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Chronic natural killer large granular lymphocyte (NK-LGL) leukemia, also referred to as chronic lymphoproliferative disorder of NK cells, is a rare disorder defined by prolonged expansion of clonal NK cells. Similar prevalence of STAT3 mutations in chronic T-LGL and NK-LGL leukemia is suggestive of common pathogenesis. We undertook whole-genome sequencing to identify mutations unique to NK-LGL leukemia. The results were analyzed to develop a resequencing panel that was applied to 58 patients. Phosphatidylinositol 3-kinase pathway gene mutations (PIK3CD/PIK3AP1) and TNFAIP3 mutations were seen in 5% and 10% of patients, respectively. TET2 was exceptional in that mutations were present in 16 (28%) of 58 patient samples, with evidence that TET2 mutations can be dominant and exclusive to the NK compartment. Reduced-representation bisulfite sequencing revealed that methylation patterns were significantly altered in TET2 mutant samples. The promoter of TET2 and that of PTPRD, a negative regulator of STAT3, were found to be methylated in additional cohort samples, largely confined to the TET2 mutant group. Mutations in STAT3 were observed in 19 (33%) of 58 patient samples, 7 of which had concurrent TET2 mutations. Thrombocytopenia and resistance to immunosuppressive agents were uniquely observed in those patients with only TET2 mutation (Games-Howell post hoc test, P = .0074; Fisher’s exact test, P = .00466). Patients with STAT3 mutation, inclusive of those with TET2 comutation, had lower hematocrit, hemoglobin, and absolute neutrophil count compared with STAT3 wild-type patients (Welch’s t test, P ≤ .015). We present the discovery of TET2 mutations in chronic NK-LGL leukemia and evidence that it identifies a unique molecular subtype.

Large granular lymphocyte (LGL) leukemia is a rare hematological disorder with expansion of the T‐cell or natural killer (NK) cell lineage. Signal transducer and activator of transcription 3 (STAT3) exhibits somatic activating mutations in 30%‐40% of LGL leukemia cases. Transcriptional targets of STAT3 include inflammatory cytokines, thus previous studies have measured cytokine levels of LGL leukemia patients compared to normal donors. Sphingolipid metabolism is a growing area of cancer research, with efforts focused on drug discovery. To date, no studies have examined serum sphingolipids in LGL leukemia patients, and only one study compared a subset of cytokines between the T‐LGL and NK‐LGL subtypes. Therefore, here, we included both LGL leukemia subtypes with the goals of (a) measuring serum sphingolipids for the first time, (b) measuring cytokines to find distinctions between the subtypes, and (c) establishing relationships with STAT3 mutations and clinical data. The serum analyses identified cytokines (EGF, IP‐10, G‐CSF) and sphingolipids (SMC22, SMC24, SMC20, LysoSM) significantly different in the LGL leukemia group compared to normal donors. In a mixed STAT3 mutation group, D661Y samples exhibited the highest mean corpuscular volume (MCV) values. We explored this further by expanding the cohort to include larger groups of single STAT3 mutations. Male D661Y STAT3 samples had lower Hgb and higher MCV compared to wild type (WT) or Y640F counterparts. This is the first report examining large groups of individual STAT3 mutations. Overall, our results revealed novel serum biomarkers and evidence that D661Y mutation may show different clinical manifestation compared to WT or Y640F STAT3., Analysis of LGL leukemia serum identified cytokines (EGF, IP‐10, G‐CSF) and sphingolipids (SMC22, SMC24, SMC20, LysoSM) that were significantly different compared to normal donors. Comparing three groups of STAT3 mutation status (WT, Y640F, D661Y) in LGL leukemia patients showed the D661Y mutation group had higher mean corpuscular volume and lower hemoglobin compared to the other groups.

