Capsaicin Inhibited Aggressive Phenotypes through Downregulation of Tumor-Associated NADH Oxidase (tNOX) by POU Domain Transcription Factor POU3F2.

Capsaicin has been reported to preferentially inhibit the activity of tumor-associated NADH oxidase (tNOX), which belongs to a family of growth-related plasma membrane hydroquinone oxidases in cancer/transformed cells. The inhibitory effect of capsaicin on tNOX is associated with cell growth attenuation and apoptosis. However, no previous study has examined the transcriptional regulation of tNOX protein expression. Bioinformatic analysis has indicated that the tNOX promoter sequence harbors a binding motif for POU3F2, which is thought to play important roles in neuronal differentiation, melanocytes growth/differentiation and tumorigenesis. In this study, we found that capsaicin-mediated tNOX downregulation and cell migration inhibition were through POU3F2. The protein expression levels of POU3F2 and tNOX are positively correlated, and that overexpression of POU3F2 (and the corresponding upregulation of tNOX) enhanced the proliferation, migration and invasion in AGS (human gastric carcinoma) cells. In contrast, knockdown of POU3F2 downregulates tNOX, and the cancer phenotypes are affected. These findings not only shed light on the molecular mechanism of the anticancer properties of capsaicin, but also the transcription regulation of tNOX expression that may potentially explain how POU3F2 is associated with tumorigenesis.

DNA repair proteins as the targets for paroxetine to induce cytotoxicity in gastric cancer cell AGS.

To evaluate the potential anticancer effects of 1175 FDA-approved drugs, cell viability screening was performed using 25 human cancer cell lines covering 14 human cancer types. Here, we focus on the action of paroxetine, which demonstrated greater toxicity toward human gastric adenocarcinoma cell-line AGS cells compared with the other FDA-approved drugs, exhibiting an IC50 value lower than 10 µM. Evaluation of the underlying novel mechanisms revealed that paroxetine can enhance DNA damage in gastric cancer cells and involves downregulation of Rad51, HR23B and ERCC1 expression and function, as well as nucleotide shortage. Enhancement of autophagy counteracted paroxetine-induced apoptosis but did not affect paroxetine-induced DNA damage. Paroxetine also enhanced ROS generation in AGS cells, but a ROS scavenger did not improve paroxetine-mediated DNA damage, apoptosis, or autophagy, suggesting ROS might play a minor role in paroxetine-induced cell toxicity. In contrast, paroxetine did not enhance DNA damage, apoptosis, or autophagy in another insensitive gastric adenocarcinoma cell-line MKN-45 cells. Interestingly, co-administration of paroxetine with conventional anticancer agents sensitized MKN-45 cells to these agents: co-treated cells showed increased apoptosis relative to MKN-45 cells treated with the anticancer agent alone. Unequivocally, these data suggest that for the first time that paroxetine triggers cytotoxicity and DNA damage in AGS cells at least partly by reducing the gene expression of Rad51, HR23B, and ERCC1. Our findings also suggest that paroxetine is a promising candidate anticancer agent and/or chemosensitizing agent for use in combination with other anticancer drugs in cancer therapy. The molecular mechanisms underlying the anticancer activity of co-treatment with paroxetine and chemotherapy appear to be complex and are worthy of further investigation.

Population-specific functional variant of the TPH2 gene 2755C>A polymorphism contributes risk association to major depression and anxiety in Chinese peripartum women.

The rate-limiting enzyme of serotonin biosynthesis, tryptophan hydroxylase 2 (TPH2), is one of the most promising candidate genes for psychiatric disorders. Although evidence strongly suggests that the TPH2 is significant in the etiology of major depression and anxiety disorder, whether it also contributes to the etiology of peripartum major depression and anxiety disorder, a specific subtype influenced considerably by other environmental factors like hormones, is unclear. This study investigated the role of TPH2 in the etiology of peripartum major depression and anxiety disorder in a Han Chinese population in Taiwan. Six single nucleotide polymorphisms were selected from previously profiled genetic information of TPH2 in Han Chinese. A cohort of postpartum Chinese women that included 117 patients with major depression, anxiety disorder, or both and 83 healthy controls were genotyped with selected TPH2 markers. The TPH2 2755A allele was found only in women with peripartum major depression and anxiety disorder (p = 0.043) and exhibited a dominant gene action (p = 0.038) with an estimated disease risk of 1.73. Although the sample size is small, results from this study suggest that the TPH2 C2755A polymorphism may represent a population-specific risk factor for peripartum major depression and anxiety disorder, perhaps by interacting with hormones.

Association analysis of monoamine oxidase A gene and bipolar affective disorder in Han Chinese.

BACKGROUND: Monoamine oxidase A (MAOA) is a mitochondrial enzyme involved in degrading several different biological amines, including serotonin. Although several pieces of evidence suggested that MAOA is important in the etiology of bipolar affective disorder (BPD), associations for markers of the MAOA gene with BPD were not conclusive and the association has not been investigated in Taiwanese population. This study was designed to illustrate the role of MAOA in the etiology of BPD in Han Chinese. METHODS: Two markers, a dinucleotide polymorphism in exon 2 and a functional uVNTR on the promoter of the MAOA gene, were used to study the genetic association in 108 unrelated patients with BPD and 103 healthy controls. Allelic distributions of two polymorphisms were analyzed and, caused the MAOA located at X chromosome, haplotype association was performed using haplotype unambiguously assigned in male participants. RESULTS: While no difference in allelic distributions of two MAOA polymorphisms was found, the risk haplotype 114S was associated with BPD in male patients (P = 0.03). The significance, however, was not found in female patients with 114S haplotype. CONCLUSION: Results from this study suggest that MAOA may have a gender-specific and small effect on the etiology of BPD in Taiwan. Due to the limited sample size, results from this study need to be confirmed in replicates.

