Susan P. Perrine

A short-term trial of butyrate to stimulate fetal-globin-gene expression in the β-globin disorders

BACKGROUND Fetal-globin (gamma-globin) chains inhibit the polymerization of hemoglobin S (sickle hemoglobin) and can functionally substitute for the beta-globin chains that are defective or absent in patients with the beta-thalassemias. Identifying safe mechanisms to stimulate fetal-hemoglobin production is therefore of great interest. Previous studies have shown that administering butyrate selectively stimulates the promoter of the human fetal-globin gene and leads to increases in gamma-globin--gene expression in the developing fetus, cultured cells, and animal models. METHODS To determine whether butyrate can stimulate fetal-globin production in humans, we treated three patients (3 to 13 years old) with sickle cell anemia and three patients (7 to 27 years old) with beta-thalassemia syndromes with a short course of intravenous infusions of arginine butyrate. The drug was infused continuously for either two or three weeks; the initial dose was 500 mg per kilogram of body weight per day. Globin-chain ratios, proportions of reticulocytes producing hemoglobin F (F reticulocytes), and levels of gamma-globin messenger RNA (mRNA) were determined before and during treatment. RESULTS In all six patients, fetal-globin synthesis increased by 6 to 45 percent above pretreatment levels (P < 0.01). The proportion of F reticulocytes increased about twofold, and the level of gamma-globin mRNA increased twofold to sixfold. The increase in gamma-globin synthesis led to improvement in the globin-chain ratios in the patients with thalassemia. The treatment of one patient was extended for seven weeks, and her hemoglobin level increased from 4.7 to 10.2 g per deciliter (2.9 to 6.3 mmol per liter). Side effects were minimal; one patient had a transient increase in serum aminotransferase concentrations. CONCLUSIONS In patients with beta-hemoglobinopathies butyrate, a natural fatty acid, can significantly and rapidly increase fetal-globin production to levels that can ameliorate beta-globin disorders. Further trials of this class of compounds are warranted to determine long-term tolerance and efficacy in patients with sickle cell anemia or beta-thalassemia.

Natural history of sickle cell anemia in Saudi Arabs. A study of 270 subjects.

We studied 270 Saudi Arabs with homozygous sickle cell anemia, using chart review, a register (since 1969), and home visiting in 42 cases. Average follow-up for the total group was 10 years. Seventy-four percent of those diagnosed by age 3 years presented on screening or with merely anemia; 26% presented with illness, abnormal physical findings, or pain. Compared with American or Jamaican blacks, serious complications occurred only 6% to 25% as frequently; leg ulcers did not occur at all; the mortality under age 15 years was 10% as great; mean levels of blood hemoglobin were higher (10 g/dl), reticulocyte count was lower (5% to 6%), and mean fetal hemoglobin (HbF), which was inversely correlated with reticulocytes, was higher (22% to 26.8%). The high HbF is believed to account for the very mild clinical manifestations.

Delay in the Fetal Globin Switch in Infants of Diabetic Mothers

In the normal fetus, a switch from production of hemoglobin F (alpha 2 gamma 2) to hemoglobin A (alpha 2 beta 2) occurs at 28 to 34 weeks of gestation. In the fetus with beta-hemoglobinopathy or beta-thalassemia, this switch proceeds despite the morbidity that results when production of beta-globin is abnormal or reduced. Since insulin has recently been shown to induce renewed expression of some inactive genes, we studied globin biosynthesis during the natural evolution of the fetal globin switch under conditions of hyperinsulinemia, which occurs in infants of diabetic mothers. Such infants develop in a hyperglycemic environment, which produces reactive hyperinsulinemia. The normal increase in beta-globin production from pre-switch levels did not occur in 9 of 10 such infants at term, as compared with 11 normal infants, in whom the switch occurred by 36 to 39 weeks of gestation (P less than 0.0001). The delay in the switch from gamma-globin to beta-globin in this unique clinical setting may allow identification of physiologic factors that can modulate developmental gene suppression.

SURFACE PROTEIN ABNORMALITIES IN LYMPHOCYTES AND PLATELETS FROM PATIENTS WITH WISKOTT-ALDRICH SYNDROME

Lymphocytes from three patients with the Wiskott-Aldrich syndrome were subjected to surface radioiodination and their 125I-labelled surface proteins were analysed by SDS-polyacrylamide gel electrophoresis and autoradiography. Autoradiographs demonstrated the absence in all three patients of an 125I-labelled protein, molecular weight of 115 000, that was present in normal individuals. In addition, one patient had an additional labelled protein, molecular weight 135 000, not found in normal individuals. The platelets from one patient were radioiodinated and the 125I-labelled membrane proteins were analysed. Glycoproteins Ia and Ib were reduced in amount and restricted in heterogeneity while glycoproteins IIb and IIIa were normal. These results suggest that the primary defect in the Wiskott-Aldrich syndrome may be abnormalities of (glyco)proteins normally present on the surface of lymphocytes and platelets.

