Research Article Regression of Metastatic Merkel Cell Carcinoma Following Transfer of Polyomavirus-Specific T Cells and Therapies

Merkel cell carcinoma (MCC) is an aggressive skin cancer that typically requires the persistent expression of Merkel cell polyomavirus (MCPyV) oncoproteins that can serve as ideal immunotherapeutic targets. Several immune evasion mechanisms are active in MCC, including downregulation of HLA class-I expression on tumor cells and dysfunctional endogenous MCPyV-specific CD8 T-cell responses. To overcome these obstacles, we combined local and systemic immune therapies in a 67-year-old man, who developed metastatic MCPyV-expressing MCC. Intralesional IFN-b-1b or targeted single-dose radiation was administered as a preconditioning strategy to reverse the downregulation of HLA-I expression noted in his tumors and to facilitate the subsequent recognition of tumor cells by T cells. This was followed by the adoptive transfer of ex vivo expanded polyclonal, polyomavirus-specific T cells as a source of reactive antitumor immunity. The combined regimen was well tolerated and led to persistent upregulation of HLA-I expression in the tumor and a durable complete response in two of threemetastatic lesions. Relative to historical controls, the patient experienced a prolonged periodwithout development of additional distant metastases (535 days compared with historic median of 200 days; 95% confidence interval, 154–260 days). The transferred CD8þ T cells preferentially accumulated in the tumor tissue, remained detectable and functional for more than 200 days, persisted with an effector phenotype, and exhibited evidence of recent in vivo activation andproliferation. The combination of local and systemic immune stimulatory therapies was well tolerated and may be a promising approach to overcome immune evasion in virus-driven cancers. Cancer Immunol Res; 2(1); 1–10. 2013 AACR