lncRNA LUCAT1 regulates DNA damage response in glioma stem cells under hypoxia

BACKGROUND: Genomic stability is essential for cell survival, particularly under stress conditions like hypoxia, which disrupt DNA repair. Glioblastoma (GBM) is markedly resistant to DNA-damaging therapies, primarily due to glioma stem cells (GSCs) and the hypoxic tumor microenvironment. Long non-coding RNAs (lncRNAs) play a significant role in maintaining genome integrity, but their involvement in the DNA damage response (DDR) under hypoxic conditions in GSCs remains unclear. We previously identified LUCAT1 as the most highly induced lncRNA in GSCs under hypoxia and a key regulator HIF1α activity. We now investigate its role in DDR regulation. METHODS: LUCAT1-interacting proteins in GSCs under hypoxia were identified using identification of direct RNA interacting proteins (iDRIP) and mass spectrometry. Interactions were confirmed by RNA pulldown and RNA -immunoprecipitation. Mechanistic studies involved immunoprecipitation, proximity ligation assays, comet assays, immunostaining, and LUCAT1 knockdown using shRNA. Gene expression changes were evaluated via RNAseq in GSCs and TCGA datasets. Functional assays were conducted in GSCs and orthotopic xenografts with LUCAT1 depletion alone or in combination with PARP or DNA-PK inhibition or radiation. RESULTS: LUCAT1 directly interacts with the DNA-PK holoenzyme, modulating its assembly and function in the non-homologous end joining (NHEJ) pathway. It also regulates BRCA1 and RAD51, key proteins in homologous recombination (HR). Depletion of LUCAT1 increased DNA damage, sensitized GSCs to DDR inhibitors, and improved survival in mice treated with radiotherapy. CONCLUSIONS: LUCAT1 is a critical DDR regulator in GSCs under hypoxia and a promising target to enhance the -efficacy of DDR inhibitors and radiotherapy in GBM.