The role of hyaluronan in tumour neovascularization (review)

Induction of vascularisation by an aqueous extract of the flowers of Calendula officinalis L. the European marigold

Calendula officinalis L. (calendula) is a plant whose recorded history is indicative of intrinsic wound healing capabilities. The wound healing process involves several distinct phases in which the formation of new blood vessels plays an essential role. This report describes the angiogenic activity of a freeze-dried aqueous extract of the flowers of Calendula officinalis L. (the European marigold) utilizing the chick chorioallantoic membrane (CAM) assay. The CAM assay is a standard and well established method for assessing the angiogenic activity in impure and pure preparations and is suitable for studies requiring examination of large numbers of sample test materials. The angiogenic activity of calendula was measured by examination of CAMs using stereomicroscopy. Further histological investigation and quantification of neovascularization was performed utilizing microvascular counts. The histological sections of CAMs were also examined for the presence of hyaluronan (HA), a tissue glycosaminoglycan associated with neovascularization, by hyaluronidase digestion and staining of tissue sections by alcian blue. All calendula treated CAMs were positive for HA; no HA could be demonstrated in control CAMs. The numbers of microvessels in calendula-treated CAMs were statistically significantly higher than in the control CAMs (p < 0.0001). Thin layer chromatography indicated that the calendula extract contained water-soluble compounds such as flavonoids, but the exact nature of the active angiogenic component(s) has not yet been identified.

CD44 exon variant 6 epitope and hyaluronate synthase are expressed on HT29 human colorectal carcinoma cells in a SCID mouse model of metastasis formation

The factors which lead to the formation of metastases are generally poorly understood; however the expression of a particular variant of the cell adhesion molecule CD44 may be important in facilitating metastasis formation in colon cancer. The aim of the present study was to investigate the expression of CD44 exon v 6 (CD44v6), hyaluronate (one of its ligands), and hyaluronate synthase, in a clinically relevant animal model of metastatic colon carcinoma. HT29 human colon carcinoma cells were injected subcutaneously between the scapulae of severe combined immunodeficient (SCID) mice and left for 3 weeks (by which time the tumours had produced metastases in the lungs). Morphological observations at the tumour-host interface were consistent with the dissociation of neoplastic cells from the primary tumours, and the ability of these cells to migrate through the extracellular matrix facilitating metastasis formation. Immunohistochemically detectable hyaluronate synthase expression was increased in vivo compared with the parent cell line in vitro. CD44v6 expression and hyaluronate were increased around single cells at the periphery of tumours compared with the central regions. CD44v6 and hyaluronate snythase expression were co-expressed in the same cells. Indeed, the present study is the first to demonstrate hyaluronate synthase expression by an epithelial cell type.