Issues

Uptake of Shiga toxin B (STxB) in primary cultures of colorectal tumors. Cells were incubated with STxB for 24 hours, fixed, and processed for immunofluorescence; STxB is shown in red and nuclear staining in blue. (A) An adenoma shows minor STxB uptake in contrast to (B) primary colorectal adenocarcinoma, (C) and liver metastasis. (D) negative control without STxB. (E) Double staining identifies the STxB-positive cells as tumor cells of epithelial origin. STxB (red) and cytokeratin-20 staining (green). (F) Note that STxB is enriched in cells at the periphery of the tumor cell islet, F-actin cytoskeleton stained in green. (G) Higher magnification shows perinuclear STxB accumulation in a tumor cell marked by cytokeratin-20 (green). (H) Fibroblasts in the primary cultures were identified by vimentin staining (green, arrowheads). The vimentin-positive cells show no uptake of STxB (red), as opposed to adjacent tumor cells (arrow). Size bars: 20 μm (A-D), 200 μm (E, F, H), 5 μm (G). For details, see Falguièes et al., in this issue.