ODC1 is a critical determinant of MYCN oncogenesis and a therapeutic target in neuroblastoma

Neuroblastoma is a frequently lethal childhood tumor in which MYC gene deregulation, commonly as MYCN amplification, portends poor outcome. Identifying the requisite biopathways downstream of MYC may provide therapeutic opportunities. We used transcriptome analyses to show that MYCN-amplified neuroblastomas have coordinately deregulated myriad polyamine enzymes (including ODC1, SRM, SMS, AMD1, OAZ2, and SMOX) to enhance polyamine biosynthesis. High-risk tumors without MYCN amplification also overexpress ODC1, the rate-limiting enzyme in polyamine biosynthesis, when compared with lower-risk tumors, suggesting that this pathway may be pivotal. Indeed, elevated ODC1 (independent of MYCN amplification) was associated with reduced survival in a large independent neuroblastoma cohort. As polyamines are essential for cell survival and linked to cancer progression, we studied polyamine antagonism to test for metabolic dependence on this pathway in neuroblastoma. The Odc inhibitor alpha-difluoromethylornithine (DFMO) inhibited neuroblast proliferation in vitro and suppressed oncogenesis in vivo. DFMO treatment of neuroblastoma-prone genetically engineered mice (TH-MYCN) extended tumor latency and survival in homozygous mice and prevented oncogenesis in hemizygous mice. In the latter, transient Odc ablation permanently prevented tumor onset consistent with a time-limited window for embryonal tumor initiation. Importantly, we show that DFMO augments antitumor efficacy of conventional cytotoxics in vivo. This work implicates polyamine biosynthesis as an arbiter of MYCN oncogenesis and shows initial efficacy for polyamine depletion strategies in neuroblastoma, a strategy that may have utility for this and other MYC-driven embryonal tumors.

Large molecular third-order optical nonlinearities in polarized carotenoids

Garito and co-workers have suggested a mechanism to dramatically increase the second hyperpolarizability, gamma, in linear pi-electron-conjugated molecules. Polarization is introduced that leads to a difference between the dipole moments of the molecule's ground state and excited state. Here a series of carotenoids was examined that had increasing intramolecular charge transfer (ICT) from the polyenic chain to the acceptor moiety in the ground state, and gamma was measured for these compounds as a function of wavelength by third-harmonic generation. The compound with the greatest ICT exhibited a 35-fold enhancement of gammamax (the gamma measured at the peak of the three-photon resonance) relative to the symmetric molecule beta-carotene, which itself has one of the largest third-order nonlinearities known. Stark spectroscopic measurements revealed the existence of a large difference dipole moment, Delta mu, between the ground and excited state. Quantum-chemical calculations underline the importance of interactions involving states with large Delta mu.

Maternal body mass index and risk of birth and maternal health outcomes in low- and middle-income countries: a systematic review and meta-analysis

We conducted a systematic review and meta-analysis of population-based cohort studies of maternal body mass index (BMI) and risk of adverse birth and health outcomes in low- and middle-income countries. PubMed, Embase, CINAHL and the British Nursing Index were searched from inception to February 2014. Forty-two studies were included. Our study found that maternal underweight was significantly associated with higher risk of preterm birth (odds ratio [OR], 1.13; 95% confidence interval [CI], 1.01-1.27), low birthweight (OR, 1.66; 95% CI, 1.50-1.84) and small for gestational age (OR, 1.85; 95% CI, 1.69-2.02). Compared with mothers with normal BMI, overweight or obese mothers were at increased odds of gestational diabetes, pregnancy-induced hypertension, pre-eclampsia, caesarean delivery and post-partum haemorrhage. The population-attributable risk (PAR) indicated that if women were entirely unexposed to overweight or obesity during the pre-pregnancy or early pregnancy period, 14% to 35% fewer women would develop gestational diabetes, pre-eclampsia or pregnancy-induced hypertension in Brazil, China, India, Iran or Thailand. The highest PAR of low birthweight attributable to maternal underweight was found in Iran (20%), followed by India (18%), Thailand (10%) and China (8%). Treatment and prevention of maternal underweight, overweight or obesity may help reduce the burden on maternal and child health in developing countries.

