RIG-I immunotherapy overcomes radioresistance in p53-positive malignant melanoma.

Radiotherapy induces DNA damage, resulting in cell-cycle arrest and activation of cell-intrinsic death pathways. However, the radioresistance of some tumour entities such as malignant melanoma limits its clinical application. The innate immune sensing receptor retinoic acid-inducible gene I (RIG-I) is ubiquitously expressed and upon activation triggers an immunogenic form of cell death in a variety of tumour cell types including melanoma.

RIG-I Resists Hypoxia-Induced Immunosuppression and Dedifferentiation.

A hypoxic tumor microenvironment is linked to poor prognosis. It promotes tumor cell dedifferentiation and metastasis and desensitizes tumor cells to type-I IFN, chemotherapy, and irradiation. The cytoplasmic immunoreceptor retinoic acid-inducible gene-I (RIG-I) is ubiquitously expressed in tumor cells and upon activation by 5'-triphosphate RNA (3pRNA) drives the induction of type I IFN and immunogenic cell death.

RIG-I activation induces the release of extracellular vesicles with antitumor activity.

Activation of the innate immune receptor retinoic acid-inducible gene I (RIG-I) by its specific ligand 5'-triphosphate-RNA (3pRNA) triggers antitumor immunity predominantly via NK cell activation and direct apoptosis induction in tumor cells. However, how NK cells are mobilized to attack the tumor cells remains elusive. Here, we show that RIG-I activation induced the secretion of extracellular vesicles (EVs) from melanoma cells, which by themselves revealed antitumor activity and .

Inflammasome-Dependent Induction of Adaptive NK Cell Memory.

Monobenzone is a pro-hapten that is exclusively metabolized by melanocytes, thereby haptenizing melanocyte-specific antigens, which results in cytotoxic autoimmunity specifically against pigmented cells. Studying monobenzone in a setting of contact hypersensitivity (CHS), we observed that monobenzone induced a long-lasting, melanocyte-specific immune response that was dependent on NK cells, yet fully intact in the absence of T- and B cells. Consistent with the concept of "memory NK cells," monobenzone-induced NK cells resided in the liver and transfer of these cells conferred melanocyte-specific immunity to naive animals.