[Prognostic value of granular pattern of growth hormone secreting tumors]. / Caracterización de tumores secretores de hormona de crecimiento de acuerdo al patrón granular y su rol en el pronóstico.

BACKGROUND: Classification of growth hormone (GH) - secreting tumors by the granular pattern might predict their clinical behavior in acromegalic patients. There are several other prognostic factors. AIM: To compare the features at presentation and cure rates of patients with GH secreting tumors according to the granular pattern, and to define independent prognostic factors for surgical treatment in these patients. MATERIAL AND METHODS: A retrospective, observational study of 85 active acromegalic patients surgically treated in two medical centers. RESULTS: Seventy-four patients (87%) were classified as having densely granulated (DG) and 11 (13%) as sparsely granulated (SG) tumors. The latter were less active biochemically, had a higher rate of macroadenoma and cavernous sinus invasion and had a lower rate of biochemical cure than the DG group. Several characteristics were associated with disease persistence but only age (Odds ratio (OR) = 0.93) and cavernous sinus invasion (OR = 21.7) were independently associated in the logistic regression model. CONCLUSIONS: The sparsely granulated pattern is associated with a more aggressive behavior, but the main determinants of prognosis are age and cavernous sinus invasion.

[Hypophysitis and retroperitoneal fibrosis associated with autoimmune polyglandular syndrome and IgG4-related disease. Report of one case]. / Hipofisitis linfoplasmocitaria y fibrosis retroperitoneal asociadas a un síndrome poliglandular autoinmune. Enfermedades relacionadas con IgG4. Caso clínico.

We report a 23 year old woman presenting with a nephrotic syndrome due to minimal change disease, central diabetes insipidus, primary hypothyroidism, vitiligo and universal alopecia. Eleven years later, she presented secondary amenorrhea due to hypogonadotropic hypogonadism, with mild hyperprolactinemia and central adrenal insufficiency. A magnetic resonance imaging of the sella turcica showed a pituitary mass with suprasellar extension that was resected using a transsphenoidal approach. Pathology confirmed the presence of a lymphoplasmacytic hypophysitis. She needed a second surgical resection due to mass growth and neuro-ophthalmologic impairment. One year later, systemic lupus erythematosus, arterial hypertension and type 2 diabetes mellitus were diagnosed. Two years later, due to back pain, constipation and renal failure, retroperitoneal fibrosis was found, satisfactorily treated with glucocorticoids and colchicine. Hence, this clinical vignette shows the coexistence of autoimmune polyglandular syndrome with retroperitoneal fibrosis and lymphoplasmacytic hypophysitis. Tissue analysis showed the presence of IgG4 producing plasma cells in the pituitary and retroperitoneum, which constitute a basis for the diagnosis of IgG4 related disease.

[Granulosa cell ovarian tumor: precocious puberty in infant less than 1 year of age. Case report]. / Tumor de las células de granulosa: pubertad precoz en lactante menor de 1 año. Caso clínico.

INTRODUCTION: Juvenile granulosa cell tumors (JGCT) are very rare, especially in infants under the age of one. The most frequent presentation is with signs of precocious puberty. OBJECTIVE: Present an in fant with peripheral precocious puberty, diagnosis of JGCT and follow up. CLINICAL CASE: 10-month-old female infant with thelarche, pubic hair and palpable abdominal mass accompanied with eleva ted levels of estradiol, very low gonadotrophins and images that show a very large ovarian mass. A sapingooforectomy was carried out with full regression of symptoms and signs and improvement of laboratory exams. The biopsy showed TCGJ so inhibin B (InB) was taken as tumoral marker after surgery. This hormone was high initially, but rapidly declined. Follow-up was based on InB, antimu-llerian Hormone (AMH) and estradiol as described in this type of tumors. CONCLUSIONS: Juvenil gra nulosa cell tumors are very infrequent in pediatric age, but should be suspected in girl with peripheral precocious puberty. The majority of cases improve with surgery, but strict surveillance of tumoral markers is needed. The most specific markers are inhibin B and anti mullerian hormone (AMH), followed by estradiol levels.