Chronic lymphoproliferative disorder of natural killer cells (CLPD-NK) is characterized by clonal expansion of natural killer (NK) cells where the underlying genetic mechanisms are incompletely understood. In the present study, we report somatic mutations in the chemokine gene CCL22 as the hallmark of a distinct subset of CLPD-NK. CCL22 mutations were enriched at highly conserved residues, mutually exclusive of STAT3 mutations and associated with gene expression programs that resembled normal CD16

Context: Chronic lymphoproliferative disorder of natural killer cells (CLPD-NK) is a subset of large granular lymphocyte (LGL) leukemia included as a provisional entity in the 2016 WHO classification of lymphoid neoplasms, which is characterized by clonal expansion of NK cells with no standardized therapy. STAT3 and TET2 mutations were previously each reported in 15%–30% of cases; however, the genomic basis of the remaining cases is still unknown. Objective: We aimed to perform a comprehensive genomic and transcriptomic analysis of CLPD-NK to elucidate the genomic landscape, investigate mechanisms of pathogenesis, and improve diagnostic classification and treatment strategies. Methods: CLPD-NK samples (n=121) were examined by whole-genome, targeted, and/or whole-transcriptome sequencing. Structural modeling, G-protein signaling, β-arrestin signaling, G-protein-coupled receptor (GPCR) for CCL22, CCR4 internalization, and chemotaxis were examined. Cell line-derived xenografts were used to examine cell proliferation and phenotype. Results: Somatic mutations in the chemokine CCL22 were found in 21.5% of CLPD-NK patients but not in 2837 cases of other hematological malignancies, including T-LGL and other NK leukemias. Clinically, there was a trend to an association with cutaneous complications and/or neurological symptoms. CCL22 mutations were enriched at the highly conserved residues Leu45, Pro46, and Pro79 and were mutually exclusive of STAT3 mutations. CCL22 mutations were associated with dysregulated gene expression, similar to normal CD56bright NK cells, with enrichment for activation of cytokine signaling pathways, representing a distinct subgroup. Most CCL22 mutations were substitutions to Arg, a basic residue, and Leu45Arg was predicted to promote electrostatic interactions with CCR4-Tyr22/Glu23 acidic residues. The mutations resulted in ligand-biased CCR4 signaling, in which activation of G-protein signaling was unchanged, but recruitment of β-arrestin, which mediates receptor internalization, was impaired, which, in turn, resulted in enhanced cell chemotaxis. CCL22 mutations drove enhanced cell proliferation in vivo in hIL-15-transgenic mice and induced an expression profile resembling that of primary samples, indicating the importance of microenvironmental crosstalk in pathogenesis. Conclusions: Somatic CCL22 mutations defined a new subgroup of CLPD-NK similar to CD56bright normal NK cells and represented a novel mechanism of leukemogenesis in which gain-of-function chemokine mutations drive tumorigenesis by biased GPCR signaling and dysregulation of microenvironmental crosstalk.

PURPOSE OF REVIEW: The past decade in LGL leukemia research has seen increased pairing of clinical data with molecular markers, shedding new insights on LGL leukemia pathogenesis and heterogeneity. This review summarizes the current standard of care of LGL leukemia, updates from clinical trials, and our congruent improved understanding of LGL pathogenesis. RECENT FINDINGS: Various clinical reports have identified associations between stem, bone-marrow, and solid organ transplants and incidence of LGL leukemia. There is also a potential for underdiagnosis of LGL leukemia within the rheumatoid arthritis patient population, emphasizing our need for continued study. Preliminary results from the BNZ-1 clinical trial, which targets IL-15 along with IL-2 and IL-9 signaling pathways, show some evidence of clinical response. SUMMARY: With advances in our understanding of LGL pathogenesis from both the bench and the clinic, exciting avenues for investigations lie ahead for LGL leukemia.

Genomic analysis of cancer offers the hope of identifying new treatments or aiding in the selection of existing treatments. Rare leukemias pose additional challenges in this regard as samples may be hard to acquire and when found the underlying pathway may not be attractive to drug development since so few individuals are affected. In this case, it can be useful to identify common mutational overlap among subsets of rare leukemias to increase the number of individuals that may benefit from a targeted therapy. This chapter examines the current mutational landscape of large granular lymphocyte (LGL) leukemia with a focus on STAT3 mutations, the most common mutation in LGL leukemia to date. We examined the linkage between these mutations and autoimmune symptoms and disorders, in cases of obvious and suspected LGL leukemia. We then summarized and compared mutations in a set of other rare leukemias that also have JAK/STAT signaling pathway activation brought about by genomic changes. These include T-cell acute lymphoblastic leukemia (T-ALL), T-cell prolymphocytic leukemia (T-PLL), cutaneous T-cell lymphoma (CTCL), select peripheral T-cell lymphoma (PTCL), and adult T-cell leukemia/lymphoma (ATLL). Though STAT3 activation is common in these leukemias, the way in which it is achieved, such as the activating cytokine pathway and/or the co-mutational background, is quite diverse.

