S-Adenosylmethionine Affects Cell Cycle Pathways and Suppresses Proliferation in Liver Cells

Antitumoral Activity of the Universal Methyl Donor S-Adenosylmethionine in Glioblastoma Cells

Glioblastoma (GBM), the most frequent and lethal brain cancer in adults, is characterized by short survival times and high mortality rates. Due to the resistance of GBM cells to conventional therapeutic treatments, scientific interest is focusing on the search for alternative and efficient adjuvant treatments. S-Adenosylmethionine (AdoMet), the well-studied physiological methyl donor, has emerged as a promising anticancer compound and a modulator of multiple cancer-related signaling pathways. We report here for the first time that AdoMet selectively inhibited the viability and proliferation of U87MG, U343MG, and U251MG GBM cells. In these cell lines, AdoMet induced S and G2/M cell cycle arrest and apoptosis and downregulated the expression and activation of proteins involved in homologous recombination DNA repair, including RAD51, BRCA1, and Chk1. Furthermore, AdoMet was able to maintain DNA in a damaged state, as indicated by the increased γH2AX/H2AX ratio. AdoMet promoted mitotic catastrophe through inhibiting Aurora B kinase expression, phosphorylation, and localization causing GBM cells to undergo mitotic catastrophe-induced death. Finally, AdoMet inhibited DNA repair and induced cell cycle arrest, apoptosis, and mitotic catastrophe in patient-derived GBM cells. In light of these results, AdoMet could be considered a potential adjuvant in GBM therapy.

Positive Regulation of S-Adenosylmethionine on Chondrocytic Differentiation via Stimulation of Polyamine Production and the Gene Expression of Chondrogenic Differentiation Factors

S-adenosylmethionine (SAM) is considered to be a useful therapeutic agent for degenerative cartilage diseases, although its mechanism is not clear. We previously found that polyamines stimulate the expression of differentiated phenotype of chondrocytes. We also found that the cellular communication network factor 2 (CCN2) played a huge role in the proliferation and differentiation of chondrocytes. Therefore, we hypothesized that polyamines and CCN2 could be involved in the chondroprotective action of SAM. In this study, we initially found that exogenous SAM enhanced proteoglycan production but not cell proliferation in human chondrocyte-like cell line-2/8 (HCS-2/8) cells. Moreover, SAM enhanced gene expression of cartilage-specific matrix (aggrecan and type II collagen), Sry-Box transcription factor 9 (SOX9), CCN2, and chondroitin sulfate biosynthetic enzymes. The blockade of the methionine adenosyltransferase 2A (MAT2A) enzyme catalyzing intracellular SAM biosynthesis restrained the effect of SAM on chondrocytes. The polyamine level in chondrocytes was higher in SAM-treated culture than control culture. Additionally, Alcian blue staining and RT-qPCR indicated that the effects of SAM on the production and gene expression of aggrecan were reduced by the inhibition of polyamine synthesis. These results suggest that the stimulation of polyamine synthesis and gene expression of chondrogenic differentiation factors, such as CCN2, account for the mechanism underlying the action of SAM on chondrocytes.

S-Adenosylmethionine Inhibits Colorectal Cancer Cell Migration through Mirna-Mediated Targeting of Notch Signaling Pathway

Metastasis is a leading cause of mortality and poor prognosis in colorectal cancer (CRC). Thus, the identification of new compounds targeting cell migration represents a major clinical challenge. Recent findings evidenced a central role for dysregulated Notch in CRC and a correlation between Notch overexpression and tumor metastasis. MicroRNAs (miRNAs) have been reported to cross-talk with Notch for its regulation. Therefore, restoring underexpressed miRNAs targeting Notch could represent an encouraging therapeutic approach against CRC. In this context, S-adenosyl-L-methionine (AdoMet), the universal biological methyl donor, being able to modulate the expression of oncogenic miRNAs could act as a potential antimetastatic agent. Here, we showed that AdoMet upregulated the onco-suppressor miRNAs-34a/-34c/-449a and inhibited HCT-116 and Caco-2 CRC cell migration. This effect was associated with reduced expression of migration-/EMT-related protein markers. We also found that, in colorectal and triple-negative breast cancer cells, AdoMet inhibited the expression of Notch gene, which, by luciferase assay, resulted the direct target of miRNAs-34a/-34c/-449a. Gain- and loss-of-function experiments with miRNAs mimics and inhibitors demonstrated that AdoMet exerted its inhibitory effects by upregulating miRNAs-34a/-34c/-449a. Overall, these data highlighted AdoMet as a novel Notch inhibitor and suggested that the antimetastatic effects of AdoMet involve the miRNA-mediated targeting of Notch signaling pathway.

mTORC1-independent translation control in mammalian cells by methionine adenosyltransferase 2A and S-adenosylmethionine

