Venetoclax resistance induced by activated T cells can be counteracted by sphingosine kinase inhibitors in chronic lymphocytic leukemia.

The treatment of chronic lymphocytic leukemia (CLL) patients with venetoclax-based regimens has demonstrated efficacy and a safety profile, but the emergence of resistant cells and disease progression is a current complication. Therapeutic target of sphingosine kinases (SPHK) 1 and 2 has opened new opportunities in the treatment combinations of cancer patients. We previously reported that the dual SPHK1/2 inhibitor, SKI-II enhanced the in vitro cell death triggered by fludarabine, bendamustine or ibrutinib and reduced the activation and proliferation of chronic lymphocytic leukemia (CLL) cells. Since we previously showed that autologous activated T cells from CLL patients favor the activation of CLL cells and the generation of venetoclax resistance due to the upregulation of BCL-XL and MCL-1, we here aim to determine whether SPHK inhibitors affect this process. To this aim we employed the dual SPHK1/2 inhibitor SKI-II and opaganib, a SPHK2 inhibitor that is being studied in clinical trials. We found that SPHK inhibitors reduce the activation of CLL cells and the generation of venetoclax resistance induced by activated T cells mainly due to a reduced upregulation of BCL-XL. We also found that SPHK2 expression was enhanced in CLL cells by activated T cells of the same patient and the presence of venetoclax selects resistant cells with high levels of SPHK2. Of note, SPHK inhibitors were able to re-sensitize already resistant CLL cells to a second venetoclax treatment. Our results highlight the therapeutic potential of SPHK inhibitors in combination with venetoclax as a promising treatment option for the patients.

Antiproliferative activity and energy calculations of a new triterpene isolated from the palm tree Acrocomia totai.

Acrocomia totai Mart (Arecaceae) is a palm tree native to South America, widely studied for biodiesel production. The aim of this work was to perform the first phytochemical study of A. totai leaves, as well as to do biological assays against human cancer cell lines. A new triterpene of the hopane class named totaiol (1), three known triterpenes (2-4), and two phytosteroids (5-6) were identified. The new natural product was characterized using 1 D and 2 D NMR, single crystal X-ray diffraction analises, and high resolution mass spectrometry. The intercontacts in the crystal packing were also analised. Complete stereochemical characterization of compound 1 revealed an unusual positioning pattern for methyl and isopropenyl groups in the polycyclic skeleton. Compounds 1-5 were evaluated for the first time in antiproliferative assays against Ca Ski, MCF-7 and MCF-10 cells. The new natural product was active against Ca Ski cells with IC50 ≤ 6.25 µg mL-1.

Ski Is Required for Tri-Methylation of H3K9 in Major Satellite and for Repression of Pericentromeric Genes: Mmp3, Mmp10 and Mmp13, in Mouse Fibroblasts.

Several mechanisms directing a rapid transcriptional reactivation of genes immediately after mitosis have been described. However, little is known about the maintenance of repressive signals during mitosis. In this work, we address the role of Ski in the repression of gene expression during M/G1 transition in mouse embryonic fibroblasts (MEFs). We found that Ski localises as a distinct pair of dots at the pericentromeric region of mitotic chromosomes, and the absence of the protein is related to high acetylation and low tri-methylation of H3K9 in pericentromeric major satellite. Moreover, differential expression assays in early G1 cells showed that the presence of Ski is significantly associated with repression of genes localised nearby to pericentromeric DNA. In mitotic cells, chromatin immunoprecipitation assays confirmed the association of Ski to major satellite and the promoters of the most repressed genes: Mmp3, Mmp10 and Mmp13. These genes are at pericentromeric region of chromosome 9. In these promoters, the presence of Ski resulted in increased H3K9 tri-methylation levels. This Ski-dependent regulation is also observed during interphase. Consequently, Mmp activity is augmented in Ski-/- MEFs. Altogether, these data indicate that association of Ski with the pericentromeric region of chromosomes during mitosis is required to maintain the silencing bookmarks of underlying chromatin.

