The Detection of Immunity against WT1 and SMAD4(P130L) of EpCAM(+) Cancer Cells in Malignant Pleural Effusion

Malignant pleural effusion (MPE) provides a liquid tumor microenvironment model that includes cancer cells and immune cells. However, the characteristics of tumor antigen-specific CD8(+) T cells have not been investigated in detail. Here, we analyzed MPE samples taken from a patient with pancreatic cancer who received a dendritic cell vaccine targeting Wilms’ Tumor 1 (WT1) antigen over the disease course (two points at MPE(1st) and 2(nd), two months after MPE1(st)). Epithelial cell adhesion molecule (EpCAM)(+) cancer cells (PD-L1(−) or T cell immunoglobulin mucin-3, TIM-3(−)), both PD-1 or TIM-3 positive CD8(+) T cells, and CD14(+)CD68(+)CD163(+)TIM-3(+) macrophages increased from the MPE(1st) to MPE(2nd). The ratio of WT1-specific cytotoxic lymphocytes (WT1-CTLs) to MPE CD8(+) T cells and IFN-γ secretion of WT1-CTLs were reduced with disease progression. Coincidentally, the fraction of central memory T (T(CM)) of WT1-CTLs was decreased. On the other hand, CD8(+) T cells in response to SMAD4(P130L), which is homogeneously expressed in EpCAM(+) cancer cells, were detected using in vitro expansion with the HLA-A*11:01 restrictive SVCVNLYH neoantigen. Furthermore, the CD8(+) T cell response to SMAD4(P130L) was diminished following remarkably decreased numbers of CD8(+) T(CM) in MPE samples. In conclusion, CD8(+) T cells responding to WT1 or SMAD4(P130L) neoantigen expressed in EpCAM(+) pancreatic cancer cells were detected in MPE. A tumor antigen-specific immune response would provide novel insight into the MPE microenvironment.