Fig 2: ALT-FISH analysis and tumor marker co-staining of neuroblastoma (NB) tumor tissue. ALT status assignment is according to the CC analysis (Supplementary Figure S6C). See Supplementary Figure S6 and Supplementary Data Set 1 for additional information and spot statistics of all NB tumors. All scale bars are 200 µm. (A) ALT activity map of an ALT-positive NB tumor tissue section stained by TelC ALT-FISH and immuno-staining against the neuroblastoma-specific tumor cell marker NCAM (magenta). (B) Distinct regions of low to no ALT activity (I, II) were overlaid with the regions that lacked NCAM signal, identifying them as non-tumor/normal tissue. Nuclei classified as ALT-negative (blue) were also present in NCAM-positive tissue regions, indicating heterogeneity within the tumor cell population. (C) ALT activity maps of four ALT-negative and three ALT-positive NB sections. Two adjacent regions (~1 mm2 each) from the same section of ALT-positive tumor N2 are depicted. The fraction of nuclei falling into each ALT activity group is visualized by stacked bar graphs next to the images. Tumor N3.2 corresponds to an additional section of the tumor N3 sample analyzed in panel A (N3.1). Note that tumor N5 classified as ALT-negative in the CC assay displays a comparably high proportion of low-ALT cells based on the ALT map analysis.