Synergistic Carcinogenesis of HPV18 and MNNG in Het-1A Cells through p62-KEAP1-NRF2 and PI3K/AKT/mTOR Pathway

A critical review of advances in tumor metabolism abnormalities induced by nitrosamine disinfection by-products in drinking water

Intensified sanitation practices amid the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak might result in the increased release of chloramine disinfectants into surface water, significantly promoting the formation of nitrosamine disinfection by-products (DBPs) in drinking water. Unfortunately, these nitrosamine DBPs exhibit significant genotoxic, carcinogenic, and mutagenic properties, whereas chlorinating disinfectants remain in global practice. The current review provides valuable insights into the occurrence, identification, contamination status, exposure limits, and toxicity of the new unregulated disinfection by-products (nitrosamine DBPs) in drinking water. As a result, concentrations of nitrosamine DBPs far exceed allowable limits in drinking water, and prolonged exposure has the potential to cause metabolic disorders, a critical step in tumor initiation and progression. Importantly, based on recent research, we have concluded the role of nitrosamines DBPs in different metabolic pathways. Remarkably, nitrosamine DBPs can induce chronic inflammation and initiate tumors by activating sphingolipid and polyunsaturated fatty acid metabolism. Regarding amino acid and nucleotide metabolism, nitrosamine DBPs can inhibit tryptophan metabolism and de novo nucleotide synthesis. Moreover, inhibition of de novo nucleotide synthesis fails to repair DNA damage induced by nitrosamines. Additionally, the accumulation of lactate induced by nitrosamine DBPs may act as a pivotal signaling molecule in communication within the tumor microenvironment. However, with the advancement of tumor metabolomics, understanding the role of nitrosamine DBPs in causing cancer by inducing metabolic abnormalities significantly lags behind, and specific mechanisms of toxic effects are not clearly defined. Urgently, further studies exploring this promising area are needed.

RAE1 promotes nitrosamine-induced malignant transformation of human esophageal epithelial cells through PPARα-mediated lipid metabolism

Esophageal cancer (EC) is the sixth cause of cancer-related deaths and still is a significant public health problem globally. Nitrosamines exposure represents a major health concern increasing EC risks. Exploring the mechanisms induced by nitrosamines may contribute to the prevention and early detection of EC. However, the mechanism of nitrosamine carcinogenesis remains unclear. Ribonucleic acid export 1 (RAE1), has an important role in mediating diverse cancer types, but, to date, there has been no study for any functional role of RAE1 in esophageal carcinogenesis. Here, we successfully verified the nitrosamine-induced malignant transformation cell (MNNG-M) by xenograft tumor model, based on which it was found that RAE1 was upregulation in the early stage of nitrosamine-induced esophageal carcinogenesis and EC tissues. RAE1 knockdown led to severe blockade in G2/M phase and significant inhibition of proliferation of MNNG-M cells, whereas RAE1 overexpression had the opposite effect. In addition, peroxisome proliferator-activated receptor-alpha (PPARα), was demonstrated as a downstream target gene of RAE1, and its down-regulation reduced lipid accumulation, resulting in causing cells accumulation in the G2/M phase. Mechanistically, we found that RAE1 regulates the lipid metabolism by maintaining the stability of PPARα mRNA. Taken together, our study reveals that RAE1 promotes malignant transformation of human esophageal epithelial cells (Het-1A) by regulating PPARα-mediated lipid metabolism to affect cell cycle progression, and offers a new explanation of the mechanisms underlying esophageal carcinogenesis.

Synergistic effects of low-dose arsenic and N-methyl-N'-nitro-N-nitrosoguanidine co-exposure by altering gut microbiota and intestinal metabolic profile in rats

Biological organisms are exposed to low-dose arsenic or N-nitro compounds (NOCs) alone or in combination worldwide, especially in areas with high cancer prevalence through drinking water or food exposure; however, information on their combined exposure effects is limited. Here, we conducted an in-depth study of the effects on the gut microbiota, metabolomics, and signaling pathways using rat models exposed to arsenic or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), one of the most active carcinogenic NOCs, separately or in combination with metabolomics and high-throughput sequencing. Compared to exposure alone, combined exposure to arsenic and MNNG exacerbated damage to gastric tissue morphology, interfered with intestinal microflora and substance metabolism, and exerted a stronger carcinogenic effect. This may be related to intestinal microbiota disorders, including Dyella, Oscillibacter, Myroides, and metabolic pathways such as glycine, serine, and threonine metabolism, arginine biosynthesis, central carbon metabolism in cancer, and purine and pyrimidine metabolism, thereby enhancing the cancer-causing effects of gonadotrophin-releasing hormone (GnRH), P53, and Wnt signaling pathways.

