Metastatic Ovarian Cancer Can Be Efficiently Treated by Genetically Modified Mesenchymal Stromal Cells

Abstract

Due to late diagnosis, often recurrence, formation of metastases and resistance to commonly used chemotherapeutics human ovarian carcinoma represents a serious disease with high mortality. Adipose tissue-derived mesenchymal stromal cells (AT-MSC) can serve as vehicles for therapeutic genes and we engineered AT-MSC to express either Herpes simplex virus thymidine kinase (HSVtk-MSC), which phosphorylates ganciclovir (GCV) to its toxic metabolites or yeast fused cytosine deaminase::uracil phosphoribosyltransferase (CD::UPRT-MSC), which converts 5-fluorocytosine (5-FC) to highly toxic 5-fluorouracil (5-FU). Here, we reported different responses of cytotoxicity mediated by CD::UPRT-MSC/5-FC treatment on human ovarian carcinoma cell lines-SKOV-3 and A2780 used in adherent or three-dimensional (3D) cell culture and we proved high potential of 3D model to predict results in our in vivo experiments. Both tumor cell lines showed similarly high chemosensitivity to the used treatment in adherent culture, but 3D model revealed severe discrepancy-only 36% of SKOV-3 cells but even 90% of A2780 cells were eliminated. This result served as a prognostic marker-we were able to achieve significantly decreased tumor volumes of subcutaneous xenografts of A2780 cells in nude mice and we prolonged tumor-free survival in 33% of animals bearing highly metastatic ovarian carcinoma after CD::UPRT-MSC/5-FC treatment.

Human mesenchymal stem cell-derived iron oxide exosomes allow targeted ablation of tumor cells via magnetic hyperthermia

“…24 Furthermore, Toro et al have shown an efficient treatment of the metastatic dissemination of the ovarian tumor by yCD-UPRT gene-modified AT-MSCs in nude mouse model. 25 The authors did not consider existence of MSC-exosomes with suicide gene mRNA; therefore, the explanation was linked to the bystander effect. Combined action of bystander effect and exosome internalization of metastases was likely involved.…”

Cytotoxic response of 5-fluorouracil-resistant cells to gene- and cell-directed enzyme/prodrug treatment

“…In order to verify these findings, we examined the effect of CD::UPRT-MSC/5-FC in a 3D co-culture model, as it was previously described to be suitable for prediction of therapeutic outcome [16,22]. Significant decrease in the 3D aggregate volume of HT-29/EGFP and therapeutic MSC was observed when treated with 5-FC in concentration gradient ranging from 10 to 1000 µg/ml.…”

“…The results were expressed as percentage of relative viability, and evaluated as in ref. [16]. Values were expressed as means of replicates ± SD, when luminescence of control cells without the prodrug was taken as reference.…”

“…The 3D aggregate co-culture of 3 × 10 3 tumor cells mixed with CD::UPRT-MSC (labeled with DiI) at a ratio of 5:1 (at least sextaplicates) were plated in ultra-low attachment U bottom 96-well plates (Corning 7007; Corning, USA) according to ref. [16]. Seventy-two hours after plating, when the aggregates were visible and tightly formed, the medium was supplemented with concentrations gradient of 5-FC ranging from 10 to 1000 µg/ml.…”

“…The ability of transduced cells to kill themselves by produced toxic metabolites (converted prodrug)-the so-called suicide effect-causes elimination of themselves, which means that their presence is not permanent in the tumor, thus predetermine MSC to become valuable vehicles for the delivery of various "suicide" transgenes to target tumor [10]. The CD::UPRT-MSC/5-FC regimen inhibited tumor growth in many models of cancer-colon carcinoma [11], prostate cancer [4], melanoma [8,12], medullary thyroid carcinoma [13], glioblastoma [5,14,15] including ovarian metastatic disease [16]. On the other hand, we demonstrated that particular human tumor cell lines differ in their response to CD::UPRT-MSC/5-FC system, and we identified specific factors influencing this response-expression level of enzymes of nucleotide metabolism, functional gapjunctional intercellular communication (GJIC) between cells and expression of ATP-binding cassette transporters [17].…”