Medicine & Pharmacology, Gastroenterology; pancreatic cancer; immune surveillance; galectins; immunotherapy; immune checkpoints; stroma
Pancreatic ductal adenocarcinoma (PDA), the most frequent type of pancreatic cancer, is one of the main unfinished businesses in the biomedical and clinical fields, with still discouraging 5 year survival rates and poor therapy efficiency. PDA abundant desmoplasia has for long played the lead in the mechanisms involved in poor drug performance, being the main source of cytokines and chemokines orchestrating rapid and silent tumor progression and guilty of isolating tumor cells into a extense fibrotic reaction resulting in inefficient drug delivery. However, since immunotherapy was proclaimed the breakthrough of the year back to 2013, the focus in the stroma of pancreatic cancer has interestingly moved from activated fibroblasts to the immune compartment, trying to understand the immunosuppressive factors that play part in the strong immune evasion that characterizes PDA. PDA microenvironment is highly immune-suppressive, being basically composed of T regulatory cells (Tregs), tumor-associated macrophages (TAMs) and myeloid-derived suppressive cells (MDSCs), which boycott CD8+ T-cell duties in tumor recognition and clearance. Interestingly, preclinical data have highlighted the importance of this immune evasion as the source of resistance to single checkpoint immunotherapies and cancer vaccines and point at pathways inhibiting the immune attack as the key to solve the therapy puzzle. Here, we will discuss the molecular mechanisms involved in PDA immune escape as well as the state of the art of the PDA immunotherapy.