Efficient ablation by immunotoxin-mediated cell targeting of the cell types that express human interleukin-2 receptor depending on the internal ribosome entry site

Mode of transgene expression after fusion to early or late viral genes of a conditionally replicating adenovirus via an optimized internal ribosome entry site in vitro and in vivo

The expression of therapeutic genes by oncolytic viruses is a promising strategy to improve viral oncolysis, to augment gene transfer compared with a nonreplicating adenoviral vector, or to combine virotherapy and gene therapy. Both the mode of transgene expression and the locale of transgene insertion into the virus genome critically determine the efficacy of this approach. We report here on the properties of oncolytic adenoviruses which contain the luciferase cDNA fused via an optimized internal ribosome entry site (IRES) to the immediate early adenoviral gene E1A (AdDeltaE1AIL), the early gene E2B (AdDeltaE2BIL), or the late fiber gene (AdDeltafiberIL). These viruses showed distinct kinetics of transgene expression and luciferase activity. Early after infection, luciferase activities were lower for these viruses, especially for AdDeltaE2BIL, compared with nonreplicating AdTL, which contained the luciferase gene expressed from the strong CMV promoter. However, 6 days after infection, luciferase activities were approximately four (AdDeltaE1AIL) to six (AdDeltafiberIL) orders of magnitude higher than for AdTL, reflecting virus replication and efficient transgene expression. Similar results were obtained in vivo after intratumoral injection of AdDeltaE2BIL, AdDeltafiberIL, and AdTL. AdDeltafiberIL and the parental virus, Ad5-Delta24, resulted in similar cytotoxicity, but AdDeltaE2BIL and AdDeltaE1AIL were slightly attenuated. Disruption of the expression of neighboring viral genes by insertion of the transgene was minimal for AdDeltaE2BIL and AdDeltafiberIL, but substantial for AdDeltaE1AIL. Our observations suggest that insertion of IRES-transgene cassettes into viral transcription units is an attractive strategy for the development of armed oncolytic adenoviruses with defined kinetics and strength of transgene expression.

Construction and identification of recombinant vectors carrying herpes simplex virus thymidine kinase and cytokine genes expressed in gastric carcinoma cell line SGC7901

AIM: To construct and identify the recombinant vectors carrying herpes simplex virus thymidine kinase (HSV-TK) and tumor necrosis factor alpha (TNF-α) or interleukin-2 (IL-2) genes expressed in gastric carcinoma cell line SGC7901.

METHODS: The fragments of HSV-TK, internal ribosome entry sites (IRES) and TNF-α or IL-2 genes were inserted in a TK-IRES-TNF-α or TK-IRES-IL-2 order into pEGFP-N₃ and pLXSN to generate the therapeutic vectors pEGFP-TT, pEGFP-TI, pL(TT)SN and pL(TI)SN respectively, which were structurally confirmed by the digestion analysis of restriction endonuclease. The former two plasmids were used for the transient expression of recombinant proteins in the target cells while pL(TT)SN and pL(TI)SN were transfected into SGC7901 cells by lipofectamine for the stable expression of objective genes through G418 selection. The protein products expressed transiently and stably in SGC7901 cells by the constructed vectors were confirmed by fluorescent microscopy and Western blot respectively.

RESULTS: The inserted fragments in all constructed plasmids were structurally confirmed to be consistent with that of the published data. In the transient expression, both pEGFP-TT and pEGFP-TI were shown expressed in nearly 50% of the transfected SGC7901 cells. Similarly, the G418 selected vectors PL(TT)SN and PL(TI)SN were confirmed to be successful in the stable expression of the objective proteins in the target cells.

CONCLUSION: The constructed recombinant vectors in the present study that can express the suicide gene TK in combination with cytokines genes may serve as the potential tools to perform more effective investigations in future for the gene therapy of gastric carcinoma.

Tools for targeted manipulation of the mouse genome

In the postgenomic era the mouse will be central to the challenge of ascribing a function to the 40,000 or so genes that constitute our genome. In this review, we summarize some of the classic and modern approaches that have fueled the recent dramatic explosion in mouse genetics. Together with the sequencing of the mouse genome, these tools will have a profound effect on our ability to generate new and more accurate mouse models and thus provide a powerful insight into the function of human genes during the processes of both normal development and disease.