Regulation and action of interferon-stimulated gene 15 in breast cancer cells.

Interferon-stimulated gene 15 (ISG15) is a critical ubiquitin-like protein that can be conjugated to proteins via the ISGylation system to modify them posttranslationally. Furthermore, ISG15 can be detected as non-conjugated or free, intracellularly and/or extracellularly. Both conjugated and free ISG15 participate in different cancer types, including breast cancer. Here, we highlighted the findings on ISG15 and protein ISGylation, and their implications in the field of breast cancer research. ISG15 emerges as a central element in mammary tumors and may become a crucial protein in the strategies for detection, prognosis, and therapy of breast cancer.