Pseudolaric Acid B Targets CD147 to Selectively Kill Acute Myeloid Leukemia Cells.

Acute myeloid leukemia (AML) is an aggressive blood cancer. With low survival rates, new drug targets are needed to improve treatment regimens and patient outcomes. Pseudolaric acid B (PAB) is a plant-derived bioactive compound predicted to interact with cluster of differentiation 147 (CD147/BSG). CD147 is a transmembrane glycoprotein overexpressed in various malignancies with suggested roles in regulating cancer cell survival, proliferation, invasion, and apoptosis. However, the detailed function of PAB in AML remains unknown. In this study, AML cell lines and patient-derived cells were used to show that PAB selectively targeted AML (IC50: 1.59 ± 0.47 µM). Moreover, proliferation assays, flow cytometry, and immunoblotting confirmed that PAB targeting of CD147 resulted in AML cell apoptosis. Indeed, the genetic silencing of CD147 significantly suppressed AML cell growth and attenuated PAB activity. Overall, PAB imparts anti-AML activity through transmembrane glycoprotein CD147.

Very long chain fatty acid metabolism is required in acute myeloid leukemia.

Acute myeloid leukemia (AML) cells have an atypical metabolic phenotype characterized by increased mitochondrial mass, as well as a greater reliance on oxidative phosphorylation and fatty acid oxidation (FAO) for survival. To exploit this altered metabolism, we assessed publicly available databases to identify FAO enzyme overexpression. Very long chain acyl-CoA dehydrogenase (VLCAD; ACADVL) was found to be overexpressed and critical to leukemia cell mitochondrial metabolism. Genetic attenuation or pharmacological inhibition of VLCAD hindered mitochondrial respiration and FAO contribution to the tricarboxylic acid cycle, resulting in decreased viability, proliferation, clonogenic growth, and AML cell engraftment. Suppression of FAO at VLCAD triggered an increase in pyruvate dehydrogenase activity that was insufficient to increase glycolysis but resulted in adenosine triphosphate depletion and AML cell death, with no effect on normal hematopoietic cells. Together, these results demonstrate the importance of VLCAD in AML cell biology and highlight a novel metabolic vulnerability for this devastating disease.

Diosmetin Induces Apoptosis of Acute Myeloid Leukemia Cells.

Acute myeloid leukemia is an aggressive disease with limited and nonselective therapeutic options. This study explored the bioactivity and cell death inducing mechanism of diosmetin, a novel compound identified in a nutraceutical screen to impart selective anti-AML activity. Diosmetin, a citrus flavone, induced apoptosis characterized by increases in caspases 8 and 3/7 and the death inducing cytokine TNFα. In fact, through protein and mRNA expression analysis, activity was shown to be dependent on expression of estrogen receptor (ER) ß. Treatment with diosmetin also delayed tumor growth in AML mouse xenografts. In summary, these studies highlight diosmetin as a novel therapeutic that induces apoptosis through estrogen receptor ß.

Analytical Method To Detect and Quantify Avocatin B in Hass Avocado Seed and Pulp Matter.

Avocatin B, an avocado-derived compound mixture, was demonstrated recently to possess potent anticancer activity by selectively targeting and eliminating leukemia stem cells. Avocatin B is a mixture of avocadene and avocadyne, two 17-carbon polyhydroxylated fatty alcohols (PFAs), first discovered in avocado seeds; their quantities in avocado pulp are unknown. Analytical methods to detect avocado seed PFAs have utilized NMR spectroscopy and GC-MS; both of these lack quantitative capacity and accuracy. Herein, we report a sensitive LC-MS method for the quantitation of avocadene and avocadyne in avocado seed and pulp. The method has a reliable and linear response range of 0.1-50 µM (0.03-17.2 ng/µL) for both avocadene and avocadyne ( r2 > 0.990) with a lower limit of quantitation (LLOQ) of 0.1 µM. The intra- and interassay accuracy and precision of the quality control (QC) samples at LLOQ showed ≤18.2% percentage error and ≤14.4% coefficient of variation (CV). The intra- and interassay accuracy and precision for QC samples at low and high concentrations were well below 10% error and CV. This method was successfully applied to quantify avocadene and avocadyne in total lipid extracts of Hass avocado pulp and seed matter.

