Talc use, variants of the GSTM1, GSTT1, and NAT2 genes, and risk of epithelial ovarian cancer

A systematic review of the epidemiology evidence on talc and cancer

Over the past several decades, there have been many epidemiology studies on talc and cancer published in the scientific literature, and several reviews and meta-analyses of talc and respiratory, female reproductive, and stomach cancers, specifically. To help provide a resource for the evaluation of talc as a potential human carcinogen, we applied a consistent set of examination methods and criteria for all epidemiology studies that examined the association between talc exposure (by various routes) and cancers (of various types). We identified 30 cohort, 35 case-control, and 12 pooled studies that evaluated occupational, medicinal, and personal-care product talc exposure and cancers of the respiratory system, the female reproductive tract, the gastrointestinal tract, the urinary system, the lymphohematopoietic system, the prostate, male genital organs, and the central nervous system, as well as skin, eye, bone, connective tissue, peritoneal, and breast cancers. We tabulated study characteristics, quality, and results in a systematic manner, and evaluated all cancer types for which studies of at least three unique populations were available in a narrative review. We focused on study quality aspects most likely to impact the interpretation of results. We found that only one study, of medicinal talc use, evaluated direct exposure measurements for any individuals, though some used semi-quantitative exposure metrics, and few studies adequately assessed potential confounders. The only consistent associations were with ovarian cancer in case-control studies and these associations were likely impacted by recall and potentially other biases. This systematic review indicates that epidemiology studies do not support a causal association between occupational, medicinal, or personal talc exposure and any cancer in humans.

Prevention of Epithelial Ovarian Cancer

Given the challenges with achieving effective and durable treatment for epithelial ovarian cancer, primary prevention is highly desirable. Fortunately, decades of research have provided evidence for several strategies that can be deployed to optimize risk reduction. These include surgery, chemoprevention, and lifestyle factor modifications. These broad categories vary in terms of the magnitude of risk reduction possible, the possible short-term and long-term side effects, the degree of difficulty, and acceptability. Thus, the concept of a risk-based model to personalize preventive interventions is advocated to guide discussion between care providers and women at risk. For women with inherited major gene mutations that greatly increase risk of ovarian cancer, surgical approaches have favorable risk to benefit ratios. Chemoprevention and lifestyle factor modifications portend a lower degree of risk reduction but confer lower risk of undesirable side effects. Since complete prevention is not currently possible, better methods for early detection remain a high priority.

Individual effects of GSTM1 and GSTT1 polymorphisms on cervical or ovarian cancer risk: An updated meta-analysis

Background: Studies have shown that glutathione S-transferase M1 (GSTM1) and. glutathione S-transferase T1 (GSTT1) null genotype may increase the risk of cervical cancer (CC) or ovarian cancer (OC), however, the results of published original studies and meta-analyses are inconsistent. Objectives: To investigate the association between GSTM1 present/null and GSTT1 present/null polymorphisms, with the risk of cervical cancer or ovarian cancer. Methods: The odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the association between GSTM1 present/null and GSTT1 present/null polymorphisms and the risk of cervical cancer or ovarian cancer. To assess the confidence of statistically significant associations, we applied false positive reporting probability (FPRP) and bayesian false discovery probability (BFDP) tests. Results: Overall analysis showed that GSTM1 null was associated with an increased risk of cervical cancer, and subgroup analysis showed a significant increase in cervical cancer risk in Indian and Chinese populations; GSTT1 was not found null genotype are significantly associated with cervical cancer. Overall analysis showed that GSTM1 and GSTT1 null were not associated with the risk of ovarian cancer, subgroup analysis showed that GSTM1 null was associated with an increased risk of OC in East Asia, and GSTT1 null was associated with an increased risk of OC in South America. However, when we used false positive reporting probability and bayesian false discovery probability to verify the confidence of a significant association, all positive results showed "low confidence" (FPRP > .2, BFDP > .8). Conclusion: Overall, this study strongly suggests that all positive results should be interpreted with caution and are likely a result of missing plausibility rather than a true association.

