Radiation sensitivity of prostate cancer cell lines for 177Lu, 111In, or photon irradiation

1142 Objectives Radioimmunotherapy (RIT) against prostate cancer is an evolving research area due to the absence of a curative therapy for spread disease. The purpose of this on-going study is to investigate radiation sensitivity of the three prostate cancer cell lines DU145, LNCaP, and PC3 irradiated with the β--particle emitter 177Lu, the Auger-electron emitter 111In, or by photons generated in a linear accelerator (LINAC) Methods The three prostate cancer cell lines DU145, LNCaP and PC3 were subjected to radiation using an unspecific IgG1 antibody labelled with 177Lu or 111In or by using the LINAC at 4 MV. The absorbed doses obtained by radionuclide irradiation were calculated as half the equilibrium dose. The cells were subjected to absorbed doses equal to 0, 0.5, 1, 2, 4, or 6 Gy. After irradiation, the cells were further incubated for 14 d, fixed, stained with crystal violet, and colonies were counted. Surviving fraction (SF) was defined as the number of colonies in percentage of seeded cells. The LNCaP cells were cultured in soft agar containing medium after irradiation to facilitate their ability to establish colonies. They were then treated and counted in the same way as above Results For DU145 the SF at 2.0 Gy (SF2Gy) was 0.58 ± 0.06, and 0.40 ± 0.08 (mean ± SEM) after irradiation by 177Lu or from photons from the LINAC, respectively. Irradiation using 111In is on-going. For LNCaP the SF2Gy was 0.62 ± 0.03 for the 177Lu irradiation. Irradiations using 111In or the LINAC for the LNCaP cells are on-going. Irradiations of the PC3 cells are also on-going Conclusions We see an effect of the lower dose rate for 177Lu compared to LINAC. The preliminary results indicate that the inherent radiosensitivity of prostate cancer cell lines might vary. The results will be of importance when evaluation RIT results. It will also be important to consider for future therapies using RIT, conventional radiotherapy and/or in combination with other targeted radionuclide therapies Research Support Swedish Cancer Foundat