Background: Methods: Results: Conclusion:

Host immunity has critical roles in tumour surveillance. Tertiary lymphoid organs (TLOs) are induced in various inflamed tissues. The aim of this study was to investigate the clinicopathological and pathobiological characteristics of tumour microenvironment in pancreatic ductal carcinoma (PDC) with TLOs. We examined 534 PDCs to investigate the clinicopathological impact of TLOs and their association with tumour-infiltrating immune cells, the cytokine milieu, and tissue characteristics. There were two different localisations of PDC-associated TLOs, intratumoral and peritumoral. A better outcome was observed in patients with intratumoral TLOs, and this was independent of other survival factors. The PDC tissues with intratumoral TLOs showed significantly higher infiltration of T and B cells and lower infiltration of immunosuppressive cells, as well as significantly higher expression of Th1- and Th17-related genes. Tertiary lymphoid organs developed with an association with arterioles, venules, and nerves. These structures were reduced in an association with cancer invasion in PDC tissues, except for those with intratumoral TLOs. The PDC tissues with intratumoral TLOs had capillaries consisting of mature endothelial cells covered by pericytes. Our results suggest that the presence of intratumoral TLOs represents a microenvironment that has an active immune reaction, and shows a relatively intact vascular network retained.

Next generation sequencing (NGS) of tumor tissue (i.e., clinical sequencing) can guide clinical management by providing information about actionable gene aberrations that have diagnostic and therapeutic significance. Here, we performed a hospital‐based prospective study (TOP‐GEAR project, 2^nd stage) to investigate the feasibility and utility of NGS‐based analysis of 114 cancer‐associated genes (the NCC Oncopanel test). We examined 230 cases (comprising > 30 tumor types) of advanced solid tumors, all of which were matched with non‐tumor samples. Gene profiling data were obtained for 187 cases (81.3%), 111 (59.4%) of which harbored actionable gene aberrations according to the Clinical Practice Guidelines for Next Generation Sequencing in Cancer Diagnosis and Treatment (Edition 1.0) issued by three major Japanese cancer‐related societies. Twenty‐five (13.3%) cases have since received molecular‐targeted therapy according to their gene aberrations. These results demonstrate the utility of tumor‐profiling multiplex gene panel testing in a clinical setting in Japan. This study is registered with UMIN Clinical Trials Registry (UMIN000011141).

An adequate level of arginine in the tissue microenvironment is essential for T cell activity and survival. Arginine levels are regulated by the arginine-catabolizing enzyme, arginase (ARG). It has been reported that arginase II (ARG2), one of two ARGs, is aberrantly expressed in prostate cancer cells, which convert arginine into ornithine, resulting in a lack of arginine that weakens tumor-infiltrating lymphocytes and renders them dysfunctional. However, immune suppression mediated by ARG2-expressing cancer cells in lung cancer has not been observed. Here we studied the expression of ARG2 in pancreatic ductal carcinoma (PDC) tissue clinicopathologically by examining over 200 cases of PDC. In contrast to prostate cancer, ARG2 expression was rarely demonstrated in PDC cells by immunohistochemistry, and instead ARG2 was characteristically expressed in α-smooth muscle actin-positive cancer-associated fibroblasts (CAFs), especially those located within and around necrotic areas in PDC. The presence of ARG2-expressing CAFs was closely correlated with shorter overall survival (OS; P = 0.003) and disease-free survival (DFS; P = 0.0006). Multivariate Cox regression analysis showed that the presence of ARG2-expressing CAFs in PDC tissue was an independent predictor of poorer OS (hazard ratio [HR] = 1.582, P = 0.007) and DFS (HR = 1.715, P = 0.001) in PDC patients. In addition to the characteristic distribution of ARG2-expressing CAFs, such CAFs co-expressed carbonic anhydrase IX, SLC2A1, or HIF-1α, markers of hypoxia, in PDC tissue. Furthermore, in vitro experiments revealed that cultured fibroblasts extracted from PDC tissue expressed the ARG2 transcript after exposure to hypoxia, which had arginase activity. These results indicate that cancer cell-mediated immune suppression through ARG2 expression is not a general event and that the presence of ARG2-expressing CAFs is an indicator of poor prognosis, as well as hypoxia, in PDC tissue.

Intraductal papillary mucinous neoplasms (IPMNs) and mucinous cystic neoplasms (MCNs) are non-invasive neoplasms that are often observed in association with invasive pancreatic cancers, but their origins and evolutionary relationships are poorly understood. In this study, we analyze 148 samples from IPMNs, MCNs, and small associated invasive carcinomas from 18 patients using whole exome or targeted sequencing. Using evolutionary analyses, we establish that both IPMNs and MCNs are direct precursors to pancreatic cancer. Mutations in SMAD4 and TGFBR2 are frequently restricted to invasive carcinoma, while RNF43 alterations are largely in non-invasive lesions. Genomic analyses suggest an average window of over three years between the development of high-grade dysplasia and pancreatic cancer. Taken together, these data establish non-invasive IPMNs and MCNs as origins of invasive pancreatic cancer, identifying potential drivers of invasion, highlighting the complex clonal dynamics prior to malignant transformation, and providing opportunities for early detection and intervention.