Hypoxia increases thrombospondin-1 transcript and protein in cultured endothelial cells☆

The exposure of endothelial cells to hypoxic environments regulates the expression of a number of genes with products that are vasoactive or mitogenic for vascular tissue, including platelet-derived growth factor, endothelin-1, and endothelial nitric oxide synthase. Hypoxia is also known to alter the adhesive properties of endothelium toward a variety of blood cell types. Thrombospondin-1 (TSP-1) is a glycoprotein with major roles in cellular adhesion and vascular smooth muscle proliferation and migration. We report here that hypoxia induces TSP-1 gene and protein expression. Oxygen tensions of < or =30 torr resulted in TSP-1 transcript induction initially apparent at 1 to 6 hours, with maximal induction (6.5-fold+/-1.2-fold) within 24 to 48 hours in both human and bovine endothelial cells. TSP-1 protein levels remain elevated after 72 hours of continuous hypoxic exposure. The induction of TSP-1 steady-state transcript levels is caused in large part, if not entirely, by post-transcriptional stabilization of the TSP-1 mRNA. The TSP-1 induction by hypoxia is a graded and reversible physiologic response and can be mimicked by the use of cobalt chloride or the inhibition of nitric oxide production, suggesting both the involvement of a heme-containing oxygen sensor and a role for the endogenous production of nitric oxide in TSP-1 regulation. The effects of hypoxia both on the stabilization of the TSP-1 transcript and the stimulation of TSP-1 protein production are completely inhibited by arginine butyrate.

Induction of the Epstein-Barr virus thymidine kinase gene with concomitant nucleoside antivirals as a therapeutic strategy for Epstein-Barr virus-associated malignancies.

Lymphoproliferative diseases (LPDs) associated with the Epstein-Barr virus (EBV) include non-Hodgkin lymphomas, which occur in the setting of immunosuppression, including that induced by human immunodeficiency virus, and posttransplant lymphoproliferative disorders. These LPDs are characterized by actively proliferating, latently infected EBV-positive B lymphocytes and often follow a rapidly progressive fatal clinical course. Pharmacologic treatment for herpesvirus infections has targeted the virus-specific enzyme, thymidine kinase (TK), with nucleoside analogs. The lack of viral TK expression in EBV-positive tumors, caused by viral latency, however, makes antiviral therapy alone ineffective as an antineoplastic therapy. Arginine butyrate selectively activates the EBV TK gene in latently infected EBV-positive tumor cells. We have developed a strategy for treatment of EBV-associated lymphomas using pharmacologic induction of the latent viral TK gene and enzyme in tumor cells using arginine butyrate, followed by treatment with ganciclovir. A phase I/II trial, using an intrapatient dose escalation of arginine butyrate combined with ganciclovir, is underway. This combination therapy has produced complete clinical responses in 5 of 10 previously refractory patients, with partial responses occurring in 2 additional patients. This virus-targeted antitumor strategy may provide a new therapeutic approach to EBV-associated neoplasms.

α‐Lipoic acid induces p27Kip‐dependent cell cycle arrest in non‐transformed cell lines and apoptosis in tumor cell lines

α‐Lipoic acid is a naturally‐occurring co‐factor found in a number of multi‐enzyme complexes regulating metabolism. We report here that α‐lipoic acid induces hyperacetylation of histones in vivo and has differential effects on the growth and viability of normal versus transformed cell lines. The human tumor cell lines FaDu and Jurkat, as well as a Ki‐v‐Ras‐transformed Balb/c‐3T3 murine mesenchymal cell line, all initiated apoptosis following exposure to α‐lipoic acid. In contrast, treatment of non‐transformed cell lines with α‐lipoic acid resulted only in reversible cell cycle arrest in G0/G1. Treatment with butyrate, another short‐chain fatty acid, induced a G0/G1 arrest in both transformed and non‐transformed cell lines. α‐Lipoic acid caused a post‐translational elevation in the levels of the cyclin‐dependent kinase inhibitor p27Kip1. Studies using p27Kip1‐deficient MEF cells demonstrated that p27Kip1 was required for the α‐lipoic acid‐mediated cell cycle arrest. The mechanism of apoptosis was independent of Fas‐mediated signaling, as α‐lipoic acid‐treated Jurkat cell mutants deficient in Fas or FADD retained sensitivity to apoptosis. The differential selectivity of the pro‐apoptotic effects of α‐lipoic acid for transformed cells supports its potential use in the treatment of neoplastic disorders.