Douching or Perineal Talc Use and Prevalent Fibroids in Young African American Women

Background: Black women are at an increased risk of developing fibroids, but the cause is unclear. Douching and perineal talc use are common lifestyle exposures among Black women, and may be risk factors for fibroid development. Materials and Methods: This cross-sectional study consisted of Black women 23-35 years of age in the metropolitan Detroit area (n = 1693) without prior diagnoses of fibroids and intact uteri. Main exposures were ever douching (yes/no) and any perineal talc use (ever/never). Main outcomes were prevalent fibroids at baseline (yes/no) and total fibroid volume at baseline (no fibroids/ Collapse

Key Words

• Women's Health
• douching
• health disparities
• talc
• uterine leiomyoma

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MESH Headings

• Black or African American
• Cross-Sectional Studies
• Female
• Humans
• Leiomyoma/epidemiology
• Prospective Studies
• Talc/adverse effects
• Therapeutic Irrigation
• Uterine Neoplasms

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Grants

• R00 NR017191 NINR NIH HHS

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Affiliation(s)

Maya A. Wright Department of Epidemiology, University of North Carolina at Chapel Hill, Gillings School of Global Public Health, Chapel Hill, North Carolina, USA
Kristen R. Moore Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
Kristen Upson Department of Epidemiology and Biostatistics, College of Human Medicine, Michigan State University, East Lansing, Michigan, USA
Donna D. Baird Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
Helen B. Chin Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA

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Cancer risk and nullity of Glutathione-S-transferase mu and theta 1 in occupational pesticide workers

Occupational exposure to pesticides has been associated with adverse health conditions, including genotoxicity and cancer. Nullity of GSTT1/GSTM1 increases the susceptibility of pesticide workers to these adverse health effects due to lack of efficient detoxification process created by the absence of these key xenobiotic metabolizing enzymes. However, this assertion does not seem to maintain its stance at all the time; some pesticide workers with the null genotypes do not present the susceptibility. This suggests the modulatory role of other confounding factors, genetic and environmental conditions. Pesticides, aggravated by the null GSTT1/GSTM1, cause genotoxicity and cancer through oxidative stress and miRNA dysregulation. Thus, the absence of these adverse health effects together with the presence of null GSTT1/GSTM1 genotypes demands further explanation. Also, understanding the mechanism behind the protection of cells - that are devoid of GSTT1/GSTM1 - from oxidative stress constitutes a great challenge and potential research area. Therefore, this review article highlights the recent advancements in the presence and absence of cancer risk in occupational pesticide workers with GSTT1 and GSTM1 null genotypes.

Talc, body powder, and ovarian cancer: A summary of the epidemiologic evidence

Many women apply powder to the genital area as a drying agent. Talc, an inert mineral with a high capacity to absorb water, has historically been a major component of body powders. Due to its similarity and co-occurrence with asbestos, the association of body powder/talc use and gynecological cancer risk, specifically ovarian cancer risk, has been a long-standing research question. Retrospective case-control studies have shown associations between genital powder use and ovarian cancer risk, with summary relative risk estimates from meta-analyses and pooled analyses ranging from 1.24 to 1.35 for ever versus never use. In contrast, prospective cohort studies have not shown a statistically significant association until recently, when a pooled analysis of four large cohorts demonstrated a weak, but statistically significant association among women with patent reproductive tracts (hazard ratio 1.13). Taken together, the epidemiological data from case-control studies and cohort studies suggest that there may be a small, positive association between genital powder use and ovarian cancer. The causal factors underlying this association are not clear. Proposed factors include talc, other minerals, such as asbestos or quartz, that are known carcinogens and may contaminate talc products, or other powder ingredients that could cause inflammation of the reproductive tracts. Given the rarity of ovarian cancer in the general population, the small increase in relative risk translates to a very low increase in absolute risk. Further research is needed to understand the underpinnings of the observed association between genital powder use and ovarian cancer risk.

