RNaseH2 inhibition potentiates temozolomide response in patient derived glioblastoma cells

Glioblastoma (GBM) is the most common and lethal form of primary brain tumor, characterized by poor prognosis and limited treatment options, with a median survival of only 12 to 15 months post-diagnosis. Despite standard therapeutic protocols involving temozolomide (TMZ) and radiotherapy, effective treatment is challenging, underscoring the need to explore alternative therapeutic strategies. One promising approach is the inhibition of DNA damage response (DDR) pathways. RNaseH2, a key enzyme involved in ribonucleotide excision repair (RER), plays a critical role in maintaining genomic stability by removing ribonucleotides misincorporated into DNA. Thus, inhibition of RNaseH2 may enhance tumor mutational burden (TMB) and potentially transform immunogenically "cold" tumors into immunogenically "hot" tumors. In this study, a high-throughput screening (HTS) assay resulted in the identification of 52 potential RNaseH2 inhibitors from a library of 71227 compounds. We selected six of these inhibitors for further investigation, evaluating their effects both alone and in combination with TMZ in commercially available U87 MG wild-type and IDH1 mutant (IDH1 WT and MUT) glioma cells and patient-derived cells established from glioma organoids (GBO-PDC). This study highlights the therapeutic potential of RNaseH2 inhibition in combination with TMZ for GBM therapy, validated in patient-derived model, offering a promising avenue for treating this highly aggressive and yet uncurable cancer.