Commonly known for its critical role in calcium homeostasis and bone mineralization, more recently vitamin D has been implicated in haematological cancer pathogenesis and shows promise as an anti-cancer therapy. Serum levels of 25(OH)D3, the precursor to the active form of vitamin D, calcitriol, are typically lower in patients with haematological disease compared to healthy individuals. This often correlates with worse disease outcome. Furthermore, diseased cells typically highly express the vitamin D receptor (VDR), which is required for many of the anti-cancer effects observed in multiple in vivo and in vitro cancer models. In abnormal haematological cells, vitamin D supplementation promotes apoptosis, induces differentiation, inhibits proliferation, sensitizes tumor cells to other anti-cancer therapies, and reduces the production of pro-inflammatory cytokines. Although the dosage of vitamin D required to achieve these effects may induce hypercalcemia in humans, analogs and combinatorial treatments have been developed to circumvent this side effect. Vitamin D and its analogs are well tolerated in clinical trials and thus further investigation into the use of these agents in the clinic is warranted. Here we review the current literature in this field.

Large granular lymphocyte leukemia (LGLL) is a rare incurable chronic disease typically characterized by clonal expansion of CD3+ cytotoxic T-cells. Two signal transducer and activator of transcription factors, STAT1 and STAT3, are constitutively active in T-LGLL. Disruption of this activation induces apoptosis in T-LGLL cells. Therefore, considerable efforts are focused on developing treatments that inhibit STAT activation. Calcitriol, the active form of vitamin D, has been shown to decrease STAT1 and STAT3 phosphorylation in cancer cell lines and autoimmune disease mouse models. Thus, we investigated whether calcitriol could be a valid therapeutic for T-LGLL. Calcitriol treatment of the TL-1 cell line (model of T-LGLL) led to decreased phospho-Y701 STAT1 and phospho-Y705 STAT3 and increased vitamin D receptor (VDR) levels. Doses of 10 and 100 nM calcitriol also significantly decreased the inflammatory cytokine IFN-γ in the TL-1 cell line. The overall cell viability did not change when the TL-1 cell line was treated with 0.1 to 1000 nM calcitriol. Studies with primary T-LGLL patient peripheral blood mononuclear cells showed that the majority of T-LGLL patients have detectable VDR and activated STATs in contrast to normal donor controls. Treatment of primary T-LGLL patient cells with calcitriol recapitulated findings from the TL-1 cell line. Overall, our results suggest that calcitriol may reprogram T-cells to decrease essential STAT activation and pro-inflammatory cytokine output. These data support further investigation into calcitriol as an experimental therapeutic for T-LGLL.

Calcitriol, the active form of vitamin D, has been well documented to act directly on immune cells and malignant cells. Activated T cells are one of the best characterized targets of calcitriol, with effects including decreasing inflammatory cytokine output and promoting anti-inflammatory cytokine production. However, the effects of calcitriol on natural killer (NK) cells are less clear. Reports suggest that only immature NK cell populations are affected by calcitriol treatment resulting in impaired cytotoxic function and cytokine production, while mature NK cells may have little or no response. NK cell large granular lymphocyte leukemia (NK-LGLL) is a rare leukemia with CD3-CD16+CD56+NK cell clonal expansion. The current standard treatments are immunosuppressant therapies, which are not curative. The Janus kinase (JAK) – signal transducer and activator of transcription (STAT) pathway is hyperactivated in LGLL and is one pathway of interest in new drug target investigations. We previously demonstrated the ability of calcitriol to decrease STAT1 tyrosine 701 (p-STAT1) and STAT3 tyrosine 705 (p-STAT3) phosphorylation as well as inflammatory cytokine output of T cell large granular lymphocyte leukemia cells, but did not determine the effects of calcitriol on NK-LGLL. Therefore, in the present study, we investigated whether NKL cells, a model of NK-LGLL, and NK-LGLL patient peripheral blood mononuclear cells (PBMCs) are susceptible to treatment with calcitriol or seocalcitol (EB1089), a potent analog of calcitriol. NKL cells are dependent on interleukin (IL)-2 for survival and we show here for the first time that treatment with IL-2 induced tyrosine phosphorylation of STATs 1 through 6. Both calcitriol and EB1089 caused significant upregulation of the vitamin D receptor (VDR). IL-2 induction of p-STAT1 and p-STAT3 phosphorylation was significantly decreased after calcitriol or EB1089 treatment. Additionally, IL-10, interferon (IFN)-γ, and FMS-like tyrosine kinase 3 ligand (Flt-3L) extracellular output was significantly decreased at 100 nM EB1089 and intracellular IL-10 was decreased with either calcitriol or EB1089 treatment. We treated NK-LGLL patient PBMCs with calcitriol or EB1089 and found decreased p-STAT1 and p-STAT3 while VDR increased, which matched the NKL cell line data. We then measured 75 serum cytokines in NK-LGLL patients (n = 8) vs. age- and sex-matched normal healthy donors (n = 8), which is the first serum cytokine study for this LGLL subtype. We identified 15 cytokines, including IL-10 and Flt-3L, which were significantly different between normal donors and NK-LGLL patients. Overall, our results suggest that activating the vitamin D pathway could be a mechanism to decrease STAT1 and 3 activation and inflammatory cytokine output in NK-LGLL patients.

