MRP4/ABCC4 en adenocarcinomas ductales pancreáticos (PDAC): Estudio de los mecanismos que conducen a la desregulación de su Expresión e implicancias funcionales y terapéuticas
Pancreatic ductal adenocarcinoma (PDAC) stands out as the predominant form of pancreatic cancer, encompassing approximately 95 % of cases. Characterized by a highly invasive and metastatic pathophysiology, PDAC ranks among the most aggressive and lethal tumor types, constituting the third leading ca...
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| Formato: | Tesis doctoral acceptedVersion |
| Lenguaje: | Español |
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Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica
2024
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| Acceso en línea: | http://repositoriouba.sisbi.uba.ar/gsdl/cgi-bin/library.cgi?a=d&c=posgraafa&cl=CL1&d=HWA_7873 https://repositoriouba.sisbi.uba.ar/gsdl/collect/posgraafa/index/assoc/HWA_7873.dir/7873.PDF |
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| Sumario: | Pancreatic ductal adenocarcinoma (PDAC) stands out as the predominant form of pancreatic cancer, encompassing approximately 95 % of cases. Characterized by a highly invasive and metastatic pathophysiology, PDAC ranks among the most aggressive and lethal tumor types, constituting the third leading cause of cancer-related mortality. Its high aggressiveness is reflected in its poor prognosis, with a median survival rate of less than 12 %. Moreover, these tumours exhibit intrinsic resistance to chemotherapy, while their poor irrigation hampers systemic access to anti-tumor agents. A distinguishing feature of PDAC is the presence of a desmoplastic stroma, playing a pivotal role in both its heightened aggressiveness and frequent therapeutic setbacks. Current therapeutic modalities involving chemo and radiotherapy show limited efficacy, underscoring the scientific challenge of understanding the cellular and molecular biology of this type of cancer in order to identify early detection biomarkers and/or novel therapeutic targets. In this regard, our laboratory's previous findings have shown that the xenobiotic transporter ABCC4/MRP4 is positioned as a prognostic biomarker and therapeutic target in PDAC. Expression levels of ABCC4 are notably elevated in primary PDAC tumours, circulating tumour cells derived from patients, and tumour cell lines cultured in vitro, compared to non-tumour pancreatic tissue. Building upon this background and seeking to provide further evidence for the validation of ABCC4/MRP4 as a biomarker and therapeutic target, in this Thesis, we aimed to deeply characterise the molecular and epigenetic mechanisms governing its endogenous expression in PDAC. Furthermore, the objective is to unravel the transcriptomic and functional alterations correlated with its expression in both the tumor and stromal compartments. To this end, we conducted RNA-seq studies on the BxPC3 cell line overexpressing ABCC4/MRP4 in cultured and xenograft settings. Comprehensive transcriptomic data mining and bioinformatic analyses were performed on preclinical models and primary tumors from patients. The outcomes reveal that the heightened expression of ABCC4/MRP4 instigates an aberrant epigenomic and transcriptional landscape within the tumour parenchyma. This dysregulation is functionally associated with the epithelial-mesenchymal transition. Moreover, in the stromal compartment, it promotes the deregulation of cellular processes linked to increased collagen synthesis and fibrosis, characteristic of the desmoplastic reaction. Furthermore, we characterised four cis-regulatory sites of the ABCC4 gene in PDAC cell lines with varying endogenous MRP4 levels and aggressiveness. We proposed a regulatory model based on the selective binding of pioneer transcription factors FOXA1 and GATA2 to these sites. Our findings reveal that in xenografts derived from the low-grade HPAF-II cell line, the cis-regulatory sites of ABCC4 are occupied by the proepithelial factor FOXA1. In contrast, in the high-grade PANC1 line, these sites are occupied by the promesenchymal factor GATA2, leading to a consequential upsurge in ABCC4 expression levels. Finally, we further explored the functional impact of MRP4 on the tumor stroma. We showed that incubating L929 fibroblasts with conditioned media from BxPC3-MPR4+ cells or with cAMP, along with its metabolites 5'AMP and adenosine, induces the activation, migration, and proliferation of fibroblasts, while concurrently inducing the expression of fibrosis markers in these cells. In summary, the results presented here reaffirm the potential of ABCC4/MRP4 as a therapeutic target in PDAC, postulating its inhibition as a dual-impact strategy to modulate both parenchymal tumorigenesis and stromal-mediated chemoresistance. |
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