Butyrate Increases Apoptosis Induced by Different Antineoplastic Drugs in Monocytic Leukemia Cells

RNA sequencing reveals niche gene expression effects of beta-hydroxybutyrate in primary myotubes

RNA sequencing reveals primary myocyte-specific gene-regulatory niche effects for β-hydroxybutyrate but do not support a general signaling of β-hydroxybutyrate role in other primary cells or during cellular differentiation in vitro.

Various forms of fasting and ketogenic diet have shown promise in (pre-)clinical studies to normalize body weight, improve metabolic health, and protect against disease. Recent studies suggest that β-hydroxybutyrate (βOHB), a fasting-characteristic ketone body, potentially acts as a signaling molecule mediating its beneficial effects via histone deacetylase inhibition. Here, we have investigated whether βOHB, in comparison to the well-established histone deacetylase inhibitor butyrate, influences cellular differentiation and gene expression. In various cell lines and primary cell types, millimolar concentrations of βOHB did not alter differentiation in vitro, as determined by gene expression and histological assessment, whereas equimolar concentrations of butyrate consistently impaired differentiation. RNA sequencing revealed that unlike butyrate, βOHB minimally impacted gene expression in primary adipocytes, macrophages, and hepatocytes. However, in myocytes, βOHB up-regulated genes involved in the TCA cycle and oxidative phosphorylation, while down-regulating genes belonging to cytokine and chemokine signal transduction. Overall, our data do not support the notion that βOHB serves as a powerful signaling molecule regulating gene expression but suggest that βOHB may act as a niche signaling molecule in myocytes.

Tributyltin(IV) Butyrate: A Novel Epigenetic Modifier with ER Stress- and Apoptosis-Inducing Properties in Colon Cancer Cells

Organotin(IV) compounds are a class of non-platinum metallo-conjugates exhibiting antitumor activity. The effects of different organotin types has been related to several mechanisms, including their ability to modify acetylation protein status and to promote apoptosis. Here, we focus on triorganotin(IV) complexes of butyric acid, a well-known HDAC inhibitor with antitumor properties. The conjugated compounds were synthesized and characterised by FTIR spectroscopy, multi-nuclear (1H, 13C and 119Sn) NMR, and mass spectrometry (ESI-MS). In the triorganotin(IV) complexes, an anionic monodentate butyrate ligand was observed, which coordinated the tin atom on a tetra-coordinated, monomeric environment similar to ester. FTIR and NMR findings confirm this structure both in solid state and solution. The antitumor efficacy of the triorganotin(IV) butyrates was tested in colon cancer cells and, among them, tributyltin(IV) butyrate (BT2) was selected as the most efficacious. BT2 induced G2/M cell cycle arrest, ER stress, and apoptotic cell death. These effects were obtained using low concentrations of BT2 up to 1 μM, whereas butyric acid alone was completely inefficacious, and the parent compound TBT was poorly effective at the same treatment conditions. To assess whether butyrate in the coordinated form maintains its epigenetic effects, histone acetylation was evaluated and a dramatic decrease in acetyl-H3 and -H4 histones was found. In contrast, butyrate alone stimulated histone acetylation at a higher concentration (5 mM). BT2 was also capable of preventing histone acetylation induced by SAHA, another potent HDAC inhibitor, thus suggesting that it may activate HDACs. These results support a potential use of BT2, a novel epigenetic modulator, in colon cancer treatment.

Implications of butyrate and its derivatives for gut health and animal production

Butyrate is produced by microbial fermentation in the large intestine of humans and animals. It serves as not only a primary nutrient that provides energy to colonocytes, but also a cellular mediator regulating multiple functions of gut cells and beyond, including gene expression, cell differentiation, gut tissue development, immune modulation, oxidative stress reduction, and diarrhea control. Although there are a large number of studies in human medicine using butyrate to treat intestinal disease, the importance of butyrate in maintaining gut health has also attracted significant research attention to its application for animal production, particularly as an alternative to in-feed antibiotics. Due to the difficulties of using butyrate in practice (i.e., offensive odor and absorption in the upper gut), different forms of butyrate, such as sodium butyrate and butyrate glycerides, have been developed and examined for their effects on gut health and growth performance across different species. Butyrate and its derivatives generally demonstrate positive effects on animal production, including enhancement of gut development, control of enteric pathogens, reduction of inflammation, improvement of growth performance (including carcass composition), and modulation of gut microbiota. These benefits are more evident in young animals, and variations in the results have been reported. The present article has critically reviewed recent findings in animal research on butyrate and its derivatives in regard to their effects and mechanisms behind and discussed the implications of these findings for improving animal gut health and production. In addition, significant findings of medical research in humans that are relevant to animal production have been cited.

