Figure 1. Ionizing radiation and the Toll-like receptor 7 agonist imiquimod cooperate in converting malignant cells into an in situ anticancer vaccine. Radiation-induced immunogenic cell death allow for the release of tumor-associated antigens that are taken up by dendritic cells (DCs), which abundantly infiltrate imiquimod-treated tumors. Activated DCs loaded with tumor-associated antigens migrate to tumor-draining lymph nodes (TDLNs), where they activate naïve tumor-specific T cells. Activated tumor-specific T cells traffic to both irradiated and non-irradiated tumors. The cytotoxic activity of T cells is facilitated by the imiquimod- or radiation-induced upregulation of MHC class I molecules and intercellular adhesion molecule 1 (ICAM1) on the surface of transformed cells (TCs).