Chronic inflammation has a certain impact on the carcinogenesis of the digestive organs. The characteristic tissue structure of pancreatic cancer, desmoplasia, results from inflammatory processes induced by cancer cells and stromal cells. Concerning the progression of pancreatic cancer, recent research has clarified the pivotal role of tumor-stromal interaction, which promotes the development of an invasive phenotype of cancer and provides survival advantages against chemotherapeutic agents or immune surveillance. Tumor stromal cells such as pancreatic stellate cells and immune cells establish a microenvironment that protects cancer cells through complex interactions. The microenvironment of pancreatic cancer acts as a niche for pancreatic cancer stem cells from which therapy-resistance and disease recurrence develop. Inhibition of the stromal functions or restoration of the immune reaction against cancer cells has therapeutic benefits that enhance the efficacy of conventional therapies. Some of the recent advances in this field are now under evaluation in clinical settings, but many problems must be overcome to establish a radical therapy for pancreatic cancer. This review summarizes current knowledge about the tumor-promoting stromal functions, immune system modulation and therapeutic strategies targeting tumor-stromal interactions in pancreatic cancer.
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