Mesenchymal Stem Cells, Cancer Stem Cells (CSCs), and Circulating Tumor Cells (CTCs): Roles and Combinations in Tumor Growth and Dissemination

Mesenchymal stem cells are considered the key cells in tissue regeneration after damage. MSCs play a fundamental role in cancer since they can be recruited to induce tumor growth and spread. In the last decades, MSCs have demonstrated several molecular characteristics in tissue regeneration and cancer development: the capacity to escape the immune system, induce tumor angiogenesis, and probably confer resistance to cancer from common chemotherapeutic agents. However, much remains to be clarified about their involvement in the epithelial-mesenchymal transition (EMT) and interaction with cancer stem cells (CSCs), primarily due to the complexity of these molecular processes. Besides these aspects, other new molecules, such as circulating tumor cells (CTCs), seem to strongly connect with CSCs and MSCs in managing pre-metastatic niche formation. In summary, MSCs may play a complex and combined key role with CSCs and CTCs. Our chapter would highlight the importance of considering all these molecular processes and cellular interactions reporting to MSCs as a setting for other new perspectives against cancer.