Melanoma bone metastasis-induced osteocyte ferroptosis via the HIF1a-HMOX1 axis.

Osteocytes are the main cells in mineralized bone tissue. Elevated osteocyte apoptosis has been observed in lytic bone lesions of patients with multiple myeloma. However, their precise contribution to bone metastasis remains unclear.Here, we investigated the pathogenic mechanisms driving melanoma-induced osteocyte death. Both in vivo models and in vitro assays were combined with untargeted RNA sequencing approaches to explore the pathways governing melanoma-induced osteocyte death. We could show that ferroptosis is the primary mechanism behind osteocyte death in the context of melanoma bone metastasis. HMOX1 was identified as a crucial regulatory factor in this process, directly involved in inducing ferroptosis and affecting osteocyte viability. We uncover a non-canonical pathway that involves excessive autophagy-mediated ferritin degradation, highlighting the complex relationship between autophagy and ferroptosis in melanoma-induced osteocyte death. In addition, HIF1a pathway was shown as an upstream regulator, providing a potential target for modulating HMOX1 expression and influencing autophagy-dependent ferroptosis. In conclusion, our study provides insight into the pathogenic mechanisms of osteocyte death induced by melanoma bone metastasis, with a specific focus on ferroptosis and its regulation. This would enhance our comprehension of melanoma-induced osteocyte death. Overall design: The injection of B16F10 melanoma cells was performed intracardially by administering 1x10^5 cells in a 100 µl volume after inducing anesthesia with isoflurane (Abbott; IsoFlo®, Cat. #05260-05), following established protocols. Mice without tumors received PBS injections as controls and were continuously monitored for 24 hours. The treatment group received B16F10 melanoma cells injected as previously described. Subsequently, daily intraperitoneal injections of Zinc Protoporphyrin (Znpp, 10 mg/kg) (MedChemExpress, Cat. # HY-101193), and Roxadustat (10 mg/kg) (Invivochem, Cat.# V0293-500mg) were administered for 13 consecutive days. The control group received an equal volume of DMSO in PBS.