Tumor angiogenesis activity of human choriocarcinoma cells grown in vitro

The growth of five different kinds of human choriocarcinoma cell lines in vitro was quite alike. However, two distinct types of rapid and slow growth were observed in tumors grown in the hamster cheek pouch. The rapidly grown tumor tissues (BeWo, JEG-3, and NUC-1) involved significantly large numbers of blood vessels per microscopic field, as compared to slowly grown ones (SCH and HM). The vascular response was assayed using cell-free crude tumor angiogenesis factors (TAF) on chorioallantoic membrane (CAM) of the chick embryo. In all cell lines TAF activity correlated well with the extent of tumor growth in vivo. Gel filtration analysis showed that relatively high-molecular-weight (more than 10,000) factors could induce neovascularization in the both assays using CAM and rabbit cornea. These results suggest that a heterogeneity of TAF activity is present among human choriocarcinoma cell lines and tumor growth in xenograft depends on the secretion of TAF by the tumor cells themselves.