Ovarian cancer is characterized by poor prognosis. The disease often recurs despite aggressive treatment with surgery and chemotherapy. During the last decades, survival rates have not significantly improved, indicating the high need to unravel the molecular characteristics of ovarian cancer to constitute new therapeutic approaches. This thesis aims to increase our understanding of ovarian cancer behaviour using a novel method measuring signal transduction pathway (STP) activity. With this method, we measured the activity of six important STPs in healthy cells, precursor lesions and high-grade serous carcinoma. Ultimately, this thesis aims to improve the implementation of targeted treatment strategies for ovarian cancer patients by stratification based on STP activity.