Serous Ovarian Cancer Caused by Exposure to Asbestos and Fibrous Talc in Cosmetic Talc Powders-A Case Series

OBJECTIVE

Asbestos is a known cause of ovarian cancer. We report 10 cases of serous ovarian cancer among users of Johnson & Johnson (J&J) asbestos-containing "cosmetic" talc products.

METHODS

We conducted an asbestos exposure assessment during talc application and analyzed surgical tissues and talc containers for asbestos and talc.

RESULTS

Talc was found in all cases and tremolite and/or anthophyllite asbestos was found in 8/10 cases. The asbestos fibers found in the "cosmetic" talc containers matched those found in tissues. We estimated inhaled asbestos dose ranged from 0.38 to 5.18 fiber years.

CONCLUSION

We provide evidence that the inhaled dose of asbestos/fibrous talc from "cosmetic" talc use causes ovarian cancer. The unique combination of the types of asbestiform minerals detected in cancerous tissue and "cosmetic" talc is a fingerprint for exposure to asbestos-containing talc.

A critical review of talc and ovarian cancer

The association between perineal talc use and ovarian cancer has been evaluated in several epidemiology studies. Some case-control studies reported weak positive associations, while other case-control and three large prospective cohort investigations found this association to be null. A weight-of-evidence evaluation was conducted of the epidemiology, toxicity, exposure, transport, in vitro, and mechanistic evidence to determine whether, collectively, these data support a causal association. Our review of the literature indicated that, while both case-control and cohort studies may be impacted by bias, the possibility of recall and other biases from the low participation rates and retrospective self-reporting of talc exposure cannot be ruled out for any of the case-control studies. The hypothesis that talc exposure induces ovarian cancer is only supported if one discounts the null results of the cohort studies and the fact that significant bias and/or confounding are likely reasons for the associations reported in some case-control investigations. In addition, one would need to ignore the evidence from animal experiments that show no marked association with cancer, in vitro and genotoxicity studies that did not indicate a carcinogenic mechanism of action for talc, and mechanistic and transport investigations that did not support the retrograde transport of talc to the ovaries. An alternative hypothesis that talc does not produce ovarian cancer, and that bias and confounding contribute the reported positive associations in case-control studies, is better supported by the evidence across all scientific disciplines. It is concluded that the evidence does not support a causal association between perineal talc use and ovarian cancer.

Data on systematic review and meta-analysis of epidemiologic evidence on the association between perineal use of talc powder and risk of ovarian cancer

This paper describes data from a systematic review and meta-analysis [1] conducted to identify and evaluate published peer reviewed evidence on the association between perineal use of talc powder and risk of ovarian cancer. These data were collected from multiple electronic bibliographic databases, as well as from grey literature sources, without applying time, language or other filters. A meta-analysis was conducted to quantitatively assess the ovarian cancer risk in relation to talc use and other potential risk factors.

Critical review of the association between perineal use of talc powder and risk of ovarian cancer

Over the past four decades, there has been increasing concern that perineal use of talc powder, a commonly used personal care product, might be associated with an increased risk of ovarian cancer.

OBJECTIVES

To critically review all available human epidemiological data on the relationship between perineal use of talc powder and ovarian cancer, with consideration of other relevant experimental evidence.

METHODOLOGY

We identified 30 human studies for qualitative assessment of evidence, including 27 that were retained for further quantitative analysis.

RESULTS

A positive association between perineal use of talc powder and ovarian cancer was found [OR: 1.28 (95% CI: 1.20-1.37)]. A significant risk was noted in Hispanics and Whites, in women applying talc to underwear, in pre-menopausal women and in post-menopausal women receiving hormonal therapy. A negative association was noted with tubal ligation.

CONCLUSION

Perineal use of talc powder is a possible cause of human ovarian cancer.

