New insights into metronomic chemotherapy-induced immunoregulation

Chemotherapy is the mainstay of treatment in mid-advanced tumors. Considering their toxicity on hematopoietic cells, chemotherapeutics are often considered as immunosuppressive inducers. However, recently accumulating data indicate that some chemotherapeutic agents with specific administration schedules also display some positive immunological effect to contribute to tumor elimination. For instance, metronomic chemotherapy could promote tumor eradication not only by inhibiting tumor angiogenesis but also by selectively eliminating immunosuppressive cells and improving anti-tumor immune responses. In this review, we summarize what is currently known regarding metronomic chemotherapy-induced immunoregulation. Understanding of the molecular mechanisms of metronomic chemotherapy-induced immunoregulation may yield invaluable information for the optimal design of immunochemotherapies.