Tumor hypoxia may compromise the results of chemotherapy for treating colorectal cancer because it stimulates angiogenesis and the release of tumor growth factors. Hyperbaric oxygen (HBO) supplementation may potentiate the effects of chemotherapy in such cases. This study aimed to assess the effect of HBO therapy combined with chemotherapy on the treatment of colorectal cancer in mice. C57BL6 mice were submitted to the intrarectal instillation of N-methyl-N-nitrosoguanidine (MNNG) and treated with 5-fluorouracil (5FU) and/or HBO therapy. The MNNG group presented the highest dysplastic crypt rate. The 5FU + HBO group presented the highest rate of apoptotic cells per dysplastic crypt. The 5FU group presented the highest expression of hypoxia-inducible factor-1 alpha and CD44. HBO therapy increased the effect of 5FU on the treatment of the experimental colorectal neoplasia in mice.

BACKGROUND: Gastric cancer (GC) is a frequent malignant neoplasm found in China. Despite numerous therapeutic methodologies to ameliorate the well-being of GC patients, their efficiency remains inadequate.
OBJECTIVE: Rosmanol (RML) is a phenolic diterpene compound with antioxidant and anticancer activities. In the current research, the apoptotic efficacy of RML on methylnitronitrosoguanidine (MNNG)-induced GC model was determined.
METHODS: The rats were allocated into four sets, viz., normal control, MNNG (200 mg/kg bw) + NaCl, MNNG + RML (20 mg/kg), and RML (20 mg/kg) orally treated for 20 weeks.
RESULTS: The results exposed that GC rats revealed higher (P<0.05) levels of TBARS and reduced antioxidant status in the stomach and liver tissues counter to other groups. In contrast, the TBARS level was substantially alleviated (P<0.05) and restored the antioxidant status in RMLadministered rats. Histopathologic assessment of gastric tissue unveiled that an MNNG-induced group presented squamous cell carcinoma with keratin pearls. The administration of RML reduced GC incidence, and only mild dysplasia was observed. Further, RML alleviated Bcl-2, P13K, AKT, and HMGB1, as evidenced by RT-PCR and Western blot analysis.
CONCLUSIONS: Furthermore, RML triggered caspase-mediated mitochondrial apoptosis through the inactivation of the PI3K/AKT/HMGB1 pathway, eventually leading to GC cell death. This highlights that RML may be a potential natural antioxidant employed as a chemoprotective agent in GC rats.

BACKGROUND: Chronic atrophic gastritis (CAG) is a chronic digestive disease. Modern research has revealed substantial evidence indicating that the progression of CAG is closely linked to the occurrence of oxidative stress-induced DNA damage and apoptosis in the gastric mucosa. Additionally, research has indicated that Costunolide (COS), the primary active compound found in Aucklandiae Radix, a traditional herb, exhibits antioxidant properties. Nevertheless, the therapeutic potential of COS in treating CAG and its molecular targets have not yet been determined.
OBJECTIVE: The objective of this research was to explore the potential gastric mucosal protective effects and mechanisms of COS against N-Methyl-N´-nitro-N-nitrosoguanidine (MNNG)-induced CAG.
METHODS: Firstly, the MNNG-induced rat CAG model was established in vivo. Occurrence of CAG was detected through macroscopic examination of the stomachs and H&E staining. Additionally, we assessed oxidative stress, DNA damage, and apoptosis using biochemical detection, Western blot, immunohistochemistry and immunofluorescence. Then, an in vitro model was developed to induce MNNG-induced damage in GES-1 cells, and the occurrence of cell damage was determined by Hoechst 33,342 staining and flow cytometry. Finally, the key targets of COS for the treatment of CAG were identified through molecular docking, cellular thermal shift assay (CETSA), and inhibitor ML385.
RESULTS: In vivo studies demonstrated that COS promotes the expression of Nrf2 in gastric tissues. This led to an increased expression of SOD, GSH, HO-1, while reducing the production of MDA. Furthermore, COS inhibited DNA damage and apoptosis by suppressing the expression of γH2AX and PARP1 in gastric tissues. In vitro studies showed that COS effectively reversed apoptosis induced by MNNG in GES-1 cells. Additionally, COS interacted with Nrf2 to promote its expression. Furthermore, the expression levels of SOD, GSH, and HO-1 were augmented, while the generation of ROS and MDA was diminished.
CONCLUSIONS: Our results indicate that COS exhibits therapeutic effects on CAG through the promotion of Nrf2 expression and inhibition of oxidative stress and DNA damage. Therefore, COS has the potential to provide new drugs for the treatment of CAG.

