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Biomedical subjects

Jie Liao

Publications and source records attributed to Jie Liao.

At least 19 recordsLinked to original sources

Artificial Intelligence for Natural Products Discovery and Development.

Natural products (NPs) remain a cornerstone of modern drug discovery, offering stereochemical complexity and diverse bioactivities that precisely modulate therapeutic targets, refined through billions of years of evolution. However, their research has long been hindered by inefficient, empirical workflows, high resource consumption, structural complexity, and the "multicomponent, multi-target" nature of their mechanisms. The exponential growth of genomic, metabolomic, and spectral data has overwhelmed conventional analytical methods, exposing critical bottlenecks in handling high-dimensional, heterogeneous datasets that exceed human interpretive capacity. Artificial intelligence (AI) is emerging as a transformative paradigm to address these challenges, integrating multi-omics and chemical data to shift NP research from fragmented empiricism toward mechanism-driven, precision-oriented development. By leveraging deep learning architectures- including graph neural networks, Transformers, and diffusion-based generative models-AI enables systematic decoding of NP biosynthesis, automated structure elucidation, rational target identification, knowledge extraction from vast unstructured scientific literature, and de novo molecular design. This review comprehensively surveys recent advances in AI applications across the full NP discovery and development pipeline, encompassing genome mining, structure-based and ligand-based virtual screening, multimodal structural characterization, lead optimization, and biosynthetic pathway engineering. We further examine the emerging roles of protein-centric, molecule- centric, and multimodal foundation models, as well as large language models, in bridging genotype-to-chemotype gaps and unlocking unstructured scientific knowledge. Finally, we discuss critical challenges including data scarcity, representational limitations for complex stereochemistry, physical plausibility in generative models, and the urgent need for experimental validation, while outlining future directions toward autonomous experimentation, closed-loop optimization, and human-AI collaborative discovery.

Artificial intelligence↗

Colorectal carcinoma development in inducible nitric oxide synthase-deficient mice with dextran sulfate sodium-induced ulcerative colitis.

The overproduction of reactive oxygen and nitrogen species (RONS) may play an important role in ulcerative colitis (UC)-associated carcinogenesis. In order to study the role of nitric oxide (NO) in UC-associated colorectal carcinogenesis, the development of colorectal carcinoma was studied using the DSS-induced and iron-enhanced model of chronic UC in inducible nitric oxide synthase (iNOS)-deficient mice. Female wild-type C57BL/6 (iNOS+/+) and iNOS-/- mice were administered 1% DSS (w/v) through the drinking fluid for 15 DSS cycles and fed twofold iron-enriched diet. Colorectal inflammation and mucosal ulceration of moderate severity were observed in both iNOS+/+ and iNOS-/- mice. Similar tumor incidence and multiplicity in the colon were observed that 15 out of 23 (65.2%) iNOS+/+ mice developed colorectal tumors with a tumor multiplicity of 1.47+/-0.17 (mean+/-SE) after 15 DSS cycles, and 13 out of 19 (68.4%) iNOS-/- mice developed colorectal tumors with a tumor multiplicity of 2.08+/-0.21. Histopathologically, the tumors were confirmed to be well-differentiated adenocarcinomas. Nitrotyrosine, an indicator of peroxynitrite-caused protein modification, was detectable by immunohistochemistry in inflammatory cells and epithelial cells of the colon in iNOS+/+ and iNOS-/- mice, and no difference in staining intensity was observed between the two groups. Immunostaining for endothelial NOS (eNOS) was observed in lamina propria macrophages and colonic blood vessels, and eNOS protein levels were increased in the inflamed colon. These results show that there is no difference in UC-associated cancer development in iNOS+/+ and iNOS-/- mice, and suggest that in the absence of iNOS, other factors, such as eNOS, may play a role in nitrosative stress and UC-associated carcinogenesis in this model system.

Administration, Oral↗

Inhibition of adenoma progression to adenocarcinoma in a 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis model in A/J mice by tea polyphenols and caffeine.

