Single nucleotide polymorphism in prohibitin 3' untranslated region and breast-cancer susceptibility

Causal effects and metabolites mediators between immune cell and risk of breast cancer: a Mendelian randomization study

Introduction: The incidence and mortality of female breast cancer remain high, and the immune microenvironment of breast cancer has undergone significant alterations. However, the impact of blood immune cell levels on the risk of breast cancer is not fully understood. Therefor this study aims to investigate the causal relationship between blood immune cell levels and the risk of breast cancer. Methods: A Mendelian randomization (MR) analysis was employed to assess the causal relationship between immune cells and the risk of breast cancer, as along with their potential mediating factors. Genetic statistics of metabolites breast cancer and immune cells were obtained from the GWAS Catalog, while the genome-wide association study (GWAS) statistics of breast cancer were extracted from the UK biobank. Two-sample MR analysis were performed using inverse-variance weighted (IVW) to ascertain the causal association between immune cells and the risk of breast cancer. Furthermore, 1,400 metabolites were analyzed for their mediating role between immune cells and the risk of breast cancer. Results: MR analysis through IVW method revealed that genetically predicted CD24+ CD27+ B cells were associated with a decreased risk of breast cancer (OR = 0.9978, 95% CI: 0.996-0.999, p = 0.001), while IgD- CD38+ B cells were linked to an increased risk of breast cancer (OR = 1.002, 95% CI: 1.001-1.004, p = 0.005). Additional CD14+ CD16+ monocytes were associated with an increased risk of breast cancer (OR = 1.000, 95% CI: 1.000-1.001, p = 0.005). Mediation analysis revealed a positive causal relationship between IgD- CD38+ B cells and Glycerate levels, with the latter also exhibiting a positive causal relationship with the risk of breast cancer (p < 0.05). Conversely, IgD- CD38+ B cells displayed a negative causal relationship with Succinoyltaurine levels, and the latter also demonstrated a negative causal relationship with the risk of breast cancer (p < 0.05). Conclusion: This MR study provides novel genetic evidence supporting a causal relationship between IgD- CD38+ B cells and the risk of BC. Moreover, it is identified that IgD- CD38+ B cells contribute to an increased risk of BC through both positive and negative mediation effects involving Glycerate and Succinoyltaurine.

MDM4 polymorphisms associated with the risk but not the prognosis of esophageal cancer in Cixian high-incidence region from northern China

AIM

The mouse double minute 4 (MDM4) may contribute to tumorgenesis by inhibiting p53 tumor suppressor activity. This study was designed to investigate whether MDM4 polymorphisms could affect susceptibility to esophageal squamous cell carcinoma (ESCC) and the survival of ESCC patients in a population from Cixian high-incidence region of northern China, which has not been explored.

METHODS

MDM4 rs1380576 and rs4245739 were genotyped by polymerase chain reaction-ligase detection reaction (PCR-LDR) in 568 ESCC patients and 578 controls.

RESULTS

Compared to rs1380576 C/C genotype, C/G genotype was associated with decreased risk of ESCC (odds ratio [OR] = 0.761, 95% confidence interval [CI] = 0.595-0.973). Compared to rs4245739 A/A genotype, A/C or C/C genotype was related to increased susceptibility to ESCC (OR = 1.551, 95% CI = 1.001-2.402). Individuals with GC haplotype had significantly higher risk of ESCC than those with CA or GA haplotype (OR = 1.598, 95% CI = 1.048-2.438). Neither rs1380576 nor rs4245739 influenced the survival of ESCC patients.

CONCLUSION

rs1380576 and rs4245739 may be used to predict susceptibility to ESCC for population in Cixian high-incidence region.

Role of Prohibitins in Aging and Therapeutic Potential Against Age-Related Diseases

A decline in mitochondrial function has long been associated with age-related health decline. Several lines of evidence suggest that interventions that stimulate mitochondrial autophagy (mitophagy) can slow aging and prolong healthy lifespan. Prohibitins (PHB1 and PHB2) assemble at the mitochondrial inner membrane and are critical for mitochondrial homeostasis. In addition, prohibitins (PHBs) have diverse roles in cell and organismal biology. Here, we will discuss the role of PHBs in mitophagy, oxidative phosphorylation, cellular senescence, and apoptosis. We will also discuss the role of PHBs in modulating lifespan. In addition, we will review the links between PHBs and diseases of aging. Finally, we will discuss the emerging concept that PHBs may represent an attractive therapeutic target to counteract aging and age-onset disease.

Detecting DNA and RNA and Differentiating Single-Nucleotide Variations via Field-Effect Transistors

We detect short oligonucleotides and distinguish between sequences that differ by a single base, using label-free, electronic field-effect transistors (FETs). Our sensing platform utilizes ultrathin-film indium oxide FETs chemically functionalized with single-stranded DNA (ssDNA). The ssDNA-functionalized semiconducting channels in FETs detect fully complementary DNA sequences and differentiate these sequences from those having different types and locations of single base-pair mismatches. Changes in charge associated with surface-bound ssDNA vs double-stranded DNA (dsDNA) alter FET channel conductance to enable detection due to differences in DNA duplex stability. We illustrate the capability of ssDNA-FETs to detect complementary RNA sequences and to distinguish from RNA sequences with single nucleotide variations. The development and implementation of electronic biosensors that rapidly and sensitively detect and differentiate oligonucleotides present new opportunities in the fields of disease diagnostics and precision medicine.

A Putative Prohibitin-Calcium Nexus in β-Cell Mitochondria and Diabetes

The role of mitochondria in apoptosis is well known; however, the mechanisms linking mitochondria to the proapoptotic effects of proinflammatory cytokines, hyperglycemia, and glucolipotoxicity are not completely understood. Complex Ca²⁺ signaling has emerged as a critical contributor to these proapoptotic effects and has gained significant attention in regulating the signaling processes of mitochondria. In pancreatic β-cells, Ca²⁺ plays an active role in β-cell function and survival. Prohibitin (PHB), a mitochondrial chaperone, is actively involved in maintaining the architecture of mitochondria. However, its possible interaction with Ca²⁺-activated signaling pathways has not been explored. The present review aims to examine potential crosstalk between Ca²⁺ signaling and PHB function in pancreatic β-cells. Moreover, this review will focus on the effects of cytokines and glucolipotoxicity on Ca²⁺ signaling and its possible interaction with PHB. Improved understanding of this important mitochondrial protein may aid in the design of more targeted drugs to identify specific pathways involved with stress-induced dysfunction in the β-cell.

Association of rs11801299 and rs1380576 polymorphisms at MDM4 with risk, clinicopathological features and prognosis in patients with retinoblastoma

BACKGROUND

rs11801299 and rs1380576, two novel polymorphisms in MDM4 gene, have been investigated in several different cancer types. However, the role of these two polymorphisms in retinoblastoma (RB) remains unclear.

METHODS

A total of 126 patients with primary RB and 148 age-/gender-matched controls were included in this retrospective study. The frequency of rs11801299 and rs1380576 were determined between RB patients and controls. The association of these two polymorphisms with clinicopathological characteristics, prognosis were further evaluated.

RESULTS

AA genotype at rs11801299 was significantly associated with an increased risk of developing RB (OR = 2.06, 95%CI 1.09-3.90). The possibility of developing RB was also significantly increased in individuals with A allele at rs11801299 (OR = 1.49, 95%CI 1.06-2.08). RB patients carrying AA genotype and A allele at rs11801299 were more likely to have tumor invasion and poor differentiation. As for rs1380576, a significantly lower risk of developing RB was observed in patients with G allele (CG + GG) compared with wild-type CC genotype (OR = 0.59, 95%CI 0.36-3.95). RB patients with GG genotype or G allele had a lower risk of developing highly aggressive cancer. Kaplan-Meier curves and log-rank results revealed that RB patients carrying AA genotype or A allele (AA + GA) at rs11801299 had significantly poorer prognosis. Multivariate COX analysis showed that the rs11801299 G allele was associated with decreased survival but was not an independent prognostic factor.

CONCLUSION

rs11801299 was significantly associated with RB risk, pathological differentiation, tumor aggressiveness and poor prognosis.

Genetic determinants of sporadic breast cancer in Sri Lankan women

Background

While a range of common genetic variants have been identified to be associated with risk of sporadic breast cancer in several Western studies, little is known about their role in South Asian populations. Our objective was to examine the association between common genetic variants in breast cancer related genes and risk of breast cancer in a cohort of Sri Lankan women.

