Junyu Cao

Metformin suppresses cancer initiation and progression in genetic mouse models of pancreatic cancer

BackgroundPancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-associated mortality worldwide with an overall five-year survival rate less than 7%. Accumulating evidence has revealed the cancer preventive and therapeutic effects of metformin, one of the most widely prescribed medications for type 2 diabetes mellitus. However, its role in pancreatic cancer is not fully elucidated. Herein, we aimed to further study the preventive and therapeutic effects of metformin in genetically engineered mouse models of pancreatic cancer.MethodsLSL-KrasG12D/+; Pdx1-Cre (KC) mouse model was established to investigate the effect of metformin in pancreatic tumorigenesis suppression; LSL-KrasG12D/+; Trp53fl/+; Pdx1-Cre (KPC) mouse model was used to evaluate the therapeutic efficiency of metformin in PDAC. Chronic pancreatitis was induced in KC mice by peritoneal injection of cerulein.ResultsFollowing metformin treatment, pancreatic acinar-to-ductal metaplasia (ADM) and mouse pancreatic intraepithelial neoplasia (mPanIN) were decreased in KC mice. Chronic pancreatitis induced a stroma-rich and duct-like structure and increased the formation of ADM and mPanIN lesions, in line with an increased cytokeratin 19 (CK19)-stained area. Metformin treatment diminished chronic pancreatitis-mediated ADM and mPanIN formation. In addition, it alleviated the percent area of Masson’s trichrome staining, and decreased the number of Ki67-positive cells. In KPC mice, metformin inhibited tumor growth and the incidence of abdominal invasion. More importantly, it prolonged the overall survival.ConclusionsMetformin inhibited pancreatic cancer initiation, suppressed chronic pancreatitis-induced tumorigenesis, and showed promising therapeutic effect in PDAC.

Resveratrol and cancer treatment: updates

Cancer, a growing health problem worldwide, affects millions of people every year. The overall survival rates of most cancers have been prolonged owing to the efforts of clinicians and scientists. However, some tumors develop resistance to chemoradiotherapeutic agents, and the cancer research community continues to search for effective sensitizers. Resveratrol, a natural polyphenolic phytoalexin, has shown promising effects in inhibiting proliferation and cancer progression in several tumor models. However, its molecular mechanisms and applications in chemotherapy and radiotherapy have yet to be fully determined. In this concise review, we highlight the role and related molecular mechanisms of resveratrol in cancer treatment. In particular, we focus on the role of resveratrol in the tumor microenvironment and the sensitization of cancer cells for chemotherapy and radiotherapy. Resveratrol shows promising efficacies in cancer treatment and may be applied in clinical therapy, but it requires further clinical study.

Loss of AMPK activation promotes the invasion and metastasis of pancreatic cancer through an HSF1‐dependent pathway

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy with a mortality rate that closely parallels its incidence rate, and a better understanding of the molecular and cellular mechanisms associated with the invasion and distant metastasis is required. Heat shock factor 1 (HSF1) is a very highly conserved factor in eukaryotes that regulates the protective heat shock response. Here, we show that HSF1 is abnormally activated in pancreatic cancer. The knockdown of HSF1 impaired the invasion and migration and epithelial–mesenchymal transition (EMT) of pancreatic cancer cells in vitro; however, the upregulation of HSF1 showed the opposite effects. In vivo, the pharmacological inhibition of HSF1 significantly reduced the tumor burden, decreased the incidence of invasion, and prolonged the overall survival of transgenic mice harboring the spontaneous pancreatic cancer. We suggest that the loss of AMP‐activated protein kinase (AMPK) activation mediates the abnormal activation of HSF1 based on the findings that phospho‐HSF1 (p‐HSF1) was highly expressed in human PDAC tissues with a low expression of p‐AMPK and that in those tissues with a high p‐AMPK expression, the level of p‐HSF1 was decreased. The in vivo and in vitro activation of AMPK impaired the activity of HSF1, and HSF1 mediated the effects of the AMPK knockdown‐induced pancreatic cancer invasion and migration. Our study revealed a novel mechanism by which the loss of AMPK activation amplifies the activity of HSF1 to promote the invasion and metastasis of pancreatic cancer.

Resveratrol-Induced Downregulation of NAF-1 Enhances the Sensitivity of Pancreatic Cancer Cells to Gemcitabine via the ROS/Nrf2 Signaling Pathways

NAF-1 (nutrient-deprivation autophagy factor-1), which is an outer mitochondrial membrane protein, is known to play important roles in calcium metabolism, antiapoptosis, and antiautophagy. Resveratrol, a natural polyphenolic compound, is considered as a potent anticancer agent. Nevertheless, the molecular mechanisms underlying the effects of resveratrol and NAF-1 and their mediation of drug resistance in pancreatic cancer remain unclear. Here, we demonstrate that resveratrol suppresses the expression of NAF-1 in pancreatic cancer cells by inducing cellular reactive oxygen species (ROS) accumulation and activating Nrf2 signaling. In addition, the knockdown of NAF-1 activates apoptosis and impedes the proliferation of pancreatic cancer cells. More importantly, the targeting of NAF-1 by resveratrol can improve the sensitivity of pancreatic cancer cells to gemcitabine. These results highlight the significance of strategies that target NAF-1, which may enhance the efficacy of gemcitabine in pancreatic cancer therapy.

