As a result of in vivo exposure of tumors expressing immunogenic antigens to IFN-γ producing CTLs, we observed copy-number alterations (CNA) associated with DNA damage response and modulation of DNA editing/repair gene expression, which was not only attributable to the tumor-antigen loss but also accumulated during immunological selection thereby contributing to intra-tumor heterogeneity [74]. The gene discussed is IFNG; the disease is neoplasm.