Role of NADP+-dependent isocitrate dehydrogenase (NADP+-ICDH) on cellular defence against oxidative injury by gamma-rays

PURPOSE

To investigate the regulation of NADPH-producing isocitrate dehydrogenase (ICDH) in cytosol (IDPc) and mitochondria (IDPm) upon gamma-ray irradiation, and the roles of IDPc and IDPm in the protection against cellular damage induced by gamma-ray irradiation.

MATERIALS AND METHODS

Changes of IDPc and IDPm proteins upon gamma-ray irradiation to NIH3T3 cells were analysed by immunoblotting. To increase or decrease the expression of IDPc or IDPm, NIH3T3 cells were stably transfected with mouse IDPc or IDPm cDNA in either the sense or the antisense direction. The transfected cells with either increased or decreased IDPc or IDPm were exposed to gamma-rays, and the levels of reactive oxygen species generation, protein oxidation and lipid peroxidation were measured.

RESULTS

Both IDPc and IDPm activities were induced by gamma-ray in NIH3T3 cells. Cells with decreased expression of IDPc or IDPm had elevated reactive oxygen species generation, lipid peroxidation and protein oxidation. Conversely, overproduction of IDPc or IDPm protein partially protected the cells from oxidative damage induced by gamma-ray irradiation.

CONCLUSIONS

The protective role of IDPc and IDPm against gamma-ray-induced cellular damage can be attributed to elevated NADPH, reducing equivalents needed for recycling reduced glutathione in the cytosol and mitochondria. Thus, a primary biological function of the ICDHs may be production of NADPH, which is a prerequisite for some cellular defence systems against oxidative damage.

Analysis of genes responding to ultraviolet B irradiation of HaCaT keratinocytes using a cDNA microarray

BACKGROUND

Ultraviolet (UV) B irradiation causes many important biological changes in skin, which lead to pathophysiological alterations of the homeostatic environment.

OBJECTIVES

To gain more insight into the molecular events provoked by UVB irradiation, we performed cDNA microarray analysis.

METHODS

Immortalized HaCaT keratinocytes were irradiated with a high cytotoxic dose of UVB (50 mJ cm(-2)), and total RNA was isolated. Fluorescently labelled probes were prepared by reverse transcription and were hybridized with cDNA microarray slides made using 840 cDNA clones.

RESULTS

Time-course cDNA microarray analysis revealed the global gene expression profile after UVB exposure. Of 840 genes tested, 192 genes showed changes in their expression levels at one or more of four time points. The genes were clustered into four groups according to their expression patterns in a self-organizing maps analysis. Classification of these genes into nine functional categories revealed that UVB irradiation affected several biological processes. The genes that were first upregulated and then returned to normal levels included several genes related to the inhibition of cell growth and the proteasome pathway. Conversely, the expressions of many genes involved in the cytoskeleton, signal transduction, metabolism and transcription were first downregulated or unchanged and then upregulated later, reflecting the recovery of UVB-damaged cellular activities.

CONCLUSIONS

These results demonstrate the complexity of the transcriptional profile of the UVB response, and provide a basis for the global characterization of UV-regulated gene expression.

Immunomodulating Effects of CKBM on the Cytokine Production in Peripheral Blood Mononuclear Cells (PBMCs) from Healthy Volunteers

The current study investigated the immunomodulating effect of CKBM on cytokine induction in peripheral blood mononuclear cells (PBMCs) isolated from 20 healthy volunteers. Cytometric Bead Analysis (CBA) was used to study IL-2, IL-4, IL-6, IL-10, TNF-alpha and IFN-gamma. TNF-alpha and IL-6 were significantly increased in a CKBM dose- and time-dependent manner. Flow cytometry analysis showed an increased intracellular staining of IL-6 but not of TNF-alpha in CKBM treated PBMCs. In addition, MTT cell cytotoxicity assay showed that CKBM concentrations below 5% did not significantly affect the metabolic activities of PBMCs. The current study indicated that CKBM may modulate the immune response by inducing the secretions of TNF-alpha and IL-6, which are cytokine mediators of innate immunity and inflammation preparing or "priming" the body to combat diseases.

