In vitro studies of cellular response to dna damage caused by boron neutron capture therapy (BNCT) in a recurrent thyroid carcinoma

RODRIGUEZ , C; CARPANO, M; PERONA, M; THORP, S; CUROTTO, P; POZZI, E; CASAL, MR; JUVENAL, GJ; PISAREV, MA; DAGROSA, MA

Helsinki

Congreso; 16 th Internation Congress on Boron Neutron capture therapy (BNCT).; 2014

Background: Some years ago, we started to study the effect of BNCT on DNA damage and the mechanisms of repair induced in a thyroid carcinoma. We observed different genotoxic patterns for tumor cells irradiated with gamma rays, neutrons alone and neutrons plus different boron compounds, boronophenylalanine (BPA) or a,b-dihydroxyethyl)-deutero-porphyrin IX (BOPP). In the present study we analyzed the damage profile of nuclear H2AX foci and the expression of Ku70 and Rad51, main components of non-homologous end joining (NHEJ) and homologous recombination repair (HRR) pathways, respectively, induced by BNCT in human cells of thyroid carcinoma. Methods: Cells of the human follicular thyroid carcinoma line, WRO in exponential growth were distributed into the following groups: 1) Gamma irradiation, 2) irradiation with neutrons beam (N), 3) irradiation with neutrons plus BPA (BNCT). A control group for each treatment was included. The cells were irradiated in the thermal column facility of the RA-3 reactor (Flux= 1.1010 n/cm2 sec) or with a 60Co source (1 Gy/min??) + 5%. The irradiations were performed during different lapses of time in order to obtain a total physical absorbed dose of 3 Gy (±10%). The studies after irradiation were carried out after 30 minutes, 1, 2, 4, 6, 24 and 48 hours of incubation. DNA damage was evaluated by immunofluorescence using an anti-histone H2AX phosphorylation antibody indicating double strand break in the DNA. The protein expression of Ku70 and Rad51 was analyzed by Western Blot at different times post irradiation. Results: The number of H2AX foci was higher in Gamma group after 30 minutes after the irradiation while the foci size was bigger in the BNCT group. The expression of Rad51 protein increased 4 hours after the irradiation and the levels remained high even after 48 hours in the N and BNCT groups (p