Roles of exosomes in metastatic colorectal cancer

Metastases remain a major cause of cancer morbidity and mortality. This is a multistep process that involves aberrant cell communication, leading to tumor cell dissemination from the primary tumor and colonization of distinct organs for secondary tumor formation. The mechanisms promoting this pathological process are not fully understood, although they may be of obvious therapeutic interest. Exosomes are small cell-secreted vesicles that contain a large variety of proteins, lipids, and nucleic acids with important signaling activities, and that represent an evolutionarily conserved mechanism for cell-to-cell communication. Not surprisingly, exosome activities have gained strong interest in cancer biology and might play essential roles in metastasis development. Here, we will describe recent findings on the role of exosomes in cancer metastasis formation, particularly in colorectal cancer (CRC). We will also discuss the potential therapeutic value of these vesicles in metastatic cancer.

SHEDding light on the role of Pragmin pseudo-kinases in cancer

The human kinome comprises more than 50 pseudo-kinases with unclear biological function due to the absence of apparent catalytic activity, and therefore, with presumably little interest for cancer drug discovery. However, it is now acknowledged that several of them, such as Pragmin family members, play roles as important as those of active kinases in human cancer. How these pseudo-kinases promote tumor formation is largely unknown. Recently, independent structural analyses of three Pragmin pseudo-kinases (Pragmin, SGK223, and SGK269/PEAK1) revealed a split helical dimerization (SHED)-based mechanism of action. Additional sequence-structure analysis identified C19orf35 as a new member of the Pragmin family. Based on the results of these molecular studies, we present a unified model on how Pragmin pseudo-kinases may regulate oncogenic signaling, and suggest potential therapeutic strategies to block their tumor activity.

Dimerization of the Pragmin Pseudo-Kinase Regulates Protein Tyrosine Phosphorylation

The pseudo-kinase and signaling protein Pragmin has been linked to cancer by regulating protein tyrosine phosphorylation via unknown mechanisms. Here we present the crystal structure of the Pragmin 906-1,368 amino acid C terminus, which encompasses its kinase domain. We show that Pragmin contains a classical protein-kinase fold devoid of catalytic activity, despite a conserved catalytic lysine (K997). By proteomics, we discovered that this pseudo-kinase uses the tyrosine kinase CSK to induce protein tyrosine phosphorylation in human cells. Interestingly, the protein-kinase domain is flanked by N- and C-terminal extensions forming an original dimerization domain that regulates Pragmin self-association and stimulates CSK activity. A1329E mutation in the C-terminal extension destabilizes Pragmin dimerization and reduces CSK activation. These results reveal a dimerization mechanism by which a pseudo-kinase can induce protein tyrosine phosphorylation. Further sequence-structure analysis identified an additional member (C19orf35) of the superfamily of dimeric Pragmin/SgK269/PEAK1 pseudo-kinases.

Chemotactic G protein-coupled receptors control cell migration by repressing autophagosome biogenesis

Chemotactic migration is a fundamental behavior of cells and its regulation is particularly relevant in physiological processes such as organogenesis and angiogenesis, as well as in pathological processes such as tumor metastasis. The majority of chemotactic stimuli activate cell surface receptors that belong to the G protein-coupled receptor (GPCR) superfamily. Although the autophagy machinery has been shown to play a role in cell migration, its mode of regulation by chemotactic GPCRs remains largely unexplored. We found that ligand-induced activation of 2 chemotactic GPCRs, the chemokine receptor CXCR4 and the urotensin 2 receptor UTS2R, triggers a marked reduction in the biogenesis of autophagosomes, in both HEK-293 and U87 glioblastoma cells. Chemotactic GPCRs exert their anti-autophagic effects through the activation of CAPNs, which prevent the formation of pre-autophagosomal vesicles from the plasma membrane. We further demonstrated that CXCR4- or UTS2R-induced inhibition of autophagy favors the formation of adhesion complexes to the extracellular matrix and is required for chemotactic migration. Altogether, our data reveal a new link between GPCR signaling and the autophagy machinery, and may help to envisage therapeutic strategies in pathological processes such as cancer cell invasion.

