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Institute
Pancreatic ductal adenocarcinoma (PDAC), due to its genomic heterogeneity and lack of development of effective therapies, will become the second leading cause of cancer-related death within 10 years. Therefore, identifying novel targets that can predict response to specific treatments is a key goal to personalize pancreatic cancer therapy and improve survival. Given that the occurrence of oncogenic KRAS mutations is a characteristic event in PDAC leading to genome instability, a better understanding of the role of DNA repair mechanisms in this process is desirable. The aim of our study was to investigate the role of the error-prone DNA double strand breaks (DSBs) repair pathway, alt-EJ in the presence of KRAS G12D mutation in pancreatic cancer formation. Our findings showed that oncogenic KRAS contributes to the activation of the alt-EJ mechanism by increasing the expression of Polθ, Lig3 and Mre11, key components of alt-EJ in both mouse and human PDAC models. In addition, we demonstrated that alt-EJ has increased activity in DNA DSBs repair pathway in a mouse and human model of PDAC bearing KRAS G12D mutation. We further focused on estimating the impact of alt-EJ inactivation by polymerase theta (Polθ) deletion on pancreatic cancer development and survival in genetically engineered mouse models (GEMMs). Here, we described that although deficiency of Polθ resulted in delayed cancer progression and prolonged survival of experimental mice, it can lead to full-blown PDAC. Our study showed that disabling one component of the alt-EJ may be insufficient to fully suppress pancreatic cancer progression and a complete understanding of all alt-EJ factors and their involvement in DSB repair and oncogenesis is required.
Serine protease inhibitor Kazal type 1 (SPINK1) plays an important role in preventing pancreatitis by inhibiting activated trypsin in the pancreas. The N34S variant of SPINK1 was found to be associated with chronic pancreatitis. However, this mutation is also expressed in the healthy population, indicating that the mutation alone does not cause the disease.
In this study, we investigated at single molecular level the effect of pH on the binding characteristics of human cationic trypsin to SPINK1 by single-molecule force spectroscopy (SMFS).
We found that at pH 8.0, trypsin shows twice the binding force to wild type SPINK1 (90.9 pN ± 3.9 pN) compared to the N34S mutant (47.3 pN ± 3.9 pN). An acidic pH of 4.8 results in a lower binding forces for trypsin-wild type SPINK1 (41.9 pN ± 4.0 pN) to a similar level as the binding force of trypsin-N34S mutant (54.6 pN ± 4.6 pN) complexes. These results are complemented by dynamic force spectroscopy findings which show a higher stability of the wild type SPINK1-trypsin complexes at pH 8.0 in comparison to N34S mutant-trypsin complexes. In addition, the binding profiles for both wild type and N34S mutant SPINK1 to trypsin equalize at pH 4.8.
Our results indicate that the presence of the mutation in the healthy population would most probably not affect the interaction with trypsin at acidic pH such as physiological conditions in pancreatic acinar cells. However, an increase in pH, leads to a difference of binding strength between SPINK1 or N34S mutant towards human cationic trypsin. These findings may be relevant for understanding the role of SPINK1 and its mutation N34S in the pathogenesis of pancreatitis.
In acinar cells, cellular organelles like zymogene granule, mitochondria, endoplasmic reticulum and lysosome functions in coordinate way in order to synthesize and secrets large amounts of digestive enzyme. Dysfunction of this organelle, results into enzyme activation within acinar cell; ultimately, acute pancreatitis. While previous studies reported that mitochondrial function is disrupt but mechanism of clearance of these mitochondria remains unknown during pancreatitis. Here we reported that PINK1 and Parkin mediated pathway is activated during pancreatitis and clears dysfunctional mitochondria in-vivo. PINK1 or Parkin deficient acinar cell had energy crisis, decreased ATP production and altered acinar cell fate in-vitro. Inhibiting clearance of dysfunctional mitochondria aggravates experimental pancreatitis severity and delays regeneration/recovery of exocrine tissue after disease via PARIS-PGC-1α pathway. While an attempt to explore therapeutic target of PARIS-PGC-1α pathway by treatment of SRT1720 rescued experimental pancreatitis. Together, PINK1 and Parkin, restricts exocrine pancreatic damage in pancreatitis and accelerates tissue recovery after disease.