Introduction and Clinical Justification: Pancreatic ductal adenocarcinoma (ADCP) has a high prevalence, being radically treatable in <20% of patients, justifying research into early diagnosis and treatment methods. To help to this aim, genetically modified murine models which reproduce its oncogenesis have been developed in the last 15 years. ADCP develops from preneoplastic lesions that are not yet invasive. Main pancreatic duct ligation (PDL) induces physiological exocrine pancreatic atrophy through apoptosis; acinar cells are replaced by fibroadipose tissue, a process Tp53 gene-mediated. During the development of ADCP Tp53 is inactivated, collaborating in the development of cancer. These effects have been described in both clinical and experimental settings but, up to date, there are no published studies that describe how atrophy induction affects the development of preneoplastic lesions in a ADCP model. The hypothesis of this work is that early PDL, when Tp53 and apoptosis are still active, in a well-defined model of ADCP, can induce sufficient exocrine atrophy to prevent the progression of preneoplastic lesions into cancer. The main objective was to assess the effect of PDL through histological analysis of preneoplastic lesions, and genomic analysis. Regarding methodology, the absence of similar studies implied carrying out a pilot study. An analytical, experimental, prospective, single-center study was designed using a murine model, with a sample estimate of 88 animals distributed in 5 experimental groups. The murine model Ptf1a-Cre (+/ki); K-ras LSLG12Vgeo (+/ki) was used, which was developed at CNIO in Madrid. The following were established: 1. Group PDL-Kras group, which underwent selective PDL in the splenic lobe of the pancreas; 2. Group sham-Kras, as control of the surgical technique, which underwent surgical pancreatic isthmus dissection, but without PDL; and 3. Group control-Kras, which did not undergo any surgery, analyzing only preneoplastic lesions development intrinsic to the model. Two other control groups of the genetic backgrounds used for the development of the transgenic model were considered; Groups PDL-Cre and PDL-G, subjected to PDL. Analysis were performed at; 1st, 3rd and 6th postoperative months (maximum follow-up: 9 months of life), regarding the presence and number of preneoplastic lesions (PanIN 1, 2, 3 and atypical flat lesions- AFL-) in the pancreas proximal to the ligation (PP) and in the distal pancreas (PD; splenic lobe), for each experimental group, as well as differential gene expression. The clinical and histological impact of PDL was also analyzed. To perform all this, clinical, biochemical, histological, and genomic analyzes (using Limma and GSEA) were carried out. Statistical analysis was performed using SPSS. Results: In PDL-Kras group, significantly fewer PanIN 1, 2 and AFL lesions were observed in the PD compared to the PP. The control-Kras and sham-Kras groups had a 7 and 9-fold risk-increase of presenting PanIN 2, 3 and AFL in their PD, compared to the PD of PDL-Kras mice. At a genomic level, an inhibition of acinar function was observed in PD of the PDL-Kras group, as well as an overexpression in PP of ADCP carcinogenesis-related genes. It is thus concluded that: 1. The PDL technique in the murine PDAC model considered is a procedure that induces exocrine atrophy and a decrease in the number of preneoplastic lesions in ligated PD compared to PP. At a genomic level, it could inhibit the expression of ADCP carcinogenesis-related genes.
| Date of Award | 25 Jun 2021 |
|---|
| Original language | Spanish |
|---|
| Supervisor | Fernando Burdio Pinilla (Director), Luis Grande Posa (Director) & Rita Quesada Díez (Director) |
|---|