Preventive effect of Actinidia valvata Dunn extract on N-methyl-N'-nitro-N-nitrosoguanidine-induced gastrointestinal cancer in rats

The role of LncRNA TUG1 in DNA damage and malignant transformation induced by Helicobacter pylori and N-methyl-N'-nitro-N-nitrosoguanidine on human esophageal epithelial cells

N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) and Helicobacter pylori might synergistically promote the malignant transformation of human esophageal epithelial cells (HEECs) through inducing DNA double-strand breaks (DSBs) and inhibition of PAXX protein expression. The long noncoding RNA (lncRNA) TUG1 is associated with multiple cancers, and its overexpression can promote cancer by interfering with the functions of oncogenes. LncRNA TUG1 is also associated with DNA methyltransferase 1 (DNMT1) and the epithelial signaling pathway of H. pylori infection. To explore the role of LncRNA TUG1 in the malignant transformation of HEECs induced by H.pylori + MNNG, a stable strain of HEECs with LncRNA TUG1 knockdown (LncRNA TUG1-KD) was constructed using RNA interference technology with lentivirus as a vector. Set up negative controls LncRNA TUG1-NC (null carrier lentivirus was selected to transfect HEECs) and block controls (normal HEECs without exposure). H. pylori + MNNG were added to the LncRNA TUG1-KD and LncRNA TUG1-NC groups for 6 h and then passaged until their malignant transformation. From each group, cells in the early, intermediate, and late stages of malignant transformation were used for the alkaline comet assay and determination of protein expression, including γ-H2AX and PAXX, by western blotting assay to assess DNA damage and repair processes. Clone formation assay in soft agar and nude mouse xenograft model was used to assess malignancy. This study suggests that H. pylori + MNNG promotes the malignant transformation of HEECs by inducing DNA DSBs and inhibiting PAXX expression, and this effect may be alleviated by LncRNA TUG1 knockdown. It elucidates the pathogenesis of EC from the perspective of the combined effect of epigenetic and environmental carcinogens, offering new insights for the comprehensive prevention and treatment of EC.

The effect of phytochemicals in N-methyl-N-nitro-N-nitroguanidine promoting the occurrence and development of gastric cancer

Gastric cancer is a common malignant tumor of the digestive tract, with a low early diagnosis rate. N-methyl-N-nitro-N-nitroguanidine (MNNG) is one of the main risk factors for gastric cancer. Phytochemicals are healthy active substances derived from vegetables, fruits, nuts, tea, herbal medicines and other plants. Taking phytochemicals is a very promising strategy for the prevention and treatment of gastric cancer. Many studies have proved that phytochemicals have protective effects on MNNG induced gastric cancer via inhibiting cell proliferation, enhancing immunity, suppressing cell invasion and migration, inducing apoptosis and autophagy, blocking angiogenesis, inhibiting Helicobacter pylori infection as well as regulating metabolism and microbiota. The intervention and therapeutic effects of phytochemicals in MNNG induced gastric cancer have attracted more and more attention. In order to better study and explore the role, advantages and challenges of phytochemicals in MNNG induced gastric cancer, we summarized the intervention and therapeutic effects of phytochemicals in MNNG induced gastric cancer. This review may help to further promote the research and clinical application of phytochemicals in MNNG induced gastric cancer, and provide some new insights.

Helicobacter pylori plus N-Methyl-N’-nitro-N-nitrosoguanidine: DNA damage and repair; malignant transformation of human esophageal epithelial cells

N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG), found in pickled foods and in chlorinated water, has been used to induce malignant transformation and gastrointestinal cancer in rats. Helicobacter pylori (HP) is implicated in human gastric cancer and possibly also in esophageal cancer. These two agents - one chemical and the other biological - might act together to induce esophageal cancer. In this study, human esophageal epithelial cells (HEECs) were divided into four groups: HP, MNNG, HP + MNNG, and control. The HP-to-HEEC ratio was 100:1. Cells were exposed for 6 h and then passaged until malignant transformation. HEEC at early, intermediate, and late stages of malignant transformation were used for proliferation, cell-cycle, and invasion assays. The alkaline comet assay was performed and expression of proteins, including γ-H2AX and PAXX, was studied by western blotting, to explore DNA damage and repair processes. Measurements of cell morphology, soft-agar clone formation, and invasiveness, and a nude mouse xenograft model, were used to examine malignancy. The effect of HP was stronger than that of MNNG. The combination HP + MNNG exerted a stronger malignant transformation effect than either HP or MNNG alone. Mechanisms of this combined carcinogenesis may include promotion of cell proliferation, perturbation of the cell cycle, promotion of invasiveness, DNA double-strand break induction, or PAXX inhibition.

