Loss of Sox10 prevents tumor initiation in vivo and induces luminal-to-basal reprogramming in Neu+ tumor cells.

The SRY-HMG-Box transcription factor SOX10 plays a critical role in neural crest development, but its function in epithelial tumorigenesis remains unclear. Here, we identify SOX10 as a key regulator of tumor-initiating activity in Neu-driven mammary cancers. Genetic ablation of Sox10 in the luminal compartment of MMTV-Neu (NIC) mice resulted in delayed but normal mammary gland development. Sox10 deletion resulted in a reduction in mammary progenitors and a complete loss of tumor initiation in Sox10-deficient luminal cells. CRISPR/Cas9-mediated Sox10 inactivation in Neu-transformed tumor cells led to diminished self-renewal in mammosphere assays, markedly impaired growth in orthotopic transplant models and profoundly reduced lung colonization following tail vein injection, suggesting a depletion of cancer stem cell activity. Transcriptomic profiling revealed that Sox10-deficiency in Neu+ tumor cells induces a luminal-to-basal/mesenchymal-like shift and the downregulation of several genes associated with genetic networks regulating stemness. Collectively, these findings demonstrate that Sox10 is required for a permissive luminal cell state for Neu-driven tumor initiation and that it is critical for cancer stem cell activity and the establishment of metastases.