Identification of calcium-inducible genes in primary keratinocytes using suppression-subtractive hybridization

Terminal differentiation in epidermal keratinocytes involves major biochemical changes including the expression of many new differentiation-specific genes. To further understand this process, we performed suppression-subtractive hybridization of keratinocytes cultured under high-calcium condition, known to induce differentiation in vitro. We randomly isolated 300 clones representing 90 different genes. By reverse Northern blot analyses, 20 different genes were found to be overexpressed, of which 13 were confirmed as differentially expressed genes during keratinocyte differentiation by Northern blot analysis. Of those, five genes, transglutaminase 1, keratin 6, interleukin-1 receptor antagonist, kallikrein 7, and heat shock protein 27, are known to be up-regulated during epidermal differentiation. Six genes, ferritin-L chain, ribosomal protein S6, tumor-associated calcium signal transducer 2, neuroendocrine secretory protein 55, phosphoserine aminotransferase, and neutrophil gelatinase-associated lipocalin, heretofore were not known to be up-regulated during keratinocyte differentiation. We also identified two novel genes. One of these maps to chromosome 1q21 of the epidermal differentiation complex, and its expression level was strongly increased in differentiating keratinocytes. These differentially expressed genes may provide significant opportunities for further understanding of the epidermal keratinocyte differentiation.

Detection of RTP801, a gene that is differentially expressed in irradiated HeLa cells

PURPOSE

To quantify the effects of irradiation on the expression levels of a differentially expressed gene, RTP801, in HeLa cells.

MATERIALS AND METHODS

Total RNA was isolated from irradiated and non-irradiated HeLa cells. A subtraction library was constructed, from which 88 random clones were screened. The expression patterns of one clone, detected by reverse Northern blotting, were quantified by real time RT-PCR, using CYBR green I dye.

RESULTS

RTP801, a hypoxia-inducible factor-I-responsive gene, was identified as a differentially expressed gene in HeLa cells exposed to X-ray. Real time RT-PCR showed that the mRNA levels of RTP801 were greatly diminished by radiation.

CONCLUSIONS

These results suggest that down-regulation of hypoxia-inducible factor-I-responsive genes, such as RTP801, in irradiated HeLa cells may result in reductions in the radiotherapy resistance of tumor cells.

Heterogeneity detector: finding heterogeneous positions in Phred/Phrap assemblies

A modification to Phred and program to detect heterogeneous positions, which is particularly useful in the identification of mutations and other abnormalities in Phred/Phrap genome assemblies.

AVAILABILITY

The package is made available at http://glscompute.gis.a-star.edu.sg/~charlie/DHetero.html

A rare cause of intestinal perforation in an extreme low birth weight infant--gastrointestinal mucormycosis: a case report

We report an extreme low birth weight infant with gastrointestinal mucormycosis (GM) mimicking necrotizing enterocolitis on day 15 of age. Emergency laparotomy confirmed ileal perforations. Subsequently, tissue histology confirmed GM. This is the most premature infant who survived after GM and is the third reported neonatal survivor in English literature.

Maternal diclofenac sodium ingestion and severe neonatal pulmonary hypertension

We describe a case of severe pulmonary hypertension and transient right-sided hypertrophic cardiomyopathy in a neonate, caused by premature closure of ductus arteriosus after short-term maternal use of diclofenac sodium (Voltaren). In view of this associated complication, diclofenac sodium should be avoided during pregnancy. In addition, maternal diclofenac sodium ingestion should be suspected if a newborn develops severe pulmonary hypertension and/or right-sided hypertrophic cardiomyoptathy with closed ductus arteriosus.

