Alterations in sphingolipid composition and mitochondrial bioenergetics represent synergistic therapeutic vulnerabilities linked to multidrug resistance in leukemia.

Modifications in sphingolipid (SL) metabolism and mitochondrial bioenergetics are key factors implicated in cancer cell response to chemotherapy, including chemotherapy resistance. In the present work, we utilized acute myeloid leukemia (AML) cell lines, selected to be refractory to various chemotherapeutics, to explore the interplay between SL metabolism and mitochondrial biology supportive of multidrug resistance (MDR). In agreement with previous findings in cytarabine or daunorubicin resistant AML cells, relative to chemosensitive wildtype controls, HL-60 cells refractory to vincristine (HL60/VCR) presented with alterations in SL enzyme expression and lipidome composition. Such changes were typified by upregulated expression of various ceramide detoxifying enzymes, as well as corresponding shifts in ceramide, glucosylceramide, and sphingomyelin (SM) molecular species. With respect to mitochondria, despite consistent increases in both basal respiration and maximal respiratory capacity, direct interrogation of the oxidative phosphorylation (OXPHOS) system revealed intrinsic deficiencies in HL60/VCR, as well as across multiple MDR model systems. Based on the apparent requirement for augmented SL and mitochondrial flux to support the MDR phenotype, we explored a combinatorial therapeutic paradigm designed to target each pathway. Remarkably, despite minimal cytotoxicity in peripheral blood mononuclear cells (PBMC), co-targeting SL metabolism, and respiratory complex I (CI) induced synergistic cytotoxicity consistently across multiple MDR leukemia models. Together, these data underscore the intimate connection between cellular sphingolipids and mitochondrial metabolism and suggest that pharmacological intervention across both pathways may represent a novel treatment strategy against MDR.

Nervonic acid limits weight gain in a mouse model of diet-induced obesity.

Lipid perturbations contribute to detrimental outcomes in obesity. We previously demonstrated that nervonic acid, a C24:1 ω-9 fatty acid, predominantly acylated to sphingolipids, including ceramides, are selectively reduced in a mouse model of obesity. It is currently unknown if deficiency of nervonic acid-sphingolipid metabolites contribute to complications of obesity. Mice were fed a standard diet, a high fat diet, or these diets supplemented isocalorically with nervonic acid. The primary objective was to determine if dietary nervonic acid content alters the metabolic phenotype in mice fed a high fat diet. Furthermore, we investigated if nervonic acid alters markers of impaired fatty acid oxidation in the liver. We observed that a nervonic acid-enriched isocaloric diet reduced weight gain and adiposity in mice fed a high fat diet. The nervonic acid enrichment led to increased C24:1-ceramides and improved several metabolic parameters including blood glucose levels, and insulin and glucose tolerance. Mechanistically, nervonic acid supplementation increased PPARα and PGC1α expression and improved the acylcarnitine profile in liver. These alterations indicate improved energy metabolism through increased ß-oxidation of fatty acids. Taken together, increasing dietary nervonic acid improves metabolic parameters in mice fed a high fat diet. Strategies that prevent deficiency of, or restore, nervonic acid may represent an effective strategy to treat obesity and obesity-related complications.

Chemotherapy selection pressure alters sphingolipid composition and mitochondrial bioenergetics in resistant HL-60 cells.