The present study investigated the inhibitory effects of Polyphenon E [a standardized green tea polyphenol preparation containing 65% (-)-epigallocatechin-3-gallate] and caffeine on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumor progression from adenoma to adenocarcinoma. Female A/J mice were treated with a single dose of NNK (103 mg/kg body weight, i.p.) and kept for 20 weeks for the mice to develop lung adenomas. The mice were then given a solution of 0.5% Polyphenon E or 0.044% caffeine as the sole source of drinking fluid until week 52. Both treatments significantly decreased the number of visible lung tumors. Histopathologic analysis indicated that Polyphenon E administration significantly reduced the incidence (by 52%) and multiplicity (by 63%) of lung adenocarcinoma. Caffeine also showed marginal inhibitory effects in incidence and multiplicity of adenocarcinoma (by 48% and 49%, respectively). Markers of cell proliferation, apoptosis, and related cell signaling were studied by immunohistochemistry, and the labeling index and staining intensity were quantified by the Image-Pro system. Polyphenon E and caffeine treatment inhibited cell proliferation (by 57% and 50%, respectively) in adenocarcinomas, enhanced apoptosis in adenocarcinomas (by 2.6- and 4-fold, respectively) and adenomas (both by 2.5-fold), and lowered levels of c-Jun and extracellular signal-regulated kinase (Erk) 1/2 phosphorylation. In the normal lung tissues, neither agent had a significant effect on cell proliferation or apoptosis. The results show that tea polyphenols (and perhaps caffeine) inhibit the progression of NNK-induced lung adenoma to adenocarcinoma. This effect is closely associated with decreased cell proliferation, enhanced apoptosis, and lowered levels of c-Jun and Erk1/2 phosphorylation.

Adenocarcinoma↗

Inhibition of chronic ulcerative colitis associated adenocarcinoma development in mice by inositol compounds.

Chronic inflammation is a well recognized risk factor for cancer and patients with long-standing ulcerative colitis (UC) are at an increased risk for colorectal carcinoma development. In order to prevent UC associated carcinogenesis, we tested the effects of inositol compounds (including inositol and hexaphosphate inositol) on UC-associated carcinogenesis in our novel mouse model. Female C57BL/6 mice were subjected to long-term, cyclic dextran sulfate sodium (DSS) treatment and fed a 2-fold iron-enriched diet. The inositol compounds were administered via the drinking fluid. In the DSS-plus-2-fold iron positive control group, colorectal adenocarcinoma incidence was 70.6% (24/34 mice) after 15 cycles of DSS treatment (1 DSS cycle=7 day DSS treatment period followed by a 10 day recovery period). Tumor multiplicity was 1.26+/-1.05 and tumor volume was 21.4+/-5.2 mm3. Adding 1% inositol, tumor incidence was statistically significantly reduced (42%, 9 of 21 mice with tumors), as was tumor multiplicity (0.5+/-0.7) and tumor volume (4.2+/-1.9 mm3). Administration of hexaphosphate inositol noticeably reduced tumor incidence (50%, 12 mice with tumors out of 24 total), tumor multiplicity (0.8+/-0.9) and tumor volume (12.3+/-4.1 mm3); however, the results were not statistically significant (P>0.05). Further mechanistic studies showed that the inhibition of UC-associated carcinogenesis by inositol compounds might relate to their function on the modulation of macrophage mediated inflammation, nitro-oxidative stress and cell proliferation in UC-associated carcinogenesis. This study indicates that inositol compounds may have the potential to serve as preventive agents for chronic inflammation-carcinogenesis.

Adenocarcinoma↗

Membrane lateral diffusion and capture of CFTR within transient confinement zones.

The cystic fibrosis transmembrane conductance regulator (CFTR) channel interacts with scaffolding and other proteins that are expected to restrict its lateral movement, yet previous studies have reported predominantly free diffusion. We examined the lateral mobility of CFTR channels on live baby hamster kidney cells using three complementary methods. Channels bearing an extracellular biotinylation target sequence were labeled with streptavidin conjugated with fluorescent dyes (Alexa Fluor 488 or 568) or quantum dots (qDot605). Fluorescence recovery after photobleaching and image correlation spectroscopy of the dye-labeled channels revealed a significant immobile population ( approximately 50%), which was confirmed by direct single particle tracking (SPT) of qDot605-labeled CFTR. Adding 10 histidine residues at the C-terminus of CFTR to mask the postsynaptic density 95, Discs large, ZO-1 (PDZ) binding motif abolished its association with EBP50/NHERF1, reduced the immobile fraction, and increased mobility. Other interactions that are not normally detected on this timescale became apparent when binding of PDZ domain proteins was disrupted. SPT revealed that CFTR(His-10) channels diffuse randomly, become immobilized for periods lasting up to 1 min, and in some instances are recaptured at the same location. The impact of transient confinement on the measured diffusion using the three fluorescence techniques were assessed using computer simulations of the biological experiments. Finally, the impact of endosomal CFTR on mobility measurements was assessed by fluorescence correlation spectroscopy. These results reveal unexpected features of CFTR dynamics which may influence its ion channel activity.