Methods

A case-control study of 350 postmenopausal women with breast cancer and 350 healthy postmenopausal women was conducted. Genotyping using the iPLEX GOLD assay was done for 56 haplotype-tagging single nucleotide polymorphisms (SNPs) in 36 breast cancer related genes. Testing for association was done using an additive genetic model. Odds ratios and 95% confidence intervals were calculated using adjusted logistic regression models.

Results

Four SNPs [rs3218550 (XRCC2), rs6917 (PHB), rs1801516 (ATM), and rs13689 (CDH1)] were significantly associated with risk of breast cancer. The rs3218550 T allele and rs6917 A allele increased breast cancer risk by 1.5-fold and 1.4-fold, respectively. The CTC haplotype defined by the SNPs rs3218552|rs3218550|rs3218536 on chromosome 7 (P = 0.0088) and the CA haplotype defined by the SNPs rs1049620|rs6917 on chromosome 17 (P = 0.0067) were significantly associated with increased risk of breast cancer. The rs1801516 A allele and the rs13689 C allele decreased breast cancer risk by 0.6-fold and 0.7-fold, respectively.

Conclusions

These findings suggest that common genetic polymorphisms in the XRCC2, PHB, CDH1 and ATM genes are associated with risk of breast cancer among Sri Lankan postmenopausal women. The exact biological mechanisms of how these variants regulate overall breast cancer risk need further evaluation using functional studies.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4112-4) contains supplementary material, which is available to authorized users.

The association between differentially expressed micro RNAs in breast cancer cell lines and the micro RNA-205 gene polymorphism in breast cancer tissue

Micro (mi)RNAs are an endogenous non-coding small RNA comprised of 19–26 nucleotides. miRNAs regulate gene expression through the recognition of its ‘seed sequence’ and interactions with 3′-untranslated region of target miRNAs. Previous studies identified that miRNAs are associated with the onset and development of breast cancer and that a number of mutations in the coding DNA sequence of miRNAs affect its expression. Therefore, the present study aimed to screen differentially expressed miRNAs using miRNA expression profile chips to analyze the expression of miRNA (miR)-205 in 12 breast cell lines of different metastatic performance and benign proliferative variation as well as breast cancer via in-situ hybridization, and screen out single-nucleotide polymorphisms (SNPs) in the miR-205 coding gene region. In addition, the association between SNP and the clinicopathological features of breast lesions was investigated. The results of the present study demonstrated that the expression of miR-205 was decreased in breast cancer cells and tissues compared with benign lesions. SNPs in the miR-205 coding gene region were identified in tumor cell lines and as increasing lengths of the AGC repetitive sequence were lost, miR-205 expression increased. An association was identified between a number of SNPs in the miR-205 coding gene region and breast cancer, as well as between SNPs in miR-205 coding gene region and the clinicopathological features of breast cancer.

Cancer risk susceptibility loci in a Swedish population

A germline mutation in cancer predisposing genes is known to increase the risk of more than one tumor type. In order to find loci associated with many types of cancer, a genome-wide association study (GWAS) was conducted, and 3,555 Swedish cancer cases and 15,581 controls were analyzed for 226,883 SNPs. The study used haplotype analysis instead of single SNP analysis in order to find putative founder effects. Haplotype association studies identified seven risk loci associated with cancer risk, on chromosomes 1, 7, 11, 14, 16, 17 and 21. Four of the haplotypes, on chromosomes 7, 14, 16 and 17, were confirmed in Swedish familial cancer cases. It was possible to perform exome sequencing in one patient for each of those four loci. No clear disease-causing exonic mutation was found in any of the four loci. Some of the candidate loci hold several cancer genes, suggesting that the risk associated with one locus could involve more than one gene associated with cancer risk. In summary, this study identified seven novel candidate loci associated with cancer risk. It was also suggested that cancer risk at one locus could depend on multiple contributing risk mutations/genes.

Mouse double minute 4 variants modify susceptibility to risk of recurrence in patients with squamous cell carcinoma of the oropharynx

Given the crucial role of Mouse double minute 4 (MDM4) oncoprotein in p53 pathway, single nucleotide polymorphisms (SNPs) could serve as such biomarkers for prediction of SCCOP recurrence. Thus, we investigated associations between three tagging putatively functional variants of MDM4, two in the 3' untranslated region of 3' UTR [rs11801299 (NC_000001.10:g.204529084G>A) and rs10900598(NC_000001.10:g.204525568G>T)] and one in intron 1 [rs1380576(NC_000001.10:g.204488278G>C)], and recurrence risk of SCCOP in 1,008 incident patients. A log-rank test and multivariable Cox models were used to assess associations. Patients with MDM4-rs10900598 GT/TT had a worse disease-free survival (DFS) compared with corresponding GG genotype, while those with rs11801299 AG/AA genotypes had a lower recurrence risk than the cases with rs11801299 GG genotype (both log-rank, P < 0.001). Multivariable analysis showed that significantly different recurrence risk were found among patients with MDM4-rs10900598 GT/TT and rs11801299 AG/AA variant genotypes (HR, 2.0, 95% CI, 1.4-2.9 and HR, 0.4, 95% CI, 0.3-0.6, respectively) compared with their corresponding common homozygous genotypes. Furthermore, after combining the risk genotypes of the three SNPs, patients among low-risk group had a significantly lower risk of SCCOP recurrence than those in high-risk group (HR, 0.2, 95% CI, 0.1-0.3). The risk for both individual SNPs or combined risk genotypes was restricted to HPV-positive SCCOP patients. Our findings suggest that the MDM4 polymorphisms may, individually or in combination, confer an independent risk of SCCOP recurrence, particularly in HPV-positive SCCOP patients. However, larger studies are needed to validate our findings.

Clinical and genetic characterization of hereditary breast cancer in a Chinese population

BACKGROUND

Breast cancer develops as a result of multiple gene mutations in combination with environmental risk factors. Causative variants in genes such as BRCA1 and/or BRCA2 have been shown to account for hereditary nature of certain breast cancers. However,other genes, such as ATM, PALB2, BRIP1, CHEK, BARD1, while lower in frequency, may also increase breast cancer risk. There are few studies examining the role of these causative variants. Our study aimed to examine the clinical and genetic characterization of hereditary breast cancer in a Chinese population.

METHODS

We tested a panel of 27 genes implicated in breast cancer risk in 240 participants using Next-Generation Sequencing. The prevalence of genetic causative variants was determined and the association between causative variants and clinico-pathological characteristics was analyzed.

RESULTS

Causative variant rate was 19.2% in the breast cancer (case) group and 12.5% in the high-risk group. In the case group 2.5% of patients carried BRCA1 causative variant, 7.5% BRCA2 variants, 1.7% patients had MUTYH, CHEK or PALB2 variants, and 0.8% patients carried ATM, BARD1, NBN, RAD51C or TP53 variants. In the high-risk group 5.8% women carried MUTYH causative variants, 2.5% had causative variants in ATM, 1.7% patients had variants in BRCA2 and 0.8% in BARD1, BRIP1 or CDH1. There was no significant difference in the presence of causative variants among clinical stages of breast cancer, tumor size and lymph nodes status. However, eight of the 12 BRCA1/2 causative variants were found in the TNBC group.

CONCLUSIONS

We found increased genetic causative variants in the familial breast cancer group and in high-risk women with a family history of breast cancer. However, the variant MUTYH c.892-2A > G may not be directly associated with hereditary breast carcinoma.

Association of adiponectin gene polymorphisms with knee osteoarthritis

AIM

To investigate the possible relationship of adiponectin (ADIPOQ) gene polymorphisms, plasma adiponectin, and the risk of knee osteoarthritis (OA).

METHODS

A total of 398 subjects, 202 knee OA patients and 196 healthy individuals, were enrolled in the case-control study. Genotyping at +45T/G (rs2241766) and +276G/T (rs1501299) loci was performed using polymerase chain reaction-restriction fragment length polymorphism. Plasma adiponectin levels were assessed using enzyme-linked immunosorbent assay. OA severity was determined using the Kellgren-Lawrence (KL) grading system.