The ITS analysis and identification of Actinidia eriantha and its related species

The dried plant material of medically important plant Actinidia eriantha especially when it remains in the form of powder often look morphologically similar to its related species. The lack of efficient methods to distinguish the authentic material from other similar species leads to chances of adulteration. The molecular authentication of herbal plant materials such as the internal transcribed spacer (ITS) sequences is considered as more reliable method compared to morphological traits. In this study, we aim to evaluate the potential of identification for roots of A. eriantha and its related species by ITS sequences. The lengths of ITS regions ranged from 624 to 636 bp with GC content ranging from 50.96% to 59.55%. A total of 194 variation sites and 46 haplotypes were formed in 185 samples. Among them, the roots of A. eriantha possessed specific sites at 85bp (C), 205bp (T), 493bp (C), 542bp (G), 574bp (C), 582bp (T) and 610bp (G), while A. hemsleyana, A. callosa, A. valvata and A. polygama have their own specific sites. The inter-specific genetic distance among 8 Actinidia species in the range 2.28% to 11.00%. The phylogenetic tree constructed with ITS, ITS1 and ITS2 region showed that the ITS sequences have higher potential for identification in 8 Actinidia species. However, as to A. eriantha, A. hemsleyana and A. valvata, these three barcodes have the same identification ability. The ITS regions indicated that different samples from same species can be grouped together, except for A. arguta and A. melanandrah. In conclusion, the ITS sequences can be used as an efficient DNA barcode for the identification of A. eriantha and its related species.

Effect of ethyl acetate extract of usnea longissima on esophagogastric adenocarcinoma in rats1

Purpose

To investigate the effects of the EtOAc extract of U. longissima which is uninvestigated previously on esophagogastric cancer induced in rats with N-methyl-N-nitro-N-nitrosoguanidin (MNNG).

Methods

The anticancer activity of EtOAc extract of U. longissima was examined in the esophagogastric adenocarcinoma models induced in rats with MNNG. EtOAc extract of U. longissima, 50 and 100 mg/kg oral doses were administered once daily for six months. MNNG induced differentiated and undifferentiated type adenocarcinomas in the esophageal and gastric tissues of rats.

Results

EtOAc extract of U. longissima obtained from U. longissima prevented gastric and esophageal cancerogenesis induced in rats with MNNG. EtOAc extract of U. longissima did not have a lethal effect at doses of 500, 1000 and 2000 mg/kg. The prominent anticarcinogenic activity of EtOAc extract of U. longissima 50 and 100 mg/kg suggests that it is not toxic and it is selective to the cancer tissue.

Conclusion

This information may shed light on clinical implementation of EtOAc extract of U. longissima in future.

N-methyl-N-nitro-N-nitrosoguanidine-mediated ING4 downregulation contributed to the angiogenesis of transformed human gastric epithelial cells

AIMS

Angiogenesis is associated with the progression and mortality of gastric cancer. Epidemiological evidences indicate that long-term N-nitroso compounds (NOCs) exposure predominantly contributes to the mortality of gastric cancer. Therefore, further reduced mortality of gastric cancer demands to explore the exact mechanisms of NOCs induced angiogenesis. As a tumor suppressor gene, inhibitor of growth protein 4 (ING4) plays an important role in pathological angiogenesis. In this study, we will investigate ING4 expression level in human gastric epithelial cells after the long-term low dose exposure of N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and the pathological impact of MNNG-reduced ING4 on angiogenesis of transformed cells.

MAIN METHODS

The soft agar colony formation assay, Western blotting, immunofluorescence and wound healing assay were used to evaluate the characteristics of transformed cells. HUVEC growth and tube formation assays were performed to test the angiogenic abilities. EMSA, luciferase reporter gene assay, real-time PCR and Western blotting were used to explore the exact mechanism.

KEY FINDINGS

By establishing transformed human gastric epithelial cells via chronic low dose treatment, a gradually ING4 downregulation was observed in the later-stage of MNNG-induced cell transformation. Moreover, we demonstrated that MNNG exposure-reduced ING4 expression significantly resulted into aggravating angiogenesis through increasing the phosphorylation level of NF-κB p65 and subsequently DAN binding activity and regulating the expressions of NF-κB p65 downstream pro-angiogenic genes, MMP-2 and MMP-9.

