Notably, SOX6 protein expression was significantly positively correlated with the speed of tumor growth and Ki67 immunoreactivity in EwS patient-derived xenograft (PDX) models (Fig. 3h), in which we observed a broad range of SOX6 expression levels similar to that in primary EwS tumors (Fig. 1a, b). The gene discussed is MKI67; the disease is neoplasm.