Butyrate's role in human health and the current progress towards its clinical application to treat gastrointestinal disease.

Butyrate is a key energy source for colonocytes and is produced by the gut microbiota through fermentation of dietary fiber. Butyrate is a histone deacetylase inhibitor and also signals through three G-protein coupled receptors. It is clear that butyrate has an important role in gastrointestinal health and that butyrate levels can impact both host and microbial functions that are intimately coupled with each other. Maintaining optimal butyrate levels improves gastrointestinal health in animal models by supporting colonocyte function, decreasing inflammation, maintaining the gut barrier, and promoting a healthy microbiome. Butyrate has also shown protective actions in the context of intestinal diseases such as inflammatory bowel disease, graft-versus-host disease of the gastrointestinal tract, and colon cancer, whereas lower levels of butyrate and/or the microbes which are responsible for producing this metabolite are associated with disease and poorer health outcomes. However, clinical efforts to increase butyrate levels in humans and reverse these negative outcomes have generated mixed results. This article discusses our current understanding of the molecular mechanisms of butyrate action with a focus on the gastrointestinal system, the links between host and microbial factors, and the efforts that are currently underway to apply the knowledge gained from the bench to bedside.

Single-cell RNA-sequencing reveals transcriptional dynamics of estrogen-induced dysplasia in the ovarian surface epithelium.

Estrogen therapy increases the risk of ovarian cancer and exogenous estradiol accelerates the onset of ovarian cancer in mouse models. Both in vivo and in vitro, ovarian surface epithelial (OSE) cells exposed to estradiol develop a subpopulation that loses cell polarity, contact inhibition, and forms multi-layered foci of dysplastic cells with increased susceptibility to transformation. Here, we use single-cell RNA-sequencing to characterize this dysplastic subpopulation and identify the transcriptional dynamics involved in its emergence. Estradiol-treated cells were characterized by up-regulation of genes associated with proliferation, metabolism, and survival pathways. Pseudotemporal ordering revealed that OSE cells occupy a largely linear phenotypic spectrum that, in estradiol-treated cells, diverges towards cell state consistent with the dysplastic population. This divergence is characterized by the activation of various cancer-associated pathways including an increase in Greb1 which was validated in fallopian tube epithelium and human ovarian cancers. Taken together, this work reveals possible mechanisms by which estradiol increases epithelial cell susceptibility to tumour initiation.

GREB1 is an estrogen receptor-regulated tumour promoter that is frequently expressed in ovarian cancer.

Estrogenic hormone replacement therapy increases the risk of developing ovarian cancer, and estrogen promotes tumour initiation and growth in mouse models of this disease. GREB1 (Growth regulation by estrogen in breast cancer 1) is an ESR1 (estrogen receptor 1)-upregulated protein which may mediate estrogen action. GREB1 knockdown prevents hormone-driven proliferation of several breast and prostate cancer cell lines and prolongs survival of mice engrafted with ovarian cancer cells, but its mechanism of action remains unclear. In this study, we explored GREB1 function in ovarian cancer. GREB1 overexpression in ovarian cancer cell lines increased cell proliferation and migration and promoted a mesenchymal morphology associated with increased Col1a2, which encodes a collagen I subunit. GREB1 knockdown inhibited proliferation and promoted an epithelial morphology associated with decreased Col1a2. In human tissues, GREB1 was expressed in all ESR1-expressing tissues throughout the normal female reproductive tract, in addition to several tissues that did not show ESR1 expression. In a TMA of ovarian cancer cases, GREB1 was expressed in 75-85% of serous, endometrioid, mucinous, and clear cell carcinomas. Serous, endometrioid, and mucinous ovarian cancers were almost always positive for either ESR1 or GREB1, suggesting a possible reliance on signalling through ESR1 and/or GREB1. Targeting GREB1 may inhibit tumour-promoting pathways both downstream and independent of ESR1 and is therefore a possible treatment strategy worthy of further investigation.

Intersecting Worlds of Transfusion and Transplantation Medicine: An International Symposium Organized by the Canadian Blood Services Centre for Innovation.

