PIK3CA is implicated as an oncogene in ovarian cancer

Abstract

Ovarian cancer is the leading cause of death from gynecological malignancy and the fourth leading cause of cancer death among American women¹, yet little is known about its molecular aetiology. Studies using comparative genomic hybridization (CGH) have revealed several regions of recurrent, abnormal, DNA sequence copy number^2,3,4 that may encode genes involved in the genesis or progression of the disease. One region at 3q26 found to be increased in copy number in approximately 40% of ovarian² and other⁵ cancers contains PIK3CA, which encodes the p110α catalytic subunit of phosphatidylinositol 3-kinase (PI3-kinase). The association between PIK3CA copy number and PI3-kinase activity makes PIK3CA a candidate oncogene because a broad range of cancer-related functions have been associated with PI3-kinase mediated signalling⁶. These include proliferation⁷, glucose transport and catabolism⁸, cell adhesion⁹, apoptosis¹⁰, RAS signalling⁶ and oncogenic transformation^11,12,13,14. In addition, downstream effectors of PI3-kinase, AKT1 and AKT2, have been found to be amplified^15,16 or activated¹⁷ in human tumours, including ovarian cancer. We show here that PIK3CA is frequently increased in copy number in ovarian cancers, that the increased copy number is associated with increased PIK3CA transcription, p110α protein expression and PI3-kinase activity and that treatment with the PI3-kinase inhibitor LY294002 decreases proliferation and increases apoptosis. Our observations suggest PIK3CA is an oncogene that has an important role in ovarian cancer.