DNA mismatch repair status may influence anti-neoplastic effects of butyrate

Exploring the combined anti-cancer effects of sodium butyrate and celastrol in glioblastoma cell lines: a novel therapeutic approach

Glioblastoma, a highly aggressive and lethal brain cancer, lacks effective treatment options and has a poor prognosis. In our study, we explored the potential anti-cancer effects of sodium butyrate (SB) and celastrol (CEL) in two glioblastoma cell lines. SB, a histone deacetylase inhibitor, and CEL, derived from the tripterygium wilfordii plant, act as mTOR and proteasome inhibitors. Both can cross the blood-brain barrier, and they exhibit chemo- and radiosensitive properties in various cancer models. GB cell lines LN-405 and T98G were treated with SB and CEL. Cell viability was assessed by MTT assay and IC50 values were obtained. Gene expression of DNA repair, apoptosis, and autophagy-related genes was analyzed by RT-PCR. Cell cycle distribution was determined using flow cytometry. Viability assays using MTT assay revealed IC50 values of 26 mM and 22.7 mM for SB and 6.77 μM, and 9.11 μM for CEL in LN-405 and T98G cells, respectively. Furthermore, we examined the expression levels of DNA repair genes (MGMT, MLH-1, MSH-2, MSH-6), apoptosis genes (caspase-3, caspase-8, caspase-9), and an autophagy gene (ATG-6) using real-time polymerase chain reaction. Additionally, flow cytometry analysis revealed alterations in cell cycle distribution following treatment with SB, CEL and their combination. These findings indicate that SB and CEL may act through multiple mechanisms, including DNA repair inhibition, apoptosis induction, and autophagy modulation, to exert their anti-cancer effects in glioblastoma cells. This is the first study providing novel insights into the potential therapeutic effects of SB and CEL in glioblastoma.

Fusobacterium nucleatum load in MSI colorectal cancer subtypes

BACKGROUND

Fusobacterium nucleatum (F. nucleatum) infection may lead to colorectal cancer (CRC) development in the context of microsatellite instability (MSI). To date, however, the relationship between F. nucleatum load and MSI CRC subtypes has not been clarified.

METHODS

One hundred seventy-nine consecutive patients with CRC were enrolled in the present study. In 94 patients with MSI CRC, 32 had hereditary MSI CRC from Lynch syndrome, 62 had sporadic MSI CRC, while the remaining 85 had microsatellite stable (MSS) CRC. The association of the F. nucleatum load with each CRC subtype and the patients' clinicopathological characteristics was examined.

RESULTS

Of the 179 patients with CRC, 158 (88.3%) were F. nucleatum-positive. A high F. nucleatum load was found in 84.4% (27/32), 96.8% (60/62), and 83.5% (71/85) of the patients with hereditary MSI CRC, sporadic MSI CRC, and MSS CRC, respectively (P = 0.024). In terms of clinicopathological features, a high F. nucleatum load was significantly associated with female, right-sided CRC, BRAF V600E, CpG island methylator phenotype-positive CRC, and MSI CRC (P = 0.008, P = 0.015, P = 0.007, P = 0.006, and P < 0.001, respectively). However, the clinicopathological characteristics did not differ significantly by F. nucleatum load between hereditary and sporadic MSI CRCs without tumor depth.

CONCLUSIONS

The F. nucleatum load was higher in hereditary MSI CRC than in MSS CRC as well as sporadic MSI CRC. These findings may contribute to preventing CRC in hereditary MSI CRC through appropriate intervention.

Candidate SNP Markers of Atherogenesis Significantly Shifting the Affinity of TATA-Binding Protein for Human Gene Promoters show stabilizing Natural Selection as a Sum of Neutral Drift Accelerating Atherogenesis and Directional Natural Selection Slowing It

