Understanding Tumor-Stroma Interplays for Targeted Therapies by Armed Mesenchymal Stromal Progenitors: The Mesenkillers.

Tumor represents a complex structure containing malignant cells strictly coupled with a large variety of surroundingcells constituting the tumor stroma (TS). In recent years, the importance of TS for cancer initiation, development,local invasion and metastases became increasingly clear allowing the identification of TS as one of the possibleways to indirectly target tumors. Inside the heterogeneous stromal cell population, tumor associated fibroblasts(TAF) play a crucial role providing both functional and supportive environments. During both tumor and stroma development,several findings suggest that TAF could be recruited from different sources such as locally derived host fibroblasts,via epithelial/endothelial mesenchymal transitions or from circulating pools of fibroblasts deriving form mesenchymalprogenitors, namely mesenchymal stem/stromal cells (MSC). These insights prompted scientists to identifymultimodal approaches to target TS by biomolecules, monoclonal antibodies and, more recently, via cell basedstrategies. These latter appear extremely promising, although associated with still debated and unclear findings. Thisreview discusses on crosstalk between cancers and their stroma, dissecting specific tumor types, such as sarcoma,pancreatic and breast carcinoma where stroma plays distinct paradigmatic roles. The recognition of these distinctstromal functions may help in planning effective and safer approaches aimed either to eradicate or to substitute TSby novel compounds and/or MSC having specific killing activities