Abstract P4-08-07: PIK3CA mutation, reduced AKT serine 473 phosphorylation, and increased ERα serine 167 phosphorylation are positive prognostic indicators in postmenopausal estrogen receptor-positive, HER2-negative early breast cancer

Background: Endocrine therapy is the most important treatment option for women with estrogen receptor (ER)-positive breast cancer. We recently reported that approximately two-thirds of patients who relapsed within 5 years had received anthracyclins and/or taxanes as adjuvant or neoadjuvant chemotherapy in addition to adjuvant endocrine therapy. New strategies, such as signal transduction inhibitors together with endocrine therapy are required to improve survival. PIK3CA mutations are detected in almost 40% of early ER-positive breast cancers, and are therefore the most frequent genetic alterations in this subtype. PIK3CA mutation status is reported to affect activation of AKT and ERα. Moreover, recent studies demonstrate that patients had a better prognosis when tumors expressed ER, androgen receptor (AR), and vitamin D receptor (VDR).

Methods: Expression of AR and VDR, phosphorylation of AKT serine (Ser) 473 (AKT phospho-Ser473) and ERα Ser167 (ERα phospho-Ser167) were examined by immunohistochemistry in ER-positive, HER2-negative early breast cancer tissues. Seventeen mutations in exons 1, 4, 7, 9, and 20 of the PIK3CA gene were detected in genomic DNA extracted from formalin-fixed paraffin-embedded tumor blocks. Correlations between these biological markers and clinicopathological factors and prognosis were analyzed separately in pre- and postmenopausal women.

Results: Levels of AKT phospho-Ser473 were significantly higher in premenopausal women (n = 62) than in postmenopausal women (n = 152) (P < 0.0001 and P = 0.014, respectively). In contrast, expression levels of AR were significantly higher in postmenopausal women than in premenopausal women (P < 0.0001). In premenopausal women, 26 tumors (43%) had a single mutation of PIK3CA gene, and 3 tumors (5%) had mutations at two sites. In postmenopausal women, 64 tumors (44%) had a single PIK3CA mutation, 6 tumors (4%) had mutations at two sites, and one tumor (1%) had mutations at three sites. In premenopausal women, wild type PIK3CA was associated with smaller tumor size, higher ER expression levels, and lower AR expression levels when compared with women in the same cohort with PIK3CA mutant tumors. In postmenopausal women, patients with PIK3CA wild-type tumors had higher Ki67 labeling index, higher AKT phospho-Ser473, and lower ERα phospho-Ser167 when compared to patients with PIK3CA mutant tumors. Postmenopausal women with PIK3CA wild-type tumors had significantly worse disease-free survival than patients with PIK3CA mutant tumors (P = 0.007). In contrast, PIK3CA mutation status was not correlated with survival in premenopausal women. Low levels of AKT phospho-Ser473 and high levels of ERα phospho-Ser167 were strongly associated with increased disease-free survival in postmenopausal women (P = 0.016 and P = 0.0016, respectively).

Conclusion: ERα activation, in addition to PIK3CA mutation, may be biomarkers for highly endocrine-responsive tumors. This would facilitate the selection of postmenopausal ER-positive breast cancer patients who are likely to benefit from endocrine therapy alone from those who are not.

Citation Format: Ishida N, Hatanaka Y, Baba M, Hagio K, Okada H, Hatanaka KC, Matsuno Y, Yamashita H. PIK3CA mutation, reduced AKT serine 473 phosphorylation, and increased ERα serine 167 phosphorylation are positive prognostic indicators in postmenopausal estrogen receptor-positive, HER2-negative early breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-08-07.

Test of the Brink-Axel Hypothesis for the Pygmy Dipole Resonance

The gamma strength function and level density of 1^{-} states in ^{96}Mo have been extracted from a high-resolution study of the (p[over →], p[over →]^{'}) reaction at 295 MeV and extreme forward angles. By comparison with compound nucleus γ decay experiments, this allows a test of the generalized Brink-Axel hypothesis in the energy region of the pygmy dipole resonance. The Brink-Axel hypothesis is commonly assumed in astrophysical reaction network calculations and states that the gamma strength function in nuclei is independent of the structure of the initial and final state. The present results validate the Brink-Axel hypothesis for ^{96}Mo and provide independent confirmation of the methods used to separate gamma strength function and level density in γ decay experiments.

Principal component analysis uncovers cytomegalovirus-associated NK cell activation in Ph+ leukemia patients treated with dasatinib

Dasatinib treatment markedly increases the number of large granular lymphocytes (LGLs) in a proportion of Ph⁺ leukemia patients, which associates with a better prognosis. The lymphocytosis is predominantly observed in cytomegalovirus (CMV)-seropositive patients, yet detectable CMV reactivation exists only in a small fraction of patients. Thus, etiology of the lymphocytosis still remains unclear. Here, we identified NK cells as the dominant LGLs expanding in dasatinib-treated patients, and applied principal component analysis (PCA) to an extensive panel of NK cell markers to explore underlying factors in NK cell activation. PCA displayed phenotypic divergence of NK cells that reflects CMV-associated differentiation and genetic differences, and the divergence was markedly augmented in CMV-seropositive dasatinib-treated patients. Notably, the CMV-associated highly differentiated status of NK cells was already observed at leukemia diagnosis, and was further enhanced after starting dasatinib in virtually all CMV-seropositive patients. Thus, the extensive characterization of NK cells by PCA strongly suggests that CMV is an essential factor in the NK cell activation, which progresses stepwise during leukemia and subsequent dasatinib treatment most likely by subclinical CMV reactivation. This study provides a rationale for the exploitation of CMV-associated NK cell activation for treatment of leukemias.