Microphthalmia-associated transcription factor suppresses invasion by reducing intracellular GTP pools.

Melanoma progression is associated with increased invasion and, often, decreased levels of microphthalmia-associated transcription factor (MITF). Accordingly, downregulation of MITF induces invasion in melanoma cells; however, little is known about the underlying mechanisms. Here, we report for the first time that depletion of MITF results in elevation of intracellular GTP levels and increased amounts of active (GTP-bound) RAC1, RHO-A and RHO-C. Concomitantly, MITF-depleted cells display larger number of invadopodia and increased invasion. We further demonstrate that the gene for guanosine monophosphate reductase (GMPR) is a direct MITF target, and that the partial repression of GMPR accounts mostly for the above phenotypes in MITF-depleted cells. Reciprocally, transactivation of GMPR is required for MITF-dependent suppression of melanoma cell invasion, tumorigenicity and lung colonization. Moreover, loss of GMPR accompanies downregulation of MITF in vemurafenib-resistant BRAFV600E-melanoma cells and underlies the increased invasion in these cells. Our data uncover novel mechanisms linking MITF-dependent inhibition of invasion to suppression of guanylate metabolism.

Mitochondrial thioredoxin reductase regulates major cytotoxicity pathways of proteasome inhibitors in multiple myeloma cells.

It is generally accepted that intracellular oxidative stress induced by proteasome inhibitors is a byproduct of endoplasmic reticulum (ER) stress. Here we report a mechanism underlying the ability of proteasome inhibitors bortezomib (BTZ) and carfilzomib (CFZ) to directly induce oxidative and ER stresses in multiple myeloma (MM) cells via transcriptional repression of a gene encoding mitochondrial thioredoxin reductase (TXNRD2). TXNRD2 is critical for maintenance of intracellular red-ox status and detoxification of reactive oxygen species. Depletion of TXNRD2 to the levels detected in BTZ- or CFZ-treated cells causes oxidative stress, ER stress and death similar to those induced by proteasome inhibitors. Reciprocally, restoration of near-wildtype TXNRD2 amounts in MM cells treated with proteasome inhibitors reduces oxidative stress, ER stress and cell death by ~46%, ~35% and ~50%, respectively, compared with cells with unrestored TXNRD2 levels. Moreover, cells from three MM cell lines selected for resistance to BTZ demonstrate elevated levels of TXNRD2, indirectly confirming its functional role in BTZ resistance. Accordingly, ectopic expression of TXNRD2 in MM cell xenografts in immunocompromised mice blunts therapeutic effects of BTZ. Our data identify TXNRD2 as a potentially clinically relevant target, inhibition of which is critical for proteasome inhibitor-dependent cytotoxicity, oxidative stress and ER stress.

Pharmacological targeting of guanosine monophosphate synthase suppresses melanoma cell invasion and tumorigenicity.

Malignant melanoma possesses one of the highest metastatic potentials among human cancers. Acquisition of invasive phenotypes is a prerequisite for melanoma metastases. Elucidation of the molecular mechanisms underlying melanoma invasion will greatly enhance the design of novel agents for melanoma therapeutic intervention. Here, we report that guanosine monophosphate synthase (GMPS), an enzyme required for the de novo biosynthesis of GMP, has a major role in invasion and tumorigenicity of cells derived from either BRAF(V600E) or NRAS(Q61R) human metastatic melanomas. Moreover, GMPS levels are increased in metastatic human melanoma specimens compared with primary melanomas arguing that GMPS is an attractive candidate for anti-melanoma therapy. Accordingly, for the first time we demonstrate that angustmycin A, a nucleoside-analog inhibitor of GMPS produced by Streptomyces hygroscopius efficiently suppresses melanoma cell invasion in vitro and tumorigenicity in immunocompromised mice. Our data identify GMPS as a powerful driver of melanoma cell invasion and warrant further investigation of angustmycin A as a novel anti-melanoma agent.

Zinc supplementation in infants born small for gestational age reduces mortality: a prospective, randomized, controlled trial.