Animals↗

Analysis of phospholipid species in rat peritoneal surface layer by liquid chromatography/electrospray ionization ion-trap mass spectrometry.

The main phospholipids in rat peritoneal surface layer were analyzed by normal-phase high-performance liquid chromatography (HPLC) coupled with electrospray ionization (ESI) ion-trap mass spectrometry (MS). By using a silica gel column and a gradient of hexane/isopropanol/water as mobile phase containing 5 mmol/L ammonium formate as modifiers, a baseline separation of glycerophosphoehtanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylcholine (PC), sphingomyelin (SM) and lyso-phosphatidylcholine (LPC) was obtained and more than 90 phospholipid constituents in rat peritoneal surface were identified and determined by on-line ion-trap MS detection. The major ethanolamine glycerophospholipids in rat peritoneal surfaces were plasmalogens that were highly enriched in polyunsaturated fatty acids at the sn-2 position. In addition, the fragmentation patterns for each phospholipid class by the ion-trap MS were discussed.

Animals↗

Separation of phospholipids by capillary zone electrophoresis with indirect ultraviolet detection.

A simple method for separation of different anionic and zwitterionic phospholipid classes by capillary zone electrophoresis (CZE), using indirect UV detection with adenosine monophosphate (AMP) as background electrolyte and the UV-absorbing additive, was successfully developed in this study. The separation conditions including apparent pH (pH*) of running buffer, concentration of AMP, organic solvent, applied voltage and capillary temperature were systematically optimized. The application of this method to human blood sample was also briefly examined.

Adenosine Monophosphate↗

Cystic fibrosis transmembrane conductance regulator function is suppressed in cigarette smokers.

RATIONALE: Cigarette smoke extract inhibits chloride secretion in human bronchial epithelial cells. Oxidants decrease gene expression, protein expression, and function of the cystic fibrosis transmembrane conductance regulator (CFTR). OBJECTIVES: Because cigarette smoke is a rich source of oxidants, we verified the hypothesis that CFTR may be suppressed by exposure to cigarette smoke in vitro and in vivo. METHODS: The effects of cigarette smoke exposure on Calu-3 and T84 cell CFTR expression and function were observed. Also studied were the nasal potential differences (PDs) in 26 men (9 smokers, 17 nonsmokers) who had no detectable CFTR gene mutations as determined during investigations for infertility. CFTR expression and function were determined by Northern blotting, Western blotting, and cAMP-dependent 125I efflux assays. Extensive CFTR genotyping was performed in each subject. Nasal PD measurements were made at baseline and during amiloride, chloride-free buffer, and isoproterenol perfusions. MAIN RESULTS: Cigarette smoke decreased CFTR expression and function in Calu-3 and T84 cell lines. Furthermore, the nasal PDs of cigarette smokers showed a pattern typical of CFTR deficiency with a blunted response to chloride-free buffer and isoproterenol compared with nonsmokers (-9.6 +/- 4.0 vs. -22.3 +/- 10.1 mV; p < 0.001). CONCLUSIONS: We conclude that cigarette smoke decreases the expression of CFTR gene, protein, and function in vitro and that acquired CFTR deficiency occurs in the nasal respiratory epithelium of cigarette smokers. We suggest that acquired CFTR deficiency may contribute to the physiopathology of cigarette-induced diseases such as chronic bronchitis.

Adult↗

[Effect of intestinal ischemia/reperfusion injury on leptin and orexin-A levels].

