The phosphatase Shp1 interacts with and dephosphorylates cortactin to inhibit invadopodia function

BACKGROUND

Invadopodia are actin-based cell-membrane protrusions associated with the extracellular matrix degradation accompanying cancer invasion. The elucidation of the molecular mechanisms leading to invadopodia formation and activity is central for the prevention of tumor spreading and growth. Protein tyrosine kinases such as Src are known to regulate invadopodia assembly, little is however known on the role of protein tyrosine phosphatases in this process. Among these enzymes, we have selected the tyrosine phosphatase Shp1 to investigate its potential role in invadopodia assembly, due to its involvement in cancer development.

METHODS

Co-immunoprecipitation and immunofluorescence studies were employed to identify novel substrate/s of Shp1AQ controlling invadopodia activity. The phosphorylation level of cortactin, the Shp1 substrate identified in this study, was assessed by immunoprecipitation, in vitro phosphatase and western blot assays. Short interference RNA and a catalytically-dead mutant of Shp1 expressed in A375MM melanoma cells were used to evaluate the role of the specific Shp1-mediated dephosphorylation of cortactin. The anti-invasive proprieties of glycerophosphoinositol, that directly binds and regulates Shp1, were investigated by extracellular matrix degradation assays and in vivo mouse model of metastasis.

RESULTS

The data show that Shp1 was recruited to invadopodia and promoted the dephosphorylation of cortactin at tyrosine 421, leading to an attenuated capacity of melanoma cancer cells to degrade the extracellular matrix. Controls included the use of short interference RNA and catalytically-dead mutant that prevented the dephosphorylation of cortactin and hence the decrease the extracellular matrix degradation by melanoma cells. In addition, the phosphoinositide metabolite glycerophosphoinositol facilitated the localization of Shp1 at invadopodia hence promoting cortactin dephosphorylation. This impaired invadopodia function and tumor dissemination both in vitro and in an in vivo model of melanomas.

CONCLUSION

The main finding here reported is that cortactin is a specific substrate of the tyrosine phosphatase Shp1 and that its phosphorylation/dephosphorylation affects invadopodia formation and, as a consequence, the ability of melanoma cells to invade the extracellular matrix. Shp1 can thus be considered as a regulator of melanoma cell invasiveness and a potential target for antimetastatic drugs. Video abstract.

Case Report: Early Treatment With Chenodeoxycholic Acid in Cerebrotendinous Xanthomatosis Presenting as Neonatal Cholestasis

Background: Cerebrotendinous xanthomatosis (CTX) is an inborn disorder of bile acid synthesis which causes progressive accumulation of toxic metabolites in various organs, particularly in brain and tendons. Most cases are diagnosed and treated in the second or third decade of life, when neurological involvement appears. We describe a case of CTX presenting as neonatal cholestasis. Results: The child presented cholestasis at 2 months of life. In the following months jaundice slowly disappeared, with a normalization of bilirubin and aminotransferases, respectively, at 6 and 8 months. A LC-Mass Spectrometry of the urines showed the presence of cholestanepentols glucuronide, which led to the suspicion of cerebrotendinous xanthomatosis. The diagnosis was confirmed by the dosage of cholestanol in serum and the molecular genetic analysis of the CYP27A1 gene. Therapy with chenodeoxycholic acid (CDCA) was started at 8 months and is still ongoing. The child was monitored for 13 years by dosage of serum cholestanol and urinary cholestanepentols. A strictly biochemical and neurological follow up was performed and no sign of neurological impairment was observed. Conclusions: Prompt diagnosis and treatment of CTX presenting as neonatal cholestasis may prevent further neurological impairment.

Pediatric autoimmune liver disease and extra-hepatic immune-mediated comorbidities

BACKGROUND

Autoimmune liver disease (AILD) includes autoimmune hepatitis (AIH) and autoimmune sclerosing cholangitis (ASC). AILD is often associated with other extra-hepatic immune-mediated disorders (EDs), but there are few pediatric studies available to date. In this study we evaluated the association between AILD and EDs in our pediatric series.

