TUMOR-GROWTH IN A DEFINED MICROCIRCULATION

The fate of human tumor cells deposited in rat uteri was investigated by light microscopy of histological sections, immunohistochemistry, an d scanning electron microscopy of microvascular corrosion casts. The h uman colonic tumor cell line LS 174 T was used as graft since it can b e detected by CEA immunohistochemistry, and spayed nude rats (PVG rnu/ rnu) were used as hosts, subjected to different hormonal regimens (no exogenous hormones, medroxyprogesterone acetate, 17-beta-estradiol, or the last two regimens in combination). Intrauterine deposition of a s uspension of 2x10(6) tumor cells resulted in tumor take in 72% (21/29) of the nude rats. Endometrial growth was verified in only three anima ls (14%, 3/21). Extraendometrial growth, however, was found in all ani mals with tumor take. These observations suggest that the endometrium is comparatively resistant to growth of xenografted human colonic tumo r cells. The tumor microcirculation consisted of new vessels, giving m orphological evidence that tumor growth is dependent on angiogenesis a nd not on invasion of preexisting vessels.