Polyamine-blocking therapy reverses immunosuppression in the tumor microenvironment

Correcting T-cell immunosuppression may unleash powerful antitumor responses; however, knowledge about the mechanisms and modifiers that may be targeted to improve therapy remains incomplete. Here, we report that polyamine elevation in cancer, a common metabolic aberration in aggressive lesions, contributes significantly to tumor immunosuppression and that a polyamine depletion strategy can exert antitumor effects that may also promote immunity. A polyamine-blocking therapy (PBT) that combines the well-characterized ornithine decarboxylase (ODC) inhibitor difluoromethylornithine (DFMO) with AMXT 1501, a novel inhibitor of the polyamine transport system, blocked tumor growth in immunocompetent mice but not in athymic nude mice lacking T cells. PBT had little effect on the proliferation of epithelial tumor cells, but it increased the number of apoptotic cells. Analysis of CD45(+) tumor immune infiltrates revealed that PBT decreased levels of Gr-1(+)CD11b(+) myeloid suppressor cells and increased CD3(+) T cells. Strikingly, in a model of neoadjuvant therapy, mice administered with PBT one week before surgical resection of engrafted mammary tumors exhibited resistance to subsequent tumor rechallenge. Collectively, our results indicate that therapies targeting polyamine metabolism do not act exclusively as antiproliferative agents, but also act strongly to prevent immune escape by the tumor. PBT may offer a general approach to heighten immune responses in cancer.

Combined effect of operational variables and enzyme activity on aqueous enzymatic extraction of oil and protein from soybean

The individual effect of two different enzymes-protease and cellulase-on oil and protein extraction yields combined with other process parameters-enzyme concentration, time of hydrolysis, particle size and solid-to-liquid ratio-was evaluated by Response Surface Methodology. The selection of the enzymes for the study was based on preliminary experiments that showed higher increments in the extraction yield with the use of the two enzymes when compared to hemicellulase and pectinase. The levels of the quantitative parameters studied were: i) enzyme concentration: 0.1, 0.45, 2 w/w %; ii) liquid-to-solid ratio: 0.05, 0.125, 0.2; iii) mean particle size: 212.5, 449.5, 855 µm; iv) time of hydrolysis: 30; 60; 120 min. Experimental data for both oil and protein extraction yields obtained with and without enzymes correlated very well with process parameters (P < 0.0001), resulting in models with high coefficient of determination for oil and protein extraction yields (r(2) = 0.9570 and r(2) = 0.9807, respectively). The use of protease resulted in significantly higher yields over the control (protein yield increased from 27.8 to 66.2%, oil yield increased from 41.8 to 58.7%) only when heat treated flour was used, or when non-heat treated flour with large particle sizes was used in the extraction. The yields of protein and oil from non-heat treated material in general decreased slightly with the use of enzymes.

The dobutamine stress test as an alternative to exercise testing after acute myocardial infarction

Three weeks after myocardial infarction in 50 patients the effect of the infusion of a graded dose of dobutamine was compared with that of symptom limited treadmill exercise testing. The following variables were measured: blood pressure, heart rate, ST segment changes, Doppler aortic blood flow, and cross sectional echocardiographic dimensions. The heart rate and double product increased more during exercise than during dobutamine infusion, while maximum acceleration in the ascending aorta increased more during dobutamine infusion than during exercise. Significant ST depression was recorded in 22 patients during exercise and in 24 during dobutamine infusion; the concordance between the two tests was 88%. In all cases in which ST segment depression occurred in both tests the site of ST depression was the same. Dobutamine stress testing is an alternative to exercise testing in patients after myocardial infarction.

Optimal atrioventricular delay at rest and during exercise in patients with dual chamber pacemakers: a non-invasive assessment by continuous wave Doppler

The optimal atrioventricular delay at rest and during exercise was investigated in nine patients with heart block and implanted dual chamber pacemakers. All patients studied had normal left ventricular function and a normal sinus node rate response to exercise. Cardiac output was measured by continuous wave Doppler and was calculated as the product of stroke distance measured by Doppler at the left ventricular outflow, aortic root area measured by M mode echocardiography, and heart rate. Pacemakers were programmed in the DDD mode. Cardiac output was measured with the patient at rest while supine and while erect and at the peak of submaximal exercise (the end of stage 1 of the Bruce protocol) with the pacemakers programmed to the following atrioventricular intervals: 75-80 ms, 100-110 ms, 140-150 ms, and 200 ms. During exercise the basic pacing rate was programmed to 70 beats/min. Cardiac output at rest while supine and erect was greatest with an atrioventricular delay of 140-150 ms and it was significantly higher than that with an atrioventricular delay of 75-80 ms. On average there was a 31% decrease in cardiac output when patients stood up. During treadmill exercise, however, cardiac output was greatest when the atrioventricular delay was 75-80 ms, and this was significantly higher than the cardiac output with atrioventricular delays of 150 and 200 ms. During exercise 1:1 atrioventricular relations were maintained in patients at all atrioventricular intervals. In patients with atrioventricular sequential pacemakers cardiac output at rest is greatest with an atrioventricular delay of 140-150 ms but during exercise the optimal atrioventricular delay is shorter. Rate modulation of the atrioventricular interval may improve the haemodynamic response and possibly exercise tolerance in patients with dual chamber pacemakers.

