The lymphatic biology of Kaposi's sarcoma

Gene Expression Profiling Associated with the Progression of Classic Kaposi's Sarcoma

Although Kaposi's sarcoma (KS) gene expression profile is closer to lymphatic (LEC) rather than blood vascular endothelial cells (BEC), uncertainty still surrounds the cellular origin of KS. To follow KS progression from early to late (nodular) stage, and characterize the molecular fingerprinting associated with each stage, gene arrays were used to compare gene expression profile of 9 skin samples of classic KS (4 Early, 2 Mixed, and 3 Nodular CKS samples) to 4 normal samples. Results for selected genes were validated by Real-time (RT) PCR and immunohistochemistry. Genes regulating immune and defense responses, angiogenesis, apoptosis and proliferation were differentially expressed in different KS stages compared to normal skin. Hierarchical clustering separated normal skin from KS with a clear gradient from early to nodular KS lesions. The gene expression level of endothelium markers, metalloproteinases, angiogenic factors and chemokines, gradually increased from normal through all KS stages. The expression of LEC genes highly increased from early to nodular KS. In the initiation phase we noticed a higher expression of growth factors, as compared to progressive stages. LEC and BEC markers co-exist in “KS expression signature”, although the LEC signature prevailed. Our results also show a complex environment of inflammatory cells and chemokines during KS evolution. A pathogenic hypothesis where cellular hyperproliferation is driven by local expression of chemokines and growth factors without clonal expansion of cells is suggested.

Lymphatic differentiation in classic Kaposi's sarcoma: patterns of D2-40 immunoexpression in the course of tumor progression

The recent development of lymphatic endothelium-specific immuno-indicators has given rise to research on the histogenesis of Kaposi sarcoma (KS), specifically focusing on its lymphatic root and differentiation. D2-40 is a new lymphatic marker that recognizes podoplanin and is easily applied to formalin-fixed paraffin-embedded human tissues. This study examined D2-40 immunoexpression in 178 classical KS lesions using immunohistochemical methods. D2-40 immunoexpression was also examined in 63 non-KS soft tissue lesions to test the reliability of D2-40 monoclonal antibody in the pathological diagnosis of KS. D2-40 immunoreactivity was detected at all of the KS lesions and in lymphangioma and nonneoplastic lymphatic endothelium. There was no significant relationship between the extent of D2-40 staining and histopathological stage; however, there was a positive correlation between the staining intensity and histopathological stage in KS cases. D2-40 immunoreactivity was detected at all histopathological stages of KS and may be added to the routine immunohistochemical panel used for the differential diagnosis of KS. Widespread D2-40 protein expression is evidence of a lymphatic origin or the differentiation of neoplastic cells in KS, and D2-40 expression increases with tumor progression.

Primary Kaposi sarcoma of the subcutaneous tissue

Background

Involvement of the subcutis by Kaposi sarcoma (KS) occurs primarily when cutaneous KS lesions evolve into deep penetrating nodular tumors. Primary KS of the subcutaneous tissue is an exceptional manifestation of this low-grade vascular neoplasm.

Case presentation

We present a unique case of acquired immune deficiency syndrome (AIDS)-associated KS manifesting primarily in the subcutaneous tissue of the anterior thigh in a 43-year-old male, which occurred without overlying visible skin changes or concomitant KS disease elsewhere. Radiological imaging and tissue biopsy confirmed the diagnosis of KS.

Conclusion

This is the first documented case of primary subcutaneous KS occurring in the setting of AIDS. The differential diagnosis of an isolated subcutaneous lesion in an human immunodeficiency virus (HIV)-infected individual is broad, and requires both imaging and a histopathological diagnosis to guide appropriate therapy.

Histological variants of cutaneous Kaposi sarcoma

This review provides a comprehensive overview of the broad clinicopathologic spectrum of cutaneous Kaposi sarcoma (KS) lesions. Variants discussed include: usual KS lesions associated with disease progression (i.e. patch, plaque and nodular stage); morphologic subtypes alluded to in the older literature such as anaplastic and telangiectatic KS, as well as several lymphedematous variants; and numerous recently described variants including hyperkeratotic, keloidal, micronodular, pyogenic granuloma-like, ecchymotic, and intravascular KS. Involuting lesions as a result of treatment related regression are also presented.

Proliferating mesodermal cells in murine embryos exhibiting macrophage and lymphendothelial characteristics

BACKGROUND

The data on the embryonic origin of lymphatic endothelial cells (LECs) from either deep embryonic veins or mesenchymal (or circulating) lymphangioblasts presently available remain inconsistent. In various vertebrates, markers for LECs are first expressed in specific segments of embryonic veins arguing for a venous origin of lymph vessels. Very recently, studies on the mouse have strongly supported this view. However, in the chick, we have observed a dual origin of LECs from veins and from mesodermal lymphangioblasts. Additionally, in murine embryos we have detected mesenchymal cells that co-express LEC markers and the pan-leukocyte marker CD45. Here, we have characterized the mesoderm of murine embryos with LEC markers Prox1, Lyve-1 and LA102 in combination with macrophage markers CD11b and F4/80.

RESULTS

We observed cells co-expressing both types of markers (e.g. Prox1 - Lyve-1 - F4/80 triple-positive) located in the mesoderm, immediately adjacent to, and within lymph vessels. Our proliferation studies with Ki-67 antibodies showed high proliferative capacities of both the Lyve-1-positive LECs of lymph sacs/lymphatic sprouts and the Lyve-1-positive mesenchymal cells.

CONCLUSION

Our data argue for a dual origin of LECs in the mouse, although the primary source of embryonic LECs may reside in specific embryonic veins and mesenchymal lymphangioblasts integrated secondarily into lymph vessels. The impact of a dual source of LECs for ontogenetic, phylogenetic and pathological lymphangiogenesis is discussed.

