IL-10 in cancer: Just a classical immunosuppressive factor or also an immunostimulating one?

It is generally well-accepted and established the IL-10-mediated protumor function in cancer, based on its immunosuppressive properties. However, new evidences from in vitro and in vivo murine models have emerged showing a potential immunostimulating activity of this cytokine, which may sustain IL-10-mediated antitumor function in cancer, hence favoring tumor regression. Here, we attempt to clarify IL-10’s role in cancer, by conducting a literature review of previously published studies, presenting information about IL-10 immunosuppressive and/or immunostimulating properties. Different and contradictory IL-10 effects leading to tumor growth (e.g., suppression of pro-inflammatory cytokines or inhibition of immune response recognition steps) or tumor regression (e.g., stimulation of cytotoxic and cytolytic activities of immune cells or inhibition of angiogenic factors) were found in distinct scenarios, hindering the establishment of a general role for IL-10 in cancer. Such definition is still a challenge, maybe due to a lack of sufficient information to support it, or perhaps based on the fact that IL-10 role in distinct cancer contexts may vary, switching from a classical immunosuppressive factor to an immunostimulating one