Maternal and perinatal outcomes among nulliparous adolescents in low- and middle-income countries: a multi-country study

OBJECTIVE

To investigate the risk of adverse pregnancy outcomes and caesarean section among adolescents in low- and middle-income countries.

DESIGN

Secondary analysis using facility-based cross-sectional data from the World Health Organization (WHO) Global Survey on Maternal and Perinatal Health.

SETTING

Twenty-three countries in Africa, Latin America, and Asia.

POPULATION

Women admitted for delivery in 363 health facilities during 2-3 months between 2004 and 2008.

METHODS

We constructed multilevel logistic regression models to estimate the effect of young maternal age on risks of adverse pregnancy outcomes.

MAIN OUTCOME MEASURES

Risk of adverse pregnancy outcomes among young mothers.

RESULTS

A total of 78 646 nulliparous mothers aged ≤24 years and their singleton infants were included in the analysis. Compared with mothers aged 20-24 years, adolescents aged 16-19 years had a significantly lower risk of caesarean section (adjusted OR 0.75, 95% CI 0.71-0.79). When the analysis was restricted to caesarean section indicated for presumed cephalopelvic disproportion, the risk of caesarean section was significantly higher among mothers aged ≤15 years (aOR 1.27, 95% CI 1.07-1.49) than among those aged 20-24 years. Higher risks of low birthweight and preterm birth were found among adolescents aged 16-19 years (aOR 1.10, 95% CI 1.03-1.17; aOR 1.16, 95% CI 1.09-1.23, respectively) and ≤15 years (aOR 1.33, 95% CI 1.14-1.54; aOR 1.56, 95% CI 1.35-1.80, respectively).

CONCLUSIONS

Adolescent girls experiencing pregnancy at a very young age (i.e. <16 years) have an increased risk of adverse pregnancy outcomes.

The effect of a low fructose and low glycemic index/load (FRAGILE) dietary intervention on indices of liver function, cardiometabolic risk factors, and body composition in children and adolescents with nonalcoholic fatty liver disease (NAFLD)

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a common liver disease in obese children. Diets high in added fructose (high fructose corn syrup; HFCS) and glycemic index (GI)/glycemic load (GL) are associated with increased risk of NAFLD. Lifestyle modification is the main treatment, but no guidelines regarding specific dietary interventions for childhood NAFLD exist. We hypothesized that reductions in dietary fructose (total, free, and HFCS)/GI/GL over 6 months would result in improvements in body composition and markers of liver dysfunction and cardiometabolic risk in childhood NAFLD.

METHODS

Children and adolescents with NAFLD (n = 12) and healthy controls (n = 14) 7-18 years were studied at baseline and 3 and 6 months post-dietary intervention. Plasma markers of liver dysfunction (ALT, AST, γGT), cardiometabolic risk (TG, total cholesterol, LDL-HDL cholesterol, Apo-B100, Apo-B48, Apo-CIII, insulin, homeostasis model of assessment of insulin resistance [HOMA-IR]), inflammation (TNF-α, IL-6, IL-10), anthropometric, and blood pressure (BP) were studied using validated methodologies.

RESULTS

Significant reductions in systolic BP (SBP), percentage body fat (BF), and plasma concentrations of ALT (P = .04), Apo-B100 (P < .001), and HOMA-IR were observed in children with NAFLD at 3 and 6 months (P < .05). Dietary reductions in total/free fructose/HFCS and GL were related to reductions in SBP (P = .01), ALT (P = .004), HOMA-IR (P = .03), and percentage BF in children with NAFLD. Reductions in dietary GI were associated with reduced plasma Apo-B100 (P = .02) in both groups. With the exception of Apo-B100, no changes in laboratory variables were observed in the control group.

