The extracellular matrix in oral Kaposi sarcoma (AIDS): the immunohistochemical distribution of collagens type IV, V, VI, of procollagens type I and III, of laminin and of undulin

Sarcoma Tumor Microenvironment

Components of the tumor microenvironment (TME) are known to play an essential role during malignant progression, but often in a context-dependent manner. In bone and soft tissue sarcomas, disease-regulatory activities in the TME remain largely uncharacterized. This chapter introduces the cellular, structural, and chemical composition of the sarcoma TME from a pathobiological and therapeutic perspective.Sarcomas are malignant tumors with diverse features when it comes to primary tumor appearance, metastatic potential, and response to treatment. Many of the classic subtypes are mainly composed of malignant cells and are therefore assumed to be committed to autocrine signaling. Some of the tumors are infiltrated by immune cells and contain necrotic areas or excessive amounts of extracellular matrix (ECM) that regulates tissue stiffness and interstitial fluid pressure. Vascular invasion and blood vessel characteristics can in some instances be considered in the prognostic setting.Further insights into the disease-regulatory activities of the sarcoma TME will provide essential knowledge on how to develop successful combination treatments targeting not only malignant cells, but also their routes of nutrition and ability to shield themselves toward existing therapy.

Kaposi's Sarcoma: A Clinico-Pathologic Overview

A careful overview of the classical appearances of Kaposi's sarcoma (KS) as well as of its variants were reviewed from the clinical and pathological point of view. The growth phases (stages) and the cellular patterns were histopathologically compared with emphasis on the developmental progression of disease as well as mitotic activity. Other morphological aspects were also assessed such as the features of the early phases and the incidence of hyaline bodies. One hundred and forty-three lesions from 96 patients mostly of the Italian sporadic type were investigated. A complete list of those entities which should be considered in differential diagnosis is shown and the dilemma of whether KS is a neoplasia or a hyperplasia is discussed.

Absence of human herpes virus-8 (HHV8) in nephrogenic systemic fibrosis

Background

Nephrogenic systemic fibrosis (NSF) is a fibrosing disorder that exhibits CD34 expression in the majority of lesional spindle cells. Several features of NSF bear similarity to Kaposi sarcoma.

Findings

Skin lesions procured from two male NSF patients were found to be negative for HHV8 (LNA-1) by means of immunohistochemsitry.

Conclusion

This finding negates a role for HHV8 in the pathogenesis of NSF.

The elongated first fibronectin type III domain of collagen XIV is an inducer of quiescence and differentiation in fibroblasts and preadipocytes

Collagen XIV (CXIV) is a fibril-associated collagen that is mainly expressed in well differentiated tissues and in late embryonic development. Because CXIV is almost absent in proliferating and/or dedifferentiated tissues, a functional role in maintaining cell differentiation is suspected. We demonstrate antiproliferative, quiescence- and differentiation-inducing effects of human CXIV and its recombinant fragments on mesenchymal cells. In primary human fibroblasts, in mouse 3T3 fibroblasts and in 3T3-L1 preadipocytes, CXIV reduced de novo DNA synthesis by 75%, whereas cell numbers and viability remained unaltered. Cells showed no signs of apoptosis, and maximal proliferation was restored when serum was supplemented, thus indicating that CXIV induced reversible cellular quiescence. Exposure of fibroblasts to CXIV in vitro led to cellular bundles and clusters. CXIV also triggered trans-differentiation of 3T3-L1 preadipocytes into adipocytes, as could be shown by lipid accumulation and by expression of the glucose transporter Glut4. These effects were also observed with the amino-terminal recombinant fragment Gln(29)-Pro(154) that harbors the first fibronectin type III domain and a 39-amino-acid extension, whereas no activity was found for all other recombinant CXIV fragments. Based on these finding the development of small molecular analogs that modulate fibroblast cell growth and differentiation, e.g. in wound healing and fibrosis, seems feasible.

Expression of adhesion molecules in endemic and epidemic Kaposi's sarcoma

Spindle cells and vascular endothelium in nodular lesions of AIDS associated (epidemic) and endemic Kaposi's sarcoma showed similar immunohistochemical patterns of expression for cell adhesion molecules and extracellular matrix proteins. Spindle cells as well as endothelium also expressed both alpha 5 and alpha V integrin subunits and ICAM-1 suggesting a possible role for inflammatory cytokines in spindle cell formation. The spindle cell compartment was rich in collagen, laminin, fibronectin and tenascin suggesting an important reactive component in the evolution of Kaposi's sarcoma. The lack of thrombospondin expression in the spindle cells favours the contention that they could be transitional, proliferating cells of endothelial origin. Specific expression of tat protein was not seen suggesting minimal if any HIV replication in these lesions. Our findings suggest similar histopathogenetic mechanisms for endemic and epidemic Kaposi's sarcoma. The clinically more malignant features of most AIDS related cases may reflect an important effect of systemic and focal cytokines in HIV patients and possibly other cofactor(s), i.e. tat protein in the induction and growth of the lesions.

