Effectiveness of HSV-tk suicide gene therapy driven by the Grp78 stress-inducible promoter in esophagogastric junction and gastric adenocarcinomas.
BACKGROUND
The thymidine kinase gene of the herpes simplex virus (HSV-tk) is a suicide gene when administrated with the prodrug ganciclovir (GCV). This study investigated the effectiveness of HSV-tk activation as gene therapy for gastroesophageal junction and gastric adenocarcinomas using either the stress-inducible Grp78 promoter or the murine leukemia virus long-terminal repeat (LTR) promoter.


METHODS
The HSV-tk gene, controlled by either the Grp78 promoter or the LTR promoter, was transduced into the gastroesophageal junction adenocarcinoma cell line SK-GT-5 and the gastric adenocarcinoma cell line MKN-74. Cell viability after exposure to varying concentrations of GCV was compared. The same cell lines were used to develop a nude mouse model for studies of the HSV-tk/GCV effect in vivo. The effect of intraperitoneal GCV injection on growth of the subcutaneous tumors was measured. HSV-TK expression was measured by Western blot and reverse transcription polymerase chain reaction.


RESULTS
Cell viability in vitro was significantly lower in the HSV-tk expressing (HSV-tk+) cells compared to control (no HSV-tk) cells after exposure to GCV. MKN-74tk+ cells were more sensitive to GCV killing than SK-GT-5tk+ cells. After culture with 1 microg/ml GCV for 10 days, MKN-74/tk cells were totally killed, whereas most SK-GT-5/tk cells survived. Cell viability was significantly lower under glucose starvation conditions when HSV-tk expression was regulated by the Grp78 promoter compared with the LTR promoter. MKN-74 tumors formed with HSV-tk+ cells in nude mice were eliminated after administration of GCV for 3 weeks, but GCV had no effect on tumors formed from HSV-tk- cells. Eradication of tumor formed with Grp78-tk cells was faster than that with LTR-tk cells. HSV-TK protein and mRNA were expressed in the transduced, but not the non-transduced tumors.


CONCLUSIONS
HSV-tk xwith ganciclovir suicide gene therapy results in significant cell killing in gastroesophageal junction and gastric adenocarcinoma cells both in vitro and in vivo, but complete tumor elimination only occurred with the gastric adenocarcinoma cell tumors. The most effective approach in this study used the Grp78 promoter in glucose-starvation stress conditions.
Azatian
Armen
A
Department of Surgery, University of Southern California Keck School of Medicine, Los Angeles, CA 90033, USA.
Yu
Hong
H
Dai
Wande
W
Schneiders
Fiona I
FI
Botelho
Natalia K
NK
Lord
Reginald V N
RV
D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D000091342:Endoplasmic Reticulum Chaperone BiP; D015774:Ganciclovir / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D041722:Genes, Transgenic, Suicide / Q000235:genetics*; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018139:Simplexvirus / Q000201:enzymology / Q000235:genetics; D013274:Stomach Neoplasms / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D013937:Thymidine Kinase / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
D000998:Antiviral Agents; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D013937:Thymidine Kinase; D015774:Ganciclovir