RESULTS

No significant associations were observed in the genotype distributions and allele frequencies at two loci of +45T/G and +276G/T polymorphisms in the ADIPOQ between knee OA patients and control subjects. There was a significant association between genotype distribution of +276G/T polymorphism and KL grade 2, 3 or 4 (P = 0.037, P = 0.046, P = 0.016, respectively). At +45T/G locus, the percentage of GG genotype was notably greater in control subjects (13.40%) compared with OA subjects (1.70%) (P = 0.023). Plasma adiponectin was markedly decreased in OA subjects compared with control subjects (P = 0.03). Likewise, circulating adiponectin in OA subjects was notably lesser than that in control subjects in GG genotype of +45T/G (P = 0.029) and +276G/T polymorphisms (P = 0.012).

CONCLUSION

Polymorphisms +45T/G and +276G/T of the ADIPOQ gene might not be responsible for OA susceptibility among Thais.

Prohibitin - At the crossroads of obesity-linked diabetes and cancer

The promoter of a gene that is selectively expressed in just a few cell types provides unique opportunities to study: (1) the pleiotropic function of a protein in two different cell types including the cell compartment specific function, and (2) the crosstalk between two cell/tissue types at the systemic level. This is not possible with a ubiquitous or a highly specific gene promoter. The adipocyte protein-2 ( aP2) is one such gene. It is primarily expressed in adipocytes, but also selectively in monocytic macrophages and dendritic cells, among various immune cell types. Thus, the adipocyte protein-2 gene promoter provides an opportunity to simultaneously manipulate adipose and immune functions in a transgenic animal. Prohibitin (PHB) is a pleiotropic protein that has roles in both adipocytes and immune cells. Adipocyte specific functions of prohibitin are mediated through its mitochondrial function, whereas its immune functions are mediated in a phosphorylation-dependent manner. We capitalized on this attribute of prohibitin to explore the crosstalk between adipose and immune functions, and to discern mitochondrial and plasma membrane-associated cell signaling functions of prohibitin, by expressing wild type prohibitin (Mito-Ob) and a phospho-mutant form of prohibitin (m-Mito-Ob) from the protein-2 gene promoter, individually. Both transgenic mice develop obesity in a sex-neutral manner, but develop obesity-related metabolic dysregulation in a male sex-specific manner. Subsequently, the male Mito-Ob mice spontaneously developed type 2 diabetes and liver cancer, whereas the male m-Mito-Ob mice developed lymph node tumors or autoimmune diabetes in a context-dependent manner. This review provides a point of view on the role of prohibitin in mediating sex differences in adipose and immune functions at the systemic level. We discuss the unique attributes of prohibitin and provide a new paradigm in adipose-immune crosstalk mediated through a pleiotropic protein. Impact statement Prohibitin (PHB) is ubiquitously expressed and plays a role in adipocyte-immune cell cross-talk. Both male and female transgenic mice expressing wild-type PHB in adipose tissue and in macrophages are obese, but only males develop diabetes and liver cancer. When the mice express PHB mutated on tyrosine-114 in adipocytes and macrophages, both males and females are still obese, but none develops liver cancer; instead, males develop lymph node tumors. Adipocyte specific functions of PHB are mediated through its mitochondrial function, whereas its immune functions are mediated in a phosphorylation-dependent manner. Thus, PHB appears to be an important molecule linking obesity, diabetes, and cancer. In addition, this link appears to be affected by sex steroids. Therefore, targeting PHB may lead to a better understanding of the pathogenesis of obesity, diabetes and cancer.

Association of 758 G/A polymorphism of 3'untranslated region of prohibitin with risk of gastric cancer

BACKGROUND

A polymorphic variant allele (T-allele) in the 3'-UTR of prohibitin (C-to-T at nucleotide 729) was reported to be associated with an increased risk of breast cancer. However, the association between the 3'-UTR polymorphism of prohibitin and the susceptibility to gastric cancer remains unknown. Thus, we investigated the distribution of prohibitin genotypes in Chinese patients with gastric cancer and subsequently analyzed the association between the 3'-UTR polymorphism of prohibitin and the risk of gastric cancer in that population.

METHODS

The distribution of 3'-UTR polymorphism of prohibitin in 82 gastric cancer patients was determined by sequencing and compared with that of 171 healthy controls. Luciferase reporter assay was used to investigate the effect of 3'-UTRs variant on PHB expression.

RESULTS

Our study discovered two major polymorphic sites in the 3'-UTR of prohibitin (C-to-T at nucleotide 729 and G to A at nucleotide 758). The C/T polymorphism at 729 site was not associated with the increased risk of gastric cancer (P=.961, OR=1.044, 95%CI: 0.187-5.818); however, G/A polymorphism at nucleotide 758 increased the risk of gastric cancer (P=.017, OR=1.923, 95%CI: 1.119-3.305). Luciferase reporter constructs containing the 758A allele showed higher luciferase activity compared with the wild-type allele, which indicated that 758 G>A in 3'-UTR increased PHB expression.

CONCLUSIONS

The G to A transition but not the C-to-T transition in the 3'-UTR of prohibitin was associated with an increased risk of gastric cancer in Chinese population.

Prohibitin 2: At a communications crossroads

Prohibitins (PHBs) are a highly conserved class of proteins first discovered as inhibitors of cellular proliferation. Since then PHBs have been found to have a significant role in transcription, nuclear signaling, mitochondrial structural integrity, cell division, and cellular membrane metabolism, placing these proteins among the key regulators of pathologies such as cancer, neuromuscular degeneration, and other metabolic diseases. The human genome encodes two PHB proteins, prohibitin 1 (PHB1) and prohibitin 2 (PHB2), which function not only as a heterodimeric complex, but also independently. While many previous reviews have focused on the better characterized prohibitin, PHB1, this review focuses on PHB2 and new data concerning its cellular functions both in complex with PHB1 and independent of PHB1.

A steroid metabolizing gene variant in a polyfactorial model improves risk prediction in a high incidence breast cancer population

Background

We have combined functional gene polymorphisms with clinical factors to improve prediction and understanding of sporadic breast cancer risk, particularly within a high incidence Caucasian population.

Methods

A polyfactorial risk model (PFRM) was built from both clinical data and functional single nucleotide polymorphism (SNP) gene candidates using multivariate logistic regression analysis on data from 5022 US Caucasian females (1671 breast cancer cases, 3351 controls), validated in an independent set of 1193 women (400 cases, 793 controls), and reassessed in a unique high incidence breast cancer population (165 cases, 173 controls) from Marin County, CA.

Results

The optimized PFRM consisted of 22 SNPs (19 genes, 6 regulating steroid metabolism) and 5 clinical risk factors, and its 5-year and lifetime risk prediction performance proved significantly superior (~ 2-fold) over the Gail model (Breast Cancer Risk Assessment Tool, BCRAT), whether assessed by odds (OR) or positive likelihood (PLR) ratios over increasing model risk levels. Improved performance of the PFRM in high risk Marin women was due in part to genotype enrichment by a CYP11B2 (-344T/C) variant.

Conclusions and general significance

Since the optimized PFRM consistently outperformed BCRAT in all Caucasian study populations, it represents an improved personalized risk assessment tool. The finding of higher Marin County risk linked to a CYP11B2 aldosterone synthase SNP associated with essential hypertension offers a new genetic clue to sporadic breast cancer predisposition.

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A polyfactorial breast cancer risk assessment model (PFRM) was built and validated.

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The optimized PFRM incorporates both genetic (22 SNPs/19 genes) and clinical risk factors.

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The PFRM was further validated in a high risk USA/Marin breast cancer population.

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This PFRM consistently performed significantly better than the BCRAT (Gail model).

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A functional aldosterone synthase SNP in PFRM improved predictive performance in Marin.

Molecular characterization, tissue expression profile and SNP analysis of the porcine NR1H4 gene

Nuclear Receptor subfamily 1, group H, member 4 (NR1H4) is a receptor for bile acids and has an important role in regulating energy metabolism in liver, muscle and adipose tissues in humans and animals. In this study, we cloned the full coding region of NR1H4 gene from porcine Longissimus dorsi by Rapid amplification of cDNA end (RACE). Results indicated that the open reading frame of NR1H4 covered 1461 bp encoding 486 amino acid residues and the deduced amino acid sequence was 91-94 % identical to that of Homo sapiens, Bos taurus, Macaca mulatta, Gorilla gorilla, and Ovis aries. Bioinformatic analysis indicated that NR1H4 contained 31 phosphorylation sites with 14 serine, 6 threonine and 11 tyrosine. One single nucleotide polymorphism (SNP) was detected by PCR-RFLP in 3' untranslated region of exon 9 (NR1H4) and the allele frequency analysis showed that A allele frequency was low among 396 pigs from five breeds. The NR1H4 mRNA expression pattern showed that NR1H4 gene was expressed highly in live and Longissimus dorsi. This work provided an important experimental basis for further research on mechanism of lipid metabolism and fat deposition in pigs.

