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Global gene expression analysis of anthracycline-resistant breast cancer cell lines

ABSTRACT: Drug resistance in breast cancer is the major obstacle to a successful outcome following chemotherapy treatment. While upregulation of multidrug resistance (MDR) genes is a key component of drug resistance in multiple cancers, the complexity and hierarchy of non-MDR driven drug resistance pathways are still largely unknown. The aim of this study was to identify pathways contributing to anthracycline resistance using isogenic drug resistant breast cancer cell lines. We generated isogenic MDA-MB-231, MCF7, SKBR3 and ZR-75-1 epirubicin-resistant breast cancer cell lines, which were cross-resistant to doxorubicin and SN-38; the SKBR3 cell line was also resistant to taxanes. Epirubicin-resistant cells were morphologically different from native cells, and had alterations in apoptosis and cell cycle profile. Using gene expression and small-molecule inhibitor analyses we identified deregulation of histone H2A and H2B genes in all four cell lines. These genes contribute to several biological pathways, which include cell cycle, chromosomal maintenance, epigenetics, RNA and mitochondrial transcription. Histone deacetylase and cell cycle/DNA damage small molecule inhibitors reversed resistance and were cytotoxic for all four epirubicin-resistant cell lines confirming that histone and cell cycle pathways are associated with epirubicin resistance. This study has established model systems for investigating drug resistance in all four breast cancer subtypes and revealed key pathways that contribute to anthracycline resistance. The global gene expression analysis included 4 parental (anthracycline sensitive) and 4 resistant breast cancer cell lines, in biological triplicates.

ORGANISM(S): Homo sapiens

SUBMITTER: Braunstein Marsela

PROVIDER: S-ECPF-GEOD-54326 | biostudies-other |

REPOSITORIES: biostudies-other

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Project description:Recurrent mutations in histone modifying enzymes in multiple cancer types imply key roles in tumorigenesis. However, the functional relevance of these mutations remains unknown. Here we show that the JARID1B histone H3 lysine 4 demethylase is frequently amplified and overexpressed in luminal breast tumors and a somatic point mutation of JARID1B leads to the gain of luminal-specific gene expression programs. Downregulation of JARID1B in luminal breast cancer cells induces the expression of basal cell-specific genes and growth arrest, which is partially rescued by the inhibition of TGFBR thereby indicating a key role for TGFb signaling. Integrated genome-wide analysis of JARID1B chromatin binding, histone H3 lysine trimethyl (H3K4me3) and dimethyl (H3K4me2) patterns, and gene expression profiles in luminal and basal-like breast cancer cells suggest a key role for JARID1B in luminal cell-specific gene expression programs. A significant fraction of JARID1B binding-sites overlaps with CTCF in both luminal and basal-like breast cancer cells. CTCF also co-immunoprecipitates with JARID1B and it may influence its histone demethylase (HDM) activity as the H3K4me3/me2 ratio is lower at the CTCF-overlapping compared to JARID1B-unique sites. Additionally, a heterozygous JARID1B missense mutation (K1435R) in the HCC2157 basal-like breast cancer cell line is associated with unique JARID1B chromatin-binding and gene expression patterns implying gain of luminal features. In line with this, exogenous expression of this mutant in basal-like breast cancer cells leads to a gain of JARID1B binding at many luminal-specific genes. A PARADIGM score reflecting JARID1B activity in luminal breast cancer cells is associated with poor clinical outcome in patients with luminal breast tumors. Together, our data imply that JARID1B is a luminal lineage-driving oncogene and that its therapeutic targeting may represent a novel therapeutic strategy in treatment-resistant luminal breast tumors. RNA-Seq in breast cancer cell-lines transfected with JARID1B/CTCF/control siRNA. 50 cycles of sequencing on Illumina platform.

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Global gene expression analysis of anthracycline-resistant breast cancer cell lines

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