Department of Medicine, Division of Hematology, Oncology and Transplantation, University of Minnesota, Minneapolis, MN 55455, USA.
Moore Laboratory, Department of Cell Biology, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Exp Cell Res. 2014 Apr 15;323(1):178-188. doi: 10.1016/j.yexcr.2014.01.014. Epub 2014 Jan 24.
Tunneling nanotubes (TnTs) are long, non-adherent, actin-based cellular extensions that act as conduits for transport of cellular cargo between connected cells. The mechanisms of nanotube formation and the effects of the tumor microenvironment and cellular signals on TnT formation are unknown. In the present study, we explored exosomes as potential mediators of TnT formation in mesothelioma and the potential relationship of lipid rafts to TnT formation. Mesothelioma cells co-cultured with exogenous mesothelioma-derived exosomes formed more TnTs than cells cultured without exosomes within 24-48 h; and this effect was most prominent in media conditions (low-serum, hyperglycemic medium) that support TnT formation (1.3-1.9-fold difference). Fluorescence and electron microscopy confirmed the purity of isolated exosomes and revealed that they localized predominantly at the base of and within TnTs, in addition to the extracellular environment. Time-lapse microscopic imaging demonstrated uptake of tumor exosomes by TnTs, which facilitated intercellular transfer of these exosomes between connected cells. Mesothelioma cells connected via TnTs were also significantly enriched for lipid rafts at nearly a 2-fold higher number compared with cells not connected by TnTs. Our findings provide supportive evidence of exosomes as potential chemotactic stimuli for TnT formation, and also lipid raft formation as a potential biomarker for TnT-forming cells.
隧道纳米管 (TnT) 是长的、非黏附的、基于肌动蛋白的细胞延伸物，作为连接细胞之间细胞货物运输的导管。纳米管形成的机制以及肿瘤微环境和细胞信号对 TnT 形成的影响尚不清楚。在本研究中，我们探讨了外泌体作为间皮瘤中 TnT 形成的潜在介质，以及脂筏与 TnT 形成的潜在关系。与未培养外泌体的细胞相比，在 24-48 小时内，与外源性间皮瘤衍生的外泌体共培养的间皮瘤细胞形成了更多的 TnT；在支持 TnT 形成的条件下（低血清、高血糖培养基），这种效应最为显著（相差 1.3-1.9 倍）。荧光和电子显微镜证实了分离的外泌体的纯度，并显示它们主要位于 TnT 的底部和内部，以及细胞外环境中。延时显微镜成像显示 TnT 摄取肿瘤外泌体，这促进了这些外泌体在连接细胞之间的细胞间转移。通过 TnT 连接的间皮瘤细胞也显著富含脂筏，比未通过 TnT 连接的细胞高出近两倍。我们的发现提供了外泌体作为 TnT 形成的潜在趋化刺激物的支持证据，并且脂筏形成作为 TnT 形成细胞的潜在生物标志物。
