A negative regulatory element in the bcl-2 5'-untranslated region inhibits expression from an upstream promoter

The Investigation of the Association Between the Bcl-2 3'-UTR rs1564483 Polymorphism and miR-296-3p in the Development of Breast and Gastric Cancers

BACKGROUND

B-cell leukemia/lymphoma 2 (Bcl-2) gene regulates carcinogenesis by inhibiting apoptosis. This study evaluated the association of Bcl-2 3'-untranslated regions (3' UTR) rs1564483 polymorphism and miR-296-3p with the development of breast and gastric cancers.

METHODS

A microarray analysis was performed on the Genomic Spatial Event (GSE)29431 and GSE161533 datasets for breast and gastric cancers. Blood samples were taken from 222 (111 patients and 111 controls) and 210 (84 patients and 126 controls) individuals for breast and gastric cancers, respectively. Genomic DNA was extracted from the blood samples and genotyping was performed using real-time polymerase chain reaction (RT-PCR), followed by examining the high-temperature melting curve. Statistical analysis was conducted to examine the potential correlation between the rs1564483 polymorphism and the risk of breast and gastric cancers concerning pathological characteristics.

RESULTS

The results of the microarray showed that the Bcl-2 gene was up-regulated in gastric cancer (logFC [log fold change]: 0.65, adjusted P < .05). Clinical outcome showed no notable relationship between the rs1564483 polymorphism and breast cancer risk; however, for gastric cancer, it identified a large difference between healthy controls and patients for an allelic frequency of rs1564483 (P ⩽ .001). Moreover, an assay of different models (dominant, recessive, and co-dominant) showed a significant association between the AG genotype between control and gastric cases (Pearson chi-square test, P = .046). In addition, the prevalence of the AG genotype was greater in persons under the age of 45 and in patients with H. pylori infection (P ⩽ .001). The AG genotype was not related to smoking, although the AA genotype was associated with increased cancer incidence in smokers (P ⩽ .001).

CONCLUSIONS

In silico studies and calculations of the ΔG binding of micro ribonucleic acid (miRNA) hsa-miR-296-3p to the mutant and wild alleles of the rs15644833 single nucleotide polymorphism (SNP) have revealed that Bcl-2 mRNA expression in gastric cancer decreases, thus confirming the tumor suppressor role of the Bcl-2 gene.

G-quadruplexes in cancer-related gene promoters: from identification to therapeutic targeting

INTRODUCTION

Guanine-rich DNA sequences can fold into four-stranded noncanonical secondary structures called G-quadruplexes (G4s) which are widely distributed in functional regions of the human genome, such as telomeres and gene promoter regions. Compelling evidence suggests their involvement in key genome functions such as gene expression and genome stability. Notably, the abundance of G4-forming sequences near transcription start sites suggests their potential involvement in regulating oncogenes.

AREAS COVERED

This review provides an overview of current knowledge on G4s in human oncogene promoters. The most representative G4-binding ligands have also been documented. The objective of this work is to present a comprehensive overview of the most promising targets for the development of novel and highly specific anticancer drugs capable of selectively impacting the expression of individual or a limited number of genes.

EXPERT OPINION

Modulation of G4 formation by specific ligands has been proposed as a powerful new tool to treat cancer through the control of oncogene expression. Actually, most of G4-binding small molecules seem to simultaneously target a range of gene promoter G4s, potentially influencing several critical driver genes in cancer, thus producing significant therapeutic benefits.

Metformin attenuates symptoms of osteoarthritis: role of genetic diversity of Bcl2 and CXCL16 in OA

OBJECTIVE

This study aimed to evaluate the effectiveness of metformin versus placebo in overweight patients with knee osteoarthritis (OA). In addition, to assess the effects of inflammatory mediators and apoptotic proteins in the pathogenesis of OA, the genetic polymorphisms of two genes, one related to apoptosis (rs2279115 of Bcl-2) and the other related to inflammation (rs2277680 of CXCL-16), were investigated.

METHODS

In this double-blind placebo-controlled clinical trial, patients were randomly divided to two groups, one group receiving metformin (n = 44) and the other one receiving an identical inert placebo (n = 44) for 4 consecutive months (starting dose 0.5 g/day for the first week, increase to 1 g/day for the second week, and further increase to 1.5 g/day for the remaining period). Another group of healthy individuals (n = 92) with no history and diagnosis of OA were included in this study in order to evaluate the role of genetics in OA. The outcome of treatment regimen was evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire. The frequency of variants of rs2277680 (A181V) and rs2279115 (938C>A) were determined in extracted DNAs using PCR-RFLP method.

RESULTS

Our results indicated an increase in scores of pain (P ≤ 0.0001), activity of daily living (ADL) (P ≤ 0.0001), sport and recreation (Sport/Rec) (P ≤ 0.0001), and quality of life (QOL) (P = 0.003) and total scores of the KOOS questionnaire in the metformin group compared to the placebo group. Susceptibility to OA was associated with age, gender, family history, CC genotype of 938C>A (Pa = 0.001; OR = 5.2; 95% CI = 2.0-13.7), and GG+GA genotypes of A181V (Pa = 0.04; OR = 2.1; 95% CI = 1.1-10.5). The C allele of 938C>A (Pa = 0.04; OR = 2.2; 95% CI = 1.1-9.8) and G allele of A181V (Pa = 0.02; OR = 2.2; 95% CI = 1.1-4.8) were also associated with OA.

CONCLUSION

Our findings support the possible beneficial effects of metformin on improving pain, ADL, Sport/Rec, and QOL in OA patients. Our findings support the association between the CC genotype of Bcl-2 and GG+GA genotypes of CXCL-16 and OA.

Evaluation of Bax and BCL 2 Genes Polymorphisms in Iraqi Women with Breast Cancer

The present study aimed to examine the polymorphism -938C > A of BCL-2 gene and promoter -248G>A in the Bax gene, as well as their relationship with specific clinical-pathological characteristics, in patients with breast cancer. Blood samples were obtained from 70 patients who had been diagnosed with breast cancer and 34 healthy women as the control group. Polymorphic analysis was performed using the polymerase chain reaction-restriction fragment length polymorphism assay. Anthropometric data were assessed. Estrogen receptor (ER), human epidermal growth factor receptor 2 (Her-2),  and progesterone receptor (PR) were measured by immunohistochemistry. The data of age and body mass index (BMI) demonstrated no significant variations between the two groups (P>0.05). The results of HER-2 revealed that 42.86% of breast cancer patients reflected positively for Her-2/neu expression, while 24.29% reflected negative results of Her-2/neu. Moreover, the results of ER revealed that 42.86% and 28.57% of subjects were positive and negative ER, respectively; moreover, the missing data was 28.57%. In addition, the results of PR indicated that 35.71% of patients (25/70) were positive for PR, while 28.57% reflected negative results, and the missing results were 35.71%. The genotype and allele frequencies of BCL-2(-938C>A) were not statistically significant in women with breast cancer and the control group (P=0.574, P=0.533) for heterozygous and recessive models, respectively. The genotype of BCL-2(-938C>A) in control and patients in codominant, dominant, recessive, and additive models demonstrated no significant variations of all genotypes in all groups. Genotypes and allele frequencies for Bax (-248G>A) in patients with breast cancer and control indicated that the frequencies of GG, AG, and AA genotypes in cases were 16.67%, 3.33%, and 80 %, while in controls, these values were 3.23 %, 58.06 %, and 3.23 %, respectively. The heterozygous genotype (AG) in the codominant model was OR=36.00 (95% CI 4.5608 - 284.1608; P=0.0007). In comparison with the wild type (GG), there was a 36-fold increase in the risk of breast cancer. Furthermore, the findings of this study revealed a significant correlation between Bax (-248G>A) polymorphism and breast cancer risk under the dominant and overdominant (OR=6.33; 95% CI 2.2604 -17.7452; P=0.0004, and OR=40.154; 95% CI 5.1365 - 313.8949; P=0.0004, respectively. The recessive model revealed that there was a decreased risk of breast cancer (OR= 0.167; 95% CI 0.0303 to 0.9168; P=0.039). Based on the results, it can be concluded that there were no significant variations in BCL-2 (-938C>A) polymorphism of all genotypes models when breast cancer women are compared with healthy ones. In a similar vein, there was no significant association between the BCL-2 (-938C>A) polymorphism and breast cancer risk under dominant, codominant, or recessive models.

