SmgGDS splice variants: Potential novel targets for breast cancer therapeutics

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Background: Breast cancer malignancy is promoted by the small GTPases K-Ras, Rap1, RhoA, and Rac1. We recently reported that the activity of these GTPases is regulated by two splice variants of SmgGDS, named SmgGDS-558 and SmgGDS-607. SmgGDS is overexpressed in lung and prostate cancer, but its role in breast cancer is unknown. Here we examine whether SmgGDS splice variants are expressed in breast cancer and promote breast cancer malignancy.

Methods: Immunohistochemical staining for SmgGDS was performed on archival human breast tumors (N=183) and normal breast tissue (N=22). Immunoblotting was used to detect SmgGDS splice variants in human breast cancer cell lines. siRNAs that silence different SmgGDS splice variants were used to examine the effects of SmgGDS knockdown on breast cancer cell spreading, cell proliferation via [3H]thymidine uptake, anchorage-independent cell growth using soft agar colony assays, and NF-kB activation using luciferase reporter assays.

Results: SmgGDS expression was detected in >65% of DCIS and invasive lobular and ductal carcinoma, and in 100% of metastatic tumors, but was detected in only 18% of normal breast tissue specimens (p<0.01). All tested cell lines expressed both SmgGDS splice variants. Silencing SmgGDS-558 or SmgGDS-607 with siRNA significantly diminished cell proliferation (100±2.0 vs. 11.3±1.0 vs. 50.5±2.2, p<0.05) in MCF-7 cells, with similar results in MDA-MB-231 and T47D cells. MCF-7 soft agar colony formation was significantly decreased 71% and 49% when SmgGDS-558 or SmgGDS-607 was silenced. MCF-7 cell spreading was promoted by silencing SmgGDS-558, but not SmgGDS-607. NF-kB activation was also decreased by 30% in resting and TNF-α-treated MCF-7 and MDA-MB-231 cells by silencing either splice variant.

Conclusions: SmgGDS is disproportionally expressed in human breast cancers. Reduction of SmgGDS-558 and SmgGDS-607 levels dramatically reduced breast cancer cell proliferation, soft agar colony formation, and NF-kB activation. Our results indicate that SmgGDS splice variants regulate breast cancer malignancy, most likely through their regulation of small GTPases. This study identifies SmgGDS splice variants as novel therapeutic targets in breast cancer.

Targeted gene silencing of TLR4 using liposomal nanoparticles for preventing liver ischemia reperfusion injury

RNAi-based therapy is a promising strategy for the prevention of ischemia-reperfusion injury (IRI). However, systemic administration of small interfering RNA (siRNA) may cause globally nonspecific targeting of all tissues, which impedes clinical use. Here we report a hepatocyte-specific delivery system for the treatment of liver IRI, using galactose-conjugated liposome nanoparticles (Gal-LipoNP). Heptocyte-specific targeting was validated by selective in vivo delivery as observed by increased Gal-LipoNP accumulation and gene silencing in the liver. Gal-LipoNP TLR4 siRNA treatment resulted in a significant decrease of serum alanine transferase (ALT) and aspartate transaminase (AST) in a hepatic IRI model. Histopathology displayed an overall reduction of the injury area in the Gal-LipoNP TLR4 siRNA treated mice. Additionally, neutrophil accumulation and lipid peroxidase-mediated tissue injury, detected by MPO, MDA and ROS respectively, were attenuated after Gal-LipoNP TLR4 siRNA treatment. Moreover, therapeutic effects of Gal-LipoNP TLR4 siRNA were associated with suppression of the inflammatory cytokines IL-1 and TNF-α. Taken together, this study is the first demonstration of liver IRI treatment using liver-specific siRNA delivery.

Curcumin improves insulin resistance in skeletal muscle of rats

BACKGROUND AND AIMS

Curcumin has been reported to lower plasma lipids and glucose in diabetic rats, and to decrease body weight in obese rats, which may partly be due to increased fatty acid oxidation and utilization in skeletal muscle.

METHODS AND RESULTS

Diabetic rats induced by high-fat diet plus streptozotocin (STZ, 30 mg/kg BW) were fed a diet containing 50, 150, or 250 mg/kg BW curcumin for 7 wk. Curcumin dose-dependently decreased plasma lipids and glucose and the dose 150 mg/kg BW appeared to be adequate to produce a significant effect. Curcumin supplementation reduced glucose and insulin tolerance measured as areas under the curve. L6 myotubes were treated with palmitate (0.25 mmol/L) in the presence of different levels of curcumin for 24 h in our in vitro experiment. Curcumin at 10 μmol/L was adequate to cause a significant increase in 2-deoxy-[(3)H]d-glucose uptake by L6 myotubes. Curcumin up-regulated expression of phosphorylated AMP-activated protein kinase (AMPK), CD36, and carnitine palmitoyl transferase 1, but down-regulated expression of pyruvate dehydrogenase 4 and phosphorylated glycogen synthase (GS) in both in vivo and in vitro studies. Moreover, curcumin increased phosphorylated acetyl COA carboxylase in L6 myotubes. The effects of curcumin on these enzymes except for GS were suppressed by AMPK inhibitor, Compound C. LKB1, an upstream kinase of AMPK, was activated by curcumin and inhibited by radicicol, an LKB1 destabilizer.

