The contribution of communication between irradiated cells and between bystander cells to clonogenic survival and genomic instability

Genomic instability is observed during tumorigenic progression, in a fraction of the progeny of cells surviving irradiation, and also in unirradiated. bystander cells. It is unclear whether communication between irradiated cells themselves, or bystander cells themselves contributes to the observed effect. Herein, we restricted communication between cells by plating human lymphoblasts at low density in replicate 96 well dishes. Irradiated cells were plated before or after 0.1 Gy X-irradiation, and bystander cells were plated before or after receiving media from irradiated cells. Clonogenic survival was not affected whether cells were allowed intercellular communication (reflecting in vivo conditions) or not. Genomic instability was induced under conditions permitting intercellular communication, but not when intercellular communication was prevented. Our results imply that cell survival following irradiation or bystander conditions may not require intercellular signalling, while genomic instability might, a discrepancy that if observed at higher doses, could potentially be exploited in radiotherapy situations.