Hodgkin Lymphoma: A Special Microenvironment

Classical Hodgkin's lymphoma (cHL) is one of the most particular lymphomas for the few tumor cells surrounded by an inflammatory microenvironment. Reed-Sternberg (RS) and Hodgkin (H) cells reprogram and evade antitumor mechanisms of the normal cells present in the microenvironment. The cells of microenvironment are essential for growth and survival of the RS/H cells and are recruited through the effect of cytokines/chemokines. We summarize recent advances in gene expression profiling (GEP) analysis applied to study microenvironment component in cHL. We also describe the main therapies that target not only the neoplastic cells but also the cellular components of the background.

Association of genetic polymorphism of BCL-2 (rs2279115) with susceptibility to HCV-related hepatocellular carcinoma

Hepatitis C virus (HCV) infection is the main risk factor for chronic hepatitis (CHC), liver cirrhosis, and hepatocellular carcinoma (HCC). B cell lymphoma-2 (BCL-2) prevents apoptosis, and its overexpression could promote cancer cell survival. The purpose of this study is to evaluate the association of Bcl-2 gene polymorphism (rs2279115) and HCV-related HCC susceptibility. Two hundred and seventy individuals included in this case-control were divided into three groups. Group I: It included 90 apparently healthy subjects as control. Group II: It includes 90 patients with chronic HCV hepatitis. Group III: It includes 90 patients with HCC with positive HCV. Bcl-2 gene polymorphism (rs2279115) C > A genotypes by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). There are significantly higher incidence of CA and AA genotypes in HCV patients with HCC compared with those without HCC (OR 2.3, %CI (1.2-4.6), P = 0.01 and OR 5.7, %CI (2.4-13.8), respectively) and compared with control group (OR 2.9, %CI (1.5-5.8), P = 0.002 and OR 7.1, %CI (2.9-17.4), P < 0.001, respectively), while no significant difference between the control and HCV patients without HCC groups (OR 1.2, %CI (0. 7-2.4), P = 0.48, for CA, and OR 1.2, %CI (0.4-3.3), P = 0.67, for AA).The frequency of A allele was highly significantly overrepresented in the HCC group in comparison to HCV group (53.3% versus 30.6%, P < 0.001) and control group (53.3% versus 27.2%, P < 0.001) but no significant difference (p = 0.49) between control group and HCV patients. This study demonstrated that Bcl-2 gene polymorphism (rs2279115) was associated with increased susceptibility to HCV-related HCC.

Oxidative lesions modulate G-quadruplex stability and structure in the human BCL2 promoter

Misregulation of BCL2 expression has been observed with many diseases and is associated with cellular exposure to reactive oxygen species. A region upstream of the P1 promoter in the human BCL2 gene plays a major role in regulating transcription. This G/C-rich region is highly polymorphic and capable of forming G-quadruplex structures. Herein we report that an oxidative event simulated with an 8-oxo-7,8-dihydroguanine (^oxoG) substitution within a long G-tract results in a reduction of structural polymorphism. Surprisingly, ^oxoG within a 25-nt construct boosts thermal stability of the resulting G-quadruplex. This is achieved by distinct hydrogen bonding properties of ^oxoG, which facilitate formation of an antiparallel basket-type G-quadruplex with a three G-quartet core and a G·^oxoG·C base triad. While ^oxoG has previously been considered detrimental for G-quadruplex formation, its stabilizing effect within a promoter described in this study suggests a potential novel regulatory role of oxidative stress in general and specifically in BCL2 gene transcription.

Alpha-fetoprotein accelerates the progression of hepatocellular carcinoma by promoting Bcl-2 gene expression through an RA-RAR signalling pathway

Previous studies have found that alpha-fetoprotein (AFP) can promote the proliferation of hepatoma cells and accelerate the progression of hepatocellular carcinoma (HCC). However, the exact mechanism of action remains unclear. Recent bioinformatics studies have predicted the possible interaction between AFP and retinoic acid receptors (RARs). Thus, the purpose of this study was to investigate the molecular mechanism through which AFP promotes tumour cell proliferation by interfering with the RA-RAR signal pathway. Our data indicated that AFP could significantly promote the proliferation and weaken ATRA-induced apoptosis of hepatoma cells. Besides, cytoplasmic AFP interacts with RAR, disrupting its entrance into the nucleus, which in turn affects the expression of the Bcl-2 gene. In addition, knockdown of AFP in HepG2 cells was synchronously associated with an incremental increase of RAR binding to DNA, as well as down-regulation of Bcl-2; the opposite effect was observed in AFP gene-transfected HLE cells. Moreover, a similar effect of AFP was detected in tumour tissues with high serum AFP, but not in adjacent non-cancerous liver tissues, or HCC tissues with low serum AFP levels. These results indicate that AFP acts as signalling molecule and prevents RAR from entering into the nucleus by interacting with RAR, thereby promoting the expression of Bcl-2. Our data reveal a novel mechanism through which AFP regulates Bcl-2 expression and further suggest that AFP may be used as a novel target for treating HCC.

PRMT2 accelerates tumorigenesis of hepatocellular carcinoma by activating Bcl2 via histone H3R8 methylation

Protein arginine methyltransferases (PRMTs) have been implicated in the development of various cancers. PRMT2, a member of the type I PRMT family, is overexpressed in multiple tumors. However, the expression and role of PRMT2 in hepatocellular carcinoma (HCC) have not been studied. Here, we discovered that PRMT2 expression is elevated in HCC tissues compared to the corresponding non-tumor tissues, and PRMT2 overexpression is an independent predictor of poor prognosis in HCC patients. Depletion of PRMT2 in HCC cell lines inhibited their cell growth and induced apoptosis. Mechanistic investigations showed that PRMT2 is responsible for H3R8 asymmetric methylation (H3R8me2a). H3R8me2a enrichment at the Bcl2 promoter increases its accessibility to STAT3, promoting Bcl2 gene expression. In addition, our results confirmed that the catalytically inactive mutant of PRMT2 or the type I PRMT inhibitor MS023 impaired the pro-tumorigenic functions of PRMT2 in HCC cells. Overall, our findings showed that PRMT2 functions as an oncogenic gene in HCC, revealing its potential as a novel therapeutic target in HCC.

Genetic and epigenetic analysis of the BAX and BCL2 in the placenta of pregnant women complicated by preeclampsia

The current study examined the effects of BAX and BCL2 polymorphisms and methylation as well as mRNA expression on susceptibility to PE. After delivery, the placentas were collected from 92 women with PE, as well as 106 normotensive pregnant women. The BAX rs4645878 and BCL2 rs2279115 polymorphisms were genotyped by the PCR-RFLP method. Methylation-specific PCR (MSP) was used for analysis of promoter methylation. mRNA expression was assayed by Quantitative RT-PCR. In addition, in silico analysis was performed by bioinformatics tools. There was no relationship between PE and placental BAX rs4645878 and BCL2 rs2279115 polymorphisms. The groups were not significantly different regarding the promoter methylation of BAX gene. Nonetheless, the MM status of BCL2 promoter had a significantly higher frequency in the PE group and was associated with 2.7-fold higher risk of PE (OR = 2.7, 95% CI = 1.3-5.6; P = 0.01). The relative mRNA expression of BCL2 was decreased in the placentas of PE women (P < 0.0001). The expression of BAX gene was not significantly different between the two groups. There was no association between placental BAX rs4645878 and BCL2 rs2279115 polymorphisms and mRNA expression levels. In silico analysis indicated that BAX rs4645878 and BCL2 rs2279115 polymorphisms were located in the core recognition site of different transcription factors and these substitutions of wild allele resulted in the loss and/ or change of these binding sites and subsequently may alter BCL2 and BAX expression. This study showed that the BAX and BCL2 polymorphisms and BAX promoter methylation were not associated with PE risk. The BCL2 promoter methylation was associated with lower BCL2 expression and higher PE susceptibility.