Ammonium nitrogen removal from slurry-type swine wastewater by pretreatment using struvite crystallization for nitrogen control of anaerobic digestion

Precipitation of ammonium together with phosphate and magnesium is a possible alternative for lowering the nitrogen content of wastewater. In this study we examine the removal of ammonium nitrogen and phosphorus from slurry-type swine wastewater containing high concentrations of nutrients by the addition of phosphoric acid along with either calcium oxide or magnesium oxide, which leads to the crystallization of insoluble salts such as hydroxyapatite and struvite. The struvite crystallization method showed a high capacity for the removal of nitrogen when magnesium oxide and phosphoric acid were used as the magnesium and phosphate sources, respectively. When it was applied to swine wastewater containing a high concentration of nitrogen, the injection molar ratio of Mg2+:NH4+:PO4(3-) that gave maximum ammonium nitrogen removal was 3.0:1.0:1.5.

Updated gestational age specific birth weight, crown-heel length, and head circumference of Chinese newborns

OBJECTIVE

To construct gestation specific standards of birth weight, crown-heel length, and head circumference of Chinese infants.

DESIGN

A prospective cross sectional population study.

METHODS

The birth weight, crown-heel length, and head circumference were prospectively measured using standard equipment in newborns delivered at 24-42 weeks gestation in the maternity units of 10 public hospitals and two private hospitals in Hong Kong. The findings were used to construct gestation specific standards of these variables. The LMS method using maximum penalised likelihood was used to perform model fitting. The results were compared with those obtained from a cohort of infants born in the same locality between 1982 and 1986.

RESULTS

From October 1998 to September 2000, a total of 10 032 infants were measured, representing 9.6% of the total deliveries in Hong Kong during that period. An extra 307 infants with gestation < or = 35 weeks were recruited from October 2000 to June 2001. Each of the three variables showed a normal distribution at each gestational week. Gestation specific reference standards for each variable were constructed for male and female infants separately. Comparison with the 1982-1986 cohort showed a significant secular trend to increased birth weight. The trend was small, but significant, for crown-heel length and head circumference.

CONCLUSION

These growth standards will provide useful references for the care of newborns of ethnic Chinese origin. These standards, especially that for birth weight, should be updated regularly.

A double-blind, randomised- placebo, controlled, parallel group, multicentre, flexible-dose escalation study to assess the efficacy and safety of sildenafil administered as required to male outpatients with erectile dysfunction in Korea

The efficacy and safety of sildenafil was evaluated in a randomiSed, double-blind, placebo-controlled, flexible-dose study in Korean men aged 28-78 y with erectile dysfunction (ED) of broad-spectrum aetiology and more than 6 months duration. A total of 133 patients were randomised at six centres in Korea to receive either sildenafil (50 mg initially, increased if necessary to l00 mg or decreased to 25 mg depending on efficacy and tolerance) (n=66) or matching placebo (n=67) taken on an 'as needed' basis l h prior to anticipated sexual activity for a period of 8 weeks. At the end of this time, the primary efficacy variables relating to the achievement and maintenance of erections sufficient for sexual intercourse, and the secondary efficacy variables, which included: (1) the five separate domains of sexual functioning of the International Index of Erectile Function (IIEF) scale, (2) the percentage of successful intercourse attempts, and (3) a global assessment of erections, were all statistically significantly improved by sildenafil in comparison with placebo (P&<0.0001). Treatment-related adverse events occurred in 56.1% of patients receiving sildenafil and 20.9% receiving placebo. The most common adverse events with sildenafil were vasodilatation (flushing), headache and abnormalities in colour vision (31.8, 22.7 and 6.1% of patients, respectively), and most were mild in nature. The efficacy and safety of sildenafil in this population of Korean men appears similar to that reported in other studies in western populations.