CONCLUSION

Curcumin improves muscular insulin resistance by increasing oxidation of fatty acid and glucose, which is, at least in part, mediated through LKB1-AMPK pathway.

Impulse control disorders in Chinese Parkinson's disease patients: the effect of ergot derived dopamine agonist

OBJECTIVE

We studied the prevalence and related risk factors of impulse control disorders in Chinese Parkinson's disease patients.

METHOD

We screened all non-demented Parkinson's disease patients attending our Parkinson's disease clinic from August 2009 to March 2010. The clinical characteristics of patients with impulse control disorders and those without were compared.

RESULTS

Of the 213 PD subjects screened, 15 (7.0%) with impulse control disorders were identified. Fourteen of these subjects were on both a dopamine agonist and Levodopa, and one was on Levodopa alone. Of the fourteen subjects on both a dopamine agonist and Levodopa, eleven were on bromocriptine and Levodopa; 10.5% of the subjects exposed to bromocriptine had impulse control disorder. Upon multivariate analysis, dose of dopamine agonist used, young age at onset of Parkinson's disease and a history of anxiety or depression were independent predictors for developing impulse control disorders.

CONCLUSIONS

7% of our Chinese PD subjects had impulse control disorders. When young Parkinson's disease patients with a history of anxiety or depression are treated with high dose of DA, they are at risk of developing impulse control disorders.

A random comparative study of terbinafine versus griseofulvin in patients with tinea capitis in Western China

OBJECTIVE

To compare the efficacy and safety of terbinafine with griseofulvin in the treatment of tinea capitis in Western China.

METHODS

Children (2-14 years of age) with clinically diagnosed and potassium hydroxide microscopy-confirmed tinea capitis were randomized into three groups: group GRI4 received 4 weeks of griseofulvin; group TBF2 received 2 weeks of terbinafine; and Group TBF4 received 4 weeks of terbinafine. Clinical and mycological evaluations were done in 0, 2, 4, and 8 weeks and 1 year after therapy started. The isolated pathogenic fungi were evaluated for in vitro susceptibility by detecting the minimal inhibitory concentration (MIC) against terbinafine, griseofulvin, itraconazole, and ketoconazole.

RESULTS

The clinical effectiveness rate of GRI4, TBF2, and TBF4 were 100% (95% CI-confidence interval: 82-100%), 96.3% (95% CI: 81-100%), and 100%(95% CI: 85-100%), respectively, at week 8 and 100% after 1 year for the 3 groups; clinical cure rates were 84.2%(95% CI: 77-99%), 85.2%(95% CI: 71-98%), and 78.3%(95% CI: 61-95%), respectively, at week 8 and 100% after 1 year for all agents; mycological cure rates were 100%(95% CI: 74-100%), 95.0%(95% CI: 74-100%), and 94.1%(95% CI: 50-93%) at week 8 and 100% after 1 year for the 3 groups. In vitro, all patient-derived cultures were sensitive to the four antifungal agents.

CONCLUSION

Data from the clinical trial and in vitro antifungal activity indicated that terbinafine is efficacious and well tolerated in the treatment for Trichophyton infections (T. violaceum; Arthroderma vanbreuseghemii; and T. tonsurans) of the scalp, i.e., a 2- to 4-week course of terbinafine is as effective as a 4-week course of griseofulvin; in fact, a 2-week course of terbinafine is sufficient. Terbinafine is an effective alternative to griseofulvin against tinea capitis of Trichophyton infections.

Structural and functional properties of human multidrug resistance protein 1 (MRP1/ABCC1)