Development of Dual Functional Nucleic Acid Delivery Nanosystem for DNA Induced Silencing of Bcl-2 Oncogene

Introduction

Cancer treatment using functionalized vehicles in order to block involved genes has attracted a remarkable interest. In this study, we investigated the cellular uptake and cytotoxic effects of three sizes of anti Bcl-2 DNAi-conjugated gold nanoparticles by MCF-7 cells.

Methods

Three different sizes of gold nanoparticles were synthesized by citrate reduction method and after characterization, the nanoparticles were functionalized by Bcl-2 targeted DNAi. Cell internalization of the nanoparticles was analyzed by atomic absorption spectroscopy and light microscopy. The cytotoxic effects of the nanoparticles were investigated by MTT assay, flow cytometry and RT-PCR of the target gene.

Results

While poor cell internalization of bare gold nanoparticles was observed, the results demonstrated that cellular uptake of DNAi-conjugated gold nanoparticles is completely size-dependent, and the largest nanoparticle (~42 nm) revealed the highest internalization rate compared to other sizes (~14 and ~26 nm). Experimental findings showed that the DNAi-conjugated gold nanoparticles induced apoptotic pathway by silencing of the targeted Bcl-2 gene. In addition, supplementary theoretical studies demonstrated that the 42 nm DNAi-conjugated gold nanoparticles have great photothermal conversion efficiency for treatment under external illumination and these nanoparticles can be induced further cytotoxic effect by approximately 10°C temperature elevations.

Conclusion

Remarkable photothermal properties of DNAi-conjugated 42 nm Au-NPs in parallel with their high cell internalization and cytotoxic effects introduce them as potential dual functional anticancer nanosystems.

Transcriptional regulation of Bcl-2 gene by the PR/SET domain family member PRDM10

Bcl-2 (B-cell lymphoma 2) protein is localized in the outer membrane of mitochondria, where it plays an important role in promoting cellular survival and inhibiting the actions of pro-apoptotic proteins. PRDM10 is a member of the PR/SET family of epigenetic regulators and may play a role in development and cell differentiation. Here we show that human PRDM10 contributes to the transcriptional regulation of human Bcl-2 gene. We found that PRDM10-depletion in human cells reduced the expression of Bcl-2 protein and over-expression of PRDM10 promoted Bcl-2 protein expression. Furthermore, luciferase reporter activity of Bcl-2 gene P1 promoter was significantly increased in cells co-transfected with PRDM10, and PRDM10 was able to bind to the Bcl-2 P1 promoter in vivo. Using The Cancer Genome Atlas (TCGA) data set, we found weak positive correlation between PRDM10 and Bcl-2 in several cancer types including cancers of the breast, colon, and lung tissues. These data identify a novel function for PRDM10 protein and provide insights on the transcriptional control of Bcl-2 expression.

Recent Progress of Targeted G-Quadruplex-Preferred Ligands Toward Cancer Therapy

A G-quadruplex (G4) is a well-known nucleic acid secondary structure comprising guanine-rich sequences, and has profound implications for various pharmacological and biological events, including cancers. Therefore, ligands interacting with G4s have attracted great attention as potential anticancer therapies or in molecular probe applications. To date, a large variety of DNA/RNA G4 ligands have been developed by a number of laboratories. As protein-targeting drugs face similar situations, G-quadruplex-interacting drugs displayed low selectivity to the targeted G-quadruplex structure. This low selectivity could cause unexpected effects that are usually reasons to halt the drug development process. In this review, we address the recent research on synthetic G4 DNA-interacting ligands that allow targeting of selected G4s as an approach toward the discovery of highly effective anticancer drugs.

Correlation between Bax gene polymorphisms and esophagus cancer

The present study investigated the association between the G(-248)A single nucleotide polymorphism (SNP) in the promoter region of B-cell lymphoma 2 (Bcl-2) associated X protein (Bax), which is a pro-apoptosis gene and the clinicopathological parameters and prognosis of patients with esophagus cancer. Three genotypes (AA, AG and GG) of Bax G(-248)A SNP were detected in 75 patients with esophageal squamous cell carcinoma (ESCC) via polymerase chain reaction-restricted fragment length polymorphism (PCR-RFLP). The expression of Bax in tumor tissues from 75 patients with ESCC and 30 para-carcinoma normal tissues were detected via immunohistochemistry. The association between the Bax protein expression and the Bax gene polymorphism was analyzed via the χ2 test. The clinical data of patients was collected and the association between Bax gene polymorphism and the pathological parameters and the prognosis of patients with ESCC was analyzed. The PCR-RFLP results revealed that the number of cases and the distribution frequencies of GG, AG and AA genotypes of Bax polymorphism in patients with ESCC were 50 (66.67%), 16 (21.33%) and 9 (12%), respectively. The immunohistochemical results revealed that the positive expression rate of Bax in ESSC tissues was 42.67%. Bax protein expression was associated with the Bax gene polymorphism, which was associated with outer membrane infiltration, differentiation degree, lymphatic metastasis and the clinical staging of patients. The overall 5-year survival rate of patients was 38.6% (29/75). The survival analyses revealed that the prognosis of patients with AG+AA genotypes was favorable, while that of patients with GG genotype was poor. Bax gene polymorphism was associated with Bax gene expression, tumor staging and lymphatic metastasis in patients with ESCC, which is an influencing factor for the overall survival rate and may be used as a reference index for the prognosis evaluation of patients with ESCC.

Functional BCL-2 rs2279115 Promoter Noncoding Variant Contributes to Glioma Predisposition, Especially in Males

As a crucial oncogene, B cell lymphoma-2 (BCL-2) could promote cancer cell survival by inhibiting apoptosis via suppressing activation of proapoptotic proteins, such as BAX and BAK. There is a functional rs2279115 genetic polymorphism locating in BCL-2 promoter and deregulating BCL-2 expression. However, it is still largely undefined how BCL-2 rs2279115 promoter noncoding genetic variant is involved in glioma development. We examined the association between BCL-2 rs2279115 and glioma risk using a case-control approach. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression adjusted by age and sex. Our results demonstrated that BCL-2 rs2279115 was significantly associated with glioma risk. The odd of individuals harboring A allele (CA + AA genotype) was 0.50 (95% CI = 0.39-0.64, p = 1.0 × 10^-7) compared with CC genotype carriers. Stratification analyses by sex elucidated that BCL-2 rs2279115 was significantly associated with glioma risk in males (OR = 0.41, 95% CI = 0.30-0.58, p = 1.0 × 10^-7), but not in females (p > 0.05). In summary, our results indicate that the functional BCL-2 rs2279115 genetic variant contributes to glioma predisposition and suggest prevalent involvement of regulatory genetic variations in glioma development.

Fluorescence-based tools to probe G-quadruplexes in cell-free and cellular environments

Biophysical and biochemical investigations provide compelling evidence connecting the four-stranded G-quadruplex (GQ) structure with its role in regulating multiple cellular processes. Hence, modulating the function of GQs by using small molecule binders is being actively pursued as a strategy to develop new chemotherapeutic agents. However, sequence diversity and structural polymorphism of GQs have posed immense challenges in terms of understanding what conformation a G-rich sequence adopts inside the cell and how to specifically target a GQ motif amidst several other GQ-forming sequences. In this context, here we review recent developments in the applications of biophysical tools that use fluorescence readout to probe the GQ structure and recognition in cell-free and cellular environments. First, we provide a detailed discussion on the utility of covalently labeled environment-sensitive fluorescent nucleoside analogs in assessing the subtle difference in GQ structures and their ligand binding abilities. Furthermore, a detailed discussion on structure-specific antibodies and small molecule probes used to visualize and confirm the existence of DNA and RNA GQs in cells is provided. We also highlight the open challenges in the study of tetraplexes (GQ and i-motif structures) and how addressing these challenges by developing new tools and techniques will have a profound impact on tetraplex-directed therapeutic strategies.

