Journal Article

Activating transcription factor-2 (ATF2) is a key determinant of resistance to endocrine treatment in an in vitro model of breast cancer

Mohhamed, Hisham, Palmieri, Carlo, Carroll, Jason S., Malki, Mohammed Imad, Rudraraju, Bharath, Menon, Suraj, Giannoudis, Athina, Liloglou, Triantafillos, Ali, Simak

2020

Overview

Background Activating transcription factor-2 (ATF2), a member of the leucine zipper family of DNA binding proteins, has been implicated as a tumour suppressor in breast cancer. However, its exact role in breast cancer endocrine resistance is still unclear. We have previously shown that silencing of ATF2 leads to a loss in the growth-inhibitory effects of tamoxifen in the oestrogen receptor (ER)-positive, tamoxifen-sensitive MCF7 cell line and highlighted that this multi-faceted transcription factor is key to the effects of tamoxifen in an endocrine sensitive model. In this work, we explored further the in vitro role of ATF2 in defining the resistance to endocrine treatment. Materials and methods We knocked down ATF2 in TAMR, LCC2 and LCC9 tamoxifen-resistant breast cancer cell lines as well as the parental tamoxifen sensitive MCF7 cell line and investigated the effects on growth, colony formation and cell migration. We also performed a microarray gene expression profiling (Illumina Human HT12_v4) to explore alterations in gene expression between MCF7 and TAMRs after ATF2 silencing and confirmed gene expression changes by quantitative RT-PCR. Results By silencing ATF2, we observed a significant growth reduction of TAMR, LCC2 and LCC9 with no such effect observed with the parental MCF7 cells. ATF2 silencing was also associated with a significant inhibition of TAMR, LCC2 and LCC9 cell migration and colony formation. Interestingly, knockdown of ATF2 enhanced the levels of ER and ER-regulated genes, TFF1 , GREB1 , NCOA3 and PGR , in TAMR cells both at RNA and protein levels. Microarray gene expression identified a number of genes known to mediate tamoxifen resistance, to be differentially regulated by ATF2 in TAMR in relation to the parental MCF7 cells. Moreover, differential pathway analysis confirmed enhanced ER activity after ATF2 knockdown in TAMR cells. Conclusion These data demonstrate that ATF2 silencing may overcome endocrine resistance and highlights further the dual role of this transcription factor that can mediate endocrine sensitivity and resistance by modulating ER expression and activity.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Activating Transcription Factor 2 - genetics / Activating Transcription Factor 2 - metabolism / Analysis / Antineoplastic Agents, Hormonal - pharmacology / Antineoplastic Agents, Hormonal - therapeutic use / ATF2 / Biomedical and Life Sciences / Biomedicine / Breast cancer / Breast Neoplasms - drug therapy / Breast Neoplasms - genetics / Breast Neoplasms - pathology / Cancer Research / Cell cycle / Cell growth / Cell migration / Cell Movement - genetics / Colonies / Deoxyribonucleic acid / DNA / DNA binding proteins / DNA methylation / DNA microarrays / Drug Resistance, Neoplasm - genetics / Endocrine resistance / Endocrine therapy / Estrogens / Experiments / Female / Gene expression / Gene Expression Profiling / Gene Expression Regulation, Neoplastic - drug effects / Gene Expression Regulation, Neoplastic - genetics / Gene Knockdown Techniques / Genes / Humans / Leucine zipper proteins / MCF-7 Cells / Metastasis / Oligonucleotide Array Sequence Analysis / Oncology / Phenols / Phosphorylation / Polymerase chain reaction / Protein arrays / Protein binding / Receptors, Estrogen - analysis / Receptors, Estrogen - antagonists & inhibitors / Receptors, Estrogen - genetics / Receptors, Estrogen - metabolism / Research Article / Ribonucleic acid / RNA / Surgical Oncology / Tamoxifen / Tamoxifen - pharmacology / Tamoxifen - therapeutic use / Transcription factors / Tumor cell lines / Tumors