Intratumoral tertiary lymphoid organ is a favourable prognosticator in patients with pancreatic cancer.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Immune cell infiltration as an indicator of the immune microenvironment of pancreatic cancer.

BACKGROUND: The host immune reaction is represented by immune/inflammatory cell infiltrates. Here we systematically analysed tumour-infiltrating immune/inflammatory cells in pancreatic ductal carcinoma (PDC) and evaluated their clinicopathological impact. METHODS: Using immunohistochemistry, we examined tumour-infiltrating CD68(+) pan-macrophages, HLA-DR(+)CD68(+) M1 macrophages (M1), CD163(+) or CD204(+) M2 macrophages (M2), CD66b(+) neutrophils (Neu), CD4(+) T cells (CD4(+)T), CD8(+) T cells (CD8(+)T), and FOXP3(+)CD4(+) regulatory T cells (Treg) in 212 cases of PDC, and conducted correlation and survival analyses using the Kaplan-Meier method and Cox proportional hazards model. RESULTS: Higher levels of tumour-infiltrating pan-macrophages, M2, Neu, or the ratio of Tregs to CD4(+)T (%Treg) were significantly associated with shorter survival, whereas higher levels of tumour-infiltrating CD4(+)T, CD8(+)T, or the ratio of M1 to pan-macrophages (%M1) were significantly associated with longer survival. Survival analysis of pairs of these variables revealed that some of the resulting patient groups had exclusively longer survival. We then connected the apparently related factors, and two significant variables emerged: tumour-infiltrating CD4(+)T(high)/CD8(+)T(high)/%Treg(low) and tumour-infiltrating %M1(high)/M2(low). Multivariate survival analysis revealed that these variables were significantly correlated with longer survival and had a higher hazard ratio. CONCLUSION: Tumour-infiltrating CD4(+)T(high)/CD8(+)T(high)/%Treg(low) and %M1(high)/M2(low) are independent prognosticators useful for evaluating the immune microenvironment of PDC.