Differential expression and regulation of prohibitin during curcumin-induced apoptosis of immortalized human epidermal HaCaT cells

Prohibitin (PHB), also known as inhibin, is important in cell proliferation, differentiation and apoptosis. This protein localizes to the inner membrane of mitochondria, where it acts as a chaperone protein, and is also found in the nucleus, where it negatively regulates transcription. The tumor-suppressive role of PHB in cell proliferation appears to be contradictory. In this study, we investigated the existence, localization and alterations in the expression of PHB in the whole cell and nuclear matrix and analyzed its co-localization with the expression products of related genes. The western blot analysis results revealed that PHB exists in the composition of nuclear matrix proteins and that the expression level of PHB is significantly increased in the whole cell and markedly decreased in the nuclear matrix after curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) treatment. The laser confocal scanning microscope results demonstrated the co-localization of PHB with p53, c-Myc, Bax, and Fas in HaCaT cells, and this co-localization region was transferred as a result of curcumin treatment. In addition, the results of the GST pull-down assay demonstrated the direct interaction of PHB with p53, c-Myc and Bax but not Fas in vitro. Results of the present study confirmed that the expression and distribution of PHB, which is a nuclear matrix protein, affect the apoptosis of HaCaT cells and its co-localization with specific gene products connected with cell apoptosis.

3' untranslated region 1630 C>T polymorphism of prohibitin increases risk of breast cancer

Background:

Prohibitin 3′ untranslated region 1630 C>T (rs6917) polymorphism creates a variant T allele that lacks the antiproliferative activity of the more common functional C allele. Previous studies indicate that women carrying the prohibitin T allele have an increased susceptibility to breast cancer. However, the role of 1630 C>T polymorphism in mRNA expression of prohibitin and its contribution to carcinogenesis in the breast remains controversial.

Methods:

Using mRNA expression data from the HapMap online database, we sought an association between prohibitin 1630 C>T polymorphism and its mRNA expression, then conducted a meta-analysis of prohibitin 1630 C>T polymorphism and risk of breast cancer.

Results:

Although no significant association was found between prohibitin 1630 C>T polymorphism and mRNA expression in lymphoblastoid cell lines from the HapMap database (P_trend = 0.543), the present meta-analysis involving 5072 cases and 4796 controls demonstrated that prohibitin 1630 C>T polymorphism was significantly correlated with breast cancer risk in allele contrast model T versus C (odds ratio [OR] 1.09, 95% confidence interval [CI] 1.01–1.18), the homozygote codominant model TT versus CC (OR 1.47, 95% CI 1.12–1.92), and the recessive model TT versus CC/CT (OR 1.45, 95% CI 1.10–1.89).

Conclusion:

Our study indicates that minor allele T of prohibitin 1630 C>T polymorphism is associated with increased susceptibility to breast cancer.

Novel germline CDK4 mutations in patients with head and neck cancer

BACKGROUND

Cyclin-dependent kinase 4 (CDK4) together with its regulatory subunit cyclin D1, governs cell cycle progression through G1 phase. Cyclin-dependent kinase inhibitors, including p16INK4A in turn regulate CDK4. In particular, deregulation of the p16/CDK4/cyclin D1 complex has been established in a variety of human tumors including gliomas, sarcomas, melanoma, breast and colorectal cancer. However, changes in CDK4 have rarely been observed.

METHOD

In this study we used a combination of PCR-SSCP and direct sequencing for mutational screening of CDK4. DNA was isolated from peripheral blood leukocyte of patients with squamous cell carcinoma of head and neck, for screening germline mutations in coding regions of CDK4.

RESULTS

Variations observed in exon 2 and 5 were three missense mutations, g5051G > C (Ser52Thr), g5095G > C (Glu67Gln), g5906C > A, g5907C > G (Pro194Ser) and novel frame shift mutations g7321_23delTGA, g7121_7122insG, g7143delG in exon 7 and 3'UTR respectively.

CONCLUSION

In conclusion, two novel mutations were found in N terminal domain which indicates that CDK4 mutation may play a major role in the development and progression of squamous cell carcinoma of head and neck.

Association of PHB 1630 C>T and MTHFR 677 C>T polymorphisms with breast and ovarian cancer risk in BRCA1/2 mutation carriers: results from a multicenter study

BACKGROUND

The variable penetrance of breast cancer in BRCA1/2 mutation carriers suggests that other genetic or environmental factors modify breast cancer risk. Two genes of special interest are prohibitin (PHB) and methylene-tetrahydrofolate reductase (MTHFR), both of which are important either directly or indirectly in maintaining genomic integrity.

METHODS

To evaluate the potential role of genetic variants within PHB and MTHFR in breast and ovarian cancer risk, 4102 BRCA1 and 2093 BRCA2 mutation carriers, and 6211 BRCA1 and 2902 BRCA2 carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2 (CIMBA) were genotyped for the PHB 1630 C>T (rs6917) polymorphism and the MTHFR 677 C>T (rs1801133) polymorphism, respectively.

RESULTS

There was no evidence of association between the PHB 1630 C>T and MTHFR 677 C>T polymorphisms with either disease for BRCA1 or BRCA2 mutation carriers when breast and ovarian cancer associations were evaluated separately. Analysis that evaluated associations for breast and ovarian cancer simultaneously showed some evidence that BRCA1 mutation carriers who had the rare homozygote genotype (TT) of the PHB 1630 C>T polymorphism were at increased risk of both breast and ovarian cancer (HR 1.50, 95%CI 1.10-2.04 and HR 2.16, 95%CI 1.24-3.76, respectively). However, there was no evidence of association under a multiplicative model for the effect of each minor allele.

CONCLUSION

The PHB 1630TT genotype may modify breast and ovarian cancer risks in BRCA1 mutation carriers. This association need to be evaluated in larger series of BRCA1 mutation carriers.

Polymorphisms of MDM4 and risk of squamous cell carcinoma of the head and neck

PURPOSE

Mouse double minute 4 (MDM4), a homolog of MDM2, is one of the key negative regulators of p53, and its amplification or overexpression contributes to carcinogenesis by inhibiting the p53 tumor suppressor activity. We investigated the association between MDM4 polymorphisms and the risk of squamous cell carcinoma of the head and neck (SCCHN).

METHODS

We genotyped three MDM4 tagging polymorphisms, two in the 3' untranslated region (rs11801299G>A and rs10900598G>T) and one in intron 1 (rs1380576C>G), in a case-control study of 1075 non-Hispanic white SCCHN patients and 1079 cancer-free controls, and evaluated their associations with SCCHN risk.

RESULTS

Although none of these three polymorphisms individually had a statistically significant effect on the risk of SCCHN, nor did their combined number of putative risk genotypes (i.e. rs11801299GG, rs1380576CG+GG, and rs10900598GG) [odds ratio (OR)=1.16; 95% confidence interval (95% CI) =0.93-1.45], we found that individuals with 1-3 risk genotypes had statistically significant increased risk of oropharyngeal cancer (OR=1.32; 95% CI=1.00-1.73), particularly for those with T1-2 stage (OR=1.40; 95% CI=1.02-1.94), those with regional lymph node metastases (N1-3) (OR=1.44; 95% CI=1.07-1.95), and those with late stages (III and IV) (OR=1.34; 95% CI=1.01-1.77).

CONCLUSION

These results suggest that the joint effect of MDM4 variants may contribute to the risk of oropharyngeal cancer in non-Hispanic whites. Additional studies are warranted to unravel whether the particular stage distribution of oropharyngeal cancer with the strongest association (T1-2, N1-3, and III-IV) is a possible link with human papillomavirus-related oropharyngeal cancers.

Modifying effect of MDM4 variants on risk of HPV16-associated squamous cell carcinoma of oropharynx

BACKGROUND

The p53 pathway plays a critical role in maintaining genomic stability and preventing tumor formation. Given the roles of both MDM4 and HPV16 E6 oncoproteins in inhibition of p53 activity, we tested the hypothesis that MDM4 polymorphisms are associated with the risk of HPV16-associated squamous cell carcinoma of head and neck (SCCHN).

