Biology subjects

de Santa Barbara, P.

Publications and source records attributed to de Santa Barbara, P..

5 recordsLinked to original sources

bioRxiv2025

Breaking the redundancy: TAZ outperforms YAP1 in GIST progression

BackgroundGastrointestinal stromal tumors (GIST) are mainly caused by gain-of-function mutations in KIT or PDGFRA genes and are the most common neoplasms of the digestive tract. Imatinib (IM), a tyrosine kinase inhibitor (TKI) targeting these oncogenic drivers, has considerably improved patient outcomes, although resistance remains a major challenge. The transcriptional co-activators YAP1 and TAZ, downstream effectors of the Hippo pathway, have emerged as potential oncogenic drivers in various cancers, including GIST. However, their specific roles in KIT-dependent tumor development remain unclear. MethodsWe used WRAP5-based nanoparticles loaded with specifically designed siRNA to selectively silence YAP1 and/or TAZ proteins in KIT-dependent IM-sensitive GIST cell lines. This nucleic acid delivery system enabled efficient and specific knockdown without cytotoxicity. We assessed the impact on cell proliferation, migration, and gene expression, focusing on YAP1/TAZ targets CYR61 and CTGF. ResultsTAZ silencing resulted in a substantial reduction in GIST-T1 cell proliferation and migration, whereas YAP1 knockdown was comparatively limited. This finding was consistent with an increased TAZ expression in GIST patients, which was associated with shorter progression-free survival and an increased tendency for metastasis development. A slight additive effect was observed upon a combined YAP1/TAZ silencing in the migration assay, suggesting a more complex regulation between these two proteins. CYR61 and CTGF expressions were predominantly regulated by TAZ, though a stronger downregulation was observed upon dual knockdown in a subset of GIST cell lines with differential YAP1 and TAZ basal expression. Finally, CYR61 seemed to be more implicated in cell proliferation inhibition, which is further supported by the correlation between high CYR61 expression and poor prognosis in the GIST patients. ConclusionOur results highlight the central regulatory function of TAZ-CYR61 axis in oncogenic processes in KIT-dependent GIST, with a modest contribution from YAP1. Targeting TAZ, alone or in combination with YAP1, may represent a promising therapeutic approach, particularly in the context of tumor heterogeneity.

cancer biology↗

bioRxiv2025

Multi-protein silencing using WRAP-based nanoparticles: a proof of concept

Cancer remains the leading cause of death, with chemotherapy, radiotherapy, and surgical resection being the primary treatment methods. However, chemotherapys side effects, surgical limitations, and drug resistance present significant challenges. Small interfering RNA (siRNA) has emerged as a promising tool in cancer therapy due to its ability to silence disease-related genes selectively. Recent advancements in non-viral delivery systems, particularly cell-penetrating peptides (CPPs), have enhanced the efficacy of siRNA delivery. The use of siRNA as a therapeutic tool in cancer treatment has been reported. However, silencing only one target protein has only minor effects on tumor cell proliferation as previously shown for WRAP-based nanoparticles targeting cyclin-dependent kinase 4 (CDK4) in human glioblastoma cells. Here, we designed a more sophisticated approach to enhance therapeutic efficacy, encapsulating multiple siRNAs targeting CDK4, cyclin D1 (CD1), and Mcl-1 proteins. The siRNA cocktail, delivered via WRAP5 nanoparticles, effectively silenced these targets and reduced cell proliferation in human glioblastoma cells. Furthermore, the nanoparticles also demonstrated potential therapeutic impact in gastrointestinal stromal tumors (GIST), a rare cancer characterized by its tendency to resist standard treatments. This study highlights the versatility of WRAP5 nanoparticles as a platform for personalized cancer therapy, suggesting that siRNA delivery systems may be tailored to specific cancer types for more effective treatment strategies.

cell biology↗

bioRxiv2024

Obesity induces phenotypic switching of gastric smooth muscle cells through the activation of the PPARD/PDK4/ANGPTL4 pathway

