To assess the functionality of OGT in mediating sensitivity to inhibition of PI3K by GDC-0941, we used siRNA pools targeting OGT to knockdown the expression of OGT in the GDC-0941-resistant MDA-MB-231 and OVCAR-4 tumor cell lines, and then assayed for cell proliferation and phosphorylation status of multiple signaling pathways, including downstream effectors of PI3K (Fig. 4). The gene discussed is PIK3CA; the disease is neoplasm.