- Survivin, encoded by BIRC5, is the smallest and most structurally distinct member of the IAP family, functioning alongside XIAP, cIAP1, cIAP2, Livin and NAIP. Unlike other IAPs that primarily regulate apoptosis through caspase inhibition or ubiquitination, Survivin plays a dual role: it supports cell survival and acts as a critical regulator of mitosis. Its unique expression pattern—high in embryonic tissues and cancers but nearly absent in most normal adult tissues—makes Survivin one of the most important tumour‑associated proteins in modern oncology.
- Survivin contains a single BIR (Baculovirus IAP Repeat) domain but lacks a RING ubiquitin ligase domain, distinguishing it structurally from XIAP, cIAP1 and cIAP2. Despite this, Survivin contributes to apoptosis suppression by interacting with caspase‑3 and caspase‑7 and by stabilising other anti‑apoptotic proteins. Survivin also cooperates with heat‑shock proteins such as Hsp90, which protect it from degradation and enhance its stability in tumour cells.
- One of Survivin’s defining roles is its function in cell division. Survivin is a core component of the Chromosomal Passenger Complex (CPC), which also includes Aurora B kinase, INCENP and Borealin. The CPC ensures proper chromosome alignment, segregation and cytokinesis. Loss of Survivin disrupts mitotic spindle formation, causes chromosomal instability and leads to mitotic catastrophe. This mitotic role explains why Survivin is essential during embryonic development and why its re‑expression in cancer supports rapid proliferation.
- Survivin also influences cell survival pathways. It modulates microtubule dynamics, enhances DNA repair responses and contributes to resistance against apoptosis induced by chemotherapy, radiotherapy and immune effector cells. Tumour cells frequently upregulate Survivin to maintain proliferation under stress and evade immune‑mediated killing.
- Survivin’s expression is tightly controlled by transcription factors such as STAT3, NF‑κB, HIF‑1α and E2F. Hypoxia, inflammation and oncogenic signalling all promote Survivin expression, linking it to tumour microenvironment dynamics. Because Survivin is rarely expressed in differentiated adult tissues, it is considered a tumour‑specific survival factor, making it an attractive target for cancer therapy.
- Therapeutic strategies targeting Survivin include antisense oligonucleotides, siRNA, immunotherapies, small‑molecule inhibitors and Survivin‑based cancer vaccines. Inhibiting Survivin sensitises tumour cells to apoptosis, disrupts mitosis and enhances responses to conventional therapies. Its central role in cancer progression, metastasis and therapy resistance has made Survivin one of the most intensively studied IAPs in translational oncology.
- In summary, Survivin is a unique IAP family member that integrates apoptosis suppression with essential mitotic functions. Its tumour‑specific expression, role in chromosome segregation and contribution to therapy resistance make Survivin a key regulator of cancer biology and a promising therapeutic target.