Association of functional polymorphisms of the human tryptophan hydroxylase 2 gene with risk for bipolar disorder in Han Chinese.

CONTEXT: The tryptophan hydroxylase 2 (TPH2) gene encodes the first (also the rate-limiting) enzyme in the serotonin biosynthetic pathway. Despite reports of possible associations between polymorphisms in human TPH2 and many psychiatric disorders, including bipolar disorder (BPD), the functional effect and susceptibility loci of such polymorphisms for BPD have not yet been identified. OBJECTIVES: To examine the association of TPH2 with BPD and to identify the functional variants that may be involved in the pathophysiological development of BPD. Design, Setting, and Patients We systematically screened all exons and promoters of the TPH2 gene in Han Chinese subjects to identify sequence variants. Association tests were conducted in 105 cases and 106 control subjects using single-locus, linkage disequilibrium, and haplotype analyses. Two promoter and one exon 2 single-nucleotide polymorphisms were examined for their functional role using a reporter gene system and enzyme activity assay, respectively. Additional statistical analysis was performed to study the interaction between the 2 TPH genes in 205 study participants with TPH1 and TPH2 genotype data. RESULTS: Significant haplotype association of TPH2 polymorphisms and BPD was identified (P < .001). In addition, allelic alteration of polymorphisms in the promoter region and exon 2 of TPH2 caused noteworthy functional losses in promoter and enzyme activities, respectively, indicating the potential susceptibility loci for BPD. We found that the odds ratio changed from 3.73 of the TAG haplotype to 4.81 or 1.68, depending on the combined effect of both TPH genotypes. These data suggested an interaction between the 2 TPH genes to confer a risk for BPD. CONCLUSIONS: This study supports the involvement of TPH2 in the etiology of BPD, and the functional single-nucleotide polymorphisms identified herein might be the susceptibility loci for BPD. Although the interaction between the 2 TPH genes merits further investigation, our findings suggest that the interactive effect should be considered in future studies of serotonin-related disorders.

NTF3 Is a Novel Target Gene of the Transcription Factor POU3F2 and Is Required for Neuronal Differentiation.

POU-homeodomain transcription factor POU3F2 is a critical transcription factor that participates in neuronal differentiation. However, little is known about its downstream mediators. Here genome-wide analyses of a human neuronal differentiation cell model, NT2D1, suggested neurotrophin-3 (NTF3), a key mediator of neuronal development during the early neurogenic period, as a putative regulatory target of POU3F2. Western blot, cDNA microarray, and real-time quantitative PCR analyses showed that POU3F2 and NTF3 were upregulated during neuronal differentiation. Next-generation-sequence-based POU3F2 chromatin immunoprecipitation-sequencing and genome-wide in silico prediction demonstrated that POU3F2 binds to the NTF3 promoter during neuronal differentiation. Furthermore, unidirectional deletion or mutation of the binding site of POU3F2 in the NTF3 promoter decreased promoter-driven luciferase activity, indicating that POU3F2 is a positive regulator of NTF3 promoter activity. While NTF3 knockdown resulted in decreased viability and differentiation of NT2D1 cells, and POU3F2 knockdown downregulated NTF3 expression, recombinant NTF3 significantly rescued viable neuronal cells from NTF3- or POU3F2-knockdown cell cultures. Moreover, immunostaining showed colocalization of POU3F2 and NTF3 in developing mouse neurons. Thus, our data suggest that NTF3 is a novel target gene of POU3F2 and that the POU3F2/NTF3 pathway plays a role in the process of neuronal differentiation.

Polymorphism screening and haplotype analysis of the tryptophan hydroxylase gene (TPH1) and association with bipolar affective disorder in Taiwan.

BACKGROUND: Disturbances in serotonin neurotransmission are implicated in the etiology of many psychiatric disorders, including bipolar affective disorder (BPD). The tryptophan hydroxylase gene (TPH), which codes for the enzyme catalyzing the rate-limiting step in serotonin biosynthetic pathway, is one of the leading candidate genes for psychiatric and behavioral disorders. In a preliminary study, we found that TPH1 intron7 A218C polymorphism was associated with BPD. This study was designed to investigate sequence variants of the TPH1 gene in Taiwanese and to test whether the TPH1 gene is a susceptibility factor for the BPD. METHODS: Using a systematic approach, we have searched the exons and promoter region of the TPH1 gene for sequence variants in Taiwanese Han and have identified five variants, A-1067G, G-347T, T3804A, C27224T, and A27237G. These five variants plus another five taken from the literature and a public database were examined for an association in 108 BPD patients and 103 controls; no association was detected for any of the 10 variants. RESULTS: Haplotype constructions using these 10 SNPs showed that the 3 most common haplotypes in both patients and controls were identical. One of the fourth common haplotype in the patient group (i.e. GGGAGACCCA) was unique and showed a trend of significance with the disease (P = 0.028). However, the significance was abolished after Bonferroni correction thus suggesting the association is weak. In addition, three haplotype-tagged SNPs (htSNPs) were selected to represent all haplotypes with frequencies larger than 2% in the Taiwanese Han population. The defined TPH1 htSNPs significantly reduce the marker number for haplotype analysis thus provides useful information for future association studies in our population. CONCLUSION: Results of this study did not support the role of TPH1 gene in BPD etiology. As the current studies found the TPH1 gene under investigation belongs to the peripheral serotonin system and may link to a cardiac dysfunction phenotype, a second TPH gene that functions predominantly in the brain (i.e., nTPH or TPH2) should be the target for the future association study.