The high mortality rate associated with chemoresistance in high-grade serous ovarian cancer (HGSOC) underscores the urgent need for effective treatment strategies. This study explores the role of estrogens in six HGSOC cell lines differing in carboplatin sensitivity, estrogen receptor expression, and the ability to convert estrone sulfate (E1S) into active estrogens. We assessed the effects of the steroid sulfatase (STS) inhibitor STX64 and the estrogen agonists equilin (EQ) and ethinylestradiol (EE2) on cell viability, cell death and migration, as well as their interaction with carboplatin. STX64 IC