Abstract P6-08-07: Association between phenotype of triple negative breast cancer cell lines and sensitivity against eribulin mesylate in vitro
Authors: Bräutigam K , Mitzlaff K , Uebel L , Steinert G , Köster F , Polack S , Rody A , Liedtke C 
Published: May 2016

Abstract
Introduction:
Diagnosis of triple negative breast cancer (TNBC) is associated with adverse prognosis particularly in case of chemotherapy resistance. TNBC is a heterogeneous entity and seems to consist of at least six distinct molecular subtypes (Lehman subtypes) with distinct chemotherapy sensitivity. The cytotoxic agent eribulin induces tumor cell apoptosis through depolymerization of the cell spindle apparatus. Based on clinical data it has recently been suggested that TNBC is particularly sensitive against eribulin. The goal of this analysis was to compare (i) TNBC vs. non TNBC lines and (ii) cell lines of distinct TNBC subtypes with regard to eribulin sensitivity in vitro.
Methods:
17 established breast cancer cell lines comprising both TNBC (4 basal-like 1/2; 1 mesenchymal; 3 mesenchymal stem cell; 1 interleukin; 2 luminal AR; 1 unclassified) and non-TNBC (n=5) phenotypes were cultured and subjected to cell viability assay (MTT test), migration experiment (scratch assay), apoptosis analysis (Western Blot experiment for PARP cleavage) and quantitative RT-PCR analysis (for GABRP gene expression) after exposure to eribulin or control. Furthermore, gene expression of 8 genes known to induce malignant transformation (MMP7, ELF5, YBX1, RARRES1, PRNP, SOX 10, EGFR and GABRP) was analyzed via quantitative RT-PCR analysis in the triple negative cell line MDA-MB 231 after exposure to eribulin or control.
Results:
The effect of eribulin on the cell viability varied to a lesser extent among the TNBC compared to the non-TNBC cell lines though we could not observe a significant difference between both groups. Mentionable the TNBC cell line DU 4475 representing the interleukin phenotype displayed a significant stronger resistance to eribulin compared to all other phenotypes. A decelerated migration could be observed in the TNBC cell line MDA-MB 231 after exposure to the IC50 concentration of eribulin compared to non-treated cells.
Induction of apoptosis by eribulin treatment was verified by PARP cleavage in various TNBC cell lines. GABRP known to be overexpressed especially in basal like TNBC showed a slight increase in gene expression after exposure to eribulin in various phenotypes of TNBC - most prominent in MDA-MB 231. Additionally, upregulation of ELF5 and downregulation of YBX1 and PRNP, and, to a lesser extent, of MMP7 and SOX 10 gene expression could be investigated in MDA-MB 231 after eribulin treatment.
Conclusion:
We did not observe a significant association with regard to eribulin sensitivity between TNBC and non-TNBC. Chemotherapy sensitivity varied to a lesser extent among TNBC cell lines compared to non-TNBC cell lines. Eribulin inhibits cell proliferation and migration, induces apoptosis in TNBC, and influences gene expression of overexpressed genes in TNBC known to participate in and induce malignant transformation.
Though the current work did not explicitly specify one phenotype of TNBC for eribulin treatment regarding chemotherapy sensitivity, we identified possible target genes influenced by eribulin treatment, e. g. GABRP, and therefore need further investigation for a potential treatment approach combining eribulin with e. g. GABRP inhibitor.
Citation Format: Bräutigam K, Mitzlaff K, Uebel L, Steinert G, Köster F, Polack S, Rody A, Liedtke C. Association between phenotype of triple negative breast cancer cell lines and sensitivity against eribulin mesylate in vitro. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-08-07.