Resveratrol Inhibits ROS-Promoted Activation and Glycolysis of Pancreatic Stellate Cells via Suppression of miR-21

Activation of pancreatic stellate cells (PSCs) initiates pancreatic fibrosis in chronic pancreatitis and furnishes a niche that enhances the malignancy of pancreatic cancer cells (PCCs) in pancreatic ductal adenocarcinoma (PDAC). Resveratrol (RSV), a natural polyphenol, exhibits potent antioxidant and anticancer effects. However, whether and how RSV influences the biological properties of activated PSCs and the effects of these changes on tumor remain unknown. In the present study, we found that RSV impeded hydrogen peroxide-driven reactive oxygen species- (ROS-) induced activation, invasion, migration, and glycolysis of PSCs. In addition, miR-21 expression in activated PSCs was downregulated after RSV treatment, whereas the PTEN protein level increased. miR-21 silencing attenuated ROS-induced activation, invasion, migration, and glycolysis of PSCs, whereas the overexpression of miR-21 rescued the responses of PSCs treated with RSV. Moreover, RSV or N-acetyl-L-cysteine (NAC) administration or miR-21 knockdown in PSCs reduced the invasion and migration of PCCs in coculture, and the effects of RSV were partly reversed by miR-21 upregulation. Collectively, RSV inhibits PCC invasion and migration through suppression of ROS/miR-21-mediated activation and glycolysis in PSCs. Therefore, targeting miR-21-mediated glycolysis by RSV in tumor stroma may serve as a new strategy for clinical PDAC prevention or treatment.

Norepinephrine enhances cell viability and invasion, and inhibits apoptosis of pancreatic cancer cells in a Notch‑1‑dependent manner

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive types of cancer, which is associated with a poor prognosis due to complexities in prevention, early diagnosis and effective treatment. The lack of understanding regarding its induction and specific pro‑cancer mechanisms may contribute to its poor prognosis. The Notch‑1 pathway is widely considered to be a critical tumor‑promoting factor in PDAC. Previous studies have indicated that chronic psychological stress may promote the development of PDAC partially via the main downstream stress hormone, norepinephrine (NE); however, to the best of our knowledge, the role of the Notch‑1 pathway in this process has not been studied. Therefore, the present study aimed to explore this process. The expression levels of Notch‑1 pathway‑associated molecules were measured in response to NE using reverse transcription‑quantitative polymerase chain reaction and western blotting. Alongside NE treatment, two Notch‑1 pathway blockers, Notch‑1‑specific small interfering (si)RNA and DAPT (an inhibitor of the Notch‑1 pathway), were used to explore the relationship between NE and the Notch‑1 pathway in the development of pancreatic cell malignant biological behaviors, including cell viability, apoptosis and cell invasion. The results demonstrated that treatment with NE enhanced cell viability and invasion, and inhibited apoptosis of PDAC cells; however, these effects were suppressed following treatment with Notch‑1‑specific siRNA and DAPT. In conclusion, NE may enhance the malignant biological behaviors of PDAC via activating the Notch‑1 pathway.

Metformin suppresses the invasive ability of pancreatic cancer cells by blocking autocrine TGF‑β1 signaling

Pancreatic ductal adenocarcinoma (PDAC) is a highly invasive neoplasm with a 5‑year survival rate of <8%. Metformin, the most widely used antidiabetic drug in the world, has been shown to exert anticancer activities in epidemiological and animal studies. Our previous studies revealed that metformin suppressed desmoplasia in PDAC by reducing TGF‑β1 production in cancer cells. The aim of the present study was to investigate the effects of metformin on invasion and epithelial‑mesenchymal transition (EMT) in pancreatic cancer and to reveal the underlying mechanisms. In the present study, we revealed that metformin suppressed migration, invasion and EMT changes in pancreatic cancer cells. Furthermore, metformin reduced TGF‑β1 production and Smad2/3 phosphorylation in pancreatic cancer cells. In addition, treatment with recombinant TGF‑β1 recovered the metformin‑mediated invasion inhibition and EMT changes. Treatment with metformin also suppressed tumor growth, invasion and EMT in LSL‑KrasG12D/+, Trp53fl/+and Pdx1‑Cre (KPC) transgenic mice that harbor spontaneous pancreatic cancer. Collectively, our study revealed a new possible mechanism for the antitumor effects of metformin via autocrine TGF‑β1/Smad2/3 signaling in PDAC.

