Bone marrow derived mesenchymal stem cells (MSC) are promising tools for lung cancer therapy considering their tendencies for tumour homing and low immunogenicity. Tumour necrosis factor related apoptosis inducing ligand (TRAIL) is a pro-apoptotic protein that induces selective apoptosis of tumour cells, while sparing normal cells. Therefore, it is expected that MSCs engineered to produce TRAIL will home to and kill cancer cells.
In this study, two lentiviral vectors were constructed to express the full-length (flT) or a truncated soluble form of TRAIL (sT) driven by a CMV promoter/enhancer. A secretion targeting sequence and an isoleucine zipper (ILZ) peptide were sequentially added to the N-terminal of the soluble TRAIL to produce secreted and trimerised TRAIL. TRAIL lentiviruses were prepared and human BM-MSCs were transduced with a multiplicity of infection (MOI) of 2. FACS analysis by anti-TRAIL antibody staining demonstrated that over 99% of flT or sT viruses transduced cells are positive for TRAIL expression. TRAIL expression was further confirmed by Western blotting and ELISA assays. The flT or sT expressing MSCs both showed similar level of cellular TRAIL expression (~350 ng TRAIL per 1 mg of total cellular protein).
Co-culture of cancer cells with transduced MSCs determined the cancer killing efficacy of MSCs expressing flT or sT. Twenty cancer cell lines were tested and classified into four TRAIL response groups; high, medium, low, and no sensitivity to recombinant TRAIL (rTRAIL) at the concentration of 50 ng/ml. At the co-culture ratio of 4:1 cancer to MSC cells, MSC-sT treatment showed no or only marginal cancer cell killing effect, in contrast, MSC-flT showed promising effects on all tested cell lines, with an apoptosis induction rate ranging between 35–75%. In groups designated as high, moderate and low, MSC-flT are as effective as rTRAIL and induced marked cell death (p < 0.001) in cell lines which showed no sensitivity to rTRAIL (Figure).
In conclusion, these results demonstrate MSC-flT is a promising cell therapy and have great potential for clinical treatment of lung cancers and pleural metastases.
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