Mining Featured Biomarkers Linked with Epithelial Ovarian CancerBased on Bioinformatics

Epithelial ovarian cancer (EOC) is the18th most common cancer worldwide and the 8th most common in women. The aim of this study was to diagnose the potential importance of, as well as novel genes linked with, EOC and to provide valid biological information for further research. The gene expression profiles of E-MTAB-3706 which contained four high-grade ovarian epithelial cancer samples, four normal fallopian tube samples and four normal ovarian epithelium samples were downloaded from the ArrayExpress database. Pathway enrichment and Gene Ontology (GO) enrichment analysis of differentially expressed genes (DEGs) were performed, and protein-protein interaction (PPI) network, microRNA-target gene regulatory network and TFs (transcription factors) -target gene regulatory network for up- and down-regulated were analyzed using Cytoscape. In total, 552 DEGs were found, including 276 up-regulated and 276 down-regulated DEGs. Pathway enrichment analysis demonstrated that most DEGs were significantly enriched in chemical carcinogenesis, urea cycle, cell adhesion molecules and creatine biosynthesis. GO enrichment analysis showed that most DEGs were significantly enriched in translation, nucleosome, extracellular matrix organization and extracellular matrix. From protein-protein interaction network (PPI) analysis, modules, microRNA-target gene regulatory network and TFs-target gene regulatory network for up- and down-regulated, and the top hub genes such as E2F4, SRPK2, A2M, CDH1, MAP1LC3A, UCHL1, HLA-C (major histocompatibility complex, class I, C), VAT1, ECM1 and SNRPN (small nuclear ribonucleoprotein polypeptide N) were associated in pathogenesis of EOC. The high expression levels of the hub genes such as CEBPD (CCAAT enhancer binding protein delta) and MID2 in stages 3 and 4 were validated in the TCGA (The Cancer Genome Atlas) database. CEBPD andMID2 were associated with the worst overall survival rates in EOC. In conclusion, the current study diagnosed DEGs between normal and EOC samples, which could improve our understanding of the molecular mechanisms in the progression of EOC. These new key biomarkers might be used as therapeutic targets for EOC.

GSTT1 and GSTM1 null variants in Mestizo and Amerindian populations from northwestern Mexico and a literature review

The GSTT1 and GSTM1 genes are key molecules in cellular detoxification. Null variants in these genes are associated with increase susceptibility to developing different types of cancers. The aim of this study was to determine the prevalence of GSTT1 and GSTM1 null genotypes in Mestizo and Amerindian individuals from the Northwestern region of Mexico, and to compare them with those reported worldwide. GSTT1 and GSTM1 null variants were genotyped by multiplex PCR in 211 Mestizos and 211 Amerindian individuals. Studies reporting on frequency of GSTT1 and GSTM1 null variants worldwide were identified by a PubMed search and their geographic distribution were analyzed. We found no significant differences in the frequency of the null genotype for GSTT1 and GSM1 genes between Mestizo and Amerindian individuals. Worldwide frequencies of the GSTT1 and GSTM1 null genotypes ranges from 0.10 to 0.51, and from 0.11 to 0.67, respectively. Interestingly, in most countries the frequency of the GSTT1 null genotype is common or frequent (76%), whereas the frequency of the GSMT1 null genotype is very frequent or extremely frequent (86%). Thus, ethnic-dependent differences in the prevalence of GSTT1 and GSTM1 null variants may influence the effect of environmental carcinogens in cancer risk.

Racial health disparities in ovarian cancer: not just black and white

Ovarian cancer (OC) is the most lethal gynecological malignancy, which disproportionately affects African American (AA) women. Lack of awareness and socioeconomic factors are considered important players in OC racial health disparity, while at the same time, some recent studies have brought focus on the genetic basis of disparity as well. Differential polymorphisms, mutations and expressions of genes have been reported in OC patients of diverse racial and ethnic backgrounds. Combined, it appears that neither genetic nor the socioeconomic factors alone might explain the observed racially disparate health outcomes among OC patients. Rather, a more logical explanation would be the one that takes into consideration the combination and/or the interplay of these factors, perhaps even including some environmental ones. Hence, in this article, we attempt to review the available information on OC racial health disparity, and provide an overview of socioeconomic, environmental and genetic factors, as well as the epigenetic changes that can act as a liaison between the three. A better understanding of these underlying causes will help further research on effective cancer management among diverse patient population and ultimately narrow health disparity gaps.

