PIK3CA and malignant colon neoplasm: Consistently, immunohistochemistry staining of human colon cancer specimens showed that p85β was predominantly localized in the nuclei of tumors with a PIK3CA E545K mutation (Fig. S3g), but mostly localized in the cytoplasm of tumors with wild-type PIK3CA or a PIK3CA H1047R mutation (Fig. S3g).