Parejo Alonso, Beatriz
Sancho Andrés, Patricia (dir.)
Universidad de Zaragoza,
2023
Resumen: Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive disease characterized by its metastatic potential and chemoresistance. These traits are partially attributable to the highly tumorigenic pancreatic cancer stem cells (PaCSCs). Interestingly, these cells show unique features in order to sustain their identity and functionality, some of them amenable for therapeutic intervention. Importantly, our group has previously described that the ratio between MYC and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC1a) controls the oxygen phosphorylation (OXPHOS)- dependent metabolic phenotype of PaCSCs to maintain their pluripotent status. This scenario, apparently, renders PaCSCs highly sensitive to mitochondrial inhibition with Metformin. However, different clones of PaCSCs with distinct levels of MYC/PGC1a arise upon such metabolic stress situation, thereby generating resistance to this compound. Therefore, we hypothesize that deciphering the mechanisms underlying PaCSCs biology bears the potential to find novel targets amenable for therapeutic intervention against this extremely chemoresistant subpopulation with tumor-initiating properties. To that end, the main aim of this doctoral thesis is to study the specific traits of PaCSCs that contribute to their inherent aggressiveness in order to identify novel targetable orchestrators of their functionality.
On the one hand, compiling data from our group suggests that peroxisome proliferator-activated receptor delta (PPAR-d) correlates with pancreatic cancer progression and metastatic dissemination in response to energy deprivation and microenvironmental cues derived from tumor-associated macrophages (TAMs). However, the mechanistic basis of this regulation remains elusive. Here, we demonstrate that PPARD was consistently upregulated in response to different metabolic stressors (i.e., macrophage-derived conditioned medium or low dose Etomoxir) prior to epithelial-to-mesenchymal transition (EMT)-related functional changes. Intriguingly, treatment with various PPAR-d agonists induced enhanced invasiveness. In addition, both experimental approaches increased the MYC/PGC1a ratio, suggesting that the metabolic modulation that takes place in PaCSCs is orchestrated upstream by PPAR-d. The increased aggressiveness found in vitro was translated into enhanced metastatic dissemination in vivo. Mechanistically, PPARD overexpression or incubation with the agonist GW0742 induced an early activation of the MYC promoter, reducing the activity of
PGC1A promoter. Moreover, MYC therapeutic targeting blocked the invasion induced by PPAR-d, suggesting its pro-metastatic effects were dependent on MYC/PGC1a. Conversely, pharmacological targeting of PPAR-d inhibited the invasive capacity conferred by MCM or Etomoxir, or basal invasiveness in highly metastatic cells. Importantly, in vivo treatment with the PPAR-d antagonists GSK3787 or GSK0660 showed decreased liver metastases incidence, which strongly supports the pro-metastatic role of PPAR-d in PDAC.
On the other hand, screening of phospho-receptor tyrosine kinases revealed that PaCSCs harbored increased activation of anaplastic lymphoma kinase (ALK). We subsequently demonstrated that oncogenic ALK signaling contributes to tumorigenicity in PDAC patient-derived xenografts (PDXs) by promoting stemness through ligand-dependent activation. Indeed, the ALK ligands midkine (MDK) or pleiotrophin (PTN) increased self-renewal, clonogenicity and CSC frequency in several in vitro local and metastatic PDX models. Conversely, treatment with the clinically-approved ALK inhibitors Crizotinib and Ensartinib decreased PaCSC content and functionality, including invasiveness, in vitro and in vivo, by inducing cell death. Strikingly, ALK inhibitors sensitized chemoresistant PaCSCs to Gemcitabine, as the most used chemotherapeutic agent for PDAC treatment. Consequently, ALK inhibition delayed tumor relapse after chemotherapy in vivo by effectively decreasing the content of PaCSCs. In summary, our results demonstrate that targeting the MDK/PTN-ALK axis with clinically-approved inhibitors impairs in vivo tumorigenicity and chemoresistance in PDAC.
Taken together, our data strongly suggests that blockade of PaCSCs specific characteristics with pharmacologic inhibitors by different means, such as modulating their metabolic phenotype or targeting specific signaling pathways, decreases the metastatic incidence, tumorigenicity and chemoresistance in PDAC.
Resumen (otro idioma):
On the one hand, compiling data from our group suggests that peroxisome proliferator-activated receptor delta (PPAR-d) correlates with pancreatic cancer progression and metastatic dissemination in response to energy deprivation and microenvironmental cues derived from tumor-associated macrophages (TAMs). However, the mechanistic basis of this regulation remains elusive. Here, we demonstrate that PPARD was consistently upregulated in response to different metabolic stressors (i.e., macrophage-derived conditioned medium or low dose Etomoxir) prior to epithelial-to-mesenchymal transition (EMT)-related functional changes. Intriguingly, treatment with various PPAR-d agonists induced enhanced invasiveness. In addition, both experimental approaches increased the MYC/PGC1a ratio, suggesting that the metabolic modulation that takes place in PaCSCs is orchestrated upstream by PPAR-d. The increased aggressiveness found in vitro was translated into enhanced metastatic dissemination in vivo. Mechanistically, PPARD overexpression or incubation with the agonist GW0742 induced an early activation of the MYC promoter, reducing the activity of
PGC1A promoter. Moreover, MYC therapeutic targeting blocked the invasion induced by PPAR-d, suggesting its pro-metastatic effects were dependent on MYC/PGC1a. Conversely, pharmacological targeting of PPAR-d inhibited the invasive capacity conferred by MCM or Etomoxir, or basal invasiveness in highly metastatic cells. Importantly, in vivo treatment with the PPAR-d antagonists GSK3787 or GSK0660 showed decreased liver metastases incidence, which strongly supports the pro-metastatic role of PPAR-d in PDAC.
On the other hand, screening of phospho-receptor tyrosine kinases revealed that PaCSCs harbored increased activation of anaplastic lymphoma kinase (ALK). We subsequently demonstrated that oncogenic ALK signaling contributes to tumorigenicity in PDAC patient-derived xenografts (PDXs) by promoting stemness through ligand-dependent activation. Indeed, the ALK ligands midkine (MDK) or pleiotrophin (PTN) increased self-renewal, clonogenicity and CSC frequency in several in vitro local and metastatic PDX models. Conversely, treatment with the clinically-approved ALK inhibitors Crizotinib and Ensartinib decreased PaCSC content and functionality, including invasiveness, in vitro and in vivo, by inducing cell death. Strikingly, ALK inhibitors sensitized chemoresistant PaCSCs to Gemcitabine, as the most used chemotherapeutic agent for PDAC treatment. Consequently, ALK inhibition delayed tumor relapse after chemotherapy in vivo by effectively decreasing the content of PaCSCs. In summary, our results demonstrate that targeting the MDK/PTN-ALK axis with clinically-approved inhibitors impairs in vivo tumorigenicity and chemoresistance in PDAC.
Taken together, our data strongly suggests that blockade of PaCSCs specific characteristics with pharmacologic inhibitors by different means, such as modulating their metabolic phenotype or targeting specific signaling pathways, decreases the metastatic incidence, tumorigenicity and chemoresistance in PDAC.
Resumen (otro idioma):
Pal. clave: ciencias de la vida ; biología celular ; biología molecular
Titulación: Programa de Doctorado en Bioquímica y Biología Molecular
Plan(es): Plan 485
Área de conocimiento: Ciencias
Nota: Presentado: 27 10 2023
Nota: Tesis-Univ. Zaragoza, , 2023
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