PTEN Depletion Increases Radiosensitivity in Response to Ataxia Telangiectasia-Related-3 (ATR) Inhibition in Non-Small Cell Lung Cancer (NSCLC)
Radiotherapy (RT) is a crucial approach for treating non-small cell lung cancer (NSCLC), but managing local recurrence in advanced-stage cases remains difficult. Loss of the PTEN gene has been linked to resistance to radiotherapy. This study aimed to evaluate the effectiveness of combining RT with ataxia telangiectasia-mutated Rad3-related (ATR) inhibition using Ceralasertib in NSCLC cells lacking PTEN and to examine early inflammatory responses that may signal radiation pneumonitis (RP) following this combined treatment. We used small hairpin RNA (shRNA) transfections to create PTEN-depleted models of H460 and A549 cells. The effects of Ceralasertib alone and in combination with RT were tested both in vitro and in vivo. Immune cell infiltration in RP-susceptible C3H/NeJ mice was assessed through histological staining. Our results show that combining ATR inhibition with RT led to a significant reduction in PTEN-depleted NSCLC cells, with delayed DNA repair and decreased cell viability, as indicated by an increase in Sub G1 cells. In vivo, the combination therapy markedly inhibited the growth of H460 PTEN-depleted tumors compared to xenografts derived from H460 cells expressing PTEN. Notably, there was no substantial increase in macrophages or neutrophils, except at the four-week mark, where macrophage levels were significantly higher with the combination treatment compared to RT alone. Overall, our findings suggest that combining Ceralasertib with RT preferentially sensitizes PTEN-depleted NSCLC models in both in vitro and in vivo settings, with minimal impact on early inflammatory responses indicative of RP. These results support further investigation of ATR inhibition in conjunction with RT for NSCLC patients with PTEN mutations.