CONCLUSION

Modest reductions in fructose (total/free, HFCS) and GI/GL intake result in improvements of plasma markers of liver dysfunction and cardiometabolic risk in childhood NAFLD.

Co-operation between follicular ornithine decarboxylase and v-Ha-ras induces spontaneous papillomas and malignant conversion in transgenic skin

Ornithine decarboxylase (ODC) is aberrantly regulated in tumor cells and results in high basal levels of ODC and polyamines in many epithelial tumors. To determine if elevated ODC/polyamine levels can co-operate with a mutant Ha-ras gene in mouse skin tumorigenesis, double transgenic mice were generated by breeding K6/ODC transgenic mice with TG.AC v-Ha-ras transgenic mice. A K6 keratin promoter drives the ODC transgene in K6/ ODC transgenic mice, which results in elevated ODC/ polyamine levels directed to the outer root sheath cells of hair follicles. TG.AC transgenic mice carry a v-Ha-ras transgene while still retaining two normal c-Ha-ras alleles. Transgenic mice that possess only the K6/ODC or the v-Ha-ras transgene did not develop tumors unless treated with either a carcinogen or a tumor promoter, respectively. However, a high percentage of double transgenic mice possessing both the K6/ODC and v-Ha-ras transgenes developed spontaneous tumors. All tumors were well-differentiated keratoacanthomas, some of which progressed to carcinomas within 2 months. The development and the maintenance of these ODC/ras tumors was ODC-dependent since alpha-difluoromethylornithine (DFMO), a specific ODC inhibitor, prevented the formation and caused the regression of these tumors. These findings indicate that ODC overexpression and an activated Ha-ras are sufficient to produce a high rate of malignant transformation in an animal model. The ODC/ras double transgenic mouse provides a simple in vivo model without the use of chemical carcinogens or tumor promoters in which to test downstream effectors that play a key role in mediating the development of epithelial tumors resulting from the cooperation between ODC and v-Ha-ras.

Polyamines and nonmelanoma skin cancer

Elevated levels of polyamines have long been associated with skin tumorigenesis. Tightly regulated metabolism of polyamines is critical for cell survival and normal skin homeostasis, and these controls are dysregulated in skin tumorigenesis. A key enzyme in polyamine biosynthesis, ornithine decarboxylase (ODC) is upregulated in skin tumors compared to normal skin. Use of transgenic mouse models has demonstrated that polyamines play an essential role in the early promotional phase of skin tumorigenesis. The formation of skin tumors in these transgenic mice is dependent upon polyamine biosynthesis, especially putrescine, since treatment with inhibitors of ODC activity blocks the formation of skin tumors and causes the rapid regression of existing tumors. Although the mechanism by which polyamines promote skin tumorigenesis are not well understood, elevated levels of polyamines have been shown to stimulate epidermal proliferation, alter keratinocyte differentiation status, increase neovascularization, and increase synthesis of extracellular matrix proteins in a manner similar to that seen in wound healing. It is becoming increasingly apparent that elevated polyamine levels activate not only epidermal cells but also underlying stromal cells in the skin to promote the development and progression of skin tumors. The inhibition of polyamine biosynthesis has potential to be an effective chemoprevention strategy for nonmelanoma skin cancer.

A novel polyamine blockade therapy activates an anti-tumor immune response

Most tumors maintain elevated levels of polyamines to support their growth and survival. This study explores the anti-tumor effect of polyamine starvation via both inhibiting polyamine biosynthesis and blocking the upregulated import of polyamines into the tumor. We demonstrate that polyamine blockade therapy (PBT) co-treatment with both DFMO and a novel polyamine transport inhibitor, Trimer PTI, significantly inhibits tumor growth more than treatment with DFMO or the Trimer PTI alone. The anti-tumor effect of PBT was lost in mice where CD4⁺ and CD8⁺ T cells were antibody depleted, implying that PBT stimulates an anti-tumor immune effect that is T-cell dependent. The PBT anti-tumor effect was accompanied by an increase in granzyme B⁺, IFN-γ⁺ CD8⁺ T-cells and a decrease in immunosuppressive tumor infiltrating cells including Gr-1⁺CD11b⁺ myeloid derived suppressor cells (MDSCs), CD4⁺CD25⁺ Tregs, and CD206⁺F4/80⁺ M2 macrophages. Stimulation with tumor-specific peptides elicited elevated antigen-specific IFN-γ secretion in splenocytes from PBT-treated mice, indicating that PBT treatment stimulates the activation of T-cells in a tumor-specific manner. These data show that combined treatment with both DFMO and the Trimer PTI not only deprives polyamine-addicted tumor cells of polyamines, but also relieves polyamine-mediated immunosuppression in the tumor microenvironment, thus allowing the activation of tumoricidal T-cells.

