Combined action of suicide gene exosomes from pancreatic cancer-associated fibroblasts and from mesenchymal stem cells as a pancreatic ductal adenocarcinoma treatment approach.

[BACKGROUND] The pancreatic cancer-associated fibroblasts (pCAFs) are among the most active components of the pancreatic ductal adenocarcinoma (PDAC). The pCAFs being of mesenchymal stem/stromal cell origin, interact directly with tumor stromal elements, modulate tumor development, and are involved in the formation of pre-metastatic niches that result in unsatisfactory PDAC treatment outcomes. This study aimed to develop an innovative approach for the treatment of desmoplastic pancreatic carcinoma via intracellularly targeted exosomes derived from pCAFs and from mesenchymal stem cells (MSCs) transduced with the suicide gene - yeast cytosine deaminase::uracil phosphoribosyl transferase (yCD::UPRT).

[METHODS] pCAFs were isolated from four PDAC tumor specimens and MSCs from various tissues. Their transduction with yCD::UPRT gene produce homogenous gene transduced cell populations capable of secreting suicide gene exosomes. Both gene- transduced and naive cells and their exosomes underwent characterization by biophysical, biochemical, microscopic, and LC-MS/MS proteomic methods. Tumor cell-killing functionality was assessed using three pancreatic cancer cell lines. The killing efficacy of combined suicide gene exosomes of MSCs and pCAFs was measured in a mixture of pCAFs and MIA PaCa-2 cells as a simulated desmoplastic pancreatic tumor in vitro.

[RESULTS] MSCs and pCAFs suicide gene exosomes act as cancer cell-targeted drugs, effectively killing pancreatic carcinoma cells. Exosomes intracellular convert the non-toxic prodrug 5-fluorocytosine into cytotoxic 5-fluorouracil and its metabolites in a dose-dependent manner. In experiments simulating the desmoplastic microenvironment of PDAC, we have found that the suicide gene exosomes from both cells conjugated with prodrug effectively target and inhibit the growth of simulated PDAC.

[CONCLUSION] Exosomes containing the yCD::UPRT gene from pCAFs and MSCs function as "Trojan horse" therapies, efficiently and dose-dependently eliminating pancreatic cancer cells. PDAC environment-targeted yCD::UPRT-gene exosomes from MSCs and pCAFs show promise for a novel PDAC treatment.