Expression and Clinical Significance of Cytochrome 1B1 in Bone Sarcomas

Background/Objectives: Cytochrome 1B1 (CYP1B1) is overexpressed in several cancers, contributing to carcinogenesis, cancer progression, and chemoresistance. Despite its known oncogenic role, its expression in bone sarcomas remains unknown. Methods: This study assessed CYP1B1 expression in osteosarcoma and chondrosarcoma using immunohistochemistry on tissue microarrays and analyzed corresponding transcriptomic profiles from public RNA-seq datasets. Associations with clinicopathological features, survival, drug sensitivity, and protein-protein interaction networks were also investigated. Results: CYP1B1 was overexpressed in 72.3% of bone sarcomas (78% of osteosarcomas and 82.1% of chondrosarcomas) and was significantly underexpressed in normal bone (12.5%, p < 0.001). Importantly, high CYP1B1 expression was found in younger patients (≤34 years; p = 0.013), but no other associations with tumor grade, size, or metastasis were observed. The mean survival rate of CYP1B1-positive patients was insignificantly shorter than that of negative patients (58.8 vs. 62.8 months; p = 0.170). Although not confirmed in the multivariate analysis, CYP1B1-positive patients had poorer survival in the univariate analysis, which may reflect tumor aggressiveness rather than prognostic value. Transcriptomic data showed significantly lower CYP1B1 mRNA in osteosarcoma versus normal bone, suggesting post-transcriptional or translational regulation. Drug sensitivity analysis revealed both positive and negative correlations between CYP1B1 expression and response to various compounds in the GDSC dataset, highlighting potential therapeutic implications. Conclusions: Despite low mRNA levels, CYP1B1 protein is consistently and selectively overexpressed in bone sarcomas, particularly in younger patients. While not prognostic, its expression profile warrants further investigation and evaluation as a therapeutic target or diagnostic biomarker, especially in refractory or advanced cases.