VSIR and pancreatic ductal adenocarcinoma: VISTA acts as an inhibitory immune checkpoint by suppressing T cells and enabling cancer’s immune escape in melanoma [9], pancreatic ductal adenocarcinoma [10], prostate cancer [11], renal cell carcinoma [12], non-small cell lung cancer [6], acute myeloid leukemia [13], colorectal cancer [4], ovarian cancer, endometrial cancer [14], fibrosarcoma [15], glioma [16], and oral squamous cell carcinoma [17].