Abstract P4-04-18: High serum miR-19a levels correlated with favorable prognosis in patients with metastatic HER2+ breast cancer and might result from effective antibody-dependent cell-mediated cytotoxicity (ADCC) induced by trastuzumab and Th1-mediated antitumor immune response

Abstract

Abstract Introduction HER2 amplification is found in up to 20% of breast cancer and is associated with poor survival. To date, no predictive biomarker has been validated for clinical practice in patients with HER2+ breast cancer. Type 1 T helper lymphocytes (Th1) are required to activate antitumor cytotoxic T lymphocytes (CTL) necessary for tumor clearance. Particularly, IFN-γ secreted by Th1 cells is necessary for the development of CTL-mediated antitumor response. Trastuzumab can induce antibody-dependent cell-mediated cytotoxicity (ADCC) mediated by natural killer (NK) cells. In turn, trastuzumab-activated NK cells can trigger Th1 cells by driving their differentiation and maturation. Furthermore, NK-mediated ADCC can increase tumor cell membrane permeability through pore formation induced by perforin secreted by NK cells. We found that: 1) high serum miR-19a levels in patients with metastatic HER2+ breast cancer were predictive of favorable prognosis; 2) Th1 cells expressed and secreted high miR-19a levels; 3) and breast cancer tissue expressed higher miR-19a levels than normal adjacent tissue. Therefore, the high serum miR-19a levels in patients with good prognosis may derive from tumor cells killed by NK-mediated ADCC and secretion from Th1 cells. MiR-19a may represent a marker of effective anti-tumor immune response. Results HER2+ metastatic breast cancer patients with high serum miR-19a levels (n=27) had longer PFS (7.9 vs. 4.1 months; p=0.003) and OS (median not reached vs. 13.1 months; p<0.0001) than patients with low serum miR-19a levels (n=24). Locally advanced breast cancer tissue (n=35) expressed higher levels of miR-19a than normal adjacent tissue (n=10) (p=0.048). KPL-4 cells (HER2-amplified) expressed higher miR-19a levels than SKBR3 cells (HER2-amplified) (p=0.010) and MCF-7 cells (non-HER2-amplified, used as control) (p<0.0001). In in vitro ADCC assay, trastuzumab induced an increased tumor cell killing by NK cells and consequent miR-19a release into the supernatants of MCF-7 (p=0.004; p=0.0005), SKBR3 (p=0.001; p<0.0001) and KPL-4 (p=0.0005; p<0.0001), respectively. Th1 cells expressed (p<0.0001) and secreted (p=0.0002) higher miR-19a levels than Th2 cells (Th1 antagonist). Patients with favorable prognosis had higher levels of IFN-γ-secreting Th1 cells (p=0.049) in the peripheral blood than patients with worse prognosis. Conclusion High serum miR-19a levels in patients with metastatic HER2+ breast cancer may result from an increased ability of trastuzumab to induce an effective NK-mediated ADCC and activation of Th1-mediated immune response. This may explain the different clinical outcome between patients with high and low serum miR-19a levels. Our results suggest that miR-19a may potentially represent a novel serum biomarker to evaluate trastuzumab response and Th1-mediated anti-tumor immunity in patients with metastatic HER2+ breast cancer. Citation Format: Anfossi S, Huo L, Woodward WA, Ueno NT, Valero V, Calin GA, Reuben JM. High serum miR-19a levels correlated with favorable prognosis in patients with metastatic HER2+ breast cancer and might result from effective antibody-dependent cell-mediated cytotoxicity (ADCC) induced by trastuzumab and Th1-mediated antitumor immune response. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-04-18.