Genetic polymorphisms of Bcl-2 promoter in cancer susceptibility and prognosis: a meta-analysis

Bcl-2 is critical for tumorigenesis. However, previous studies on the association of Bcl-2 promoter polymorphisms with predisposition to different cancer types are somewhat contradictory. Therefore, we performed this meta-analysis regarding the relationship between Bcl-2 promoter single nucleotide polymorphisms (SNPs) and cancer susceptibility and prognosis. Up to August 2016, 32 original publications were identified covering two Bcl-2 promoter SNPs (rs2279115 and rs1801018). Our results showed statistically significant association between rs2279115 and cancer susceptibility and prognosis in all four genetic models but not in rs1801018. Subgroups analysis indicated that rs2279115 was associated with a significantly higher risk of cancer susceptibility in Asia but not in Caucasian. Furthermore, rs2279115 was associated with a significantly higher risk in digestive system cancer and endocrine system cancer but not in breast cancer, respiratory cancer and hematopoietic cancer. Simultaneously, rs2279115 was correlated with a significantly higher risk of cancer prognosis in Asia but not in Caucasian. Considering these promising results, rs2279115 may be a tumor marker for cancertherapy in Asia. Sensitivity analysis show four gene model were stable, and no publication bias was observed in all four gene model. Large sample size, different ethnic population and different cancer type are warranted to validate this association.

Association of the AA genotype of the BCL2 (–938C>A) promoter polymorphism with better survival in ovarian cancer

Background

Bcl-2 plays a key role in the regulation of apoptosis. Recently, a novel regulatory single nucleotide polymorphism (–938C>A) in the inhibitory P2 BCL2 promoter was described. In this study we investigated its potential association with survival in epithelial ovarian cancer.

Experimental design

Patients (n=110) with primary epithelial ovarian cancer were retrospectively genotyped by pyrosequencing.

Results

Genotype distribution was not significantly different between 110 ovarian cancer patients and 120 healthy controls, suggesting that genotypes of this polymorphism do not increase the susceptibility to ovarian cancer. Kaplan-Meier curves showed a significant association of the AA genotype with increased survival (p=0.002). Multivariate analysis revealed that the BCL2–938AC/CC genotype (hazard ratio 4.5; p=0.003) was an independent prognostic factor compared to other prognostic factors such as age, histological grade or tumor stage.

Conclusion

The results suggest a role for the BCL2-938C>A polymorphism as a marker for survival in patients with epithelial ovarian cancer.

Polymorphism in apoptotic BAX (-248G>A) gene but not in anti-apoptotic BCL2 (-938C>A) gene and its protein and mRNA expression are associated with cervical intraepithelial neoplasia

HPV is associated with cervical cancer and plays a crucial role in tumor formation. Apoptosis is regulated by different pathways involving genes that either promote (BCL2 gene) or inhibit (BAX gene) cell death. Our goal was to determine whether the BCL2-938C>A (rs2279115) and BAX-248G>A (rs4645878) single nucleotide polymorphisms (SNPs) are associated with squamous intraepithelial neoplasia (SIL) risk, and whether their phenotypic expression was impaired in these lesions. Two hundred and thirty-one cases showing SIL were classified as low SIL (LSIL, n = 101) or high SIL (HSIL, n = 130), and control subjects (n = 266) with no gynecologically proven SIL were recruited. No statistical difference in the genotype and allelic frequency of the BCL-2-938C>A polymorphism was observed among the groups. BCL2-938C/A and A/A homozygotes carriers had higher distribution of BCL-2-expressing cells in stroma in the SIL group. BCL2 mRNA-expression was not correlated with BCL2-938C>A SNPs in both groups. We did find a strong association of the BAX GG genotype and risk for SIL. No difference was observed between LSIL and HSIL groups. In BAX-248G/A and A/A homozygote carriers, the number of BAX-expressing cells was lower the epithelium area in SIL. However, mRNA expression was higher in SIL patients than in the control group. In conclusion, our data provide evidence that allele G carriers in the BAX-248G>A promoter SNP may influence the development of SIL. However, this genotype does not influence the SIL outcome. Additionally, we suggest a possible role of HPV infection in the inhibition of the expression of BAX protein, decreasing cell death, and favoring cervical carcinogenesis.

Low Expression of the bcl2 Gene in Gastric Adenocarcinomas in Mazandaran Province of Iran

BACKGROUND

Gastric cancer accounts for about 8% of the total cancer cases and 10% of total cancer deaths worldwide. It is the second lethal cancer after esophageal cancer and is considered the fourth most common cancer in north and northwest Iran. The bcl2 family has a key role in the regulation of apoptosis and change in its expression can contribute to cancer. This study initially scheduled to determine the expression of bcl2 gene in tissue samples of adenocarcinoma cancer patients.

MATERIALS AND METHODS

A total of 10 samples of gastric adenocarcinoma and 10 of normal tissues from Sari hospital were selected and after DNA extraction from tissues, bcl2 gene expression assayed by real-time PCR.

RESULTS

Our results demonstrated higher expression of the bcl2 gene in control compared with cancer and marginal cancer tissues.

CONCLUSIONS

On one hand BCL2 plays an important role as an oncogene to inhibit apoptosis; on the other hand, it can initiate cell cycle arrest at G0 stage. Our observed association between its expression and patient survival is quite conflicting and may be tissue-specific. The data suggest expression both tumoural and non-tumoral(marginal) groups have lowered expression than controls (P>0.05). Due to the low number of samples we could not examine the relationship with clinicopathological features. However, bcl-2 expression may be important for prognostic outcome or a useful target for therapeutic intervention.

Stabilization of G-quadruplex DNA and inhibition of Bcl-2 expression by a pyridostatin analog

The G-quadruplexes located in the P1 promoter of B-cell lymphoma-2 (Bcl-2) gene are implicated to regulate Bcl-2 expression. Here, we designed a new pyridostatin analog named PDF, which exhibited high specificity and stabilizing effect toward G-quadruplexes. The luciferase assay demonstrated that PDF could significantly suppress Bcl-2 transcriptional activation in human laryngeal squamous carcinoma cells (Hep-2) cells. Besides, PDF also induced cell apoptosis in vitro assays. These results provide an excellent G-quadruplex specific ligand as an efficient Bcl-2 inhibitor. These results also implicate that PDF may be a potential anticancer drug to head neck cancer.

A New G-Quadruplex with Hairpin Loop Immediately Upstream of the Human BCL2 P1 Promoter Modulates Transcription

The abnormal overexpression of the BCL2 gene is associated with many human tumors. We found a new 28-mer G-quadruplex-forming sequence, P1G4, immediately upstream of the human BCL2 gene P1 promoter. The P1G4 is shown to be a transcription repressor using a promoter-driven luciferase assay; its inhibitory effect can be markedly enhanced by the G-quadruplex-interactive compound TMPyP4. G-quadruplex can readily form in the P1G4 sequence under physiological salt condition as shown by DMS footprinting. P1G4 and previously identified Pu39 G-quadruplexes appear to form independently in adjacent regions in the BCL2 P1 promoter. In the extended BCL2 P1 promoter region containing both Pu39 and P1G4, P1G4 appears to play a more dominant role in repressing the transcriptional activity. Using NMR spectroscopy, the P1G4 G-quadruplex appears to be a novel dynamic equilibrium of two parallel structures, one regular with two 1-nt loops and a 12-nt middle loop and another broken-strand with three 1-nt loops and a 11-nt middle loop; both structures adopt a novel hairpin (stem-loop duplex) conformation in the long loop. The dynamic equilibrium of two closely related structures and the unique hairpin loop conformation are specific to the P1G4 sequence and distinguish the P1G4 quadruplex from other parallel structures. The presence of P1G4 and Pu39 in adjacent regions of the BCL2 P1 promoter suggests a mechanism for precise regulation of BCL2 gene transcription. The unique P1G4 G-quadruplex may provide a specific target for small molecules to modulate BCL2 gene transcription.

