Published online Jan 14, 2019. doi: 10.3748/wjg.v25.i2.205
Peer-review started: October 18, 2018
First decision: November 1, 2018
Revised: November 6, 2018
Accepted: November 16, 2018
Article in press: November 16, 2018
Published online: January 14, 2019
Processing time: 88 Days and 18.6 Hours
Inhibitors of apoptosis proteins (IAPs) are involved in regulating mitosis and inhibiting cells from undergoing apoptosis. They have altered activity in numerous cancer types including pancreatic ductal adenocarcinoma (PDAC) and are implicated in progression of the disease, resistance to chemotherapy, worse outcome and prognosis. Recent research has shown that hyper-expression of mRNA stabilizing protein human antigen R (HuR) increases the stability of IAPs mRNA and determines the increased resistance and vitality of tumor cells. However, epigenetic regulation of IAP and its mechanisms to apoptotic potential and proliferation in pancreatic cancer cells is still unclear. Therefore, we conducted the study to determine the association of HuR mediated regulation and IAP1, IAP2 expression with clinicopathological parameters and prognosis of PDAC. In our study, we report new fundamental knowledge about the direct interaction of RNA stabilizing protein HuR and IAPs. Our results suggest that upregulation of IAP1 in pancreatic cancer is significantly related with poor outcomes. Furthermore, HuR plays important role in post-transcriptional regulation of these molecules: HuR protein binds with IAP1 and IAP2 mRNA and after HuR silencing, expression of IAP1 protein and mRNA is downregulated and IAP2 is upregulated. These results demonstrate for the first time that HuR regulates expression of IAP1 and IAP2 in pancreatic cancer cells and that IAP1 may be an important factor that facilitates carcinogenic properties of HuR.
The idea of the study was to investigate the significance of tumor apoptosis inhibition to prognosis of the disease analyzing interactions between IAPs and HuR and to determine the regulation within pancreatic cancer cells in epigenetic level. These findings lead to a better opportunity to predict the course of disease by choosing more individualized treatment with a specific biological therapy. The identification and analysis of these mechanisms will allow us to better understand the value of tumor’s factors changes in regulation of apoptotic potential in pancreatic cancer.
The main objective of our study was to investigate the importance of dysregulation of pancreatic cancer ‘s apoptotic potential IAPs to the prognosis of the disease. The major driving force of this study was that there is little known about the role of ARE-binding protein HuR in the regulation of IAPs expression and function in pancreatic cancer cells. Therefore, the aim of our study was to assess the relevance of the IAP1 and IAP2 regulation by mRNA stabilizing protein HuR signaling pathway in pancreatic cancer. The identification and analysis of these mechanisms will allow us to better understand the value of tumor’s factors changes in regulation of apoptotic potential in pancreatic cancer. Additionally, these investigated agents (IAPs and HuR) and their interaction could be useful for the future research as possible new therapeutic targets in the treatment of human pancreatic cancer.
For this research project, we have conducted a study that included 61 patients undergoing a partial pancreatodeduodenectomy (Whipple resection) between 2011 - 2016 in the Department of Surgery at the Hospital of the Lithuanian University of Health Sciences for pancreatic cancer. The protein and mRNA expression levels of IAP1, IAP2 and HuR in PDAC were compared with normal pancreatic tissue and correlations with clinicopathological parameters and survival rates were analyzed. Furthermore, in vitro cells culture‘s experiments were performed to check possible epigenetic regulation.
Our results suggest that upregulation of IAP1 in pancreatic cancer is significantly related with poor patient’s outcomes. Furthermore, HuR plays important role in post-transcriptional regulation of these molecules. To our knowledge these results demonstrate for the first time about the direct interaction of RNA stabilizing protein HuR and IAPs in pancreatic cancer cells and that IAP1 may be an important factor that facilitates carcinogenic properties of HuR. Even though, as a part of retrospective analysis of patient’s data we were able to collect over 5 year’s survival rates, relatively small number of patients could act as a limitation of a study. Furthermore, it would be useful to investigate and compare the expression of HuR, IAP1 and IAP2 in PDA tissue obtained both from gemcitabine (GEM) treated and non-treated patients in order to fully understand the underlying mechanism and the role of HuR mediated post-transcriptional regulation for the exceptional resistance of pancreatic cancer to the conventional treatment. Other problems of the study that should be solved in the future studies are unsuccessful immunohistochemistry of IAP1 and IAP2 and that the cell’s transfection experiment should be done in more than 1 pancreatic cancer cell line.
In our presented study, we were able to distinguish that IAP1 and IAP2 are direct targets of HuR. New fundamental knowledge about the direct interaction of RNA stabilizing protein HuR and IAPs was achieved. The results suggest that HuR regulates the expression of IAP1 and IAP2 in pancreatic cancer cells and that IAP1 may be one of the important factors that facilitate the carcinogenic properties of HuR. Moreover, upregulation of IAP1 in pancreatic cancer is significantly related with poor outcome. Additionally, these investigated agents (IAPs and HuR) and their interaction could be useful for the future research as possible new therapeutic targets in the treatment of human pancreatic cancer.
We have to acknowledge that this study showed the importance of dysregulation of pancreatic cancer apoptotic potential to the prognosis of the disease. However, further research is needed to analyze the mechanism of response to chemotherapy treatment in the pancreatic cancer cell lines and in vitro underlying HuR and IAPs interaction. Furthermore, it would be useful to investigate and compare the expression of HuR, IAP1 and IAP2 in PDAC tissue obtained both from GEM treated and non-treated patients and cell’s transfection experiments in order to fully understand the underlying mechanism and the role of HuR mediated post-transcriptional regulation for the exceptional resistance of pancreatic cancer to the conventional treatment.