SIGNIFICANCE

Our findings provided a significant mechanistic insight into angiogenesis of MNNG-transformed human gastric epithelial cell and supported the concept that ING4 may be a relevant therapeutic target for gastric cancer.

miR-374 mediates the malignant transformation of gastric cancer-associated mesenchymal stem cells in an experimental rat model

Mesenchymal stem cells (MSCs) are a critical component of the tumor microenvironment. Upon distinct pathological stimulus, MSCs show phenotypic and functional changes. Gastric cancer is one of the leading causes of cancer‑related deaths worldwide. The roles and mechanisms of MSCs in gastric cancer have not been well characterized. In the present study, we investigated the roles of MSCs in the malignant transformation from gastritis to gastric cancer using an N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric cancer model. We isolated MSCs from the gastric tissues of normal (RGN-MSCs) and MNNG-exposed rats (RGI-MSCs), and compared the biological properties of RGI-MSCs with RGN-MSCs. We found that RGI-MSCs had increased proliferative and migratory capabilities than these capacities noted in the RGN-MSCs. In addition, RGI-MSCs produced higher levels of IL-6, CXCL10 and MCP-1 than RGN-MSCs. Moreover, RGI-MSCs promoted the migration of normal gastric mucosa epithelial cells by inducing epithelial-mesenchymal transition (EMT). The upregulation of miR-374 in RGI-MSCs was partially responsible for their increased proliferative and migratory capabilities. Collectively, our findings provide new evidence for the roles of MSCs in gastric carcinogenesis, suggesting that targeting gastric cancer-associated MSCs may represent a novel avenue for gastric cancer therapy.

Clinical significance of the phosphorylation of MAPK and protein expression of cyclin D1 in human osteosarcoma tissues

The aim of the present study was to investigate the significance of the phosphorylation of mitogen-activated protein kinase (MAPK) and the protein expression of cyclin D1 in human osteosarcoma tissues. Human osteosarcoma tissue samples were collected from 30 patients, benign bone tumor samples were collected from 30 patients, and normal bone tissues were collected from 10 individuals as controls. Immunohistochemistry was performed to measure the levels of phosphorylated (p)-MAPK and cyclin D1 protein in cases of human osteosarcoma. The results showed that the positive rates of MAPK and cyclin D1 in osteosarcoma were 86.67% (26/30) and 73.00% (22/30), respectively. The positive staining rates of MAPK and cyclin D1 in benign bone tumor tissues were 10.00% (3/30) and 3.30% (1/30), respectively. The positive rate in the normal bone tissues was 0% (0/30), which was significantly lower, compared with that of the cancerous bone tissue. The positive rates of MAPK and cyclin D1 in osteosarcoma were increased (P<0.05), and the expression of cyclin D1 and p‑MAPK were positively correlated. The phosphorylation of MAPK may be important in the development of osteosarcoma, and the overactivation of MAPK may induce high expression of cyclin D1 and induce tumor cells to proliferate continuously.

Clinical significance of STAT3 and MAPK phosphorylation, and the protein expression of cyclin D1 in skin squamous cell carcinoma tissues

The present study aimed to investigate the significance of the phosphorylation of signal transducer and activator of transcription 3 (STAT3) and mitogen‑activated protein kinase (MAPK), and the protein expression of cyclin D1, in skin squamous cell carcinoma (SCC) tissues. SCC specimens from the skin were collected from 30 patients, and normal skin tissues were collected from 10 individuals as a control. Immunohistochemistry was used to assess the protein expression levels of phosphorylated (p‑)STAT3, p‑MAPK and cyclin D1 in the SCC tissues. The levels of p‑STAT3 protein were abnormally increased in SCC (P<0.05); however, no significant differences in the protein expression of p‑MAPK were identified between the normal skin and the SCC specimens. The extent of the upregulation of the expression of p‑STAT3 and cyclin D1 correlated with the depth of tumor invasion (P<0.05). A positive correlation existed between the expression of p‑STAT3 and cyclin D1 in SCC. However, no association between the expression intensity of p‑MAPK and cyclin D1 was identified in SCC. It is postulated that the activation of STAT3 may induce the overexpression of cyclin D1, which results in the persistent proliferation of these tumor cells in SCC.