Browsing by Author "Canals, Andrea"

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    Major Histocompatibility Complex Class I-Related Chain A (MICA) Allelic Variants Associate With Susceptibility and Prognosis of Gastric Cancer
    (Frontiers Media SA, 2021) Toledo-Stuardo, Karen; Ribeiro, Carolina H.; Canals, Andrea; Morales, Marcela; Garate, Valentina; Rodríguez-Siza, José; Tello, Samantha; Bustamante, Marco; Armisén, Ricardo; Matthies, Douglas J.; Zapata-Torres, Gerald; González-Hormazabal, Patricio
    Gastric cancer (GC) is the fifth most prevalent type of cancer worldwide. Gastric tumor cells express MICA protein, a ligand to NKG2D receptor that triggers natural killer (NK) cells effector functions for early tumor elimination. MICA gene is highly polymorphic, thus originating alleles that encode protein variants with a controversial role in cancer. The main goal of this work was to study MICA gene polymorphisms and their relationship with the susceptibility and prognosis of GC. Fifty patients with GC and 50 healthy volunteers were included in this study. MICA alleles were identified using Sanger sequencing methods. The analysis of MICA gene sequence revealed 13 MICA sequences and 5 MICA-short tandem repeats (STR) alleles in the studied cohorts We identified MICA*002 (*A9) as the most frequent allele in both, patients and controls, followed by MICA*008 allele (*A5.1). MICA*009/049 allele was significantly associated with increased risk of GC (OR: 5.11 [95% CI: 1.39–18.74], p = 0.014). The analysis of MICA-STR alleles revealed a higher frequency of MICA*A5 in healthy individuals than GC patients (OR = 0.34 [95% CI: 0.12–0.98], p = 0.046). Survival analysis after gastrectomy showed that patients with MICA*002/002 or MICA*002/004 alleles had significantly higher survival rates than those patients bearing MICA*002/008 (p = 0.014) or MICA*002/009 (MICA*002/049) alleles (p = 0.040). The presence of threonine in the position MICA-181 (MICA*009/049 allele) was more frequent in GC patients than controls (p = 0.023). Molecular analysis of MICA-181 showed that the presence of threonine provides greater mobility to the protein than arginine in the same position (MICA*004), which could explain, at least in part, some immune evasion mechanisms developed by the tumor. In conclusion, our findings suggest that the study of MICA alleles is crucial to search for new therapeutic approaches and may be useful for the evaluation of risk and prognosis of GC and personalized therapy.
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    Vitamin D deficiency/insufficiency on healthy infants receiving standard supplementation
    (2022) Bravo, Paulina; Navarro, Ernesto; Mora, Marcela; Calvanese, Marlene; Taub, Marianne; Pérez, Diego; Barros, José Ignacio; Guevara, Mercedes; Pérez, Angélica; Canals, Andrea
    La vitamina D (VD) es indispensable para el metabolismo del calcio y fósforo, su deficiencia puede causar raquitismo. En Chile se suplementa con 400 UI /diarias desde el primer mes hasta el año de vida. Objetivo: Describir las concentraciones plasmáticas de VD en lactantes sanos suplementados y secundariamente, evaluar la asociación del estatus de VD con estacionalidad y estado nutricional. Sujetos y Método: Estudio de corte transversal. Se evaluó a lactantes con lactancia materna exclusiva o mixta que acudían a controles pediátricos mensuales y recibían suplementación de VD a dosis de 400 UI diarias. A los 6 meses de edad se midió la concentración plasmática de VD, el peso y la talla. Posteriormente se clasificó el estado nutricional (peso/edad y peso/talla) según los referentes de la OMS. De acuerdo a la concentración plasmática de VD, se definió como normal ≥ 30 ng/ml, insuficiencia si esta fue entre 20 y 29 ng/ml y deficiencia < 20 ng/ml. Resultados: Se estudiaron 40 lactantes, 40% tuvieron concentracio nes de VD insuficientes y 40% deficientes. En el modelo de regresión lineal múltiple, las variables que se asociaron, de modo significativo, con una menor concentración de VD fueron: el periodo del año invierno-primavera (p = 0,007) y el riesgo de desnutrición (p = 0,038). Conclusiones: La frecuencia de deficiencia e insuficiencia de VD es elevada en nuestra población suplementada, dicho déficit es mayor durante el invierno y la primavera y en sujetos con riesgo de desnutrición.

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