Muscle magnetic resonance imaging and histopathology in ACTA1-related congenital nemaline myopathy.

INTRODUCTION: Muscle biopsy is usually diagnostic in nemaline myopathy (NM), but some patients may show nonspecific findings, leading to pitfalls in diagnosis. Muscle MRI is a helpful complementary tool. METHODS: We assessed the clinical, histopathological, MRI, and molecular findings in a 19-year-old patient with NM in whom 2 muscle biopsies with ultrastructural examination showed no nemaline bodies. We analyzed the degree and pattern of muscle MRI involvement of the entire body, including the tongue and pectoral muscles. RESULTS: Muscle MRI abnormalities in sartorius, adductor magnus, and anterior compartment muscles of the leg suggested NM. A previously unreported fatty infiltration of the tongue was found. A third biopsy after the muscle MRI showed scant nemaline bodies. A novel heterozygous de novo ACTA1 c.611C>T/p.Thr204Ile mutation was detected. CONCLUSIONS: We highlight the contribution of muscle imaging in addressing the genetic diagnosis of ACTA1-related NM.

[Mitochondrial DNA heteroplasmy of the m.3243A>G mutation in maternally inherited diabetes and deafness]. / Heteroplasmia de la mutación del ADN mitocondrial m.3243A>G en la diabetes y sordera de herencia materna.

Maternally Inherited Diabetes and Deafness (MIDD) is caused by mutations in mitochondrial DNA (mtDNA), mainly m.3243A>G. Severity, onset and clinical phenotype of MIDD patients are partially determined by the proportion of mutant mitochondrial DNA copies in each cell and tissue (heteroplasmy). The identification of MIDD allows a corred treatment with insulin avoiding drugs that may interfere with mitochondrial electrón chain transpon. We estimated the degree of heteroplasmy of the mutation m.3243A>G from blood, saliva, hair root and a muscle biopsy using quantitative PCR (qPCR) in a femóle adult patient. For this purpose, PCR producís were inserted in a vector creating plasmids with 3243A or G. Mutant and wild-type vectors were mixed in different proportions to créate a calibration curve used to interpólate heteroplasmy percentages with qPCR threshold cycles. The proportions of m.3243A>G heteroplasmy were 62% (muscle), 14% (saliva), 6% (blood leukocytes) and 3% in hair root. Quantitative analysis of heteroplasmy showed marked variations in different tissues (highest in muscle and lowest in blood). Given the relatively high heteroplasmy found in saliva, this type of biológical sample may represent an adequate non-invasive way for assessing the presence of m.3243A>G mutations in epidemiologic studies.

Abnormal distribution of inositol 1,4,5-trisphosphate receptors in human muscle can be related to altered calcium signals and gene expression in Duchenne dystrophy-derived cells.

Inositol 1,4,5-trisphosphate (IP(3)) receptors (IP(3)Rs) drive calcium signals involved in skeletal muscle excitation-transcription coupling and plasticity; IP(3)R subtype distribution and downstream events evoked by their activation have not been studied in human muscle nor has their possible alteration in Duchenne muscular dystrophy (DMD). We studied the expression and localization of IP(3)R subtypes in normal and DMD human muscle and in normal (RCMH) and dystrophic (RCDMD) human muscle cell lines. In normal muscle, both type 1 IP(3)Rs (IP(3)R1) and type 2 IP(3)Rs (IP(3)R2) show a higher expression in type II fibers, whereas type 3 IP(3)Rs (IP(3)R3) show uniform distribution. In DMD biopsies, all fibers display a homogeneous IP(3)R2 label, whereas 24 +/- 7% of type II fibers have lost the IP(3)R1 label. RCDMD cells show 5-fold overexpression of IP(3)R2 and down-regulation of IP(3)R3 compared with RCMH cells. A tetanic stimulus induces IP(3)-dependent slow Ca(2+) transients significantly larger and faster in RCDMD cells than in RCMH cells as well as significant ERK1/2 phosphorylation in normal but not in dystrophic cells. Excitation-driven gene expression was different among cell lines; 44 common genes were repressed in RCMH cells and expressed in RCDMD cells or vice versa. IP(3)-dependent Ca(2+) release may play a significant role in DMD pathophysiology.

