Likewise, we hypothesized here that the PP2A status of the endometrial tumor, should be an important additional stratification marker for testing these targeted kinase inhibitors, given that PP2A mainly acts as a negative regulator of PI3K and HER2 downstream signaling, and hence its functional or dysfunctional state could co-determine kinase inhibitor therapy outcome. The gene discussed is PIK3CA; the disease is endometrium neoplasm.