Methionine adenosyltransferase (MAT) catalyzes the synthesis of S-adenosylmethionine (SAM). As the sole methyl-donor for methylation of DNA, RNA, and proteins, SAM levels affect gene expression by changing methylation patterns. Expression of MAT2A, the catalytic subunit of isozyme MAT2, is positively correlated with proliferation of cancer cells; however, how MAT2A promotes cell proliferation is largely unknown. Given that the protein synthesis is induced in proliferating cells and that RNA and protein components of translation machinery are methylated, we tested here whether MAT2 and SAM are coupled with protein synthesis. By measuring ongoing protein translation via puromycin labeling, we revealed that MAT2A depletion or chemical inhibition reduced protein synthesis in HeLa and Hepa1 cells. Furthermore, overexpression of MAT2A enhanced protein synthesis, indicating that SAM is limiting under normal culture conditions. In addition, MAT2 inhibition did not accompany reduction in mechanistic target of rapamycin complex 1 activity but nevertheless reduced polysome formation. Polysome-bound RNA sequencing revealed that MAT2 inhibition decreased translation efficiency of some fraction of mRNAs. MAT2A was also found to interact with the proteins involved in rRNA processing and ribosome biogenesis; depletion or inhibition of MAT2 reduced 18S rRNA processing. Finally, quantitative mass spectrometry revealed that some translation factors were dynamically methylated in response to the activity of MAT2A. These observations suggest that cells possess an mTOR-independent regulatory mechanism that tunes translation in response to the levels of SAM. Such a system may acclimate cells for survival when SAM synthesis is reduced, whereas it may support proliferation when SAM is sufficient.

Identification of MCM4 as a Prognostic Marker of Hepatocellular Carcinoma

Methods

MCM4 expression difference in HCC were analyzed from TCGA and GEO data and verified by real-time PCR and western blot. ROC curve was used to analyze the diagnostic value of MCM4 and AFP. Additionally, the relationship between MCM4 and stage or nodal metastasis status or grade or age in TCGA cohort with HCC was observed from the UALCAN website. The univariate and multivariate Cox and functional analyses were done to explore the prognostic value of MCM4 in TCGA cohort.

Results

It was found that MCM4 was significantly highly expressed in HCC tissues from TCGA, GEO, and experimental data. Furthermore, ROC curve analysis showed that MCM4 was superior to be a diagnostic biomarker than AFP from TCGA (AUC_MCM4 = 0.9461, AUC_AFP = 0.7056) and GEO (GSE19665: AUC_MCM4 = 0.8800, AUC_AFP = 0.5100; GSE64041 AUC_MCM4 = 0.8038, AUC_AFP = 0.6304). AUC of MCM4 from real-time PCR result in 60 pairs of HCC and adjacent tissues was 0.7172, demonstrating the prediction value of MCM4. Besides, different expression tendencies of MCM4 among different stages or nodal metastasis status or grade or age were observed from the UALCAN website. In addition, multiROC analysis showed the advantage of MCM4 as a survival prediction at 1, 3, and 5 years with the higher AUC at 0.69 of 1 year, 0.65 of 3 years, and 0.61 of 5 years. It was shown that MCM4 was independently associated with OS in univariate and multivariate Cox analysis. And GSEA displayed that MCM4 was highly enriched in KEGG_CELL_CYCLE signaling pathway following higher correlation positively with CDC6, PLK1, CRC1, and BUB1B in HCC.

Conclusion

MCM4 might be a potential biomarker in guiding the prognostic status of HCC patients.

Identification of MCM family as potential therapeutic and prognostic targets for hepatocellular carcinoma based on bioinformatics and experiments

AIMS

The minichromosome maintenance (MCM) complex is highly conserved, which has drawn increasing attention on physiology and pathology process. However, the role of MCM in hepatocellular carcinoma (HCC) remains largely unclear. We aimed to conduct systematic analysis of expression patterns, prognostic values and potential functions of nine MCM genes in HCC, thus identifying their role in HCC.

MAIN METHODS

In our study, we systemically analyzed the role of MCM in prognosis and HCC progression by several bioinformatics analysis tools. Immunohistochemical (IHC) assays were utilized to valid the protein expression of MCM in HCC and in vitro experiments were used to confirm the functions of MCMs in HCC proliferation.

KEY FINDINGS

Overexpression of MCM2-8 and MCM10 were found to be significantly associated with clinical parameters and poor prognosis of HCC patients. The function of MCM was mainly enriched in DNA replication. Moreover, MCM were also associated with several cancer pathway and drug sensitivity in HCC. Close correlations were observed between immune cell infiltration and MCM in HCC. Cell Counting Kit-8 (CCK-8) and clone formation assays suggested the role of MCM2-8 and MCM10 in HCC proliferation.

SIGNIFICANCE

These results have implied that deregulated MCM played an important role in HCC progression and might be considered as potential therapeutic and prognostic targets for HCC.

