Reversible transfection of human melanocytes mediated by Cre/loxP site-specific recombination system and SV40 large T antigen

Downregulation of Blimp1 inhibits the maturation of bone marrow-derived dendritic cells

Modulation of differentiation of dendritic cells (DCs), which are derived from bone marrow cells, may influence their maturation and consequently regulate their ability to present antigens to alloreactive T lymphocytes. B lymphocyte‑induced maturation protein‑1 (Blimp1) is a master regulator of immunocyte differentiation, which has been investigated for its effect on DCs. In the present study, a lentivirus was used as a vector to transduce Blimp1‑short hairpin (sh)RNA into primary bone marrow cells during their differentiation to DCs. Lentiviral‑mediated Blimp1‑shRNA (lenti‑shRNA‑Blimp1) had a transduction efficiency of >60% in DC precursors. Lenti‑shRNA‑Blimp1 significantly downregulated the expression levels of Blimp1 and modulated the expression of its target proteins, including class II major histocompatibility complex (MHC) transactivator, c‑myc and interleukin‑6. Although lenti‑shRNA‑Blimp1 did not interfere with the differentiation of bone marrow cells to DCs, it inhibited DC maturation by decreasing the expression of surface MHC‑II molecules, but not the expression of MHC‑I molecules and co‑stimulatory molecules [cluster of differentiation (CD)80/CD86]. Subsequently, alloreactive T cell proliferation was alleviated and regulatory T cells were expanded in response to lenti‑shRNA‑Blimp1. A toxicity assay indicated that the morphology and proliferation of cultured DCs were mildly influenced by the lentiviral vector, indicating that the use of alternative vectors with minimal or no toxicity could be investigated in future studies. In conclusion, transduction with lenti‑shRNA‑Blimp1 modulated the maturation of DCs via MHC‑II molecule suppression and inhibited alloreactive T cell activation. The present findings supported the application of Blimp1‑based intervention as a novel approach to induce immature DCs for further immunological research.

Reversible immortalization of rat pancreatic β cells with a novel immortalizing and tamoxifen-mediated self-recombination tricistronic vector

Although the strategy of "Cre/LoxP-based reversible immortalization" holds great promise to overcome the cellular senescence of primary cell cultures for their further use, a secondary gene transfer for Cre expression is usually utilized to trigger the excision of the immortalizing genes in a large number of cells, thus presenting a formidable hurdle for large-scale application. We modified the strategy by utilizing a tricistronic retroviral vector pLCRSTP, in which Cre-ER, simian virus 40 large T antigen (SV40LTAg) oncogene, and a reporter gene were flanked by the same pair of LoxA sites. Five immortalized rat pancreatic β cell clones transduced with pLCRSTP, and six immortalized rat pancreatic β cell clones co-transduced with pLCRSTP and another vector encoding the human telomerase reverse transcriptase (hTERT) gene, were obtained, respectively. The Cre-ER protein could be induced to translocate from the cytoplasm to the nucleus by 4-hydroxytamoxifen to make SV40LTAg, hTERT and the Cre-ER gene itself excise without a secondary gene transfer. Our studies suggest that this system is useful to expand rat β cells and may allow for large-scale production due to its simpler manipulation.

Nucleofection is a highly effective gene transfer technique for human melanoma cell lines

Despite the increasing use of gene transfer strategies in the study of cellular and molecular biology, melanoma cells have remained difficult to transfect in a safe, efficient, and reproducible manner. In the present study, we report the successful use of nucleofector technology to transfect human melanoma cell lines. This technology uses an empirically derived combination of cell line-specific solutions and nucleofector programmes to electroporate nucleic acid substrates directly into the cell nucleus. Using a colorimetric beta-galactosidase assay, we optimized nucleofection parameters for 13 melanoma cell lines, leading to maximum transfection efficiency and cell survival. The combinations of cell solutions NHEM or T and nucleofector programmes A-24 or U-20 produced the best results. We compared nucleofection with two commercially available lipid-based gene transfer systems, effectene and lipofectamine 2000 using a green fluorescent protein reporter vector. Nucleofection demonstrated a 3- to 40-fold improvement in transfection efficiency when compared with the lipid-based counterparts. Nucleofection was also superior in transfecting small-interfering RNA (siRNA) as determined by Western blot analysis. Lastly, we applied nucleofection to the simultaneous transfection of a p53-dependent luciferase plasmid and p53-siRNA. Experiments using dual transfection showed knockdown of p53 expression and silencing of the reporter plasmid. In conclusion, nucleofection is highly effective for the transfer of nucleic acid substrates, singly or in combination, into human melanoma cell lines.