(1) Background: The World Health Organization (WHO) regards atherosclerosis-related myocardial infarction and stroke as the main causes of death in humans. Susceptibility to atherogenesis-associated diseases is caused by single-nucleotide polymorphisms (SNPs). (2) Methods: Using our previously developed public web-service SNP_TATA_Comparator, we estimated statistical significance of the SNP-caused alterations in TATA-binding protein (TBP) binding affinity for 70 bp proximal promoter regions of the human genes clinically associated with diseases syntonic or dystonic with atherogenesis. Additionally, we did the same for several genes related to the maintenance of mitochondrial genome integrity, according to present-day active research aimed at retarding atherogenesis. (3) Results: In dbSNP, we found 1186 SNPs altering such affinity to the same extent as clinical SNP markers do (as estimated). Particularly, clinical SNP marker rs2276109 can prevent autoimmune diseases via reduced TBP affinity for the human MMP12 gene promoter and therefore macrophage elastase deficiency, which is a well-known physiological marker of accelerated atherogenesis that could be retarded nutritionally using dairy fermented by lactobacilli. (4) Conclusions: Our results uncovered SNPs near clinical SNP markers as the basis of neutral drift accelerating atherogenesis and SNPs of genes encoding proteins related to mitochondrial genome integrity and microRNA genes associated with instability of the atherosclerotic plaque as a basis of directional natural selection slowing atherogenesis. Their sum may be stabilizing the natural selection that sets the normal level of atherogenesis.

Role of p38 MAPK in enhanced human cancer cells killing by the combination of aspirin and ABT-737

Regular use of aspirin after diagnosis is associated with longer survival among patients with mutated-PIK3CA colorectal cancer, but not among patients with wild-type PIK3CA cancer. In this study, we showed that clinically achievable concentrations of aspirin and ABT-737 in combination could induce a synergistic growth arrest in several human PIK3CA wild-type cancer cells. In addition, our results also demonstrated that long-term combination treatment with aspirin and ABT-737 could synergistically induce apoptosis both in A549 and H1299 cells. In the meanwhile, short-term aspirin plus ABT-737 combination treatment induced a greater autophagic response than did either drug alone and the combination-induced autophagy switched from a cytoprotective signal to a death-promoting signal. Furthermore, we showed that p38 acted as a switch between two different types of cell death (autophagy and apoptosis) induced by aspirin plus ABT-737. Moreover, the increased anti-cancer efficacy of aspirin combined with ABT-737 was further validated in a human lung cancer A549 xenograft model. We hope that this synergy may contribute to failure of aspirin cancer therapy and ultimately lead to efficacious regimens for cancer therapy.

Differential antineoplastic effects of butyrate in cells with and without a functioning DNA mismatch repair

The aim of this study was to investigate the differential antineoplastic effects of butyrate in cells with and without a functional mismatch repair and to determine the molecular mechanisms underlying these effects. SW48 colon cancer cells in which the MLH1 gene is silenced by promoter hypermethylation and demethylated SW48 cells in which the MLH1 gene is reexpressed were treated with butyrate (0-5mM) for 8 days and the effects on cell number, MLH1 gene promoter methylation, and expression of two cell cycle regulatory genes, CDK4 and GADD45A, were assessed. Butyrate suppressed viable cell number (P < 0.001) and reduced MLH1 promoter methylation (P < 0.05) in SW48 cells. However, in demethylated SW48 cells, butyrate caused an increase in viable cells (P < 0.05) and promoter methylation (P < 0.05). CDK4 expression was downregulated by butyrate exposure, but the effect was significantly greater for demethylated SW48 cells (P = 0.025). Butyrate treatment caused upregulation of GADD45A expression in SW48 cells but downregulation of GADD45A expression in demethylated SW48 cells (P = 0.045). This study supports the hypothesis that butyrate has more potent antineoplastic effects on colon cancer cells with MLH1 dysfunction. Differential expression of key cell cycle regulatory genes may explain some of the molecular mechanisms underlying these effects.

Folate and fiber in the prevention of colorectal cancer: Between shadows and the light

Colorectal cancer (CRC) is one of the most common malignancies and causes of cancer deaths throughout the world. Endoscopy has its functional and financial limitations; therefore, chemoprevention might be crucial in reducing the incidence of CRC. Although a number of studies have demonstrated the potential chemopreventive effects of folate (or folic acid), many challenges still remain. The relationship between folate intake and CRC risk is a complex association that might depend on many factors including gender, age, alcohol consumption, and smoking, all of which interfere with folate metabolism. The supplementary dose of fiber, the length of time required to observe the effects, and confounding factors exposed during the trial might also influence these findings. Therefore, more evidence from clinical studies is needed regarding the mechanisms that underlie the actions of bioactive food components in minimizing the risk of CRC.