The principal theme of the symposium was centered on how the world of regenerative medicine intersects with that of transfusion medicine, with a particular focus on hematopoietic stem cells (HSCs) and stem cell therapies. The symposium highlighted several exciting developments and identified areas where additional research is needed. A revised map of human hematopoietic hierarchy was presented based on the functional and phenotypic analysis of thousands of single stem and progenitor cells from adult bone marrow and fetal liver. These analyses revealed that multipotency is largely restricted to the HSC and multipotent progenitor compartments in adult bone marrow where most progenitors are unipotent, whereas fetal liver contains a large number of distinct oligopotent progenitors. Furthermore, unlike adult bone marrow, multipotency is extended in the downstream progenitors in the hierarchy in the fetal liver stage. Production of platelets ex vivo from HSCs is emerging as a potentially viable option because of advances in culture techniques that combine cytokine mixtures, small molecules, and shear stress. However, limited HSC expansion and low platelet yield from culture-derived megakaryocytes remain problematic. Evidence was presented to support stricter guidelines for transfusion of platelets and red blood cells practices in allogeneic HSC transplant patients, although evidence is often extrapolated from general indications. Basic principles of human leukocyte antigen testing in HSC transplant were described, emphasizing the need for a national (and global) stem cell donor registry. Ongoing research is aimed at improving cellular cryopreservation including the establishment of a new thawing protocol that improves viability of umbilical cord blood CD34+ cells. Umbilical cord blood transplantation practices have also been improved; recent studies suggest noninferior outcomes when patients are transplanted with umbilical cord blood vs a matched adult donor. Finally, mesenchymal stem cell infusion is an example of a cellular therapy useful for immunomodulation. Preclinical trials suggest that mesenchymal stem cells may be effective in managing sepsis. In conclusion, practices and research surrounding HSCs are continuing to evolve rapidly as new information is obtained.

Consideration of GREB1 as a potential therapeutic target for hormone-responsive or endocrine-resistant cancers.

INTRODUCTION: Steroid hormones increase the incidence and promote the progression of many types of cancer. Exogenous estrogens increase the risk of developing breast, ovarian and endometrial cancer and many breast cancers initially respond to estrogen deprivation. Although steroid hormone signaling has been extensively studied, the mechanisms of hormone-stimulated cancer growth have not yet been fully elucidated, limiting opportunities for novel approaches to therapeutic intervention. AREAS COVERED: This review examines growing evidence for the important role played by the steroid hormone-induced gene called GREB1, or growth regulation by estrogen in breast cancer 1. GREB1 is a critical mediator of both the estrogen-stimulated proliferation of breast cancer cells and the androgen-stimulated proliferation of prostate cancer cells. EXPERT OPINION: Although its exact function in the cascade of hormone action remains unclear, the ability of GREB1 to modulate tumor progression in models of breast, ovarian and prostate cancer renders this gene an excellent candidate for further consideration as a potential therapeutic target. Research examining the mechanism of GREB1 action will help to elucidate its role in proliferation and its potential contribution to endocrine resistance and will determine whether GREB1 interference may have therapeutic efficacy.

17ß-estradiol upregulates GREB1 and accelerates ovarian tumor progression in vivo.

Exogenous 17ß-estradiol (E2) accelerates the progression of ovarian cancer in the transgenic tgCAG-LS-TAg mouse model of the disease. We hypothesized that E2 has direct effects on ovarian cancer cells and this study was designed to determine the molecular mechanisms by which E2 accelerates ovarian tumor progression. Mouse ovarian cancer ascites (MAS) cell lines were derived from tgCAG-LS-TAg mice. Following intraperitoneal engraftment of two MAS cell lines, MASC1 and MASE2, into SCID mice, exogenous E2 significantly decreased the survival time and increased the tumor burden. Microarray analysis performed on MASE2-derived tumors treated with E2 or placebo showed that E2 treatment caused the upregulation of 197 genes and the downregulation of 55 genes. The expression of gene regulated by estrogen in breast cancer 1 (Greb1) was upregulated in mouse tumors treated with E2 and was overexpressed in human ovarian cancers relative to human ovarian surface epithelium, suggesting a role for GREB1 in human ovarian tumor progression. RNA interference-mediated knockdown of GREB1 in MASE2 cells decreased their proliferation rate in vitro and increased survival time in mice engrafted with the cells. These results emphasize the importance of E2 in ovarian tumor progression and identify Greb1 as a novel gene target for therapeutic intervention.

Estrogen responsiveness of the TFIID subunit TAF4B in the normal mouse ovary and in ovarian tumors.

Estrogen signaling in the ovary is a fundamental component of normal ovarian function, and evidence also indicates that excessive estrogen is a risk factor for ovarian cancer. We have previously demonstrated that the gonadally enriched TFIID subunit TAF4B, a paralog of the general transcription factor TAF4A, is required for fertility in mice and for the proliferation of ovarian granulosa cells following hormonal stimulation. However, the relationship between TAF4B and estrogen signaling in the normal ovary or during ovarian tumor initiation and progression has yet to be defined. Herein, we show that Taf4b mRNA and TAF4B protein, but not Taf4a mRNA or TAF4A protein, are increased in whole ovaries and granulosa cells of the ovary after exposure to 17beta-estradiol or the synthetic estrogen diethylstilbestrol and that this response occurs within hours after stimulation. Furthermore, this increase occurs via nuclear estrogen receptors both in vivo and in a mouse granulosa cancer cell line, NT-1. We observe a significant increase in Taf4b mRNA in estrogen-supplemented mouse ovarian tumors, which correlates with diminished survival of these mice. These data highlight the novel response of the general transcription factor TAF4B to estrogen in the normal ovary and during ovarian tumor progression in the mouse, suggesting its potential role in regulating actions downstream of estrogen stimulation.