Jiahui Li

Overview of Emerging Contaminants and Associated Human Health Effects

In recent decades, because of significant progress in the analysis and detection of trace pollutants, emerging contaminants have been discovered and quantified in living beings and diverse environmental substances; however, the adverse effects of environmental exposure on the general population are largely unknown. This review summarizes the conclusions of the comprehensive epidemic literature and representative case reports relevant to emerging contaminants and the human body to address concerns about potential harmful health effects in the general population. The most prevalent emerging contaminants include perfluorinated compounds, water disinfection byproducts, gasoline additives, manufactured nanomaterials, human and veterinary pharmaceuticals, and UV-filters. Rare but statistically meaningful connections have been reported for a number of contaminants and cancer and reproductive risks. Because of contradictions in the outcomes of some investigations and the limited number of articles, no significant conclusions regarding the relationship between adverse effects on humans and extents of exposure can be drawn at this time. Here, we report that the current evidence is not conclusive and comprehensive and suggest prospective cohort studies in the future to evaluate the associations between human health outcomes and emerging environmental contaminants.

Reactive Oxygen Species and Targeted Therapy for Pancreatic Cancer

Pancreatic cancer is the fourth leading cause of cancer-related death in the United States. Reactive oxygen species (ROS) are generally increased in pancreatic cancer cells compared with normal cells. ROS plays a vital role in various cellular biological activities including proliferation, growth, apoptosis, and invasion. Besides, ROS participates in tumor microenvironment orchestration. The role of ROS is a doubled-edged sword in pancreatic cancer. The dual roles of ROS depend on the concentration. ROS facilitates carcinogenesis and cancer progression with mild-to-moderate elevated levels, while excessive ROS damages cancer cells dramatically and leads to cell death. Based on the recent knowledge, either promoting ROS generation to increase the concentration of ROS with extremely high levels or enhancing ROS scavenging ability to decrease ROS levels may benefit the treatment of pancreatic cancer. However, when faced with oxidative stress, the antioxidant programs of cancer cells have been activated to help cancer cells to survive in the adverse condition. Furthermore, ROS signaling and antioxidant programs play the vital roles in the progression of pancreatic cancer and in the response to cancer treatment. Eventually, it may be the novel target for various strategies and drugs to modulate ROS levels in pancreatic cancer therapy.

Resveratrol in the treatment of pancreatic cancer

Pancreatic cancer (PCa), which is now the fourth most frequent cause of cancer‐related death, has a median survival of less than 6 months and a 5‐year survival rate of <6%. The hallmarks of this cancer include poor outcome, short survival duration, and resistance to therapy. The poor prognosis of PCa is related to its local recurrence, lymph node and liver metastases, and peritoneal dissemination. Recent studies have indicated that resveratrol has cancer‐chemopreventive and anticancer activities. In this short review we summarize the chemopreventive and treatment effects of resveratrol in PCa, as follows: resveratrol inhibits the proliferation of pancreatic cancer cells; induces apoptosis and cell cycle arrest; inhibits metastasis and invasion of PCa cells; inhibits the proliferation and viability of PCa stem cells; enhances the chemoradiosensitization of PCa cells; and can affect diabetes mellitus in addition to PCa. On the basis of these data, resveratrol may be considered a potential anticancer agent for the treatment of PCa.

Lipoxin A4 Attenuates Cell Invasion by Inhibiting ROS/ERK/MMP Pathway in Pancreatic Cancer.

Lipoxin A4 (LXA4), an endogenous arachidonic acid metabolite, was previously considered an anti-inflammatory lipid mediator. But it also has the potential to inhibit cancer progression. To explore the therapeutic effect of LXA4 in pancreatic cancer, we used Panc-1 cells to investigate the mechanism by which LXA4 can attenuate pancreatic cancer cell invasion. Our data showed that LXA4 significantly inhibited both cell invasion and the expression of matrix metalloproteinase- (MMP-) 9 and MMP-2. Further experiments implied that LXA4 decreased the levels of intracellular reactive oxygen species (ROS) and the activity of the extracellular signal regulated kinases (ERK) pathway to achieve similar outcome to ROS scavenger N-acetyl-l-cysteine (NAC). However, a decreased level of intracellular ROS was not observed in cells treated with the specific ERK pathway inhibitor FR180204. The blocking of either intracellular ROS or ERK pathway caused the downregulation of MMP-9 and MMP-2 expression. Furthermore, tests revealed that LXA4 inhibited MMP-9 and MMP-2 at the mRNA, protein, and functional levels. Finally, LXA4 dramatically limited the invasion of CoCl2-mimic hypoxic cells and abrogated intracellular ROS levels, ERK activity, and MMPs expression. These results suggest that LXA4 attenuates cell invasion in pancreatic cancer by suppressing the ROS/ERK/MMPs pathway, which may be beneficial for preventing the invasion of pancreatic cancer.

