Abstract 1229: miRNA and response to trastuzumab

Abstract The implementation of trastuzumab has revolutionized the clinical management of HER2 positive breast cancers. Unfortunately, 50% of patients are resistant to the treatment. Researchers have already designed alternative anti-HER2 agents, such as pertuzumab and lapatinib. Still, predicting which patients will benefit from the therapy would prevent overtreatment and avoid unnecessary risks of side effects. MiRNAs are small non-coding RNAs involved in post-transcriptional gene regulation, and participate in almost all biological processes, including cancer. Since aberrant miRNA levels can be detected both at tissue level and in the circulation, they are good candidates as predictive and prognostic biomarkers. This study had access to tumor tissue samples from the phase III NeoALTTO trial, aimed at evaluating the efficacy of a HER2 dual blockade with trastuzumab and Lapatinib vs single blocking, in concomitance with chemotherapy, in a pre-operative setting. The primary end-point of the study was pathologic complete response (pCR); the secondary end-point event-free survival (EFS). Focusing on the trastuzumab arm, we identified both a predictive signature (hsa-miR-31-3p, OR 0.70, 95%CI: 0.53-0.92 and hsa-miR-382-3p, OR 1.39, 95%CI: 1.01-1.91) with an AUC value of 0.73 (95%CI: 0.60-0.87), and a prognostic signature (miR-153-3p, HR 1.83, 95%CI: 1.34-2.50 and miR-219a-5p, HR 0.629, 95%CI: 0.51-0.79) leading to a C-statistics of 0.730 (95%CI: 0.63-0.83). Moreover, we identified 2 miRNAs (miR-215-5p and miR-30c-2-3p) associated to EFS with a statistically significant interaction term with pCR (p.interaction: 0.017 and 0.038, respectively). Aiming at deepening the understanding of resistance mechanism, we modulated the expression of miR-31-3p and miR-382-3p in vitro, upon trastuzumab treatment in HER2 positive breast cancer cell lines. Given that miR-31-3p negatively correlates with pCR, we transfected it in HER2-addicted SKBr3 cells to appreciate a possible gain of resistance to trastuzumab; conversely, miR-382-3p positively correlates with pCR and was transfected in HER2 non-addicted HCC1954 cells. Western blot analysis of HER2 signaling pathway highlighted that overexpression of miR-31-3p was able to counteract the reduction of phosphorylated HER2 levels induced by trastuzumab treatment in SKBR3 cells compared to control. Interestingly, miR-31-3p upmodulation increased the proliferation of both treated and non-treated SKBr3 cell in a 3D setting. Conversely, miR-382-3p overexpression in HCC1954 cells only slightly increased responsiveness to trastuzumab in the 3D setting, compared to control. Trastuzumab efficacy also relies on the immune system reaction, thus, in vivo experiments will likely provide further insights into the mechanism of action of these miRNAs. Citation Format: Giulia Cosentino, Sara Pizzamiglio, Chiara M. Ciniselli, Loris De Cecco, Alessandra Cataldo, Ilaria Plantamura, Tiziana Triulzi, Sarra El-abed, Yingbo Wang, Mohammed Bajji, Paolo Nuciforo, Jens Huober, Susan L. Ellard, David L. Rimm, Andrea Gombos, Mariagrazia Daidone, Paolo Verderio, Elda Tagliabue, Serena Di Cosimo, Marilena V. Iorio. miRNA and response to trastuzumab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1229.