Fig. 7

Expression of β-catenin in BLM melanoma cells during brain metastasis in vivo. Untreated (n = 8) or 0.5 μM PKF115–584 pre-conditioned (n = 8) human BLM melanoma cell aggregates were injected into the IV^th ventricle (rhombencephalon) of the stage 12/13 HH chick embryo (m). After 96 h of further incubation the embryos were analyzed for tumor formation and melanoma cell invasion. a Untreated BLM cells had formed small tumor nodules in the roof plate of the rhombencephalon and infiltrated the neighboring host tissues in 7/8 chick embryos. b The HMB45-negative BLM cells the neural crest marker p75 (red cytoplasmic staining). c-e: BLM cells were almost 100% MIB1-positive (red nuclear staining) and were detected close to (d) or within (e, arrows pointing at BLM cells) blood vessels. f-i Immunohistochemistry for anti-β-catenin (f, red staining) showed that in the central tumor nodule as well as the metastatic nodule in the region of the floor plate the MIB1-positive BLM cells with a compact, epithelial-like morphology (asterisks in g and h) had only a weak cytoplasmic expression of β-catenin, while the cells in the outskirt of the tumor nodule and cells invading the host tissues in the mesenchyme along the neuroepithelium with a stretched, mesenchymal-like morphology (arrows in g and i) showed a prominent β-catenin expression. j-l In 8/8 embryos injected with PKF115–584 pre-conditioned BLM cells only an empty space as reminder of the former tumor nodule was detected after 96 h (j, k). Only few PKF115–584 pre-conditioned, MIB1-negative BLM cells and aggregates with morphological signs of apoptosis could be distinguished at this point in the lumen of the IVth ventricle floating among cellular debris of dead BLM cells (l). m Scheme of the injection of melanoma cells into the rhombencephalon of chick embryos. n Qualitative enumeration of chick embryos showing viable BLM melanoma cells in the roof plate with invading melanoma cells as shown in A-L. (asterisks define p-values calculated by Fisher’s exact test)