[Virilization caused by an ovarian tumor. Report of one case]. / Hiperandrogenismo avanzado en una mujer postmenopáusica. Caso clínico.

We report a 76-year-old woman with a virilization syndrome characterized by progressive androgenic alopecia, clitoris enlargement and hirsutism predominating in the face. Plasma testosterone was 711 ng/dl. Magnetic resonance imaging showed slightly enlarged ovaries with a cyst in the left. A bilateral oophorectomy was performed, demonstrating the presence of a Leydig cell hilar tumor in the right ovary. The patient had a good postoperative evolution with reduction of androgen levels and reversion of alopecia.

Ectopic pituitary adenoma of the TSH-secreting sphenoidal sinus with excellent response to somatostatin analogs. Theory of the embryogenesis and literature review from a clinical case.

Ectopic thyrotropin-secreting pituitary adenomas are rare, with only 10 published cases. We report the case of a 52-year-old woman who was referred for primary hypothyroidism, who showed clinical signs of hyperthyroidism and had been under treatment with levothyroxine. Her exams revealed high levels of thyroid stimulating hormone (TSH), at odds with free thyroxin (FT4) and raised triiodothyronine (T3), which remained elevated after medication suspension, suggesting possible central hyperthyroidism. Sellar MRI showed normal pituitary gland, with a mass in the sphenoid sinus of 24 mm. A possible ectopic TSH secreting pituitary tumor of sphenoid sinus was hypothesized. After a intramuscularly (IM) single dose of a sustained-relase of a somatostatin analog (octreotide) 20 mg, plasma levels of thyroid hormones were normalized and a significant tumor reduction was demonstrated in MRI control at 7-weeks' follow-up. The tumor was removed by transsphenoidal endoscopy, and the biopsy confirmed an adenoma with positive immunostaining for TSH and GH. Hyperthyroidism recurrence was observed in hormonal controls 4 weeks after surgery. Treatment with sustained-release octreotide was reinitiated, every 60-days for two years, with normalization of the thyroid hormone profile, but with a residual lesion with the appearance of a tumor in the MRI. A second tumor resection was performed, achieving sustained hormonal cure and no residual tumor lesion at 2-years' follow-up. To our knowledge, this is the first report of an ectopic thyrotropin-secreting pituitary adenoma of the sphenoid sinus. Clinical and laboratory aspects relevant to this entity are reviewed, emphasizing the usefulness of octreotide in the management of the reported case.

Prevalence of EGFR Mutations and Clinico-Pathological Characteristics of Chilean Lung Cancer Patients

Background: Lung cancer (LC) is the second leading cause of cancer death in Chile, causing >3,000 deaths every year. Epidemiological LC data in Chile is scarce and scattered. Here, we aimed to quantify the prevalence of Epidermal Growth Factor Receptor (EGFR) gene mutations in a Chilean cancer center. These data may identify individuals that could benefit from targeted therapies such as Tyrosine Kinase Inhibitors (TKIs). Methods: A total of 1,405 Biopsies from 1,381 LC patients were retrospectively analyzed retrieving clinical data from EGFR mutants including age, gender, histological type, smoking habits and type of EGFR mutation. We also analyzed overall survival (OS) rates. Results: From all patients 21.7% had clinically relevant EGFR mutations, and a median age at diagnosis of 65 years. Most were female (64%), classified as adenocarcinomas (94.5%), and non-smokers/light smokers (93.1%). The most prevalent mutation was exon-19 deletions (50.6%) followed by Leucine-to Arginine 858; OS was 15 months. Clinical follow-up information was available for 83 patients. The use of TKIs in these patients significantly improved OS. Conclusion: The prevalence of EGFR mutations in the studied population was 21.7%, comparable to other countries in Latin America. The most frequent EGFR mutation was exon-19 deletion, OS in this group was 15 months, and TKIs significantly improved OS.

