Expression of embryonic stem cell factor Sox2 in serous ovarian carcinomas

The transcription factor SOX2 is involved in the maintenance of embryonic stem cell pluripotency and is expressed in several carcinoma types, predominantly of squamous cell origin. The gene SOX2 is located at chromosome 3q26, a region that is frequently amplified in ovarian high-grade serous carcinoma.

In this study, we correlate SOX2 protein expression and gene amplification status in ovarian carcinomas with histopathological criteria and disease outcome. 215 cases of ovarian carcinomas (154 serous, 39 endometrioid, 11 clear cell, 5 mucinous and 6 transitional cell carcinomas) were analyzed by immunohistochemistry in a tissue microarray for nuclear expression of SOX2. 57% of all carcinomas showed SOX2 expression with no significant difference between the major histological types. SOX2 was detected predominantly in less differentiated tumors (G1: 36.4%, G2: 55.6%, G3: 64.0%, p=0.040). Low-level gene amplification was detected by FISH analysis in 22% of the high grade serous carcinomas and was associated with high SOX2 protein expression. Survival analysis of stage II-IV high-grade serous carcinomas revealed a favourable effect of SOX2 expression (median disease free survival 27 vs. 21 months, p=0.041; median overall survival 39 vs. 25 months, p=0.062). In summary, SOX2 is preferentially expressed in high-grade ovarian carcinomas and is associated with enhanced disease free survival. Further prospective studies are needed to explore whether SOX2 expression can be used as a marker for predicting tumor response to conventional platin-based therapies in high-grade ovarian carcinomas.