T cell large granular lymphocyte leukemia (T-LGLL) is a rare incurable disease that is characterized by defective apoptosis of cytotoxic CD8+ T cells. Chronic activation of the Janus Kinase-Signal Transducer and Activator of Transcription (JAK-STAT) pathway is a hallmark of T-LGLL. One manifestation is the constitutive phosphorylation of tyrosine 701 of STAT1 (p-STAT1). T-LGLL patients also exhibit elevated serum levels of the STAT1 activator, interferon-γ (IFN-γ), thus contributing to an inflammatory environment. In normal cells, IFN-γ production is tightly controlled through induction of IFN-γ negative regulators. However, in T-LGLL, IFN-γ signaling lacks this negative feedback mechanism as evidenced by excessive IFN-γ production and decreased levels of suppressors of cytokine signaling 1 (SOCS1), a negative regulator of IFN-γ. Here we characterize the IFN-γ-STAT1 pathway in TL-1 cells, a cell line model of T-LGLL. TL-1 cells exhibited lower IFN-γ receptor protein and mRNA expression compared to an IFN-γ responsive cell line. Furthermore, IFN-γ treatment did not induce JAK2 or STAT1 activation or transcription of IFN-γ-inducible gene targets. However, IFN-β induced p-STAT1 and subsequent STAT1 gene transcription, demonstrating a specific IFN-γ signaling defect in TL-1 cells. We utilized siRNA targeting of STAT1, STAT3, and STAT5b to probe their role in IL-2-mediated IFN-γ regulation. These studies identified STAT5b as a positive regulator of IFN-γ production. We also characterized the relationship between STAT1, STAT3, and STAT5b proteins. Surprisingly, p-STAT1 was positively correlated with STAT3 levels while STAT5b suppressed the activation of both STAT1 and STAT3. Taken together, these results suggest that the dysregulation of the IFN-γ-STAT1 signaling pathway in TL-1 cells likely results from low levels of the IFN-γ receptor. The resulting inability to induce negative feedback regulators explains the observed elevated IL-2 driven IFN-γ production. Future work will elucidate the best way to target this pathway, with the ultimate goal to find a better therapeutic for T-LGLL.

p97 is a “segregase” that plays a key role in numerous ubiquitin (Ub)-dependent pathways such as ER-associated degradation. It has been hypothesized that p97 extracts proteins from membranes or macromolecular complexes to enable their proteasomal degradation; however, the complex nature of p97 substrates has made it difficult to directly observe the fundamental basis for this activity. To address this issue, we developed a soluble p97 substrate—Ub-GFP modified with K48-linked ubiquitin chains—for in vitro p97 activity assays. We demonstrate that WT p97 can unfold proteins and that this activity is dependent on the p97 adaptor NPLOC4-UFD1L, ATP hydrolysis, and substrate ubiquitination, with branched chains providing maximal stimulation. Furthermore, we show that a p97 mutant that causes inclusion body myopathy, Paget’s disease of bone, and frontotemporal dementia in humans unfolds substrate faster, suggesting that excess activity may underlie pathogenesis. This work overcomes a significant barrier in the study of p97 and will allow the future dissection of p97 mechanism at a level of detail previously unattainable.

