known growth factors.

Angiogenesis and the skin

This communication reviews the circumstances of angiogenesis in the embryo and in the adult. Various biochemical and physical factors reported to influence new blood vessel growth are discussed. Particular emphasis is given to angiogenesis occurring in the skin. Evidence concerning an epidermal stimulus for vascular growth is examined.

Neovascularization in human cutaneous melanoma: a quantitative morphological and Doppler ultrasound study

A study of tumour blood flow in 36 patients with 38 malignant melanomas using Doppler Ultrasound flowmetry has shown that tumour blood flow can be detected in most melanomas more than 0.9 mm thick, and is absent in most melanomas less than this thickness. Histological quantitation of blood vessels using lectin staining to delineate vascular endothelium and automated image analysis has shown a high degree of correlation between vascularity at the tumour base and tumour thickness. Since it is likely that the development of a vascular plexus at the tumour base is a prerequisite for dissemination, the development of these blood vessels may prove to be an independent prognostic factor for thin melanomas. This work also provides a new model for dynamic, in vivo investigation of the vascularity of human tumours.

Progression from hormone dependence to autonomy and angiogenesis in mouse mammary tumours

The transplantable pregnancy-dependent mammary tumour (TPDMT-4), the related hormone-dependent (TPDMT-4EP) and autonomous (T4-0I320 and T4-0I96) subline tumours, and the mammary glands from DDD mice were compared for angiogenic activity on the rabbit cornea by tissue implantation. The TPDMT-4EP tumour was established by serially transplanting TPDMT-4 tumour fragments in oestradiol plus progesterone treated mice. The T4-0I320 and T4-0I96 tumours directly derived from the TPDMT-4 and TPDMT-4EP tumours, respectively. Angiogenic activity was graded by macroscopic and microscopic examinations into 3 classes; negative, partial and complete angiogenesis. These tumours were comparable to mammary glands in activity and induced complete angiogenesis in only 15-23% of the implants. However, when partial and complete responses were combined as positive angiogenesis, TPDMT-4, T4-0I320, TPDMT-4EP and T4-0I96 tumour implants were angiogenic in 25, 29, 42 and 54%, respectively. The T4-0I96 tumour was significantly more angiogenic than the parent tumour but this was not so for the TPDMT-4EP tumour. Spontaneous C3H mouse mammary tumours, human gliomas from nude mice, rat Walker 256 carcinomas and rabbit VX-2 tumours induced complete angiogenesis in 54, 63, 59 and 92% of the implants, respectively. The results suggest that the TPDMT-4 tumour is unique in being weakly angiogenic and able to progress toward greater autonomy with or without augmented angiogenic activity in different conditions.

Phenotypic dynamics of tumor progression in human malignant melanoma

The phenotypic changes in human melanoma cells during the course of tumor progression were studied with monoclonal antibodies (MAbs) against the melanoma-associated antigens (MAA) M.2.2.4, H.2.8.10, K.1.2, A.1.43, and A.10.33, and HLA-(A,B,C and D). Cryostat sections of 172 primary melanomas of the skin, 157 melanoma metastases and 56 nevi were investigated with an indirect immunoperoxidase method. Phenotypic heterogeneity was observed within lesions at all stages, and also within different tumors of the same patients. Despite this heterogeneity, principles of antigen expression were found. From the reaction pattern of MAbs, the following classifications of antigens were derived: "constitutive" markers of nevomelanocytic cells (M.2.2.4 and H.2.8.10) were found expressed over a wide range of local and systemic tumors. One MAA, K.1.2 (Suter et al., 1985), that declines with progression of melanoma, was classified as an "early" antigen, whereas MAA that appear in primary melanoma in proportion to invasiveness, and which are expressed in metastases of lymph nodes and visceral organs (A.1.43, and A.10.33), were classified as "late" markers of tumor progression. HLA-antigens were classified as "intermediate" markers, HLA-A,B,C, as an "early-intermediate", and HLA-DR as a "late-intermediate" marker. The occurrence of class II HLA, A.1.43-, and A.10.33-positive tumor cells in primary melanoma indicates a high metastatic potential of tumors, independent of tumor thickness. The data show that local and systemic progression of melanoma is associated with qualitative changes in tumor cells which can be recognized by MAbs.

Tumor angiogenesis

The hypothesis that tumors are angiogenesis dependent has, in the past decade, generated new investigations designed to elucidate the mechanism of angiogenesis itself. Many laboratories are now engaged in this pursuit. Some are studying angiogenesis that occurs in physiological situations, whereas others are interested in angiogenesis that dominates pathological conditions. These efforts have led to (1) the development of bioassays for angiogenesis; (2) the partial purification and, in one case, the complete purification of angiogenic factors from neoplastic and non-neoplastic cells; (3) the development of new polymer technology for the sustained release of these factors and other macromolecules in vivo; (4) the cloning and long-term culture of capillary endothelial cells; (5) the demonstration of the role of nonendothelial cells, such as mast cells in modulating angiogenesis; (6) the discovery of angiogenesis inhibitors; and (7) the demonstration that certain animal tumors will regress when angiogenesis is inhibited. The effects of angiogenesis inhibitors provide perhaps the most compelling evidence for the role of angiogenesis in tumor growth. It is conceivable that the original effort to understand the role of angiogenesis in tumor growth will also lead to the use of angiogenesis inhibitors as a new class of pharmacologic agents in a variety of non-neoplastic diseases such as arthritis, psoriasis, and ocular neovascularization. However, much work remains to be done before it will be possible to understand (1) the regulatory systems that govern capillary density in normal tissues; (2) the factors that maintain the viability of microvascular endothelium; (3) the development of the vascular system itself; and (4) the mechanism by which vascular regression occurs, both in the embryo and in the postnatal organism. A knowledge of the mechanisms which underlie these normal processes may help to enlarge our comprehension of tumor angiogenesis.

The pattern of the mononuclear infiltrate as a prognostic parameter in flat superficial spreading melanomas

The mononuclear cell infiltrate of 90 superficial spreading melanomas (SSM) of less than or equal to 1.5 mm thickness was analyzed at different locations around and within the tumors. All patients had been followed for at least 5 years, and 20 (22%) had developed metastases. A correlation between the overall inflammatory response in the histologic sections and the prognosis was not observed, nor could a significant distinction be made between metastasizing and nonmetastasizing melanomas when the mononuclear cell infiltrate was analyzed at different locations. A significant clustering of metastasizing tumors was, however, observed in the subgroup with a relatively strong infiltrate within the tumor compared with the overall infiltrate. From this observation, a semiquantitative description of the pattern of the infiltrate was established. It provides an additional parameter for prognostication in flat SSMs and it raises new questions about the role of the local host-tumor interaction.

Human lung tumour cell line adapted to grow in serum-free medium secretes angiogenesis factor

A human lung tumour cell line has been grown in serum-free medium for 12 months and during this period cells were subcultured every 4 days. The culture medium contained an angiogenesis factor which has been purified and shown to be similar to that isolated from other sources including solid tumours. This is the first report that demonstrates de novo synthesis and secretion of angiogenesis factor by a cell line adapted to grow in a serum-free medium.