S-Adenosylmethionine Inhibits Cell Growth and Migration of Triple Negative Breast Cancer Cells through Upregulating MiRNA-34c and MiRNA-449a

Triple-negative breast cancer (TNBC) is one of the most common malignancies worldwide and shows maximum invasiveness and a high risk of metastasis. Recently, many natural compounds have been highlighted as a valuable source of new and less toxic drugs to enhance breast cancer therapy. Among them, S-adenosyl-L-methionine (AdoMet) has emerged as a promising anti-cancer agent. MicroRNA (miRNA or miR)-based gene therapy provides an interesting antitumor approach to integrated cancer therapy. In this study, we evaluated AdoMet-induced modulation of miRNA-34c and miRNA-449a expression in MDA-MB-231 and MDA-MB-468 TNBC cells. We demonstrated that AdoMet upregulates miR-34c and miR-449a expression in both cell lines. We found that the combination of AdoMet with miR-34c or miR-449a mimic strongly potentiated the pro-apoptotic effect of the sulfonium compound by a caspase-dependent mechanism. For the first time, by video time-lapse microscopy, we showed that AdoMet inhibited the in vitro migration of MDA-MB-231 and MDA-MB-468 cells and that the combination with miR-34c or miR-449a mimic strengthened the effect of the sulfonium compound through the modulation of β-catenin and Small Mother Against Decapentaplegic (SMAD) signaling pathways. Our results furnished the first evidence that AdoMet exerts its antitumor effects in TNBC cells through upregulating the expression of miR-34c and miR-449a.

S-adenosylmethionine induces apoptosis and cycle arrest of gallbladder carcinoma cells by suppression of JAK2/STAT3 pathways

S-adenosylmethionine (SAM) is a naturally occurring physiologic molecule found ubiquitously in all mammalian cells and an essential compound in many metabolic pathways. It has been reported to possess many pharmacological properties including cancer-preventive and anticancer effects. However, the precise molecular mechanism involved in its anticancer effect is not yet clear. The present study is conducted to investigate the anticancer activity and the underlying mechanisms of SAM on human gallbladder cancer cells (GBC-SD and SGC-996) in vitro and in vivo. Cells were dealt with SAM and subjected to cell viability, colony formation, Hoechst staining, apoptosis, cycle arrest, western blot, and xenograft tumorigenicity assay. Experimental results showed that SAM could significantly inhibit the growth and proliferation and induce the apoptosis as well as cell cycle arrest in G0/G1 phase of GBC-SD and SGC-996 cells in a dose-dependent manner in vitro. The expression levels of p-JAK2, p-STAT3, Mcl-1, and Bcl-XL were significantly downregulated. In addition, inhibition of the JAK2/STAT3 pathway significantly enhanced the anti-apoptotic effect of SAM, suggesting the key roles of JAK2/STAT3 in the process. More importantly, our in vivo studies demonstrated that administration of SAM could significantly decrease the tumor weight and volume and immunohistochemistry analysis proved the downregulation of p-JAK2 and p-STAT3 in tumor tissues following SAM treatment, consistent with our in vitro results. In summary, our findings indicated that SAM can inhibit cell proliferation and induce apoptosis as well as cycle arrest of GBC cells by suppression of JAK2/STAT3 pathways and the dramatic effects of SAM hinting that SAM might be a useful therapeutic option for patients suffering from gallbladder cancer.

LINC00662 promotes hepatocellular carcinoma progression via altering genomic methylation profiles

The identification of viability-associated long noncoding RNAs (lncRNAs) is a means of uncovering therapeutic approaches for hepatocellular carcinoma (HCC). In addition, aberrant genome-wide hypomethylation has been implicated in HCC initiation and progression. However, the relationship between lncRNA dysregulation and genome-wide hypomethylation in hepatocarcinogenesis has not been fully elucidated. A novel lncRNA named LINC00662 was previously demonstrated to play a role in gastrointestinal cancer. In this study, we demonstrated that this lncRNA was correlated with survival and exhibited oncogenic properties, both in vitro and in vivo. Moreover, we determined that LINC00662 could lead to genome-wide hypomethylation and alter the genomic methylation profile by synchronously reducing the S-adenosylmethionine (SAM) level and enhancing the S-adenosylhomocysteine (SAH) level. Mechanistically, LINC00662 was determined to regulate the key enzymes influencing SAM and SAH levels, namely, methionine adenosyltransferase 1A (MAT1A) and S-adenosylhomocysteine hydrolase (AHCY), by RNA-RNA and RNA-protein interactions. In addition, we demonstrated that some SAM-dependent HCC-promoting genes could be regulated by LINC00662 by altering the methylation status of their promoters via the LINC00662-coupled axes of MAT1A/SAM and AHCY/SAH. Taken together, the results of this this study indicate that LINC00662 could be a potential biomarker for HCC therapy. More importantly, we proposed a new role of lncRNA in regulating genomic methylation to promote oncogene activation.