OBJECTIVE: To explore the effect of intestinal ischemia/reperfusion (I/R) injury on leptin and orexin-A levels in peripheral blood and central secretory tissues, and investigate the roles of leptin and orexin-A in acute inflammatory responses. METHODS: An intestinal I/R injury rat model was established, and the rats were grouped according to duration of the reperfusion time following a 60-min ischemia. Radioimmunoassay was used to examine the protein levels of leptin in the serum and adipose tissue, and the protein levels of orexin-A in the plasma and hypothalamus. Reverse transcriptase-polymerase chain reaction was also performed to detect the mRNA expressions of adipose leptin and hypothalamus orexin-A. RESULTS: Compared with that before injury, serum leptin level of 60-min ischemia with 30-min reperfusion (I60'R30') group decreased significantly and that of I60'R360' increased significantly. Compared with the sham-operation group (sham) after injury, serum leptin level of I60'R360' group increased significantly, and adipose leptin protein levels of I60'R30' and I60'R90' groups decreased significantly, whereas that of I60'R360' group increased obviously. Compared with sham group after injury, adipose leptin mRNA expressions of I60'R30', I60'R240' and I60'R360' groups all increased significantly, while that of I60'R150' showed significant decrease. No significant changes were noted in the protein levels of orexin-A either in the plasma or hypothalamus after I/R injury. In comparison with sham group after injury, hypothalamus orexin-A mRNA expressions of I60'R30' and I60'R90' groups showed gradual but significant decrease, and till 150 min of reperfusion, the expression reached its lowest, followed then by slow recovery at 240 and 360 min, though still remaining significantly lower than that of sham group. CONCLUSION: Leptin and orexin-A have a time-dependent response to intestinal I/R injury, but the former appears to exhibit a faster response, and they may play a certain role in the metabolic disorders of acute inflammation.

Animals↗

Inhibition of intestinal tumorigenesis in Apcmin/+ mice by (-)-epigallocatechin-3-gallate, the major catechin in green tea.

The present study was designed to investigate the effects of two main constituents of green tea, (-)-epigallocatechin-3-gallate (EGCG) and caffeine, on intestinal tumorigenesis in Apc(min/+) mice, a recognized mouse model for human intestinal cancer, and to elucidate possible mechanisms involved in the inhibitory action of the active constituent. We found that p.o. administration of EGCG at doses of 0.08% or 0.16% in drinking fluid significantly decreased small intestinal tumor formation by 37% or 47%, respectively, whereas caffeine at a dose of 0.044% in drinking fluid had no inhibitory activity against intestinal tumorigenesis. In another experiment, small intestinal tumorigenesis was inhibited in a dose-dependent manner by p.o. administration of EGCG in a dose range of 0.02% to 0.32%. P.o. administration of EGCG resulted in increased levels of E-cadherin and decreased levels of nuclear beta-catenin, c-Myc, phospho-Akt, and phospho-extracellular signal-regulated kinase 1/2 (ERK1/2) in small intestinal tumors. Treatment of HT29 human colon cancer cells with EGCG (12.5 or 20 micromol/L at different times) also increased protein levels of E-cadherin by 27% to 58%, induced the translocation of beta-catenin from nucleus to cytoplasm and plasma membrane, and decreased c-Myc and cyclin D1 (20 micromol/L EGCG for 24 hours). These results indicate that EGCG effectively inhibited intestinal tumorigenesis in Apc(min/+) mice, possibly through the attenuation of the carcinogenic events, which include aberrant nuclear beta-catenin and activated Akt and ERK signaling.

Animals↗

Oxidant stress suppresses CFTR expression.

Epithelial mucous membranes are repeatedly exposed to oxidants and xenobiotics. CFTR plays a role in glutathione transepithelial flux and in defining the hydration and viscoelasticity of protective mucus. We therefore hypothesized that CFTR expression and function may be modulated by oxidant stress. A sublethal oxidant stress (tert-butylhydroquinone, BHQ) in CFTR-expressing epithelial cells (T84) induced a significant increase in cellular glutathione that was associated with an increase in expression of the gene encoding the heavy subunit of the rate-limiting enzyme for glutathione synthesis, gamma-glutamylcysteine synthetase (gamma-GCShs). CFTR gene expression was markedly decreased according to a time course that mirrored the changes in gamma-GCShs. Western blot analysis confirmed that the decrease in CFTR gene expression was associated with a decrease in CFTR protein. cAMP-dependent iodide efflux was also decreased by the oxidant stress. Nuclear run-on assays indicated that the oxidant stress had no effect on CFTR gene transcription, but the mRNA stability in the oxidant-stressed cells was markedly reduced. Furthermore, BHQ increased gamma-GCShs mRNA while decreasing CFTR mRNA in Calu-3 cells, and taurine chloramine induced similar effects in T84 cells. We conclude that suppression of CFTR expression may represent an adaptive response of mucosal epithelium to an exogenous oxidant stress.

Adenocarcinoma↗

Phosphorylation of CFTR by PKA promotes binding of the regulatory domain.

