Abstract P4-02-28: EMP1 low expressing tumor is associated with cell proliferation and poor overall survival of ER-positive breast cancer patients
Authors: Ukai Junko , Tokumaru Yoshihisa , Oshi Masanori , Niwa Yoshimi , Mori Ryutaro , Takabe Kazuaki , Futamura Manabu 
Published: March 2023

Abstract
Background: Epithelial membrane protein 1 (EMP1) belongs to PMP22 gene family and is reported to be expressed low in numerous gastrointestinal cancers. However, little is known about its role in breast cancer. EMP1 functions to promote cell proliferation. In this study, we hypothesized that low EMP1 expressing breast cancer is associated with high proliferative characteristics and poor survival. Material and Methods: The clinicopathological data and transcriptome data of breast cancer patients from two independent large publicly available databases, The Cancer Genome Atlas (TCGA, n = 1090) and The Molecular Taxonomy of Breast Cancer International Consortium (METARBRIC, n = 1904), were utilized in the current study. Survival analyses; Overall survival (OS), Disease-specific survival (DSS) and Disease-free survival (DFS) were performed by comparing the high and low expression groups. CYT score, xCell, and other immunological factors were used to evaluate intratumoral immune cell composition. Also, gene set enrichment analysis (GSEA) was performed between EMP1 high and low expression groups. Results: We divided each cohort into EMP1 expression high and low groups by utilizing median cutoff. The expression levels of EMP1 were not associated with clinical stage in any subtypes. However, interestingly lower expression of EMP1 was significantly associated with more advanced grades in ER positive/HER2 negative (ER+/HER2) subtype in both TCGA and METABRIC cohorts (p&lt; 0.001 and p&lt; 0.001, respectively). Also, low EMP1 expressing tumors demonstrated higher MKI67 expression levels in ER+/HER2- subtype consistently in both TCGA (p&lt; 0.001) and METABRIC cohorts (p&lt; 0.001). Furthermore, GSEA demonstrated that low EMP1 expressing tumors enriched the gene sets associated with cell proliferation such as MYC Targets, E2F signaling, and G2M Checkpoint signaling, compared with low EMP1 expressing tumors in ER+/HER2- of both TCGA and METABRIC cohorts. On the contrary, high EMP1 expressing tumors enriched the immune related gene sets such as Coagulation, Inflammatory_Response, Complement, and IL-6_JAK_STAT3 Signaling in ER+/HER2- of both TCGA and METABRIC cohorts. To this end, we further hypothesized that high EMP1 tumors were associated with favorable tumor immune microenvironment (TIME) and analyzed TIME utilizing xCell. However, to our surprise high EMP1 expressing tumors were not associated with favorable TIME. Low EMP1 expressing tumors demonstrated worse DFS, DSS, and OS compared with high EMP1 expressing tumors in ER+/HER2- breast cancer patients (p=0.013, p=0.003, and p=0.006) which was not the case in the other subtypes in METABRIC cohort. Conclusion: Low EMP1 expressing tumors were associated with improved OS, DSS, DFS in ER-positive breast cancer patients. Also, low EMP1 expressing tumors were found to associate with advanced grades and enriched gene sets related to cell proliferation and cell cycle, which may explain the poor survival of patients with low EMP1 expressing ER+/HER2- breast cancer.
Citation Format: Junko Ukai, Yoshihisa Tokumaru, Masanori Oshi, Yoshimi Niwa, Ryutaro Mori, Kazuaki Takabe, Manabu Futamura. EMP1 low expressing tumor is associated with cell proliferation and poor overall survival of ER-positive breast cancer patients [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-02-28.