AB053. Labeling of prostate tumor-specific replication-selective oncolytic adenoviruses with radioactive 125I: inhibitory effects on prostate cancer cell

BACKGROUND: The authors established a 125I-labeled replication-selective oncolytic adenovirus and human telomerase reverse transcriptase/prostate-specific antigen (125I-RSOAds-hTERT/PSA) oncolytic adenovirus marker and investigated the effects of different labeling conditions. This study also explored the possible mechanism whereby 125I-RSOAds-hTERT/PSA inhibited the proliferation of prostate cancer cells. METHODS: N-bromosuccinimide (NBS) was used as an oxidant for 125I labeling, and various concentrations of oncolytic viruses and NBS were prepared to determine the optimal conditions for labeling. The effects of the amount of 125I, reaction time, pH, and reaction volume on the labeling rate of the 125I-RSOAds-hTERT/PSA oncolytic adenovirus marker were measured. Radioactive oncolytic adenoviruses were isolated and purified by column chromatography; the radiochemical purities of the 125I-RSOAds-hTERT/PSA marker at different times were detected by paper chromatography. After the addition of radioactive iodine-labeled prostate cancer-specific oncolytic adenoviruses to prostate cancer cells, changes in the inhibitory rate were measured by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assays. RESULTS: The radiochemical purity of the 125I-RSOAds-hTERT/PSA marker was >95%, and the marker was stable (93–94%) after storage at 4 °C for 7 days. The optimal conditions were 0.5 µL of 125I (about 0.2 mCi, 7.4 MBq), 25 µg of NBS, 100 µL of 8×10(9) viral protein (VP)/mL 125I-RSOAds-hTERT/PSA virus solution, 3 min of reaction time, pH 7.5, and 120 µL PBS. Radioactive iodine-labeled prostate cancer-specific oncolytic adenoviruses inhibited the proliferation of prostate cancer cells significantly. CONCLUSIONS: Radioactive 125I labeling of the hTERT/PSA dual-regulated prostate cancer-specific oncolytic adenovirus is feasible, and the radiochemical purity of the marker was stable under defined conditions. Radioactive iodine-labeled prostate cancer-specific replication-selective oncolytic adenoviruses significantly inhibited prostate cell growth.