Assessment of psychoeducational outcomes after pediatric liver transplant

Outcomes research in pediatric liver transplant (LT) has focused on mortality and morbidity but there is a need to also evaluate functional outcomes. Standardized cognitive testing was administered to a cohort of children with infantile chronic liver disease who were transplanted at the University of Alberta during their preschool years. Thirty children had comprehensive assessments with the Bayley Scales of Infant Development or Wechsler testing. Patient variables potentially associated with cognitive delay were analyzed with multiple regression analysis. The mean DQ/IQ score (developmental quotient/intelligence quotient) was 81 +/- 17. Delay (DQ/IQ score < 70), and borderline delay (DQ/IQ 70-84) were each present in 27% of the cohort, with only 46% demonstrating normal cognition. Regression analysis demonstrated that the decreased IQ was associated with pretransplant growth retardation and elevated calcineurin inhibitor levels. Performance IQ had strong correlation with pretransplant growth retardation and elevated serum ammonia, R(2)= 45%, compared to verbal IQ that was associated was elevated calcineurin inhibitor levels, R(2)= 23%. Children post-LT are at high risk for cognitive delay or borderline delay. This is the first study to demonstrate the association calcineurin inhibitors with impaired IQ and also the unique finding of different variables predictive of impaired verbal intelligence quotient (VIQ) versus performance intelligence quotient (PIQ).

Polyamine Antagonist Therapies Inhibit Neuroblastoma Initiation and Progression

PURPOSE

Deregulated MYC drives oncogenesis in many tissues yet direct pharmacologic inhibition has proven difficult. MYC coordinately regulates polyamine homeostasis as these essential cations support MYC functions, and drugs that antagonize polyamine sufficiency have synthetic-lethal interactions with MYC Neuroblastoma is a lethal tumor in which the MYC homologue MYCN, and ODC1, the rate-limiting enzyme in polyamine synthesis, are frequently deregulated so we tested optimized polyamine depletion regimens for activity against neuroblastoma.

EXPERIMENTAL DESIGN

We used complementary transgenic and xenograft-bearing neuroblastoma models to assess polyamine antagonists. We investigated difluoromethylornithine (DFMO; an inhibitor of Odc, the rate-limiting enzyme in polyamine synthesis), SAM486 (an inhibitor of Amd1, the second rate-limiting enzyme), and celecoxib (an inducer of Sat1 and polyamine catabolism) in both the preemptive setting and in the treatment of established tumors. In vitro assays were performed to identify mechanisms of activity.

RESULTS

An optimized polyamine antagonist regimen using DFMO and SAM486 to inhibit both rate-limiting enzymes in polyamine synthesis potently blocked neuroblastoma initiation in transgenic mice, underscoring the requirement for polyamines in MYC-driven oncogenesis. Furthermore, the combination of DFMO with celecoxib was found to be highly active, alone, and combined with numerous chemotherapy regimens, in regressing established tumors in both models, including tumors harboring highest risk genetic lesions such as MYCN amplification, ALK mutation, and TP53 mutation with multidrug resistance.

CONCLUSIONS

Given the broad preclinical activity demonstrated by polyamine antagonist regimens across diverse in vivo models, clinical investigation of such approaches in neuroblastoma and potentially other MYC-driven tumors is warranted. Clin Cancer Res; 22(17); 4391-404. ©2016 AACR.

