Effects of Radioprotectors on Abdominal Tissues and Malignancies Following Irradiation

Purpose: Our previous study demonstrated aminoguanidine (AG) could alleviate abdomen irradiation-induced diarrhea and mucosa damage of small bowel (NSC). In addition, AG did protect crypt cell line but not cervical cancer line after irradiation. Does AG protect tumor after irradiation in animal model? Does AG protect organs of abdomen such as liver and kidney after irradiation? What is the mechanism of AG protection? Is it the sam as known antioxidants such as amifostine (AM) and superoxide dismutase (SOD)? We are interesting in further studies. The proposal will be performed for 3 years. Materials and methods: In the first year, we will implant cancer cell lines including cancers of cervix, endometrium, ovarian, liver, and urinary bladder to SCID mice for xenograft model. We will use 6 Gy irradiation to tumor in mice. Radioprotectors such as AG 800 mg/kg (p.o. 2 hours before irradiation), AM 200 mg/kg (i.p. 15-30 minutes before irradiation), SOD mimic (i.p. 15-30 minutes before irradiation), or vehicle will be administrated to mice. We will compare tumor size and conolies of pulmonary metastasis 20 days later. mmunohistochemistry (IHC) and Western blotting will be used for analysis. In the second year, we will induce severe damage of kidney, liver or small bowel. One to three fractions of 12 Gy whole andominal irradiation (WAI) with 2-week interval will be delivered to SD rats. Serum, liver, and kidney will be sampled in different time points from 6 to 30 weeks after the last irradiation. Aminotransferase (AST), alanine aminotransferase (ALT), Alkaline phosphatase (ALP), blood urea nitrogen (BUN), creatinine (Cr), total biliruin, and direct bilirubin will be analyzed. In the small-bowel damage model, 15 GyWAI will be delivered and small bowel will be resected in different time points from 0.5 hour to 3 days after irradiation. In the third year, we will use above radioprotectors to salvage severe damage of kidney, liver or small bowel. The dose of radiation and radioprotectors will be same as the second year. SOD inhibitor (Diethyldithiocarbamate: DDC 100 mg/kg, i.p.) and p53 inhibitor (pifithrin-: PFT-2.2 mg.kg, i.p.) will be administrated 30 monutes before irradiation. We will select significant time points for analysis. We will analyze data same as the second year. Preliminary result: AM can increase survival rate from 0% to 90% following 18 Gy irradiation. DDC and PFT-can reverse the effect of AM to 0% and 20%, respectively. SOD can increase survival rate from 0% to 20% following 18 Gy irradiation. AG can increase survival rate from 0% to 10% following 18 Gy irradiation. AM can increase expression of p53 and p21 expression 4-8 hours after 18 Gy irradiation. Accordint to our preliminary result, SOD and AG have a potential radiopeotection for small bowl following medial dose of irradiation. Hence, we will choose 15 GyWAI for studies of small-bowel damage. Expected results and further prospect: Generally, radioprotectors may protect kidney, liver, and small bowel but not tumor. The mechanism of protection may be related to p53/p21 and SOD pathway. AG may be considered to use in radiotherapy of patients with abdominal malignancies.

Project ID:PC9902-1653
External Project ID:NSC98-2314-B182-032-MY2