p97 is a ‘segregase’ that plays a key role in numerous ubiquitin-dependent pathways, such as ER-associated degradation (ERAD). It has been hypothesized that p97 extracts proteins from membranes or macromolecular complexes to enable their proteasomal degradation; however, the complex nature of p97 substrates has made it difficult to directly observe the fundamental basis for this activity. To address this issue, we developed a soluble p97 substrate—Ub-GFP modified with K48-linked ubiquitin chains—for in vitro p97 activity assays. We demonstrate for the first time that wild type p97 can unfold proteins and that this activity is dependent on the p97 adaptor NPLOC4-UFD1L, ATP hydrolysis, and substrate ubiquitination, with branched chains providing maximal stimulation. Furthermore, we show that a p97 mutant that causes inclusion body myopathy, Paget’s Disease of bone, and frontotemporal dementia (IBMPFD) in humans unfolds substrate faster, suggesting that excess activity may underlie pathogenesis. This work overcomes a significant barrier in the study of p97 and will allow the future dissection of p97 mechanism at a level of detail previously unattainable.

Constitutively activated STAT1 and elevated IFN-γ are both characteristic of T cell large granular lymphocytic leukemia (T-LGLL), a rare incurable leukemia with clonal expansion of cytotoxic T cells due to defective apoptosis. Interferon gamma (IFN-γ) is an inflammatory cytokine that correlates with worse progression and symptomology in multiple autoimmune diseases and cancers. In canonical IFN-γ-STAT1 signaling, IFN-γ activates STAT1, a transcription factor, via phosphorylation of tyrosine residue 701 (p-STAT1). p-STAT1 then promotes transcription of IFN-γ, creating a positive feedback loop. We previously found that calcitriol treatment of the TL-1 cell line, a model of T-LGLL, significantly decreased IFN-γ secretion and p-STAT1 while increasing the vitamin D receptor (VDR) protein. Here we further explore these observations. Using TL-1 cells, IFN-γ decreased starting at 4 h following calcitriol treatment, with a reduction in the intracellular and secreted protein levels as well as the mRNA content. A similar reduction in IFN-γ transcript levels was observed in primary T-LGLL patient peripheral blood mononuclear cells (PBMCs). p-STAT1 inhibition followed a similar temporal pattern and VDR upregulation inversely correlated with IFN-γ levels. Using EB1089 and 25(OH)D(3), which have high or low affinity for VDR, respectively, we found that the decrease in IFN-γ correlated with the ability of EB1089, but not 25(OH)D(3), to upregulate VDR. However, both compounds inhibited p-STAT1; thus the reduction of p-STAT1 is not solely responsible for IFN-γ inhibition. Conversely, cells treated with VDR siRNA exhibited decreased basal IFN-γ production upon VDR knockdown in a dose-dependent manner. Calcitriol treatment upregulated VDR and decreased IFN-γ regardless of initial VDR knockdown efficiency, strengthening the connection between VDR upregulation and IFN-γ reduction. Our findings suggest multiple opportunities to further explore the clinical relevance of the vitamin D pathway and the potential role for vitamin D supplementation in T-LGLL.

Branched-chain keto acids (BCKAs) are associated with increased susceptibility to several degenerative diseases. However, BCKA concentrations in tissues or the amounts of tissue available are frequently at the limit of detection for standard plasma methods. To accurately and quickly determine tissue BCKAs, we have developed a sensitive ultra fast liquid chromatography-mass spectrometry (UFLC-MS) method. BCKAs from deproteinized tissue extractions were o-phenylenediamine (OPD) derivatized, ethyl acetate extracted, lyophilized in a vacuum centrifuge, and reconstituted in 200 mM ammonium acetate. Samples were injected onto a Shimadzu UFLC system coupled to an AB-Sciex 5600 Triple TOF mass spectrometer instrument that detected masses of the OPD BCKA products using a multiple reaction monitoring method. An OPD-derivatized (13)C-labeled keto acid was used as an internal standard. Application of the method for C57BL/6J (wild-type) and PP2Cm knockout mouse tissues, including kidney, adipose tissue, liver, gastrocnemius, and hypothalamus, is shown. The lowest tissue concentration measured by this method was 20 nM, with the standard curve covering a wide range (7.8-32,000 nM). Liquid chromatography-mass spectrometry run times for this assay were less than 5 min, facilitating high throughput, and the OPD derivatives were found to be stable over several days.