Polyhydroxyalkanoate (PHA) production from waste

PHA (polyhydroxyalkanoate) production was attempted with SBRs from food waste. Seed microbes were collected from a sewage treatment plant with a biological nutrient removal process, and acclimated with synthetic substrate prior to the application of the fermented food waste. Laboratory SBRs were used to produce PHA with limited oxygen and nutrients. The maximum content of 51% PHA was obtained with an anaerobic/aerobic cycle with P limitation, and the yield was estimated to be about 0.05 gPHA(produced)/gCOD(applied) or 25 kg PHA/dry ton of food waste, assuming more than 40% of the PHA contents were recoverable. PHB/PHA ratios were 0.74 to 0.77 due to the higher acetate concentrations. Economical analysis seemed to suggest the PHA produced from the food waste could be an alternative material to produce the biodegradable plastic to be used for the collection bags for solid waste.

Identification of new endogenous retroviral sequences belonging to the HERV-W family in human cancer cells

A human endogenous retroviral family (HERV-W) has recently been identified on chromosome 7 that contains a single complete open reading frame putatively encoding an envelope protein. We have identified fifteen HERV-W families on human genomic DNA using a monochromosomal panel in our previous study. In order to identify additional families, we examined genomic DNA derived from cancer cell lines (A549, AZ521, OVCAR3, RT4) using the PCR approach. Five env fragments of a HERV-W family were newly identified and analyzed. They showed a high degree of nucleotide sequence similarity (93-97%) to that of the other HERV-W families. Translation of the env fragments showed no frameshift and termination codon by deletion/insertion or point mutation in clones A549-2, AZ521-3, and OVCAR-3. The ratio of synonymous to nonsynonymous substitutions indicated that negative selective pressure is acting on A549-2, AZ521-3, and OVCAR-3 sequences. These env gene sequences could be associated with an active provirus in human cancer cells (A549, AZ521, OVCAR3).

Conditional loss of TGF-beta signalling leads to increased susceptibility to gastrointestinal carcinogenesis in mice

BACKGROUND

Downregulation of TGF-beta receptors is implicated in colon cancer development. Inactivation of either of the two transmembrane serine/threonine kinases, TGF-beta1 types I/II receptors, is now implicated in carcinogenesis, especially gastrointestinal carcinogenesis.

METHODS

We generated transgenic mice, called pS2-dnRII or ITF-dnRII, of which the dominant negative mutant of the TGF-beta type II receptor was expressed under the control of tissue-specific promoters, the pS2 promoter for stomach and ITF for intestine. They were either infected with H.pylori (ATCC 43504 strain, CagA+ and VacA+) or administered with azoxymethane to determine the significance of loss of TGF-beta signalling in gastrointestinal carcinogenesis.

RESULTS

Gastric adenocarcinoma developed in pS2-dnRII mice, whereas only chronic active gastritis was noted in wild-type littermates after 36 weeks of H.pylori infection. Mice lacking in TGF-beta signalling specifically in the stomach showed a significantly higher proliferation cell nuclear antigen-labelling index when infected with H.pylori than wild-type littermates (P < 0.01). Development of colonic aberrant crypt foci was provoked in mice by intraperitoneal injections of azoxymethane, and ITF-dnRII mice showed significantly higher incidences of ACF and colon cancers than wild-type littermates.

CONCLUSIONS

Maintaining normal TGF-beta signalling in the gastrointestinal tract seems to be important either for preventing abnormal mucosal proliferation, or for suppressing or retarding carcinogenesis.

Genetic factors associated with endothelial dysfunction affect the early onset of coronary artery disease in Korean males

