Prognostic value of innate and adaptive immunity in cancers

Cancer remains one of the most complex diseases affecting humans. Despite the impressive advances made in molecular and cell biology, the mechanism by which cancer cells progress through carcinogenesis and acquire their metastatic ability is still widely debated. Tumors are heterogeneous cellular entities whose growth depends on dynamical interactions among cancer cells, as well as between cells and the constantly changing microenvironment. Several types of immune cells, including cells of both the innate and adaptive immune system, comprise the human cancer microenvironment distributed both in tumor islets and in the stroma. While chronic inflammation is considered as one of the hallmarks of cancer, increasing the risk of tumor development and progression, the clinical relevance of innate and adaptive cellular components of the immune system is less clear. A relevant issue is to unravel the discrepancy between the promoting effects on cancer proliferation, invasion, and dissemination induced by some types of inflammatory cells and the inhibitory effects on cancer growth exerted by the local immune response. Here, we discuss the role played by innate and adaptive immune systems in the local progression and metastasis of human cancers of various histologic origins, as well as the prognostic information currently understood and exploited.