Elevated blood branched-chain amino acids (BCAA) are often associated with insulin resistance and type 2 diabetes, which might result from a reduced cellular utilization and/or incomplete BCAA oxidation. White adipose tissue (WAT) has become appreciated as a potential player in whole body BCAA metabolism. We tested if expression of the mitochondrial BCAA oxidation checkpoint, branched-chain α-ketoacid dehydrogenase (BCKD) complex, is reduced in obese WAT and regulated by metabolic signals. WAT BCKD protein (E1α subunit) was significantly reduced by 35–50% in various obesity models ( fa/fa rats, db/db mice, diet-induced obese mice), and BCKD component transcripts significantly lower in subcutaneous (SC) adipocytes from obese vs. lean Pima Indians. Treatment of 3T3-L1 adipocytes or mice with peroxisome proliferator-activated receptor-γ agonists increased WAT BCAA catabolism enzyme mRNAs, whereas the nonmetabolizable glucose analog 2-deoxy-d-glucose had the opposite effect. The results support the hypothesis that suboptimal insulin action and/or perturbed metabolic signals in WAT, as would be seen with insulin resistance/type 2 diabetes, could impair WAT BCAA utilization. However, cross-tissue flux studies comparing lean vs. insulin-sensitive or insulin-resistant obese subjects revealed an unexpected negligible uptake of BCAA from human abdominal SC WAT. This suggests that SC WAT may not be an important contributor to blood BCAA phenotypes associated with insulin resistance in the overnight-fasted state. mRNA abundances for BCAA catabolic enzymes were markedly reduced in omental (but not SC) WAT of obese persons with metabolic syndrome compared with weight-matched healthy obese subjects, raising the possibility that visceral WAT contributes to the BCAA metabolic phenotype of metabolically compromised individuals.

Background— Although metabolic reprogramming is critical in the pathogenesis of heart failure, studies to date have focused principally on fatty acid and glucose metabolism. Contribution of amino acid metabolic regulation in the disease remains understudied. Methods and Results— Transcriptomic and metabolomic analyses were performed in mouse failing heart induced by pressure overload. Suppression of branched-chain amino acid (BCAA) catabolic gene expression along with concomitant tissue accumulation of branched-chain α-keto acids was identified as a significant signature of metabolic reprogramming in mouse failing hearts and validated to be shared in human cardiomyopathy hearts. Molecular and genetic evidence identified the transcription factor Krüppel-like factor 15 as a key upstream regulator of the BCAA catabolic regulation in the heart. Studies using a genetic mouse model revealed that BCAA catabolic defect promoted heart failure associated with induced oxidative stress and metabolic disturbance in response to mechanical overload. Mechanistically, elevated branched-chain α-keto acids directly suppressed respiration and induced superoxide production in isolated mitochondria. Finally, pharmacological enhancement of branched-chain α-keto acid dehydrogenase activity significantly blunted cardiac dysfunction after pressure overload. Conclusions— BCAA catabolic defect is a metabolic hallmark of failing heart resulting from Krüppel-like factor 15–mediated transcriptional reprogramming. BCAA catabolic defect imposes a previously unappreciated significant contribution to heart failure.

