Exosome delivery of tumor suppressive microRNA-7 to cervical cancer cells: A novel approach for regulating cervical cancer cell growth (230)

Abstract

<b>Objectives:</b> Exosomes are highly stable nanosized extracellular vehicles released from cells for cell-cell communication that protect their cargo from degradation in an array of environments. Adipocytederived stem cell exosomes (ACS-exos) have unique properties that allow them to be engineered as delivery vehicles in various biological settings. The ability to manipulate the exosomes and their contents allows exosomes to be a focus of cancer therapeutics. MicroRNAs (miRNAs) are small non-coding RNAs that control gene translation and expression. Abnormal expression of tissue miRNAs has been associated with significant alterations in cell growth. MicroRNA-7 (miR-7) has an inhibitory effect on X-Linked Inhibitor of Apoptosis Protein (XIAP), which is over-expressed in cervical cancer cells, inhibiting apoptosis and promoting cell proliferation. miR-7 down-regulates XIAP in cervical carcinoma cells, increasing apoptosis and suppressing colony formation. Our objective was to develop a new therapeutic approach for cervical cancer by employing ACS-exos to deliver miR-7 to cervical cancer cells so as to elicit regulatory effects on XIAP. <b>Methods:</b> The cervical cancer cell line C-33 A was used to demonstrate the effect of miR-7 on XIAP expression. An miRNA mimic hsa-miR-7 was used for transfection. The presence of XIAP in C-33 A cells was established using Western blot, and then the cells were transfected with miR-7 using Lipofectamine ^TM RNAiMAX. The transfected cells were collected 24 and 48 hours after treatment, and the expression of XIAP was tested using Western blot. To collect exosomes, adipocyte-derived stem cells (ACS) were cultured in a growth medium with exosome-depleted FBS for 72 hours, followed by differential centrifugation. The isolated exosomes were then transfected with either miR-7 or Texas-Red fluorescent-labeled siRNA (TX-Red) using Exo-Fect^TM Exosome Transfection Reagent. Transfected exosomes were added to the C-33 A cell culture media. The cells were analyzed under a fluorescence microscope after 24 and 48 hours of growth. Western blot was used to study the expression of XIAP. The presence of Beta-Tubulin was also tested as a loading control. <b>Results:</b> The presence of XIAP in C-33 A cells was confirmed by Western blot. In the cells transfected with miR-7, Western blot demonstrated downregulation of XIAP after both 24 and 48 hours. Successful nucleotide transfection of ACS-exos and oligonucleotide integration into the C-33 A cells was confirmed by fluorescence microscopy, which demonstrated the intracellular presence of TX-Red in only the positive control C-33 A cell line. A similar downregulation of XIAP in the cells treated with miR-7 transfected ACS-exos was seen as in the miR-7 transfected cells by Western blot. Beta-Tubulin expression was seen across the control and treatment cells. <b>Conclusions:</b> Delivery of tumor-suppressive miR-7 via ACS-exos elicited downregulation of XIAP. The isolation and successful transfection of exosomes demonstrated are key processes in utilizing exosomes for cancer therapeutics. Further, the exosome cargo nucleotides integrated into the target cells and resulted in alteration of protein expression. Additional studies examining the effects of exosome-delivered miR-7 on cervical cancer cell viability, proliferation, invasion are underway. These findings highlight the promising therapeutic potential of exosomes in cervical cancer.