Formononetin ameliorates ferroptosis-associated fibrosis in renal tubular epithelial cells and in mice with chronic kidney disease by suppressing the Smad3/ATF3/SLC7A11 signaling

AIMS

Chronic kidney disease (CKD) is characterized by interstitial fibrosis, while limited treatment drugs are available. Ferroptosis is a newly identified process that can trigger tubular atrophy and fibrosis. The aim of this study is to investigate the effects of formononetin (FN), a bioflavonoid, on ferroptosis and renal fibrosis.

MAIN METHODS

In vivo experiments, unilateral ureteral obstruction (UUO)- and folic acid (FA, 250 mg/kg)-induced CKD models were constructed in C57BL/6 mice of 6-8 weeks old, followed by the administration with 40 mg/kg/day FN by gavage. For in vitro experiments, ferroptosis was induced with RSL3 or erastin in primary mouse renal tubular epithelial cells (TECs), followed by the addition of indicated concentrations of FN. Then, the levels of ferroptosis and fibrosis were analyzed. The translocation of Smad3, ATF3, and Nrf2 from the cytoplasm to the nucleus was checked by western blotting. The interaction of Smad3 and ATF3 was detected by Co-immunoprecipitation.

KEY FINDINGS

FN dramatically ameliorated tubular injury along with reduced expression of the profibrotic genes including α-SMA, Col1a1, and fibronectin in both two CKD mouse models and RSL3/erastin-treated TECs. Furthermore, FN administration also significantly suppressed ferroptosis, as evidenced by increased expression of SLC7A11 and GPX4, and decreased levels of 4-HNE. In mechanism, FN disrupted the interaction between Smad3 and ATF3, resulting in the blocking of their translocation from the cytoplasm to the nucleus. In addition, FN also promoted the separation of the Nrf2/Keap1 complex and enhanced Nrf2 nuclear accumulation.

SIGNIFICANCE

FN alleviates CKD by impeding ferroptosis-associated fibrosis by suppressing the Smad3/ATF3/SLC7A11 signaling and could serve as a candidate therapeutic drug for CKD.

Hesperidin Reversed Long-Term N-methyl-N-nitro-N-Nitroguanidine Exposure Induced EMT and Cell Proliferation by Activating Autophagy in Gastric Tissues of Rats

Gastric cancer is a common malignant tumor worldwide. N-methyl-N-nitro-N-nitroguanidine (MNNG) is one of the most important inducing factors of gastric cancer. Autophagy can affect the occurrence and development of gastric cancer, but the mechanism is not clear. Chemoprevention has been shown to be a rational and very promising approach to the prevention of gastric cancer. Hesperidin is a citrus flavone, an abundant polyphenol in citrus fruits and traditional Chinese medicine. It has an excellent phytochemistry that plays an intervention role in gastric cancer. However, it is unclear whether long-term exposure to MNNG will affect the occurrence of gastric cancer by regulating autophagy and whether hesperidin can play an intervention role in this process. In the present study, we demonstrated that long-term MNNG exposure inhibits autophagy in stomach tissues of rats, promotes the epithelial-mesenchymal transition (EMT) process and cell proliferation and suppresses the activity of the PI3K/AKT pathway. We further found that after rapamycin-activated autophagy, long-term MNNG exposure promoted cell proliferation and EMT were inhibited. In addition, hesperidin promotes autophagy and the activity of the PI3K/AKT pathway, as well as the suppression of proliferation and EMT in the stomach tissues of rats. Our findings indicate that hesperidin reverses MNNG-induced gastric cancer by activating autophagy and the PI3K/AKT pathway, which may provide a new basis for the early prevention and treatment of MNNG-induced gastric cancer.

