Telomerase-Specific T-Cell Immunity in Breast Cancer: Effect of Vaccination on Tumor Immunosurveillance Susan M. Domchek, 2,3 Adri Recio, 1 Rosemarie Mick, 2,4 Carolyn E. Clark, 1 Erica L. Carpenter, 1 Kevin R. Fox, 2,3 Angela DeMichele, 2,3 Lynn M. Schuchter, 2,3 Michael S. Leibowitz, 1 Michael H. Wexler, 1 Barbara A. Vance, 1,2 Gregory L. Beatty, 1,2,3 Elizabeth Veloso, 1 Michael D. Feldman, 2,5 and Robert H. Vonderheide 1,2,3 1 Abramson Family Cancer Research Institute, 2 Abramson Cancer Center, 3 Division of Hematology-Oncology, Departments of Medicine, 4 Biostatistics and Epidemiology, and 5 Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania Abstract The human telomerase reverse transcriptase (hTERT) is nearly universally overexpressed in human cancer, contributes cri- tically to oncogenesis, and is recognized by cytotoxic T cells that lyse tumors. CD8+ T cells specific for hTERT naturally occur in certain populations of cancer patients in remission, but it remains poorly understood whether such T cells could contribute to tumor immunosurveillance. To address this issue, we induced hTERT-specific T cells in vivo via peptide vaccination in 19 patients with metastatic breast cancer who otherwise had no measurable T-cell responses to hTERT at baseline. Tumor-infiltrating lymphocytes (TIL) were evident after, but not before vaccination, with 4% to 13% of post- vaccine CD8+ TIL specific for the immunizing hTERT peptide. Induction of TIL manifested clinically with tumor site pain and pruritus and pathologically with alterations in the tumor microenvironment, featuring histiocytic accumulation and widespread tumor necrosis. hTERT-specific CD8+ T cells were also evident after vaccination in the peripheral blood of patients and exhibited effector functions in vitro including proliferation, IFN-; production, and tumor lysis. An explor- atory landmark analysis revealed that median overall survival was significantly longer in those patients who achieved an immune response to hTERT peptide compared with patients who did not. Immune response to a control cytomegalovirus peptide in the vaccine did not correlate with survival. These results suggest that hTERT-specific T cells could contribute to the immunosurveillance of breast cancer and suggest novel opportunities for both therapeutic and prophylactic vaccine strategies for cancer. [Cancer Res 2007;67(21):10546–55] Introduction The re-emerging concept of tumor immunosurveillance builds on findings that T lymphocytes can recognize peptide antigens expressed on the surface of tumor cells in the context of MHC molecules (1, 2). Among the several dozen such antigens that have been previously described, most are neither broadly expressed in cancer nor critical to the oncogenic process, and the appearance of antigen-loss mutations in tumor cells in the face of immune pressure is well-described (3–5). We therefore sought to understand natural and induced immune responses to a class of antigens termed ‘‘universal tumor antigens’’ that not only trigger T cell reactivity against a broad range of tumor types but also play critical functional roles in tumor growth and development (6). We hypo- thesized that such molecules, if essential to the neoplastic pro- cess and presented by MHC molecules, might function as effective mediators of cellular immunosurveillance for which mutation as a means of immune escape would be incompatible with sustained tumor growth. A prototype antigen for this hypothesis is the human telomerase reverse transcriptase (hTERT; ref. 7). Telomerase maintains chromosomal integrity by protecting telomeric DNA that would otherwise be lost during successive rounds of cell division in rapidly dividing cells such as tumor cells (8–10). Although telo- merase activity and hTERT expression is absent in most normal human cells, telomerase activity is found in >85% of all human cancers (11), including most types of cancer stem cells described thus far (12). hTERT expression plays a critical functional role in oncogenesis (13), and inhibition of hTERT in cancers that express telomerase activity leads to growth arrest in vitro without the development of escape mutants (14, 15). Naturally occurring CD8+ T cells specific for the hTERT peptide I540 (ILAKFLHWL) have been observed in high numbers in blood from certain populations of cancer patients in remission following standard therapies (16, 17), but whether such T cells represent an active component of cancer immunosurveillance—and one that might be therapeutically exploited—remains unknown. We and others have previously observed that the I540 peptide binds with high affinity to HLA-A2 and can be used to generate specific CTLs in vitro that lyse a wide range of hTERT + tumor cell lines and primary tumors (18–21). In healthy individuals or patients with a heavy burden of metastatic cancer, the precursor frequency of I540-specific CD8+ T cells in peripheral blood is very low (20). In contrast, >80% of HLA-A2+ patients with chronic myelogenous leukemia in durable remission following treatment with imatinib, IFN-a, or stem cell transplantation harbor large numbers of circulating, tetramer-positive I540-specific CTL in peripheral blood, ranging from 0.1% to 13.2% of freshly isolated CD8+ T cells (16). In our own study of patients with acute myelogenous leukemia or chronic myelogenous leukemia in remission following allogeneic stem cell transplantation or imatinib, we also found that 80% of patients had I540 tetramer–reactive CD8+ T cells in the blood (range, 0.1–1.2%; data not shown). Similarly, >90% of HLA-A2+ patients with prostate cancer in remission following prostatectomy Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). Requests for reprints: Robert H. Vonderheide, Abramson Family Cancer Research Institute, University of Pennsylvania School of Medicine, 551 BRB II/III, 421 Curie Boulevard, Philadelphia, PA 19104. Phone: 215-573-4265; Fax: 215-573-2652; E-mail: rhv@mail.med.upenn.edu. I2007 American Association for Cancer Research. doi:10.1158/0008-5472.CAN-07-2765 Cancer Res 2007; 67: (21). November 1, 2007 10546 www.aacrjournals.org Research Article Research. on February 19, 2016. © 2007 American Association for Cancer cancerres.aacrjournals.org Downloaded from