Dormant tumor cells as a therapeutic target?

Tumor dormancy is characterised by the persistence of residual tumor cells for long periods. Recurrence from minimal residual disease is a major cause of cancer death. Thus, understanding how cancer cells become and remain dormant, may lead to new strategies to prevent relapse. Evidence has emerged that a balance exists between host and dormant tumor cells. Cross-talk between tumor cells and their micro-environment, angiogenesis, and anti-tumor immune response participate in the control of dormant tumor cells. Tumor cells have several mechanisms of maintaining equilibrium, and immune escape, including expression of immuno-regulatory molecules (e.g., increased expression of B7.1 and B7-H1); epigenetic modifications (e.g., silencing of the SOCS1 gene, de-regulating the JAK/STAT pathway); and autocrine loops. These new findings offer new opportunities to design specific treatments, to modify the balance in favor of the host immune response.