Three measurable and modifiable enteric microbial biotransformations relevant to cancer prevention and treatment

Interdisciplinary scientific evaluation of the human microbiota has identified three enteric microbial biotransformations of particular relevance for human health and well-being, especially cancer. Two biotransformations are counterproductive; one is productive. First, selective bacteria can reverse beneficial hepatic hydroxylation to produce toxic secondary bile acids, especially deoxycholic acid. Second, numerous bacterial species can reverse hepatic detoxification-in a sense, retoxify hormones and xeonobiotics-by deglucuronidation. Third, numerous enteric bacteria can effect a very positive biotransformation through the production of butyrate, a small chain fatty acid with anti-cancer activity. Each biotransformation is addressed in sequence for its relevance in representative gastrointestinal and extra-intestinal cancers. This is not a complete review of their connection with every type of cancer. The intent is to introduce the reader to clinically relevant microbial biochemistry plus the emerging evidence that links these to both carcinogenesis and treatment. Included is the evidence base to guide counseling for potentially helpful dietary adjustments.

Butyrate: implications for intestinal function

PURPOSE OF REVIEW

Butyrate is physiologically produced by the microbial fermentation of dietary fibers and plays a plurifunctional role in intestinal cells. This review examines the recent findings regarding the role and mechanisms by which butyrate regulates intestinal metabolism and discusses how these findings could improve the treatment of several gastrointestinal disorders.

RECENT FINDINGS

Butyrate is more than a primary nutrient that provides energy to colonocytes and acts as a cellular mediator in those cells through several mechanisms. One remarkable property of butyrate is its ability to inhibit histone deacetylases, which is associated with the direct effects of butyrate and results in gene regulation, immune modulation, cancer suppression, cell differentiation, intestinal barrier regulation, oxidative stress reduction, diarrhea control, visceral sensitivity and intestinal motility modulation. All of these actions make butyrate an important factor for the maintenance of gut health.

SUMMARY

From studies published over 30 years, there is no doubt of the important role that butyrate plays in maintaining intestinal homeostasis. However, despite these effects, clinical studies are still required to validate the routine use of butyrate in clinical practice and, specifically, in the treatment of intestinal diseases.

Dairy milk fat augments paclitaxel therapy to suppress tumour metastasis in mice, and protects against the side-effects of chemotherapy

Milk fat is a natural product containing essential nutrients as well as fatty acids and other food factors with reported anti-cancer potential. Here bovine milk fat was tested for its ability to inhibit the growth of breast and colon cancers and their metastasis to the lung and liver; either alone or in combination with the chemotherapeutic agent paclitaxel. A diet containing 5% typical anhydrous milk fat (representing ~70% of the total dietary fat component) fed to Balb/c mice delayed the appearance of subcutaneous 4T1 breast and CT26 colon cancer tumours and inhibited their metastasis to the lung and liver, when compared to the control diet containing soybean oil as the only fat component. It augmented the inhibitory effects of paclitaxel on tumour growth and metastasis, and reduced the microvessel density of tumours. It displayed no apparent organ toxicity, but instead was beneficial for well-being of tumour-bearing mice by maintaining gastrocnemius muscle and epididymal adipose tissue that were otherwise depleted by cachexia. The milk fat diet ameliorated gut damage caused by paclitaxel in non-tumour-bearing mice, as evidenced by retention of jejunal morphology, villi length and intestinal γ-glutamyl transpeptidase activity, and inhibition of crypt apoptosis. It prevented loss of red and white blood cells due to both cancer-mediated immunosuppression and the cytotoxic effects of chemotherapy. The present study warrants the use of milk fat as an adjuvant to inhibit tumour metastasis during cancer chemotherapy, and to spare patients from the debilitating side-effects of cytotoxic drugs.