Study of regulatory promoter polymorphism (-248 G>A) of Bax gene in patients with gastric cancer in the northern provinces of Iran

AIM

The aim of this study is to evaluate the polymorphism in Bax gene and its association with some clinical pathology traits in gastric cancer.

BACKGROUND

Gastric cancer is considered as the fourth most common cancer in the north and northwest of Iran. Bcl2 family has a key role in regulation of apoptosis, and any changes in the expression of Bcl2 lead to cancer.

PATIENTS AND METHODS

Blood samples were collected from 100 cases and 89 controls in the northern provinces of Iran to evaluate promoter polymorphism (-248G<A) of Bax gene. Genotyping was carried out by PCR-RFLP method.

RESULTS

The result of this study demonstrated the existence of polymorphism in the above-mentioned region of Bax gene. Sixty-nine patients (%69) with genotype GG and 31 patients (%31) with genotype AG were observed in the case group. No mutant genotype was found among cases. Sixty-seven individuals (%75/28) with genotype GG, 21 individuals (%23/59) with genotype AG and only one mutant genotype (AA) were demonstrated in the control group. The bioinformatics analysis showed that this polymorphism removed the probable Sp1 motifs, which may affect its expression in the cells.

CONCLUSION

Allele G was the most frequent between both patient and control samples. Polymorphism may be effective on Bax expression, but it requires further investigation. Our results showed significant effects between genotypes and features of gender and age, whereas no significant relation were observed between the genotypes and grade, stage as well as smoking traits.

The acute lymphoblastic leukemia prognostic scoring whether it is possible by BCL-2, BAX gene promoter genotyping

BACKGROUND

BCL-2 is the most important anti-apoptotic regulator and Bax is a pro-apoptotic protein. The status of these parameters or the ration of BCL-2 to BAX is important in malignant cell fate as well as normal cells.

METHODS

Sixty-two ALL patients and 62 healthy sex-and age-matched controls were studied. After genotyping, the promoter region of the BAX and BCL-2 genes by RFLP-PCR method the patients were classified in nine prognostic groups, after that, the overall survival ratio of each score was compared with others pair-wise or between groups.

RESULTS

The frequencies of the AA, AC, CC alleles of the BCL-2 C-938A polymorphism in patient group were 33 (53.23%), 18 (29.03%), 11 (17.74%), and in the control group were 13 (21.0%), 27 (43.5%), 22 (35.5%), respectively (P=0.003). Also, the frequencies of AA, AG, GG alleles of the BAX G-248A SNP were 15 (24.2%), 24 (38.7%), 23 (37.1%) in ALL group and 13 (21.0%), 25 (40.3%), 24 (38.7%) (p>0.05) in the control group. The survival time estimation and ratio were significantly different between different SNPs in BCL-2 (P=0.002).

CONCLUSION

These findings showed that the BCL-2 promoter region polymorphism is more reliable than BAX gene promoter polymorphism in any ALL scoring system. But the establishment of complete scoring system requires further more clinical and laboratory findings along with genetic polymorphisms is necessary.

Influence of BCL2-938 C>A promoter polymorphism and BCL2 gene expression on the progression of breast cancer

BCL2 (B-cell leukemia/lymphoma 2) gene functions as antiapoptotic regulatory element and known to be associated with tumorigenesis. The SNP-938 (C>A) (rs2279115), located in the inhibitory P2 promoter of the BCL2 gene, influences differential binding affinities of transcriptional factors thereby affecting BCL2 expression. The present study is an attempt to evaluate the association between BCL2(-938C>A) polymorphism and clinical characteristics of breast cancer patients as well as to analyze BCL2 expression and Ki67 proliferation index with respect to the genotypes. One hundred ten primary breast cancer tumor tissues were genotyped for -938 C>A polymorphism through PCR-RFLP method as well as evaluated for BCL2 expression and ki67 proliferation index by immunohistochemistry. Evaluation of apoptosis level was performed by flowcytometry. The results revealed that AA genotype was associated with an increased risk (AA Vs AC + CC) by 2.86-fold (p = 0.07) for breast cancer development which reflected in elevated A allele frequency also. AA genotype was found to be predominant among BCL2 positive tumors as compared to BCL2 negative tumors. Further, AA genotype was found to be associated with advanced stage tumors, node positive status, and high Ki67 proliferation index compared to CA and CC genotypes indicating that elevated expression of BCL2 gene in the presence of A allele might be associated with decreased apoptosis and enhanced proliferation rate. AA genotype of BCL2-938C>A polymorphism might influence BCL2 gene expression there by associated with elevated risk for breast cancer progression. Probably, failure of apoptosis due to enhanced expression and antiapoptotic protein BCL2 might promote malignant growth.

Polymorphisms of BCL2 and BAX Genes Associate with Outcomes in Advanced Non-small cell lung cancer Patients treated with platinum-based Chemotherapy

Single-nucleotide polymorphisms (SNP) of the gene belonging to the BCL2 family are thought to play a role in chemotherapy resistance. This study investigated the association of BCL2-938C>A(rs2279115) and BAX-248G>A(rs4645878) promoter region SNPs and the clinical responses and outcomes of 235 non-small cell lung cancer (NSCLC) patients treated with platinum-based chemotherapy. The data suggested that BAX-248GA and GA+AA genotype was associated with poor response [odds ratio (OR) 1.943, p = 0.039; OR 1.867, p = 0.038, respectively] to chemotherapy, and BCL2-938CA, CA+AA and BAX-248GA, AA and GA+AA were associated with poor progression-free survival (PFS) [hazard ratio (HR) 1.514, p = 0.004; HR 1.456, p = 0.009; HR 1.449, p = 0.013; HR 2.006, p = 0.010; HR 1.506, p = 0.003, respectively] and BCL2-938CA, AA and CA+AA and BAX-248GA, AA and GA+AA were associated with poor overall survival (OS) (HR 2.006, p < 0.001; HR 2.322, p < 0.001; HR 2.096, p < 0.001; HR 1.632, p = 0.001; HR 2.014, p = 0.010; HR 1.506, p < 0.001, respectively). Furthermore, combination of these two polymorphisms showed patients with 2-4 variant alleles of these two genes associated with poor PFS and OS (HR 1.637, p = 0.001; HR 2.365, p < 0.001). The data from the current study provide evidence that BCL2-938C>A and BAX-248G>A polymorphisms may be useful in predicting clinical outcomes of patients with advanced inoperable NSCLC to platinum-based chemotherapy.

Alpha fetoprotein mediates HBx induced carcinogenesis in the hepatocyte cytoplasm

Although tumor-associated fetal protein AFP has demonstrated utility as a clinical tumor marker, the significance of intracellular AFP is still unclear. The aim of this study was to explore the role of cytoplasmic AFP during HBx induced carcinogenesis, which had not previously been recognized; 614 HCC patients were analyzed for correlation of HBV infection with AFP level, and much higher AFP levels were found in HBsAg positive patients. Tumor tissue specimens from 20 HCC patients were used for analysis of AFP and GADD45α. Analysis of HCC specimens showed that upregulation of cytoplasmic AFP is associated with down-regulation of GADD45α in neoplastic tissue. Transfected HBx promotes transcription of AFP by acting on the elements in the AFP gene regulatory region. HBx itself did not directly impact transcription of GADD45α. However, the obstruction of RAR signaling by HBx induced elevation of AFP, which led to down-regulation of GADD45α. Cytoplasmic AFP was able to interact with RAR, disrupting its entrance into the nucleus and binding to the elements in the regulatory region of the GADD45α gene. Knockdown of AFP in siRNA-transfected AFP positive cell lines was synchronously associated with an incremental increase of RAR binding to DNA, as well as upregulation of GADD45α and it was contrary in AFP gene-transfected AFP negative cell lines. These results indicate cytoplasmic AFP is not only a histochemical tumor biomarker for human hepatoma but is also an intracellular signal molecule and potential participant in HBx induced hepatocarcinogenesis.

