BIRC5 and histiocytic sarcoma: The aims of this study were to comparatively analyze the gene expression levels of survivin, in addition to IAP and Bcl-2 family members, in dogs with histiocytic sarcoma (hereafter referred to as HS dogs) and to evaluate the effects of survivin knockdown using siRNA on biological activities, including cell viability, chemosensitivity and hemophagocytic activity, in 4 CHS cell lines derived from different sources.