Hydrophobic bile acids, genomic instability, Darwinian selection, and colon carcinogenesis

Sporadic colon cancer is caused predominantly by dietary factors. We have selected bile acids as a focus of this review since high levels of hydrophobic bile acids accompany a Western-style diet, and play a key role in colon carcinogenesis. We describe how bile acid-induced stresses cause cell death in susceptible cells, contribute to genomic instability in surviving cells, impose Darwinian selection on survivors and enhance initiation and progression to colon cancer. The most likely major mechanisms by which hydrophobic bile acids induce stresses on cells (DNA damage, endoplasmic reticulum stress, mitochondrial damage) are described. Persistent exposure of colon epithelial cells to hydrophobic bile acids can result in the activation of pro-survival stress-response pathways, and the modulation of numerous genes/proteins associated with chromosome maintenance and mitosis. The multiple mechanisms by which hydrophobic bile acids contribute to genomic instability are discussed, and include oxidative DNA damage, p53 and other mutations, micronuclei formation and aneuploidy. Since bile acids and oxidative stress decrease DNA repair proteins, an increase in DNA damage and increased genomic instability through this mechanism is also described. This review provides a mechanistic explanation for the important link between a Western-style diet and associated increased levels of colon cancer.

Selective sensitivity to carboxyamidotriazole by human tumor cell lines with DNA mismatch repair deficiency

We have previously reported that high-dose nifedipine had a selective antiproliferative effect on colon cancer cell lines deficient in DNA mismatch repair (MMR). We hypothesized that carboxyamidotriazole (CAI), a calcium channel blocker, would also have a selective inhibitory effect on colon cancer cell lines with DNA MMR deficiency. In addition, we speculated that this effect may also be seen in cell lines deficient in DNA MMR derived from other tumor types. Fourteen human cancer cell lines with and without DNA MMR derived from carcinomas of the colon, bladder, ovary and prostate were treated with CAI, vehicle or control drugs (nifedipine and 5-flurouracil). The effect of treatment on growth inhibition, invasion, apoptosis and cell cycle progression was assessed. Selective sensitivity to CAI was observed in all cancer cell lines deficient in MMR. Compared with the MMR-proficient cells, the matched deficient cells were significantly more sensitive to the growth inhibitory effect of CAI and nifedipine, but less sensitive to 5-flurouracil. CAI significantly inhibited the invasive ability of MMR-deficient cancer cells compared to 5-flurouracil. CAI induced more apoptosis but similar level of G(2)/M arrest in MMR (hMLH1- or hMSH6-)-deficient colon cancer cells than MMR-proficient counterparts. CAI selectively inhibits proliferation and invasion in MMR-deficient human cancer cell lines. The antitumor effect is at least partly explained by G2/M cell cycle arrest and induction of apoptosis. These findings may have clinical implications directing clinical trials in selectively targeted patients with DNA MMR tumors.

Chemotherapeutic agents for colorectal cancer with a defective mismatch repair system: The state of the art

Mismatch repair (MMR) proteins are capable of recognizing and processing not only single base-pair mismatches and insertion-deletion loops that occur during DNA replication, but also adducts in DNA resulting from treatment with cancer chemotherapy agents. MMR deficiency leads to microsatellite instability (MSI) and results in resistance to antimetabolites, alkylating and platinating agents, DNA minor groove binders, and inhibitors of topoisomerases. Therefore, anticancer agents that can be recommended for use in MMR deficient colorectal cancers are those that exert their cytotoxicity regardless of the MMR status. These include some alkylating drugs, brostacillin, gemcytabine, photodynamic therapy, taxanes. An approach that is currently receiving much attention is the use of agents such as 5-azacytidine, an inhibitor of the DNA methyltransferases, in combination with inhibitors of histone de-acetylation, to restore the MMR function. A strong anti-proliferative efficacy with a relatively low direct cytotoxicity, obtainable with oloumicine and roscovitine (selective cyclin-dependent kinases inhibitors) can represent a new expedient for the therapeutic treatment of MMR deficient colorectal cancers. The question of how MMR defects modulate the response to chemotherapeutics deserves further investigation, to enable a more aware choice of cancer treatment.