Selective loss of MEG3 expression and intergenic differentially methylated region hypermethylation in the MEG3/DLK1 locus in human clinically nonfunctioning pituitary adenomas.

CONTEXT: MEG3 is an imprinted gene encoding a novel noncoding RNA that suppresses tumor cell growth. Although highly expressed in the normal human pituitary, it is unknown which of the normal pituitary cell types and pituitary tumors express MEG3. OBJECTIVES: Our objectives were 1) to investigate cell-type- and tumor-type-specific expression of MEG3 in the human pituitary and 2) to investigate whether methylation in the intergenic differentially methylated region (IG-DMR) at the DLK1/MEG3 locus is involved in the loss of MEG3 expression in tumors. DESIGN AND METHODS: RT-PCR, quantitative RT-PCR, Northern blot, and a combination of in situ hybridization and immunofluorescence were used to determine the cell-type- and tumor-type-specific MEG3 expression. Bisulfite treatment and PCR sequencing of genomic DNA were used to measure the CpG methylation status in the normal and tumor tissues. Five normal human pituitaries and 17 clinically nonfunctioning, 11 GH-secreting, seven prolactin-secreting, and six ACTH-secreting pituitary adenomas were used. RESULTS: All normal human pituitary cell types express MEG3. However, loss of MEG3 expression occurs only in nonfunctioning pituitary adenomas of a gonadotroph origin. All other pituitary tumor phenotypes examined express MEG3. Hypermethylation of the IG-DMR at the DLK1/MEG3 locus is present in nonfunctioning pituitary adenomas. CONCLUSIONS: MEG3 is the first human gene identified expressed in multiple normal human pituitary cell types with loss of expression specifically restricted to clinically nonfunctioning pituitary adenomas. The IG-DMR hypermethylation may be an additional mechanism for MEG3 gene silencing in such tumors.

Role of Ki-67 proliferation index and p53 expression in predicting progression of pituitary adenomas.

Pituitary adenomas sometimes progress after surgery and can be locally invasive. Ki-67 and p53 expression are referred to as indicators of aggressive behavior in the World Health Organization Classification of Endocrine Tumors. The real value of these markers including an appropriate threshold for Ki-67 labeling index correlating with tumor progression is controversial. We identified 24 consecutive pituitary adenomas from patients who required surgery for recurrence within 5 years of their first procedure and 31 consecutive adenomas with no evidence of postsurgical progression within 5 years of first surgery. Case selection was based upon availability of complete clinical information, blocks, and slides for study. Immunohistochemistry for Ki-67 revealed that the tumors without progression had a proliferation index of 0.41% +/- 0.01% (mean +/- SEM) (n = 31) (range, 0.08%-1.2%) and the first biopsy from those tumors which progressed had a mean proliferation index of 1.45% +/- 0.09% (mean +/- SEM) (n = 24) (range, 0.1%-10.6%) (P = .01). With the use of ROC analysis, a threshold level of Ki-67 expression greater than 1.3% predicts progression with a high specificity. The group with progression had a higher proportion of nonfunctioning tumors (P < .005, chi(2)). There was no significant difference between the 2 groups with regard to invasion, suprasellar extension, size, tumor type, postoperative radiotherapy, extent of resection, sex, and age. Ki-67 labeling index was an independent predictor of progression (multivariate analysis, P < .011). p53 was positive in 12.5% of cases with surgical progression and in 9.6% of cases without progression, but the difference was not significant (P = .7; chi(2), 0.11).

The effects of SOM230 on cell proliferation and adrenocorticotropin secretion in human corticotroph pituitary adenomas.

