Targeted delivery of oncolytic drugs such as vincristine sulfate during chemotherapy continues to present challenges, and one of the major side effects of the non-specific delivery of this drug is neurotoxicity.
In a recent study published in Scientific Reports, researchers from Egypt investigated whether loading vincristine sulfate into mesenchymal stem cell-derived exosomes could improve the targeted delivery of the drug specifically to cancer stem cells, which have a critical role in the initiation and maintenance of tumors, as well as in chemotherapy resistance and metastasis.
Study: Stem cells derived exosomes as biological nano carriers for VCR sulfate for treating breast cancer stem cells. Image Credit: Vshivkova/Shutterstock.com
Background
The World Health Organization statistics report that cancer-related mortalities each year are in the millions. The survival rates for various types of cancers are often dependent on how the tumors respond to radiation therapy or chemotherapy, as well as the probability of metastasis.
Tumor-initiating cells or cancer stem cells that have mutations enabling them to circumvent the regulatory mechanisms that prevent unchecked proliferation play a central role in both these processes and in the initiation and growth of tumors.
Stem cells, such as mesenchymal stem cells, can differentiate into various mature functional cells.
Recent research has focused on using mesenchymal stem cell-derived exosomes, which are small vesicles that carry biomolecules, for targeted drug delivery, controlling immune responses, and lowering inflammation.
About the study
In the present study, the researchers investigated the efficacy of mesenchymal stem cell-derived exosomes carrying vincristine sulfate in targeting cancer stem cells from a ductal carcinoma breast cancer cell line.
They aimed to understand whether these vincristine sulfate-carrying exosomes could improve the targeted delivery of the drug while reducing the side effects due to non-specific drug delivery.
Mesenchymal stem cells were obtained from the bone marrow of rats through isolation and culturing of bone marrow cells, as well as morphological and flow cytometry-based identification of mesenchymal stem cells.
Subsequently, the exosomes derived by culturing these mesenchymal stem cells were isolated and purified through ultracentrifugation and characterized using transmission electron microscopy and flow cytometry.
The mesenchymal stem cell-derived exosomes were quantified using the bicinchoninic acid protein assay, following which the probe sonication method was used to load the vincristine sulfate into the exosomes.
Cellulose tubing used in dialysis membranes and phosphate-buffered saline were used to test the loading capacity of the exosomes.
The cytotoxicity of the vincristine sulfate-carrying exosomes was tested against cancer stem cells obtained from the T4D7 breast cancer cell line.
The cells were treated with vincristine sulfate-carrying exosomes, after which the viability of the cultured ductal carcinoma cells was assessed using the sulforhodamine B (SRB) assay.
Flow cytometry was then employed to determine the efficacy of the vincristine sulfate treatment by assessing the expression of CD24-/CD44+, which are the markers used to identify cancer stem cells.
Major findings
The study found that while the efficacy of vincristine sulfate had not been reduced by transporting it using mesenchymal stem cell-derived exosomes, the exosome significantly improved the targeted delivery of vincristine to the cancer stem cell as compared to free vincristine sulfate.
Furthermore, given the nano size of the vincristine sulfate molecules, the mesenchymal stem cell-derived exosomes could hold 0.325 mg of the drug.
The results from the SRB assay indicated that the cytotoxicity of the vincristine sulfate that was delivered via the exosomes was the same as that of free vincristine sulfate, suggesting that the mesenchymal stem cell-derived exosome did not hinder the cytotoxicity of the drug.
The efficacy of the drug delivery system was tested using flow cytometry with antibodies against the cancer stem cell markers CD24-/CD44+. The control cell line not treated with the oncolytic showed 10.5% cancer stem cells, while those treated with vincristine sulfate alone had 6.68% cancer stem cells.
Mesenchymal stem cell-derived exosomes carrying vincristine sulfate were the most effective form of treatment, with only 2.8% of cancer stem cells remaining in the cell after treatment.
Surprisingly, the study also reported that treatment with mesenchymal stem cell-derived exosomes alone decreased CD24-/CD44+ cells from 10.5% to 4.8%.
Given that these exosomes did not contain any oncolytic molecules that could be cytotoxic, these findings indicate the potential for mesenchymal stem cell-derived exosomes to be used as a possible cancer treatment option with no cytotoxicity.
Conclusions
To summarize, the study investigated the efficacy of mesenchymal stem cell-derived exosomes in targeted chemotherapeutic drug delivery by testing the cytotoxicity of vincristine sulfate-carrying exosomes against cancer stem cells obtained from a breast cancer cell line.
The results showed that not only was the cytotoxicity of vincristine sulfate unaffected by the exosome but that the exosome-vincristine sulfate complex was more effective in targeting and reducing the concentration of cancer stem cells than vincristine sulfate alone.
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