Culture slides

For laser microirradiation, cells were grown directly on culture slides (Millipore). Cells were pre-sensitized with 10 μM BrdU for 24 hours at 37 °C. Before microirradiation, media was replaced with DMEM without phenol red. Laser microirradiation was performed using MMI Cellcut Plus 355 nm Laser Capture microscope (Molecular Machines & Industries). Laser power was 50–55% of maximum to generate DNA damage restricted to the laser paths. Following damage, cells were incubated for the indicated times for recovery and processed for immunofluorescence staining and analysis.

NET (MZ-CRC-1, TT, BON-1, QGP-1) and non-cancerous cell lines (HEK-293T, WI-38) were plated on culture slides (Millipore) coated with fibronectin (Sigma Aldrich) and cultured for 48 h at 37°C. Cells were then incubated with 20 μM IR-783 for 30 min at 37°C, washed twice with PBS, and fixed with 10% formalin for 45 min at 4°C. Coverslips were mounted using Prolong-Gold w/DAPI (Invitrogen) and cured for 24 hours prior to imaging. Images were acquired using a Nikon A1 Confocal Laser Scanning Microscope (CLSM) with an Indocyanine Green filter cube and 633nm excitation laser (Figure 4).