Efecto antitumoral del selenito sódico solo y en combinación con gemcitabina en cáncer de páncreas: Estudios in vitro e in vivo

Abstract

Pancreatic cancer and, above all, pancreatic adenocarcinoma is one of the deadliest with a 5-year survival of less than 5% in advanced stages (III and IV). This fact is largely due to a delay in its diagnosis and its great aggressiveness and chemoresistance. Sodium selenite is an inorganic oxo-salt source of selenium. It is a compound toxic to humans at high doses but with a therapeutic range that allows its use as an antitumor in various solid tumors, as shown by various investigations carried out in recent years. The cellular damage caused by sodium selenite is attributed to its ability to deplete reduced glutathione and reduced thioredoxin and, therefore, with the cellular deprotection against reactive oxygen species, which activates mechanisms of cell death due to protein damage. and cellular nucleic acids. This antitumor power has been described as selective with tumor cells and especially with those that express resistance mechanisms to chemotherapeutic agents. Given that there are no studies with sodium selenite in pancreatic cells and tumors and taking into account the chemoresistance, ominous prognosis and limited efficacy of systemic treatments, the objective of this doctoral thesis is to test sodium selenite alone and in combination with chemotherapy (gemcitabine) in pancreatic cancer in vitro and in vivo. For this, in vitro studies were carried out: cell proliferation and cytotoxicity with sulforhodamine B with the PANC-1 (human) and Pan02 (murine) cell lines, cell cycle studies with propidium iodide and DIiC1, immunofluorescence assays for AIF translocation and inhibition with benzamide, Western-Blott studies to detect phospho-p38, colony and cell migration assays, CSC spherical formation studies, multicellular tumor spheroids (MTS) studies, and tumor angiogenesis assays. On the other hand, in vivo studies were carried out with experimental animals (albino mice) which were inoculated with subcutaneous tumors with the Pan02 line and were treated for 10 treatment cycles with selenite, gemcitabine and a combination of both. Tumor volume, tumor growth, tumor metabolic activity, survival and tumor histology studies were carried out with basic histological techniques and immunofluorescence. The results obtained showed the potent in vitro antitumor capacity of sodium selenite alone and synergistically in combination with gemcitabine. These studies also showed that selenite's antitumor activity does not cause notable cell cycle stops and does affect mitochondrial depolarization. When analyzing the mechanism of cell death, it was found that it is dependent on the activation of the repairing enzyme PARP and the nuclear translocation of the mitochondrial factor AIF. On the other hand, it was found that the synergy between selenite and gemcitabine is related to the fact that selenite is capable of activating factor p38, which is closely related to tumor cell death caused by gemcitabine. When analyzing tumor aggressiveness parameters, it was possible to verify how selenite both alone and in combination with gemcitabine is capable of reducing tumor cell migration, colony formation, CSC spherical formation, MTS growth and tumor angiogenesis. All these facts were demonstrated with studies with experimental animals where it was found that selenite both alone and in combination with gemcitabine, in the latter case, in a more accentuated way, inhibits tumor growth, tumor activity, increases survival of the mice and also decreases in vivo tumor aggressiveness parameters such as proliferative markers, invasiveness and angiogenesis. That is why sodium selenite both alone and in combination with gemcitabine has promising antitumor activity against pancreatic cancer both in vitro and in vivo with experimental animals, thus justifying the performance of clinical trials in humans in order to confirm these findings.