Development of recombinant opcml tumour suppressor protein as a therapy in ovarian cancer

Ovarian cancer is the leading cause of death for gynaecological malignancies. Despite the recent introduction of new successful therapeutics such as PARP inhibitors, the mortality rate for ovarian cancer remains high, highlighting the need for new treatments. In over 80% of ovarian cancers, OPCML is silenced by loss of heterozygosity and epigenetic mechanisms. OPCML is a highly conserved glycosylphosphatidylinositol (GPI)-anchored protein that exhibits tumour-suppressive properties across various cancer types (e.g., ovarian and lung cancer), likely due to its inhibitory effects on specific receptor tyrosine kinases (RTKs), including HER2 and AXL. Given OPCML's localization on the plasma membrane and its proposed mechanism of action at the external leaflet, we postulate that a targeted protein therapy delivering recombinant OPCML directly to the cell surface could serve as an effective anti-cancer treatment strategy. Here, I produced a soluble form of recombinant OPCML (rOPCML) and an Fc-fusion derivate (rOPCML-Fc) in HEK-293 cells. rOPCML +/- Fc effects were tested in ovarian cancer cell lines, lung cancer cell lines and cancer cells from ascites-derived spheroids of an ovarian cancer patient. The results show that rOPCML +/- Fc treatment induces tumour-suppressive effects comparable to ectopic OPCML expression. Mechanistically, the treatment effectively inhibited the activation of the AXL and HER2, along with the downstream phosphorylation of effector proteins AKT and ERK1/2. Consequently, this significantly reduced cell viability, colony formation capacity, migration, and invasion while promoting apoptosis. Furthermore, an extensive PamGene kinase activity assay demonstrated that rOPCML treatment inhibits the phosphorylation of other RTKs and downstream pathway effectors involved in ovarian cancer survival and invasiveness. In conclusion, rOPCML +/- Fc demonstrates significant tumour-suppressive effects, paving the way for a novel therapeutic approach for ovarian and other cancers that could be administered systemically or delivered to the tumour sites (e.g., intraperitoneally during peritoneal washing).