A second finding of this study was that several OCs simultaneously over-express the catalytic (PIK3CA) and the regulatory (PIK3R1) subunits of PI3K (∼57%) or present activating mutations in the gene encoding PIK3CA (∼12%), implying that the deregulated expression and/or activity of this enzyme represents a crucial oncogenic event during cancer development in the ovary. Here, PIK3R1 is linked to cancer.