The combination of daunorubicin (dnr) and cytarabine (Ara-C) is a cornerstone of treatment for acute myelogenous leukemia (AML); resistance to these drugs is a major cause of treatment failure. Ceramide, a sphingolipid (SL), plays a critical role in cancer cell apoptosis in response to chemotherapy. Here, we investigated the effects of chemotherapy selection pressure with Ara-C and dnr on SL composition and enzyme activity in the AML cell line HL-60. Resistant cells, those selected for growth in Ara-C- and dnr-containing medium (HL-60/Ara-C and HL-60/dnr, respectively), demonstrated upregulated expression and activity of glucosylceramide synthase, acid ceramidase (AC), and sphingosine kinase 1 (SPHK1); were more resistant to ceramide than parental cells; and displayed sensitivity to inhibitors of SL metabolism. Lipidomic analysis revealed a general ceramide deficit and a profound upswing in levels of sphingosine 1-phosphate (S1P) and ceramide 1-phosphate (C1P) in HL-60/dnr cells versus parental and HL-60/Ara-C cells. Both chemotherapy-selected cells also exhibited comprehensive upregulations in mitochondrial biogenesis consistent with heightened reliance on oxidative phosphorylation, a property that was partially reversed by exposure to AC and SPHK1 inhibitors and that supports a role for the phosphorylation system in resistance. In summary, dnr and Ara-C selection pressure induces acute reductions in ceramide levels and large increases in S1P and C1P, concomitant with cell resilience bolstered by enhanced mitochondrial remodeling. Thus, strategic control of ceramide metabolism and further research to define mitochondrial perturbations that accompany the drug-resistant phenotype offer new opportunities for developing therapies that regulate cancer growth.

Therapeutic Effect of Blueberry Extracts for Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is an aggressive hematological malignancy with high incidence in the aging population. In addition, AML is one of the more common pediatric malignancies. Unfortunately, both of these patient groups are quite sensitive to chemotherapy toxicities. Investigation of blueberries specifically as an anti-AML agent has been limited, despite being a prominent natural product with no reported toxicity. In this study, blueberry extracts are reported for the first time to exert a dietary therapeutic effect in animal models of AML. Furthermore, in vitro studies revealed that blueberry extracts exerted anti-AML efficacy against myeloid leukemia cell lines as well as against primary AML, and specifically provoked Erk and Akt regulation within the leukemia stem cell subpopulation. This study provides evidence that blueberries may be unique sources for anti-AML biopharmaceutical compound discovery, further warranting fractionation of this natural product. More so, blueberries themselves may provide an intriguing dietary option to enhance the anti-AML efficacy of traditional therapy for subsets of patients that otherwise may not tolerate rigorous combinations of therapeutics.

Ceramide-tamoxifen regimen targets bioenergetic elements in acute myelogenous leukemia.

The objective of our study was to determine the mechanism of action of the short-chain ceramide analog, C6-ceramide, and the breast cancer drug, tamoxifen, which we show coactively depress viability and induce apoptosis in human acute myelogenous leukemia cells. Exposure to the C6-ceramide-tamoxifen combination elicited decreases in mitochondrial membrane potential and complex I respiration, increases in reactive oxygen species (ROS), and release of mitochondrial proapoptotic proteins. Decreases in ATP levels, reduced glycolytic capacity, and reduced expression of inhibitors of apoptosis proteins also resulted. Cytotoxicity of the drug combination was mitigated by exposure to antioxidant. Cells metabolized C6-ceramide by glycosylation and hydrolysis, the latter leading to increases in long-chain ceramides. Tamoxifen potently blocked glycosylation of C6-ceramide and long-chain ceramides. N-desmethyltamoxifen, a poor antiestrogen and the major tamoxifen metabolite in humans, was also effective with C6-ceramide, indicating that traditional antiestrogen pathways are not involved in cellular responses. We conclude that cell death is driven by mitochondrial targeting and ROS generation and that tamoxifen enhances the ceramide effect by blocking its metabolism. As depletion of ATP and targeting the "Warburg effect" represent dynamic metabolic insult, this ceramide-containing combination may be of utility in the treatment of leukemia and other cancers.

Modification of sphingolipid metabolism by tamoxifen and N-desmethyltamoxifen in acute myelogenous leukemia--Impact on enzyme activity and response to cytotoxics.