Association of the functional BCL-2 rs2279115 genetic variant and small cell lung cancer

As a well-known oncogene, B cell lymphoma-2 (BCL-2) can promote cancer cell survival through preventing their apoptosis. Several functional BCL-2 single nucleotide polymorphisms (SNPs), such as rs2279115, rs1801018, and rs1564483, have been identified and might contribute to cancer susceptibility. However, the involvement of these SNPs in small cell lung cancer (SCLC) was still unclear. As a result, we investigated associations between these three genetic variants and SCLC risk in a case-control design. Genotypes were determined in two independent case-control sets consisted of 520 SCLC patients and 1040 controls from two medical centers. Odds ratios (ORs) and 95 % confidence intervals (CIs) were calculated utilizing unconditional logistic regression. We found that only BCL-2 rs2279115 genetic variant significantly contributed to decreased SCLC risk in Chinese Han populations, with the rs2279115 A allele as the protective allele. Stratified analyses of association between BCL2 rs2279115 SNP and SCLC risk indicated that the functional polymorphism was only significantly associated with decreased risk of the limited stage SCLC but not the extensive stage disease. Our results indicate that the BCL-2 rs2279115 genetic variant was associated with SCLC risk in Chinese populations and support the hypothesis that SNPs in regulatory regions of oncogenes might contribute to cancer susceptibility.

Functional BCL-2 regulatory genetic variants contribute to susceptibility of esophageal squamous cell carcinoma

B-cell lymphoma-2 (BCL-2) prevents apoptosis and its overexpression could promote cancer cell survival. Multiple functional BCL-2 genetic polymorphisms, such as rs2279115, rs1801018 and rs1564483, have been identified previously and might be involved in cancer development through deregulating BCL-2 expression. Therefore, we examined associations between these three polymorphisms and esophageal squamous cell carcinoma (ESCC) susceptibility as well as its biological function in vivo. Genotypes were determined in two independent case-control sets consisted of 1588 ESCC patients and 1600 controls from two regions of China. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by logistic regression. The impact of the rs2279115 polymorphism on BCL-2 expression was detected using esophagus tissues. Our results demonstrated that the BCL-2 rs2279115 AA genotype was significantly associated with decreased ESCC risk compared with the CC genotype (OR = 0.72, 95% CI = 0.57–0.90, P = 0.005), especially in nonsmokers (OR = 0.42, 95% CI = 0.29–0.59, P = 0.001) or nondrinkers (OR = 0.44, 95% CI = 0.32–0.62, P = 0.002). Genotype-phenotype correlation studies demonstrated that subjects with the rs2279115 CA and AA genotypes had a statistically significant decrease of BCL-2 mRNA expression compared to the CC genotype in both normal and cancerous esophagus tissues. Our results indicate that the BCL-2 rs2279115 polymorphism contributes to ESCC susceptibility in Chinese populations.

Influence of BCL2-938C>A and BAX-248G>A promoter polymorphisms in the development of AML: case-control study from South India

B-cell lymphoma 2 (BCL2) and BCL2-associated X protein (BAX) proteins are anti-apoptotic and pro-apoptotic determinants of mitochondrial-mediated apoptosis, and their relative expression determines the cell fate. The promoter polymorphisms in these genes were shown to alter the protein function or expression and exert an impact on apoptosis regulation. Deregulation in the expression of any of these genes leads to disruption of cellular homeostasis and malignant transformation. The present study was aimed to determine the association of BCL2-938C>A and BAX-248G>A promoter polymorphisms with origin and progression of acute myeloid leukemia (AML). We also have performed combined genotype analysis to evaluate the cumulative effect of risk genotypes in the AML development. These polymorphisms were genotyped by polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) in 221 AML patients and 305 age- and sex-matched healthy controls. Our study revealed that BCL2-938CA (p = 0.018) and BAX-248GG (0.043) genotypes were significantly associated with increased risk for AML occurrence. BAX-248A allele had shown decreased risk for AML. The combined analysis had shown that BCL2-938CA+AA-BAX-248GG group had a 1.63-fold (95 % CI: 1.08-2.45, p = 0.02) increased risk for AML. None of the clinical variables had shown any significant association with both polymorphisms. With respect to complete remission (CR) rate, BAX-248GG genotype (p = 0.002) and G allele (p = 0.009) had conferred significant risk for complete remission failure. Although the log rank test was not significant, survival analysis had shown a trend where BCL2-938CA genotype, and BAX-248GG had reduced median disease-free survival (DFS) of 9 and 10 months, respectively. In conclusion, BCL2-938C>A and BAX-248G>A gene polymorphisms might contribute to the origin of AML. Moreover, influence of BAX-248GG genotype on CR and DFS rate suggests that the BAX-248G>A polymorphism can serve as marker for poor prognosis in AML.

A genetic variant of p53 restricts the mucous secretory phenotype by regulating SPDEF and Bcl-2 expression

Despite implications for carcinogenesis and other chronic diseases, basic mechanisms of p53 and its variants in suppressing Bcl-2 levels are poorly understood. Bcl-2 sustains mucous cell metaplasia, whereas p53(-/-) mice display chronically increased mucous cells. Here we show that p53 decreases bcl-2 mRNA half-life by interacting with the 5' untranslated region (UTR). The p53-bcl-2 mRNA interaction is modified by the substitution of proline by arginine within the p53 proline-rich domain (PRD). Accordingly, more mucous cells are present in primary human airway cultures with p53(Arg) compared with p53(Pro). Also, the p53(Arg) compared with p53(Pro) displays higher affinity to and activates the promoter region of SAM-pointed domain-containing Ets-like factor (SPDEF), a driver of mucous differentiation. On two genetic backgrounds, mice with targeted replacement of prolines in p53 PRD show enhanced expression of SPDEF and Bcl-2 and mucous cell metaplasia. Together, these studies define the PRD of p53 as a determinant for chronic mucous hypersecretion.

A newly identified G-quadruplex as a potential target regulating Bcl-2 expression

BACKGROUND

A new G-quadruplex structure located in the B-cell CLL/lymphoma 2 (Bcl-2) P1 promoter and its physiological function related to Bcl-2 transcription have been studied to find a potential anticancer therapeutic target.

METHODS

Absorption, polyacrylamide gel electrophoresis, fluorescence, circular dichroism, and nuclear magnetic resonance spectra have been employed to determine G-quadruplex structure and the interaction between G-quadruplex and phenanthrolin-dicarboxylate. Real time polymerase chain reaction and luciferase assay were done to assess the physiological function of the G-quadruplex structure.

RESULTS

The UV-melting and polyacrylamide gel electrophoresis studies show that the p32 DNA sequence forms an intramolecular G-quadruplex structure. Circular dichroism and nuclear magnetic resonance spectra indicate that the G-quadruplex is a hybrid-type structure with four G-tetrads. Fluorescence spectra show that a phenanthroline derivative has a higher binding affinity for p32 G-quadruplex than duplex. Further circular dichroism and nuclear magnetic resonance studies indicate that the phenanthroline derivative can regulate p32 G-quadruplex conformation. Real time polymerase chain reaction and luciferase assays show that the phenanthroline derivative has down-modulated Bcl-2 transcription activity in a concentration-dependent manner. However, no such effect was observed when p32 G-quadruplex was denatured through base mutation.

CONCLUSION

The newly identified G-quadruplex located in the P1 promoter of Bcl-2 oncogene is intimately related with Bcl-2 transcription activity, which may be a promising anticancer therapeutic target.

GENERAL SIGNIFICANCE

The newly identified G-quadruplex in the Bcl-2 P1 promoter may be a novel anticancer therapeutic target.

General peroxidase activity of a parallel G-quadruplex-hemin DNAzyme formed by Pu39WT - a mixed G-quadruplex forming sequence in the Bcl-2 P1 promoter

Background

A 39-base-pair sequence (Pu39WT) located 58 to 19 base pairs upstream of the Bcl-2 P1 promoter has been implicated in the formation of an intramolecular mixed G-quadruplex structure and is believed to play a major role in the regulation of bcl-2 transcription. However, an extensive functional exploration requires further investigation. To further exploit the structure–function relationship of the Pu39WT-hemin DNAzyme, the secondary structure and peroxidase activity of the Pu39WT-hemin complex were investigated.