The maintenance of balance between nitric oxide (NO) and the superoxide anion is required for proper functioning of the endothelium. To investigate the relationship between genetic factors associated with endothelial function and the development of coronary artery disease (CAD), endothelial nitric oxide synthase (ecNOS) gene a/b polymorphism and NADH/NADPH oxidase p22 phox gene C242T polymorphism were examined in 305 Korean male CAD patients and 215 healthy male control subjects. The beta-fibrinogen gene H1/H2 polymorphism was also analyzed. Both ecNOS a/b and p22 phox C242T polymorphisms were found to be associated with the development of CAD in the study population (p=0.020 and 0.011, respectively). When the association was analyzed by age, statistical significance was retained only in those <51 years (p=0.021 and 0.025 for the a/b and the C242T polymorphism, respectively) and not in those >51 years of age (p=0.155 and 0.278 respectively). However, the distribution of the beta-fibrinogen H1/H2 genotypes was not found to be associated with the development of CAD in either the < or =50 (p = 0.611) or >50 groups (p = 0.188). The ecNOS gene a/b polymorphism and the NADH/NADPH oxidase p22 phox gene C242T polymorphism were found to be significantly associated with the development of CAD in Korean male patients less than 51 years old.

Optical organophosphorus biosensor consisting of acetylcholinesterase/viologen hetero Langmuir-Blodgett film

The fiber-optic biosensor consisting of an acetylcholinesterase (AChE)-immobilized Langmuir-Blodgett (LB) film was developed to detect organophosphorus compounds in contaminated water. The sensing scheme was based on the decrease of yellow product, o-nitrophenol, from a colorless substrate, o-nitrophenyl acetate, due to the inhibition by organophosphorus compounds on AChE. Absorbance change of the product as the output of enzyme reaction was detected and the light was guided through the optical fibers. The enzyme portion of the sensor system was fabricated by the LB technique for formation of the enzyme film. AChE-immobilized LB film was formed by adsorbing the enzyme molecules onto a viologen monolayer using the electrostatic force. The proposed kinetics for irreversible inhibition of organophosphorus compounds on AChE agreed well with the experimental data. The surface topography of AChE-immobilized LB film was investigated by atomic force microscope (AFM). The immobilized AChE had the maximum activity at pH 7. The proposed biosensor could successfully detect the organophosphorus compounds up to 2 ppm and the response time to steady signal of the sensor was about 10 min.

Color image detection by biomolecular photoreceptor using bacteriorhodopsin-based complex LB films

A biomolecular photoreceptor consisting of bacteriorhodopsin (bR)-based complex Langmuir-Blodgett (LB) films was developed for color image detection. By mimicking the functions of the pigments in retina of human visual system, biomolecules with photoelectric conversion function were chosen and used as constituents for an artificial photoreceptor. bR and flavin were deposited onto the patterned (9-pixelized) ITO glass by LB technique. A 9-pixel biomolecular photoreceptor was fabricated with a sandwich-type structure of ITO/LB films/electrolyte gel/Pt. Since each functional molecule shows its own response characteristic according to the light illumination in the visible region, the simplified knowledge-based algorithm for interpretation of the incident light wavelength (color) was proposed based on the basic rule describing the relationship between the photoelectric response characteristics and the incident light wavelength. When simple color images were projected onto the photoreceptor, the primary colors in visible light region, red, green, and blue were clearly recognized, and the projected color images were fairly well reproduced onto the color monitor by the proposed photoreceptor with the knowledge-based algorithm. It is concluded that the proposed device has a capability of recognizing the color images and can be used as a model system to simulate the information processing function of the human visual system.

Visual information processing using bacteriorhodopsin-based complex LB films

Image extraction and visual information processing using bacteriorhodopsin (bR)-based bioelectronic devices is presented. Image extraction was achieved using a photoreceptor consisting of bR and spiropyran films. The undesired signals from the photoreceptor were automatically eliminated from the whole signal by spiropyran films acting as an optical noise filter that increases the target signal to an undesired signal ratio. For the information processing, the photoreceptor consisting of bR and lipid films deposited with different configurations was used and the target signals were processed to achieve the pattern recognition. The pattern recognition was based on not only the response variability of bacteriorhodopsin, induced by different film configurations, but also on the initial learning process. The input patterns were predicted by simple calculation with the known signals through the initial learning process.