Dibenzo[a,l]pyrene (DB[a,l]P) (dibenzo[def,p]chrysene) is a highly carcinogenic polycyclic aromatic hydrocarbon (PAH) that has been identified in tobacco smoke and is found in our environment due to incomplete combustion of organic matter. Its metabolites are known to form stable DNA adducts in bacteria and mammalian cells, and can lead to tumors in animal models. Glucuronidation of major metabolites of DB[a,l]P by the uridine-5’-diphosphate glucuronosyltransferase (UGT) family of enzymes is an important route of detoxification of this pro-carcinogen. The focus of the current study was to characterize the glucuronidation of the pro-carcinogenic enantiomers DB[a,l]P-(+)-trans-11S,12S–diol and DB[a,l]P-(−)-trans-11R,12R–diol. Glucuronidation assays with HEK293 cell lines over-expressing individual human UGT enzymes demonstrated that UGTs 1A1, 1A4, 1A7, 1A8, 1A9, 1A10, and 2B7 glucuronidated one or both DB[a,l]P-trans-11,12-diol enantiomers. Three glucuronide conjugates were observed in activity assays with UGTs 1A1 and 1A10, while two glucuronides were formed by UGTs 1A7, 1A8, and 1A9, and one glucuronide was made by UGT1A4 and UGT2B7. Enzyme kinetic analysis indicated that UGT1A9 was the most efficient UGT at forming both the (+)-DB[a,l]P-11-Gluc and (−)-DB[a,l]P-11-Gluc products while UGTs 1A1 and 1A10 were the most efficient at forming the (+)-DB[a,l]P-12-Gluc product (as determined by the kcat/KM). Incubations with human liver microsomes showed formation of three diastereomeric glucuronide products: (+)-DB[a,l]P-11-Gluc, (+)-DB[a,l]P-12-Gluc, and (−)-DB[a,l]P-11-Gluc, with an average overall ratio of 31 : 32 : 37 in four liver specimens. Human bronchus and trachea tissue homogenates demonstrated glucuronidation activity against both DB[a,l]P-trans-11,12-diol enantiomers, with both tissues producing the (+)-DB[a,l]P-11-Gluc and (+)-DB[a,l]P-12-Gluc with little or no formation of (−)-DB[a,l]P-11-Gluc. These results indicate that multiple UGTs are involved in the stereospecific glucuronidation of DB[a,l]P-trans-11,12-diol in a pattern consistent with their expression in respiratory tract tissues, and that glucuronidation may be an important first-line detoxification mechanism of DB[a,l]P metabolites.

Liver transplantation appears to be quite beneficial for treatment of Maple Syrup Urine Disease (MSUD, an inherited disorder of branched chain amino acid metabolism); however, there is a limited availability of donor livers worldwide and the first year costs of liver transplants are quite high. Recent studies have suggested that intact adipose tissue, already widely used in reconstructive surgery, may have an underappreciated high capacity for branched chain amino acid (BCAA) metabolism. Here we examined the potential for adipose tissue transplant to lower circulating BCAAs in two models of defective BCAA metabolism, BCATm and PP2Cm [branched chain keto acid dehydrogenase complex (BCKDC) phosphatase] knockout (KO) mice. After 1–2 g fat transplant, BCATm and PP2Cm KO mice gained or maintained body weight 3 weeks after surgery and consumed similar or more food/BCAAs the week before phlebotomy. Transplant of fat into the abdominal cavity led to a sterile inflammatory response and nonviable transplanted tissue. However when 1–2 g of fat was transplanted subcutaneously into the back, either as small (0.1–0.3g) or finely minced pieces introduced with a 18 ga. needle, plasma BCAAs decreased compared to Sham operated mice. In two studies on BCATm KO mice and one study on PP2Cm KO mice, fat transplant led to 52–81% reductions in plasma BCAAs compared to baseline plasma BCAA concentrations of untreated WT type siblings. In PP2Cm KO mice, individual BCAAs in plasma were also significantly reduced by fat transplant, as were the alloisoleucine/Phe ratios. Therefore, subcutaneous fat transplantation may have merit as an adjunct to dietary treatment of MSUD. Additional studies are needed to further refine this approach.

The UDP-glucuronosyltransferase (UGT) 1A9 has been shown to play an important role in the detoxification of several carcinogens and clearance of anticancer and pain medications. The goal of the present study was to identify novel polymorphisms in UGT1A9 and characterize their effect on glucuronidation activity. The UGT1A9 gene was analyzed by direct sequencing of buccal cell genomic DNA from 90 healthy subjects. In addition to a previously identified single nucleotide polymorphism (SNP) at codon 33 resulting in an amino acid substitution (MetThr), two low-prevalence (0.02) novel missense SNPs at codons 167 (ValAla) and 183 (CysGly) were identified and are present in both white and African-American subjects. Glucuronidation activity assays using HEK293 cell lines overexpressing wild-type or variant UGT1A9 demonstrated that the UGT1A9(33Thr) and UGT1A9(183Gly) variants exhibited differential glucuronidation activities compared with wild-type UGT1A9, but this was substrate-dependent. The UGT1A9(167Ala) variant exhibited levels of activity similar to those of wild-type UGT1A9 for all substrates tested. Whereas the wild-type and UGT1A9(33Thr) and UGT1A9(167Ala) variants formed homodimers as determined by Western blot analysis of native polyacrylamide gels, the UGT1A9(183Gly) variant was incapable of homodimerization. These results suggest that several low-prevalence missense polymorphisms exist for UGT1A9 and that two of these (M33T and C183G) are functional. These results also suggest that although Cys183 is necessary for UGT1A9 homodimerization, the lack of capacity for UGT1A9 homodimerization is not sufficient to eliminate UGT1A9 activity.