Use of dabigatran etexilate to reduce breast cancer progression

Coagulation proteases and the generation of thrombin are increased in breast tumor epithelial and stromal cells. Since thrombin can modify tumor cell behavior directly through the activation of protease-activated receptors (PARs) or indirectly by generating fibrin matrices, the effect of dabigatran etexilate, a direct thrombin inhibitor, on breast cancer development was evaluated. Dabigatran inhibited invasiveness of MDA-MB-231 breast carcinoma cells across Matrigel-coated membranes at concentrations that had no effect on the proliferation index of cultured tumor cells. In vivo evaluation of invasiveness of MDA-MB-231 cells in tracheal xenotransplants in nude mice orally administered dabigatran etexilate twice daily at a dose of 45 mg/kg over 4 weeks demonstrated less invasion of tumor cells through the tracheal wall compared to vehicle-treated mice. To evaluate the effect of dabigatran on the development of metastatic foci, 4T1 tumor cells were injected orthotopically in the mammary fat pads of syngeneic Balb/c mice. Dabigatran etexilate treatment exhibited evidence of antitumor activity with a 50% reduction in tumor volume at 4 weeks following orthotopic injection of 4T1 cells in syngeneic Balb/c mice with no weight loss in treated mice. Dabigatran etexilate reduced both 4T1 tumor cells in the blood and liver micrometastases by 50-60%. These results suggest that oral administration of the direct thrombin inhibitor, dabigatran etexilate, inhibits both invasion and metastasis of malignant breast tumors, suggesting that it may be beneficial in not only preventing thrombotic events in cancer patients, but also as adjunct therapy to treat malignant tumors.

Psychosocial and cognitive factors associated with adherence to dietary and fluid restriction regimens by people on chronic haemodialysis

BACKGROUND

Failure by people on chronic haemodialysis to adhere adequately to dietary and fluid restrictions can have serious medical consequences. Numerous psychosocial factors possibly associated with adherence have been investigated in previous research. However, most previous studies have examined one or a few variables in isolation, and have tended to focus on sociodemographic variables not easily amenable to intervention. Much previous work has tended to ignore potential differences in adherence between male and female dialysands.

METHODS

Sociodemographic and psychosocial factors associated with adherence to dietary and fluid restrictions were investigated in 45 people on haemodialysis attending one renal unit, excluding those with a residual urine volume > 500 ml/day. Multiple regression analyses were used to estimate the contribution to adherence of a range of variables, including gender, age, duration of dialysis, affective disturbance, past psychiatric history, health locus of control, social adjustment and social supports.

RESULTS

Adherence to diet (measured by predialysis serum potassium) and to fluid restriction (interdialysis weight gain) were not linked, and had different psychosocial correlates. Regression models of four different aspects of adherence revealed very distinct psychosocial correlates, with contributions to adherence from complex interactions between psychosocial and cognitive variables, notably gender, age, social adjustment, health locus of control, and depression.

CONCLUSIONS

The findings cast doubt on the results of many previous studies which have used simple models of adherence. Adherence is likely to be influenced in a complex manner by multiple factors including age, gender, locus of control, social adjustment, and past psychiatric history.

Non-hematopoietic expression of IDO is integrally required for inflammatory tumor promotion

Indoleamine 2,3-dioxygenase (IDO) is generally considered to be immunosuppressive but recent findings suggest this characterization oversimplifies its role in disease pathogenesis. Recently, we showed that IDO is essential for tumor outgrowth in the classical two-stage model of inflammatory skin carcinogenesis. Here, we report that IDO loss did not exacerbate classical inflammatory responses. Rather, IDO induction could be elicited by environmental signals and tumor promoters as an integral component of the inflammatory tissue microenvironment even in the absence of cancer. IDO loss had limited impact on tumor outgrowth in carcinogenesis models that lacked an explicit inflammatory tumor promoter. In the context of inflammatory carcinogenesis where IDO was critical to tumor development, the most important source of IDO was radiation-resistant non-hematopoietic cells, consistent with evidence that loss of the IDO regulatory tumor suppressor gene Bin1 in transformed skin cells facilitates IDO-mediated immune escape by a cell autonomous mechanism. Taken together, our results identify IDO as an integral component of 'cancer-associated' inflammation that tilts the immune system toward tumor support. More generally, they promote the concept that mediators of immune escape and cancer-associated inflammation may be genetically synonymous.

Ornithine decarboxylase expression leads to translocation and activation of protein kinase CK2 in vivo

Ornithine decarboxylase (ODC) is the key initial enzyme in the biosynthesis of polyamines. Since polyamines have been shown to enhance protein kinase CK2 activity in vitro, ODC was overexpressed to examine the role of polyamines in CK2 regulation in vivo. Infection of Balb/MK cells with an ODC retrovirus to elevate ODC and polyamine levels increased overall protein phosphorylation as well as CK2 protein levels and enzyme activity in mimosine- or nocodazole- arrested cells. Immunofluorescence microscopy and enzyme analyses of subcellular fractions from ODC-overexpressing cells demonstrated translocation of CK2 from the cytoplasm to the nucleus with no apparent loss of cytoplasmic CK2 activity, suggesting polyamine activation of the remaining cytoplasmic enzyme. Similarly, K6/ODC transgenic mice exhibited higher ODC and CK2 enzyme activities than their normal littermates. ODC-immunostained cells in the transgenic skin also stained intensely for CK2 protein. Primary cultures of K6/ODC keratinocytes also exhibited increased ODC and CK2 enzyme activities compared with those from normal littermates. However, the addition of difluoromethylornithine, a specific ODC inhibitor, to the transgenic keratinocytes reduced both intracellular polyamine levels and CK2 enzyme activity. These results suggest that polyamines regulate the CK2 enzyme by affecting its cellular distribution as well as its enzyme activity and levels.