Signaling switch of the urotensin II vasosactive peptide GPCR: prototypic chemotaxic mechanism in glioma

Multiform glioblastomas (GBM) are the most frequent and aggressive primary brain tumors in adults. The poor prognosis is due to neo-angiogenesis and cellular invasion, processes that require complex chemotaxic mechanisms involving motility, migration and adhesion. Understanding these different cellular events implies identifying receptors and transduction pathways that lead to and promote either migration or adhesion. Here we establish that glioma express the vasoactive peptide urotensin II (UII) and its receptor UT and that UT-mediated signaling cascades are involved in glioma cell migration and adhesion. Components of the urotensinergic systems, UII and UT, are widely expressed in patient-derived GBM tissue sections, glioma cell lines and fresh biopsy explants. Interestingly, gradient concentrations of UII produced chemoattracting migratory/motility effects in glioma as well as HEK293 cells expressing human UT. These effects mainly involved the G13/Rho/rho kinase pathway while partially requiring Gi/o/PI3K components. In contrast, we observed that homogeneous concentrations of UII drastically blocked cell motility and stimulated cell-matrix adhesions through a UT/Gi/o signaling cascade, partially involving phosphatidylinositol-3 kinase. Finally, we provide evidence that, in glioma cells, homogeneous concentration of UII allowed translocation of Gα13 to the UT receptor at the plasma membrane and increased actin stress fibers, lamellipodia formation and vinculin-stained focal adhesions. UII also provoked a re-localization of UT precoupled to Gαi in filipodia and initiated integrin-stained focal points. Altogether, these findings suggest that UT behaves as a chemotaxic receptor, relaying a signaling switch between directional migration and cell adhesion under gradient or homogeneous concentrations, thereby redefining sequential mechanisms affecting tumor cells during glioma invasion. Taken together, our results allow us to propose a model in order to improve the design of compounds that demonstrate signaling bias for therapies that target specifically the Gi/o signaling pathway.

Impact of meriolins, a new class of cyclin-dependent kinase inhibitors, on malignant glioma proliferation and neo-angiogenesis

BACKGROUND

Glioblastomas are the most frequent and most aggressive primary brain tumors in adults. The median overall survival is limited to a few months despite surgery, radiotherapy, and chemotherapy. It is now clearly established that hyperactivity of cyclin-dependent kinases (CDKs) is one of the processes underlying hyperproliferation and tumoral growth. The marine natural products meridianins and variolins, characterized as CDK inhibitors, display a kinase-inhibitory activity associated with cytotoxic effects. In order to improve selectivity and efficiency of these CDK inhibitors, a series of hybrid compounds called meriolins have been synthesized.

METHODS

The potential antitumoral activity of meriolins was investigated in vitro on glioma cell lines (SW1088 and U87), native neural cells, and a human endothelial cell line (HUV-EC-C). The impact of intraperitoneal or intratumoral administrations of meriolin 15 was evaluated in vivo on 2 different nude mice-xenografted glioma models.

RESULTS

Meriolins 3, 5, and 15 exhibited antiproliferative properties with nanomolar IC50 and induced cell-cycle arrest and CDK inhibition associated with apoptotic events in human glioma cell lines. These meriolins blocked the proliferation rate of HUV-EC-C through cell cycle arrest and apoptosis. In vivo, meriolin 15 provoked a robust reduction in tumor volume in spite of toxicity for highest doses, associated with inhibition of cell division, activation of caspase 3, reduction of CD133 cells, and modifications of the vascular architecture.

CONCLUSION

Meriolins, and meriolin 15 in particular, exhibit antiproliferative and proapoptotic activities on both glioma and intratumoral endothelial cells, constituting key promising therapeutic lead compounds for the treatment of glioblastoma.

