Epigenetic modulation by methionine deficiency attenuates the potential for gastric cancer cell dissemination

The Role of Methionine Restriction in Gastric Cancer: A Summary of Mechanisms and a Discussion on Tumor Heterogeneity

Gastric cancer is ranked as the fifth most prevalent cancer globally and has long been a topic of passionate discussion among numerous individuals. However, the incidence of gastric cancer in society has not decreased, but instead has shown a gradual increase in recent years. For more than a decade, the treatment effect of gastric cancer has not been significantly improved. This is attributed to the heterogeneity of cancer, which makes popular targeted therapies ineffective. Methionine is an essential amino acid, and many studies have shown that it is involved in the development of gastric cancer. Our study aimed to review the literature on methionine and gastric cancer, describing its mechanism of action to show that tumor heterogeneity in gastric cancer does not hinder the effectiveness of methionine-restricted therapies. This research also aimed to provide insight into the inhibition of gastric cancer through metabolic reprogramming with methionine-restricted therapies, thereby demonstrating their potential as adjuvant treatments for gastric cancer.

Identification and verification of the role of crucial genes through which methionine restriction inhibits the progression of colon cancer cells

Studies have shown that methionine restriction (MR) can inhibit tumor progression, but its mechanism in colon cancer is unknown. Through DESeq2 and Edge analysis of the GSE72131 and GSE103602 datasets, 649 co-upregulated and 532 co-downregulated genes affected by MR were identified, respectively. Enrichment analysis showed that these genes were closely associated with tumor progression. Combined with the differentially expressed genes of colon cancer in The Cancer Genome Atlas database, MR affected 330 dysregulated genes in colon cancer. On this basis, a transcriptional regulatory and competing endogenous RNA network was established and F transcription factor 1 and microRNA 17-92a-1 Cluster Host Gene were identified as a key transcription factor and long non-coding RNA, respectively. In addition, four genes (FA Complementation Group I, Holliday Junction Recognition Protein, Karyopherin Subunit Alpha 2 and Kinesin Family Member 15) were identified by analyzing the relationship between dysregulated genes and overall survival. Finally, western blotting, reverse transcription-quantitative PCR, Transwell and other in vitro experiments verified that MR inhibits HCT116 colon cancer cell proliferation, metastasis and invasion, induces apoptosis and downregulates 6 hub genes. Collectively, the present study identified potential targets for MR to inhibit colon cancer progression and contributed to the clinical application of MR.

Methionine deficiency promoted mitophagy via lncRNA PVT1-mediated promoter demethylation of BNIP3 in gastric cancer

BACKGROUND

The occurrence of recurrence and metastasis after treatment is a major challenge in the treatment of gastric cancer. This study was based on the methionine (Met)-dependent characteristics of gastric cancer cells to explore the effect of Met deficiency on the occurrence and development of gastric cancer.

METHODS

Human gastric cancer cell lines MKN45 and AGS and nude mice model were used to explore how Met affects gastric cancer by regulating lncRNA PVT1.

RESULTS

The levels of lncRNA PVT1 in gastric cancer cells and human gastric cancer xenografts of nude mice were down-regulated under the condition of Met deficiency. The cell viability and cell proliferation were declined after MKN45 and SGC-790 cells were cultured in Met-deficient medium. LncRNA PVT1 could affect BNIP3 promoter DNA methylation level through its interaction with DNMT1. Moreover, the silence of lncRNA PVT1 and the up-regulation of BNIP3 level inhibited the gastric cancer cell proliferation. Met deficiency could up-regulate BNIP3 expression by inhibiting the binding of lncRNA PVT1 to DNMT1, and activate mitophagy, thus inhibiting gastric cancer cell proliferation.

CONCLUSION

Our study suggested that Met deficiency could down-regulate the expression of lncRNA PVT1, further demethylated the promoter of BNIP3, thus inhibiting the proliferation of gastric cancer cells by activating mitophagy.

[Recombinant methioninase regulates PI3K/Akt/Glut-1 pathway and inhibits aerobic glycolysis to promote apoptosis of gastric cancer cells]

OBJECTIVE

To investigate the molecular mechanism of recombinant methioninase (rMETase) in promoting apoptosis of gastric cancer cells.

METHODS

Gastric cancer SGC-7901 cells were treated with rMETase (final concentration of 1.25 and 2.50 mmmol/L) for 72 h, and the changes in the cell viability were detected using CCK-8 method and the cell morphology changes were observed under an inverted microscope. Plate colony formation assay was used to evaluate colony formation ability of the cells, and flow cytometry was performed to analyze the changes in cell apoptosis and cell cycles. Glucose and lactate levels in the culture medium were determined using a colorimetric method and ATP concentration was detected using a fluorescence microplate reader; Western blotting was used to assess the effect of rMETase on PI3K/Akt pathway, glucose transporter-1 (GLUT-1), glycolysis- related proteins and apoptotic proteins in SGC-7901 cells.

RESULTS

rMETase significantly inhibited the proliferation and clonal formation, promoted cell apoptosis, and induced cell cycle arrest in S phase in SGC-7901 cells (P < 0.05). With the increase of rMETase concentration, the cells showed obviously decreased glucose intake accompanied by decreased glycolysis and ATP concentration (P < 0.001). The results of Western blotting showed that the expressions of PI3K, p-Akt/t-Akt, GLUT-1, and the key glycolytic enzymes HK2, PFKM, LDHA, antiapoptosis protein Bcl-2 were all downregulated and the pro-apoptotic proteins Bax and caspase-3 were up-regulated in response to rMETase treatment in SGC-7901 cells (P < 0.01).

