The role of serotonin and p53 status in the radiation-induced bystander effect.
OBJECTIVE
The aim of this study was to investigate the role of serotonin and protein 53 (p53) status of the cells in the radiation-induced bystander effects (RIBE).


METHODS
The radiation-induced bystander response was investigated in human MCF-7 breast cancer cells and human HCT116 colorectal cancer cells employing medium-transfer experiments and micronuclei (MN) induction as an end-point. Irradiated cell conditioned medium (ICCM) from cells exposed to α-particle or γ-radiation was filtered and transferred to unirradiated cells 2 h following irradiation. MCF-7 cells were irradiated with 0.5 Gy α-particles, while HCT116 p53(+/+) and HCT116 p53(-/-) cells were irradiated with 0.5 Gy γ-radiation.


RESULTS
Bystander MCF-7 cells, recipient of ICCM from 0.5 Gy α-particle irradiated MCF-7 cells grown in high serotonin conditions showed a modest but significant increase in MN, while MCF-7 cells receiving ICCM with low serotonin levels did not show any bystander effect. Added serotonin (100 ng/ml) led to a bystander effectin HCT116 p53(-/-) cells recipient of ICCM from 0.5 Gy γ-irradiated HCT116 p53(+/+) cells, but had no effect when the ICCM was from γ-irradiated HCT116 P53(-/-) cells.


CONCLUSIONS
The results indicate that serotonin levels in the medium play a role in the RIBE and that there may be an interaction between the role of serotonin and the p53 status of the irradiated cells.
Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway. erta.kalanxhi@rr-research.no
Erta
E
Kalanxhi
Jostein
J
Dahle
D024201:Bystander Effect / Q000187:drug effects* / Q000528:radiation effects*; D003470:Culture Media / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005720:Gamma Rays; D045325:HCT116 Cells; D006801:Humans; D061986:MCF-7 Cells; D012701:Serotonin / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000378:metabolism*
D003470:Culture Media; D016159:Tumor Suppressor Protein p53; D012701:Serotonin