METHODS

Genotyping was conducted on 3 tagging single nucleotide polymorphisms (rs11801299 G>A, rs10900598 G>T, and rs1380576 C>G) in MDM4, and serology was used to determine HPV 16 exposure in 380 cases and 335 cancer-free controls that were frequency-matched by age, sex, smoking, and drinking status.

RESULTS

None of 3 MDM4 polymorphisms alone was significantly associated with risk of overall SCCHN. With further analysis stratified by HPV16 serology and tumor site, we found that each polymorphism individually modified the risk of HPV16-associated squamous cell carcinoma of the oropharynx (SCCOP), and such effect modification was particularly pronounced in never smokers and never drinkers.

CONCLUSION

The risk of HPV16-associated SCCOP could be modified by MDM4 polymorphisms. Large and prospective studies are needed to validate our findings.

The role and therapeutic potential of prohibitin in disease

Prohibitin 1 (PHB1), a pleiotropic protein in the cell, has been implicated in the regulation of proliferation, apoptosis, transcription, mitochondrial protein folding, and as a cell-surface receptor. This diverse array of functions of PHB1 is attributed to the cell type studied and its subcellular localization. This review discusses recent data that indicate a diverse role of PHB1 in disease pathogenesis and suggest that targeting PHB1 may be a potential therapeutic option for treatment of diseases including cancer, inflammatory bowel disease, insulin resistance/type 2 diabetes, and obesity. These diseases are associated with increased oxidative stress and mitochondrial dysfunction and therefore, the role of PHB1 in both responses will also be discussed.

Prohibitins are required for cancer cell proliferation and adhesion

Prohibitin 1 (PHB1) is a highly conserved protein that together with its homologue prohibitin 2 (PHB2) mainly localizes to the inner mitochondrial membrane. Although it was originally identified by its ability to inhibit G1/S progression in human fibroblasts, its role as tumor suppressor is debated. To determine the function of prohibitins in maintaining cell homeostasis, we generated cancer cell lines expressing prohibitin-directed shRNAs. We show that prohibitin proteins are necessary for the proliferation of cancer cells. Down-regulation of prohibitin expression drastically reduced the rate of cell division. Furthermore, mitochondrial morphology was not affected, but loss of prohibitins did lead to the degradation of the fusion protein OPA1 and, in certain cancer cell lines, to a reduced capability to exhibit anchorage-independent growth. These cancer cells also exhibited reduced adhesion to the extracellular matrix. Taken together, these observations suggest prohibitins play a crucial role in adhesion processes in the cell and thereby sustaining cancer cell propagation and survival.

Adiponectin gene SNP276 variants and central obesity confer risks for hyperglycemia in indigenous Taiwanese

This cross-sectional study analyzed the effects of two single nucleotide polymorphisms (SNP) of the adiponectin gene, SNP45 and SNP276, on hyperglycemia in indigenous Taiwanese, and whether central obesity modulates the effects of these SNPs. Overall, 550 indigenous Taiwanese were recruited for this cross-sectional study. The subjects were categorized into a hyperglycemic group if fasting plasma glucose was > 126 mg/dL (n = 88) or the control group if fasting plasma glucose was < 100 mg/dL (n = 462). The SNP276 TT homozygote carried greater hyperglycemia risk than SNP276 GG [odds ratio (OR) = 2.67, 95% confidence interval (CI) = 1.05-6.78], but not heterozygote (OR = 1.54, 95% CI = 0.95-2.50). SNP45 T > G was not associated with hyperglycemia risk. In multivariate-adjusted modeling, we found a significant relationship between SNP276 T carriers (GT + TT) (OR = 2.06, 95% CI = 1.10-3.88) and central obesity (OR = 4.50, 95% CI = 1.91-10.61) with hyperglycemia. Compared with non-central-obese carriers of SNP276 GG, non-central-obese SNP276 T carriers, and central obese subjects with SNP276 GG and SNP276 T carriers had 5.50, 8.31 and 13.76-fold, respectively, higher risks for hyperglycemia; obese carriers of the T-containing variants experienced a combined risk for hyperglycemia. Furthermore, the hyperglycemic risks were more pronounced in leaner (non-central-obese) individuals carrying the T variant than the central-obese individuals. The adiponectin SNP276 T variant and central obesity had independent and additive effects on hyperglycemia risks. These findings may provide valuable information regarding preventive strategies that might be useful to prevent or treat diabetes and its related complications.

Do BRCA1 modifiers also affect the risk of breast cancer in non-carriers?

We studied whether or not single nucleotide polymorphisms (SNPs), which have been shown to modify the risk of breast cancer in women with a BRCA1 mutation, are associated with cancer risk in unselected (non-hereditary) breast cancer patients. We genotyped seven SNPs in six distinct genes (PHB, RAD51, ITGB3, TGFB1, VEGF, MTHFR) in 1100 unselected Polish breast cancer patients and 1100 controls. The frequencies of genotypes were similar in cases and controls. In a subgroup analysis, we found a positive association between the homozygous genotype PHB 1630C/T and medullary breast cancer (odds ratio (OR)=4.0, 95% confidence interval (CI) 1.1-14.0). PHB 1630C/T was also associated with tumours negative for oestrogen receptor (OR=2.2, 95% CI 1.13-4.4) or progesterone receptor (OR=2.8, 95% CI 1.4-5.8). Our results show that, in general, the single nucleotide polymorphisms which modify the risk of hereditary breast cancer in Poland do not modify the risk of sporadic breast cancer. The PHB 1630 C/T single nucleotide polymorphism was associated with breast cancers with clinical features typical for BRCA1-positive tumours and is deserving of further study.

The response of human colonocytes to folate deficiency in vitro: functional and proteomic analyses

Low folate intake is associated with colon cancer. We combined a proteomics and biochemical approach to identify proteins and pathways affected by folate deficiency in human colonocytes. Folate differentially altered activity and expression of proteins involved in proliferation [e.g., PCNA], DNA repair [e.g., XRCC5, MSH2], apoptosis [e.g., BAG family chaperone protein, DIABLO and porin], cytoskeletal organization [e.g., actin, ezrin, elfin], and expression of proteins implicated in malignant transformation [COMT, Nit2].

Ovarian cancer risk in Polish BRCA1 mutation carriers is not associated with the prohibitin 3' untranslated region polymorphism

BACKGROUND

The variable penetrance of ovarian cancer in BRCA1 mutation carriers suggests that other genetic or environmental factors modify disease risk. The C to T transition in the 3' untranslated region of the prohibitin (PHB) gene alters mRNA function and has recently been shown to be associated with hereditary breast cancer risk in Polish women harbouring BRCA1 mutations.

METHODS

To investigate whether the PHB 3'UTR polymorphism also modifies hereditary ovarian cancer risk, we performed a case-control study among Polish women carrying one of the three common founder mutations (5382insC, 300 T > G, 4154delA) including 127 ovarian cases and 127 unaffected controls who had both breasts and ovaries intact. Controls were matched to cases by year of birth and BRCA1 mutation. Genotyping analysis was performed using PCR-based restriction fragment length polymorphism analysis. Odds ratios (OR) were calculated using conditional and penalized univariable and multivariable logistic regression.

RESULTS

A comparison of the genotype frequencies between cases and controls revealed no association of the PHB 3'UTR _CT+TT genotypes with ovarian cancer risk (ORadj 1.34; 95% CI, 0.59-3.11).

CONCLUSION

Our data suggest that the PHB 3'UTR polymorphism does not modify ovarian cancer risk in women carrying one of the three Polish BRCA1 founder mutations.

Ovarian cancer survival and polymorphisms in hormone and DNA repair pathway genes

We evaluated the association between 21 polymorphisms in hormone and DNA repair pathway genes and survival among 454 Australian women diagnosed with invasive epithelial ovarian cancer. The cohort was followed for mortality using personal identifiers which were linked to state cancer registry records and the Australian National Death Index. The mean follow-up time after ovarian cancer diagnosis was 4.63 years (all women) and 8.07 years for the censored group (those alive or dead from non-ovarian cancer causes). Two hundred and eighty-eight (63%) ovarian cancer deaths occurred during the follow-up period. No association was observed for the vast majority of polymorphisms, but there was suggestive evidence for altered risk of ovarian cancer death associated with the CYP17 5'UTR C allele (HR 1.30; 95% CI=1.02-1.68, p= 0.04), and for the SRD5A2 V89L C allele (HR 0.79; 95% CI=0.62-1.01, p=0.06). These results are interesting given tentative evidence that both of these variants are also associated with increased predisposition to ovarian cancer in our extended Australian study, and in other published studies. However, given the marginal significance of these associations and the large number of tests performed, independent replication will be necessary to validate these novel findings.