CONTEXT: There is no tumor-directed medical therapy available for Cushing's disease. OBJECTIVE: The objective was to determine the in vitro effect of the somatostatin analog pasireotide (SOM230) on cell proliferation in human corticotroph tumors. DESIGN/METHODS: Expression of somatostatin receptors (SSTR 1-5) was determined by quantitative RT-PCR in 13 human corticotroph tumors and by immunohistochemistry (IHC) in 12 of the 13 tumors. SOM230 effects on cell proliferation and ACTH release were evaluated in vitro using primary cultures of six of the 13 human corticotroph adenomas. RESULTS: In our series, we found expression of SSTR subtypes 1, 2, 4, and 5 in human corticotroph tumors by quantitative RT-PCR. All receptor subtypes were detected by IHC, with SSTR subtype 5 having the highest IHC score in 83% (10 of 12) of the cases. Significant suppression of cell proliferation was observed in all tumors cultured (percent suppression range: 10-70%; P = 0.045-0.001). SOM230 inhibited ACTH secretion in five of the six tumors cultured (percent suppression range: 23-56%; P = 0.042-0.001). CONCLUSION: Corticotroph tumors express multiple SSTR subtypes. SOM230 significantly suppressed cell proliferation and ACTH secretion in primary cultures of human corticotroph tumors. These in vitro results support the hypothesis that SOM230 may have a role in the medical therapy of corticotroph tumors.

Caracterización de tumores secretores de hormona de crecimiento de acuerdo al patrón granular y su rol en el pronóstico / Prognostic value of granular pattern of growth hormone secreting tumors

Background: Classification of growth hormone (GH) - secreting tumors by the granular pattern might predict their clinical behavior in acromegalic patients. There are several other prognostic factors. Aim: To compare the features at presentation and cure rates of patients with GH secreting tumors according to the granular pattern, and to define independent prognostic factors for surgical treatment in these patients. Material and Methods: A retrospective, observational study of 85 active acromegalic patients surgically treated in two medical centers. Results: Seventy-four patients (87%) were classified as having densely granulated (DG) and 11 (13%) as sparsely granulated (SG) tumors. The latter were less active biochemically, had a higher rate of macroadenoma and cavernous sinus invasion and had a lower rate of biochemical cure than the DG group. Several characteristics were associated with disease persistence but only age (Odds ratio (OR) = 0.93) and cavernous sinus invasion (OR = 21.7) were independently associated in the logistic regression model. Conclusions: The sparsely granulated pattern is associated with a more aggressive behavior, but the main determinants of prognosis are age and cavernous sinus invasion.

Hipofisitis linfoplasmocitaria y fibrosis retroperitoneal asociadas a un síndrome poliglandular autoinmune: enfermedades relacionadas con IgG4. Caso clínico / Hypophysitis and retroperitoneal fibrosis associated with autoimmune polyglandular syndrome and IgG4-related disease: report of one case

We report a 23 year old woman presenting with a nephrotic syndrome due to minimal change disease, central diabetes insipidus, primary hypothyroidism, vitiligo and universal alopecia. Eleven years later, she presented secondary amenorrhea due to hypogonadotropic hypogonadism, with mild hyperprolactinemia and central adrenal insufficiency. A magnetic resonance imaging of the sella turcica showed a pituitary mass with suprasellar extension that was resected using a transsphenoidal approach. Pathology confirmed the presence of a lymphoplasmacytic hypophysitis. She needed a second surgical resection due to mass growth and neuro-ophthalmologic impairment. One year later, systemic lupus erythematosus, arterial hypertension and type 2 diabetes mellitus were diagnosed. Two years later, due to back pain, constipation and renal failure, retroperitoneal fibrosis was found, satisfactorily treated with glucocorticoids and colchicine. Hence, this clinical vignette shows the coexistence of autoimmune polyglandular syndrome with retroperitoneal fibrosis and lymphoplasmacytic hypophysitis. Tissue analysis showed the presence of IgG4 producing plasma cells in the pituitary and retroperitoneum, which constitute a basis for the diagnosis of IgG4 related disease.

