Abstract [Background] A cancer stem cell (cancer initiating cell, CSC) is considered capable of self -replication, self-differentiation, drug resistance, and immune evasion. Recently, CSC has become increasingly important in the treatment of malignant tumors. Cancer stem cells express specific molecules termed CSC marker, including aldehyde dehydrogenase (ALDH) 1, B lymphoma Mo-MLV insertion region 1 homolog (Bmi-1) and CD24, and their expression has been reported to be the potential prognostic values. However, the prognostic values of ALDH1, Bmi1, and CD24 expression in patients with oral cancer are less understood. [Purpose] The aims of present study were to evaluate the expression of ALDH1, Bmi1, and CD24 in oral squamous cell carcinoma (OSCC) and to elucidate the relationships among the CSC marker expression, clinical stages, histological differentiation, the classification of invasion mode, cerebral lymph node metastasis and disease-free survival rate. [Materials and Methods] Tissue specimens were obtains from 103 patients with OSCC after surgery or biopsy. Immunohistochemistry was used to assess ALDH1, Bmi1, and CD24 protein using at least 10% staining-positive cells as the definition of positive staining. [Results] Immunohistochemical analysis of 103 cases showed that 31 cases (30%) expressed ALDH1. There was no relationship between ALDH1 expression and clinical stages or metastasis. However, there was significant association between ALDH1 expression and histological differentiation, or classification of invasion mode or disease-free survival rate. Otherwise, 39 cases (38%) cases of 103 OSCC patients expressed Bmi-1. There was significant association between Bmi-1 expression and invasion mode or disease-free survival rate. Sixty four cases (62%) expressed CD24. There was significant association between CD24 expression and histological differentiation. [Conclusions] These findings suggested that the expression of ALDH1 and Bmi-1 as CSC markers in OSCC may be good marker indicating survival in patients with OSCC. Citation Format: Tetsuya Tamatani, Natsumi Takamaru, Kenji Fujisawa, Hirokazu Nagai, Youji Miyamoto. Expression of ALDH1, Bmi-1 and CD24 in human oral squamous cell carcinoma and its relationship with clinical factors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3358.