It is nowadays well established that the immune system can profoundly influence disease outcome in cancer patients. Increasing evidence is indeed showing that patients displaying spontaneous T cell-mediated immune response against their tumor (defined as immune surveillance) have higher chance to respond to therapies and display globally better prognosis. Conversely, patients whose tumor is characterized by immunosuppression, usually involving myeloid cells and chronic inflammation pathways, often undergo rapid progression and rarely benefit from therapy. Hence, capturing the immune features of individual tumors can help to predict disease course and tailor the therapeutic workup in clinical setting. In addition, overcoming cancer-related immunosuppression could provide a valid tool to rescue immune surveillance and implement cancer treatment through the engagement of the immunological control.

Delivering the right cure to the right patient is the base of precision medicine, and intensive efforts are ongoing worldwide to include the assessment of immune features unto individual patient profiling. However, despite the enormous amount of preclinical and clinical data proving the pivotal role of immunity in molding disease outcome, the immune-related assays that have been introduced into clinical practice, are still scantly. One major limitation is related to the fact that most immune biomarkers have been so far evaluated at tumor site, which implies the need for tumor biopsies and limitations related to intra-lesion heterogeneity. Instead, tests relying on blood samples are easier to perform, more reliable in terms of reproducibility, and repeatable for longitudinal studies. Of note, it is nowadays well established that cancer immunity is a systemic process involving different peripheral immune organs (lymph nodes, bone marrow and spleen) and, as such, it can be measured in blood. Hence, circulating immune cells might represent an informative source of biomarkers to reveal the type and activation status of immunity at single patient level. This holds particularly true for tumor-related immunosuppression, which is mostly mediated myeloid cells and it is responsible for blunting antitumor T cell immune-surveillance. Early during carcinogenesis, cancer cells establish a tight cross-talk with the bone marrow, mediated by tumor-released soluble factors that influence myelopoiesis. This process results in the introduction into the peripheral circulation, of aberrant immunosuppressive myeloid cells, globally known as Myeloid-Derived Suppressor Cells (MDSC). MDSC are among the most potent allies of the tumor cells, whose growth and progression in vivo in favored by MDSC ability to inhibit antitumor T cells, promote angiogenesis and sustain metastatic spread. High numbers of MDSC in blood and tumor site of cancer patients is reproducibly associated with poor prognosis and resistance to therapy, including immunotherapy. Studies in preclinical models have also shown that in vivo removal of MDSC reduces tumor expansion in vivo and confers sensitivity to treatment including immunotherapy, indicating a promising role of these cells as appealing novel therapeutic target in cancer. Unfortunately, the phenotypic and functional features of human MDSC are still poorly understood and need to be extensively investigated in clinical setting.

The members of the SERPENTINE Consortium have substantially contributed to the discovery and the study of MDSC in cancer, acquiring deep knowledge on the phenotypic and functional features of these cells both in human and murine setting. In the present trial? coordinators are committed to translate the predictive/prognostic role of MDSC immune profiling into real-life clinical practice. Through the concerted effort of all Consortium members and the prospective enrolment of blood samples from a comprehensive cancer patients case set, coordinators are going to develop off-the-shelf predictive/prognostic test based on the standardized quantification of MDSC in peripheral blood of cancer patients. In addition, thanks to our multiple expertise, coordinators are going to get deep insights into the biology of human cancer-related MDSC, for the development of novel therapeutic approaches based on rescuing tumor immune surveillance by antagonizing immunosuppression.