Tumor‐induced angiogenesis studied in confrontation cultures of multicellular tumor spheroids and embryoid bodies grown from pluripotent embryonic stem cells

Abstract

ABSTRACT Tumor vascularization is the rate‐limiting step for the progression of cancer. Differential steps of tumor‐induced angiogenesis were studied by a novel in vitro confrontation culture of avascular multi‐cellular prostate tumor spheroids and embryoid bodies grown from pluripotent embryonic stem (ES) cells. Vascularization in embryoid bodies started on day 5 of cell culture and was paralleled by down‐regulation of hypoxia‐inducible factor 1α (HIF‐1α) and vascular endothelial growth factor (VEGF). In parallel, a dissipation of gradients in the pericellular oxygen pressure was observed as measured by O 2 ‐sensitive microelectrodes. After 24–48 h of confrontation culture, cells positive for platelet endothelial cell adhesion molecule (PECAM‐1) became visible in the contact region between the embryoid body and the tumor spheroid and sprouted within the confrontation cultures during subsequent days. Tumor‐induced angiogenesis resulted in growth stimulation of tumor spheroids, disappearance of central necrosis and a reduction of the pericellular oxygen pressure. Furthermore, tumor vascularization resulted in elevated levels of HIF‐1α, VEGF, heat shock protein 27 (HSP27), and P‐glycoprotein. Tumor‐induced angiogenesis may augment the oxygen consumption in tumors resulting in an increased expression of hypoxia‐related, proangiogenic genes as well as of HSP27 and P‐glycoprotein, which are involved in a multidrug resistance phenotype.—Wartenberg, M., Dönmez, F., Ling, F. C., Acker, H., Hescheler, J., Sauer, H. Tumor‐induced angiogenesis studied in confrontation cultures of multicellular tumor spheroids and embryoid bodies grown from pluripotent embryonic stem cells. FASEB J. 15, 995–1005 (2001)