N-Nitroso compounds (NOCs) are recognized as important factors that promote gastric cancer development, but the specific effects and potential mechanisms by which NOC exposure promotes gastric cancer are still poorly understood. In this study, we explored the effects and potential molecular mechanisms of NOCs on the promotion of gastric cancer using methylnitronitrosoguanidine (MNNG), a classical direct carcinogen of NOC. The results of in vivo and in vitro experiments showed that chronic and low-concentration MNNG exposure significantly promoted the malignant progression of tumors, including cell migration, cell invasion, vasculogenic mimicry (VM) formation, cell spheroid formation, stem cell-like marker expression, and gastric cancer growth and metastasis. Mechanistically, we revealed that demethylase ALKBH5 regulated the level of the N6‑methyladenosine (m6A) modification in the 3\'UTR and CDS region of the ZKSCAN3 mRNA to promote ZKSCAN3 expression, mediated the binding of ZKSCAN3 to the VEGFA promoter region to regulate VEGFA transcription, and participated in MNNG-induced gastric cancer cell migration, invasion, VM formation, cell spheroid formation, stem cell-like marker expression and ultimately gastric cancer progression. In addition, our study revealed that ALKBH5-ZKSCAN3-VEGFA signaling was significantly activated during MNNG-induced gastric carcinogenesis, and further studies in gastric cancer patients showed that ALKBH5, ZKSCAN3, and VEGFA expression were upregulated in cancers compared with paired gastric mucosal tissues, that ALKBH5, ZKSCAN3, and VEGFA could serve as important biomarkers for determining patient prognosis, and that the molecular combination showed greater prognostic value. These findings provide a theoretical basis for developing gastric cancer interventions for NOCs and for determining gastric cancer progression.

BACKGROUND: DNA mismatch repair (MMR) is a highly conserved pathway that corrects DNA replication errors, the loss of which is attributed to the development of various types of cancers. Although well characterized, MMR factors remain to be identified. As a 3\'-5\' exonuclease and endonuclease, meiotic recombination 11 homolog A (MRE11A) is implicated in multiple DNA repair pathways. However, the role of MRE11A in MMR is unclear.
METHODS: Initially, short-term and long-term survival assays were used to measure the cells\' sensitivity to N-methyl-N\'-nitro-N-nitrosoguanidine (MNNG). Meanwhile, the level of apoptosis was also determined by flow cytometry after MNNG treatment. Western blotting and immunofluorescence assays were used to evaluate the DNA damage within one cell cycle after MNNG treatment. Next, a GFP-heteroduplex repair assay and microsatellite stability test were used to measure the MMR activities in cells. To investigate the mechanisms, western blotting, the GFP-heteroduplex repair assay, and chromatin immunoprecipitation were used.
RESULTS: We show that knockdown of MRE11A increased the sensitivity of HeLa cells to MNNG treatment, as well as the MNNG-induced DNA damage and apoptosis, implying a potential role of MRE11 in MMR. Moreover, we found that MRE11A was largely recruited to chromatin and negatively regulated the DNA damage signals within the first cell cycle after MNNG treatment. We also showed that knockdown of MRE11A increased, while overexpressing MRE11A decreased, MMR activity in HeLa cells, suggesting that MRE11A negatively regulates MMR activity. Furthermore, we show that recruitment of MRE11A to chromatin requires MLH1 and that MRE11A competes with PMS2 for binding to MLH1. This decreases PMS2 levels in whole cells and on chromatin, and consequently comprises MMR activity.
CONCLUSIONS: Our findings reveal that MRE11A is a negative regulator of human MMR.

