Determinación de mutaciones en los genes de los receptoresTirosina cinasa (kit y pdgfra) asociados a tumores del estroma Gastrointestinal (gist)

Las alteraciones moleculares en los oncogenes c-kit y pdgfra; que codifican para los receptores de membrana tirosina cinasas, se asocian con características clínico-patológicas de pacientes con tumores del estroma gastrointestinal (GIST). Actualmente, los medicamentos están siendo desarrollados para inhibir, a nivel, molecular, la acción de los oncogenes que desencadenan el desarrollo del cáncer. En este estudio caracterizamos las mutaciones de los genes c-kit y pdgfra en pacientes con diagnóstico de GIST para determinar las mutaciones que pudieran estar asociadas a la proliferación tumoral y/o a una respuesta terapéutica específica. Se aisló el ADN de 44 tejidos de tumor fijados en formalina con diagnóstico de GIST. Los exones con mayor frecuencia de mutaciones reportadas para los genes c-kit, y pdgfrc4 fueron amplificados y evaluados por secuenciación directa. Experimentos de donación fueron realizados para caracterizar todos los posibles aletos mutantes presentes en las células tumorales. Las secuencias de aminoácidos fueron inferidas y alineadas a una secuencia de referencia del Genebank para determinar el sitio y el tipo de mutación. Encontramos la mayor frecuencia de mutaciones en el exón 11 (77%) del gen c-kit. Las mutaciones encontradas en el exón 11 fueron heterogéneas mientras que, el exón 9 presentó un único tipo de mutación (p.A502Y503dup). En el gen pdgfra se observó sustituciones y deleciones, siendo la más frecuente p.D842V. Todas las mutaciones encontradas han sido previamente asociadas a GIST, inclusive se observaron mutaciones asociadas a. GIST con síndromes familiares. Un 66% de los pacientes de alto riesgo presentaron mutaciones entre los residuos 556-560 del exón 11 del gen c-kit. Es interesante observar que las mutaciones entre los residuos 556-560 comprenden la región de la yuxtamembrana que regula entre la conformación activa e inactiva del receptor. Nuestros resultados sugieren que el sitio y tipo de mutación activan constitutivamente a los receptores KIT y PDGFRc PDGFRc. Estudios clínicos han determinado cómo el tipo y sitio de mutación en estos genes, influyen en la respuesta objetiva y la resistencia a las drogas que actualmente se emplean. Una evaluación a nivel molecular de los casos con GIST permite una mejor interpretación del pronóstico y evolución clínica del proceso tumoral al determinar las mutaciones que desencadena una inadecuada señalización intracelular y por ende un descontrol del ciclo celular

Spatiotemporal Dynamics of Dissemination of Non-Pandemic HIV-1 Subtype B Clades in the Caribbean Region

The Human immunodeficiency virus type-1 (HIV-1) epidemic in the Caribbean region is mostly driven by subtype B; but information about the pattern of viral spread in this geographic region is scarce and different studies point to quite divergent models of viral dissemination. In this study, we reconstructed the spatiotemporal and population dynamics of the HIV-1 subtype B epidemic in the Caribbean. A total of 1,806 HIV-1 subtype B pol sequences collected from 17 different Caribbean islands between 1996 and 2011 were analyzed together with sequences from the United States (n = 525) and France (n = 340) included as control. Maximum Likelihood phylogenetic analyses revealed that HIV-1 subtype B infections in the Caribbean are driven by dissemination of the pandemic clade (BPANDEMIC) responsible for most subtype B infections across the world, and older non-pandemic lineages (BCAR) characteristics of the Caribbean region. The non-pandemic BCAR strains account for >40% of HIV-1 infections in most Caribbean islands; with exception of Cuba and Puerto Rico. Bayesian phylogeographic analyses indicate that BCAR strains probably arose in the island of Hispaniola (Haiti/Dominican Republic) around the middle 1960s and were later disseminated to Trinidad and Tobago and to Jamaica between the late 1960s and the early 1970s. In the following years, the BCAR strains were also disseminated from Hispaniola and Trinidad and Tobago to other Lesser Antilles islands at multiple times. The BCAR clades circulating in Hispaniola, Jamaica and Trinidad and Tobago appear to have experienced an initial phase of exponential growth, with mean estimated growth rates of 0.35-0.45 year(-1), followed by a more recent stabilization since the middle 1990s. These results demonstrate that non-pandemic subtype B lineages have been widely disseminated through the Caribbean since the late 1960s and account for an important fraction of current HIV-1 infections in the region

Best fit demographic model for different HIV-1 subtype B_CAR clades.

