Lung cancer is a major public health problem in the western world, and gene therapy strategies to tackle this disease systemically are often impaired by inefficient delivery of the vector to the tumour tissue. Some of the main factors inhibiting systemic delivery are found in the blood stream in the form of red and white blood cells (WBCs) and serum components. Mesenchymal stem cells (MSCs) have been shown to home to tumour sites and could potentially act as a shield and vehicle for a tumouricidal gene therapy vector. Here, we describe the ability of an adenoviral vector expressing TRAIL (Ad.TR) to transduce MSCs and show the apoptosis-inducing activity of these TRAIL-carrying MSCs on A549 lung carcinoma cells. Intriguingly, using MSCs transduced with Ad.enhanced-green-fluorescent-protein (EGFP) we could show transfer of viral DNA to cocultured A549 cells resulting in transgenic protein production in these cells, which was not inhibited by exposure of MSCs to human serum containing high levels of adenovirus neutralizing antibodies. Furthermore, Ad.TR-transduced MSCs were shown not to induce T-cell proliferation, which may have resulted in cytotoxic T-cell-mediated apoptosis induction in the Ad.TR-transduced MSCs. Apoptosis was also induced in A549 cells by Ad.TR-transduced MSCs in the presence of physiological concentrations of WBC, erythrocytes and sera from human donors that inhibit or neutralize adenovirus alone. Moreover, we could show tumour growth reduction with TRAIL-loaded MSCs in an A549 xenograft mouse model. This is the first study that demonstrates the potential therapeutic utility of Ad.TR-transduced MSCs in cancer cells and the stability of this vector in the context of the blood environment.

Disseminating tumors are one of the gravest medical problems. Here, we combine the tumor-specific apoptosis-inducing activity of tumor necrosis factor-related apoptosisinducing ligand (TRAIL) with the ability of mesenchymal stem cells (MSCs) to infiltrate both tumor and lymphatic tissues to target primary tumors as well as disseminated cancer cells in a human pancreatic cancer mouse model. Furthermore, we targeted X-linked inhibitor of apoptosis protein (XIAP) by RNA interference (RNAi) inside the cancer cells to make use of the apoptosis sensitization as well the antimetastatic effect that is afforded by XIAP silencing. We generated MSCs, termed MSC.sTRAIL, that express and secrete a trimeric form of soluble TRAIL (sTRAIL). MSC.sTRAIL triggered limited apoptosis in human pancreatic carcinoma cells that were resistant to soluble recombinant TRAIL, which is most likely due to the enhanced effect of the direct, cell-mediated delivery of trimeric TRAIL. MSC.sTRAIL-mediated cell death was markedly increased by concomitant knockdown of XIAP by RNAi in the cancer cells. These findings were confirmed in xenograft models, in which tumors from the parental pancreatic carcinoma cells showed only growth retardation on treatment with MSC.sTRAIL, whereas tumors with silenced XIAP that were treated with MSC.sTRAIL went into remission. Moreover, animals with XIAP-negative xenografts treated with MSC.sTRAIL were almost free of lung metastasis, whereas animals treated with control MSCs showed substantial metastatic growth in the lungs. In summary, this is the first demonstration that a combined approach using systemic MSC-mediated delivery of sTRAIL together with XIAP inhibition suppresses metastatic growth of pancreatic carcinoma.

What We Already Know about This Topic What This Article Tells Us That Is New Background Human mesenchymal stromal cells demonstrate promise for acute respiratory distress syndrome, but current studies use highly heterogenous cell populations. We hypothesized that a syndecan 2 (CD362)–expressing human mesenchymal stromal cell subpopulation would attenuate Escherichia coli–induced lung injury and enhance resolution after ventilator-induced lung injury. Methods In vitro studies determined whether CD362+ human mesenchymal stromal cells could modulate pulmonary epithelial inflammation, wound healing, and macrophage phagocytosis. Two in vivo rodent studies determined whether CD362+ human mesenchymal stromal cells attenuated Escherichia coli–induced lung injury (n = 10/group) and enhanced resolution of ventilation-induced injury (n = 10/group). Results CD362+ human mesenchymal stromal cells attenuated cytokine-induced epithelial nuclear factor kappa B activation, increased epithelial wound closure, and increased macrophage phagocytosis in vitro. CD362+ human mesenchymal stromal cells attenuated Escherichia coli–induced injury in rodents, improving arterial oxygenation (mean ± SD, 83 ± 9 vs. 60 ± 8 mmHg, P < 0.05), improving lung compliance (mean ± SD: 0.66 ± 0.08 vs. 0.53 ± 0.09 ml · cm H2O−1, P < 0.05), reducing bacterial load (median [interquartile range], 1,895 [100–3,300] vs. 8,195 [4,260–8,690] colony-forming units, P < 0.05), and decreasing structural injury compared with vehicle. CD362+ human mesenchymal stromal cells were more effective than CD362− human mesenchymal stromal cells and comparable to heterogenous human mesenchymal stromal cells. CD362+ human mesenchymal stromal cells enhanced resolution after ventilator-induced lung injury in rodents, restoring arterial oxygenation (mean ± SD: 113 ± 11 vs. 89 ± 11 mmHg, P < 0.05) and lung static compliance (mean ± SD: 0.74 ± 0.07 vs. 0.45 ± 0.07 ml · cm H2O−1, P < 0.05), resolving lung inflammation, and restoring histologic structure compared with vehicle. CD362+ human mesenchymal stromal cells efficacy was at least comparable to heterogenous human mesenchymal stromal cells. Conclusions A CD362+ human mesenchymal stromal cell population decreased Escherichia coli–induced pneumonia severity and enhanced recovery after ventilator-induced lung injury.