The triphenylethylene antiestrogen, tamoxifen, can be an effective inhibitor of sphingolipid metabolism. This off-target activity makes tamoxifen an interesting ancillary for boosting the apoptosis-inducing properties of ceramide, a sphingolipid with valuable tumor censoring activity. Here we show for the first time that tamoxifen and metabolite, N-desmethyltamoxifen (DMT), block ceramide glycosylation and inhibit ceramide hydrolysis (by acid ceramidase, AC) in human acute myelogenous leukemia (AML) cell lines and in AML cells derived from patients. Tamoxifen (1-10 µM) inhibition of AC in AML cells was accompanied by decreases in AC protein expression. Tamoxifen also depressed expression and activity of sphingosine kinase 1 (SphK1), the enzyme-catalyzing production of mitogenic sphingosine 1-phosphate (S1-P). Results from mass spectroscopy showed that tamoxifen and DMT (i) increased the levels of endogenous C16:0 and C24:1 ceramide molecular species, (ii) nearly totally halted production of respective glucosylceramide (GC) molecular species, (iii) drastically reduced levels of sphingosine (to 9% of control), and (iv) reduced levels of S1-P by 85%, in vincristine-resistant HL-60/VCR cells. The co-administration of tamoxifen with either N-(4-hydroxyphenyl)retinamide (4-HPR), a ceramide-generating retinoid, or a cell-deliverable form of ceramide, C6-ceramide, resulted in marked decreases in HL-60/VCR cell viability that far exceeded single agent potency. Combination treatments resulted in synergistic apoptotic cell death as gauged by increased Annexin V binding and DNA fragmentation and activation of caspase-3. These results show the versatility of adjuvant triphenylethylene with ceramide-centric therapies for magnifying therapeutic potential in AML. Such drug regimens could serve as effective strategies, even in the multidrug-resistant setting.

Long-term outcomes of MUA for stiffness in primary TKA.

Knee stiffness following primary total knee arthroplasty (TKA) is a well-recognized problem which leads to poor patient outcomes and may limit patient activities of daily living. Manipulation under anesthesia (MUA) is one option for the treatment of knee stiffness. However, there has been controversy regarding the safety and long-term efficacy of this procedure. A systematic review of the literature was performed to identify studies that reported the clinical outcomes and measured range of motion for patients undergoing MUA. Fourteen studies (913 patients) reported range of motion results following MUA at up to 10-year follow-up. The mean premanipulation and final range of motion were 66 and 99 degrees, respectively. Compared with preoperative range of motion, the gain in the range-of-motion arc at 1-, 5-, and 10-year follow-up was 30, 33, and 33 degrees, respectively. Complications were rare with only two reported periprosthetic fractures, resulting in an incidence of 0.2%. MUA for a stiff primary TKA is an efficacious procedure to restore range of motion. Early gains in motion appear to be maintained at long term, and in some cases patients may gradually improve further at mid-term follow-up. The risk of periprosthetic fracture is low, making MUA a safe option for improving knee range of motion.

Vemurafenib (PLX4032): an orally available inhibitor of mutated BRAF for the treatment of metastatic melanoma.

OBJECTIVE: To summarize the preclinical and clinical data on vemurafenib, approved by the Food and Drug Administration (FDA) on August 17, 2011, and discuss the drug's clinical advantages and limitations. DATA SOURCES: An English-language literature search of MEDLINE/PubMed (1966-August 2011), using the terms PLX4032, RG7204, RO5185426, vemurafenib, and metastatic melanoma, was conducted. In addition, information and data were obtained from meeting abstracts, clinical trial registries, and news releases from the FDA. STUDY SELECTION AND DATA EXTRACTION: All relevant published articles and abstracts on vemurafenib were included. Clinical trial registries and meeting abstracts were used to obtain information regarding ongoing trials. All peer-reviewed articles containing information regarding the clinical safety and efficacy of vemurafenib were evaluated for inclusion. DATA SYNTHESIS: Before the recent approval (March 2011) of ipilimumab, there was no first-line standard-of-care therapy, with proven overall survival benefit, for the treatment of malignant metastatic melanoma. Unlike ipilimumab, which acts through immune-modulation, vemurafenib is a novel, molecularly targeted therapeutic with preferential efficacy toward a specific mutated oncogenic BRAF-signaling mediator. In recently published results of a Phase 3 clinical trial comparing dacarbazine with vemurafenib, vemurafenib prolonged progression-free and overall survival, with confirmed objective response rate of 48% (95% CI 42 to 55) versus 5% (95% CI 3 to 9) for patients who received dacarbazine (p < 0.001). CONCLUSIONS: Vemurafenib offers a novel, first-line, personalized therapy for patients who have mutated BRAF. Clinical trials of vemurafenib in combination with ipilimumab or other targeted or cytotoxic chemotherapeutic agents may provide more effective regimens with long-term clinical benefit.

