Engineered tumor-tropic mesenchymal stem cells as targeted therapeutic delivery systems for refractory Ovarian cancer

The objective of this research was to develop a targeted clinically translatable stem cell-based system for the treatment of drug-resistant and metastatic ovarian cancer. To achieve this goal, we genetically engineered and isolated an adipose-derived stem cell (ASC) clone that expresses secretory human carboxylesterase-2 (shCE2) enzyme extracellularly and yeast cytosine deaminase: uracil phosphoribosyl transferase (yCD:UPRT) enzyme intracellularly for targeted combination enzyme/prodrug therapy. The shCE2 enzyme converts the prodrug irinotecan into its potent active metabolite SN-38, while yCD:UPRT transforms the prodrug 5-FC into the cytotoxic agent 5-FU. To evaluate the therapeutic potential of this system, we utilized ovarian cancer cells derived from patients with drug-resistant recurrent disease. All four lines exhibited sensitivity to SN-38 at sub-nanomolar concentrations, with a direct correlation observed between SN-38 sensitivity and expression levels of topoisomerase I. The cancer cells were subsequently xenografted into mice to establish metastatic intraperitoneal tumors. Following confirmation of active migration of the engineered ASCs toward the tumor sites through real-time bioluminescent imaging and immunohistochemistry, mice were treated either with prodrugs alone or in combination with the engineered ASCs. Therapeutic response and tumor relapses were assessed using quantitative bioluminescent imaging. The results of this study demonstrated that mice receiving the combination of ASCs and prodrugs exhibited complete eradication of metastatic tumors with no clinically significant toxicity to normal tissues. Overall, this study demonstrates that the developed ASC-directed dual enzyme/prodrug system is a highly effective and targeted approach for treating refractory ovarian tumors, with significant potential for clinical translation.