Identification of a New Candidate Locus for Ebstein Anomaly in 1p36.2.

Ebstein anomaly (EA) is a rare congenital heart defect (CHD) with a poorly characterized genetic etiology. However, some EA patients carry deletions in 1p36, all of which have been reported to carry distal deletions and share loss of the PRDM16 gene, which is currently considered the most likely candidate for EA development in this region. Here, we report a patient with an 11.96-Mb proximal 1p36 deletion, without loss of PRDM16, who presented with EA and a proximal deletion phenotype. This finding suggests that PRDM16 loss is not required for the development of EA in 1p36 deletions and that the loss of an additional proximal locus in 1p36 is also likely associated with EA. Our data suggest that a distal locus containing the SKI gene and a proximal locus containing the CHD-associated genes RERE and UBE4B are the most probable etiological factors for EA in patients with 1p36 deletion syndrome.

The Ski Protein is Involved in the Transformation Pathway of Aurora Kinase A.

Oncogenic kinase Aurora A (AURKA) has been found to be overexpresed in several tumors including colorectal, breast, and hematological cancers. Overexpression of AURKA induces centrosome amplification and aneuploidy and it is related with cancer progression and poor prognosis. Here we show that AURKA phosphorylates in vitro the transcripcional co-repressor Ski on aminoacids Ser326 and Ser383. Phosphorylations on these aminoacids decreased Ski protein half-life. Reduced levels of Ski resulted in centrosomes amplification and multipolar spindles formation, same as AURKA overexpressing cells. Importantly, overexpression of Ski wild type, but not S326D and S383D mutants inhibited centrosome amplification and cellular transformation induced by AURKA. Altogether, these results suggest that the Ski protein is a target in the transformation pathway mediated by the AURKA oncogene.

Epidemiología de lesiones por deportes de invierno atendidas en un servicio de urgencia / Epidemiology of winter sports injuries treated in the emergency department

Objective: To analyze the incidence and characteristics of winter injuries treated at an Emergency Department in Santiago, Chile. Method: 198 patients were examined in the Emergency Department after a winter sports related accident between June 1 and October 31, 2004. All of them filled a questionnaire regarding their accident. Results: 119 men (60,1 percent) and 79 women (39,9 percent) with an average age of 23 years (4-65). The technical and environmental conditions in which the injury occurred were homogeneous. 80 percent of the accidents were secondary to a fall. 123 injuries happened during skiing, 63 during snowboarding and 12 by other sports, being 64 percent minor and 36 percent severe injuries. 10,1 percent of patients required hospitalization. Conclusion: Most of the patients were young men, with little experience that fell on minimum to moderately difficult courses. Most of these were low grade injuries.

Objetivo: Analizar incidencia y características de lesiones invernales atendidas en Servicio de Urgencia (SU) de Santiago, Chile durante una temporada invernal. Método: Encuesta realizada a 198 pacientes que consultaron en SU tras accidentarse practicando algún tipo de deporte en nieve entre 1 de Junio y 31 de Octubre de 2004. Resultados: Se atendieron 119 hombres (60,1 por ciento) y 79 mujeres (39,9 por ciento) con promedio de edad de 23 años (4-65). El nivel técnico y las condiciones medioambientales en que ocurrió la lesión fueron homogéneos. 80 por ciento de los accidentes fueron por caída: 123 lesiones por ski, 63 por snowboard y 12 por otros deportes siendo 64 por ciento de lesiones menores y 36 por ciento graves. Un 10,1 por ciento de pacientes requirió hospitalización. Conclusión: El grupo de pacientes mayormente afectados son hombres jóvenes, con escasa experiencia, que sufren caídas esquiando en pistas de dificultad mínima a moderada, siendo la mayoría de las lesiones de carácter menos graves.