Branched-chain amino acids (BCAAs) are circulating nutrient signals for protein accretion, however, they increase in obesity and elevations appear to be prognostic of diabetes. To understand the mechanisms whereby obesity affects BCAAs and protein metabolism, we employed metabolomics and measured rates of [1-(14)C]-leucine metabolism, tissue-specific protein synthesis and branched-chain keto-acid (BCKA) dehydrogenase complex (BCKDC) activities. Male obese Zucker rats (11-weeks old) had increased body weight (BW, 53%), liver (107%) and fat (∼300%), but lower plantaris and gastrocnemius masses (-21-24%). Plasma BCAAs and BCKAs were elevated 45-69% and ∼100%, respectively, in obese rats. Processes facilitating these rises appeared to include increased dietary intake (23%), leucine (Leu) turnover and proteolysis [35% per g fat free mass (FFM), urinary markers of proteolysis: 3-methylhistidine (183%) and 4-hydroxyproline (766%)] and decreased BCKDC per g kidney, heart, gastrocnemius and liver (-47-66%). A process disposing of circulating BCAAs, protein synthesis, was increased 23-29% by obesity in whole-body (FFM corrected), gastrocnemius and liver. Despite the observed decreases in BCKDC activities per gm tissue, rates of whole-body Leu oxidation in obese rats were 22% and 59% higher normalized to BW and FFM, respectively. Consistently, urinary concentrations of eight BCAA catabolism-derived acylcarnitines were also elevated. The unexpected increase in BCAA oxidation may be due to a substrate effect in liver. Supporting this idea, BCKAs were elevated more in liver (193-418%) than plasma or muscle, and per g losses of hepatic BCKDC activities were completely offset by increased liver mass, in contrast to other tissues. In summary, our results indicate that plasma BCKAs may represent a more sensitive metabolic signature for obesity than BCAAs. Processes supporting elevated BCAA]BCKAs in the obese Zucker rat include increased dietary intake, Leu and protein turnover along with impaired BCKDC activity. Elevated BCAAs/BCKAs may contribute to observed elevations in protein synthesis and BCAA oxidation.

A procarcinogen found most notably in tobacco smoke is dibenzo[a,l]pyrene (DB[a,l]P), which can be further metabolized into its epoxide, diol, and carcinogenic diol-epoxide forms. DB[a,l]P metabolites are some of the most potent carcinogens of the polycyclic aromatic hydrocarbon (PAH) family of compounds due to a structural feature called the fjord region. The activated metabolites of DB[a,l]P bind mostly to deoxyadenosine in DNA to form stable adducts, which can potentially lead to DNA damage. UDP-glucuronosyltransferase (UGT) enzymes mediate the attachment of a UDP-glucuronic acid to a wide variety of endogenous and exogenous substrates including several carcinogens, resulting in increases in water solubility and elimination of the carcinogen from the body. The focus of the current study was to examine the detoxification of the carcinogenic diol form (DB[a,l]P-trans-11,12-diol) by glucuronidation. In order to understand the metabolism of this potent PAH by human UGT enzymes, HEK293 cell lines over-expressing individual UGTs were screened for glucuronidation activity toward DB[a,l]P-11,12-diol. Glucuronide products were quantified using an ultra-performance liquid chromatography (UPLC) method. Six UGTs (UGTs 1A1, 1A7, 1A8, 1A9, 1A10 and UGT2B7) were found to be highly active. Three glucuronide conjugates were observed in activity assays with UGT1A1 and 1A10, while only two glucuronides were formed with UGTs 1A7, 1A8, 1A9, and 2B7. Enzyme kinetic analysis indicated that UGT1A9 is the most active isoform among all the UGTs, exhibiting the highest Vmax/Km for the two glucuronide products it formed. These results suggest that multiple UGTs are involved in stereospecific glucuronidation of DB[a,l]P metabolites in humans. In addition to the further characterization of (DB[a,l]P-trans-11,12-diol) glucuronide conjugates, studies examining the role of polymorphisms in active UGTs on cancer risk are currently on-going. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3456.