The Vasculature of Xenotransplanted Human Melanomas and Sarcomas on Nude Mice

Abstract

The tumor-inherent vasculature plays a major role with respect to tumor sensitivity to ionizing radiation. Ultrastructural studies of the tumor vasculature are necessary in order to obtain more detailed information on the architecture and structure and on the sites affected by tumor therapy. The vasculature of xenotransplanted human tumors on nude mice was investigated in this study by means of scanning and transmission electron microscopy. Structurally complete real arteries or veins are neither to be seen in the periphery nor in the center. Large-caliber vessels basically have a capillary wall structure. The endothelial cells show a very alternating height and electron density. Frequently, different cell types and tumor cells themselves are apparently involved in the formation of the vessel wall. The endothelium is characterized by very simple immature cell contacts. In some tumors the amount of vessels without or with incomplete endothelium seems to be higher than the number of structurally real capillaries. This has consequences as well for radiotherapy as for hyperthermia and chemotherapy.

Transformation of the microvascular system during multistage tumorigenesis

“…Areas of high vessel density observed within RIP1‐Tag5 tumors may represent foci of active angiogenesis. The appearance of vascular sinusoids and lacunes in solid tumors has also been described for melanomas and was correlated with areas of maximal interstitial pressure 34. The aberrant vascular features that we describe for the spontaneously arising solid tumors in RIP1‐Tag5 mice are similar to intravital microscopy studies performed on experimental pancreatic cancer in the rat 35.…”

Vasculogenic mimicry

“…Timar & Toth (54) described sinusoids in melanomas lined by tumor cells and cited literature supporting the existence of such channels in breast cancer. In 1989, Konerding et al (55, 56) reported morphological descriptions of non‐endothelial cell‐lined “vessels” in animal models of melanoma and observed that thin branches of tumor cells morphologically resembled endothelial cells. Konnerding et al (56) therefore speculated that tumor cells may form vessels, although expressing uncertainty about the extent to which these channels provided perfusion to the tumor.…”

Molecular biology of breast cancer metastasis Molecular expression of vascular markers by aggressive breast cancer cells

“…There is strong evidence suggesting that human cytotrophoblasts adopt an endothelial cell phenotype as they actively participate in the dynamics of establishing the placenta and primordial microcirculation, which has been designated 'trophoblast pseudo-vasculogenesis' [9,10,11]. With respect to tumor vascularization, the possibility of the formation or lining of a microcirculation by tumor cells has been suggested by several studies, on the basis of morphologic analyses and numerous pathology reports [12,13,14,15,16,17,18,19,20,21,22,23,24,25]. In a recent review by Tímár and Tóth [26], the diagnostic and clinical significance with regard to human melanoma and breast cancer tumor cell-lined sinuses and vascular channels was presented.…”