Mitochondrial DNA damage by bleomycin induces AML cell death.

Mitochondria contain multiple copies of their own 16.6 kb circular genome. To explore the impact of mitochondrial DNA (mtDNA) damage on mitochondrial (mt) function and viability of AML cells, we screened a panel of DNA damaging chemotherapeutic agents to identify drugs that could damage mtDNA. We identified bleomycin as an agent that damaged mtDNA in AML cells at concentrations that induced cell death. Bleomycin also induced mtDNA damage in primary AML samples. Consistent with the observed mtDNA damage, bleomycin reduced mt mass and basal oxygen consumption in AML cells. We also demonstrated that the observed mtDNA damage was functionally important for bleomycin-induced cell death. Finally, bleomycin delayed tumor growth in xenograft mouse models of AML and anti-leukemic concentrations of the drug induced mtDNA damage in AML cells preferentially over normal lung tissue. Taken together, mtDNA-targeted therapy may be an effective strategy to target AML cells and bleomycin could be useful in the treatment of this disease.

Chemotherapeutic agents attenuate CXCL12-mediated migration of colon cancer cells by selecting for CXCR4-negative cells and increasing peptidase CD26.

BACKGROUND: Recurrence of colorectal cancer (CRC) may arise due to the persistence of drug-resistant and cancer-initiating cells that survive exposure to chemotherapy. Proteins responsible for this recurrence include the chemokine receptor CXCR4, which is known to enable CRC metastasis, as well as the cancer-initiating cell marker and peptidase CD26, which terminates activity of its chemokine CXCL12. METHODS: We evaluated the expression and function of CXCR4 and CD26 in colon cancer cell lines and xenografts following treatment with common chemotherapies using radioligand binding, flow cytometry, immunofluorescence, and enzymatic assays. RESULTS: 5-Fluorouracil, oxaliplatin and SN-38 (the active metabolite of irinotecan), as well as cisplatin, methotrexate and vinblastine, each caused decreases in cell-surface CXCR4 and concomitant increases in CD26 on HT-29, T84, HRT-18, SW480 and SW620 CRC cell lines. Flow cytometry indicated that the decline in CXCR4 was associated with a significant loss of CXCR4+/CD26- cells. Elevations in CD26 were paralleled by increases in both the intrinsic dipeptidyl peptidase activity of CD26 as well as its capacity to bind extracellular adenosine deaminase. Orthotopic HT-29 xenografts treated with standard CRC chemotherapeutics 5-fluorouracil, irinotecan, or oxaliplatin showed dramatic increases in CD26 compared to untreated tumors. Consistent with the loss of CXCR4 and gain in CD26, migratory responses to exogenous CXCL12 were eliminated in cells pretreated with cytotoxic agents, although cells retained basal motility. Analysis of cancer-initiating cell CD44 and CD133 subsets revealed drug-dependent responses of CD26/CD44/CD133 populations, suggesting that the benefits of combining standard chemotherapies 5-fluoruracil and oxaliplatin may be derived from their complementary elimination of cell populations. CONCLUSION: Our results indicate that conventional anticancer agents may act to inhibit chemokine-mediated migration through eradication of CXCR4+ cells and attenuation of chemokine gradients through elevation of CD26 activity.

New sources of drugs for hematologic malignancies.

Advancing novel therapeutic agents for the treatment of malignancy into the marketplace is an increasingly costly and lengthy process. As such, new strategies for drug discovery are needed. Drug repurposing represents an opportunity to rapidly advance new therapeutic strategies into clinical trials at a relatively low cost. Known on-patent or off-patent drugs with unrecognized anticancer activity can be rapidly advanced into clinical testing for this new indication by leveraging their known pharmacology, pharmacokinetics, and toxicology. Using this approach, academic groups can participate in the drug discovery field and smaller biotechnology companies can "de-risk" early-stage drug discovery projects. Here, several scientific approaches used to identify drug repurposing opportunities are highlighted, with a focus on hematologic malignancies. In addition, a discussion of the regulatory issues that are unique to drug repurposing and how they impact developing old drugs for new indications is included. Finally, the mechanisms to enhance drug repurposing through increased collaborations between academia, industry, and nonprofit charitable organizations are discussed.

A small-molecule inhibitor of D-cyclin transactivation displays preclinical efficacy in myeloma and leukemia via phosphoinositide 3-kinase pathway.

