Metal Drugs and the Anticancer Immune Response

The immune system deploys a multitude of innate and adaptive mechanisms not only to ward off pathogens but also to prevent malignant transformation ("immune surveillance"). Hence, a clinically apparent tumor already reflects selection for those malignant cell clones capable of evading immune recognition ("immune evasion"). Metal drugs, besides their well-investigated cytotoxic anticancer effects, massively interact with the cancer-immune interface and can reverse important aspects of immune evasion. This topic has recently gained intense attention based on combination approaches with anticancer immunotherapy (e.g., immune checkpoint inhibitors), a strategy recently delivering first exciting results in clinical settings. This review summarizes the promising but still extremely fragmentary knowledge on the interplay of metal drugs with the fidelity of anticancer immune responses but also their role in adverse effects. It highlights that, at least in some cases, metal drugs can induce long-lasting anticancer immune responses. Important steps in this process comprise altered visibility and susceptibility of cancer cells toward innate and adaptive immunity, as well as direct impacts on immune cell populations and the tumor microenvironment. On the basis of the gathered information, we suggest initiating joint multidisciplinary programs to implement comprehensive immune analyses into strategies to develop novel and smart anticancer metal compounds.