Shokrollahi, M. | Search bioRxiv

bioRxiv2024

Metabolic Vulnerabilities of Temozolomide-Resistant Glioblastoma Cells: Implications for Targeted Therapies and Overcoming Chemoresistance

Chemoresistance is a major clinical challenge in the management of glioblastoma (GB), making it difficult to achieve long-term success with traditional treatments. Therefore, there is a need for the development of novel drugs. We explored the metabolic vulnerabilities of temozolomide (TMZ)-resistant GB and their potential implications for targeted therapies. In monolayer and tumoroid cultures, we found elevated reliance on oxidative phosphorylation in TMZ-resistant cells. Notably, iron reduction in TMZ-resistant cells reduced viability and proliferation, upregulated hypoxia-inducible factor 1- (Hif1-) expression, induced autophagy, inhibited autophagic flux, and increased reactive oxygen species (ROS) generation, indicating the significance of iron in metabolic vulnerabilities of these cells. Hypoxic cells showed acquired resistance to iron chelation compared to their normoxic state, suggesting an adaptive mechanism associated to hypoxia. Viability, size, and invasion were reduced in TMZ-resistant tumoroids. Additionally, we reported IC50 for the combination of TMZ with a range of DFO and DFP, making the combination therapy a promising drug candidate to improve therapeutic treatments. TeaserCombining iron reduction and chemotherapy in drug-resistant glioblastoma cells enhances therapeutic outcomes.

cancer biology↗

bioRxiv2023

DNA double-strand break-capturing nuclear envelope tubules drive DNA repair

The nuclear envelope is a membrane separating nuclear from cytoplasmic processes. Existing models suggest that damaged DNA moves to the envelope at the edge of the nucleus for repair. Yet, most damaged human DNA does not reposition to the nuclear periphery during repair. Here we show that human cells relocate the nuclear envelope to non-peripheral damaged DNA, providing solid support promoting the reconnection of DNA break ends. Upon DNA double-strand break (DSB) induction, cytoplasmic microtubules poke the nuclear envelope inwards, inducing an extensive network of DSB-capturing nuclear envelope tubules (dsbNETs). The formation of dsbNETs, which encompass the nuclear lamina and the inner and outer nuclear membranes, depends on DNA damage response kinases, dynamic microtubules, the linker of the nucleoskeleton and cytoskeleton (LINC) proteins SUN1 and SUN2, nuclear pore protein NUP153, and kinesin KIF5B. Repressing dsbNETs compromises the reassociation of DSB ends. The timely reversal of dsbNETs by the kinesin KIFC3 also promotes repair. DSB ends reconnection is restored in dsbNETs-deficient cells by enlarging the 53BP1 DNA repair center. The lamina-binding domain of SUN1 mediates its entry into the tubules and DSB capture by the envelope. Fusing truncated SUN1 to the NHEJ repair protein KU70 fails to localize SUN1 to the tubules but rescues DSB targeting only to the boundary envelope. Although dsbNETs typically promote accurate DSB repair and cell survival, they are co-opted by the PARP inhibitor olaparib to induce aberrant chromosomes restraining BRCA1-deficient breast cancer cells. We uncover dsbNETs, which bring the nuclear envelope to DSBs for repair and potentiate the efficacy of anti-cancer agents. Our findings revise theories of the structure-function relationship of the nuclear envelope and identify dsbNETs as a critical factor in DNA repair and nuclear organization, with implications for health and disease.

molecular biology↗