D-cyclins are universally dysregulated in multiple myeloma and frequently overexpressed in leukemia. To better understand the role and impact of dysregulated D-cyclins in hematologic malignancies, we conducted a high-throughput screen for inhibitors of cyclin D2 transactivation and identified 8-ethoxy-2-(4-fluorophenyl)-3-nitro-2H-chromene (S14161), which inhibited the expression of cyclins D1, D2, and D3 and arrested cells at the G(0)/G(1) phase. After D-cyclin suppression, S14161 induced apoptosis in myeloma and leukemia cell lines and primary patient samples preferentially over normal hematopoietic cells. In mouse models of leukemia, S14161 inhibited tumor growth without evidence of weight loss or gross organ toxicity. Mechanistically, S14161 inhibited the activity of phosphoinositide 3-kinase in intact cells and the activity of the phosphoinositide 3-kinases α, ß, δ, and γ in a cell-free enzymatic assay. In contrast, it did not inhibit the enzymatic activities of other related kinases, including the mammalian target of rapamycin, the DNA-dependent protein kinase catalytic subunit, and phosphoinositide-dependent kinase-1. Thus, we identified a novel chemical compound that inhibits D-cyclin transactivation via the phosphoinositide 3-kinase/protein kinase B signaling pathway. Given its potent antileukemia and antimyeloma activity and minimal toxicity, S14161 could be developed as a novel agent for blood cancer therapy.

A 2,6,9-hetero-trisubstituted purine inhibitor exhibits potent biological effects against multiple myeloma cells.

A focused library of hetero-trisubstituted purines was developed for improving the cell penetrating and biological efficacy of a series of anti-Stat3 protein inhibitors. From this SAR study, lead agent 22e was identified as being a promising inhibitor of MM tumour cells (IC50's <5µM). Surprisingly, biophysical and biochemical characterization proved that 22e was not a Stat3 inhibitor. Initial screening against the kinome, prompted by the purine scaffold's history for targeting ATP binding pockets, suggests possible targeting of the JAK family kinases, as well for ABL1 (nonphosphorylated F317L) and AAK1.

The antihelmintic flubendazole inhibits microtubule function through a mechanism distinct from Vinca alkaloids and displays preclinical activity in leukemia and myeloma.

On-patent and off-patent drugs with previously unrecognized anticancer activity could be rapidly repurposed for this new indication given their prior toxicity testing. To identify such compounds, we conducted chemical screens and identified the antihelmintic flubendazole. Flubendazole induced cell death in leukemia and myeloma cell lines and primary patient samples at nanomolar concentrations. Moreover, it delayed tumor growth in leukemia and myeloma xenografts without evidence of toxicity. Mechanistically, flubendazole inhibited tubulin polymerization by binding tubulin at a site distinct from vinblastine. In addition, cells resistant to vinblastine because of overexpression of P-glycoprotein remained fully sensitive to flubendazole, indicating that flubendazole can overcome some forms of vinblastine resistance. Given the different mechanisms of action, we evaluated the combination of flubendazole and vinblastine in vitro and in vivo. Flubendazole synergized with vinblastine to reduce the viability of OCI-AML2 cells. In addition, combinations of flubendazole with vinblastine or vincristine in a leukemia xenograft model delayed tumor growth more than either drug alone. Therefore, flubendazole is a novel microtubule inhibitor that displays preclinical activity in leukemia and myeloma.

Avocado-derived avocadyne is a potent inhibitor of fatty acid oxidation.

Avocatin-B (Avo-B), an avocado-derived 1:1 mixture of the polyhydroxylated alcohols avocadyne (AYNE) and avocadene, eliminated leukemia cells by suppressing fatty acid oxidation (FAO) in vivo and in vitro while sparing healthy blood cells. In this study, we identified AYNE as the most potent FAO inhibitor within the Avo-B mixture capable of inducing cell death in leukemia cells lines (IC50 : 3.10 ± 0.14 µM in TEX cells; 11.53 ± 3.32 µM in OCI-AML2) and patient-derived acute myeloid leukemia cells. When added individually, the two Avo-B constituents demonstrated antagonism (Combination Index values >1), highlighting the need for future studies to assess AYNE alone. Together, this work highlighted AYNE as the most potent FAO inhibitor within the Avo-B mixture. PRACTICAL APPLICATIONS: This work identifies which of the two molecules in avocatin B (Avo-B), an avocado-derived mixture of two molecules with demonstrated human safety, utility against leukemia, insulin resistance and diabetes, is most useful. Therefore, it provides the basis for future clinical studies that will focus on testing and developing the most active Avo-B constituent.