K6/ODC transgenic mice as a sensitive model for carcinogen identification

Ornithine decarboxylase (ODC), an important enzyme in the polyamine biosynthetic pathway, is aberrantly regulated in many epithelial tumors of rodents and humans. In murine skin, it has been shown that ODC overexpression provides a sufficient condition for tumor promotion. Therefore, we hypothesized that K6/ODC transgenic mice in which ODC overexpression was targeted to hair follicle keratinocytes might provide a sensitive model for identifying genotoxic carcinogens. Ten known carcinogens or noncarcinogens have been tested in the model so far and results are highly concordant with 2-year rodent bioassays (100% concordant). More importantly, each of two chemicals tested that is recognized as a human carcinogen was identified as a carcinogen in K6/ODC transgenic mice. In addition, 7, 12-dimethylbenz(a)anthracene (DMBA) dose response studies indicated that even at a very low dose, 2 nmol, a high percentage of mice (50%) had already developed tumors 8 weeks after treatment. We conclude that the K6/ODC transgenic mouse model is very sensitive to topical application of genotoxic carcinogens and could therefore be a useful mouse model for carcinogen identification and chemical risk assessment.

Polyamine Blocking Therapy Decreases Survival of Tumor-Infiltrating Immunosuppressive Myeloid Cells and Enhances the Antitumor Efficacy of PD-1 Blockade

Despite unprecedented advances in the treatment of cancer through the use of immune checkpoint blockade (ICB), responses are not universal and alternative strategies are needed to enhance responses to ICB. We have shown previously that a novel polyamine blocking therapy (PBT), consisting of cotreatment with α-difluoromethylornithine (DFMO) to block polyamine biosynthesis and a Trimer polyamine transport inhibitor, decreases myeloid-derived suppressor cells (MDSC) and M2-like tumor-associated macrophages (TAM). Both MDSCs and TAMs promote tumor progression, inhibit antitumor immunity, and limit the efficacy of ICB. In this study, we investigated the use of PBT to heighten therapeutic responses to PD-1 blockade in mice bearing 4T1 mammary carcinoma and B16F10 melanoma tumors. Whereas PBT inhibited primary tumor growth in both tumor models, 4T1 lung metastases were also dramatically decreased in mice treated with PBT. Reductions in MDSC and TAM subpopulations in 4T1 tumors from PBT-treated mice were accompanied by reduced cytoprotective autophagy only in tumor-infiltrating MDSC and macrophage subpopulations but not in the lung or spleen. PBT treatment blunted M2-like alternative activation of bone marrow-derived macrophages and reduced STAT3 activation in MDSC cultures while increasing the differentiation of CD80⁺, CD11c⁺ macrophages. PBT significantly enhanced the antitumor efficacy of PD-1 blockade in both 4T1 and B16F10 tumors resistant to anti-PD-1 monotherapy, increasing tumor-specific cytotoxic T cells and survival of tumor-bearing animals beyond that with PBT or PD-1 blockade alone. Our results suggest that cotreatment with DFMO and the Trimer polyamine transport inhibitor may improve the therapeutic efficacy of immunotherapies in patients with cancer with resistant tumors.

