Another possible mechanism of resistance was reduction in major histocompatibility complex (MHC) class I levels, which allows tumors cells to avoid immune surveillance by CD8+ T cells.56 However, we found that the ex vivo tumor cells had higher levels of MHC class I on their surface compared with the parental tumor cell line, in both the absence and presence of IFNγ stimulation (Figure S2C). This evidence concerns the gene IFNG and neoplasm.