Novel Mango Ginger Bioactive (2,4,6-Trihydroxy-3,5-diprenyldihydrochalcone) Inhibits Mitochondrial Metabolism in Combination with Avocatin B.

Acute myeloid leukemia (AML) is an aggressive blood cancer with limited effective chemotherapy options and negative patient outcomes. Food-derived molecules such as avocatin B (Avo B), a fatty-acid oxidation (FAO) inhibitor, are promising novel therapeutics. The roots of the Curcuma amada plants have been historically used in traditional medicine, but isolated bioactive compounds have seldom been studied. Here, we report that 2,4,6-trihydroxy-3,5-diprenyldihydrochalcone (M1), a bioactive from C. Amada, possesses novel anticancer activity. This in vitro study investigated the antileukemia properties of M1 and its effects on mitochondrial metabolism. In combination with Avo B, M1 synergistically reduced AML cell line viability and patient-derived clonogenic growth with no effect on normal peripheral blood stem cells. Mechanistically, M1 alone inhibited mitochondria complex I, while the M1/Avo B combination inhibited FAO by 60%, a process essential to the synergy. These results identified a novel food-derived bioactive and its potential as a novel chemotherapeutic for AML.

Glutamine Metabolism Mediates Sensitivity to Respiratory Complex II Inhibition in Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is a hematologic malignancy metabolically dependent on oxidative phosphorylation and mitochondrial electron transport chain (ETC) activity. AML cells are distinct from their normal hematopoietic counterparts by this metabolic reprogramming, which presents targets for new selective therapies. Here, metabolic changes in AML cells after ETC impairment are investigated. Genetic knockdown of the ETC complex II (CII) chaperone protein SDHAF1 (succinate dehydrogenase assembly factor 1) suppressed CII activity and delayed AML cell growth in vitro and in vivo. As a result, a novel small molecule that directly binds to the ubiquinone binding site of CII and inhibits its activity was identified. Pharmacologic inhibition of CII induced selective death of AML cells while sparing normal hematopoietic progenitors. Through stable isotope tracing, results show that genetic or pharmacologic inhibition of CII truncates the tricarboxylic acid cycle (TCA) and leads to anaplerotic glutamine metabolism to reestablish the truncated cycle. The inhibition of CII showed divergent fates, as AML cells lacked the metabolic plasticity to adequately utilize glutamine metabolism, resulting in preferential depletion of key TCA metabolites and death; normal cells were unaffected. These findings provide insight into the metabolic mechanisms that underlie AML's selective inhibition of CII. IMPLICATIONS: This work highlights the effects of direct CII inhibition in mediating selective AML cell death and provides insights into glutamine anaplerosis as a metabolic adaptation that can be therapeutically targeted.

Structure-activity relationship of avocadyne.

Avocado consumption is associated with numerous health benefits. Avocadyne is a terminally unsaturated, 17-carbon long acetogenin found almost exclusively in avocados with noted anti-leukemia and anti-viral properties. In this study, specific structural features such as the terminal triple bond, odd number of carbons, and stereochemistry are shown to be critical to its ability to suppress mitochondrial fatty acid oxidation and impart selective activity in vitro and in vivo. Together, this is the first study to conduct a structure-activity analysis on avocadyne and outline the chemical moieties critical to fatty acid oxidation suppression.

Estrogen Receptors Alpha and Beta in Acute Myeloid Leukemia.

Estrogen receptor (ER) signaling has been widely studied in a variety of solid tumors, where the differential expression of ERα and ERß subtypes can impact prognosis. ER signaling has only recently emerged as a target of interest in acute myeloid leukemia (AML), an aggressive hematological malignancy with sub-optimal therapeutic options and poor clinical outcomes. In a variety of tumors, ERα activation has proliferative effects, while ERß targeting results in cell senescence or death. Aberrant ER expression and hypermethylation have been characterized in AML, making ER targeting in this disease of great interest. This review describes the expression patterns of ERα and ERß in AML and discusses the differing signaling pathways associated with each of these receptors. Furthermore, we assess how these signaling pathways can be targeted by various selective estrogen receptor modulators to induce AML cell death. We also provide insight into ER targeting in AML and discuss pending questions that require further study.