Rectified photocurrent of molecular photodiode consisting of cytochrome c/GFP hetero thin films

Photoinduced electron transfer in the molecular electronic device consisting of protein-adsorbed hetero Langmuir-Blodgett (LB) film was investigated. Three kinds of functional molecules, cytochrome c, viologen, and green fluorescent protein (GFP) were used as an electron acceptor, a mediator, and a sensitizer, respectively. The hetero-LB film was fabricated by subsequently depositing cytochrome c and viologen onto the pretreated ITO or quartz glass. GFP adsorbed hetero-LB films were prepared by soaking the hetero-LB films into the buffer solution containing GFP. The MIM (metal/insulator/metal) structured molecular device was constructed by depositing aluminum onto the surface of the GFP-adsorbed hetero LB films. Due to the excitation by irradiation with a 460 nm monochromic light source, the photoinduced unidirectional flow of electrons in the MIM device could be achieved and was detected as photocurrents. The photoswitching function was achieved and the rectifying characteristic was observed in the molecular device. Based on the measurement of transient photocurrent of molecular device, the unidirectional flow of electrons was verified.

Tumor necrosis factor receptor superfamily 14 is involved in atherogenesis by inducing proinflammatory cytokines and matrix metalloproteinases

Tumor necrosis factor (TNF) receptor superfamily 14 (TNFRSF14) is the cellular receptor for TNF superfamily 14 (LIGHT). Immunohistochemical staining of human carotid atherosclerotic plaques revealed a high level of expression of the TNFRSF14 in regions rich in macrophages/foam cells. To investigate the role of TNFRSF14 in the functioning of monocytes in relation to atherogenesis, we have analyzed TNFRSF14 expression levels and cellular events after stimulation of TNFRSF14 in peripheral blood monocytes or the human macrophage-like cell line, THP-1. A high level of expression of TNFRSF14 was detected in activated monocytes, in macrophages derived from monocytes, and in THP-1 cells. Concomitant activation of THP-1 cells with interferon-gamma and immobilized anti-TNFRSF14 monoclonal antibody resulted in synergistic induction of proatherogenic cytokines, such as TNF-alpha and interleukin-8. Activation of THP-1 cells with immobilized anti-TNFRSF14 monoclonal antibody induced expression of matrix metalloproteinase (MMP)-1, MMP-9, MMP-13, and tissue inhibitors of metalloproteinase-1 and -2. Furthermore, immunohistochemical staining of atherosclerotic plaques with severe infiltration of foam cells revealed that the expression patterns of TNFRSF14 and MMP-1, -9, and -13 overlapped. Treatment of THP-1 cells with soluble LIGHT also caused induction of MMP-9 and interleukin-8. These data suggest that TNFRSF14 is involved in atherosclerosis via the induction of proatherogenic cytokines and decreasing plaque stability by inducing extracellular matrix-degrading enzymes.

Cloning of cDNAs encoding C-type lectins from Elapidae snakes Bungarus fasciatus and Bungarus multicinctus

A number of C-type lectins with various biological activities have been purified and characterized from Viperidae snake venoms. In contrast, only a few reports could be found in literature concerning the C-type lectins in Elapidae snake venoms. Based on the published cDNA sequences of C-type lectins from Viperidae snake venoms, oligonucleotide primers were designed and used to screen the cDNA libraries made from the venom glands of Bungarus fasciatus and Bungarus multicinctus. This allowed the cloning of three full length cDNAs encoding C-type lectins. The encoded proteins, named BFL-1, BFL-2 and BML, exhibit high degrees of sequence identities with Viperidae snake venom saccharide-binding lectins (around 60% with Trimeresurus stejnegeri venom lectin, Crotalus atrox venom lectin and Agkistrodon piscivorus venom lectin). They show much less identities with other venom C-type lectin-like proteins (around 30% with the platelet glycoprotein Ib-binding protein from Agkistrodon blomhoffi venom and the factor IX/X-binding protein from Trimeresurus flavoviridis venom). The cDNAs revealed that the precursors contain potential signal peptides characterized by a hydrophobic core. To our knowledge, these are the first cDNA cloning of group VII C-type lectins (Drickamer K. 1993. Prog. Nucleic Acid Res. Mol. Biol. 45, 207-232) from Elapidae snake venom glands.

