Figure 2.

(A) Definition of areas for quantitative distinction between tumor growth, space occupying tumor growth (tumor mass effect), and tumor cell invasion. Other parameters (tumor height, tumor depth, tumor invasion depth and recipient tissue area) are shown as well. (B) Definition of “tumor invasion index” and “space occupying growth index,” for exact quantitation. Additionally, indices related to tumor depth and tumor invasion depth are defined. (C) Tumor invasion index values of spheroid co-cultures and xenograft tandem-cultures, based on different cell lines. Asterisks indicate statistically significant (* = p < 0.05, ** = p < 0.01) differences of xenograft tandem-cultures vs. their spheroid co-culture counterparts.