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Glucose impairs tamoxifen sensitivity modulating CTGF in breast cancer cells

ABSTRACT: Metabolic diseases, including type 2 diabetes and obesity are relevant negative prognostic factor in patients with breast cancer (BC). We have investigated the mechanisms through which elevated glucose levels affect tamoxifen sensitivity of estrogen receptor positive (ER+) BC cells. We found that MCF7 BC cell sensitivity to tamoxifen was 2-fold reduced in 25mM glucose (HG), a concentration mimicking hyperglycaemia, compared to 5.5 mM glucose (LG), resembling normal fasting glucose levels in humans. Shifting MCF7 cells from HG to LG ameliorated their responsiveness to tamoxifen. RNA-Sequencing revealed that glucose modified the transcriptome of MCF7 cells. In particular, cell cycle-related genes were affected by glucose. Combining gene specific knockdown and treatment with human recombinant proteins, we identified the Connective Tissue Growth Factor (CTGF) as glucose-induced factor able to reduce MCF7 cell sensitivity to tamoxifen. Moreover, we found that both CTGF expression levels and tamoxifen responsiveness were enhanced co-culturing MCF7 cells with human adipocytes through an Interleukin-8 (IL8)-mediated mechanism. Indeed, IL8 inhibition reduced CTGF levels and rescued tamoxifen sensitivity in MCF7 cells. Interestingly, CTGF immuno-detection in bioptic specimens obtained from women with ER+ BC correlated with distant metastases (P-value = 0.000), hormone therapy resistance (P-value = 0.000), reduced overall (P-value = 0.051) and disease free survival (P-value = 0.000). Thus, glucose affects tamoxifen responsiveness directly modulating CTGF in BC cells, and indirectly promoting the adipocytes’ release of IL8. Both CTGF and IL8 may represent potential targets in novel therapeutic strategies to increase tamoxifen sensitivity.

ORGANISM(S): Homo sapiens

PROVIDER: GSE97647 | GEO | 2017/07/01

SECONDARY ACCESSION(S): PRJNA382560

REPOSITORIES: GEO

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Project description:Phosphoinositide-3-kinase/protein-kinaseB/mammalian target of rapamycin (PI3K/AKT/mTOR) signalling plays an important role in breast cancer (BC). Its interaction with estrogen receptor (ER) signalling becomes more complex and inter-dependent with acquired endocrine resistance. Targeting mTOR combined with endocrine therapy has shown clinical utility, however, a negative feedback-loop exists downstream of PI3K/AKT/mTOR. Direct blockade of AKT together with endocrine therapy may improve BC treatment. AZD5363, a novel pan-AKT kinase catalytic inhibitor, was examined in a panel of ER+ BC cell lines (MCF7, HCC1428, T47D, ZR75.1) adapted to long-term-estrogen-deprivation (LTED) or tamoxifen (TamR). AZD5363 caused a dose-dependent decrease in proliferation in all cell lines tested (GI50<500nM) except HCC1428 and HCC1428-LTED. T47D-LTED and ZR75-LTED were the most sensitive of the lines (GI50~100nM). AZD5363 re-sensitised TamR cells to tamoxifen and acted synergistically with fulvestrant. AZD5363 decreased p-AKT/mTOR targets leading to a reduction in ERα-mediated transcription in a context specific manner and concomitant decrease in recruitment of ER and CREB-binding protein (CBP) to estrogen-response-elements located on the TFF1, PGR and GREB1 promoters. Furthermore, AZD5363 reduced expression of cell-cycle-regulatory proteins. Global gene expression highlighted ERBB2-ERBB3, ERK5 and IGF1 signaling pathways driven by MYC as potential feedback-loops. Combined treatment with AZD5363 and fulvestrant showed synergy in an ER+ patient derived xenograft and delayed tumour progression post-cessation of therapy. These data support the combination of AZD5363 with fulvestrant as a potential therapy for BC that is sensitive or resistant to E-deprivation or tamoxifen and that activated AKT is a determinant of response, supporting the need for clinical evaluation. Cell lines were treated in biological triplicates in the absence of estrogen with or without AZD5363 for 24hours in order to identify gene changes associated with perturbation of AKT signalling

Project description:Targeting the estrogen signaling pathway has proved to be of great value in the treatment of human breast cancer. Tamoxifen, a selective estrogen receptor modulator (SERM), is the most widely used antiestrogen. However, only 40-50% of patients with estrogen receptor (ER) positive breast cancer benefit from tamoxifen treatment and 30-50% acquire resistance and the disease progresses. Continuous treatment with conventional therapy may contribute to cancer progression in recurring cancers through the accumulation of drug resistant cancer progenitors. We found that MCF7 tamoxifen-resistant (TAM-R) cells possess a significantly higher proportion of cancer progenitor cells than tamoxifen-sensitive MCF7 cells. Our results indicate that the chemokine receptor CXCR4 plays an important role in the maintenance of cancer progenitors in a tamoxifen-resistant cell line and downregulation of CXCR4 signaling by small molecule antagonists specifically inhibits growth of a stem-like cell population in tamoxifen-resistant tumors both in vitro and in vivo. Whole genome gene expression analysis revealed aryl hydrocarbon receptor (AhR) signaling as one of the top networks that is differentially regulated in MCF7(TAM-R) xenograft tumors treated with the CXCR4 antagonist AMD3100 as compared to MCF7 tumors. Further, small molecule antagonists of AhR signaling specifically inhibit the progenitor population in MCF7(TAM-R) cells suggesting that the aryl hydrocarbon receptor could be a putative target for the treatment of tamoxifen-resistant breast cancers. Introduction transplants remains limited by the ability to expand these cells ex vivo. An unbiased screen with primary human HSCs identified a purine derivative, StemRegenin 1 (SR1), that promotes the ex vivo expansion of CD34+ cells. Culture of HSCs with SR1 led to a 50-fold increase in cells expressing CD34 and a 17-fold increase in cells that retain the ability to engraft immunodeficient mice. Mechanistic studies show that SR1 acts by antagonizing the aryl hydrocarbon receptor (AHR). The identification of SR1 and AHR modulation as a means to induce ex vivo HSC expansion should facilitate the clinical use of HSC therapy.

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Glucose impairs tamoxifen sensitivity modulating CTGF in breast cancer cells

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