Treatment of classic Kaposi's sarcoma-associated lymphedema with elastic stockings

Lymphedema of the lower extremities is a frequent complication of Kaposi's sarcoma (KS). Compressive therapy is the basis of treatment for lymphatic disorders, but to the authors' knowledge, there are no controlled trials to evaluate its effectiveness in KS-related lymphedema. Sixty-five patients with classic KS-associated lymphedema limited to below the knee were studied. Fifty patients received below-knee elastic stockings, whereas the remaining 15 did not use any compressive device. Among treated patients, 60% (30/50) experienced a limb volume reduction, while 40% (20/50) had an increase of limb volume. In contrast, all patients (15/15) of the untreated group had an increase of limb volume. No correlation between lymphedema reduction and systemic or local chemotherapy was observed, supporting compressive therapy as the major strategy for the treatment of this condition. Our results suggest that elastic stockings may be important tools for the management of lymphedema associated to classic KS.

Lymphatic Endothelial Cells, Lymphangiogenesis, and Extracellular Matrix

Exciting studies involving the molecular regulation of lymphangiogenesis in lymphatic-associated disorders (e.g., wound healing, lymphedema and tumor metastasis) have focused renewed attention on the intrinsic relationship between lymphatic endothelial cells (LECs) and extracellular matrix (ECM) microenvironment. ECM molecules and remodeling events play a key role in regulating lymphangiogenesis, and the "functionality"-relating molecules, especially hyaluronan, integrins, reelin, IL-7, and matrix metalloproteinases, provide the most fundamental and critical prerequisite for LEC growth, migration, tube formation, and survival, although lymphangiogenesis is directly or/and indirectly controlled by VEGF-C/-D/VEGFR- 3- Prox-1-, Syk/SLP76-, podoplanin/Ang-2/Nrp-2-, FOXC2-, and other signaling pathways in embryonic and pathological processes. New knowledge regarding the differentiation of initial lymphatics should enable improvements in understanding of a variety of cytokines, chemokines, and other factors. The lymphatic colocalization with histochemical staining by using the novel molecular markers (e.g., LYVE-1), along with subsequent injection technique with ferritin or some tracer, will reveal functional and structural features of newly formed and preexisting lymphatics. Growing recognition of the multiple functions of ECM and LEC molecules for important physiological and pathological events may be helpful in identifying the crucial changes in tissues subjected to lymph circulation and ultimately in the search for rational therapeutic approaches to prevent lymphatic-associated disorders.

Mesenchymal cells with leukocyte and lymphendothelial characteristics in murine embryos

The development of lymphatic endothelial cells (LECs) from deep embryonic veins or mesenchymal lymphangioblasts is controversially discussed. Studies employing quail-chick grafting experiments have shown that various mesodermal compartments of the embryo possess lymphangiogenic potential, whereas studies on murine embryos have been in favor of a venous origin of LECs. We have investigated NMRI mice from embryonic day (ED) 9.5 to 13.5 with antibodies against the leukocyte marker CD45, the pan-endothelial marker CD31, and the lymphendothelial markers Prox1 and Lyve-1. Early signs of the development of lymphatics are the Lyve-1- and Prox1-positive segments of the jugular and vitelline veins. Then, lymph sacs, which are found in the jugular region of ED 11.5 mice, express Prox1, Lyve-1, and CD31. Furthermore, scattered cells positive for all of the four markers are present in the mesenchyme of the dermatomes and the mediastinum before lymphatic vessels are present in these regions. Their number increases during development. A gradient of increasing CD31 expression can be seen the closer the cells are located to the lymph sacs. Our studies provide evidence for the existence of scattered mesenchymal cells, which up-regulate lymphendothelial and down-regulate leukocyte characteristics when they integrate into growing murine lymphatics. Such stem cells may also be present in the human and may be the cell of origin in post-transplantation Kaposi sarcoma.

Lymphatic and vascular origin of Kaposi's sarcoma spindle cells during tumor development

The histogenesis of Kaposi's sarcoma (KS) tumor spindle cells (SC) remains controversial but several immunohistochemical studies favor a lymphatic origin. Twenty KS surgical biopsies were analyzed for the coexpression of LANA, CD34, LYVE-1, D2-40, VEGFR-2, VEGFR3 by using double or triple immunostaining. Most of the SC in both early and late KS expressed the lymphatic markers LYVE-1, D2-40 and VEGFR-3 and the blood vascular endothelial/endothelial precursor cell markers CD34 and endothelial stem cell marker VEGFR-2. All the LANA+ SC in early and late KS were LYVE-1+, but only 75% of these LANA+ cells were CD34(+). The CD34(+)/LANA+ cells increased from early- (68.8%) to late-stage KS (82.2%). However, approximately 18% of the LANA+ SC in early KS were CD34(-) but were LYVE-1+, suggesting that resident lymphatic endothelial cells (LEC) are targeted for primary infection by human herpesvirus-8. This LANA+/LYVE-1+/CD34(-) (resident LEC) cell population clearly decreased during the development of KS from early (18.7%) to late KS (2.9%). Thus, in late stages of KS, most SC were LANA+/CD34(+)/LYVE-1+. However, in both early- and late-stage KS, approximately 18% of the SC were CD34(+)/LANA-/LYVE-1 -- and could represent newly recruited endothelial precursor cells, which become infected in the lesion and eventually undergo a phenotype switch expressing LEC markers. Our study apparently indicates that KS represents a unique variant of tumor growth with continues recruitment of tumor precursor cells as well as proliferation and decreased apoptosis of SC.