Suppression of HIF-1α by Valproic Acid Sustains Self-Renewal of Mouse Embryonic Stem Cells under Hypoxia In Vitro

Abstract

The developing embryo naturally experiences relatively low oxygen conditions in vivo. Under in vitro hypoxia, mouse embryonic stem cells (mESCs) lose their self-renewal activity and display an early differentiated morphology mediated by the hypoxia-inducible factor-1α (HIF-1α). Previously, we demonstrated that histone deacetylase (HDAC) is activated by hypoxia and increases the protein stability and transcriptional activity of HIF-1α in many human cancer cells. Furthermore HDAC1 and 3 mediate the differentiation of mECSs and hematopoietic stem cells. However, the role of HDACs and their inhibitors in hypoxia-induced early differentiation of mESCs remains largely unknown. Here, we examined the effects of several histone deacetylase inhibitors (HDA-CIs) on the self-renewal properties of mESCs under hypoxia. Inhibition of HDAC under hypoxia effectively decreased the HIF-1α protein levels and substantially improved the expression of the LIF-specific receptor (LIFR) and phosphorylated-STAT3 in mESCs. In particular, valproic acid (VPA), a pan HDACI, showed dramatic changes in HIF-1α protein levels and LIFR protein expression levels compared to other HDACIs, including sodium butyrate (SB), trichostatin A (TSA), and apicidin (AP). Importantly, our RT-PCR data and alkaline phosphatase assays indicate that VPA helps to maintain the self-renewal activity of mESCs under hypoxia. Taken together, these results suggest that VPA may block the early differentiation of mESCs under hypoxia via the destabilization of HIF-1α.

Induction of LIFR confers a dormancy phenotype in breast cancer cells disseminated to the bone marrow

“…However, it is well documented that HDACs and histone methyltransferases possess compensatory functions 26 . Therefore we used the pan-HDAC inhibitor valproic acid (VPA) 27 , which enhanced histone H3 acetylation in MCF7 cells in vitro ( Fig. 2e ), and significantly increased LIFR and SOCS3 mRNA levels in hypoxia ( Fig.…”

Effect of Hypoxia on the Differentiation and the Self-Renewal of Metanephrogenic Mesenchymal Stem Cells

“…Moreover, a study has reported that hypoxia is not beneficial for maintaining human embryonic stem cells in the undifferentiated state [ 39 ]. Another study has demonstrated that mouse embryonic stem cells lose self-renewal activity under in vitro hypoxia [ 40 ]. Our present results showed that hypoxia exposure reduced the expression of SIX-2 and CITED1 and the number of SIX-2-positive cells.…”

Acetylation and deacetylation in cancer stem-like cells

“…HDACs also participate in the regulation of stemness property of normal stem cells. HDAC1 and HDAC3 were shown to be activated by hypoxia and mediate the differentiation of mouse embryonic stem cells and hematopoietic stem cells [ 65 ]. Octamer-binding transcription factor 4 (Oct4) is an important transcriptional factor of embryonic stem cells which is commonly used as a marker of normal stem cells and cancer stem-like cells.…”

“…However, another HDACI valproic acid (VPA) was previously reported to enhance self-renewal and cytokine-induced expansion of hematopoietic stem cells [ 96 – 98 ]. VPA could maintain the self-renewal ability of mouse embryonic stem cells (mESCs) under hypoxic conditions by suppression of HIF-1alpha [ 65 ]. Conversely, in a recent study, VPA induced significant upregulation of neuroprogenitor marker Musashi, CD133 and Nestin, which suggests that VPA may play a key role in neuronal differentiation of human bone-marrow mesenchymal stromal cells (BM-MSCs) [ 99 ].…”