Epidemiology of ovarian cancer: a review

Ovarian cancer (OC) is the seventh most commonly diagnosed cancer among women in the world and the tenth most common in China. Epithelial OC is the most predominant pathologic subtype, with five major histotypes that differ in origination, pathogenesis, molecular alterations, risk factors, and prognosis. Genetic susceptibility is manifested by rare inherited mutations with high to moderate penetrance. Genome-wide association studies have additionally identified 29 common susceptibility alleles for OC, including 14 subtype-specific alleles. Several reproductive and hormonal factors may lower risk, including parity, oral contraceptive use, and lactation, while others such as older age at menopause and hormone replacement therapy confer increased risks. These associations differ by histotype, especially for mucinous OC, likely reflecting differences in etiology. Endometrioid and clear cell OC share a similar, unique pattern of associations with increased risks among women with endometriosis and decreased risks associated with tubal ligation. OC risks associated with other gynecological conditions and procedures, such as hysterectomy, pelvic inflammatory disease, and polycystic ovarian syndrome, are less clear. Other possible risk factors include environmental and lifestyle factors such as asbestos and talc powder exposures, and cigarette smoking. The epidemiology provides clues on etiology, primary prevention, early detection, and possibly even therapeutic strategies.

Epidemiology of ovarian cancer: a review

Ovarian cancer (OC) is the seventh most commonly diagnosed cancer among women in the world and the tenth most common in China. Epithelial OC is the most predominant pathologic subtype, with five major histotypes that differ in origination, pathogenesis, molecular alterations, risk factors, and prognosis. Genetic susceptibility is manifested by rare inherited mutations with high to moderate penetrance. Genome-wide association studies have additionally identified 29 common susceptibility alleles for OC, including 14 subtype-specific alleles. Several reproductive and hormonal factors may lower risk, including parity, oral contraceptive use, and lactation, while others such as older age at menopause and hormone replacement therapy confer increased risks. These associations differ by histotype, especially for mucinous OC, likely reflecting differences in etiology. Endometrioid and clear cell OC share a similar, unique pattern of associations with increased risks among women with endometriosis and decreased risks associated with tubal ligation. OC risks associated with other gynecological conditions and procedures, such as hysterectomy, pelvic inflammatory disease, and polycystic ovarian syndrome, are less clear. Other possible risk factors include environmental and lifestyle factors such as asbestos and talc powder exposures, and cigarette smoking. The epidemiology provides clues on etiology, primary prevention, early detection, and possibly even therapeutic strategies.

Lack of any association of GST genetic polymorphisms with susceptibility to ovarian cancer--a meta-analysis

OBJECTIVE

Epidemiology studies have reported conflicting results between glutathione S-transferase Mu-1 (GSTM1), glutathione S-transferase theta-1 (GSTT1) and glutathione S-transferase pi-1 (GSTP1) and ovarian cancer (OC) susceptibility. In this study, an updated meta-analysis was applied to determine whether the deletion of GSTM1, GSTT1 and GSTP1 has an influence on OC susceptibility.

METHODS

A published literature search was performed through PubMed, Embase, Cochrane Library, and Science Citation Index Expanded database for articles published in English. Pooled odds ratios (ORs) and 95% confidence intervals (95%CIs) were calculated using random or fixed effects models. Heterogeneity between studies was assessed using the Cochrane Q test and I2 statistics. Sub-group analysis was conducted to explore the sources of heterogeneity. Sensitivity analysis was employed to evaluate the respective influence of each study on the overall estimate.

RESULTS

In total, 10 published studies were included in the final analysis. The combined analysis revealed that there was no significant association between GSTM1 null genotype and OC risk (OR=1.01, 95%CI: 0.91-1.12). Additionally, there was no significant association between GSTT1 genetic polymorphisms and OC risk (OR=0.98, 95% CI: 0.85-1.13). Similalry, no significant associations were found concerning the GSTP1 rs1695 locus and OC risk. Meanwhile, subgroup analysis did not show a significant increase in eligible studies with low heterogeneity. However, sensitivity analysis, publication bias and cumulative analysis demonstrated the reliability and stability of the current meta-analysis.

