Ochratoxin A drives hepatocellular carcinoma progression via GRPR-mediated activation of PLCβ/IP3R/Ca²⁺ and RPS15A/p53 pathways by regulating cancer cell fate

Ochratoxin A (OTA), a group 2B human carcinogen, has been implicated in hepatocellular carcinoma (HCC), yet its precise molecular mechanisms remain elusive. In this study, we investigated the oncogenic role of OTA using both in vitro (Huh7 and Hep-3B cell lines) and in vivo (C57BL/6 mouse models) approaches. Molecular docking, surface plasmon resonance, co-immunoprecipitation coupled with mass spectrometry (Co-IP/MS), and functional rescue experiments were employed to elucidate the underlying pathways. Our results demonstrated that OTA exposure (50 nM) significantly promoted HCC cell proliferation, migration, and invasion. Molecular docking combined with surface plasmon resonance revealed a high-affinity binding interaction between OTA and the gastrin-releasing peptide receptor (GRPR), which was subsequently validated by the observed upregulation of GRPR expression upon OTA treatment. We further demonstrated that OTA activates the canonical GRPR downstream pathway, PLCβ/IP3R/Ca^{2 +}, leading to increased intracellular calcium levels. Furthermore, Co-IP/MS identified ribosomal protein S15A (RPS15A) as a novel GRPR-interacting protein. RPS15A overexpression facilitated HCC progression by recruiting MDM2 to accelerate the degradation of p53, thereby upregulating the SLC7A11/GPX4 axis-a key regulator of ferroptosis. Crucially, GRPR knockdown effectively attenuated OTA-induced tumor growth both in vitro and in vivo. Collectively, our findings reveal a novel mechanism whereby OTA promotes HCC progression by binding to GRPR and activating both the PLCβ/IP3R/Ca²⁺ signaling cascade and the RPS15A/p53/SLC7A11/GPX4 axis, suggesting that targeting GRPR may represent a promising therapeutic strategy for OTA-associated HCC.