Dexamethasone modulates the radiotherapeutic effect of labeled iodo-ancitabine in solid tumor bearing mice

Ancitabine is one of the potent chemotherapeutic anticancer drugs. iodoancitabine (125I-ANC) was prepared by electrophilic substitution using iodogen as an oxidizing agent which produce yield above 90 % at ph 7 with heating on a water bath to 65 degree C within 10 min as reaction time. The labeled drug was stable for 48 h post labeling . Biodistribution study of 125I-ANC in normal mice reflected that its uptake was increased in organ of high proliferation like stomach. In solid tumor bearing mice 125I-ANC was incorporated rapidly in tumor site and declined slowly, while declined rapidly from other tissues like blood. The therapeutic activity of 125I-ANC was significantly increased with the increase of radioactivity by decreasing the percent viability when examined on EAC cells. Significant increase in the percent survival was observed by locoregional administration (intramuscular in the inoculated thigh) than in the control. Also, starting treatment at the third day was the best day to start treatment . Furthermore,125I-ANC has been showed significant decrease in the size of the tumor treated leg when compared to the control tumor one. Mice received dexamethasone (DEX) showed significant increase in the uptake of 125I-ANC in tumor site. Radiotherapy using DEX produced significant decrease in the size of tumor especially when mice received DEX 10 days before inoculation.