Figure 4.

Demonstration of the repellent effect of hypoxic tissue areas on CTL infiltration. Six examples (A–F) showing significantly stronger inhibitory effects of hypoxic tumor cells compared to normoxic tumor cells concerning the distribution of CTL. Each row corresponds to one tumor. Left panels: original immunofluorescence images (DAPI, blue; hypoxic cells, green; CTL, yellow), all scale bars: 200 µm. Left middle panels, corresponding Spatstat point pattern representation of the different groups of cells identified in the tumor sections (hypoxic tumor cells, green; normoxic tumor cells, dark red; CTL, yellow). Right middle panels, inhomogeneity-corrected Kcross functions testing the distribution of CTL vs. hypoxic (green) and normoxic (red) tumor cells. The areas shown represent the confidence bands generated by Loh’s bootstrap method. Right panels, plot illustrating the delta between the lowest value of the red curve vs. the highest values of the green curves in the corresponding right middle panels. Values below 0 define a significant deviation. This is the region of statistically significant divergence between the distribution of both tumor cell populations relative to CTL. It is evident that hypoxic tumor cells have a stronger repellent or anti-clustering effect on CTL than normoxic tumor cells.