Results

Experimental results showed that when Pu39WT was incubated with hemin, it formed a uniparallel G-quadruplex-hemin complex in K⁺ or Na⁺ solution, rather than a mixed hybrid without bound hemin. Also, Pu39WT-hemin showed peroxidase activity (ABTS²⁻) in the presence of H₂O₂ to produce the colored radical anion (ABTS^•-), which could then be used to determine the parameters governing the catalytic efficiency and reveal the peroxidase activity of the Pu39WT-hemin DNAzyme.

Conclusions

These results demonstrate the general peroxidase activity of Pu39WT-hemin DNAzyme, which is an intramolecular parallel G-quadruplex structure. This peroxidase activity of hemin complexed with the G-quadruplex-forming sequence in the Bcl-2 gene promoter may imply a potential mechanism of hemin-mediated cellular injury.

Development and antitumor activity of a BCL-2 targeted single-stranded DNA oligonucleotide

PNT100 is a 24-base, chemically unmodified DNA oligonucleotide sequence that is complementary to a region upstream of the BCL-2 gene. Exposure of tumor cells to PNT100 results in suppression of proliferation and cell death by a process called DNA interference. PNT2258 is PNT100 that is encapsulated in protective amphoteric liposomes developed to efficiently encapsulate the PNT100 oligonucleotide, provide enhanced serum stability, optimized pharmacokinetic properties and antitumor activity of the nanoparticle both in vivo and in vitro. PNT2258 demonstrates broad antitumor activity against BCL-2-driven WSU-DLCL2 lymphoma, highly resistant A375 melanoma, PC-3 prostate, and Daudi-Burkitt’s lymphoma xenografts. The sequence specificity of PNT100 was demonstrated against three control sequences (scrambled, mismatched, and reverse complement) all encapsulated in a lipid formulation with identical particle characteristics, and control sequences did not demonstrate antiproliferative activity in vivo or in vitro. PNT2258 is currently undergoing clinical testing to evaluate safety and antitumor activity in patients with recurrent or refractory non-Hodgkin’s lymphoma and additional studies are planned.

Role of polymorphisms in BCL-2 and BAX genes in modulating the risk of developing non-Hodgkin lymphoma

The aim of this study was to investigate whether polymorphisms of - 938C/A and Thr43Ala in the BCL-2 gene and G - 248A in the BAX gene are associated with the risk of developing non-Hodgkin lymphoma (NHL). We genotyped polymorphisms of - 938C/A and Thr43Ala in the BCL-2 gene and G-248A in the BAX gene among 424 patients with NHL and 446 controls. We found that the - 938AA genotype of the BCL2 gene was significantly associated with the risk of developing NHL (p < 0.001) and this genotype was associated with advanced stage (p = 0.01). Meanwhile, individuals having - 248AG + AA genotypes were significantly associated with an increased risk of NHL (p = 0.01), and these genotypes were associated with larger tumor size (p = 0.02). The present study demonstrated that the - 938AA genotype of the BCL-2 gene and - 248AG + AA genotype of the BAX gene may be susceptible genotypes for NHL. There appeared to be an impact of the BCL2 - 938AA genotype on advanced stage and - 248AG + AA genotypes on tumor size in NHL.

The BCL2-938 C > A promoter polymorphism is associated with risk group classification in children with acute lymphoblastic leukemia

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer. While current treatment regimens achieve almost 80% overall survival, long-term side effects of chemotherapeutic agents can be severe. The functional BCL2-938C > A promoter polymorphism is known to influence the balance between survival and apoptosis of malignant hematolymphoid cells. We investigated its usefulness as a marker for treatment stratification for children with ALL.

METHODS

We analyzed DNA from 182 children suffering from ALL in this study to determine genotypes of the -938 C > A polymorphism by "slow-down" PCR.

RESULTS

ALL patients with the BCL2-938CC genotype had an approximately 3-fold higher risk of belonging to a high-risk group. Within the high-risk group, 50% of BCL2-938CC patients were classified as high-risk due to poor prednisone response whereas only 33% of patients with AC and AA genotypes were classified as high-risk for the same reason.

CONCLUSIONS

Our results suggest that BCL2-938C > A genotyping may be beneficial for therapy response prediction in ALL patients, and warrant examination in a larger cohort to validate its usefulness for treatment stratification of pediatric ALL patients.

A novel SATB1 binding site in the BCL2 promoter region possesses transcriptional regulatory function

BCL2 is a key regulator of apoptosis. Our previous work has demonstrated that special AT-rich sequence-binding protein 1 (SATB1) is positively correlated with BCL2 expression. In the present study, we report a new SATB1 binding site located between P1 and P2 promoters of the BCL2 gene. The candidate SATB1 binding sequence predicted by bioinformatic analysis was investigated in vitro and in vivo by electrophoretic gel mobility shift assays (EMSA) and chromatin immunoprecipitation (ChIP). One 25-bp sequence, named SB1, was confirmed to be SATB1 binding site. The regulatory function of SB1 and its relevance to SATB1 were further examed with dual-luciferase reporter assay system in Jurkat cells. We found that SB1 could negatively regulate reporter gene activity. Mutation of SATB1 binding site further repressed the activity. Knockdown of SATB1 also enhanced this negative effect of SB1. Our data indicate that the SB1 sequence possesses negative transcriptional regulatory function and this function can be antagonized by SATB1.

Genetic determinants of neuronal vulnerability to apoptosis

Apoptosis is a common mode of cell death that contributes to neuronal loss associated with neurodegeneration. Single-nucleotide polymorphisms (SNPs) in chromosomal DNA are contributing factors dictating natural susceptibility of humans to disease. Here, the most common SNPs affecting neuronal vulnerability to apoptosis are reviewed in the context of neurological disorders. Polymorphic variants in genes encoding apoptotic proteins, either from the extrinsic (FAS, TNF-α, CASP8) or the intrinsic (BAX, BCL2, CASP3, CASP9) pathways could be highly valuable in the diagnosis of neurodegenerative diseases and stroke. Interestingly, the Arg72Pro SNP in TP53, the gene encoding tumor suppressor p53, was recently revealed a biomarker of poor prognosis in stroke due to its ability to modulate neuronal apoptotic death. Search for new SNPs responsible for genetic variability to apoptosis will ensure the implementation of novel diagnostic and prognostic tools, as well as therapeutic strategies against neurological diseases.

Impact of single-nucleotide polymorphisms at the TP53-binding and responsive promoter region of BCL2 gene in modulating the phenotypic variability of LGMD2C patients

Apoptosis of skeletal muscle fibers is a well-known event occurring in patients suffering from muscular dystrophies. In this study, we hypothesized that functional polymorphisms in genes involved in the mitochondrial apoptotic pathway might modulate the apoptotic capacity underlying the muscle loss and contributing to intrafamilial and interfamilial variable phenotypes in LGMD2C (Limb Girdle Muscular Dystrophy type 2C) patients sharing the same c.521delT mutation in SGCG gene. Detection of apoptosis was confirmed on muscle biopsies taken from LGMD2C patients using the TUNEL method. We genotyped then ten potentially functional SNPs in TP53, BCL-2 and BAX genes involved in the mitochondrial apoptotic pathway. Potential genotype-dependent Bcl-2 and p53 protein expressed in skeletal muscle was investigated using western blot and ELISA assays. The result showed that muscle cells carrying the TP53-R72R and TP53-16 bp del/del genotypes displayed an increased p53 level which could be more effective in inducing apoptosis by activation of the pro-apoptotic gene expression. In addition, the BCL2-938 AA genotype was associated with increased Bcl-2 protein expression in muscle from LGMD2C patients compared to -938CC genotype, while there was no evidence of significant difference in the BAX haplotype. Our findings suggest that increased Bcl-2 protein expression may counteract pro-apoptotic pathways and thus reduce the muscle loss. To the best of our knowledge, this is a pioneer study evaluating the role of apoptotic BCL-2 and TP53 genes in contributing to the phenotypic manifestation of c.521delT mutation in LGMD2C patients. Larger studies are needed to validate these findings.

