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Erythropoietin promotes breast tumorigenesis through tumor initiating cell self-renewal

ABSTRACT: The erythropoietin (EPO) hormone induces red blood cell production and its recombinant form is the most prescribed drug for the treatment of anemia, including that arising in cancer patients. Based on randomized trials showing that EPO administration to cancer patients result in a decreased survival, we investigated the impact of EPO modulation on tumorigenesis. Using genetically engineered mouse models of breast cancer we found that EPO promoted tumorigenesis by activating JAK/STAT signaling specifically in breast tumor initiating cells (TICs) and promoting their self-renewal. Moreover, we define an active role for endogenous EPO in breast cancer progression and breast TIC self-renewal and demonstrate a potential application of EPO pathway inhibition in breast cancer therapy.

ORGANISM(S): Homo sapiens

PROVIDER: GSE51433 | GEO | 2014/05/31

SECONDARY ACCESSION(S): PRJNA224091

REPOSITORIES: GEO

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Project description:Abstract Background: Several studies on the use of erythropoietin (Epo) to treat anaemia in patients undergoing cancer treatment have shown adverse effects on tumour control and survival. Experimental studies indicate that this could be linked to an interaction with wound healing processes and not an effect on tumour cells per se. We have previously shown that erythropoietin in combination with surgical trauma stimulates tumour growth. In the present study, we investigated the effect of surgery and Epo on gene expression. Methods: Human tumours from oral squamous cell cancer were xenotransplanted to nude mice treated with Epo. The tumours were then transected in a standardised procedure to mimic surgical trauma and the change in gene expression of the tumours was investigated by microarray analysis. qRT-PCR was used to measure the levels of mRNAs of pro-apoptotic genes. The frequency of apoptosis in the tumours was assessed using immunohistochemistry for caspase-3. Results: There was little change in the expression of genes involved in tumour growth and angiogenesis but a significant down-regulation of the expression of genes involved in apoptosis. This effect on apoptosis was confirmed by a general decrease in the expression of mRNA for selected pro-apoptotic genes. Epo-treated tumours had a significantly lower frequency of apoptosis as measured by immunohistochemistry for caspase 3. Conclusions: Our results suggest that the increased tumour growth during erythropoietin treatment might be due to inhibition of apoptosis, an effect that becomes significant during tissue damage such as surgery. This further suggests that the decreased tumour survival during erythropoietin treatment might be due to inhibition of apoptosis. Key words: Erythropoietin, Head and neck cancer, surgery, apoptosis, wound healing, xenograft. We wanted to study the effect of wound healing mechanisms on remaining tumour tissue efter incomplete surgery or biopsy. We xenografted human Head and Neck squamous Cell Cancer (HNSCC) tumours on Balb/c nude mice. The mice were divided in six groups. Three of the groups received intrapertoneal doses of erythropoietin (Epo) and the other three groups were given NaCl as placebo. One treated and one non-treated group were harvested without surgical transection. In the other four groups, the tumours were transected mimicking subtotal surgery. One Epo-treated and one non-treated group was analysed after 24 hours after transection and the remaining two groups 48 hours after surgery. Groups C and D were not analyzed due to harvesting at an unsuitable time interval. Group A No surgery (=FALSE) + Epo Group B No surgery (=FALSE) + NaCl Group E Surgery (=TRUE) + Epo 24 hours after surgical transection Group F Surgery (=TRUE) + NaCl 24 hours after surgical resection Group G Surgery (=TRUE) + Epo 48 hours after surgical transection Group H Surgery (=TRUE) + Nacl 48 hours after surgical transection

Project description:Background: cancer cells rely on glycolysis as main ATP source (Warbürg effect). Tumor-initiating cells (TICs) are the fraction of cells that give raise and repopulate tumors. TICs are exposed to prolonged periods of oxygen and glucose deprivation (OGD), as they live in a hypoxic niche and they withstand prolonged lack of blood vessels during initial tumorigenesis or metastasis formation (avascular phase). Warbürg effect is energetically inefficient; we hypothesize that TICs might have differential metabolic features. Tumor eradication requires killing TICS; finding such features would have therapeutic implications. Methodology/principal findings: 106 MDA-MB-231 breast-cancer cells (hereafter Wt) were exposed for 5 weeks to 0.2% oxygen and 0.1g/l glucose, recovering 9 clones. Both flow-cytometry (50-fold enrichment in the CD24-/CD44+/CD133+ population) and xenografts in NOD/SCID mice using 100 cells (75% vs. 16% engraftment) suggest that OGD-resistant clones are true TICs (hereafter “TIC clones”). TIC clones showed a 30-fold higher replication and viability (BRDU incorporation, colony assay) than Wt. When exposed to OGD, ATP-production dropped 5-fold in WT, but was maintained in TIC clones by increasing 5-fold the fatty acid and oxygen consumption. These properties were explained by lack of upregulation of HIF-1 alpha and PDK1, as well as an increase in ATP-synthase. Analysis with metabolic inhibitors (2-deoxyglucose, antimycin-A) confirmed glycolysis and mitochondrial respiration as main routes of metabolism for Wt and TIC clones respectively. Metabolomics revealed that glutamine catabolism generated the NADPH required to quench reactive oxygen species generated during mitochondrial respiration in TIC clones. Glutamine deprivation or mitochondrial blockers were able to abrogate the viability of TIC clones. Conclusions/significance: the TIC-fraction of a cancer cell population withstands prolonged OGD by switching from the Warbürg effect to mitochondrial respiration. Targeting this metabolic feature abrogates the survival of TICs.

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Erythropoietin promotes breast tumorigenesis through tumor initiating cell self-renewal

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