Helper-like innate lymphoid cells and cancer immunotherapy.

Immunotherapies have revolutionized cancer treatment over the last 20 years. They aim either to boost immune cell activation or decrease immune cell inhibition, to improve control over cancer development. Various strategies for improving tumor immunity have been tested. Some have been approved and others are currently in clinical trials. They target the immune system itself, the tumor cells or the microenvironment. Most focus on enhancing T-cell responses, notably through infusions of activating cytokines, the adoptive transfer of activated or engineered T cells, or immune checkpoint inhibitors. ILCs have also emerged as an interesting target for immunotherapy, initially due to the anti-tumor activities of cytotoxic NK cells. However, the other helper-like ILCs can also infiltrate the tumor microenvironment, having either pro- or anti-tumor effects, depending on their phenotype and the type of cancer. Moreover, given the similarities between helper ILCs and T cells in terms of their cytokine profiles and the surface markers they express, immunotherapies targeting T cells may also target helper-like ILCs. We provide here an overview of the field, summarizing the evidence for a role of helper-like ILCs and ways of targeting these cells in solid tumors and hematological malignancies.