Down-regulation of GABA(A) receptor via promiscuity with the vasoactive peptide urotensin II receptor. Potential involvement in astrocyte plasticity

GABA_A receptor (GABA_AR) expression level is inversely correlated with the proliferation rate of astrocytes after stroke or during malignancy of astrocytoma, leading to the hypothesis that GABA_AR expression/activation may work as a cell proliferation repressor. A number of vasoactive peptides exhibit the potential to modulate astrocyte proliferation, and the question whether these mechanisms may imply alteration in GABA_AR-mediated functions and/or plasma membrane densities is open. The peptide urotensin II (UII) activates a G protein-coupled receptor named UT, and mediates potent vasoconstriction or vasodilation in mammalian vasculature. We have previously demonstrated that UII activates a PLC/PIPs/Ca²⁺ transduction pathway, via both G_q and G_i/o proteins and stimulates astrocyte proliferation in culture. It was also shown that UT/G_q/IP₃ coupling is regulated by the GABA_AR in rat cultured astrocytes. Here we report that UT and GABA_AR are co-expressed in cerebellar glial cells from rat brain slices, in human native astrocytes and in glioma cell line, and that UII inhibited the GABAergic activity in rat cultured astrocytes. In CHO cell line co-expressing human UT and combinations of GABA_AR subunits, UII markedly depressed the GABA current (β₃γ₂>α₂β₃γ₂>α₂β₁γ₂). This effect, characterized by a fast short-term inhibition followed by drastic and irreversible run-down, is not relayed by G proteins. The run-down partially involves Ca²⁺ and phosphorylation processes, requires dynamin, and results from GABA_AR internalization. Thus, activation of the vasoactive G protein-coupled receptor UT triggers functional inhibition and endocytosis of GABA_AR in CHO and human astrocytes, via its receptor C-terminus. This UII-induced disappearance of the repressor activity of GABA_AR, may play a key role in the initiation of astrocyte proliferation.

Phenotype-genotype correlations of 13 rare CYP21A2 mutations detected in 46 patients affected with 21-hydroxylase deficiency and in one carrier

CONTEXT

Steroid 21-hydroxylase deficiency is the most common enzymatic defect causing congenital adrenal hyperplasia with genotype/phenotype relationships for common mutations. Novel mutations of the CYP21A2 gene must be well studied to propose right genetic counseling for patients.

OBJECTIVE

Thirteen CYP21 mutations have been studied. A detailed description of phenotype was performed for all mutations (p.I77T, p.L167P, p.I230T, p.R233K, p.G291S, p.G292D, p.E320K, p.R341P, p.R354H, p.R369W, p.R408C, p.G424S, and p.R426H). In vitro and in silico studies were performed only for those not previously described (p.L167P, p.I230T, p.R233K, p.G292D, p.E320K, and p.R369W).

RESULTS

Regarding phenotype, patients with 10 of these mutations had a classical form. A patient with isolated p.I230T presented with nonclassical form and a patient with the association p.I230T + p.V281L in cis presented with a more severe phenotype. The p.R233K mutation was detected in a carrier partner. A patient with p.R369W presented with an intermediate form. Functional studies showed that all mutations except p.I230T and p.R369W decreased enzyme activity more than p.P30L: severity of p.R369W was intermediate between p.P30L and p.V281L, and finally p.I230T was less severe than p.V281L. Mutation analysis in a three-dimensional model structure of the CYP21 protein explained the observed in vitro effects, severe mutations being implicated in important functional domains of the protein.

CONCLUSION

According to phenotype and functional studies, 11 of the mutations described, except the isolated p.R369W and p.I230T, may be responsible for a severe phenotype underlying the necessity to manage children having them. The p.I230T is a nonclassical mutation, and for the p.R369W, we need more cases to precise its severity.

Bilateral anorchia in infancy: occurence of micropenis and the effect of testosterone treatment

OBJECTIVE

To analyze the clinical and histological findings in boys with bilateral anorchia and the response to testosterone treatment on penis length.