METHODS

In this single centre retrospective study 48 patients (39 AIH and 9 ASC children) were evaluated. Thirty-six children were primarily referred to our Centre for liver disease suspicion, while the remaining twelve had a previous diagnosis of EDs. All the patients were screened for various EDs at AILD diagnosis and yearly during the follow-up.

RESULTS

Mean duration of follow-up was 9 years and 1 month. Twenty-two (46%) patients had a diagnosis of EDs. Ulcerative colitis (UC) was the most frequent EDs (9 patients), followed by autoimmune thyroid disease (5 patients) and celiac disease (5 patients). In 7 out of 9 UC patients, ASC was present.

CONCLUSIONS

Our study showed a high association (46%) between AILD and EDs. In particular, in 8 out of 9 ASC patients UC was diagnosed (p-value 0.007). It is important to look for EDs in AILD children and, conversely, AILD in EDs children with abnormal liver function tests.

Diagnostic Value of Carcinoembryonic Antigen (CEA) Assay in Pleural Effusions

Carcinoembryonic antigen (CEA) levels were evaluated by a direct radioimmunoassay in the effusion fluids and plasma samples from 107 patients with pleural effusions of unknown etiology. CEA levels higher than 20 ng/ml were detected in 55 % of pleural effusions from patients with malignant disease: 40 % of the patients in this group had values of plasmatic CEA lower than 20 ng/ml. With the only exception of 4 patients with empyema, CEA levels were uniformly lower than 20 ng/ml in the effusion fluid of patients with benign disease. Moreover, CEA levels higher than 20 ng/ml were observed in 81.2 % of pleural effusions and 31.2 % of plasma samples from patients with cytology positive for malignancy, whereas increased CEA levels were observed in 37.5 % of effusion fluids and 33.3 % of plasma samples from patients with malignant disease but negative cytology in the pleural effusion. CEA assay in the effusion fluid represents a useful tool of high specificity and good sensitivity to discriminate between benign and malignant etiology of pleural effusions.

Encounter dynamics of a small target by a polymer diffusing in a confined domain

We study the first passage time for a polymer, that we call the narrow encounter time (NETP), to reach a small target located on the surface of a microdomain. The polymer is modeled as a freely joint chain (beads connected by springs with a resting non zero length) and we use Brownian simulations to study two cases: when (i) any of the monomer or (ii) only one can be absorbed at the target window. Interestingly, we find that in the first case, the NETP is an increasing function of the polymer length until a critical length, after which it decreases. Moreover, in the long polymer regime, we identified an exponential scaling law for the NETP as a function of the polymer length. In the second case, the position of the absorbed monomer along the polymer chain strongly influences the NETP. Our analysis can be applied to estimate the mean first time of a DNA fragment to a small target in the chromatin structure or for mRNA to find a small target.

[Nephrotic syndrome after treatment with d-penicillamine in a pediatric patient with Wilson's disease]

We describe a case of nephrotic syndrome (NS) after a 7 months treatment with D-penicillamine in a 14 years old girl with Wilson's disease, with a prompt regression at the discontinuation of the drug. Kidney function, proteinuria in particular, must be always monitored during the chelating therapy, and the drug must be discontinued as soon as signs of renal injury are detected.

[Pediatric steatohepatitis: is it only obesity?]

We describe the case of an 11-year-old obese child with nonalcoholic steatohepatitis and Wilson's disease. Nonalcoholic steatohepatitis, although frequently found in patients with obesity, can also be caused by other etiologies, including Wilson's disease, which must therefore always be ruled out in the obese child.

[Acute hepatitis as a side effect of albendazole: a pediatric case]

We describe a case of acute hepatitis with jaundice in a patient of seven years of age in oral treatment with albendazole; a mild increase of liver function tests is a well-known side effect after prolonged administration but acute hepatitis has never been described in childhood.

[Acute hepatitis as a side effect of albendazole: a pediatric case]

We describe a case of acute hepatitis with jaundice in a patient of seven years of age in oral treatment with albendazole; a mild increase of liver function tests is a well-known side effect after prolonged administration but acute hepatitis has never been described in childhood.

