Abstract 120: Cellular import of the inhibitor of apoptosis (IAP) protein survivin

The inhibitor of apoptosis (IAP) protein survivin is found overexpressed in virtually all human cancers and has been shown to correlate with poor prognosis. Recent work performed by our laboratory and that of others has demonstrated that survivin, when found or expressed extracellularly, is associated with a more aggressive disease form. In a variety of cancer cell lines grown in conditioned medium, rich with a flag/HA-tagged form of survivin, intracellular accumulation was readily detected. We found that survivin was internalized constitutively at a rate that was not affected by chelation of the conditioned medium in HeLa S cervical cancer cells. Instead, survivin internalization was modestly affected by lipid membrane stasis, induced by cooling the cells and the conditioned medium prior to and during incubation leading us to investigate if survivin's intracellular accumulation was dependent upon clathrin-coated pit-dependent endocytosis. Using dual-affinity protein purification and mass-spectrometry, survivin was found associating directly with clathrin, TNFR1, and the transferrin receptor (TfR), indicating that the process of survivin uptake may be through endocytosis. In addition, short-inhibitory RNA (siRNA) knockdown of TNFR1 and TfR as well as antibody blocking of these receptors significantly reduced survivin's intracellular accumulation. Further characterization of this novel survivin pool and its intracellular accumulation may reveal new strategies for the downregulation of survivin in cancer and ultimately better treatment strategies.Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 120.