A novel three‑miRNA signature predicts survival in cholangiocarcinoma based on RNA‑Seq data

Accumulating evidence illustrates that many microRNAs (miRNAs) are abnormally expressed in cholangiocarcinoma and play important roles in tumorigenesis, tumor progression and metastasis. These miRNAs may serve as prognostic biomarkers and potential therapeutic targets. The aim of the present study was to identify the differentially expressed miRNAs in cholangiocarcinoma tissues vs. normal tissues by analyzing high‑throughput data derived from The Cancer Genome Atlas (TCGA) database. Furthermore, we evaluated the prognostic performance of the differentially expressed miRNAs and developed a novel three‑miRNA signature which predicted survival in cholangiocarcinoma patients. According to the cut‑off criteria of P<0.01 and |log2FC|>1.0, a total of 100xa0miRNAs (54xa0upregulated and 46xa0downregulated) were found to be differentially expressed and some of them were significantly associated with clinical features. Of the above 100xa0miRNAs, we obtained three miRNAs (miR‑10b, miR‑22 and miR‑551b) which were markedly related to patient overall survival (OS). Subsequently, a novel three‑miRNA signature was established and validated to be effective to predict survival. The results demonstrated that the survival rate, as well as the survival time of patients were obviously enhanced in relation to a lower miRNA signature index. Univariate and multivariate Cox regression analyses revealed that the three‑miRNA signature was an independent prognostic factor in cholangiocarcinoma. The reliability of the three‑miRNA signature was validated by an independent cohort from Gene Expression Omnibus (GEO). Furthermore, the functional enrichment analysis emphasized that the target genes of the aforementioned miRNAs may be involved in a variety of pathways and processes associated with cancer. Finally, these three miRNAs were detected for verification of expression using RT‑qPCR, and miR‑551b was selected for the verification of biological functions in cholangiocarcinoma cells. The results revealed that overexpression of miR‑551b decreased cancer cell proliferation and promoted apoptosis. Collectively, the results of the present study indicated that a specific three‑miRNA signature could be considered as an alternative prognostic marker in cholangiocarcinoma.

Hypoxia-driven paracrine osteopontin/integrin αvβ3 signaling promotes pancreatic cancer cell epithelial-mesenchymal transition and cancer stem cell-like properties by modulating FOXM1

Pancreatic stellate cells (PSCs), a key component of the tumor microenvironment, contribute to tumor invasion, metastasis, and chemoresistance. Osteopontin (OPN), a phosphorylated glycoprotein, is overexpressed in pancreatic cancer. However, OPN expression in PSCs and its potential roles in tumor–stroma interactions remain unclear. The present study first showed that OPN is highly expressed and secreted in activated PSCs driven by hypoxia, and this process is in a ROS‐dependent manner; in addition, OPN was shown to be involved in the PSC‐induced epithelial–mesenchymal transition (EMT) and cancer stem cell (CSC)‐like properties of pancreatic cancer cells (PCCs). Mechanistically, OPN from activated PSCs interacts with the transmembrane receptor integrin αvβ3 on PCCs to upregulate forkhead box protein M1 (FOXM1) expression and induce malignant phenotypes of PCCs. Moreover, the Akt and Erk pathways participate in OPN/integrin αvβ3 axis‐induced FOXM1 expression of PCCs. Our further analysis showed that OPN and FOXM1 are significantly upregulated in pancreatic cancer tissues and are associated with poor clinical outcome, indicating that OPN and FOXM1 might be considered as diagnostic and prognostic biomarkers for patients with pancreatic cancer. In conclusion, we show here for the first time that OPN promotes the EMT and CSC‐like properties of PCCs by activating the integrin αvβ3‐Akt/Erk‐FOXM1 cascade in a paracrine manner, suggesting that targeting the tumor microenvironment represents a promising therapeutic strategy in pancreatic cancer.

Metformin suppresses tumor angiogenesis and enhances the chemosensitivity of gemcitabine in a genetically engineered mouse model of pancreatic cancer

Aims: Pancreatic ductal adenocarcinoma (PDAC) is one of the most malignant diseases and has few effective and reliable therapeutic strategies. The anti‐tumor effect of metformin is widely known, however, there is only limited evidence regarding the anti‐angiogenesis effect and chemosensitization of metformin and its underlying mechanisms in PDAC. Main methods: In the present study, we adopted a spontaneous PDAC mouse model named LSL‐KrasG12D/+; Trp53fl/+; Pdx1‐Cre (KPC) mice to explore the mechanism of the modulation of tumor angiogenesis and chemosensitization of metformin by treating KPC mice with metformin, gemcitabine or a combination of the two. H&E staining, Masson staining and immunohistochemical staining were adopted to describe the histopathology and biomarkers of the KPC in different groups. Key findings: Metformin plus gemcitabine reduced tumorigenic potential of PDAC. Specifically, metformin showed an anti‐pancreatic stellate cells (PSCs) effect via decreasing the expression of sonic hedgehog (SHH) and then sparked some downstream effects, for example, inhibiting the production of vascular endothelial growth factor (VEGF) in the tumor microenvironment, reducing the formation of tumor neovascularization, attenuating the desmoplastic reaction and enhancing the antitumor effect of gemcitabine. Significance: We concluded that metformin suppressed tumor angiogenesis and enhanced the chemosensitivity of gemcitabine via inactivating PSCs in PDAC of KPC mice.