GPT and osteosarcoma: We confirmed that these results extended to ALT+ cancer cell lines in general by performing the CCA on the differential centrifugation fractions of 24 h-old culture medium from a diverse panel of 11 ALT+ cancer cell lines and nine matching ALT− cells, including osteosarcoma, soft tissue sarcoma, neuroblastoma, glioblastoma, and non-small cell lung cancer cell lines, and a mortal cell strain.