MHC-restricted phosphopeptides from insulin receptor substrate-2 and CDC25b offer broad-based immunotherapeutic agents for cancer

Cancer cells display novel phosphopeptides in association with MHC class I and II molecules. In this study, we evaluated two HLA-A2-restricted phosphopeptides derived from the insulin receptor substrate (IRS)-2 and the cell-cycle regulator CDC25b. These proteins are both broadly expressed in multiple malignancies and linked to cancer cell survival. Two phosphopeptides, termed pIRS-2_1097-1105 and pCDC25b_38-46, served as targets of strong and specific CD8 T-cell memory responses in normal human donors. We cloned T-cell receptor (TCR) cDNAs from murine CD8 T-cell lines speci fic for either pIRS-2_1097-1105 or pCDC25b_38-46. Expression of these TCRs in human CD8 T cells imparted high-avidity phosphopeptide-speci fic recognition and cytotoxic and cytokinesecreting effector activities. Using these cells, we found that endogenously processed pIRS-2_1097-1105 was presented on HLA-A2⁺ melanomas and breast, ovarian, and colorectal carcinomas. Presentation was correlated with the level of the Ser1100-phosphorylated IRS-2 protein in metastatic melanoma tissues. The highest expression of this protein was evident on dividing malignant cells. Presentation of endogenously processed pCDC25b_38-46 was narrower, but still evident on HLA-A2⁺ melanoma, breast carcinoma, and lymphoblastoid cells. Notably, pIRS-2_1097-1105-specific and pCDC25b_38-46-specific TCR-expressing human CD8 T cells markedly slowed tumor outgrowth in vivo. Our results de fine two new antigens that may be developed as immunotherapeutic agents for a broad range of HLA-A2⁺ cancers.