Tumor de las células de granulosa: pubertad precoz en lactante menor de 1 año. Caso clínico / Granulosa cell ovarian tumor: precocious puberty in infant less than 1 year of age. Case report

Resumen Introducción: Los tumores de las células de la granulosa de tipo juvenil (TCGJ) son muy poco fre cuentes, especialmente en menores de 1 año. Los signos de pubertad precoz constituyen la presenta ción clínica más importante. Objetivo: Presentar una lactante con pubertad precoz periférica, con diagnóstico de TCGJ, discutiendo las claves de su tratamiento y seguimiento. Caso Clínico: Lactante de 10 meses que presentó telarquia, vello púbico y tumor abdominal palpable acompañado de niveles plasmáticos de Estradiol aumentados, gonadotrofinas muy bajas e imágenes que mostraban masa ovárica gigante. Se realizó salpingooforectomía, obteniéndose regresión absoluta de signos y síntomas. La biopsia demostró TCGJ por lo que se tomó inhibina B (InB) como marcador después de la cirugía. Esta hormona estaba alta inicialmente, pero descendió rápidamente. El seguimiento se basó en InB, Hormona antimulleriana (AMH) y estradiol como se describe en este tipo de tumores. Conclusiones: Los TCGJ son muy infrecuentes en pediatría; deben sospecharse en niñas con puber tad precoz periférica. El tratamiento quirúrgico en la gran mayoría es curativo, pero debe mantenerse un estricto control con marcadores tumorales, siendo los más específicos la InB y la AMH y en menor escala los niveles de Estradiol.

Abstract Introduction: Juvenile granulosa cell tumors (JGCT) are very rare, especially in infants under the age of one. The most frequent presentation is with signs of precocious puberty. Objective: Present an in fant with peripheral precocious puberty, diagnosis of JGCT and follow up. Clinical case: 10-month-old female infant with thelarche, pubic hair and palpable abdominal mass accompanied with eleva ted levels of estradiol, very low gonadotrophins and images that show a very large ovarian mass. A sapingooforectomy was carried out with full regression of symptoms and signs and improvement of laboratory exams. The biopsy showed TCGJ so inhibin B (InB) was taken as tumoral marker after surgery. This hormone was high initially, but rapidly declined. Follow-up was based on InB, antimu-llerian Hormone (AMH) and estradiol as described in this type of tumors. Conclusions: Juvenil gra nulosa cell tumors are very infrequent in pediatric age, but should be suspected in girl with peripheral precocious puberty. The majority of cases improve with surgery, but strict surveillance of tumoral markers is needed. The most specific markers are inhibin B and anti mullerian hormone (AMH), followed by estradiol levels.

Maternally expressed gene 3, an imprinted noncoding RNA gene, is associated with meningioma pathogenesis and progression.

Meningiomas are common tumors, representing 15% to 25% of all central nervous system tumors. NF2 gene inactivation on chromosome 22 has been shown as an early event in tumorigenesis; however, few factors underlying tumor growth and progression have been identified. The chromosomal abnormalities of 14q32 are often associated with meningioma pathogenesis and progression; therefore, it has been proposed that an as yet unidentified tumor suppressor is present at this locus. Maternally expressed gene 3 (MEG3) is an imprinted gene located at 14q32 which encodes a noncoding RNA with an antiproliferative function. We found that MEG3 mRNA is highly expressed in normal arachnoidal cells. However, MEG3 is not expressed in the majority of human meningiomas or the human meningioma cell lines IOMM-Lee and CH157-MN. There is a strong association between loss of MEG3 expression and tumor grade. Allelic loss at the MEG3 locus is also observed in meningiomas, with increasing prevalence in higher grade tumors. In addition, there is an increase in CpG methylation within the promoter and the imprinting control region of MEG3 gene in meningiomas. Functionally, MEG3 suppresses DNA synthesis in both IOMM-Lee and CH157-MN cells by approximately 60% in bromodeoxyuridine incorporation assays. Colony-forming efficiency assays show that MEG3 inhibits colony formation in CH157-MN cells by approximately 80%. Furthermore, MEG3 stimulates p53-mediated transactivation in these cell lines. Therefore, these data are consistent with the hypothesis that MEG3, which encodes a noncoding RNA, may be a tumor suppressor gene at chromosome 14q32 involved in meningioma progression via a novel mechanism.

