Hinokiflavone, a novel CK2 inhibitor, promotes apoptosis and synergizes with chemotherapeutic agents in cisplatin-resistant bladder cancer cells.

Bladder cancer (BC) remains a major therapeutic challenge, particularly in patients with acquired resistance to platinum-based chemotherapy. In this study, we investigated the potential of hinokiflavone (HNK), a natural biflavonoid, as a therapeutic agent against cisplatin-resistant BC. Our results demonstrate that HNK differentially inhibits the proliferation of cisplatin-resistant BC cells while sparing normal uroepithelial cells. Mechanistically, HNK induces apoptosis through both intrinsic and extrinsic pathways, as evidenced by caspase activation and Annexin V staining. Next-generation sequencing and gene set enrichment analysis revealed that HNK affects genes associated with biosynthesis, metabolism, DNA replication and DNA repair. Additionally, HNK suppresses the transcription of MUTYH, OGG1, and XRCC1, key genes involved in base excision repair. We firstly identified that HNK as a novel CK2 inhibitor, and subsequent experiments confirmed that HNK inhibits CK2 activity, leading to decreased phosphorylation of Akt, Stat3, and XRCC1. The data suggest that the disruption of CK2-mediated signaling compromises BC cell survival and DNA repair capacity. Furthermore, combination treatment with HNK and chemotherapeutic agents such as doxorubicin or mitomycin C resulted in enhanced cytotoxic effects, suggesting a potential role of HNK as a chemo-sensitizing agent. These findings highlight HNK as a promising therapeutic candidate for cisplatin-resistant BC by targeting both DNA repair pathways and CK2-mediated survival signaling.