Avocado-derived polyols for use as novel co-surfactants in low energy self-emulsifying microemulsions.

Avocado (Persea americana Mill.; Lauraceae) seed-derived polyhydroxylated fatty alcohols (PFAs) or polyols (i.e., avocadene and avocadyne) are metabolic modulators that selectively induce apoptosis of leukemia stem cells and reverse pathologies associated with diet-induced obesity. Delivery systems containing avocado polyols have not been described. Herein, natural surface active properties of these polyols are characterized and incorporated into self-emulsifying drug delivery systems (SEDDS) that rely on molecular self-assembly to form fine, transparent, oil-in-water (O/W) microemulsions as small as 20 nanometers in diameter. Mechanistically, a 1:1 molar ratio of avocadene and avocadyne (i.e., avocatin B or AVO was shown to be a eutectic mixture which can be employed as a novel, bioactive, co-surfactant that significantly reduces droplet size of medium-chain triglyceride O/W emulsions stabilized with polysorbate 80. In vitro cytotoxicity of avocado polyol-SEDDS in acute myeloid leukemia cell lines indicated significant increases in potency and bioactivity compared to conventional cell culture delivery systems. A pilot pharmacokinetic evaluation of AVO SEDDS in C57BL/6J mice revealed appreciable accumulation in whole blood and biodistribution in key target tissues. Lastly, incorporation of AVO in SEDDS significantly improved encapsulation of the poorly water-soluble drugs naproxen and curcumin.

Knockdown of BNIP3L or SQSTM1 alters cellular response to mitochondria target drugs.

Macroautophagy/autophagy, a pathway by which cellular components are sequestered and degraded in response to homeostatic and cell stress-related signals, is required to preserve hematopoietic stem and progenitor cell function. Loss of chromosomal regions carrying autophagy genes and decreased autophagy gene expression are characteristic of acute myeloid leukemia (AML) cells. Deficiency of autophagy proteins is also linked to an altered AML metabolic profile; altered metabolism has recently emerged as a potential druggable target in AML. Here, we sought to understand the mitochondria-specific changes that occur in leukemia cells after knockdown of BNIP3L/Nix or SQSTM1/p62, which are two autophagy genes involved in mitochondrial clearance and are downregulated in primary AML cells. Mitochondrial function, as measured by changes in endogenous levels of reactive oxygen species (ROS) and mitochondrial membrane potential, was altered in leukemia cells deficient in these autophagy genes. Further, these AML cells were increasingly sensitive to mitochondria-targeting drugs while displaying little change in sensitivity to DNA-targeting agents. These findings suggest that BNIP3L or SQSTM1 may be useful prognostic markers to identify AML patients suitable for mitochondria-targeted therapies. Abbreviations: AML: acute myeloid leukemia; DHE: dihydroethidium; mtDNA: mitochondrial DNA; NAO: 10-N-nonyl acridine orange; PD: population doubling; R123: rhodamine 123; ROS: reactive oxygen species; TRC: transduced scramble controls.

Avocatin B Protects Against Lipotoxicity and Improves Insulin Sensitivity in Diet-Induced Obesity.

SCOPE: The effects of an avocado-derived fatty acid oxidation (FAO) inhibitor, avocatin B (AvoB), on glucose and lipid metabolism in models of diet-induced obesity (DIO) and in vitro models of lipotoxicity are evaluated. The safety of its oral consumption in humans is also determined. METHODS AND RESULTS: Mice are given high-fat diets (HFD) for 8 weeks. Thereafter, AvoB or vehicle is administered orally twice weekly for 5 weeks. AvoB inhibits FAO which led to improved glucose tolerance, glucose utilization, and insulin sensitivity. AvoB's effects on metabolism under lipotoxic conditions are evaluated in vitro in pancreatic ß-islet cells and C2C12 myotubes. AvoB inhibits FAO and increases glucose oxidation, resulting in lowering of mitochondrial reactive oxygen species that improves insulin responsiveness in C2C12 myotubes and insulin secretion in INS-1 (832/13) cells, respectively. A randomized, double-blind, placebo-controlled clinical trial in healthy human participants is conducted to assess the safety of AvoB consumption (50 mg or 200 mg per day for 60 days). AvoB is well-tolerated and not associated with any dose-limiting toxicity. CONCLUSION: Therapeutic agents that are safe and effectively inhibit FAO and improve DIO-associated pathologies are currently not available. AvoB's mechanism of action and favorable safety profile highlight its nutritional and clinical importance.