BACKGROUND: Low birth weight infants have been noted to have low zinc concentrations in cord blood, and zinc deficiency in childhood is associated with reduced immunocompetence and increased infectious disease morbidity. This study investigates whether zinc supplementation of infants born full term and small for gestational age affects mortality. METHODS: A randomized, double-blind, controlled trial with 2-by-2 factorial design enrolled 1154 full-term small for gestational age infants to receive in syrup 1 of the following: riboflavin; riboflavin and zinc (5 mg as sulfate); riboflavin, calcium, phosphorus, folate, and iron; or riboflavin, zinc, calcium, phosphorus, folate, and iron. A fixed dosage of 5 mL per child was given daily from 30 to 284 days of age. Household visits were made 6 days per week to provide the syrup and conduct surveillance for illness and death. When a child's death was reported, parental reports and medical records were used to ascertain the cause. The effects of zinc and of the combination of iron, folate, calcium, and phosphorus were analyzed by intent to treat. The mortality analysis was performed using a survival analytic approach that models time until death as the dependent variable; all models had 2 terms as independent variables: 1 for the zinc effect and 1 for the vitamin and mineral (calcium and phosphorus, folate and iron) effect. RESULTS: Zinc supplementation was associated with significantly lower mortality, with a rate ratio of 0.32 (95% confidence interval: 0.12-0.89). Calcium, phosphorus, folate, and iron supplementation was not associated with a mortality reduction, although a statistically nonsignificant trend toward reduction was observed with a rate ratio of 0.88 (95% confidence interval: 0.36-2.15). CONCLUSIONS: Zinc supplementation in small for gestational age infants can result in a substantial reduction in infectious disease mortality.

Clinical trial of benidipine in mild to moderate hypertension.

Thirty four patients with mild to moderate hypertension, were put on benidipine 4 mg/day after two weeks of placebo therapy. Twenty five patients completed the trial successfully for 4 mg benidipine. The blood pressure of 20 patients was controlled with benidipine 4 mg/day (effective rate 80%). Five patients with unsatisfactory control on 4 mg/day benidipine were put on 8 mg/day. Four of them were controlled and one was considered as failure (effective rate 80%). Most of the patients tolerated the drug well. Three patients had mild side effects like headache and heaviness in the head. One of them also had puffiness of face and body (on benidipine 8 mg/day) and was withdrawn from the study. One patient had mild constipation. We conclude that benidipine is well tolerated in the dose of 4-8 mg/day and is an effective antihypertensive agent for treatment of patients with mild to moderate hypertension.

Efficacy of antimicrobial treatment in non-dysenteric persistent diarrhoea in a community setting.

OBJECTIVES: To determine the efficacy of antimicrobial treatment in non-dysenteric persistent diarrhoea in a community setting. METHODS: In this double-blind field trial, 156 children aged 4-36 months with persistent diarrhoea not associated with Giardia lamblia infestation seeking treatment in a community outpatient clinic, were randomized to receive a combination of nalidixic acid and metronidazole, metronidazole alone, or placebo for 7 days. RESULTS: In comparison with placebo, metronidazole treatment did not result in a significant reduction in the mean post-enrollment diarrhoeal duration and stool frequency, increase in the proportion of patients recovered by days 3, 5 and 7 of treatment, and increase in weight gain at days 7 and 14. Comparing the combination of nalidixic acid and metronidazole with metronidazole alone, 17.5% more children treated with the combination recovered by day 3 of treatment (p = 0.08) and the mean stool frequency ascertained on day 7 for the previous 24 h was 26.8% less in them (p = 0.05). The weight gains at days 7 and 14 were similar in the two groups. CONCLUSIONS: These findings indicate that metronidazole offers no therapeutic benefit in persistent diarrhoea not associated with Giardia lamblia and nalidixic acid has only a modest clinical benefit, which is not substantial enough to warrant its routine use.

Pregnancy associated anemia and iron: a pilot study.

Iron deficiency occurs when the rate of loss of utilization exceeds its assimilation. Treatment is based on iron supplementation but due to side effects compliance to iron therapy is poor. A double blind comparative study was done using a novel time release preparation of ferrous sulphate (Code A) v.s. sustained release ferrous sulphate preparation (Code B) on 60 pregnant women in mid or late pregnancy with anaemia. The amount of ferrous sulphate in Code A was less than half of Code B. The patients were sequentially randomised as Code A or Code B recipient. The non compliance rate was 33%, and for both Code A & Code B. The mean improvement in hemoglobin after 4 weeks of therapy was 2.01 gm% for Code A and 2.3 gm% for Code B. Iron absorption as evidenced by improvement in S. Iron, TIBC and ferritin levels was better with Code A. The improvement in subjective symptoms of anaemia was better than average in Code B preparation. Code A group had comparatively more side effects both major and minor, this may have been the reason for a slightly higher drop out rate in this group. In conclusion the timed release preparation has a comparable haematological response and better absorption with significantly lower doses as compared to the sustained release preparation.