Abstract P6-01-14: Expression of SOX10 in invasive ductal carcinoma of the breast
Authors: Hoang Laura L , Wang Jianmin , Tacha David , Chan Huijiao , Wei Bing , Zhang Zhang , Bu Hong , Hicks David G , Tang Ping 
Published: May 2015

Abstract
Background: The transcription factor SOX10 mediates the differentiation of neural crest-derived cells, and expression of SOX10 detected by IHC analysis is primarily used to support the diagnosis of melanoma. Expression of SOX10 has been recently reported in benign breast myoepithelial cells and triple negative breast cancer. The aim of the current study is to investigate the expression pattern of SOX10 in a cohort of invasive ductal carcinoma (IDC) tumors, and analyze its relationship with different clinicopathological features and clinical outcome. Methods: Four hundred-twenty eight cases of IDC of the breast diagnosed in our institution between 1997 and 2008 and having follow-up information were included in this study. Immunohistochemical studies for SOX10 (≥1% of tumor cells having nuclear staining designated as positive expression), ER, PR, HER2 and Ki-67 were performed on 25 pre-constructed tissue microassay blocks. The relationship between SOX10 expression and the clinicopathologic features, expression of ER, PR, HER2 and Ki-67, and clinical outcome were evaluated. Results: Among this cohort of patients, the majority of them were greater than 50 years old, with grade 1 or 2 tumors that were less than 2 cm and node negative. 81% of the tumors were ER positive, 75% were PR positive and 8% HER2 positive. The overall expression rate of SOX10 was 18%; however, its expression rates were significantly higher in high grade tumors (31%), and tumors that were ER (53%) and PR (41%) negative, and tumors with high Ki-67 expression (designed as &gt;15% nuclear labeling, 47%). 51% of ER-/PR- tumors, 64% of triple negative tumors and 68% of Basal-like tumors expressed SOX10. SOX10 expression was not associated with patient age, tumor size, nodal status and over-expression of HER2. When we looked at the 4 different levels of SOX10 expression (1-25%, 26-50%. 51-75% and 76-100% of cells with positive nuclear staining) in different subgroups of breast cancer, we noted that the majority of all cases had high levels of SOX10 expression (76-100% cells with nuclear staining) regardless of their ER, PR, HER2 and Ki-67 status. No significant difference in overall survival (p value=0.8553) and disease-free survival (0.1810) between SOX10 positive and negative tumors was noted. Conclusion: Our data demonstrates a significant association between SOX10 expression and high grade, ER/PR negative, triple negative or basal-like IDC, suggesting their myoepithelial differentiation. Given that SOX10 has been recently described as a principle driver for melanoma, better understanding of SOX10 expression and signalling would provide important insight in development of novel diagnostic and therapeutic tools for SOX10 expressing tumors.
Citation Format: Laura L Hoang, Jianmin Wang, David Tacha, Huijiao Chan, Bing Wei, Zhang Zhang, Hong Bu, David G Hicks, Ping Tang. Expression of SOX10 in invasive ductal carcinoma of the breast [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-01-14.