Splicing regulator SLU7 preserves survival of hepatocellular carcinoma cells and other solid tumors via oncogenic miR-17-92 cluster expression.

Resisting death is a central hallmark of cancer cells. Tumors rely on a number of genetic mechanisms to avoid apoptosis, and alterations in mRNA alternative splicing are increasingly recognized to have a role in tumorigenesis. In this study, we identify the splicing regulator SLU7 as an essential factor for the preservation of hepatocellular carcinoma (HCC) cells viability. Compared with hepatocytes, SLU7 expression is reduced in HCC cells; however, further SLU7 depletion triggered autophagy-related cellular apoptosis in association with the overproduction of reactive oxygen species. Remarkably, these responses were not observed in primary human hepatocytes or in the well-differentiated HepaRG cell line. Mechanistically, we demonstrate that SLU7 binds the C13orf25 primary transcript in which the polycistronic oncomir miR-17-92 cluster is encompassed, and is necessary for its processing and expression. SLU7 knockdown altered the splicing of the C13orf25 primary transcript, and markedly reduced the expression of its miR-17, miR-20 and miR-92a constituents. This led to the upregulation of CDKN1A (P21) and BCL2L11 (BIM) expression, two bona fide targets of the miR-17-92 cluster and recognized mediators of its pro-survival and tumorigenic activity. Interestingly, altered splicing of miR-17-92 and downregulation of miR-17 and miR-20 were not observed upon SLU7 knockdown in non-transformed hepatocytes, but was found in other (HeLa, H358) but not in all (Caco2) non-hepatic tumor cells. The functional relevance of miR-17-92 dysregulation upon SLU7 knockdown was established when oxidative stress, autophagy and apoptosis were reversed by co-transfection of HCC cells with a miR-17 mimic. Together, these findings indicate that SLU7 is co-opted by HCC cells and other tumor cell types to maintain survival, and identify this splicing regulator as a new determinant for the expression of the oncogenic miR-17-92 cluster. This novel mechanism may be exploited for the development of antitumoral strategies in cancers displaying such SLU7-miR-17-92 crosstalk.

[A study of arteriosclerotic disease and of ischemic cardiopathy in particular and the associated risk factors in the Autonomous Basque Community. The Euzkadi project]. / Estudio de la enfermedad arteriosclerosa y cardiopatía isquémica en particular y factores de riesgo asociados en la Comunidad Autónoma Vasca. Proyecto Euzkadi.

The aim of the Euzkadi Project was to know the prevalence rate of cardiovascular disease and the high risk factors (hypertension, hypercholesterolemia and cigarette smoking) in the Basque Country to carry out an intervention trials to reduce these factors if we have collaboration of the Public Health Service. We have studied a sample of 4,800 men, 25-64 years old, randomly selected (1,600 men in each province), the examination was done by cardiologist using the cardiovascular questionnaire by Blackburn and Rose, the cholesterol was tested in WHO Collaborating Lipid Reference Center (Prague) and the electrocardiogram was studied by Minnesota Code. The rate of Atherosclerotic disease was 69%, coronary heart disease 49% (12% angina típica, 9% angina atípica and 28% myocardial infarction), stroke 7%, and peripheral vascular disease 13%. The rate of silent myocardial infarction was 31%. The rate of hypertension was 24%, hypercholesterolemia 14% and cigarette smoking 40%.