STUDY DESIGN

Patients were divided into two groups according to the absence (group A, n = 29) or the presence (group B, n = 26) of palpable intrascrotal or inguinal mass at first clinical examination.

RESULTS

A micropenis was found in 46% of patients (n = 24) with a similar proportion in both groups. Testosterone treatment induced a mean penis length gain of 1.9 +/- 1.3 SDS (standard deviation score). However, micropenis persisted in six patients. Histological examination (n = 18) confirmed the absence of any testicular structure with deferent ducts being present unilaterally or bilaterally in all but three patients. In these three patients, a hemorrhagic testis, probably as a result of a mechanical torsion, was found.

CONCLUSIONS

The presence of isolated micropenis in almost half of patients with bilateral anorchia strongly suggests that the testicular damage frequently occurs during the second half of gestation after male sexual differentiation. In most cases, testosterone treatment stimulates the penile growth. Although the pathogenesis of bilateral anorchia may be heterogeneous, our study suggests that gonads may have been functionally abnormal before they disappeared, and suggests that some patients have an intrinsic endocrine disorder.

A nationwide study of granulosa cell tumors in pre- and postpubertal girls: missed diagnosis of endocrine manifestations worsens prognosis

BACKGROUND

There are very few data on the natural history of ovarian granulosa cell tumors (OGCT) in children. The aim of this study was to determine whether early recognition and diagnosis of the initial endocrine signs could improve the outcome of these tumors.

METHODS

In a nationwide study from 1990 to 2004, we analyzed the clinical, biological and pathologic data from 40 pre- and postpubertal girls presenting an OGCT.

RESULTS

1. Among the prepubertal girls (n = 29), 17 OGCTs were diagnosed on the basis of precocious pseudopuberty. None of the 17 girls had a peritoneal spread of the tumor (100% FIGO stage Ia). Diagnosis based on a tumoral or acute abdomen (12 cases) was associated with frequent intraperitoneal ruptures of the tumor (50%) and a risk of relapse (2 cases). Of the eight girls who had had a misdiagnosed precocious pseudopuberty, five had a pre- or perioperative tumoral rupture. 2. Among the postpubertal girls (n = 11), endocrine manifestations such as secondary amenorrhea or virilization had been underevaluated in three of them and the diagnosis was established from a tumoral abdomen. This clinical presentation was associated with frequent ruptures of the mass in the peritoneum (80%) and a higher risk of recurrence (30%). 3. A delayed diagnosis of OGCT despite previous endocrine signs (11 cases; 8 pre- and 3 postpubertal) was associated with a high risk of pre- or peri-operative peritoneal tumor spreading (70% FIGO stage Ic or IIc, p <0.05). The mean delay for diagnosis ranged from 3 to 11 months.

CONCLUSION

This study highlights the critical role of early diagnosis of OGCT in pre- and postpubertal girls, particularly at the first seemingly banal signs of endocrine disorder. Peritoneal spread of the tumor may thereby be prevented, which improves the prognosis.

Le rachitisme symptomatique de l’adolescent

Although systematic vitamin D supplementation in adolescents remains debated, rickets is nevertheless a well recognized pathology in this age group. Adolescence is an at-risk period because of rapid growth, insufficient calcium intake and/or vitamin D status. Surveys have shown that calcium intake is insufficient (< 1000 mg a day) in 45% of boys and 71% of girls and that vitamin D status is deficient (25-OH-D < 10 ng/ml). The aims of the study carried out by the Calcium Group of the Société Française de Pédiatrie, were to evaluate the frequency of rickets, and to define the criteria for the adolescent population at risk. Forty-one adolescents with rickets were hospitalized between 1985 and 2000. Most of the cases were from the Northern France: 20 from Paris and suburbs, eight from the North-West, four from the North, four from the North-East; five were from the Center of France. The mean age was 13 years and two months for the 28 girls, and 14 years and four months for the 13 boys. Eighty per cent of the adolescents were from immigrant families (33/41): 15 were from sub-Saharan Africa, ten from North Africa, six from Pakistan and two from Turkey. Two thirds of the adolescents were hospitalized in the 2nd quarter of the year. Some adolescents suffered from lower limb pain, 16 had deformations of lower limbs, particularly genu valgum, associated with pain; seven others had either muscle spasms (4), tetany (3). Serum calcium level was low (average 1.84 mmol/l: [1.1-2.5]), and serum 25-OH D level was extremely low. Radiographic characteristics observed were metaphyseal strips on the knees, with condensed edges at times, with the presence of bone demineralization. The treatment combined calcium and vitamin D, and was often administered intravenously when a hypocalcemia was detected. Rickets is not frequent in adolescents, but nonetheless this pathology is not exceptional, and the number of cases is probably under-estimated. Rickets affects immigrant adolescents in particular but nevertheless could also present a certain risk period for the general population.

