Abstract 2386: Amphiregulin confers trastuzumab resistance by activating PI3K/Akt pathway in HER2-positive breast cancer.

Abstract

Abstract Background: Amphiregulin is a ligand for the epidermal growth factor receptor (EGFR). Human epidermal growth factor receptor 2 (HER2) shares common signal pathways and forms a heterodimer with EGFR. In this study, we investigated the effect of amphiregulin on trastuzumab therapy in HER2-positive breast cancer. Methods: We analyzed serum amphiregulin levels by enzyme-linked immunosorbent assay (ELISA) from baseline serum samples obtained from HER2-positive metastatic breast cancer patients who received first-line trastuzumab plus taxane chemotherapy. In addition, in vitro experiments were performed to elucidate the biologic mechanism of clinical findings related to amphiregulin using SK-BR-3 and BT-474 cell lines. Results: Between October 2004 and July 2009, a total of 50 women with HER2-positive metastatic breast cancer were consecutively enrolled. The median age was 47 years (range, 27-72 years). Eighteen patients (36.0%) received weekly paclitaxel plus trastuzumab, 24 patients (48.0%) tri-weekly paclitaxel plus trastuzumab, and 8 patients (16.0%) tri-weekly docetaxel plus trastuzumab. Among 43 patients with measurable lesions, the response rate (RR) was 76.7%. The median follow-up duration was 29.2 months (range, 0.7-63.3 months). The median progression-free survival (PFS) was 17.6 months (95% confidence interval (CI), 13.4-21.9 months). The median overall survival (OS) was 47.0 months (95% CI, 35.3-58.6 months). The median serum amphiregulin level was 1.0 ng/mL with a maximum level of 4.4 ng/mL. Patients with high serum amphiregulin levels (≥0.5 ng/mL) had significantly shorter PFS (p=0.018) along with a tendency toward lower RR (p=0.237) and shorter OS (p=0.529) than the others. The in vitro colony forming assay demonstrated that the addition of amphiregulin resulted in increased proliferation of both SK-BR-3 and BT-474 cells. In addition, the anti-proliferative effect of trastuzumab was decreased in the presence of amphiregulin in both SK-BR-3 and BT-474 cells. The Western blot analysis showed that amphiregulin increased the phosphorylation of Akt and its downstream molecules in both SK-BR-3 and BT-474 cells. In addition, in the presence of amphiregulin, sustained phosphorylation of Akt and its downstream molecules was observed after trastuzumab treatment in both SK-BR-3 and BT-474 cells. Conclusions: High serum amphiregulin levels (≥0.5 ng/mL) predicted disease progression after first-line trastuzumab plus taxane chemotherapy in patients with HER2-positive metastatic breast cancer. Amphiregulin promoted the proliferation of HER2-positive breast cancer cells in vitro and induced trastuzumab resistance by activating PI3K/Akt pathway. Our results suggest that the measurement of serum amphiregulin levels by ELISA may provide additional information for the clinical outcome of trastuzumab-based chemotherapy in patients with HER2-positive breast cancer. Citation Format: Ji-Won Kim, Young Seok Joung, Ahrum Min, Hyun-Jin Nam, Jee Hyun Kim, Seock-Ah Im, Kyung-Hun Lee, Jin-Soo Kim, Tae-Yong Kim, Sae-Won Han, Yoon Kyung Jeon, Do-Youn Oh, Tae-You Kim, In Ae Park. Amphiregulin confers trastuzumab resistance by activating PI3K/Akt pathway in HER2-positive breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2386. doi:10.1158/1538-7445.AM2013-2386