Advanced Intestinal Cancers often Maintain a Multi-Ancestral Architecture
Fig 1
Mosaics are a powerful experimental tool for studying tumorigenesis.
The clonal architecture of colon tumors is visible in vivo using fluorescence endoscopy. The intestinal epithelium is a single layer of cells that is replaced every three to five days. New cells are produced from stem cells lying near the base of the each crypt. In our model, crypts are homotypic red or homotypic green with the latter being particularly evident during fluorescence endoscopy, as each crypt appears as a discrete green circle (A). Tumors can be composed of only red crypts (left panel), a mixture of red and green crypts (middle panel), or only green crypts (right panel). The tumors are outlined in white. The high variability in clonal architecture is also evident in whole mounts (B). Tumors were homotypic red (left panel), heterotypic (middle three panels), or homotypic green (right panel). The mixture of red and green crypts varies among multi-ancestral tumors, with some being primarily composed of either red crypts or green crypts, whereas others are roughly an equal number of both types. Histology is necessary to determine architecture, as tumors can appear heterotypic with neoplastic crypts of one color intermingled with normal crypts of the other color. The clonal architecture of tumors is scored from histologic sections. Neoplastic cells were visualized following H&E staining (C) with high levels of CTNNB1 (β-catenin) expression in the cytoplasm and nucleus (D, brown stain). As shown in a nearby section from the same tumor stained by immunofluorescence, neoplastic cells within a single tumor often arose from both the red and green cell lineages (E-F). Panel B photos are shown at the same magnification; size bar = 1mm. Panels C and E are shown at the same magnification; size bar = 500μm. Panel D shows a 4x enlargement in an adjacent section of the outlined area in Panel C. Panel F shows a 4x enlargement of the area outlined in Panel E.