CONCLUSIONS

rMETase can inhibit aerobic glycolysis, induce apoptosis and inhibit the proliferation of SGC-7901 cells by inhibiting the activity of PI3K/Akt/GLUT-1 pathway, suggesting its potential as a therapeutic agent for gastric cancer.

Methyl-donor depletion of head and neck cancer cells in vitro establishes a less aggressive tumour cell phenotype

PURPOSE

DNA methylation plays a fundamental role in the epigenetic control of carcinogenesis and is, in part, influenced by the availability of methyl donors obtained from the diet. In this study, we developed an in-vitro model to investigate whether methyl donor depletion affects the phenotype and gene expression in head and neck squamous cell carcinoma (HNSCC) cells.

METHODS

HNSCC cell lines (UD-SCC2 and UPCI-SCC72) were cultured in medium deficient in methionine, folate, and choline or methyl donor complete medium. Cell doubling-time, proliferation, migration, and apoptosis were analysed. The effects of methyl donor depletion on enzymes controlling DNA methylation and the pro-apoptotic factors death-associated protein kinase-1 (DAPK1) and p53 upregulated modulator of apoptosis (PUMA) were examined by quantitative-PCR or immunoblotting.

RESULTS

HNSCC cells cultured in methyl donor deplete conditions showed significantly increased cell doubling times, reduced cell proliferation, impaired cell migration, and a dose-dependent increase in apoptosis when compared to cells cultured in complete medium. Methyl donor depletion significantly increased the gene expression of DNMT3a and TET-1, an effect that was reversed upon methyl donor repletion in UD-SCC2 cells. In addition, expression of DAPK1 and PUMA was increased in UD-SCC2 cells cultured in methyl donor deplete compared to complete medium, possibly explaining the observed increase in apoptosis in these cells.

CONCLUSION

Taken together, these data show that depleting HNSCC cells of methyl donors reduces the growth and mobility of HNSCC cells, while increasing rates of apoptosis, suggesting that a methyl donor depleted diet may significantly affect the growth of established HNSCC.

Methionine tumor starvation by erythrocyte-encapsulated methionine gamma-lyase activity controlled with per os vitamin B6

Erymet is a new therapy resulting from the encapsulation of a methionine gamma-lyase (MGL; EC number 4.4.1.11) in red blood cells (RBC). The aim of this study was to evaluate erymet potential efficacy in methionine (Met)-dependent cancers. We produced a highly purified MGL using a cGMP process, determined the pharmacokinetics/pharmacodynamics (PK/PD) properties of erymet in mice, and assessed its efficacy on tumor growth prevention. Cytotoxicity of purified MGL was tested in six cancer cell lines. CD1 mice were injected with single erymet product supplemented or not with vitamin B6 vitamer pyridoxine (PN; a precursor of PLP cofactor). NMRI nude mice were xenografted in the flank with U-87 MG-luc2 glioblastoma cells for tumor growth study following five intravenous (IV) injections of erymet with daily PN oral administration. Endpoints included efficacy and event-free survival (EFS). Finally, a repeated dose toxicity study of erymet combined with PN cofactor was conducted in CD1 mice. Recombinant MGL was cytotoxic on 4/6 cell lines tested. MGL half-life was increased from <24 h to 9-12 days when encapsulated in RBC. Conversion of PN into PLP by RBC was demonstrated. Combined erymet + PN treatment led to a sustained Met depletion in plasma for several days with a 85% reduction of tumor volume after 45 days following cells implantation, and a significant EFS prolongation for treated mice. Repeated injections in mice exhibited a very good tolerability with only minor impact on clinical state (piloerection, lean aspect) and a slight decrease in hemoglobin and triglyceride concentrations. This study demonstrated that encapsulation of methioninase inside erythrocyte greatly enhanced pharmacokinetics properties of the enzyme and is efficacy against tumor growth. The perspective on these results is the clinical evaluation of the erymet product in patients with Met starvation-sensitive tumors.

CCR5 Antagonism by Maraviroc Reduces the Potential for Gastric Cancer Cell Dissemination

The chemokine (C-C motif) receptor 5 (CCR5) that belongs to the family of G protein-coupled receptors is exploited by macrophage tropic (R5) human immunodeficiency virus type 1 (HIV-1) to enter cells. Maraviroc, a small molecule CCR antagonist, is used as a part of combination antiretroviral therapy to treat persons infected by R5 HIV-1. CCR5 is expressed in various cancers, and its level of expression is a negative predictor of patients' survival in gastric cancers. Here, we report MKN45, MKN74, and KATOIII cells, three human gastric cancer cell lines with different stages of differentiation, which express CCR5 as detected by flow cytometry and reverse transcription-polymerase chain reaction (RT-PCR), and its ligand RANTES. In vitro experiments demonstrate that CCR5 antagonism reduces gastric cancer cell migration induced by macrophage inflammatory protein 1α (MIP-1α), MIP-1β, and RANTES and adhesion to the ex-planted murine peritoneum. Administration of maraviroc from days 3 to 10 after MKN45 cell inoculation to severe combined immunodeficient (SCID) mice effectively reduced the extent of peritoneal disease and increased survival. Maraviroc treatment also reduced the tumor burden in a xenograft model. Gene expression and RT-PCR analyses revealed that CCR5 antagonism in vivo modulates the expression of genes known for their role in cancer growth including interleukin-10 receptor B; hepatocyte growth factor receptor (MET); the homolog of the atypical cadherin gene, FAT1; Nm23-H1; and lymphotoxin β receptor. In summary, we have shown that CCR5 is mechanistically involved in dissemination of gastric cancer cells, suggesting that small molecule inhibitors of CCR5 might be exploited for their anticancer potential.