[Progress of NRF2 Signaling Pathway in Promoting Proliferation of Non-small Cell Lung Cancer]

The morbidity and mortality of lung cancer ranks among the top cancers in the world. Non-small cell lung cancer (NSCLC) is the main pathological type of lung cancer, with limited treatment options and poor prognosis. The nuclear factor E2-related factor 2 (NRF2) signaling pathway is highly mutated and activated in NSCLC, and promotes the malignant progression of lung cancer through various mechanisms. NRF2-targeted therapy will provide new treatment strategies for patients with NSCLC. This article will review the basic structure and response pathways of the NRF2 pathway, the mechanism of NRF2 regulating lung cancer cell proliferation, and the research and development progress of NRF2 inhibitors.
.

Overcoming therapeutic resistance to platinum-based drugs by targeting Epithelial–Mesenchymal transition

Platinum-based drugs (PBDs), including cisplatin, carboplatin, and oxaliplatin, have been widely used in clinical practice as mainstay treatments for various types of cancer. Although there is firm evidence of notable achievements with PBDs in the management of cancers, the acquisition of resistance to these agents is still a major challenge to efforts at cure. The introduction of the epithelial-mesenchymal transition (EMT) concept, a critical process during embryonic morphogenesis and carcinoma progression, has offered a mechanistic explanation for the phenotypic switch of cancer cells upon PBD exposure. Accumulating evidence has suggested that carcinoma cells can enter a resistant state via induction of the EMT. In this review, we discussed the underlying mechanism of PBD-induced EMT and the current understanding of its role in cancer drug resistance, with emphasis on how this novel knowledge can be exploited to overcome PBD resistance via EMT-targeted compounds, especially those under clinical trials.

The dysregulation of unsaturated fatty acid-based metabolomics in the MNNG-induced malignant transformation of Het-1A cells

Studies have shown that environmental carcinogens exerted an important function in the high incidence of esophageal cancer (EC). Nitrosamines have been identified as important environmental carcinogens for EC. This study aimed to investigate the metabolic disturbances and new key toxicological markers in the malignant transformation process of normal esophageal epithelial cells (Het-1A) induced by MNNG (N-methyl-N'-nitro-N-nitrosoguanidine). Untargeted metabolomic and lipidomic profiling analysis by using ultra-high-performance liquid chromatography coupled with mass spectrometry (UHPLC-MS) were applied to explore the metabolic network alterations of Het-1A cells. The metabolomic results showed that significant alterations were observed in metabolic signatures between different generations (P5, P15, P25, P35) and the control cell group (P0). A total of 48 differential endogenous metabolites were screened and identified, mainly containing fatty acids, amino acids, and nucleotides. The differential metabolites were predominantly linked to the pathway of biosynthesis of unsaturated fatty acids metabolism. The cell lipidomic profiling revealed that the most differential lipids contained fatty acids (FAs), phosphatidylcholines (PC), phosphatidylethanolamines (PE), and phosphatidylserines (PS). The enrichment of the lipidomic pathway also confirmed that the lipid metabolism of biosynthesis of unsaturated fatty acids was the significant variation during the cell malignant transformation. Furthermore, we detected the expression of the upstream regulatory enzymes related to the unsaturated fatty acids to explore the regulation mechanism. The expression of stearoyl-CoA desaturase (SCD), ELOVL fatty acid elongase 1 (ELOVL1) promoted, and fatty acid desaturase 1 (FADS1) inhibited the key fatty acids of unsaturated fatty acids metabolism compared to the control cell group. Overall, our results revealed that lipid fatty acid metabolism was involved in the malignant transformation of Het-1A cells induced by MNNG and deepened the awareness of the carcinogenic mechanism of environmental exposure pollutants.

Nuclear factor erythroid 2-related factor 2 in human papillomavirus-related cancers

High-risk human papillomavirus (HR-HPV) infection is a necessary cause for the development of cervical cancer. Moreover, HR-HPV is also associated with cancers in the anus, vagina, vulva, penis and oropharynx. HR-HPVs target and modify the function of different cell biomolecules, such as glucose, amino acids, lipids and transcription factors (TF), such as p53, nuclear factor erythroid 2-related factor 2 (Nrf2), among others. The latter is a master TF that maintains redox homeostasis. Nrf2 also induces the transcription of genes associated with cell detoxification. Since both processes are critical for cell physiology, Nrf2 deregulation is associated with cancer development. Nrf2 is a crucial molecule in HPV-related cancer development but underexplored. Moreover, Nrf2 activation is also associated with resistance to chemotherapy and radiotherapy in these cancers. This review focusses on the importance of Nrf2 during HPV-related cancer development, resistance to therapy and potential therapies associated with Nrf2 as a molecular target.