IMAGe, a new clinical association of intrauterine growth retardation, metaphyseal dysplasia, adrenal hypoplasia congenita, and genital anomalies

We report three boys with adrenal hypoplasia congenita (AHC) and additional findings that represent a new syndrome, IMAGe: Intrauterine growth retardation, Metaphyseal dysplasia, AHC, and Genital anomalies. Each presented shortly after birth with growth retardation and severe adrenal insufficiency. Each of the three patients had mild dysmorphic features, bilateral cryptorchidism, a small penis, and hypogonadotropic hypogonadism. Skeletal surveys revealed metaphyseal dysplasia in all three and epiphyseal dysplasia in two. The patients had documented or suspected hypercalciuria and/or hypercalcemia, resulting in nephrocalcinosis in one and in prenatal liver and spleen calcifications in another. AHC presents most often either as an isolated abnormality, caused by mutations in the DAX1 gene, or as part of an Xp21 contiguous gene syndrome, caused by a deletion of the Duchenne muscular dystrophy, glycerol kinase, and DAX1 genes. All three patients with the IMAGe association had normal creatine kinase levels and no evidence of glycerol kinase deficiency. Sequence analysis of DNA from these patients revealed no mutation in the DAX1- or steroidogenic factor-1-coding sequences, nor was a deletion of DAX1 detected. Identification of the molecular basis of the IMAGe association will give new insight into the pathogenesis of this syndromic relationship involving bone, adrenal cortical, and pituitary development.

Evaluation of gonadal function in 107 intersex patients by means of serum antimüllerian hormone measurement

Fetal male sexual differentiation is driven by two testicular hormones: testosterone (synthesized by interstitial Leydig cells) and antimüllerian hormone (AMH; produced by Sertoli cells present in the seminiferous tubules). Intersex states result either from gonadal dysgenesis, in which both Leydig and Sertoli cell populations are affected, or from impaired secretion or action of either testosterone or AMH. Until now, only Leydig cell function has been assessed in children with ambiguous genitalia, by means of testosterone assay. To determine whether serum AMH would help in the diagnosis of intersex conditions, we assayed serum AMH levels in 107 patients with ambiguous genitalia of various etiologies. In XY patients, AMH was low when the intersex condition was caused by abnormal testicular determination (including pure and partial gonadal dysgenesis) but was normal or elevated in patients with impaired testosterone secretion, whereas serum testosterone was low in both groups. AMH was also elevated during the first year of life and at puberty in intersex states caused by androgen insensitivity. In 46,XX patients with a normal male phenotype or ambiguous genitalia, in whom the diagnosis of female pseudohermaphroditism had been excluded, serum AMH levels higher than 75 pmol/L were indicative of the presence of testicular tissue and correlated with the mass of functional testicular parenchyma. In conclusion, serum AMH determination is a powerful tool to assess Sertoli cell function in children with intersex states, and it helps to distinguish between defects of male sexual differentiation caused by abnormal testicular determination and those resulting from isolated impairment of testosterone secretion or action.