CONCLUSIONS

These findings suggest that GSTs genetic polymorphisms may not contribute to OC susceptibility. Large epidemiological studies with the combination of GSTM1 null, GSTT1 null and GSTP1 Ile105Val polymorphisms and more specific histological subtypes of OC are needed to prove our findings.

The Association Between Talc Use and Ovarian Cancer: A Retrospective Case-Control Study in Two US States

Supplemental Digital Content is available in the text.

Multiple studies of ovarian cancer and genital talc use have led only to consensus about possible carcinogenicity. Seeking greater clarity, we examined this association in 2,041 cases with epithelial ovarian cancer and 2,100 age- and-residence-matched controls.

Epidemiology of ovarian cancer: a review

Ovarian cancer (OC) is the seventh most commonly diagnosed cancer among women in the world and the tenth most common in China. Epithelial OC is the most predominant pathologic subtype, with five major histotypes that differ in origination, pathogenesis, molecular alterations, risk factors, and prognosis. Genetic susceptibility is manifested by rare inherited mutations with high to moderate penetrance. Genome-wide association studies have additionally identified 29 common susceptibility alleles for OC, including 14 subtype-specific alleles. Several reproductive and hormonal factors may lower risk, including parity, oral contraceptive use, and lactation, while others such as older age at menopause and hormone replacement therapy confer increased risks. These associations differ by histotype, especially for mucinous OC, likely reflecting differences in etiology. Endometrioid and clear cell OC share a similar, unique pattern of associations with increased risks among women with endometriosis and decreased risks associated with tubal ligation. OC risks associated with other gynecological conditions and procedures, such as hysterectomy, pelvic inflammatory disease, and polycystic ovarian syndrome, are less clear. Other possible risk factors include environmental and lifestyle factors such as asbestos and talc powder exposures, and cigarette smoking. The epidemiology provides clues on etiology, primary prevention, early detection, and possibly even therapeutic strategies.

Review of the Gene-Environment Interaction Literature in Cancer: What Do We Know?

BACKGROUND

Risk of cancer is determined by a complex interplay of genetic and environmental factors. Although the study of gene-environment interactions (G×E) has been an active area of research, little is reported about the known findings in the literature.

METHODS

To examine the state of the science in G×E research in cancer, we performed a systematic review of published literature using gene-environment or pharmacogenomic flags from two curated databases of genetic association studies, the Human Genome Epidemiology (HuGE) literature finder and Cancer Genome-Wide Association and Meta Analyses Database (CancerGAMAdb), from January 1, 2001, to January 31, 2011. A supplemental search using HuGE was conducted for articles published from February 1, 2011, to April 11, 2013. A 25% sample of the supplemental publications was reviewed.

RESULTS

A total of 3,019 articles were identified in the original search. From these articles, 243 articles were determined to be relevant based on inclusion criteria (more than 3,500 interactions). From the supplemental search (1,400 articles identified), 29 additional relevant articles (1,370 interactions) were included. The majority of publications in both searches examined G×E in colon, rectal, or colorectal; breast; or lung cancer. Specific interactions examined most frequently included environmental factors categorized as energy balance (e.g., body mass index, diet), exogenous (e.g., oral contraceptives) and endogenous hormones (e.g., menopausal status), chemical environment (e.g., grilled meats), and lifestyle (e.g., smoking, alcohol intake). In both searches, the majority of interactions examined were using loci from candidate genes studies and none of the studies were genome-wide interaction studies (GEWIS). The most commonly reported measure was the interaction P-value, of which a sizable number of P-values were considered statistically significant (i.e., <0.05). In addition, the magnitude of interactions reported was modest.

CONCLUSION

Observations of published literature suggest that opportunity exists for increased sample size in G×E research, including GWAS-identified loci in G×E studies, exploring more GWAS approaches in G×E such as GEWIS, and improving the reporting of G×E findings.