<p>Log marginal likelihood (ML) estimates for the logistic (Log), exponential (Expo) and expansion (Expa) growth demographic models obtained using the path sampling (PS) and stepping-stone sampling (SS) methods. The Log Bayes factor (BF) is the difference of the Log ML between of alternative (H1) and null (H0) models (H1/H0). Log BF >3 indicate that model H1 is more strongly supported by the data than model H0.</p

ML phylogenetic tree.

<p>A) HIV-1 subtype B <i>pol</i> PR/RT sequences (∼1,000 nt) circulating in the Caribbean (<i>n</i> = 743), US (<i>n</i> = 525), and France (<i>n</i> = 340); B) HIV-1 subtype B <i>pol</i> RT (∼600 nt) sequences from Barbados (<i>n</i> = 14), Guadeloupe (<i>n</i> = 243), Haiti (<i>n</i> = 15), Martinique (<i>n</i> = 452), Puerto Rico (<i>n</i> = 285), US Virgin Islands (<i>n</i> = 54) and representative sequences of the B_PANDEMIC (US = 165, France = 135) and the B_CAR (Caribbean = 200) clades. Branches are colored according to the geographic origin of each sequence as indicated at the legend (bottom right). Arcs indicate the B_PANDEMIC and B_CAR clades. Purple and green shaded boxes highlight the position of the Caribbean clades B_CAR-TT and B_CAR-JM. The <i>a</i>LRT support values are indicated at key nodes: *(0.81–0.90), **(0.91–1). Trees were rooted using HIV-1 subtype D reference sequences. The branch lengths are drawn to scale with the bar at the bottom indicating nucleotide substitutions per site.</p

Root location of the HIV-1 subtype B.

<p>Graphics depict the location state posterior probability distributions at the root of the subtype B_CAR clades at the Bayesian MCC trees obtained from complete dataset (A) and country “balanced” sub-sets (B to G) from the Caribbean region. Color code is indicated at the legend at bottom left.</p

High Diversity of Hepatitis B Virus Genotypes in Panamanian Blood Donors: A Molecular Analysis of New Variants

<div><p>Hepatitis B Virus (HBV) is an infectious agent that causes more than half of the cases of liver disease and cancer in the world. Globally there are around 250 million people chronically infected with this virus. Despite 16% of the cases of liver disease in Central America are caused by HBV, the information regarding its genetic diversity, genotypes and circulation is scarce. The purpose of this study was to evaluate the genetic variability of the HBV genotypes from HBV-DNA positive samples obtained from screening blood donors at the Social Security System of Panama and to estimate its possible origin. From 59,696 blood donors tested for HBV infection during 2010–2012, there were 74 HBV-DNA positive subjects. Analysis of the partial PreS2-S region of 27 sequences shows that 21% of the infections were caused by genotype A, 3% by genotype D and 76% by genotype F. In addition, we were able to confirm circulation of six sub-genotypes A1, A2, A3, D4, F3, F1 and a proposed new sub-genotype denominated F5pan. We found a confinement of sub-genotypes F1 and F5pan to the western area of Panama. The tMRCA analysis suggests a simultaneous circulation of previously described sub-genotypes rather than recent introductions of the Panamanian sub-genotypes in the country. Moreover, these results highlight the need of more intensive research of the HBV strains circulating in the region at the molecular level. In conclusion, Panama has a high HBV genotype diversity that includes a new proposed sub-genotype, an elevated number of PreCore-Core mutations, and confinement of these variants in a specific geographical location.</p></div