Figure 4.

Comparison of 1-week-old tumor nodules from SCL-I and SCL-I^TSP-1 clone 9 cells. (A) Tumor histology of sections from SCL-I cells shows solid tumor nodules with tumor cell islands (t) embedded in stroma ropes (s). (B) SCL-I^TSP-1 cells had formed cyst-like nodules consisting of a rim of vital epithelium (t) around massive central necrosis (cn) and surrounded by stroma. (C) In situ hybridization with an antisense TSP-1 probe (bright-field micrograph) showing only scattered cells in SCL-I nodules expressing TSP-I mRNA. (D) In SCL-I^TSP-1 nodules, nearly all tumor cells expressed TSP-1. Immunostaining with a TSP-1-specific antibody revealed scattered TSP-1 protein dots throughout the SCL-I nodule (E) whereas SCL-I^TSP-1 nodules showed a prominent TSP-1 matrix at the tumor/stroma border (F). (G) The carcinoma-like SCL-I nodules consisted of epithelial islands (high density of Hoechst-stained nuclei) interspersed by stroma (areas of low nuclei content) with blood vessels (yellow) prominent in the stroma around the tumor as well as within the tumor. (H) In SCL-I^TSP-1 cysts, vessels double-stained for collagen type IV (in red) and PECAM (in green) (double-labeled vessels appear in yellow) were present in the surrounding stroma but absent in the tumor. s, stroma; t, tumor; cn, central necrosis. (Bar = 100 μm.)