OBJECTIVE: Celastrus orbiculatus ethyl acetate extract (COE) is the main extract of the stem of the Chinese herbal C. orbiculatus, which has anti-tumor and anti-inflammatory biological effects. Our previous study showed that COE had a certain reversal effect on the precancerous lesions of gastric cancer (PLGC) in rats, but the exact mechanism of action remains elusive. We aimed to explore the therapeutic effects of COE on PLGC and the potential mechanisms.
METHODS: The PLGC rat model was successfully constructed by N-methyl-N´-nitro-N-nitrosoguanidine (MNNG) multifactorial induction method. Then, COE was prepared to treat the PLGC rat model. Hematoxylin & eosin staining was used to observe gastric mucosal lesions in rats, AB-PAS and HID-AB staining were used to observe intestinal metaplasia. PDCD4-ATG5 signaling pathway was detected by immunohistochemistry (IHC) and reverse transcription polymerase chain reaction (RT-PCR) in vivo, and autophagy level was detected by IHC, transmission electron microscopy, and RT-PCR in vivo. Besides, the PLGC (MC) cell model was successfully constructed by treating GES-1 cells with MNNG. Then, the morphology, proliferation, and apoptosis of MC cells, and the role of the PDCD4-ATG5 signaling pathway and autophagy in MC cells were evaluated by COE and after the overexpression of PDCD4 treatment.
RESULTS: COE significantly improved gastric mucosal injury and cellular heteromorphism and retarded the progression of PLGC in rats. Further studies indicated COE not only inhibited the level of autophagy but also interfered with the PDCD4-ATG5 signaling pathway in vivo. On the other hand, COE treatment could effectively reverse MC cell damage, inhibit MC cell proliferation, and promote MC cell apoptosis. Furthermore, COE also promoted PDCD4 and inhibited ATG5 expression in vitro, and the inhibitory effect of COE on ATG5-mediated autophagy was further enhanced after the overexpression of PDCD4.
CONCLUSIONS: The study revealed that COE could regulate the PDCD4-ATG5 signaling pathway to inhibit autophagy in gastric epithelial cells, which contributes to reversing the progression of PLGC.

Dormancy is a potential way for tumors to develop drug resistance and escape treatment. However, the mechanisms involved in cancer dormancy remain poorly understood. This is mainly because there is no in vitro culture model making it possible to spontaneously induce dormancy. In this context, the present work proposes the use of three-dimensional (3D) spheroids developed from osteosarcoma cell lines as a relevant model for studying cancer dormancy. MNNG-HOS, SaOS-2, 143B, MG-63, U2OS and SJSA-1 cell lines were cultured in 3D using the Liquid Overlay Technique (LOT). Dormancy was studied by staining cancer cells with a lipophilic dye (DiD), and long-term DiD+ cells were considered as dormant cancer cells. The role of the extracellular matrix in inducing dormancy was investigated by embedding cells into methylcellulose or Geltrex™. Gene expression of DiD+ cells was assessed with a Nanostring™ approach and the role of the genes detected in dormancy was validated by a transient down-expression model using siRNA treatment. Proliferation was measured using fluorescence microscopy and the xCELLigence technology. We observed that MNNG-HOS, 143B and MG-G3 cell lines had a reduced proliferation rate in 3D compared to 2D. U2OS cells had an increased proliferation rate when they were cultured in Geltrex™ compared to other 3D culture methods. Using 3D cultures, a transcriptomic signature of dormancy was obtained and showed a decreased expression of 18 genes including ETV4, HELLS, ITGA6, MCM4, PRKDC, RAD21 and UBE2T. The treatment with siRNA targeting these genes showed that cancer cell proliferation was reduced when the expression of ETV4 and MCM4 were decreased, whereas proliferation was increased when the expression of RAD21 was decreased. 3D culture facilitates the maintenance of dormant cancer cells characterized by a reduced proliferation and less differential gene expression as compared to proliferative cells. Further studies of the genes involved has enabled us to envisage their role in regulating cell proliferation.