The -938A/A genotype of BCL2 gene is associated with esophageal cancer

Perturbations in the apoptotic genes have been implicated in human malignancies. The purpose of the present study was to investigate the polymorphisms of -938C/A, Thr43Ala in anti-apoptotic B-cell lymphoma 2 gene (BCL2) and -248G/A in pro-apoptotic B-cell lymphoma 2-associated X protein gene (BAX) and to explore their role in influencing the susceptibility for development of esophageal cancer. A total of 205 esophageal cancer patients and 224 controls were enrolled in the present study. The genotype and allele distributions of -938C/A, ala43thr in BCL2 and -248G/A in BAX were analyzed in patients and controls, as well as the association of -938C/A genotype with clinical characteristics in patients. We found that homozygous -938A/A genotype of BCL2 gene was significantly associated with risk of developing esophageal cancer (χ2=9.269, P=0.002, OR=2.585, 95%CI = 1.380-4.842). Association with clinical characteristics showed that the patients with BCL2 -938A/A genotype were more likely to develop into poor differentiation compared with the AC and CC carriers (χ2=5.796, P=0.016, OR=4.039, 95%CI=1.200-13.596), and we found smokers were more present in the -938A/A genotype subgroup (χ2=5.095, P=0.024, OR=2.679, 95%CI=0.893-8.025). The present study revealed that the -938A/A genotype of BCL2 gene is associated with susceptibility of esophageal cancer. There appeared to be an impact of BCL2 -938A/A genotype on tumor differentiation and smoking. Further studies are needed in a larger population.

Role of Caspase 8, Caspase 9 and Bcl-2 polymorphisms in papillary thyroid carcinoma risk in Han Chinese population

Dysregulation of apoptosis plays a key role in carcinogenesis. This study was designed to investigate the association of apoptosis-related gene Caspase 8, Caspase 9 and Bcl-2 polymorphisms with papillary thyroid carcinoma (PTC) susceptibility. We undertook a case-control study of 118 patients and 213 controls to investigate the association between Caspase 8 (-652 6 N ins/del), Caspase 9 (-1263 A>G) and Bcl-2 (-938 C>A) polymorphisms and PTC susceptibility by polymerase chain reaction restriction-fragment length polymorphism and DNA sequencing methods. We further analyzed the distribution of genotype frequency, as well as the association of genotype with clinicopathological characteristics. Overall, no statistically significant association was observed in Caspase 8 (-652 6 N ins/del). Nevertheless, Caspase 9 -1263 GG genotype was at increased risk of PTC (P=0.045; odds ratio (OR)=1.12). Furthermore, GG genotype thyroid cancers were significantly more common in older patients than AA or AG genotypes PTC and in cases of advanced pathological stages. However, Bcl-2 -938 AA genotype demonstrated a protective effect in PTCs (P=0.004; OR=0.35). Polymorphism in Caspase 9 (-1263 A>G) was observed to be associated with susceptibility of PTC. However, Bcl-2 (-938 C>A) polymorphism indicated to play a protective role in susceptibility to PTC. Nevertheless, further investigation with a larger sample size is needed to support our results.

Upregulation of cellular Bcl-2 by the KSHV encoded RTA promotes virion production

Apoptosis of virus infected cells can restrict or dampen full blown virus propagation and this can serve as a protective mechanism against virus infection. Consequently, viruses can also delay programmed cell death by enhancing the expression of anti-apoptotic proteins. Human Bcl-2 is expressed on the surface of the mitochondrial membrane and functions as the regulator of the delicate balance between cell survival and apoptosis. In this report, we showed that the replication and transcription activator (RTA) encoded by KSHV ORF 50, a key regulator for KSHV reactivation from latent to lytic infection, upregulates the mRNA and protein levels of Bcl-2 in 293 cells, and TPA-induced KSHV-infected cells. Further analysis revealed that upregulation of the cellular Bcl-2 promoter by RTA is dose-dependent and acts through targeting of the CCN₉GG motifs within the Bcl-2 promoter. The Bcl-2 P2 but not the P1 promoter is primarily responsive to RTA. The results of ChIP confirmed the direct interaction of RTA protein with the CCN₉GG motifs. Knockdown of cellular Bcl-2 by lentivirus-delivered small hairpin RNA (shRNA) resulted in increased cell apoptosis and decreased virion production in KSHV-infected cells. These findings provide an insight into another mechanism by which KSHV utilizes the intrinsic apoptosis signaling pathways for prolonging the survival of lytically infected host cells to allow for maximum production of virus progeny.

Structural insights into G-quadruplexes: towards new anticancer drugs

DNA G-quadruplexes are DNA secondary structures formed in specific G-rich sequences. DNA sequences that can form G-quadruplexes have been found in regions with biological significance, such as human telomeres and oncogene-promoter regions. DNA G-quadruplexes have recently emerged as a new class of novel molecular targets for anticancer drugs. Recent progress on structural studies of the biologically relevant G-quadruplexes formed in human telomeres and in the promoter regions of human oncogenes will be discussed, as well as recent advances in the design and development of G-quadruplex-interactive drugs. DNA G-quadruplexes can readily form in solution under physiological conditions and are globularly folded nucleic acid structures. The molecular structures of intramolecular G-quadruplexes appear to differ from one another and, therefore, in principle may be differentially regulated and targeted by different proteins and drugs.

Quadruplex formation is necessary for stable PNA invasion into duplex DNA of BCL2 promoter region

Guanine-rich sequences are highly abundant in the human genome, especially in regulatory regions. Because guanine-rich sequences have the unique ability to form G-quadruplexes, these structures may play a role in the regulation of gene transcription. In previous studies, we demonstrated that formation of G-quadruplexes could be induced with peptide nucleic acids (PNAs). PNAs designed to bind the C-rich strand upstream of the human BCL2 gene promoted quadruplex formation in the complementary G-rich strand. However, the question whether G-quadruplex formation was essential for PNA invasion remained unanswered. In this study, we compared PNA invasion in the native and mutant, i.e. not forming G-quadruplex, BCL2 sequences and showed that G-quadruplex is required for effective PNA invasion into duplex DNA. This finding provides strong evidence for not only sequence-specific, but also quadruplex specific, gene targeting with PNA probes. In addition, we examined DNA-duplex invasion potential of PNAs of various charges. Using the gel shift assay, chemical probing and dimethyl sulfate (DMS) protection studies, we determined that uncharged zwitterionic PNA has the highest binding specificity while preserving efficient duplex invasion.

BCL-2 (-938C > A) polymorphism is associated with breast cancer susceptibility

Background

BCL-2 (B-cell leukemia/lymphoma 2) gene has been demonstrated to be associated with breast cancer development and a single nucleotide polymorphism (SNP; -938C > A) has been identified recently. To investigate whether this polymorphism functions as a modifier of breast cancer development, we analyzed the distribution of genotype frequency, as well as the association of genotype with clinicopathological characteristics. Furthermore, we also studied the effects of this SNP on Bcl-2 expression in vitro.

Methods

We genotyped the BCL-2 (-938C > A) in 114 patients and 107 controls, and analyzed the estrogen receptor (ER), progestogen receptor (PR), C-erbB2 and Ki67 status with immunohistochemistry (IHC). Different Bcl-2 protein levels in breast cancer cell lines were determined using western blot. Logistic regression model was applied in statistical analysis.

Results

We found that homozygous AA genotype was associated with an increased risk (AA vs AC+CC) by 2.37-fold for breast cancer development and significant association was observed between nodal status and different genotypes of BCL-2 (-938C > A) (p = 0.014). AA genotype was more likely to develop into lobular breast cancer (p = 0.036). The result of western blot analysis indicated that allele A was associated with the lower level of Bcl-2 expression in breast cancer cell lines.

Conclusions

AA genotype of BCL-2 (-938C > A) is associated with susceptibility of breast cancer, and this genotype is only associated with the nodal status and pathological diagnosis of breast cancer. The polymorphism has an effect on Bcl-2 expression but needs further investigation.