Figure 4.

Heterogeneous spatial patterning of Wnt signaling activity (a) and the Wnt-inhibitor Dkk (b) in in vitro tumor spheroids. In (a), two single-cell-cloned colon cancer spheroids (scale bars are 20 μm) are shown using phase contrast (left), fluorescence microscopy (right). The green color (online; TOP-GFP) denotes Wnt signaling activity highlighted by white arrows. (a) is adapted from Fig. 1b in Vermeulen et al. (2010), with kind permission. In (b), tumor spheroids of MG63 osteosarcoma cells are shown using phase contrast (upper left), fluorescence (mitochondrially localized red fluorescent protein, upper right), a section of the spheroid (red; color online) immunostained for Dkk1 (green; color online), highlighted by a white arrow, and nuclei (blue; color online; DAPI), with scale bars 200μm (top) and 10μm (bottom). (b) is adapted from Figs. 3(c) and 3(d) in Lee et al. (2007), with kind permission.