Analysis of peripheral and local anti‐tumor immune response in esophageal cancer patients after NY‐ESO‐1 protein vaccination

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Abstract
NY‐ESO‐1 antigen is a prototype of a class of cancer/testis antigens. We carried out a clinical trial using NY‐ESO‐1 whole protein as a cancer vaccine for 13 advanced cancer patients. We have recently reported that vaccine elicited humoral and cellular immune responses in 9 cancer patients including 4 esophageal cancer patients, and clinical responses were also observed in 4 of 5 evaluable patients. In this study, we analyzed the responses in 8 esophageal cancer patients including 4 newly enrolled patients. Patients were injected subcutaneously at biweekly intervals with NY‐ESO‐1 recombinant protein formulated with cholesterol‐bearing hydrophobized pullulan. Induction of antibody, and CD4 and CD8 T‐cell responses were observed in 7, 7 and 6 patients, respectively, out of 8 patients. 1 PR, 2 SD and 2 mixed clinical responses were observed in 6 evaluable patients. No significant adverse events were observed. Furthermore, we analyzed NY‐ESO‐1 and MHC class I expression and the infiltration of immune cells into tumor samples obtained before and after vaccination from 4 patients by immunohistochemistry. The results showed 2 patients with disappearance of CD4 and CD8 T‐cell infiltration, 1 patient with increase in the number of CD68+ macrophages and 1 patient with tumor antigen loss in the progressive tumors following vaccinations. The induction of NY‐ESO‐1 immunity and some preferable clinical outcomes were observed in esophageal cancer patients by vaccination with NY‐ESO‐1. However, the tumors grew eventually by various mechanisms after vaccination.

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