Figure 3. Outgrowth of antigen-loss variants after pmel T cell treatment of cancer cells expressing hgp100₂₅ but not of cancers expressing mgp100₂₅ or EGP.

Cancer cells of relapsed tumors expressing mgp100₂₅, EGP (both gray) or hgp100₂₅ (black) were isolated after pmel T cell treatment, adapted to culture, and analyzed for peptide-EGFP fusion gene expression (left panels). MC57 cells (white histogram) cultured in vitro and MC57-mgp100, MC57-EGP (both gray) or MC57-hgp100 (black) cells isolated from non-treated mice (right panels) were analyzed as controls. Isolated lines from mgp100- or hgp100-expressing tumors are representative for four lines each, the isolate from the EGP-expressing tumor is representative for two lines; all lines were isolated after relapse (respective tumors were marked with * in Figure 2B). The repeatability in independent experiments strongly suggests that loss of antigen expression from the hgp100₂₅ cancer cells was not an artifact caused by adaptation or post-isolation culturing. See also Figure S3.