State-dependent block of HERG potassium channels by R-roscovitine: implications for cancer therapy.

Human ether-a-go-go-related gene (HERG) potassium channel acts as a delayed rectifier in cardiac myocytes and is an important target for both pro- and antiarrhythmic drugs. Many drugs have been pulled from the market for unintended HERG block causing arrhythmias. Conversely, recent evidence has shown that HERG plays a role in cell proliferation and is overexpressed both in multiple tumor cell lines and in primary tumor cells, which makes HERG an attractive target for cancer treatment. Therefore, a drug that can block HERG but that does not induce cardiac arrhythmias would have great therapeutic potential. Roscovitine is a cyclin-dependent kinase (CDK) inhibitor that is in phase II clinical trials as an anticancer agent. In the present study we show that R-roscovitine blocks HERG potassium current (human embryonic kidney-293 cells stably expressing HERG) at clinically relevant concentrations. The block (IC(50) = 27 microM) was rapid (tau = 20 ms) and reversible (tau = 25 ms) and increased with channel activation, which supports an open channel mechanism. Kinetic study of wild-type and inactivation mutant HERG channels supported block of activated channels by roscovitine with relatively little effect on either closed or inactivated channels. A HERG gating model reproduced all roscovitine effects. Our model of open channel block by roscovitine may offer an explanation of the lack of arrhythmias in clinical trials using roscovitine, which suggests the utility of a dual CDK/HERG channel block as an adjuvant cancer therapy.

Use of an alumina-on-alumina bearing system in total hip arthroplasty for osteonecrosis of the hip.

BACKGROUND: The results of total hip arthroplasty in patients with osteonecrosis of the femoral head are not always optimal. The use of alumina-on-alumina interfaces in young and active patients may decrease wear and lower the rate of aseptic loosening of the implant and appears to be an attractive alternative to the use of conventional cobalt-chromium-on-polyethylene bearings. The purpose of this study was to evaluate the safety and efficacy of the alumina-on-alumina bearing in patients with osteonecrosis and to compare this group of patients to a group of similarly treated patients with osteoarthritis and a group of patients who received conventional cobalt-chromium-on-polyethylene bearings. METHODS: Patients were selected from a United States Investigational Device Exemption multicenter prospective randomized clinical study that was initiated in 1996. Seventy patients with osteonecrosis of the femoral head (seventy-nine hips) received a cementless alumina-on-alumina bearing system and were directly matched to seventy-six patients with osteoarthritis of the hip (seventy-nine hips) who were managed with the same implant. Both groups were compared with twenty-five patients (twenty-six hips) with osteonecrosis and twenty-five patients (twenty-six hips) with osteoarthritis who were managed with a cementless cobalt-chromium-on-polyethylene bearing system. All patients received a cementless hydroxyapatite-coated femoral stem and were followed both clinically and radiographically. RESULTS: The clinical outcomes for alumina-on-alumina bearings were similar for both osteonecrotic and osteoarthritic hips. The seven-year survival probability was 95.5% for the osteonecrotic hips and 89.4% for the osteoarthritic hips in the alumina-on-alumina bearing group and 92.3% for the osteonecrotic hips and 92.9% for the osteoarthritic hips in the cobalt-chromium-on-polyethylene bearing group. At the time of the most recent follow-up, the mean Harris hip score was 96 points for both the osteonecrotic and the osteoarthritic hips in the alumina-on-alumina group and 96 points for the osteonecrotic hips and 97 points for the osteoarthritic hips in the cobalt-chromium-on-polyethylene bearing group. CONCLUSIONS: The results of the use of alumina-on-alumina and cobalt-chromium-on-polyethylene bearings in cementless standard total hip implants in patients with osteonecrosis and osteoarthritis were comparable. The low revision rate for the alumina-on-alumina bearing is encouraging and offers a promising option for younger, more active patients who have this challenging disease. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.