PIK3CA and ovarian neoplasm: The mechanisms responsible for the acquired chemoresistance in ovarian tumors are many, including efflux pumps, repair mechanisms, signaling survival pathways (e.g., PI3K/AKT, MAPK, estrogen signaling), etc. Specifically, PARP1 inhibition causes a loss of ERK2 stimulation by decreasing the activity of critical pro-angiogenic factors, including the vascular endothelial growth factor (VEGF) and the hypoxia-inducible factor (HIF) [17].