[Acute acalculous cholecystitis as a complication of hepatitis A: report of 2 pediatric cases]

Acute acalculous cholecystitis (CAA) is very rare in children and it is usually related to infectious agents. We report 2 paediatric cases of CAA complicating hepatitis type A, with a favourable evolution with conservative treatment.

[Hepatitis type A with atypical course]

Hepatitis A virus infection is usually asymptomatic in children. Classic symptomatic forms and atypical clinical manifestations are known. We report a paediatric case of hepatitis A with marked cholestasis, treated with steroids, and with an unusual prolonged course.

Conformal invariance and stochastic Loewner evolution processes in two-dimensional Ising spin glasses

We present numerical evidence that the techniques of conformal field theory might be applicable to two-dimensional Ising spin glasses with Gaussian bond distributions. It is shown that certain domain wall distributions in one geometry can be related to that in a second geometry by a conformal transformation. We also present direct evidence that the domain walls are stochastic Loewner (SLE) processes with kappa approximately 2.1. An argument is given that their fractal dimension d(f) is related to their interface energy exponent theta by d(f) - 1 = 3/[4(3 + theta)], which is consistent with the commonly quoted values d(f) approximately 1.27 and theta approximately -0.28.

Scalings of domain wall energies in two dimensional Ising spin glasses

We study domain wall energies of two dimensional spin glasses. The scaling of these energies depends on the model's distribution of quenched random couplings, falling into three different classes. The first class is associated with the exponent theta approximately -0.28; the other two classes have theta=0, as can be justified theoretically. In contrast to previous claims, we find that theta=0 does not indicate d=d(c)(l) but rather d< or =d(c)(l), where d(c)(l) is the lower critical dimension.

Relationship between plasma and hepatic cytosolic levels of ornithine decarboxylase (ODC) and thymidine kinase (TK) in 70% hepatectomized rats

Ornithine decarboxylase (ODC) and thymidine kinase (TK) are enzymes important for DNA synthesis, a process that is critical for cell renewal and regeneration. As such, they already have been used as surrogate markers of regeneration in tissue. In the present study, the activity of these two enzymes in plasma of rats and regenerating hepatic tissue following a 70% hepatectomy were determined. The results demonstrate that the changes in these enzyme activities in plasma reflect the changes obtained in the liver tissue. Thus, blood levels of ODC and TK can be used as a less invasive and nondestructive means of monitoring the regenerative response of the liver and possibly other tissues.

Circadian rhythm of hepatic cytosolic and nuclear estrogen and androgen receptors

Mammalian liver is a sex steroid-responsive tissue. The effects of these hormones presumably are mediated by hepatic estrogen receptors (ER) and androgen receptors (AR). Serum levels of sex hormones display circadian rhythms. Further, estrogens and androgens are commonly administered; administration of these agents is associated frequently with liver disease. Therefore, we investigated whether the cytosolic and nuclear sex steroid receptors also display a similar circadian rhythm, and whether variations occurred in the distribution of receptors between cytosolic and nuclear compartments. Animals were killed every 4 h from midnight till the following midnight; cytosolic and nuclear levels of both ER and AR were measured. Cytosolic ER reached a maximum level at 4 AM, and a minimum at 8 PM and midnight of both days. Nuclear ER was highest at 8 AM and lowest at 4 PM and 8 PM, a pattern which parallels variations in serum estradiol levels. Cytosolic AR was highest at 8 PM and lowest at midnight and 4 AM. Nuclear AR was highest at 4 AM and lowest at 4 PM and 8 PM. The highest level of nuclear AR does not correspond to the maximum serum testosterone level, which occurred at 4 PM. The total hepatic content of both ER and AR was not constant over the 24-h period, but varied considerably with time of day. These studies suggest that both ER and AR show a distinct circadian rhythm in subcellular compartmentalization, and that total hepatic content of ER and AR varies significantly during a 24-h period.