Additional Supporting Information may be found in the online version of this article.

sc-12-0952_sm_SupplFigure1.pdf464KSupplementary figure S1. A. Flow cytometry analysis. MSC 293T cells have similar CD markers as HEK 293T and lack cancer stem cell phenotype. Importantly, MSC 293T cell population is free of mesenchymal stromal cells. B. Large-T antigen genomic PCR suggests that MSC 293T cells develop from HEK 293T cells. The analysis resulted in a 180-bp amplicon, which indicates the large-T antigen in control HEK 293T and MSC 293T cells. Mesenchymal stromal cells lacked the large-T PCR amplicon. C. The co-culture induced microsatellite instability. Microsatellite analysis of parental MSC, HEK 293T cells and nine MSC 293T cell subclones. Note that the genomic DNA isolated from the tumor refers to the microsatellite structure of in vivo transplanted MSC 293T cells. The microsatellite structure of clones 2 (D13S317), clone 6 (CSF1PO), clone 7 (D165539, vWA), and clone 10 (vWA) differed from that of STR profiles in the DSMZ database (Deutsche Sammlung von Mikroorganismen und zellkulturen), which was detected also in in vivo transplanted tumor-derived genomic DNA. Clone 3 was lost during the isolation procedure.
sc-12-0952_sm_SupplFigure2.pdf250KSupplementary figure S2 A,B. Phosphokinase array of MSC 293T showed significantly increased mitogen activation and stress signaling pathways as compared to parental HEK 293T cells. The p-values correspond to p<0.05 (*), p<0.01 (**), p<0.001 (***) as compared to HEK 293T controls.
sc-12-0952_sm_SupplFigure3.pdf296KSupplementary figure S3. Limiting dilution transplantation showed inability of a low number of grafted MSC 293T cells to form tumors thereby suggesting the lack of cancer stem cell characteristics. Mice were injected subcutaneously with 100, 1000 or 10,000 cells. Red circles, the location of the graft, black arrows, the site of a signal.
sc-12-0952_sm_SupplFilm1.mpg4993KSupplementary film 1. Co-culture of untreated MSCs with HEK 293T cells in fresh 10% FBS β-medium. Note the remarkable motility of MSCs in eluding contact with HEK 293T cells that generated membrane protrusions towards MSCs. HEK 293T cells showed a high number of cell divisions thereby reducing the possibility for MSC to migrate.
sc-12-0952_sm_SupplFilm2.mpg21804KSupplementary film 2. Co-culture of MSCs pre-treated with HEK 293T conditioned serum-free medium with HEK 293T cells. Note that the MSCs incubated in these conditions did not move and were surrounded by HEK 293T cells that formed a physical connection with MSC. Consequently, the MSC lost their cytoplasm leaving only a fragmented nucleus.
sc-12-0952_sm_SupplFilm3.mpg11094KSupplementary film 3. The final stages of the co-culture showing the almost complete destruction of MSC.
sc-12-0952_sm_SupplMethods.pdf28KSupplementary Data

Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.