AUTHOR=Gorin Jean-Baptiste , Gouard Sébastien , Ménager Jérémie , Morgenstern Alfred , Bruchertseifer Frank , Faivre-Chauvet Alain , Guilloux Yannick , Chérel Michel , Davodeau François , Gaschet Joëlle 

TITLE=Alpha Particles Induce Autophagy in Multiple Myeloma Cells

JOURNAL=Frontiers in Medicine

VOLUME=Volume 2 - 2015

YEAR=2015

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2015.00074

DOI=10.3389/fmed.2015.00074

ISSN=2296-858X

ABSTRACT=Objectives: Radiations emitted by the radionuclides in radioimmunotherapy (RIT) approaches induce direct killing of the targeted cells as well as indirect killing through bystander effect. Our research group is dedicated to the development of α-RIT, i.e RIT using α-particles especially for the treatment of multiple myeloma (MM). γ-irradiation and β-irradiation have been shown to trigger apoptosis in tumor cells. Cell death mode induced by 213Bi α-irradiation appears more controversial. We therefore decided to investigate the effects of 213Bi on MM cell radiobiology, notably cell death mechanisms as well as tumor cell immunogenicity after irradiation.
Methods: Murine 5T33 and human LP-1 multiple myeloma (MM) cell lines were used to study the effects of such α-particles. We first examined the effects of 213Bi on proliferation rate, double strand DNA breaks, cell cycle and cell death. Then, we investigated autophagy after 213Bi irradiation. Finally, a co-culture of dendritic cells (DC) with irradiated tumour cells or their culture media was performed to test whether it would induce DC activation.
Results: We showed that 213Bi induces DNA double strand breaks, cell cycle arrest and autophagy in both cell lines but we detected only slight levels of early apoptosis within the 120 hours following irradiation in 5T33 and LP-1. Inhibition of autophagy prevented 213Bi induced inhibition of proliferation in LP-1 suggesting that this mechanism is involved in cell death after irradiation. We then assessed the immunogenicity of irradiated cells and found that irradiated LP-1 can activate DC through the secretion of soluble factor(s), however no increase in membrane or extracellular expression of danger associated molecular patterns (DAMPs) was observed after irradiation.
Conclusion: This study demonstrates that 213Bi induces mainly necrosis in MM cells, low levels of apoptosis and also autophagy that might be involved in tumor cell death.