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.

Bioaccessibility of avocado polyhydroxylated fatty alcohols.

Avocado-derived polyhydroxylated fatty alcohols (PFAs), such as avocadene and avocadyne, have been recently identified as potent modulators of mitochondrial metabolism which selectively induce leukemia cell death and reverse pathologies associated with diet-induced obesity. However, avocadene and avocadyne bioaccessibility from avocado pulp is not reported; hence, this study aims to investigate if these PFAs are bioaccessible. Dynamic (TNO dynamic intestinal model-1 (TIM-1)) and static in vitro digestion of lyophilized Hass avocado pulp powder shows lipolytic gastrointestinal enzymes led to appreciable bioaccessibility of avocadene (55%) and avocadyne (50%). Furthermore, TIM-1 digestion of a 1:1 ratio of pure avocadene and avocadyne (avocatin B or AvoB) crystals formulated in an oil-in-water microemulsion has on average 15% higher bioaccessibility than the avocado pulp powder demonstrating both dosage forms as potential dietary sources of avocado PFAs. This research provides the impetus for further research on the nutritional significance of dietary long chain fatty alcohols.

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.