[Psychosocial and sexual outcome in women with Turner syndrome]

Results of an inquiry in adults patients (18-53 years of age) coming from three centers (1 in Rouen & 2 in Paris), 213 questionnaires were sent. 105 answers were received. Scholar achievement: only secondary cycle in 6%, Secondary cycle + professional course in 22% and tertiary cycle in 44%. No scholar ship in 2%, 26% were still ongoing studies. Professions: 18% are unemployed (24%), Secretary jobs: 10%, Health professions (altogether): 18%, Teachers: 8%, Clerks: 7%, Executive jobs: 8% and Miscellaneous jobs: 5%. 3% have an handicapped status. The small height was a career obstacle in 29%. Affective life. Age of first sexual intercourse was 19-22 years. 17 are or were married and 15% are living in couple. But 58% have not any sexual life whatsoever. These women are divided on the ways to cure the sterility. Few among the oldest have attempted adoption or medically assisted procreation, with each time low rate of success. 26% have psychological disturbances which were serious in 6% mainly due to depression.

[Parasitemia in Plasmodium falciparum malarial attacks in children]

In order to evaluate the predictive value of parasitaemia, this parameter was measured on admission in 69 Gabonese children aged from 3 to 13 years hospitalized for Plasmodium falciparum malarial attacks. Fourteen of these children had cerebral malaria, 5 had isolated convulsions and 50 had uncomplicated attacks. The parasitaemia values measured were compared with those found in asymptomatic children of the same age range carrying trophozoites. There were no significant differences in mean parasitaemia count between the 3 types of malarial attack, and only the asymptomatic carriers had significantly lower counts. However, the wide scattering of individual values within each group indicated that simple measurement of parasitaemia is not discriminative enough to predict the course of malarial attacks in children living in endemic regions. In particular, malarial attacks with very low or very high parasitaemia value are possible, but similar values are found in asymptomatic carriers.

[Problems in diagnosis of necrotic angiitis of the tongue]

Cutaneous and mucous lesions are uncommon and very often confusing in Horton's disease. In this case report, adding to this confusing aspect, the patient's medical history and clinical signs led the investigations in a totally different direction. Facing this isolated lesion of the tongue and the negative biopsy of the temporal superficial artery, the diagnosis of Horton's disease was finally confirmed by the good reaction following corticoid therapy.

[Value of x-ray computed tomography in topographic exploration of an impacted maxillary third molar]

A case report of impacted maxillary third molar illustrate the limits of panoramic radiograph in topographic approach of Higmore Antrum. The CT scan in duplicate incidence appears in this case like indispensable complement to the standard X-Ray. It accurates the impacted localisation and the proceeding in the surgical treatment.

Controlled trial of the action of a toothpaste containing nicomethanol hydrofluoride in the treatment of dentine hypersensitivity

A double-blind clinical trial was performed on 76 patients with dentine hypersensitivity. For four weeks the patients used either a toothpaste containing nicomethanol hydrofluoride or one containing potassium nitrate and sodium monofluorophosphate. After one, two and four weeks the pain responses of the teeth to three types of stimuli were assessed. In normal conditions of oral hygiene, the nicomethanol hydrofluoride toothpaste was found at least as effective as the potassium nitrate/sodium monofluorophosphate preparation.

[Acute necrosis of the thoracic esophagus and ileum complicating rheumatoid purpura]

A child is described who developed acute ischaemic necrosis of the oesophagus complicating an otherwise typical case of anaphylactoid purpura. This episode was preceded by a necrotising ileitis requiring intestinal resection and ileostomy. The histological similarities of the lesions in the oesophagus and the ileum suggest a common cause connected with the anaphylactoid purpura.

[Hypophyseal gonadotropin secretion in sexual precocity with McCune-Albright's syndrome]

In three young girls with isosexual precocity and fibrous dysplasia of bones, plasma gonadotropins (LH and FSH) response to releasing hormone (LH-RH) has been much under the mean response in true female precocious puberty. These data and those previously reported in the literature suggest that MacCune-Albright's syndrome correlates to an hypothalamo-pituitary dysfunction rather than to a true prematurity.