ISG15 and neoplasm: It has also been reported that the loss of autophagy extension proteins ATG5 or ATG7 in tumor cells leads to the accumulation of double-stranded DNA (dsDNA) in the cytoplasm, which activates stimulator of interferon genes (STING) signaling pathway and increases the expression level of ISG15, thereby promoting the acquisition of tumor-related phenotypes, such as invasion and proliferation [41].