Carrie A. Franzen

Characterization of Uptake and Internalization of Exosomes by Bladder Cancer Cells

Bladder tumors represent a special therapeutic challenge as they have a high recurrence rate requiring repeated interventions and may progress to invasive or metastatic disease. Exosomes carry proteins implicated in bladder cancer progression and have been implicated in bladder cancer cell survival. Here, we characterized exosome uptake and internalization by human bladder cancer cells using Amnis ImageStreamX, an image cytometer. Exosomes were isolated by ultracentrifugation from bladder cancer culture conditioned supernatant, labeled with PKH-26, and analyzed on the ImageStreamX with an internal standard added to determine concentration. Exosomes were cocultured with bladder cancer cells and analyzed for internalization. Using the IDEAS software, we determined exosome uptake based on the number of PKH-26+ spots and overall PKH-26 fluorescence intensity. Using unlabeled beads of a known concentration and size, we were able to determine concentrations of exosomes isolated from bladder cancer cells. We measured exosome uptake by recipient bladder cancer cells, and we demonstrated that uptake is dose and time dependent. Finally, we found that uptake is active and specific, which can be partially blocked by heparin treatment. The characterization of cellular uptake and internalization by bladder cancer cells may shed light on the role of exosomes on bladder cancer recurrence and progression.

Osteopontin Mediates an MZF1-TGF-β1-Dependent Transformation of Mesenchymal Stem Cells into Cancer Associated Fibroblasts in Breast Cancer

Interactions between tumor cells and cancer-associated fibroblasts (CAFs) in the tumor microenvironment significantly influence cancer growth and metastasis. Transforming growth factor-β (TGF-β) is known to be a critical mediator of the CAF phenotype, and osteopontin (OPN) expression in tumors is associated with more aggressive phenotypes and poor patient outcomes. The potential link between these two pathways has not been previously addressed. Utilizing in vitro studies using human mesenchymal stem cells (MSCs) and MDA-MB231 (OPN+) and MCF7 (OPN−) human breast cancer cell lines, we demonstrate that OPN induces integrin-dependent MSC expression of TGF-β1 to mediate adoption of the CAF phenotype. This OPN–TGF-β1 pathway requires the transcription factor, myeloid zinc finger 1 (MZF1). In vivo studies with xenotransplant models in NOD-scid mice showed that OPN expression increases cancer growth and metastasis by mediating MSC-to-CAF transformation in a process that is MZF1 and TGF-β1 dependent. We conclude that tumor-derived OPN engenders MSC-to-CAF transformation in the microenvironment to promote tumor growth and metastasis via the OPN–MZF1–TGF-β1 pathway.

Urothelial cells undergo epithelial-to-mesenchymal transition after exposure to muscle invasive bladder cancer exosomes

Bladder cancer, the fourth most common noncutaneous malignancy in the United States, is characterized by high recurrence rate, with a subset of these cancers progressing to a deadly muscle invasive form of disease. Exosomes are small secreted vesicles that contain proteins, mRNA and miRNA, thus potentially modulating signaling pathways in recipient cells. Epithelial-to-mesenchymal transition (EMT) is a process by which epithelial cells lose their cell polarity and cell–cell adhesion and gain migratory and invasive properties to become mesenchymal stem cells. EMT has been implicated in the initiation of metastasis for cancer progression. We investigated the ability of bladder cancer-shed exosomes to induce EMT in urothelial cells. Exosomes were isolated by ultracentrifugation from T24 or UMUC3 invasive bladder cancer cell conditioned media or from patient urine or bladder barbotage samples. Exosomes were then added to the urothelial cells and EMT was assessed. Urothelial cells treated with bladder cancer exosomes showed an increased expression in several mesenchymal markers, including α-smooth muscle actin, S100A4 and snail, as compared with phosphate-buffered saline (PBS)-treated cells. Moreover, treatment of urothelial cells with bladder cancer exosomes resulted in decreased expression of epithelial markers E-cadherin and β-catenin, as compared with the control, PBS-treated cells. Bladder cancer exosomes also increased the migration and invasion of urothelial cells, and this was blocked by heparin pretreatment. We further showed that exosomes isolated from patient urine and bladder barbotage samples were able to induce the expression of several mesenchymal markers in recipient urothelial cells. In conclusion, the research presented here represents both a new insight into the role of exosomes in transition of bladder cancer into invasive disease, as well as an introduction to a new platform for exosome research in urothelial cells.

PLK-1 Silencing in Bladder Cancer by siRNA Delivered With Exosomes

OBJECTIVE To use exosomes as a vector to deliver small interfering ribonucleic acid (siRNA) to silence the polo-like kinase 1 (PLK-1) gene in bladder cancer cells. MATERIALS AND METHODS Exosomes were isolated from both human embryonic kidney 293 (HEK293) cell and mesenchymal stem cell (MSC) conditioned media. Fluorescently labeled exosomes were co-cultured with bladder cancer and normal epithelial cells and uptake was quantified by image cytometry. PLK-1 siRNA and negative control siRNA were loaded into HEK293 and MSC exosomes using electroporation. An invasive bladder cancer cell line (UMUC3) was co-cultured with the electroporated exosomes. Quantitative reverse transcriptase polymerase chain reaction was performed. Protein analysis was performed by Western blot. Annexin V staining and MTT assays were used to investigate effects on apoptosis and viability. RESULTS Bladder cancer cell lines internalize an increased percentage of HEK293 exosomes when compared to normal bladder epithelial cells. Treatment of UMUC3 cells with exosomes electroporated with PLK-1 siRNA achieved successful knockdown of PLK-1 mRNA and protein when compared to cells treated with negative control exosomes. CONCLUSION HEK293 and MSC exosomes were effectively used as a delivery vector to transport PLK-1 siRNA to bladder cancer cells in vitro, resulting in selective gene silencing of PLK-1. The use of exosomes as a delivery vector for potential intravesical therapy is attractive.

The Constituents and Potential Targets of the Extracellular Matrix:Implications for Carcinogenesis and Cancer Treatment

The dense extracellular matrix consists of a multitude of proteins with important implications in tumorogenesis that extend beyond the maintenance of tissue integrity. Several of the main macromolecular constituents- proteoglycans, collagens, integrins, and syndecans will be discussed in this review, with particular attention to their roles in tumor initiation, invasion, angiogenesis, and metastasis. In addition, a brief synopsis of the role of enzymes that remodel the extracellular matrix will be provided. Finally, specific examples of targeted molecular therapies: anti-integrin agents, MMP inhibitors, and hyaluronidase will be discussed.

Exosomes: an evolving source of urinary biomarkers and an up-and-coming therapeutic delivery vehicle

Exosomes are a subset of small, extracellular vesicles secreted by all cell types, and can be isolated for virtually all bodily fluids that have been investigated. The importance of exosomal signaling in normal physiology and cancer is clear, with the transfer of host-cell cytoplasmic RNA, intracellular and membrane-bound proteins being well-described.