The prohibitin genes in Arabidopsis thaliana: expression in seeds, hormonal regulation and possible role in cell cycle control during seed germination

A fragment encoding a partial sequence of a prohibitin (Phb) gene was isolated. The expression of Phb mRNA and protein in seeds of wild type and mutant Arabidopsis thaliana is presented. Phb mRNA is abundant in wild-type seeds; thus, it may have sequence or structural characteristics responsible for this stability. The 3' untranslated region sequence of a Phb gene has interesting features. We found that Arabidopsis Phb does not interact with a retinoblastoma-related protein or E2F in a yeast two-hybrid system, thus suggesting that the plant protein may have not conserved such interaction, described for mammalian Phb. The possible role of Phb in cell cycle regulation during germination is discussed.

The 3′ untranslated region C > T polymorphism of prohibitin is a breast cancer risk modifier in Polish women carrying a BRCA1 mutation

The variable penetrance of breast cancer in BRCA1 mutation carriers suggests that other genetic or environmental factors modify breast cancer risk. The C to T transition in the 3' untranslated region of the prohibitin (PHB) gene alters mRNA function and has been shown to be associated with an increased breast cancer risk among young North-American women who have one first-degree relative with breast cancer. To investigate whether the PHB 3'UTR polymorphism acts as a modifier of hereditary breast cancer risk we performed a case-control study among female BRCA1 mutation carriers, which included 258 cases and 258 controls who were unaffected by ovarian cancer, in situ breast carcinoma or any other type of cancer. Controls were matched to cases by year of birth and BRCA1 mutation (5382insC, 300 T > G, 4153delA). Genotyping analysis was performed using RFLP-PCR. Odds ratios (OR) were calculated using conditional and penalised univariable and multivariable logistic regression. Multivariable penalised logistic regression revealed CT (OR(adj), 2.03; 95% CI, 1.17-3.59) and combined CT + TT (OR(adj), 2.12; 95% CI, 1.23-3.70) genotypes as significant modifiers of breast cancer risk. Breast cancer risk did not differ between carriers of the 300 T > G and 5382insC mutation. Our results suggest that the PHB 3'UTR T allele increases the risk of breast cancer in patients who are already at increased risk of disease.

A systematic analysis of disease-associated variants in the 3' regulatory regions of human protein-coding genes II: the importance of mRNA secondary structure in assessing the functionality of 3' UTR variants

In an attempt both to catalogue 3' regulatory region (3' RR)-mediated disease and to improve our understanding of the structure and function of the 3' RR, we have performed a systematic analysis of disease-associated variants in the 3' RRs of human protein-coding genes. We have previously analysed the variants that have occurred in two specific domains/motifs of the 3' untranslated region (3' UTR) as well as in the 3' flanking region. Here we have focused upon 83 known variants within the upstream sequence (USS; between the translational termination codon and the upstream core polyadenylation signal sequence) of the 3' UTR. To place these variants in their proper context, we first performed a comprehensive survey of known cis-regulatory elements within the USS and the mechanisms by which they effect post-transcriptional gene regulation. Although this survey supports the view that RNA regulatory elements function within the context of specific secondary structures, there are no general rules governing how secondary structure might exert its influence. We have therefore addressed this question by systematically evaluating both functional and non-functional (based upon in vitro reporter gene and/or electrophoretic mobility shift assay data) USS variant-containing sequences against known cis-regulatory motifs within the context of predicted RNA secondary structures. This has allowed us not only to establish a reliable and objective means to perform secondary structure prediction but also to identify consistent patterns of secondary structural change that could potentiate the discrimination of functional USS variants from their non-functional counterparts. The resulting rules were then used to infer potential functionality in the case of some of the remaining functionally uncharacterized USS variants, from their predicted secondary structures. This not only led us to identify further patterns of secondary structural change but also several potential novel cis-regulatory motifs within the 3' UTRs studied.

Prohibitin mutations are uncommon in prostate cancer families linked to chromosome 17q

BACKGROUND

Linkage studies have provided evidence for a prostate cancer susceptibility locus on chromosome 17q. The mitochondrial protein prohibitin (PHB) is a plausible candidate gene based on its chromosomal location (17q21) and known function.

METHODS

All coding regions and intron/exon junctions of the PHB gene were sequenced in 32 men from families participating in the University of Michigan Prostate Cancer Genetics Project that demonstrated evidence of linkage to 17q markers.

RESULTS

Although a number of nucleotide variants were identified, no coding region substitutions were identified in any of the 32 men with prostate cancer from 32 unrelated multiplex prostate cancer families.

CONCLUSIONS

PHB mutations do not appear to account for the linkage signal on 17q21-22 detected in PCGP families. Fine mapping of this region is in progress to refine the candidate region and highlight additional candidate prostate cancer susceptibility genes for sequence analysis.

Camptothecin induces nuclear export of prohibitin preferentially in transformed cells through a CRM-1-dependent mechanism

Prohibitin is a growth-suppressive protein that has multiple functions in the nucleus and the mitochondria. Our earlier studies had shown that prohibitin represses the activity of E2F transcription factors while enhancing p53-mediated transcription. At the same time, prohibitin has been implicated in mediating the proper folding of mitochondrial proteins. We had found that treatment of cells with camptothecin, a topoisomerase 1 inhibitor, led to the export of prohibitin and p53 from the nucleus to the mitochondria. Here we show that the camptothecin-induced export of prohibitin occurs preferentially in transformed cell lines, but not in untransformed or primary cells. Cells that did not display the translocation of prohibitin were refractive to the apoptotic effects of camptothecin. The translocation was mediated by a putative nuclear export signal at the C-terminal region of prohibitin; fusion of the nuclear export signal (NES) of prohibitin to green fluorescence protein led to its export from the nucleus. Leptomycin B could inhibit the nuclear export of prohibitin showing that it was a CRM-1-dependent event driven by Ran GTPase. Confirming this, prohibitin was found to physically interact with CRM-1, and this interaction was significantly higher in transformed cells. Delivery of a peptide corresponding to the NES of prohibitin prevented the export of prohibitin to cytoplasm and protected cells from apoptosis. These results suggest that the regulated translocation of prohibitin from the nucleus to the mitochondria facilitates its pleiotropic functions and might contribute to its anti-proliferative and tumor suppressive properties.

Resistin gene 3'-untranslated region +62G-->A polymorphism is associated with hypertension but not diabetes mellitus type 2 in a German population

OBJECTIVES

Resistin, a peptide hormone produced by adipocytes, has been associated with diabetes mellitus type 2 (DM-2) in some rodent models. In humans the exact function of resistin remains unknown. Some, but not all studies have found associations between polymorphisms in the resistin gene with DM-2. Recently a 3'-untranslated region +62G-->A polymorphism of the resistin gene has been associated with decreased risk for DM-2 and for hypertension in diabetics in a Chinese population. Purpose of the present study was to examine for the first time in a German Caucasian population the possible association between this polymorphism and DM-2, hypertension, lipoprotein levels, resistin levels as well as atherosclerosis.

DESIGN, SETTING AND SUBJECTS

A total of 818 subjects participated in the study. The presence of the +62G-->A polymorphism of the resistin gene was investigated using polymerase chain reaction-restriction fragment length polymorphism in 384 subjects with DM-2 [224 men, 160 women, age 63.4 +/- 10.6 years, body mass index (BMI) 28.7 +/- 5.1 kg m(-2)] and in 434 nondiabetic age- and sex-matched control subjects (248 men, 186 women, age 64.4 +/- 6.5 years, BMI 26.5 +/- 3.7 kg m(-2)).

