Abstract 1926: Npy1r as a prognostic marker and a novel drug target in estrogen receptor-positive breast cancer
Authors: Bhat Raksha , Vasaikar Suhas , Bae Leon , Carmine De Angelis , Cataldo Maria Letizia , Nanda Sarmistha , Zhang Bing , Schiff Rachel , Trivedi Meghana V. 
Published: August 2018

Abstract
Despite the crucial role of some G protein-coupled receptors (GPCRs) in cancer progression and metastases reported in recent studies, the function of majority of GPCRs, as a class, remains largely unexplored in breast cancer. In this study, we evaluated transcriptome, proteome and phosphoproteome data for 398 non-sensory GPCRs (IUPHAR v1.0) using the landmark TCGA breast cancer proteogenomics dataset and Illumina HiSeq dataset. Neuropeptide Y Receptor Y1 (NPY1R) was the top most hypo-phosphorylated (at S368) GPCR in 92 out of 99 evaluable samples. Furthermore, NPY1R gene expression was found to be significantly lower in tumor samples than tumor-matched normal (n=112). Among tumor samples, the LumA subtype had significantly higher NPY1R expression than LumB, Basal and Her2 subtype (p&lt;0.05, One-way ANOVA, Tukey test). Interestingly, the trend of NPY1R gene expression, protein expression and phosphosite expression was decreasing in the order of LumA, LumB, Basal and Her2 subtype (p&lt;0.01, Jonckheere trend test). Using publicly available dataset of 22,277 genes on survival in 2,422 patients, we found that higher NPY1R expression predicted better overall survival and recurrence-free survival in estrogen receptor-positive (ER+) breast cancer patients. In light of this, we interrogated NPY1R gene expression in endocrine sensitive and resistant cell line models and the impact of NPY1R antagonist in ER+ breast cancer cell lines. NPY1R expression was increased in response to estradiol in various ER+ breast cancer cell line models (MCF7, T47D, and BT474) in publicly available datasets. Conversely, we found that tamoxifen or estrogen deprivation (ED) treatment reduced NPY1R expression in MCF7 and T47D cells. In our endocrine-resistant (tamoxifen-resistant, estrogen deprivation-resistant, and fulvestrant-resistant) cell line models, NPY1R expression remained significantly lower compared to the parental cells in vitro and in vivo (p&lt;0.05, One-way ANOVA, Tukey test). Treatment of MCF7 parental cells with 100 nM NPY significantly reduced estrogen-stimulated cell growth (p&lt;0.05, One-way ANOVA, Tukey test). Chronic treatment of cells with 1 μM BIBP3226, an NPY1R antagonist, for 2 weeks reversed the effect of NPY on the estradiol-stimulated cell growth. Estradiol-stimulated cell growth was modest (~40%) in ED-resistant MCF7 cells compared to that (~250%) in parental MCF7 cells. While 100 nM NPY treatment did not affect the estrogen-stimulated growth in ED-resistant MCF7 cells, which can be explained by the undetectable expression of NPY1R, it caused significant inhibition of the estrogen-stimulated growth in the same cells treated chronically with BIBP3226. Molecular mechanisms to explain these effects of chronic NPY1R antagonism are underway. Our ongoing studies will further elucidate the role of NPY1R as a novel drug target in ER+ breast cancer.
Citation Format: Raksha Bhat, Suhas Vasaikar, Leon Bae, De Angelis Carmine, Maria Letizia Cataldo, Sarmistha Nanda, Bing Zhang, Rachel Schiff, Meghana V. Trivedi. Npy1r as a prognostic marker and a novel drug target in estrogen receptor-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1926.