Due to the lack of a precise in vitro model that can mimic the nature microenvironment in osteosarcoma, the understanding of its resistance to chemical drugs remains limited. Here, we report a novel three-dimensional model of osteosarcoma constructed by seeding tumor cells (MG-63 and MNNG/HOS Cl no. 5) within demineralized bone matrix scaffolds. Demineralized bone matrix scaffolds retain the original components of the natural bone matrix (hydroxyapatite and collagen type I), and possess good biocompatibility allowing osteosarcoma cells to proliferate and aggregate into clusters within the pores. Growing within the scaffold conferred elevated resistance to doxorubicin on MG-63 and MNNG/HOS Cl no. 5 cell lines as compared to two-dimensional cultures. Transcriptomic analysis showed an increased enrichment for drug resistance genes along with enhanced glutamine metabolism in osteosarcoma cells in demineralized bone matrix scaffolds. Inhibition of glutamine metabolism resulted in a decrease in drug resistance of osteosarcoma, which could be restored by α-ketoglutarate supplementation. Overall, our study suggests that microenvironmental cues in demineralized bone matrix scaffolds can enhance osteosarcoma drug responses and that targeting glutamine metabolism may be a strategy for treating osteosarcoma drug resistance.

Studying the regulatory mechanism of gastric disease progression to gastric cancer (GC) is essential. miR-520f expression is down-regulated in GC and inhibits the proliferation of gastric cancer cells, suggesting that it is associated with the development of GC, but whether it plays a role in the gastric precancerous lesion (GPL) is unclear. This study aimed to investigate the effect of miR-520f-3p in the N-methyl-N\'-nitro-N-nitrosoguanidine (MNNG)-induced GPL model and to elucidate the role of its downstream target gene Kruppel-like factor 7 (KLF7) in it. The experimental results showed that miR-520f-3p expression was down-regulated in the MNNG-induced GES-1 cell model, and overexpression of miR-520f-3p reversed the effects of MNNG on cell migration, invasion and epithelial-mesenchymal transition (EMT) -related protein expression. Meanwhile, overexpression of KLF7 attenuated the effect of miR-520f-3p on GPL. In a mouse GPL model, it was observed that MNNG elicited inflammation and EMT processes in mouse gastric tissues through the KLF7/ Nuclear Factor Kappa B (NFκB) pathway, and silencing KLF7 alleviated MNNG-induced gastric epithelial cell injury and gastric atrophy symptoms. These results provide a new perspective for understanding the development of GPL, and the development of new therapies targeting miR-520f-3p and KLF7 may provide new ideas for the prevention and treatment of gastric cancer.

As the representative item of environmental chemical carcinogen, MNNG was closely associated with the onset of Gastric cancer (GC), while the underlying mechanisms remain largely unknown. Here, we comprehensively analyzed the potential clinical significance of METTL3 in multiple GC patient cohorts. Additionally, we demonstrated that long-term exposure to MNNG elevated METTL3 and EMT marker expression by in vitro and in vivo models. Furthermore, the depletion of METTL3 impacted the proliferation, migration, invasion, and tumorigenesis of MNNG malignant transformation cells and GC cells. By me-RIP sequencing, we identified a panel of vital miRNAs potentially regulated by METTL3 that aberrantly expressed in MNNG-induced GC cells. Mechanistically, we showed that METTL3 meditated miR-1184/TRPM2 axis by regulating the process of miRNA-118. Our results provide novel insights into critical epigenetic molecular events vital to MNNG-induced gastric carcinogenesis. These findings suggest the potential therapeutic targets of METTL3 for GC treatment.