Epstein–Barr virus post-transplant lymphoproliferative disease and virus-specific therapy: pharmacological re-activation of viral target genes with arginine butyrate

Abstract: Lymphoproliferative disorders associated with the Epstein–Barr virus (EBV) include non‐Hodgkin’s lymphoma, Hodgkin’s lymphoma, and “post‐transplant lymphoproliferative disorders” (PTLD), which occur with immunosuppression after marrow and organ transplantation. PTLD is characterized by actively proliferating, latently infected EBV(+) B‐lymphocytes, and often manifests a rapidly progressive fatal clinical course if the immunosuppression cannot be reversed. Lung transplant recipients are a subset of patients at special risk for developing PTLD. The incidence of PTLD development in these patients has been estimated at 5–10%. Whereas immunologic and antiviral therapy have been moderately effective for treating EBV‐associated infections in the lytic phase, they have been less useful in the more common latent phase of the disease. One common treatment for herpesvirus infections has targeted the virus‐specific enzyme thymidine kinase (TK). The lack of viral TK expression in EBV(+) tumor cells, due to viral latency, makes anti‐viral therapy alone ineffective as an anti‐neoplastic therapy, however. We have developed a strategy for the treatment of EBV‐associated lymphomas/PTLD using pharmacologic induction of the latent viral TK gene and enzyme in the tumor cells, followed by treatment with ganciclovir. Arginine butyrate selectively activates the EBV TK gene in latently EBV‐infected human lymphoid cells and tumor cells. A Phase I/II trial has been initiated, employing an intra‐patient dose escalation of arginine butyrate combined with ganciclovir. In six patients with EBV‐associated lymphomas or PTLD, all of which were resistant to conventional radiation and/or chemotherapy, this combination produced complete clinical responses in four of six patients, with a partial response occurring in a fifth patient. Pathologic examination in two of three patients demonstrated complete necrosis of the EBV lymphoma, with no residual disease, following a single three‐week course of the combination therapy. Possible side‐effects of the therapy included nausea and reversible lethargy at the highest doses. One patient suffered acute liver failure, thought to be secondary to release of FasL from the necrotic tumor. Analysis of patient‐derived tumor cells in culture demonstrated that arginine butyrate produced selective induction of the EBV TK gene, which then conferred sensitivity to ganciclovir, resulting in tumor apoptosis. Additional patient accrual is sought for further evaluation of this therapy.

Histone deacetylase inhibitors are potent inducers of gene expression in latent EBV and sensitize lymphoma cells to nucleoside antiviral agents

Induction of EBV lytic-phase gene expression, combined with exposure to an antiherpes viral drug, represents a promising targeted therapeutic approach to EBV-associated lymphomas. Short-chain fatty acids or certain chemotherapeutics have been used to induce EBV lytic-phase gene expression in cultured cells and mouse models, but these studies generally have not translated into clinical application. The recent success of a clinical trial with the pan-histone deacetylase (pan-HDAC) inhibitor arginine butyrate and the antiherpes viral drug ganciclovir in the treatment of EBV lymphomas prompted us to investigate the potential of several HDAC inhibitors, including some new, highly potent compounds, to sensitize EBV(+) human lymphoma cells to antiviral agents in vitro. Our study included short-chain fatty acids (sodium butyrate and valproic acid); hydroxamic acids (oxamflatin, Scriptaid, suberoyl anilide hydroxamic acid, panobinostat [LBH589], and belinostat [PXD101]); the benzamide MS275; the cyclic tetrapeptide apicidin; and the recently discovered HDAC inhibitor largazole. With the exception of suberoyl anilide hydroxamic acid and PXD101, all of the other HDAC inhibitors effectively sensitized EBV(+) lymphoma cells to ganciclovir. LBH589, MS275, and largazole were effective at nanomolar concentrations and were 10(4) to 10(5) times more potent than butyrate. The effectiveness and potency of these HDAC inhibitors make them potentially applicable as sensitizers to antivirals for the treatment of EBV-associated lymphomas.

Butyrate Histone Deacetylase Inhibitors

Abstract In addition to being a part of the metabolic fatty acid fuel cycle, butyrate is also capable of inducing growth arrest in a variety of normal cell types and senescence-like phenotypes in gynecological cancer cells, inhibiting DNA synthesis and cell growth in colonic tumor cell lines, suppressing hTERT mRNA expression and telomerase activity in human prostate cancer cells, and inducing stem cell differentiation and apoptosis by DNA fragmentation. It regulates gene expression by inhibiting histone deacetylases (HDACs), enhances memory recovery and formation in mice, stimulates neurogenesis in the ischemic brain, promotes osteoblast formation, selectively blocks cell replication in transformed cells (compared to healthy cells), and can prevent and treat diet-induced obesity and insulin resistance in mouse models of obesity, as well as stimulate fetal hemoglobin expression in individuals with hematologic diseases such as the thalassemias and sickle-cell disease, in addition to a multitude of other biochemical effects in vivo. However, efforts to exploit the potential of butyrate in the clinical treatment of cancer and other medical disorders are thwarted by its poor pharmacological properties (short half-life and first-pass hepatic clearance) and the multigram doses needed to achieve therapeutic concentrations in vivo. Herein, we review some of the methods used to overcome these difficulties with an emphasis on HDAC inhibition.