DLGAP5 protects glioblastoma cells against DNA damage through E2F1-transcripted RAD51AP1

Glioblastoma multiforme (GBM) is the most prevalent primary brain tumor in adults and characterized by high therapeutic resistance and poor prognosis, in which the repair of DNA damage plays a significant role, highlighting the need to elucidate the regulatory mechanisms of DNA damage repair in GBM cells. The discs large homolog associated protein 5 (DLGAP5) is highly expressed and plays pro-tumoral activities in various cancers, however its roles in GBM remain poorly defined. Here, we report that DLGAP5 is significantly upregulated and associated with poor prognosis of GBM patients. In addition, DLGAP5 knockdown suppresses proliferation, induces apoptosis and causes DNA damage in GBM cells. Mechanistically, DLGAP5 knockdown leads to a decrease of E2F1-mediated transcription of DNA repair protein RAD51AP1, and importantly, the enforced expression of E2F1 recovers RAD51AP1 expression that largely rescues DNA damage and apoptosis of GBM cells depleted of DLGAP5. Furthermore, DLGAP5 knockdown reduces the expression of E2F1 and RAD51AP1 and induces DNA damage and suppresses tumorigenesis in xenografted GBM tumors. In conclusion, this study demonstrates that DLGAP5 protects against DNA damage in GBM cells through the E2F1/RAD51AP1 pathway, providing potential therapeutic targets in DNA damage-inducing anti-GBM modalities.