Overview of serpin B9 and its roles in cancer (Review).

Serine proteinase inhibitor B9 (serpin B9) is a member of the serine protease inhibitor superfamily, which is widely found in animals, plants and microorganisms. Serpin B9 has been reported to protect cells from the immune‑killing effect of granzyme B (GrB) released by lymphocytes. In recent years, an increasing number of studies have indicated that serpin B9 is involved in tumour apoptosis, immune evasion, tumorigenesis, progression, metastasis, drug resistance and even in maintaining the stemness of cancer stem cells (CSCs). Moreover, according to clinical studies, serpin B9 has been demonstrated to be significantly associated with the development of precancerous lesions, a poor prognosis and ineffective therapies, suggesting that serpin B9 may be a potential target for cancer treatment and an indicator of cancer diagnosis; thus, it has begun to attract increased attention from scholars. The present review concisely described the structure and biological functions of the serpin superfamily and serpin B9. In addition, related research on serpins in cancer is discussed in order to provide a comprehensive understanding of the role of serpin B9 in cancer, as well as its clinical significance for cancer diagnosis and prognosis.