The RNA‐binding protein La/SSB associates with radiation‐induced DNA double‐strand breaks in lung cancer cell lines

Background Platinum‐based chemotherapy and radiotherapy are standard treatments for non‐small cell lung cancer, which is the commonest, most lethal cancer worldwide. As a marker of treatment‐induced cancer cell death, we have developed a radiodiagnostic imaging antibody, which binds to La/SSB. La/SSB is an essential, ubiquitous ribonuclear protein, which is over expressed in cancer and plays a role in resistance to cancer therapies. Aim In this study, we examined radiation‐induced DNA double strand breaks (DSB) in lung cancer cell lines and examined whether La/SSB associated with these DSB. Method Three lung cancer lines (A549, H460 and LL2) were irradiated with different X‐ray doses or X‐radiated with a 5 Gy dose and examined at different time‐points post‐irradiation for DNA DSB in the form of γ‐H2AX and Rad51 foci. Using fluorescence microscopy, we examined whether La/SSB and γ‐H2AX co‐localise and performed proximity ligation assay (PLA) and co‐immunoprecipitation to confirm the interaction of these proteins. Results We found that the radio‐resistant A549 cell line compared to the radio‐sensitive H460 cell line showed faster resolution of radiation‐induced γ‐H2AX foci over time. Conversely, we found more co‐localised γ‐H2AX and La/SSB foci by PLA in irradiated A549 cells. Conclusion The co‐localisation of La/SSB with radiation‐induced DNA breaks suggests a role of La/SSB in DNA repair, however further experimentation is required to validate this.