Abstract PO2-24-02: Molecular characterization of primary tumors associated with various CTCs’ subpopulation

Abstract Background: Circulating tumor cells (CTCs) are prognostic in primary breast cancer (BC) patients and represent a heterogeneous population of cells with different phenotypes and biological value. However, molecular characterization of primary tumors associated with various CTCs’ subpopulation is lacking. This study aimed to identify expression of genes associated with the presence of different CTCs subpopulations in primary BC patients using a comprehensive genomics approach. Methods: This prospective ongoing study included 312 patients (pts) with non-metastatic BC enrolled from March 2012 to February 2015. CTCs were detected on day -1 to 0 before surgery. Isolated peripheral blood mononuclear cells (PBMC) were depleted of hematopoietic cells using RossetteSepTM kit negative selection with anti-CD45 antibody. RNA extracted from CD45-depleted (CD45-) PBMC was interrogated for expression of EMT-inducing transcription factors (TWIST1, SNAIL1, SLUG, ZEB1) and epithelial (CK19) gene transcripts by quantitative reverse transcription-PCR. Expressions of gene transcripts in CD45- PBMC of patients were compared to those of CD45- PBMC of 60 healthy donors. Formalin-fixed paraffin-embedded tumor tissue was subject for gene expression analysis performed by HTG EdgeSeq Oncology Biomarker panel (HTG Molecular Diagnostics, Inc. , Tucson, USA). Results: CTCs with epithelial phenotype (CTCEP) were detected in 30 (9. 6%) pts, CTC with EMT (epithelial-to-mesenchymal transition) were detected in 54 (17. 3%), while blood of 79 (25. 3%) pts exhibit at least one type of CTC. Patients with detectable CTC in peripheral blood had inferior disease-free survival compared to patients without detectable CTC (HR = 0. 62, 95% CI 0. 37-1. 06, P=0. 048). There was no association between epithelial CTCs and analysed patients/tumour variables. Genes expression analysis identified 7 differentially expressed genes in patients with the CTCEP phenotype (CHGA, MESP1, COL2A1, MT2A, COMP, MMP7 and ORM2), 200 genes associated with CTCEMT phenotype (top 10 genes included CHGA, CECR6, SMAD2, HUS1, FGF10, HNF1A, SEC61G, CDK4, CD44 and F3). Analysis identified that low expression of CHGA and MMP7 was consistently associated with any CTC subpopulations. Conclusions: In this study for the first-time revealed gene expressions associated with various CTC subpopulations. We suppose that these genes could represent potential therapeutic target aimed to inhibit metastatic cascade in breast cancer. Citation Format: Michal Mego, Gabriel Minarik, Milan Hucko, Katarina Kalavska, Marian Karaba, Juraj Benca, Tatiana Sedlackova, Lucia Kucerova, Jozef Mardiak, Lubos Klucar, Zuzana Cierna. Molecular characterization of primary tumors associated with various CTCs’ subpopulation 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 PO2-24-02.