Multiple roles of circulating tumor cells and exosomes in cancer metastasis

Metastatic cancer is a prominent cause of death worldwide. Clinical evidences indicate that cancer patients affected by metastases display tumors diffused over the entire body that, once established, become very difficult to be eradicated and most of the times give a negative outcome. Both circulating tumor cells (CTCs) and exosomes can be detected in affected individuals' bodily fluids and participate to the metastatic cascade. Importantly, they are considered valuable predictors of therapeutic responses. In the last years, these biomaterials have been widely characterized, demonstrating their involvement in multiple steps of metastasis, and many strategies have been developed in order to isolate them. CTCs and exosomes have become fundamental tools for investigating and dissecting the cellular and molecular mechanisms responsible for the metastatic process, a quest everyday more critical for prevention and treatment of metastatic cancer.