Histone deacetylase inhibitors: a new perspective for the treatment of leukemia

Histone deacetylase inhibitors (HDIs) promote or enhance several different anticancer mechanisms and therefore are in evidence as potential antileukemia agents. Studies on leukemia have provided examples for their functional implications in cancer development and progression, as well as their relevance for therapeutic targeting. A number of HDIs have been tested in clinical trials and have been proven safe with significant clinical activity. The use of HDIs in association with other molecules, such as classical chemotherapeutic drugs and DNA demethylating agents, has been implied as a promising treatment alternative for leukemia patients in the future. Here we describe the histone deacetylase inhibitors that have been tested in clinical trials for the treatment of leukemia and lymphoma. We conclude that further clinical trials involving a broader number of HDIs used either alone or in combination with other agents are needed to consolidate the use of these epigenetic modulators on leukemia therapy.

Characterisation of a carp cell line for analysis of apoptosis

Teleost fish in general, and common carp in particular, are excellent genetic models for bridging the gap in knowledge between invertebrate models such as C. elegans and D. melanogaster, on one hand, and higher vertebrates on the other hand, although, until now, there have been few well characterised fish cell lines shown to be suitable for studies on apoptosis. The present study describes the suitability of a permanent, nonleukemic, nonvirally infected carp cell line for apoptotic studies. A traditional approach using known apoptotic inducers such as UV-light combined with RNA interference, the latest ready-to-use technology widely used in higher vertebrates, was tested in the carp leucocyte cell line (CLC). This study was designed as a first step towards a better knowledge of fish macrophages and their fate after different types of apoptotic insults.

Sodium butyrate enhances the cytotoxic effect of antineoplastic drugs in human lymphoblastic T-cells

Sodium butyrate (NaB), a potent histone deacetylase inhibitor, induces cell cycle arrest and apoptosis in malignant cells. We investigated the effects on cellular proliferation in vitro when combining NaB with antineoplastic drugs commonly used to treat leukemias. Our results demonstrate that NaB increases the cytotoxic effects of cytarabine and etoposide, but not of bleomycin, doxorubicin, vincristine or methotrexate. These data suggest that NaB is a promising adjuvant therapeutic agent for the treatment of lymphoblastic leukemias, and provides a basis for further studies in this field.

Induction of Apoptosis by (Z)-Stellettic Acid C, an Acetylenic Acid from the Sponge Stelletta sp., Is Associated with Inhibition of Telomerase Activity in Human Leukemic U937 Cells

BACKGROUND

(Z)-stellettic acid C, an acetylenic acid from the marine sponge Stelletta sp., has been shown to have cytotoxic activity in some cancer cells; however, its mechanisms on malignant cell growth are not known. In this study, the potential of (Z)-stellettic acid C to induce apoptosis in human leukemic U937 cells and its effects on telomerase activity were investigated.

METHODS

Cytotoxicity was evaluated by MTT assays. Apoptosis was detected using DAPI staining and annexin V fluorescein. The mRNAs of Bcl-2, inhibitor of apoptosis proteins (IAPs) family and Fas/FasL system were determined by RT-PCR. Caspases and telomerase activities were measured using colorimetric assay and telomeric repeat amplification protocol enzyme-linked immunosorbent assay (TRAP-ELISA), respectively.

RESULTS

Exposure of U937 cells to (Z)-stellettic acid C resulted in growth inhibition and induction of apoptosis in a dose-dependent manner, which was associated with the modulation of Bcl-2 family expression, activation of caspases and downregulation of IAPs family members. (Z)-Stellettic acid C treatment markedly inhibited the activity of telomerase in a dose-dependent fashion. Additionally, the expression of human telomerase reverse transcriptase, a main determinant of the telomerase enzymatic activity, was progressively downregulated by (Z)-stellettic acid C treatment.

CONCLUSIONS

These results suggest that (Z)-stellettic acid C could have a possible cancer therapeutic potential.