Immunoelectron microscopy shows an atypical pattern and a quantitative shift of collagens type I, III and VI in oral Kaposi's sarcoma of AIDS

The localization of collagen types I, III and VI in normal human alveolar and palatal mucosa and in oral Kaposi's sarcoma (KS) was studied by light microscopy and cryo-immunoelectron microscopy. Normal oral mucosa revealed two different types of organization. The upper connective tissue stroma contained a loose reticular network mainly composed of collagen types III and VI, while collagen type I immunostaining predominated in the deeper stroma. Ultrastructurally, in the KS tumour stroma, a loose pattern of individual thin collagen fibrils was noted. These often fanned out at their ends showing a filamentous substructure. The fibrils consisted predominantly of collagen type I similar to individual fibrils of normal oral mucosa. However, there was a marked loss of thick fibre bundles of collagen types I and III in KS compared with normal oral mucosa, whereas collagen type VI was markedly increased and found preferentially in clusters and strands around cross-striated fibrils that often spanned the distance between single collagen fibres. The abundance of collagen type VI in a pattern similar to early stages of wound healing suggests that the KS stroma resembles an early organizational stage of the interstitial and vascular extracellular matrix subject to a high rate of collagen turnover. This character of the KS stroma appears to result from a continuous auto-and paracrine stimulation of cell growth and collagen synthesis and provides an excellent model to study the structural arrangement of collagen type VI in relation to the fibrillar collagen types I and III.

Distribution of basement membrane-associated heparan sulfate proteoglycan in idiopathic and AIDS-associated Kaposi's sarcoma

In the present study we analyzed the immunohistochemical distribution of different major basement membrane (BM) components with special emphasis on the BM-associated heparan sulfate proteoglycan (HSPG) in early and late stages of Kaposi's sarcoma (KS), both of idiopathic and AIDS-associated origin. In early KS all BM components tested were found surrounding the small clefts of tumour vessels. Heparan sulfate proteoglycan showed the weakest and often fragmented pattern of staining. In the late, nodular sarcomatous form of KS individual tumour cells were surrounded by a BM composed of collagen IV, laminin and fibronectin, while heparan sulfate proteoglycan was not detectable in most cases. Neither between idiopathic and AIDS-associated KS nor between cutaneous and visceral lesions were significant differences in the staining pattern. Our findings of a rather selective expression of various BM-components and the known distribution in normal blood and lymphatic capillaries raises the hypothesis that KS-cells may be derived from cells of lymphaticovenous differentiation.

Non-pigmented oral kaposi's sarcoma (AIDS). Report of two cases

In 90% of cases of AIDS-associated Kaposi's sarcoma (KS), the lesion is observed in the oral cavity. Oral KS usually reveals distinct clinical features characterized by a brown-bluish or otherwise pigmented appearance. The histological features are identical to classical KS. The occurrence of a non-pigmented oral KS in 2 male homosexual patients has prompted the present case reports. Clinicians should be aware that not all cases of AIDS-associated oral KS appear as brown or purplish tumors but may present without any discoloration.

Histogenesis of Kaposi's sarcoma and angiosarcoma of the face and the scalp

This study reviews data on the histogenesis of Kaposi's sarcoma and angiosarcoma derived from clinical features, histology, electron microscopy, enzyme histochemistry, and immunochemistry of both diseases. Their hemorrhagic clinical appearance contrasts the predominantly lymphatic histologic features of vessels in early lesions. Investigations performed to resolve the debate whether these tumors arise from blood vessel or lymphatic endothelium show remarkably similar results for both conditions. Electron microscopy reveals Weibel - Palade bodies in a minority of cases, but features consistent with less well-differentiated blood vessel endothelium may be seen in a greater proportion of tumors. Enzyme histochemistry generally shows absence of adenosine triphosphatase and alkaline phosphatase in tumor cells; a pattern of enzymes similar to that found in normal lymphatic endothelium. Conflicting data arises from the large number of immunohistochemical studies performed on both conditions. Factor VIII-related antigen and Ulex europaeus agglutinin-I have been most frequently employed, but the specificity of these agents for blood vessel endothelium is debatable. Panendothelial markers show consistent labeling of both tumors, but marker studies employing a wide range of monoclonal antibodies specific for blood vessel endothelium have shown occasional positive labeling of tumor cells. A number of studies have claimed absence of labeling with specific blood vessel monoclonal antibodies, but at present no study employing a specific marker for lymphatic endothelium has been reported. Although the demonstration of specific markers for blood vessel endothelium in these tumors has been variable, the data would be compatible with lesions arising from undifferentiated stem cells that proliferate with varying degrees of differentiation toward blood vessel endothelium. An alternative hypothesis for the histogenesis of Kaposi's sarcoma would be one of multicentric hyperplasia containing lymphatic venular anastamoses with elements of both lymphatic and blood vessel endothelium.

Ultrastructural findings in clinically uninvolved oral mucosa of patients with HIV infection

Twelve biopsies of clinically normal oral mucosa taken from HIV seropositive patients have been investigated by means of light- and electron microscopy. Vascular abnormalities were found in all biopsies, regardless of the clinical stage of the HIV infection. In particular slit-like vascular channels, sparseness of intercellular junctions and swollen, protruded endothelial cells with an increased quantity of Weibel-Palade bodies were noticed. These findings were similar to those described in lesions of early stage Kaposi's sarcoma.