Thesis presented March 27, 2023

Abstract:
High-grade serous ovarian carcinoma (HGSOC) represents the leading cause of death from gynecologic cancer and is the fifth most deadly cancer in women. Resistance to conventional therapies and diversity of the tumor microenvironment (TME) of HGSOC contribute to patient relapse and death. Therefore, there is an important need to understand the underlying mechanisms of the development of this cancer in order to propose new targeted therapies. Prokineticin 1 (PROK1) and prokineticin 2 (PROK2) are two secreted multifunctional proteins that act via two G-protein coupled receptors, PROKR1 and PROKR2. PROKs are involved in several processes such as angiogenesis and inflammation, and have been shown to be associated with the development of several cancers. While the role of PROK1 and its receptors is well established in ovarian physiology, its involvement in HGSOC remains controversial. The objective of my thesis was to characterize the role of PROK1 and PROK2 ligands and their receptors in HGSOC by three complementary approaches. First, a clinical approach that used two distinctive cohorts of patients with HGSOC. These cohorts served to characterize the expression of the ligands, PROK1 and PROK2 in the serum and in ascites fluid and established their patterns in the tumor’s tissues, as well as those of their receptors. Second, an in vitro approach used three ovarian cancer (OC) cell lines, SKOV3, OVCAR8 and ID8, in 2D and 3D culture systems to analyze the impact of PROK1 and PROK2 on main tumorigenesis processes. Finally, an in vivo approach with the development of a syngeneic mouse model of OC to test the effect of the PROKR1-preferential antagonist, PC-1. Our study demonstrated that the prokineticin system is highly dysregulated and increased in HGSOC, both in its circulating levels and locally within the tumor tissue. In vitro experiments demonstrated that the PROK1 ligand inhibits SKOV3 cells growth in a 3D culture system, suggesting a tumor suppressor effect. Immunohistochemical evaluation of tumor samples revealed strong differential patterns for the ligands and their receptors. Indeed, PROK1 and PROK2 were expressed by both cancer cells and immune cells, with PROK2 being the main ligand found in tumor cells. PROKR1 and PROKR2 were both expressed by tumors, however, only PROKR1 was highly expressed by infiltrating neutrophils and in adjacent tissue. Treatment of mice with the PC-1 antagonist increased the number of tumor nodules present on the surface of the peritoneum, compared to control mice, and caused significant splenomegaly, a poor prognostic sign in OC. In conclusion, my thesis project has improved our understanding of the involvement of prokineticins members in the growth and dissemination of HGSOC and is providing strong evidence of their relevance for future investigations. The concomitant study of the role of ligands and their receptors in the same cohorts, tumor cells and animal models provide a comprehensive and integrated view of the role of this protein’s family in HGSOC. In addition, I wrote a review on the involvement of prokineticins in reproductive cancers, and the different possible targeted therapies.

Keywords:
Prokineticin signaling, HGSOC, PC-1, neutrophils, tumor microenvironment