Abstract 4168: Akt pathway in human breast cancer: A comparison between estrogen positive and estrogen negative tumors using reverse phase protein array

Abstract

Abstract INTRODUCTION: Estrogen receptor status is crucial for breast cancer treatment planning. Some estrogen receptor (ER) negative tumors carry a worse prognosis and lack more specific therapies. The AKT pathway is a promising target in breast cancer and was reported hyper activated in ER- tumors cells using in vitro models. We aimed to compare the level of Akt pathway activation between ER+ and ER- tumors using frozen human breast tumor samples. METHODS: 40 cases of breast cancer (20 ER+, 20 ER-) were identified from the frozen tumor bank. Patients were between 40 and 70 years old, with Stage I or II, node negative disease. About 20.000 cells from each tumor cells were purified by laser capture microdissection (LCM) and the protein lysate applied to the Reverse Phase Protein Array (RPPA). Antibodies tested by RPPA included Src, p-Src, Akt, p-Akt Thr308, p-Akt Ser473, mTOR, p-mTOR, PDGFRα, p-PDGFRα Tyr751. We also compared these results to patient matched non-microdissected samples and to immunohistochemistry (IHQ) using digital quantification. RESULTS: 6 out of 9 antibodies showed higher mean expression in ER- negative tumors but only p-Src had statistically significant different levels (0.043). The coordinated high levels (above median) of p-Src/p-Akt/p-mTOR was observed in 1 (5%) of ER+ and in 8 (40%) of ER- tumors. All 8 cases from the ER- group were triple negative (ER-/PR-/Her2-). Correlation coeficients of LCM-RPPA samples and non-microdissected/RPPA samples varied from 0.02 to 0.47. Only p-Akt Ser473 showed a significant correlation (r=0.47, p=0.003). Correlation coeficients between LCM-RPPA and IHQ for antibodies Akt, p-Akt and mTOR were 0.03, –0.22 and 0.05, respectively. CONCLUSION: Protein quantification using LCM-RPPA in human breast tumors is feasible and can detect significant differences between ER+ and ER- tumors. Triple negative tumors showed a high Akt pathway activation profile compared to ER+ tumors. Triple negative tumors are more likely to benefit from targeted therapies directed against the Akt pathway. LCMed and non-LCMed matching samples analyzed by RPPA showed discrepant results. The same happened to the comparison between LCM-RPPA and IHQ with digital quantification. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4168. doi:1538-7445.AM2012-4168