Expression of Clostridium perfringens enterotoxin receptors claudin-3 and claudin-4 in prostate cancer epithelium

The mRNA for Rvp.1 (rat ventral prostate) increases in abundance before gland involution after androgen deprivation. Rvp.1 is homologous to CPE-R, the high-affinity intestinal epithelial receptor for Clostridium perfringens enterotoxin (CPE), and is sufficient to mediate CPE binding and trigger subsequent toxin-mediated cytolysis. Rvp.1 (claudin-3) and CPE-R (claudin-4) are members of a larger family of transmembrane tissue-specific claudin proteins that are essential components of intercellular tight junction structures regulating paracellular ion flux. However, claudin-3 and claudin-4 are the only family members capable of mediating CPE binding and cytolysis. The present study was designed to study the expression of claudin-3 and claudin-4 in human prostate tissue as potential targets for CPE toxin-mediated therapy for prostate cancer. On human multiple-tissue Northern blot analysis, mRNAs for both claudin-3 and claudin-4 were expressed at high levels in prostate tissue. In normal prostate tissue, expression of claudin-3 was localized exclusively within acinar epithelial cells by in situ mRNA hybridization. Compared with expression within prostate epithelial cells in surrounding normal glandular tissue, expression of claudin-3 mRNA remained high in the epithelium of prostate adenocarcinoma (10 of 10) and prostatic intraepithelial neoplasia (five of five). Prostate adenocarcinoma cells metastatic to bone were obtained from a patient with disease progression during antiandrogen therapy. These metastatic cells were prostate-specific antigen-positive by immunohistochemical staining and also expressed functional CPE receptors as measured by sensitivity to CPE-induced cell lysis. The persistent high level of claudin-3 expression in prostate adenocarcinoma and functional cytotoxicity of CPE in metastatic androgen-independent prostate adenocarcinoma suggests a new potential therapeutic strategy for prostate cancer.

GSTP1 CpG island hypermethylation is responsible for the absence of GSTP1 expression in human prostate cancer cells

GSTP1 CpG island hypermethylation is the most common somatic genome alteration described for human prostate cancer (PCA); lack of GSTP1 expression is characteristic of human PCA cells in vivo. We report here that loss of GSTP1 function may have been selected during the pathogenesis of human PCA. Using a variety of techniques to detect GSTP1 CpG island DNA hypermethylation in PCA DNA, we found only hypermethylated GSTP1 alleles in each PCA cell in all but two PCA cases studied. In these two cases, CpG island hypermethylation was present at only one of two GSTP1 alleles in PCA DNA. In one of the cases, DNA hypermethylation at one GSTP1 allele and deletion of the other GSTP1 allele were evident. In the other case, an unmethylated GSTP1 allele was detected, accompanied by abundant GSTP1 expression. GSTP1 CpG island DNA hypermethylation was responsible for lack of GSTP1 expression by LNCaP PCA cells: treatment of the cells with 5-azacytidine (5-aza-C), an inhibitor of DNA methyltransferases, reversed the GSTP1 promoter DNA hypermethylation, activated GSTP1 transcription, and restored GSTP1 expression. GSTP1 promoter activity, assessed via transfection of GSTP1 promoter-CAT reporter constructs in LNCaP cells, was inhibited by SssI-catalyzed CpG dinucleotide methylation. Remarkably, although selection for loss of GSTP1 function may be inferred for human PCA, GSTP1 did not act like a tumor suppressor gene, as LNCaP cells expressing GSTP1, either after 5-aza-C treatment or as a consequence of transfection with GSTP1 cDNA, grew well in vitro and in vivo. Perhaps, GSTP1 inactivation may render prostatic cells susceptible to additional genome alterations, caused by electrophilic or oxidant carcinogens, that provide a selective growth advantage.