CD80 and neoplasm: Flow cytometry phenotypic analysis of cells explanted from the tumors and cultured for seven days ex vivo, taking advantage of the TC-1 and TRAMP-C2 mutual discrimination using the CD80 cell surface marker (TC-1 cells are CD80-positive while TRAMP-C2 are CD80-negative), revealed that the vast majority of tumor cells present in the tumors that had arisen from co-injection of TC-1 proliferating cells with senescent TRAMP-C2 cells were TC-1 tumor cells (Figure 5).