Human gene marker/therapy clinical protocols

Ectopic expression of herpes simplex virus-thymidine kinase gene in human non-small cell lung cancer cells conferred caspase-activated apoptosis sensitized by ganciclovir

Human non-small cell lung cancer (NSCLC) cells were transfected with recombinant prodrug herpes simplex virus type I thymidine kinase (HSV-tk) cDNA, and the selected clones underwent apoptosis in response to induction by antiviral ganciclovir (GCV). The efficiency of GCV-induced growth inhibition and the extent of the bystander effect were associated with the expression level of HSV-TK in stable transfectants. Development in the HSV-tk/GCV system toward cell death was initiated with cell-cycle accumulation at S and G(2)/M phases, immediately followed by the appearance of sub-G(0)/G(1) cells after drug exposure. To investigate the regulation of cell-cycle modulators during drug treatment, we analyzed release of the apoptosis initiator cytochrome c and activation of the downstream effectors caspase-9, caspase-3 and poly(ADP-ribose)polymerase 16 hr after GCV sensitization, followed by transient escalation of tumor-suppressor p53 and cell-cycle modulators cyclin A and B(1) before committing to programmed cell death. Furthermore, tumor regression was proportional to the degree of ectopic expression of the transferred HSV-tk gene. Our results demonstrate that the HSV-tk/GCV system effectively inhibits the proliferation of NSCLC cells in vitro and in vivo through potent induction of apoptosis, thus providing a rationale for further development.

Transgene expression in neonatal mouse inner ear explants mediated by first and advanced generation adenovirus vectors

The mouse serves as a valuable model for treatment leading to the prevention and therapy of inner ear disease. Transgenic correction of genetic inner ear disease in mice may help develop treatment for human genetic inner ear disease. In mutations involving hair cells (HCs) or supporting cells (SCs), it is necessary to insert the wild-type transgenes directly into these cells. We used inner ear explants to characterize the transgenic expression using adenovirus-mediated reporter genes (bacterial lacZ). The variable parameters were the age of the explants (P1-P5), the type of vector (first and advanced generation adenovirus) and the genotype of the mouse (wild-type versus shaker-2 mutant). Transduction of cochlear HCs was detected at P1 and in some of the P3 cochleae. Low efficiency transduction of SCs was observed in P1 explants, but the efficiency increased with age and reached high levels at P5. The pattern of transduction was similar regardless of the genotype and the type of vector used. The data demonstrate that differentiating HCs and SCs in mouse explants can be transduced by adenovirus vectors, suggesting that cultures of mouse ears are a valuable model for developing inner ear gene therapy protocols.

Bystander effect of purine nucleoside analogues in HSV-1 tk suicide gene therapy is superior to that of pyrimidine nucleoside analogues

Introduction of the herpes simplex virus type 1 thymidine kinase gene into tumor cells, followed by the administration of the antiherpes nucleoside analogue ganciclovir has been demonstrated to be effective in eliminating solid tumors in animals. The success of this combination treatment largely depends on the bystander effect, i.e. the killing of nontransfected tumor cells by activated drug carried over from the nearby herpes thymidine kinase (tk) gene-transfected cells. We evaluated the in vitro bystander effect of several antiherpes purine and pyrimidine nucleoside analogues, using a colorimetric assay. All pyrimidine nucleoside analogues, including (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU), showed low, if any, bystander killing effect. In contrast, purine nucleoside analogues, such as ganciclovir, were endowed with a pronounced bystander killer effect. Lobucavir (Cyclobut-G), a ganciclovir analogue, displayed a two- to three-fold more pronounced bystander killer effect than ganciclovir, eliminating, at a concentration of 10 microM, 75% and 90% of a cell population that contained 5% and 10% tk gene-transfected cells, respectively. These findings were corroborated by autoradiographic analysis that showed that 2'-3H-BVDU metabolites formed in the herpes tk gene-transfected tumor cells were much less efficiently incorporated in the DNA of bystander cells than 8-3H-GCV. This indicates that, under the same experimental conditions, BVDU metabolites are less prone to pass the gap junctions than GCV metabolites.