Person: Armisen, Ricardo
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Publication MET Exon 14 Skipping and Novel Actionable Variants: Diagnostic and Therapeutic Implications in Latin American Non-Small-Cell Lung Cancer Patients(2024) Rivas, Solange; Sepúlveda, Romina V.; Tapia, Ignacio; Estay, Catalina; Soto, Vicente; Blanco, Alejandro; González, Evelin; Armisen, RicardoTargeted therapy indications for actionable variants in non-small-cell lung cancer (NSCLC) have primarily been studied in Caucasian populations, with limited data on Latin American patients. This study utilized a 52-genes next-generation sequencing (NGS) panel to analyze 1560 tumor biopsies from NSCLC patients in Chile, Brazil, and Peru. The RNA sequencing reads and DNA coverage were correlated to improve the detection of the actionable MET exon 14 skipping variant (METex14). The pathogenicity of MET variants of uncertain significance (VUSs) was assessed using bioinformatic methods, based on their predicted driver potential. The effects of the predicted drivers VUS T992I and H1094Y on c-MET signaling activation, proliferation, and migration were evaluated in HEK293T, BEAS-2B, and H1993 cell lines. Subsequently, c-Met inhibitors were tested in 2D and 3D cell cultures, and drug affinity was determined using 3D structure simulations. The prevalence of MET variants in the South American cohort was 8%, and RNA-based diagnosis detected 27% more cases of METex14 than DNA-based methods. Notably, 20% of METex14 cases with RNA reads below the detection threshold were confirmed using DNA analysis. The novel actionable T992I and H1094Y variants induced proliferation and migration through c-Met/Akt signaling. Both variants showed sensitivity to crizotinib and savolitinib, but the H1094Y variant exhibited reduced sensitivity to capmatinib. These findings highlight the importance of RNA-based METex14 diagnosis and reveal the drug sensitivity profiles of novel actionable MET variants from an understudied patient populationPublication SKI regulates rRNA transcription and pericentromeric heterochromatin to ensure centromere integrity and genome stability(2025) Pola, Víctor; Carrero, David; Sagredo, Eduardo; Inostroza, Víctor; Cappelli, Claudio; Rivas, Solange; Bitrán, Mirita; Zambrano, Evelyn; Gonzalez, Evelin; Morales, Fernanda; Manterola, Marcia; Montecino, Martín; Armisen, Ricardo; Marcelain, KatherineAccurate chromosome segregation and ribosomal gene expression silencing are essential for maintaining genome integrity, and disruptions in these processes are key for oncogenesis and cancer progression. Here, we demonstrate a novel role for the transcriptional co-repressor SKI in regulating rDNA and pericentromeric heterochromatin (PCH) silencing in human cells. We found that SKI localizes to the rDNA promoter on acrocentric chromosomes and is crucial for maintaining H3K9 trimethylation (H3K9me3) and repressing 45S rRNA gene expression. SKI is also associated with BSR and HSATII satellites within PCH, where is necessary for H3K9 methylation and recruitment of SUV39H1 and HP1α, key players for heterochromatin silencing and centromere function. Consequently, SKI deficiency disrupted centromere integrity and resulted in aberrant chromosome segregation, micronuclei formation, and chromosome instability. The identification of SKI as a key participant in the epigenetic-mediated silencing of pericentromeric and ribosomal DNA provides a fundamental insight, paving the way for new research into the intricate relationship between transcriptional regulation and genome instability during cancer progression, and opening novel opportunities for therapeutic intervention.