RESULTS

Thirty-four subjects were found to be carrying the +62G-->A polymorphism in the control and 24 in the diabetic group (allelic frequencies 4% and 3.2% respectively). Subjects with DM-2 were not found to have a different frequency of the genotypes (93.75% and 6.258%, for GG:GA/AA respectively) than the control subjects (92.2% and 7.8% for GG:GA/AA respectively) (OR 0.75, 95% CI 0.44-1.3, P = 0.31). In the total cohort, carriers of the A allele had a higher prevalence of hypertension (OR 1.82, 95% CI 1.03-3.21, P = 0.039). When analysed separately, the control group showed a strong association between the presence of the A allele and hypertension (OR 2.92, 95% CI 1.38-6.15, P = 0.005), whilst no such association could be established in the diabetic group (OR 1.05, 95% CI 0.43-2.54, P = 0.92). Multiple regression analysis confirmed that the presence of the A variant is associated with hypertension in control but not in diabetic subjects, independent of age and BMI. The polymorphism had no significant influence on the presence of atherosclerotic disease, BMI, and on triglyceride, HDL and LDL cholesterol levels, both, in the control and the diabetic groups. There was no difference in the serum resistin levels between the 62G-->A variant carriers and noncarriers.

CONCLUSIONS

In conclusion, the present data suggest that in a German Caucasian population the +62G-->A polymorphism of the resistin gene is associated with hypertension but not with DM-2.

Polymorphism at 3' UTR +28 of the prion-like protein gene is associated with sporadic Creutzfeldt-Jakob disease

The downstream prion-like protein (doppel or Dpl) shares significant biochemical and structural homology with the cellular prion protein, PrP(C), which is considered as a responsible protein for the transmissible spongiform encephalopathies (TSEs) or prion diseases. Recently, polymorphisms in open reading frame (ORF) of the prion-like protein gene (PRND) have been analysed in relation to the occurrence of prion diseases and other neurodegenerative disorders. We examined the role of a single-nucleotide polymorphism (SNP) at 3' untranslated region (UTR) +28 of PRND. We analysed this polymorphism in 110 Korean patients with sporadic Creutzfeldt-Jakob disease (CJD) and 102 healthy control subjects. Significant differences in genotype (P=0.005) and allele (P=0.032) frequencies at 3' UTR +28 were observed between sporadic CJD and normal controls. This result suggests that the PRND polymorphism at 3' UTR +28 might be associated with the occurrence of sporadic CJD.

Prohibitin: a potential target for new therapeutics

Prohibitin (PHB) is localized to the mitochondria where it might have a role in the maintenance of mitochondrial function and protection against senescence. There is considerable controversy concerning the function of nuclear-localized PHB. PHB has potential roles as a tumor suppressor, an anti-proliferative protein, a regulator of cell-cycle progression and in apoptosis. PHB might also function as a cell-surface receptor for an as-yet unidentified ligand. Cell-associated PHB in the gastrointestinal tract has been implicated in protection against infection and inflammation and the induction of apoptosis in other tissues. The diverse array of functions of PHB, together with the emerging evidence that its function can be modulated specifically in certain tissues, suggest that targeting PHB would be a useful therapeutic approach for the treatment of variety of disease states, including inflammation, obesity and cancer.

Expression of prohibitin 3' untranslated region suppressor RNA alters morphology and inhibits motility of breast cancer cells

The prohibitin 3' untranslated region (3'UTR) belongs to a novel class of non-coding regulatory RNAs. It arrests cell cycle progression by blocking G1-S transition in breast and other cancers. Our previous studies comparing MCF7 derived clones constitutively expressing a common allelic form of prohibitin RNA (UTR/C) to various controls demonstrated that it functions as a tumor suppressor. Here, we further characterized the morphology and motility of these transgenic breast cancer cells when grown in cell culture and on nude mice. In contrast to empty vector (EV) cells, UTR/C cells were observed to grow in an organized manner with more cell-cell contact and differentiate into structures with a duct-like appearance. Computer assisted cytometry to evaluate differences in nuclear morphology was performed on UTR/C and EV tissues from nude mice. Receiver operator curve areas generated using a logistic regression model were 0.8, indicating the ability to quantitatively distinguish UTR/C from EV tissues. Keratinocyte growth factor-induced motility experiments showed that migration of UTR/C cells was significantly reduced (80-90%) compared to EV cells. Together, these data indicate that this novel 3'UTR influences not only the tumorigenic phenotype but also may play a role in differentiation and migration of breast cancer cells.

Oligogenic combinations associated with breast cancer risk in women under 53 years of age

Common, but weakly penetrant, functional polymorphisms probably account for most of the genetic risk for breast cancer in the general population. Current polygenic risk models assume that component genes act independently. To test for potential gene-gene interactions, single nucleotide polymorphisms in ten genes with known or predicted roles in breast carcinogenesis were examined in a case-control study of 631 Caucasian women diagnosed with breast cancer under the age of 53 years and 1,504 controls under the age of 53 years. Association of breast cancer risk with individual genes and with two- and three-gene combinations was analyzed. Sixty-nine oligogenotypes from 37 distinct two- and three-gene combinations met stringent criteria for significance. Significant odds ratios (ORs) covered a 12-fold range: 0.5-5.9. Of the observed ORs, 17% differed significantly from the ORs predicted by a model of independent gene action, suggesting epistasis, i.e., that these genes interact to affect breast cancer risk in a manner not predictable from single gene effects. Exploration of the biological basis for these oligogenic interactions might reveal etiologic or therapeutic insights into breast cancer and other cancers.

Regulation of Prohibitin Expression During Follicular Development and Atresia in the Mammalian Ovary1

Prohibitin is a ubiquitous and highly conserved protein implicated as an important regulator in cell survival. Prohibitin content is inversely associated with cell proliferation, but it increases during granulosa cell differentiation as well as in earlier events of apoptosis in a temperature-sensitive granulosa cell line. In the present study, we have characterized the spatial expression patterns for prohibitin using established in vivo models for the induction of follicular development and atresia in the mammalian ovary. Comparative Western blot analyses of granulosa cell lysates from control ovaries and from ovaries primed with eCG or treated with eCG plus anti-eCG (gonadotropin withdrawal) were conducted. Prohibitin was immunolocalized in rat ovarian sections probed with antibodies against either proliferating cell nuclear antigen (PCNA) or cholesterol side-chain cleavage cytochrome P450 (P450(scc)) or in terminal deoxynucleotidyl transferase-mediated dUTP nick end labeled sections. Additionally, porcine oocytes, zygotes, and blastocyts were also immunolocalized with prohibitin antibody. Immunolocalization revealed the presence of prohibitin in granulosa cells, theca-interstitial cells, and the oocyte. The results indicate that prohibitin protein expression in the gonadotropin-treated cells was upregulated. Immunoreactivity of prohibitin was inversely related to PCNA expression during follicular maturation and colocalized with P450(scc). Prohibitin appeared to be translocated from the cytoplasm to the nucleus in atretic follicles, germinal vesicle-stage oocytes, zygotes, and blastocysts. These results suggest that prohibitin has several functional regulatory roles in granulosa and theca-interstitial cells and in the ovum during follicular maturation and atresia. It is likely that prohibitin may play an important role in determining the fate of these cells and eventual follicular destiny.

Association of the human adiponectin gene and insulin resistance

Adiponectin is an adipocyte-secreted protein that modulates insulin sensitivity and whose low circulating concentration is associated with insulin resistance. In the present study, we analysed the association between two single-nucleotide polymorphisms (SNPs) in the adiponectin gene and insulin resistance in 253 nondiabetic subjects. In addition, we investigated whether this association is modulated by body mass index (BMI) levels. The SNPs +45T>G and +276G>T in the human adiponectin gene were detected in real-time PCR with LightCycler. No association was found with the +45T>G SNP. The +276G>T SNP was associated with higher BMI (P<0.01), plasma insulin (P<0.02) and HOMA(IR) (P<0.02). To analyse the possible interaction between BMI and the adiponectin gene on insulin resistance, the study group was divided into two subgroups, according to the BMI below or above the median of 26.2 kg/m(2). In both subgroups, subjects carrying the +276G>T SNP had higher HOMA(IR); however, the difference was highly significant among leaner (P<0.001), but not among heavier individuals, indicating that BMI status and the adiponectin gene interact in modulating insulin resistance. Among individuals with BMI <26.2 kg/m(2), the relative risk of insulin resistance was 9.7 (CI: 1.32-87.7, P<0.035). In a subgroup of 67 subjects, carriers of the +276G>T SNP had significantly (P<0.05) lower mean serum adiponectin levels (25.7 ng/ml) compared to noncarriers (37.0 ng/ml), suggesting a possible influence of the +276G>T SNP on adiponectin levels. In summary, we observed an association between the +276G>T SNP in the adiponectin gene and insulin resistance. In particular, among leaner individuals, the adiponectin gene appears to determine an increased risk to develop insulin resistance.