Vinblastine, a chemotherapeutic drug, inhibits palmitoylation of tubulin in human leukemic lymphocytes

BACKGROUND

We have previously shown that tubulin, the major protein of microtubules, is posttranslationally modified by palmitoylation. In addition, we demonstrated that palmitoylation of tubulin is inhibited in vitro by stoichiometric levels of the chemotherapeutic drug, vinblastine. Here, we sought to determine whether a clinically relevant dose of vinblastine inhibits palmitoylation of tubulin in vivo.

METHODS

Human CEM leukemic lymphocytes were incubated with [3H]palmitate in the presence and absence of a low, clinically relevant dose of vinblastine. [3H]palmitoylated tubulin was identified by two-dimensional PAGE and autoradiography.

RESULTS

We found, first, that tubulin was palmitoylated in CEM cells. Second, the clinically relevant dose of vinblastine inhibited palmitoylation of tubulin in vivo in CEM cells. In addition, microtubules were disassembled and cells became apoptotic.

CONCLUSION

This study identifies a previously unknown mechanism of action of vinblastine, the depalmitoylation of tubulin, and suggests that depalmitoylation of tubulin may be a target for new chemotherapeutic drugs.

In vitro induction of apoptosis in U937 cells by perillyl alcohol with sensitization by pentoxifylline: increased BCL-2 and BAX protein expression

BACKGROUND

Chemotherapy is effective against a wide variety of tumor cells, although its use is limited by side effects. In vitro experiments and phase I and II trials have shown that phytochemicals such as perillyl alcohol (P-OH) have antitumor effects. Pentoxifylline (PTX), a synthetic methylxanthine used mainly to treat pathologies associated with hematological diseases, sensitizes tumor cells to chemotherapy. The aim of this study was to determine whether PTX amplifies the antitumor effects of P-OH in U937 human myelomonocytic leukemia cells.

METHODS

Apoptosis was measured by the loss of mitochondrial membrane potential determined by flow cytometry using dihexyloxacarbocyanine iodide (DiOC6) and propidium iodide. Bcl-2 and Bax protein expression was also assessed by Western blot analysis.

RESULTS

P-OH and PTX induced loss of the mitochondrial membrane potential in U937 cells in vitro. Culturing the cells in the presence of both compounds caused a significant increase (p < 0.001) in apoptosis and expression of anti-apoptotic Bcl-2 and pro-apoptotic Bax proteins. However, despite their coexistence, Bax expression prevailed in our experiments. These data suggest that the effects of PTX might be attributable to changes in the mitochondrial membrane potential.

CONCLUSION

PTX sensitizes tumor cells to the anti-neoplastic action of P-OH. These observations may have clinical relevance in the treatment of cancer patients.

Differential susceptibility to etoposide in clones derived from a human ovarian cancer cell line

OBJECTIVES

To identify parameters/factors that may contribute to the differential sensitivity to etoposide in two clones isolated from the human ovarian carcinoma SKOV-3 cell line, which does not express p53 and is resistant to platinum-based regimens.

METHODS

Differential sensitivity of the cells to etoposide was monitored by microscopy to observe morphological changes, by flow cytometry analyses to detect cell cycle perturbations, and by molecular/biochemical assays to identify events involved in induction of apoptosis.

RESULTS

Etoposide treatment (1) induced apoptosis in one clone, ES, but not in another clone, ER, (2) had no effect on the expression of the antiapoptotic proteins Bcl-2 and Bcl-X(L) in both cell clones, whereas the proapoptotic proteins Bak and Bax were dramatically upregulated in ES, but not ER cells, and (3) induced more extensive processing of procaspase-8, procaspase-9, and the caspase-3-targeted substrates, topoisomerase I and PARP, in ES cells. Ectopic overexpression of Bcl-2 in ES cells failed to inhibit etoposide-induced apoptosis.

CONCLUSIONS

The differential susceptibility of ES and ER cells to etoposide-induced apoptosis is associated with differences in several events rather than with a specific single genetic regulator of the apoptotic machinery. We propose that the differential response of ovarian cancer patients to etoposide treatment is associated with the number of etoposide-sensitive cells in the tumor.