Andrés Acevedo

The Combined Expression Patterns of Ikaros Isoforms Characterize Different Hematological Tumor Subtypes

A variety of genetic alterations are considered hallmarks of cancer development and progression. The Ikaros gene family, encoding for key transcription factors in hematopoietic development, provides several examples as genetic defects in these genes are associated with the development of different types of leukemia. However, the complex patterns of expression of isoforms in Ikaros family genes has prevented their use as clinical markers. In this study, we propose the use of the expression profiles of the Ikaros isoforms to classify various hematological tumor diseases. We have standardized a quantitative PCR protocol to estimate the expression levels of the Ikaros gene exons. Our analysis reveals that these levels are associated with specific types of leukemia and we have found differences in the levels of expression relative to five interexonic Ikaros regions for all diseases studied. In conclusion, our method has allowed us to precisely discriminate between B-ALL, CLL and MM cases. Differences between the groups of lymphoid and myeloid pathologies were also identified in the same way.

Primary mediastinal large B-cell lymphoma: transcriptional regulation by miR-92a through FOXP1 targeting

Background Primary mediastinal large B-cell lymphoma (PMBL) shares pathological features with diffuse large B-cell lymphoma (DLBCL), and molecular features with classical Hodgkin lymphoma (cHL). The miR-17∼92 oncogenic cluster, located at chromosome 13q31, is a region that is amplified in DLBCL. Methods Here we compared the expression of each member of the miR-17∼92 oncogenic cluster in samples from 40 PMBL patients versus 20 DLBCL and 20 cHL patients, and studied the target genes linked to deregulated miRNA in PMBL. Results We found a higher level of miR-92a in PMBL than in DLBCL, but not in cHL. A combination of in silico prediction and transcriptomic analyses enabled us to identify FOXP1 as a main miR-92a target gene in PMBL, a result so far not established. This was confirmed by 3UTR, and RNA and protein expressions in transduced cell lines. In vivo studies using the transduced cell lines in mice enabled us to demonstrate a tumor suppressor effect of miR-92a and an oncogenic effect of FOXP1. A higher expression of miR-92a and the down-regulation of FOXP1 mRNA and protein expression were also found in human samples of PMBL, while miR-92a expression was low and FOXP1 was high in DLBCL. Conclusions We concluded to a post-transcriptional regulation by miR-92a through FOXP1 targeting in PMBL, with a clinico-pathological relevance for better characterisation of PMBL.

El perfil de splicing del factor de transcripción ikaros caracteriza subtipos de neoplasias hematológicas

Introduccion La familia Ikaros de factores de transcripcion incluye genes cruciales en desarrollo hematopoyetico y que se han visto relacionados con el desarrollo de diferentes tipos de neoplasias hematologicas. Sin embargo, la compleja expresion de las isoformas en esta familia ha impedido cualquier utilidad clinica de las misma y esta el momento solo se ha caracterizado la presencia de ciertas isoformas en casos de leucemias y que, sin embargo, tambien aparecen en individuos sanos. Objetivo Basandonos en lo anterior, en el presente estudio se propone la estandarizacion una nueva metodologia que permita el estudio del conjunto completo de isoformas en la muestra, ya que todo parece indicar que es el desequilibrio de isoformas lo que se podria asociar a la enfermedad. Materiales y metodos Para ello se cuantificaron las regiones inter-exonicas de Ikaros a traves de qRT-PCR lo que permitio describir un perfil de expresion para el conjunto de isoformas presentes en cada paciente, que incluye diferencias de expresion de determinados exones, asi como presencia de procesamientos no canonicos. Resultados De esta manera hemos sido capaces de discriminar grupos de patologias, pudiendo discriminar grupos de leucemias linfoides agudas, leucemias linfoides cronicas, leucemias mieloides cronicas y mielomas multiples. Del mismo modo se encontraron diferencias entre los grupos de estirpe linfoides frente a los mieloides. Adicionalmente, se describio la evolucion del perfil de expresion de un paciente diagnosticado de leucemia mieloide cronica que evoluciono a leucemia linfoide aguda y que permitio observar variaciones moleculares en este tipo de patologias evolutivas. Conclusiones Estos resultados permiten inferir que el conjunto de isoformas Ikaros, y no la sobre-expresion de una sola de ellas, es caracteristico de la enfermedad y por tanto su estudio puede llegar a ser un buen marcador diagnostico. Ademas existen caracteristicas concretas, como la presencia de procesamientos no canonicos, que permitirian una implementacion rapida para el diagnostico de subgrupos dentro de algunas de las patologias y cuyo estudio es de alto interes ante la posibilidad de que supongan algun tipo de caracteristicas pronosticas.