The emerging role of exosomes in survivin secretion.

The tumor microenvironment plays an integral part in the biology of cancer, participating in tumor initiation, progression, and response to therapy. Factors released by tumor cells themselves contribute in creating an environment mostly favorable but sometimes detrimental to the tumor. Survivin, one of the key members of the inhibitor of apoptosis (IAP) family of proteins, has been shown in the cytoplasm, mitochondria, nucleus, and most recently in the extracellular space, transported via small membrane bound vesicles called exosomes. Exosomes are secreted from hematopoietic, non-hematopoietic, tumor, and non-tumor cells, shuttling essential molecules such as proteins, RNAs, and microRNAs, all believed to be important for cell-cell and cell-extracellular communication. In this review, we discuss exosomal Survivin and its role in modifying the tumor microenvironment.