Translational development of difluoromethylornithine (DFMO) for the treatment of neuroblastoma

Neuroblastoma is a childhood tumor in which MYC oncogenes are commonly activated to drive tumor progression. Survival for children with high-risk neuroblastoma remains poor despite treatment that incorporates high-dose chemotherapy, stem cell support, surgery, radiation therapy and immunotherapy. More effective and less toxic treatments are sought and one approach under clinical development involves re-purposing the anti-protozoan drug difluoromethylornithine (DFMO; Eflornithine) as a neuroblastoma therapeutic. DFMO is an irreversible inhibitor of ornithine decarboxylase (Odc), a MYC target gene, bona fide oncogene, and the rate-limiting enzyme in polyamine synthesis. DFMO is approved for the treatment of Trypanosoma brucei gambiense encephalitis ("African sleeping sickness") since polyamines are essential for the proliferation of these protozoa. However, polyamines are also critical for mammalian cell proliferation and the finding that MYC coordinately regulates all aspects of polyamine metabolism suggests polyamines may be required to support cancer promotion by MYC. Pre-emptive blockade of polyamine synthesis is sufficient to block tumor initiation in an otherwise fully penetrant transgenic mouse model of neuroblastoma driven by MYCN, underscoring the necessity of polyamines in this process. Moreover, polyamine depletion regimens exert potent anti-tumor activity in pre-clinical models of established neuroblastoma as well, in combination with numerous chemotherapeutic agents and even in tumors with unfavorable genetic features such as MYCN, ALK or TP53 mutation. This has led to the testing of DFMO in clinical trials for children with neuroblastoma. Current trial designs include testing lower dose DFMO alone (2,000 mg/m(2)/day) starting at the completion of standard therapy, or higher doses combined with chemotherapy (up to 9,000 mg/m(2)/day) for patients with relapsed disease that has progressed. In this review we will discuss important considerations for the future design of DFMO-based clinical trials for neuroblastoma, focusing on the need to better define the principal mechanisms of anti-tumor activity for polyamine depletion regimens. Putative DFMO activities that are both cancer cell intrinsic (targeting the principal oncogenic driver, MYC) and cancer cell extrinsic (altering the tumor microenvironment to support anti-tumor immunity) will be discussed. Understanding the mechanisms of DFMO activity are critical in determining how it might be best leveraged in upcoming clinical trials. This mechanistic approach also provides a platform by which iterative pre-clinical testing using translational tumor models may complement our clinical approaches.

Pharmacokinetics, Safety, and Efficacy of Glecaprevir/Pibrentasvir in Children With Chronic HCV: Part 2 of the DORA Study

BACKGROUND AND AIMS

Glecaprevir/pibrentasvir (GLE/PIB) has shown high efficacy and safety in chronic HCV-infected adults and adolescents; data in children were limited. DORA part 2 is a phase 2/3, nonrandomized, open-label study evaluating the pharmacokinetics, efficacy, and safety of a pediatric formulation of GLE and PIB in children ages 3 to < 12 years.

APPROACH AND RESULTS

Children with chronic HCV infection, genotype 1-6, with or without compensated cirrhosis, were divided into three cohorts by age-cohort 2 (9 to < 12 years), cohort 3 (6 to < 9 years), and cohort 4 (3 to < 6 years)-and given weight-based doses of GLE and PIB for 8, 12, or 16 weeks. Primary endpoints were sustained virologic response at posttreatment week 12 (SVR12) and steady-state exposure; secondary endpoints were rates of persistent viremia, relapse, and reinfection. Safety and laboratory abnormalities were assessed. Final pediatric dosages determined to be efficacious were 250 mg GLE + 100 mg PIB (in children weighing ≥ 30 to < 45 kg), 200 mg GLE + 80 mg PIB (≥ 20 to < 30 kg), and 150 mg GLE + 60 mg PIB (12 to < 20 kg). Of 80 participants enrolled and dosed, 96% (77/80) achieved SVR12. One participant, on the initial dose ratio, relapsed by posttreatment week 4; no participants had virologic failures on the final dose ratio of GLE 50 mg/PIB 20 mg. Two nonresponders prematurely discontinued the study. Most adverse events (AEs) were mild; no drug-related serious AEs occurred. Pharmacokinetic exposures were comparable to those of adults.

CONCLUSIONS

A pediatric formulation of GLE/PIB was highly efficacious and well tolerated in chronic HCV-infected children 3 to < 12 years old.

Experiences and barriers to Health-Related Quality of Life following liver transplantation: a qualitative analysis of the perspectives of pediatric patients and their parents

This paper examines health-related quality of life (HRQOL) experiences and barriers facing young people who have received a liver transplant (LT). Semi-structured qualitative interviews were conducted with children and adolescents who have undergone LT and their parents. Findings indicate that LT fosters substantially improved child and adolescent HRQOL; however, young people also experience challenges such as difficulties with medication compliance, self-management of care routines, physical activity restrictions, and undesirable medical procedures. Implications and recommendations for clinical practice and research are discussed.