SULT1A1 at a differentiation branch point regulates osteosarcoma cell proliferation and melatonin-mediated anti-tumor...

Circadian disruption is increasingly recognized as a contributing factor in tumorigenesis and tumor evolution; however, the role of circadian genes in osteosarcoma cell fate determination and therapeutic response remains to be fully elucidated.

Gene expression data from GEO were integrated to construct a prognostic model of circadian rhythm-annotated genes based on melatonin-related signatures, validated using the TARGET database. Single-cell RNA-seq and pseudotime trajectory inference were performed to characterize osteosarcoma cell states and identify branch-point genes. We queried publicly available CRISPR-Cas9 dependency data (DepMap) and performed functional assays in osteosarcoma cell lines.

A five-gene circadian rhythm-annotated prognostic signature was established and validated. The intersection of the signature with branch-point genes and circadian rhythm-annotated genes identified SULT1A1. CRISPR-Cas9 screening data confirmed that SULT1A1 is essential for osteosarcoma cell proliferation across multiple cell lines. Experimentally, SULT1A1 knockdown significantly suppressed cell proliferation and colony formation, and markedly enhanced the anti-tumor efficacy of melatonin in osteosarcoma cells.

Our findings identify SULT1A1 as a candidate circadian-associated gene localized at an osteosarcoma differentiation branch point, where it may participate in modulating cell proliferation and sensitivity to melatonin. This study uncovers a candidate mechanism potentially linking circadian gene networks to tumor cell state plasticity, with potential implications for understanding non-genetic tumor adaptation and developing chronotherapeutic strategies in osteosarcoma.