Fig. 4

Maturation and final form of the columns. A Frozen section of a subcutaneous C38 tumor labeled for laminin (red), CD31 (green) and cell nuclei (TOTO-3, blue). The maturation process of the columns can be observed as we move from the peritumoral host tissue (right side of the picture) towards the center of the tumor (left side): the size of the columns and the amount of the deposited laminin increase from the periphery towards the tumor center. The newly incorporated connective tissue columns contain more vessels (arrows). After “processing” by tumor cells, they contain only a single vessel (arrowheads). B Tissue column in an orthotopically growing C38 tumor (black areas). The centrally located vessel (CD31, green) is surrounded by SMA-positive myofibroblasts (red) and enclosed by laminin (blue). C The frozen section of a C38 liver metastasis labeled with CD31 (green), SMA (red) and laminin (blue). Black areas represent tumor tissue. As maturation of the tissue columns progresses, the central part of the large column containing multiple vessels is invaded by the tumor (T). The tumor mass present within the column is not delineated by laminin, which indicates an early phase of invasion. At the lower right, a mature column is visible (arrow) containing a single vessel located centrally. Note the presence of a “misprocessed” column (arrowhead) that contains no vessels. D Connective tissue column in a subcutaneous C38 tumor (tumor cells fill the outer black area). The completely matured column contains a single central vessel (CD31, green) surrounded by connective tissue, which contains collagen I (red) and laminin deposited by the tumor cells (blue). E C38 lung metastasis. The black area represents tumor tissue. The column shows the same structure as in other locations. A central vessel can be seen (CD31, green), surrounded by SMA-positive cells (red) and laminin (blue). F C38 metastasis (black areas) reaching the brain surface. A connective tissue column that contains numerous vessels (CD31, green) surrounded by SMA-positive cells (blue) and laminin (red) produced by the tumor can be observed at this location