Dietary lactoferrin does not prevent dextran sulfate sodium induced murine intestinal lymphocyte death.

Dextran sulfate sodium (DSS) induced intestinal inflammation is characterized by pronounced mucosal and epithelial cell damage. Bovine lactoferrin (bLf), a common dietary protein, influences inflammatory cytokines and intestinal lymphocyte (IL) apoptosis. The objectives of this study were to determine if 1) DSS induces IL necrotic or apoptotic death, 2) dietary bLf affects DSS induced IL death and 3) bLf alters cytokine profiles during DSS induced inflammation. Female C57BL/6 mice were randomized to 2% or 0% bLf diets for 12 d and within diets to 5% or 0% DSS in the drinking water for 4 d after which intestinal histology, IL number, IL apoptosis/necrosis, IL phenotypes, protein levels of pro-inflammatory cytokine (TNF-alpha) and transcription factor (NFkappaB), apoptotic (caspase 3, Bax) proteins, anti-inflammatory cytokine (IL-10) and anti-apoptotic (Bcl-2) protein in IL were evaluated. DSS treatment resulted in shortened intestinal length, decreased body weight and widespread mucosal damage as well as increased IL death as determined by a decreased percentage of viable (PI-/ANN-, P<0.005) and increased percentage of necrotic/late apoptotic (PI+/ ANN+, P<0.05) and necrotic (PI+/ANN-, P<0.05) IL. DSS exposure increased caspase 3 (P<0.05) and decreased Bcl-2 (P<0.01) protein levels in mouse IL. Dietary bLf did not influence these cell death outcome measures. However, bLf reduced protein levels of the pro-inflammatory transcription factor, NFkappaB, in IL (P<0.05) and was associated with a 34%, albeit non-significant, reduction in TNF-alpha relative to non-bLf fed mice. DSS treatment increased apoptosis and necrosis of mouse IL and elevated pro-apoptotic and reduced anti-apoptotic protein levels in these cells. Dietary bLf did not influence necrosis or apoptosis of IL but may provide limited protection in the intestine by affecting the pro-inflammatory transcription factor NFkappaB, and potentially, cytokine expression.

Lactoferrin effect on lymphocyte cytokines and apoptosis is independent of exercise.

BACKGROUND: Strenuous exercise increases apoptosis of intestinal lymphocytes (IL). Bovine lactoferrin (bLf), a protein found in milk products, affects lymphocyte apoptosis and the expression of TH1 and TH2 cytokines. OBJECTIVE: The purpose was to determine whether bLf affects apoptosis and TH1 (tumor necrosis factor alpha) and TH2 (interleukin-10) cytokine expression in IL of mice given strenuous exercise. METHODS: : Female C57BL/6 mice (n = 89), given three bouts of treadmill exercise, were killed either immediately, 24 h after the last bout, or before initiation of exercise; within exercise conditions, mice were fed control (0% bLf) or bLf-supplemented (2% bLf) diet for 12 d until sacrifice. IL were enumerated, and apoptosis and cytokine expression were determined by Western blot analysis; markers of stress (corticosterone and iso-prostanes) were measured in the plasma by radioimmunoassay and direct immunoassay. RESULTS: Exercise increased IL loss (P < 0.05) and the expression of caspase 3 (P < 0.001), heat shock protein 70 (P < 0.01), and interleukin-10 (P < 0.05) in mouse IL; bLf did not alter these responses. However, bLf reduced tumor necrosis factor alpha expression in mouse IL (P < 0.05), possibly through decreased nuclear factor kappaB expression (P < 0.05) in the supplemented group. CONCLUSIONS: Dietary bLf does not affect IL apoptosis after exercise but may confer intestinal protection through changes in cytokine expression, independent of exercise.