Dysferlinopathy in Chile: evidence of two novel mutations in the first reported cases.

We describe two Chilean patients with dysferlinopathy, a 32-year-old man with Miyoshi's distal myopathy and a 29-year-old woman with a proximodistal phenotype. Absence of dysferlin in frozen muscle biopsy allowed diagnostic confirmation. In these two patients, two mutations not previously identified in other populations were found: a homozygous c.1948delC (p.Leu650TyrfsX6) was found in the male patient; the heterozygous mutation c.1276G>A (p.Gly426Arg) was found in the female patient in association with the previously reported c.2858dupT (p.Phe954ValfsX2). To our knowledge, this is the first time that mutations in DYSF are identified in native Chileans. Our findings suggest the possibility that mutations in the DYSF gene were present in the Native American population before colonization.

Heteroplasmia de la mutación del ADN mitocondrial m.3243A>G en la diabetes y sordera de herencia materna / Mitochondrial DNA heteroplasmy of the m.3243A>G mutation in maternally inherited diabetes and deafness

Maternally Inherited Diabetes and Deafness (MIDD) is caused by mutations in mitochondrial DNA (mtDNA), mainly m.3243A>G. Severity, onset and clinical phenotype of MIDD patients are partially determined by the proportion ofmutant mitochondrial DNA copies in each cell and tissue (heteroplasmy). The identification ofMIDD allows a corred treatment with insulin avoiding drugs that may interfere with mitochondrial electrón chain transpon. We estimated the degree of heteroplasmy ofthe mutation m.3243A>G from blood, saliva, hair root and a muscle biopsy using quantitative PCR (qPCR) in a femóle adult patient. For this purpose, PCR producís were inserted in a vector creatingplasmids with 3243A or G. Mutant and wild-type vectors were mixed in different proportions to créate a calibration curve used to interpólate heteroplasmy percentages with qPCR threshold cycles. The proportions of m.3243A>G heteroplasmy were 62% (muscle), 14% (saliva), 6% (blood leukocytes) and 3% in hair root. Quantitative analysis of heteroplasmy showed marked variations in different tissues (highest in muscle and lowest in blood). Given the relatively high heteroplasmy found in saliva, this type of biológical sample may represent an adequate non-invasive way for assessing the presence of m.3243A>G mutations in epidemiologic studies.

Activation of p53 by MEG3 non-coding RNA.

MEG3 is a maternally expressed imprinted gene suggested to function as a non-coding RNA. Our previous studies suggest that MEG3 has a function of tumor suppression. The tumor suppressor p53 plays a central role in tumor suppression and mediates the functions of many other tumor suppressors. Therefore, we hypothesized that MEG3 functions through activation of p53. We found that transfection of expression constructs for MEG3 and its isoforms results in a significant increase in p53 protein levels and dramatically stimulates p53-dependent transcription from a p53-responsive promoter. Using this as the functional assay, we demonstrated that the open reading frames encoded by MEG3 transcripts are not required for MEG3 function, and the folding of MEG3 RNA is critical to its function, supporting the concept that MEG3 functions as a non-coding RNA. We further found that MEG3 stimulates expression of the growth differentiation factor 15 (GDF15) by enhancing p53 binding to the GDF15 gene promoter. Interestingly, MEG3 does not stimulate p21(CIP1) expression, suggesting that MEG3 can regulate the specificity of p53 transcriptional activation. p53 degradation is mainly mediated by the mouse double minute 2 homolog (MDM2). We found that MDM2 levels were down-regulated in cells transfected with MEG3, suggesting that MDM2 suppression contributes at least in part to p53 accumulation induced by MEG3. Finally, we found that MEG3 is able to inhibit cell proliferation in the absence of p53. These data suggest that MEG3 non-coding RNA may function as a tumor suppressor, whose action is mediated by both p53-dependent and p53-independent pathways.