No abstract

No abstract

No abstract

Background. Herpes simplex thymidine kinase (HTK) is known to phosphorylate ganciclovir (GCV). Phosphorylated GCV is incorporated into genomic DNA, which leads to inhibition of cell growth and cell death in the replicating cells. Recently, much attention has been drawn to the use of retrovirally mediated gene therapy using HTK as a new therapeutic approach for brain tumors. However, little is known about this phenomenon in gastrointestinal carcinomas. Methods. The authors transfected the HTK gene packaged in retroviral vector into TMK‐1 gastric carcinoma cells (TMK‐HTK cells). Sensitivity of TMK‐HTK cells to GCV was examined in vitro. Moreover, TMK‐HTK cells were transduced into nude mice subcutaneously, and the effects of GCV therapy was examined at the concentration of 20 mg/kg daily for 14 days. Results. TMK‐HTK cells were sensitive to GCV at the concentration of 0.1 to 100 μg/ml in a dose‐ and time‐dependent manner in vitro. Moreover, 12 of 13 TMK‐HTK tumors, which were transduced into nude mice subcutaneously, shrunk from the average diameter of 6.5 mm. Conclusion, The results indicate that retrovirally transmitted gene therapy with GCV may provide a new therapeutic approach for treatment of gastric carcinomas. Cancer 1995;75:1467‐71.

Previous studies demonstrated that the Ras suppressor, RSU-1, localizes to human chromosome 10p13, a region frequently deleted in high grade gliomas, and that RSU-1 expression inhibited the tumorigenesis of a glioblastoma cell line. We have now examined RNA from human glial tumors for RSU-1 expression by RT-PCR using primers for the 5' and 3' ends of the RSU-1 open reading frame. Analysis of the amplified RSU-1 cDNA demonstrated that in addition to the entire 858 bp RSU-1 open reading frame, a shorter 725 bp RSU-1 fragment was amplified as well. Sequencing of this product revealed that it encoded a RSU-1 cDNA product which was missing a single 133 bp internal exon. This exon-deleted product was found in 30% of the high grade gliomas studied and 2/3 oligodendrogliomas, but not in other CNS tumors, bladder or colon tumors or normal tissue. The exon-deleted RSU-1 product was infrequently detected in RNA from human tumor cell lines. Expression of an HA-tagged form of the deleted RSU-1 protein in transfected Cos 1 cells revealed that the protein was unstable, with a half life of less than 1 h, in contrast to the full length HA-tagged Rsu-1 protein which was stable for more than 4 h. These results suggest that the alternative splicing of the RSU-1 RNA to produce the exon-deleted form constitutes a mechanism for reduction or loss of functional Rsu-1. Because the expression of Rsu-1 can inhibit malignant growth of glioblastoma cells, the depletion of Rsu-1, via the production of the alternatively spliced form of RSU-1, may inhibit growth regulation in tumors.