The unphosphorylated regulatory (R) domain of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) is often viewed as an inhibitor that is released by phosphorylation. To test this notion, we studied domain interactions using CFTR channels assembled from three polypeptides. Nucleotides encoding the R domain (aa 635-836) were replaced with an internal ribosome entry sequence so that amino- and carboxyl-terminal half-molecules would be translated from the same mRNA transcript. Although only core glycosylation was detected on SplitDeltaR, biotinylation, immunostaining, and functional studies clearly demonstrated its trafficking to the plasma membrane. SplitDeltaR generated a constitutive halide permeability, which became responsive to cAMP when the missing R domain was coexpressed. Each half-molecule was co-precipitated by antibody against the other half. Contrary to expectations, GST-R domain was pulled down only if prephosphorylated by protein kinase A, and coexpressed R domain was precipitated with SplitDeltaR much more efficiently when cells were stimulated with cAMP. These results indicate that phosphorylation regulates CFTR by promoting association of the R domain with other domains rather than by causing its dissociation from an inhibitory site.

Animals↗

Administration of green tea or caffeine enhances the disappearance of UVB-induced patches of mutant p53 positive epidermal cells in SKH-1 mice.

Irradiation of female SKH-1 hairless mice with UVB (30 mJ/cm2) twice a week for 10-20 weeks resulted in the formation of a large number of cellular patches (>8 adjacent cells/patch) that are recognized with an antibody (Pab240) which recognizes mutated but not wild-type p53 protein. These patches are not recognized by an antibody (Pab1620) to wild-type p53 protein. The patches, which are considered putative early cellular markers of the beginning of tumor formation, started appearing after 4-6 weeks of UVB treatment, and multiple patches were observed after treatment for 10 weeks. The number and size of the patches increased progressively with continued UVB treatment. Discontinuation of UVB for 4 weeks resulted in an 80-90% decrease in the number of these patches. The number of the remaining patches did not decrease any further but remained relatively constant for at least 4-9 weeks. Oral administration of green tea (6 mg tea solids/ml) or caffeine (0.4 mg/ml) as the sole source of drinking fluid during irradiation with UVB, twice a week for 20 weeks, inhibited UVB-induced formation of mutant p53 positive patches by approximately 40%. Oral administration of green tea (6 mg tea solids/ml) as the sole source of drinking fluid or topical applications of caffeine (6.2 micromol) once a day 5 days a week starting immediately after discontinuation of UVB treatment enhanced the rate and extent of disappearance of the mutant p53-positive patches. Topical applications of caffeine to the dorsal skin of mice pretreated with UVB for 20 weeks resulted in enhanced apoptosis selectively in focal basal cell hyperplastic areas of the epidermis (putative precancerous lesions), but not in areas of the epidermis that only had diffuse hyperplasia. Our studies indicate that the chemopreventive effect of caffeine or green tea may occur by a proapoptotic effect preferentially in early precancerous lesions.

Administration, Oral↗

Systemic iron supplementation replenishes iron stores without enhancing colon carcinogenesis in murine models of ulcerative colitis: comparison with iron-enriched diet.

Ulcerative colitis (UC) patients frequently require iron supplementation to remedy anemia. The impact of systemic iron supplementation (intraperitoneal injection) on UC-associated carcinogenesis was assessed in mice subjected to cyclic dextran sulfate sodium (DSS) treatment and compared with dietary iron enrichment. Systemic iron supplementation, but not a twofold iron diet, remedied iron deficiency as indicated by the histochemical detection of splenic iron stores. A twofold iron diet, but not systemic iron, increased iron accumulation in colonic luminal contents, at the colonic mucosal surface, and in superficial epithelial cells. Colitis-associated colorectal tumor incidence after 15 DSS cycles was not affected by systemic iron (2/28; 7.1%) compared to nonsupplemented controls (4/28; 14.1%) but was significantly increased by the twofold iron diet (24/33; 72.7%) (P < 0.001). Mechanistic study revealed that systemic iron had no effect on DSS-induced inflammation, or colonic iNOS and COX-2 protein levels, compared to controls. Systemic iron supplementation for 16 weeks replenished splenic iron in a spontaneous colitis model (interleukin-2-deficient mice) and significantly reduced colonic inflammation compared to interleukin-2 (-/-) controls without increasing hyperplastic lesions. These results suggest that iron supplemented systemically could be used to remedy anemia in UC patients without exacerbating inflammation or enhancing colon cancer risk. These findings need to be verified in clinical studies.

Adenocarcinoma↗

Inhibition of carcinogenesis by polyphenols: evidence from laboratory investigations.