ObjectiveClinical research has identified stomach dysmotility as a common feature of obesity. However, the specific mechanisms driving gastric emptying dysfunction in patients with obesity remain largely unknown. In this study, we investigated potential mechanisms by focusing on the homeostasis of gastric smooth muscle, using tissue samples from both patient and mice, as well as human cell culture system. DesignTissue samples were collected from patients who underwent sleeve gastrectomy for obesity, as well as from control subjects with standard weight who were undergoing treatment for gastric or esophageal carcinoma. Stomach tissues were harvested from mice after 12 weeks on a High-Fat Diet (HFD). Differentiated human gastric smooth muscle cells (SMCs) were treated with lipids, siRNA-peptide-based nanoparticles and/or pharmaceutical compounds. All experimental conditions were analyzed for their effects on SMC differentiation using stage-specific smooth muscle markers. Additionally, lipidomic and RNA sequencing analyses were performed on human gastric SMC cultures. The findings were assessed in patients with obesity to evaluate their clinical relevance. ResultsThe smooth muscle layers in gastric tissue from both patients with obesity and mice fed on a HFD exhibited altered differentiation status. Treatment of differentiated human gastric SMCs with lipids phenocopies these alterations and is associated with increased expression of PDK4 and ANGPTL4. Inhibition of PDK4 or ANGPTL4 upregulation prevents these lipid-induced modifications. Mechanistically, lipid treatment activates PPARD, which regulates PDK4 and ANGPTL4 upregulation, leading to SMC dedifferentiation. Notably, PDK4 and ANGPTL4 levels correlate with immaturity and alteration of gastric smooth muscle in patients with obesity. ConclusionObesity triggers a phenotypic change in gastric SMCs, driven by the activation of the PPARD/PDK4/ANGPTL4 pathway. These mechanistic insights offer potential biomarkers for diagnosing stomach dysmotility in patients with obesity.

physiology↗

bioRxiv2022

High-Resolution Ultrasound and Speckle Tracking: a non-invasive approach to assess in vivo gastrointestinal motility during development

Gastrointestinal motor activity has been extensively studied in adults, conversely only few studies have investigated fetal motor skills. When the gastrointestinal tract starts to contract during the embryonic period and how this function evolves during development are not known. Here, we adapted a non-invasive high-resolution echography technique combined with speckle tracking analysis to examine the gastrointestinal tract motor activity dynamics during chick embryo development. We provided the first recordings of fetal gastrointestinal motility in living embryos. We found that although gastrointestinal contractions appear very early during development, they become synchronized only at the end of the fetal period. To validate this approach, we used various pharmacological inhibitors and BAPX1 gene overexpression in vivo. We found that the enteric nervous system determinates the onset of the synchronized contractions in the stomach. Moreover, alteration of smooth muscle fiber organization led to an impairment of this functional activity. Altogether, our findings show that non-invasive high-resolution echography and speckle tracking analysis allow visualizing and quantifying gastrointestinal motility during development and highlight the progressive acquisition of functional and coordinated gastrointestinal motility before birth.

developmental biology↗

bioRxiv2022

LIX1 controls digestive mesenchyme-derived cell fate decision by regulating cristae organization in mitochondria

Limb Expression 1 (LIX1) is a master regulator of digestive mesenchymal progenitor and GastroIntestinal Stromal Tumor (GIST) cell proliferation by controlling the expression of the Hippo effectors YAP1/TAZ and KIT. However, the underlying mechanisms of these LIX1-mediated regulations and tumor promotion remain to be elucidated. Here, we report that LIX1 is S-palmitoylated on cysteine 84 and localized in mitochondria. LIX1 knock-down affects the mitochondrial ultrastructure, resulting in decreased respiration and mitochondrial reactive oxygen species production. This is sufficient to downregulate YAP1/TAZ and reprogram KIT-positive GIST cells towards the smooth muscle cell lineage with reduced proliferative and invasive capacities. Mechanistically, LIX1 knock-down impairs the stability of the mitochondrial proteins PHB2 and OPA1 that are found in complexes with mitochondrial-specific phospholipids and are required for cristae organization. Supplementation with unsaturated fatty acids counteracts the effects of LIX1 knock-down on mitochondrial morphology and ultrastructure, restores YAP1/TAZ signaling, and consequently KIT levels. Altogether, our findings demonstrate that LIX1 contributes to GIST aggressive potential by modulating YAP1/TAZ and KIT levels, a process that depends on mitochondrial remodeling. Our work brings new insights into the mechanisms that could be targeted in tumors in which YAP1 and TAZ are implicated.

cancer biology↗