Xanthohumol regulates miR-4749-5p-inhibited RFC2 signaling in enhancing temozolomide cytotoxicity to glioblastoma.

Aims: Xanthohumol (XN), a natural prenylated flavonoid isolated from Humulus lupulus L. (hops), possess the therapeutic effects in glioblastoma multiforme (GBM), which is a grade IV aggressive glioma in adults. However, low bioavailability and extractive yield limit the clinical applications of XN. To comprehensively investigate XN-mediated gene networks in inducing cell death is helpful for drug development and cancer research. Therefore, we aim to identify the detailed molecular mechanisms of XN's effects on exhibiting cytotoxicity for GBM therapy.

Methods And Key Findings: XN significantly induced GBM cell death and enhanced temozolomide (TMZ) cytotoxicity, a first-line therapeutic drug of GBM. XN-mediated transcriptome profiles and canonical pathways were identified. DNA repair signaling, a well-established mechanism against TMZ cytotoxicity, was significantly correlated with XN-downregulated genes. Replication factor C subunit 2 (RFC2), a DNA repair-related gene, was obviously downregulated in XN-treated cells. Higher RFC2 levels which occupied poor patient survival were also observed in high grade GBM patients and tumors. Inhibition of RFC2 reduced cell viability, induced cell apoptosis, and enhanced both XN and TMZ cytotoxicity. By intersecting array data, bioinformatic prediction, and in vitro experiments, microRNA (miR)-4749-5p, a XN-upregulated microRNA, was identified to target to RFC2 3'UTR and inhibited RFC2 expression. A negative correlation existed between miR-4749-5p and RFC2 in GBM patients. Overexpression of miR-4749-5p significantly promoted XN- and TMZ-mediated cytotoxicity, and reduced RFC2 levels.

Significance: Consequently, we suggest that miR-4749-5p targeting RFC2 signaling participates in XN-enhanced TMZ cytotoxicity of GBM. Our findings provide new potential therapeutic directions for future GBM therapy.