Many plant polyphenolic compounds have been shown to have cancer-preventing activities in laboratory studies. For example, tea and tea preparations have been shown to inhibit tumorigenesis in a variety of animal models of carcinogenesis, involving organ sites such as the skin, lungs, oral cavity, esophagus, stomach, liver, pancreas, small intestine, colon, and prostate. In some of these models, inhibitory activity was demonstrated when tea was administered during the initiation, promotion, or progression stage of carcinogenesis. The cancer-preventing activities of these and other polyphenols, such as curcumin, genistein, and quercetin, are reviewed. In studies in vitro, many of these compounds have been shown to affect signal transduction pathways, leading to inhibition of cell growth and transformation, enhanced apoptosis, reduced invasive behavior, and slowed angiogenesis. However, the concentrations used in cell culture studies were much higher than those found in vivo. If we propose mechanisms for cancer prevention on the basis of cell line experiments, then these activities must be demonstrated in vivo. The bioavailability, ie, tissue and cellular concentrations, of dietary polyphenols is a determining factor in their cancer-preventing activity in vivo. For example, compounds such as curcumin are effective when applied topically to the skin or administered orally to affect the colon but are not effective in internal organs such as the lungs. More in-depth studies on bioavailability should facilitate correlation of mechanisms determined in vitro with in vivo situations, increase our understanding of dose-response relationships, and facilitate extrapolation of results from animal studies to human situations.

Animals↗

Kidney disease and the metabolic syndrome.

The epidemic of metabolic syndrome contributes to the rapid growth of cardiovascular and renal diseases. Hyper-hemodynamics, impaired pressure natriuresis, excess excretory load, insulin resistance, endothelial dysfunction, chronic inflammation, and prothrombotic status individually and interdependently initiate renal injury in metabolic syndrome. The prevention and treatment of kidney disease require a multifactorial approach. Weight loss through diet control and exercise can reverse many pathophysiologic processes. Pharmacologic intervention includes insulin sensitizers, tight glycemic and lipid control, blockage of renin angiotensin aldosterone system, and anti-inflammatory and antithrombotic therapies. Each peroxisome proliferator-activated receptor isoform plays a distinct role in metabolic syndrome, and their agonists may prevent or reverse the early renal injuries.

Cardiovascular Diseases↗

Promoter hypermethylation and inactivation of O(6)-methylguanine-DNA methyltransferase in esophageal squamous cell carcinomas and its reactivation in cell lines.

The purpose of this study was to characterize the role of DNA hypermethylation in the loss of expression of O(6)-methylguanine-DNA methyltransferase (MGMT) during the development of esophageal squamous cell carcinoma (ESCC) and to investigate its reactivation in cell lines. Samples were collected from Linzhou City of the Henan province in northern China, a high-risk area of this disease. The hypermethylation of promoter CpG islands of the MGMT gene was examined by methylation-specific PCR in ESCC and neighboring non-tumorous tissues, as well as in laser capture microdissected samples with normal epithelium, basal cell hyperplasia (BCH), and dysplasia (DYS). The MGMT mRNA and protein expression were determined with RT-PCR and immunohistochemistry, respectively. Five of 17 (29%) normal, 10 of 20 (50%) BCH, 8 of 12 (67%) DYS, and 13 of 18 (72%) ESCC samples had DNA hypermethylation in the MGMT promoter region, showing a gradual increase with the progression of carcinogenesis. The frequency of the loss of MGMT mRNA and protein expression progressively decreased from normal to BCH, DYS, and ESCC, and it was highly correlated with MGMT promoter hypermethylation according to Fisher's exact tests. When each individual sample was considered, good concordance between DNA hypermethylation and the loss of expression of MGMT was also observed. In samples from the same patient, if hypermethylation was detected in earlier lesions, it was usually observed in more severe lesions. In the ESCC cell line KYSE 510, treatment with a DNA methyltransferase inhibitor, 2'-deoxy-5-azacytidine partially reversed the CpG hypermethylation status and restored mRNA expression of the MGMT gene. Similar reactivation of MGMT gene by dietary polyphenols, (-)-epigallocatechin-3-gallate and genistein, has also been observed. The results suggest that the DNA hypermethylation of MGMT is an important mechanism for MGMT gene silencing in the development of ESCC, and this epigenetic event may be prevented or reversed by these polyphenols for the prevention of carcinogenesis.

Carcinoma, Squamous Cell↗