Mitochondria transfer from Jurkat cells to MSCs was obviously inhibited by anti-ICAM-1 treatment (Fig.?5a, b), which was further confirmed by flow cytometry analysis (Fig.?5c, d). cells to MSCs was again detected by flow cytometry and confocal microscopy. Finally, we verified our findings using human primary T-ALL cells cocultured with MSCs. Results Chemotherapeutic drugs caused intracellular oxidative stress in Jurkat cells. Jurkat cells transfer mitochondria to MSCs but receive few mitochondria from MSCs, resulting in 1H-Indazole-4-boronic acid chemoresistance. This process of mitochondria transfer is usually mediated by tunneling nanotubes, which are protrusions that extend from the cell membrane. Moreover, we found that most Jurkat cells adhered to MSCs in the coculture system, which was mediated by the adhesion molecule ICAM-1. Treatment with a neutralizing antibody against ICAM-1 led to a decreased number of adhering Jurkat cells, decreased mitochondria transfer, and increased chemotherapy-induced cell death. Conclusions We 1H-Indazole-4-boronic acid show evidence that mitochondria transfer from Jurkat cells to MSCs, which is usually mediated by cell adhesion, may be a potential therapeutic target for T-ALL treatment. Electronic supplementary material The online version of this article (10.1186/s13045-018-0554-z) contains supplementary material, which is available to authorized users. test. Statistical differences were determined by GraphPad Prism 5.0 software (GraphPad Software Inc., CA, USA). A two-sided value ?0.05 was considered to be statistically significant. For the other experimental procedures, please see Additional?file?1. Results Jurkat cells transfer mitochondria to MSCs when exposed to chemotherapeutic drugs We previously found that MSCs could protect T-ALL cells from chemotherapeutic cell death in indirect (Transwell) and 1H-Indazole-4-boronic acid direct coculture system. Furthermore, we showed that exposure of T-ALL cells to MSCs decreased mitochondrial ROS levels via the ERK/Drp1 pathway under both culture conditions, However, when exposed to chemotherapeutic drugs, Jurkat cells in direct contact with MSCs exhibited significantly lower mitochondrial ROS levels than cells in the Transwell system [27]. We thus wondered whether there were other mechanisms by which MSCs decrease ROS levels in Jurkat cells in a cytotoxic environment. As mitochondria are the key source of intracellular ROS, alterations in mitochondrial number and function could influence the intracellular ROS levels. We thus explored whether mitochondria transfer occurred between MSCs and Jurkat cells and participated in MSC-induced leukemia cell chemoresistance. First, MSCs were labeled with green fluorescent protein (GFP) by lentiviral transduction to distinguish them from Jurkat cells in the coculture system. These cells were then purified via fluorescence-activated cell sorting (FACS). Prior to coculture experiments, we also labeled 1H-Indazole-4-boronic acid MSCs and Jurkat cells with the mitochondria-specific dye MitoTracker Red to observe mitochondria transfer between MSCs and Jurkat cells. Twelve hours later, 300?nM ara-C or 100?nM MTX was added to the coculture system. After 2?days of coculture, we quantified mitochondria transfer by flow cytometry. The results showed that 32.20??5.21% (ara-C-treated group) or 30.00??4.31% (MTX-treated group) of GFP-labeled MSCs were Red+, indicating that approximately 30% of the MSCs received mitochondria from Jurkat cells (Fig.?1a). We also 4933436N17Rik stained GFP-labeled MSCs with MitoTracker Red before coculture with Jurkat cells. However, only 0.59??0.14% (ara-C-treated group) or 0.62??0.15% (MTX-treated group) of the Jurkat cells were Red+ after 2?days of coculture, indicating that few Jurkat cells received mitochondria from MSCs (Fig.?1b). Taken together, these results showed that Jurkat cells could transfer mitochondria to MSCs when treated with chemotherapeutic drugs. We further performed confocal microscopy to directly observe mitochondria transfer. We first labeled Jurkat cells with MitoTracker Red before coculture with GFP-labeled MSCs. After 3?days of coculture, specific fields of view as well as side views of confocal imaging showed that mitochondrial Red fluorescence was internalized in GFP-labeled MSCs (Fig.?1c). In addition, the areas of red foci in GFP-labeled MSCs increased in a time-dependent manner from day 1 to day 3 (Fig.?1d, e), indicating that mitochondria transfer from Jurkat cells to MSCs was dynamic. Open in.