Multidrug ABC transporters such as P-glycoprotein (P-gp/MDR1/ABCB1) and multidrug resistance protein 1 (MRP1/ABCC1) play an important role in the extrusion of drugs from the cell and their overexpression can be a cause of failure of anticancer and antimicrobial chemotherapy. Recently, the mouse P-gp/Abcb1a structure has been determined and this has significantly enhanced our understanding of the structure-activity relationship (SAR) of mammalian ABC transporters. This paper highlights our current knowledge on the structural and functional properties and the SAR of human MRP1/ABCC1. Although the crystal structure of MRP1/ABCC1 has yet to be resolved, the current topological model of MRP1/ABCC1 contains two transmembrane domains (TMD1 and TMD2) each followed by a nucleotide binding domain (NBD) plus a third NH2-terminal TMD0. MRP1/ABCC1 is expressed in the liver, kidney, intestine, brain and other tissues. MRP1/ABCC1 transports a structurally diverse array of important endogenous substances (e.g. leukotrienes and estrogen conjugates) and xenobiotics and their metabolites, including various conjugates, anticancer drugs, heavy metals, organic anions and lipids. Cells that highly express MRP1/ABCC1 confer resistance to a variety of natural product anticancer drugs such as vinca alkaloids (e.g. vincristine), anthracyclines (e.g. etoposide) and epipodophyllotoxins (e.g. doxorubicin and mitoxantrone). MRP1/ABCC1 is associated with tumor resistance which is often caused by an increased efflux and decreased intracellular accumulation of natural product anticancer drugs and other anticancer agents. However, most compounds that efficiently reverse P-gp/ABCB1-mediated multidrug resistance have only low affinity for MRP1/ABCC1 and there are only a few effective and relatively specific MRP1/ABCC1 inhibitors available. A number of site-directed mutagenesis studies, biophysical and photolabeling studies, SAR and QSAR, molecular docking and homology modeling studies have documented the role of multiple residues in determining the substrate specificity and inhibitor selectivity of MRP1/ABCC1. Most of these residues are located in the TMs of TMD1 and TMD2, in particular TMs 4, 6, 7, 8, 10, 11, 14, 16, and 17, or in close proximity to the membrane/cytosol interface of MRP1/ABCC1. The exact transporting mechanism of MRP1/ABCC1 is unclear. MRP1/ABCC1 and other multidrug transporters are front-line mediators of drug resistance in cancers and represent important therapeutic targets in future chemotherapy. The crystal structure of human MRP1/ABCC1 is expected to be resolved in the near future and this will provide an insight into the SAR of MRP1/ABCC1 and allow for rational design of anticancer drugs and potent and selective MRP1/ABCC1 inhibitors.

The small GTPase Cdc42 promotes membrane protrusion during polar body emission via ARP2-nucleated actin polymerization

Polar body emission is a specialized cell division throughout the animal kingdom, serving to reduce chromosome ploidy while preserving the egg cytoplasm. Critical to polar body emission are the asymmetric positioning of the meiotic spindle prior to anaphase, with one pole attached to the oocyte cortex, and the simultaneous membrane protrusion during subsequent cytokinesis. We have shown that, during Xenopus oocyte maturation, the small GTPase Cdc42 promotes membrane protrusion while a classical RhoA contractile ring forms and constricts at the base of the protrusion. We report here that treating oocytes with low concentrations of nocodazole diminished the size of metaphase I spindles and prevented polar body emission, and yet an active Cdc42 cap of correspondingly diminished size still developed, on time, atop of the spindle pole. Conversely, treating oocytes with low concentrations of taxol resulted in a spindle with multiple poles attached to the cortex, but still each of these poles were associated with activated cortical Cdc42 at the appropriate time. Therefore, the asymmetric positioning of the meiotic spindle with one pole anchored to the cortex is a prerequisite for Cdc42 activation. Furthermore, we demonstrated that the Cdc42-regulated F-actin nucleator ARP2/3 complex was similarly localized at the cortex of the protruding polar body membrane, suggesting that Cdc42 promotes membrane protrusion through an F-actin meshwork mechanism. Finally, we demonstrated that Cdc42 and RhoA formed similarly complementary activity zones during egg activation and that inhibition of Cdc42 prevented second polar body emission. Therefore, Cdc42 activation likely promotes membrane protrusion during polar body emission in widespread systems.

European ancestry and resting metabolic rate in older African Americans

BACKGROUND/OBJECTIVES

Resting metabolic rate (RMR) contributes 60-80% of total energy expenditure and is consistently lower in populations of African descent compared with populations of European populations. Determination of European ancestry (EA) through single nucleotide polymorphism (SNP) analysis would provide an initial step for identifying genetic associations that contribute to low RMR. We sought to evaluate the association between RMR and EA in African Americans.

SUBJECTS/METHODS

RMR was measured by indirect calorimetry in 141 African American men and women (aged 74.7±3.0 years) enrolled in a substudy of the Health, Aging and Body Composition Study. Ancestry informative markers were used to estimate individual percent EA. Multivariate regression was used to assess the association between RMR and EA after adjustments for soft tissue fat-free mass (STFFM), fat mass, age, study site, physical activity level and sex.

RESULTS

Mean EA was 23.8±16% (range: 0.1-70.7%) and there were no differences by sex. Following adjustments, each percent EA was associated with a 1.6 kcal/day (95% Confidence interval: 0.42, 2.7 kcal/day) higher RMR (P=0.008). This equates to a 160 kcal/day lower RMR in a population of completely African ancestry, with one of completely European ancestry. Additional adjustment for trunk STFFM that partially accounts for high-metabolic rate organs did not affect this association.

CONCLUSIONS

EA in African Americans is strongly associated with higher RMR. The data suggest that population differences in RMR may be due to genetic variants.