MHC-Restricted Phosphopeptides from Insulin Receptor Substrate-2 and CDC25b Offer Broad-Based Immunotherapeutic Agents for Cancer

AbstractCancer 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-21097–1105 and pCDC25b38–46, 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 specific for either pIRS-21097–1105 or pCDC25b38–46. Expression of these TCRs in human CD8 T cells imparted high-avidity phosphopeptide-specific recognition and cytotoxic and cytokine-secreting effector activities. Using these cells, we found that endogenously processed pIRS-21097–1105 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 pCDC25b38–46 was narrower, but still evident on HLA-A2+ melanoma, breast carcinoma, and lymphoblastoid cells. Notably, pIRS-21097–1105–specific and pCDC25b38–46–specific TCR-expressing human CD8 T cells markedly slowed tumor outgrowth in vivo. Our results define two new antigens that may be developed as immunotherapeutic agents for a broad range of HLA-A2+ cancers. Cancer Res; 74(23); 6784–95. ©2014 AACR.