The killing effect on bladder cancer cell EJ in vitro by radiation-induced suicide gene therapy under the radiation of 125I

Objectives To explore a more effective approach for the treatment of bladder cancers, we designed recombinant lentivirus E8-codA-GFP, and investigate the killing effect on bladder cancer cell EJ by the recombinant gene under the radiation of radionuclide 125I.

Methods After EJ cells were infected by E8-codA-GFP LV and then exposed to 125I at the dose of 74, 55.5, 37, 17.5kBq for 48 hours, the expression of GFP gene was observed under fluorescence microscope and the ability to converting 5-fluorocytosine (5-FC) to 5-Fluorouracil (5-FU) was assayed by HPLC. In the experiment group, the cells were exposed to 125I at different dose. In 125I contrast group, the cells were exposed to 125I at different dose. And 5-FU was added to one group of the infected cells as the positive contrast. After 48 hours exposure, the survival rates were determined by MTT assay.

Results The green fluorescence was obviously observed at the dose of 55.5kBq and 74kBq, and the ultraviolet peak of 5-FU was the sharpest at the dose of 148kBq observed by HPLC. MTT colorimetric assay showed that the survival rates were (65.43±16.20)%, (67.04±10.71)%, (68.29±14.59)% and (72.57±9.29)% , respectively, for lentivirus-infected EJ cells treated with 125I at the dose of 148, 111, 74, 37 kBq and 400µg/ml 5-FC, which was lower than the 125I contrast group that was (99.33±15.64)%, (80.98±11.97)%, (97.46±6.31)% and 100% , respectively, at the dose of 148, 111, 74, 37 kBq but was higher than the positive contrast group ( the survival rate was (29.14±1.10)% ).

Conclusions The results indicate that synthetic promoter E8 can induce the expression of downstream CD gene and reporter gene after exposure of 125I and non-toxic 5-FC combined with low dosage 125I can play killing effects on infected EJ cells, which provides valuable contributions to the continued experiments on radionuclide 125I therapy combination with CD /5-FC suicide system in the therapy of tumor.