Identificación del factor de splicing SLU7 como controlador de la estabilidad genómica

Hemos estudiado el desconocido papel del factor de splicing SLU7 como mediador de la integridad genómica y regulador de la progresión en la mitosis durante el ciclo celular. Hemos demostrado que la disminución de la expresión de SLU7 en líneas celulares cancerosas de diferentes orígenes contribuye (1) a la formación de híbridos RNA:DNA (R-loops) asociados con la inducción de daño en el DNA y (2) a la parada en la mitosis asociada con la pérdida de cohesión entre las cromátidas hermanas. Ambos eventos están directamente relacionados con la inducción de inestabilidad genómica, característica fundamental de la carcinogénesis. Tanto in vitro como in vivo, hemos caracterizado los mecanismos moleculares que implican alteraciones del splicing y la generación de proteínas aberrantes de SRSF3 y la disminución de SRSF1 y sororina. Nuestros datos presentan a SLU7 como un guardián de la estabilidad genómica y la disminución de su expresión observada en el hígado enfermo de los pacientes podría estar participando en el proceso de hepatocarcinogénesis. Así mismo, en las células transformadas la dependencia de SLU7 para su supervivencia, lo presentan como una nueva diana terapéutica para el cáncer

Splicing factor SLU7 prevents oxidative stress-mediated hepatocyte nuclear factor 4α degradation, preserving hepatic differentiation and protecting from liver damage

Background and aims: Hepatocellular dedifferentiation is emerging as an important determinant in liver disease progression. Preservation of mature hepatocyte identity relies on a set of key genes, predominantly the transcription factor hepatocyte nuclear factor 4α (HNF4α) but also splicing factors like SLU7. How these factors interact and become dysregulated and the impact of their impairment in driving liver disease are not fully understood. Approach and results: Expression of SLU7 and that of the adult and oncofetal isoforms of HNF4α, driven by its promoter 1 (P1) and P2, respectively, was studied in diseased human and mouse livers. Hepatic function and damage response were analyzed in wild-type and Slu7-haploinsufficient/heterozygous (Slu7+/- ) mice undergoing chronic (CCl4 ) and acute (acetaminophen) injury. SLU7 expression was restored in CCl4 -injured mice using SLU7-expressing adeno-associated viruses (AAV-SLU7). The hepatocellular SLU7 interactome was characterized by mass spectrometry. Reduced SLU7 expression in human and mouse diseased livers correlated with a switch in HNF4α P1 to P2 usage. This response was reproduced in Slu7+/- mice, which displayed increased sensitivity to chronic and acute liver injury, enhanced oxidative stress, and marked impairment of hepatic functions. AAV-SLU7 infection prevented liver injury and hepatocellular dedifferentiation. Mechanistically we demonstrate a unique role for SLU7 in the preservation of HNF4α1 protein stability through its capacity to protect the liver against oxidative stress. SLU7 is herein identified as a key component of the stress granule proteome, an essential part of the cell's antioxidant machinery. Conclusions: Our results place SLU7 at the highest level of hepatocellular identity control, identifying SLU7 as a link between stress-protective mechanisms and liver differentiation. These findings emphasize the importance of the preservation of hepatic functions in the protection from liver injury

Preclinical models for prediction of immunotherapy outcomes and immune evasion mechanisms in genetically heterogeneous multiple myeloma

The historical lack of preclinical models reflecting the genetic heterogeneity of multiple myeloma (MM) hampers the advance of therapeutic discoveries. To circumvent this limitation, we screened mice engineered to carry eight MM lesions (NF-kappaB, KRAS, MYC, TP53, BCL2, cyclin D1, MMSET/NSD2 and c-MAF) combinatorially activated in B lymphocytes following T cell-driven immunization. Fifteen genetically diverse models developed bone marrow (BM) tumors fulfilling MM pathogenesis. Integrative analyses of 500 mice and 1,000 patients revealed a common MAPK-MYC genetic pathway that accelerated time to progression from precursor states across genetically heterogeneous MM. MYC-dependent time to progression conditioned immune evasion mechanisms that remodeled the BM microenvironment differently. Rapid MYC-driven progressors exhibited a high number of activated/exhausted CD8+ T cells with reduced immunosuppressive regulatory T (Treg) cells, while late MYC acquisition in slow progressors was associated with lower CD8+ T cell infiltration and more abundant Treg cells. Single-cell transcriptomics and functional assays defined a high ratio of CD8+ T cells versus Treg cells as a predictor of response to immune checkpoint blockade (ICB). In clinical series, high CD8+ T/Treg cell ratios underlie early progression in untreated smoldering MM, and correlated with early relapse in newly diagnosed patients with MM under Len/Dex therapy. In ICB-refractory MM models, increasing CD8+ T cell cytotoxicity or depleting Treg cells reversed immunotherapy resistance and yielded prolonged MM control. Our experimental models enable the correlation of MM genetic and immunological traits with preclinical therapy responses, which may inform the next-generation immunotherapy trials