Abstract PO3-01-01: Dysregulation of Phenylalanine-tyrosine Metabolic Signaling Pathway and Neoadjuvant Response in HER2-positive Breast Cancer
Authors: Goh Chih Wan , Xiu Bingqiu , Xue Jingyan , Chi Yayun , Wu Jiong 
Published: May 2024

Abstract
Background: Although trastuzumab and tyrosine inhibitors combined with neoadjuvant chemotherapy could significantly improve patients' pathological complete response (pCR) rate, nearly half of the patients could not achieve complete remission. Our objective was to explore the relationship between metabolic signaling pathway changes and therapeutic efficacy in patients receiving neoadjuvant therapy for HER2-positive breast cancer. Methods: Core needle biopsy specimens from HER2-positive breast cancer patients who underwent neoadjuvant therapy and radical mastectomy at Fudan University Shanghai Cancer Center between January 2017 and December 2021 were collected for RNA sequencing. According to pathological evaluation, samples (n=133) were divided into pCR and non-pCR groups. Gene differences between the two groups were further evaluated for KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis. The TCGA (The Cancer Genome Atlas, n=1091) and the HAN ethnic GEO datasets (GSE162228, GSE206, GSE48391, n=305) were used to analyze the metabolic differences between tumors and normal tissues with patients’ prognosis. Consensus clustering analysis was performed to divide patients for low and high phenylalanine-tyrosine metabolism dysregulation to analyze patients’ outcomes. The IC50 value of cell lines was tested using CCK-8 experiments. Western blot was performed to analyze the protein level changes in mTOR and glycolysis pathway. Results: We found that phenylalanine-tyrosine metabolism was significantly enriched in HER2-positive breast cancer patients. Consensus clustering analysis of TCGA and the HAN ethnic GEO datasets showed that patients with low phenylalanine-tyrosine catabolism had a significantly worse survival outcome than patients with high tyrosine metabolism (P= 0.017). In our cohort, phenylalanine-tyrosine pathway metabolic enzyme DDC was upregulated while MAOA was downregulated in non-pCR patients compared to pCR patients, suggesting the increased production of dopamine and reduced catabolism of dopamine (DA) in non-pCR tumors. In vitro experiments showed that dopamine and the knockdown of MAOA decreased cell sensitivity to pyrotinib. In addition, dopamine and clorgyline- an MAOA inhibitor, promoted the proliferation of HER2-positive cell lines under the treatment of pyrotinib. The GSEA analysis of our neoadjuvant cohort and TCGA datasets revealed that MAOA expression was associated with an inverse enrichment of the mTORC1 and glycolysis pathways. Western blot experiment results showed that dopamine or the knockdown of MAOA could activate the mTOR and glycolysis pathway Conclusions: Phenylalanine-tyrosine metabolism was significantly enriched in HER2-positive breast cancer patients. The phenylalanine-tyrosine signaling pathway may be dysregulated in HER2-positive breast cancer and patients with low phenylalanine-tyrosine catabolism have a worse prognosis. Low expression of MAOA promotes tumor resistance to HER2-targeted drugs and could serve as a therapeutic biomarker in breast cancer.
Citation Format: Chih Wan Goh, Bingqiu Xiu, Jingyan Xue, Yayun Chi, Jiong Wu. Dysregulation of Phenylalanine-tyrosine Metabolic Signaling Pathway and Neoadjuvant Response in HER2-positive Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-01-01.