The Relevance of Nrf2 Pathway and Autophagy in Pancreatic Cancer Cells upon Stimulation of Reactive Oxygen Species

Nrf2 (NF-E2-related factor 2) pathway and autophagy both can respond to oxidative stress to promote cancer cells to survive in the tumor microenvironment. We, therefore, explored the relevance between Nrf2 pathway and autophagy in pancreatic cancer cells upon stimulation of reactive oxygen species (ROS). Pancreatic cancer cells were cultured under controlled ROS stressing condition or basal condition. Different inhibitors were used to prevent autophagy at particular stages. Nrf2 siRNA was used to inhibit Nrf2 pathway activation. Ad-mRFP-GFP-LC3 infection was used to monitor autophagic flux. The result shows that a small amount of exogenous hydrogen peroxide (H2O2) can significantly improve the level of intracellular ROS. Moreover, our findings indicate that ROS promotes the activation of both Nrf2 pathway and autophagy in pancreatic cancer cells. Moreover, our data demonstrate that suppression of autophagic activity at particular stages results in an increased promotion of Nrf2 pathway activation upon ROS stimulation. Furthermore, we found that silencing of Nrf2 promotes autophagy upon ROS stimulation. In addition, Nrf2 interference effectively promotes autophagic flux upon ROS stimulation. In summary, our findings suggest that Nrf2 pathway and autophagy have a negative interaction with each other upon ROS stimulation.

Disrupting the Balance between Tumor Epithelia and Stroma is a Possible Therapeutic Approach for Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a type of highly lethal malignant tumor. PDAC is locally invasive and is surrounded by a dense desmoplasia or fibrosis, which can involve adjacent vital structures. Previously, the effect of pancreatic stellate cells (PSCs) of stroma in the progression of PDAC has received more attention, and most in vitro and in vivo studies revealed that PSCs appear to confer biological aggressiveness. However, clinical trials targeting desmoplasia or PSCs showed disappointing results. Recent studies found that stromal components, especially activated PSCs, are able to inhibit the occurrence and progression of PDAC. Inhibition of the stroma or desmoplasia through genetic regulations or drugs accelerates the formation and progression of PDAC. Thus, we hypothesized that in various times and spaces, there is a balance between the tumor epithelia and stroma; once the balance is upset, the tumor traits may undergo certain changes. Therefore, finding the key changing points of this relationship to corrupt or influence it, instead of blindly inhibiting the stroma motivation or simply maintaining stroma activation, will destroy the cooperation or promote the competition and antagonism among cells. This approach may render tumors more vulnerable and thus unable to resist anti-cancer therapies.

Pancreatic carcinoma-specific immunotherapy using novel tumor specific cytotoxic T cells

Pancreatic cancer represents one of the most lethal human cancers. Investigation of the effective targeting to the tumor cells is essential for both primary tumors and metastases. Tumor specific cytotoxic T lymphocytes (CTLs) have recently been considered to be the attractive vehicles for delivering therapeutic agents toward various tumor diseases. This study was to explore the distribution pattern of CTL carrying the lentiviral vectors with the characteristic of adenoviral E1 gene under the control of the cell activation-dependent CD40 ligand promoter (Lenti/hCD40L/E1AB). Following transduction with adenoviral particles containing chimeric type 5 and type 35 fiber proteins (Ad5/35-TRAIL), these CTLs produced infectious virus when exposed to SW1990 cells. We found that the novel CTL harboring Lenti/hCD40L/E1AB and Ad5/35-TRAIL inhibited pancreatic cancer cell growth and angiogenesis in vitro and in vivo. Furthermore, Ad5/35-TRAIL transduced CTL induced significant apoptosis in pancreatic carcinoma cell lines and upregulated IFN-gamma (IFN-γ) secretion of CTLs. Importantly, Ad5/35-TRAIL transduced CTLs had no inhibitory effect on normal cells. Thus, the novel CTLs may be safe and feasible for the development of gene therapy approaches to pancreatic carcinoma.