Chemoresistance in human ovarian cancer: the role of apoptotic regulators

Ovarian cancer is among the most lethal of all malignancies in women. While chemotherapy is the preferred treatment modality, chemoresistance severely limits treatment success. Recent evidence suggests that deregulation of key pro- and anti-apoptotic pathways is a key factor in the onset and maintenance of chemoresistance. Furthermore, the discovery of novel interactions between these pathways suggests that chemoresistance may be multi-factorial. Ultimately, the decision of the cancer cell to live or die in response to a chemotherapeutic agent is a consequence of the overall apoptotic capacity of that cell. In this review, we discuss the biochemical pathways believed to promote cell survival and how they modulate chemosensitivity. We then conclude with some new research directions by which the fundamental mechanisms of chemoresistance can be elucidated.

Common gene polymorphisms and nutrition: emerging links with pathogenesis of multifactorial chronic diseases (review)

Rapid progress in human genome decoding has accelerated search for the role of gene polymorphisms in the pathogenesis of complex multifactorial diseases. This review summarizes the results of recent studies on the associations of common gene variants with multifactorial chronic conditions strongly affected by nutritional factors. Three main individual sections discuss genes related to energy homeostasis regulation and obesity, cardiovascular disease (CVD), and cancer. It is evident that several major chronic diseases are closely related (often through obesity) to deregulation of energy homeostasis. Multiple polymorphic genes encoding central and peripheral determinants of energy intake and expenditure have been revealed over the past decade. Food intake control may be affected by polymorphisms in the genes encoding taste receptors and a number of peripheral signaling peptides such as insulin, leptin, ghrelin, cholecystokinin, and corresponding receptors. Polymorphic central regulators of energy intake include hypothalamic neuropeptide Y, agouti-related protein, melanocortin pathway factors, CART (cocaine- and amphetamine-regulated transcript), some other neuropeptides, and receptors for these molecules. Potentially important polymorphisms in the genes encoding energy expenditure modulators (alpha- and beta- adrenoceptors, uncoupling proteins, and regulators of adipocyte growth and differentiation) are also discussed. CVD-related gene polymorphisms comprising those involved in the pathogenesis of atherosclerosis, blood pressure regulation, hemostasis control, and homocysteine metabolism are considered in a separate section with emphasis on multiple polymorphisms affecting lipid transport and metabolism and their interactions with diet. Cancer-associated polymorphisms are discussed for groups of genes encoding enzymes of xenobiotic metabolism, DNA repair enzymes, factors involved in the cell cycle control, hormonal regulation-associated proteins, enzymes related to DNA methylation through folate metabolism, and angiogenesis-related factors. There is an apparent progress in the field with hundreds of new gene polymorphisms discovered and characterized, however firm evidence consistently linking them with pathogenesis of complex chronic diseases is still limited. Ways of improving the efficiency of candidate gene approach-based studies are discussed in a short separate section. Successful unraveling of interaction between dietary factors, polymorphisms, and pathogenesis of several multifactorial diseases is exemplified by studies of folate metabolism in relation to CVD and cancer. It appears that several new directions emerge as targets of research on the role of genetic variation in relation to diet and complex chronic diseases. Regulation of energy homeostasis is a fundamental problem insufficiently investigated in this context so far. Impacts of genetic variation on systems controlling angiogenesis, inflammatory reactions, and cell growth and differentiation (comprising regulation of the cell cycle, DNA repair, and DNA methylation) are also largely unknown and need thorough analysis. These goals can be achieved by complex simultaneous analysis of multiple polymorphic genes controlling carefully defined and selected elements of relevant metabolic and regulatory pathways in meticulously designed large-scale studies.

The prohibitin 3' untranslated region polymorphism is not associated with risk of ovarian cancer

OBJECTIVE

The 3' untranslated region of the prohibitin gene encodes an RNA molecule that arrests cell proliferation between the G(1) and S phases of the cell cycle, and a C-to-T transition within this region creates a variant lacking antiproliferative activity. The T allele was reported to be associated with an increased risk of breast cancer in North American women, specifically in those under age 50 years reporting a first-degree family history of breast cancer. We assessed the association of the prohibitin 3' untranslated region polymorphism with risk of ovarian cancer in the Australian population by case-control comparison.

METHODS

We examined 553 cases of epithelial ovarian cancer and 300 unaffected controls to assess whether this polymorphism was associated with risk of ovarian cancer in Australian women. Genotyping was carried out using the Perkin-Elmer ABI Prism 7700 Sequence Detection System for fluorogenic polymerase chain reaction allelic discrimination. Genotype distributions were compared by logistic regression.

RESULTS

Stratification of the ovarian cancer cases according to tumour behavior (low malignant potential or invasive), histology, grade, stage, or p53 immunohistochemical status failed to reveal any heterogeneity with respect to prohibitin genotype. There was no difference in genotype distribution between cases and controls, with an odds ratio (95% confidence interval) of 0.99 (0.72-1.35) for the CT/TT genotype.

CONCLUSION

The prohibitin T variant does not appear to be associated with risk of ovarian cancer in Australian women.

Comparative proteomic profiling of murine skin

Mammalian skin is regularly exposed to different environmental stresses, each of which results in specific compensatory changes in protein expression that can be assessed by proteomic analysis. We have established a reference proteome map of BALB/c murine skin allowing the resolution of greater than 500 protein spots in a single two-dimensional polyacrylamide gel. Forty-four protein spots, corresponding to 28 different cutaneous proteins, were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and the Mascot online database searching algorithm. Twenty-five proteins were expressed at higher levels in the epidermis, whereas only nine were found predominantly in the subepidermal tissues. A subset of protein spots exhibited strain-specific expression. Proteins of diverse function were identified, including those involved in stress response, apoptosis, growth inhibition, the maintenance of structural integrity, translational control, energy metabolism, calcium binding, cholesterol transport, and the scavenging of free radicals. Prohibitin expression was detected cutaneously, with more abundant protein and mRNA levels in the epidermis. Five molecular chaperones including protein di-sulfide isomerase, 78 kDa glucose-regulated protein precursor, heat shock protein 60 (HSP60), HSP70, and HSP27 were also identified. Of these, HSP27 expression was confined mainly to the epidermis, and expression of protein disulfide isomerase was found primarily in the subepidermal tissues. Proteomic analysis of skin following heat or cold shock resulted in increased levels of HSP27, HSP60, and HSP70 suggesting involvement of these chaperones in the cutaneous response mechanism to temperature stress. These data establish numerous reference markers within the proteome map of murine skin and provide an important framework for future efforts aimed at characterization of the epidermal and subepidermal responses to environmental changes.

Gonadotropin-releasing hormone attenuates pregnancy-associated thymic involution and modulates the expression of antiproliferative gene product prohibitin

Thymic involution during pregnancy is believed to be a critical adaptive mechanism for regulation and control of the maternal immune system. These regulatory feedback mechanisms are important for the survival of the semiallogeneic fetus. In the present study, we examined the effects of GnRH on pregnancy-induced thymic involution by characterizing the expression patterns of prohibitin (PHB), an antiproliferative gene product, GnRH, and GnRH receptor (GnRH-R) proteins in the rat thymus and in mature splenic lymphocytes. GnRH agonist infusions in pregnant rats markedly attenuated pregnancy-induced thymic involution resulting in significant increases in thymic weight and thymocyte numbers. In addition, histological examination of the thymus revealed increase in cortical cellularity. Western blot analyses revealed a significant increase of total PHB protein content in thymi during pregnancy. Furthermore, distinct changes in PHB isoform expression were observed in the pregnant involuting thymi with greater expression of the basic PHB isoform. Basic isoform expression decreased in pregnant rats and was comparable with nonpregnant rat thymi upon GnRH agonist treatment. PHB is mainly expressed in mature cells of the thymic medulla, where it strongly colocalized with GnRH. We have observed GnRH-R immunoreactivity mainly in thymic medulla. Furthermore, as assessed by immunofluorescence double labeling with proliferating cell nuclear antigen, PHB was preferentially expressed in nonproliferating thymocytes. In this study, we demonstrated that GnRH, GnRH-R, and PHB show characteristic polarized expression in thymocytes. In addition, GnRH and PHB were coexpressed in mature splenic T cells. Our results suggest that PHB and GnRH are involved in thymic growth and may be important for maturation of T lymphocytes.