CXCL9 and neoplasm: Radiotherapy can upregulate major histocompatibility complex I (MHC-I) molecules on the surface of tumour cells, promote the maturation of dendritic cells (DCs) and presentation of tumour-associated antigens, and enhance the secretion of cytokines required for T-cell infiltration, such as chemokine (C–X–C motif) ligand 9 (CXCL9), CXCL10, and CXCL16, from DCs and tumour cells, which are beneficial for the cytotoxic activity and expansion of CD8 + T cells [98] (Fig. 2).