Safety Assessment of Talc as Used in Cosmetics

The Cosmetic Ingredient Review Expert Panel (Panel) assessed the safety of talc for use in cosmetics. The safety of talc has been the subject of much debate through the years, partly because the relationship between talc and asbestos is commonly misunderstood. Industry specifications state that cosmetic-grade talc must contain no detectable fibrous, asbestos minerals. Therefore, the large amount of available animal and clinical data the Panel relied on in assessing the safety of talc only included those studies on talc that did not contain asbestos. The Panel concluded that talc is safe for use in cosmetics in the present practices of use and concentration (some cosmetic products are entirely composed of talc). Talc should not be applied to the skin when the epidermal barrier is missing or significantly disrupted.

Microarray enriched gene rank

Background

We develop a new concept that reflects how genes are connected based on microarray data using the coefficient of determination (the squared Pearson correlation coefficient). Our gene rank combines a priori knowledge about gene connectivity, say, from the Gene Ontology (GO) database, and the microarray expression data at hand, called the microarray enriched gene rank, or simply gene rank (GR). GR, similarly to Google PageRank, is defined in a recursive fashion and is computed as the left maximum eigenvector of a stochastic matrix derived from microarray expression data. An efficient algorithm is devised that allows computation of GR for 50 thousand genes with 500 samples within minutes on a personal computer using the public domain statistical package R.

Results

Computation of GR is illustrated with several microarray data sets. In particular, we apply GR (1) to answer whether bad genes are more connected than good genes in relation with cancer patient survival, (2) to associate gene connectivity with cluster/subtypes in ovarian cancer tumors, and to determine whether gene connectivity changes (3) from organ to organ within the same organism and (4) between organisms.

Conclusions

We have shown by examples that findings based on GR confirm biological expectations. GR may be used for hypothesis generation on gene pathways. It may be used for a homogeneous sample or for comparison of gene connectivity among cases and controls, or in longitudinal setting.

Genetic polymorphisms and gene-dosage effect in ovarian cancer risk and response to paclitaxel/cisplatin chemotherapy

Background

Ovarian malignancies are often diagnosed in advanced stage and at the same time resistance to treatment, both intrinsic and developed during treatment, is sometimes observed. These facts underscore the need for new markers of ovarian cancer risk, as well as markers of treatment effectiveness.

Methods

In this study we genotyped 225 ovarian cancer patients, 64 breast and ovarian cancer patients and 348 healthy controls. In total, 12 polymorphic variants and 2 deletions in PGR, ABCB1, ABCG2, GSTT1, GSTM1, GSTP1, ATM, TP53 and ATP7B genes were analyzed using ASA-PCR, RFLP-PCR, multiplex-PCR and sequencing.

Results

Ten genetic polymorphisms were significantly associated with the risk of developing ovarian carcinoma in at least one of the groups under study. Impact of PGR gene polymorphisms on ovarian cancer risk was specific only for the group of the BRCA1 mutation carriers (in presence of p.Val660Leu variant- OR 2,82; p = 0,010), which confirms the difference in modulation of ovarian cancer risk between sporadic and hereditary malignancies, including the breast-ovarian cancer group (as a cancer-prone group). The analyses showed also the importance of ATP7B gene in ovarian carcinogenesis, both studied variants of which significantly modulated the ovarian cancer risk in all groups excluding the group with BRCA1 mutation. Cumulative risk analysis revealed 3 unfavorable variants that increased significantly the risk of developing ovarian cancer (p.Ile1145 = ABCB1+ p.Asp1853Asn ATM+ p.Ser406Ala ATP7B- OR 7,47; p = 0,002) and significantly modified the progression free survival (PFS) of the patients, and also two favorable genotypes which protected against ovarian cancer (p.Arg952Lys ATP7B+ p.Arg72Pro TP53- OR 0,50; p = 0,008). PFS analysis for carriers of favorable versus unfavorable genotypes emphasized the impact of the regulation of cell cycle (p.Asp1853Asn ATM) and active transport of xenobiotics (p.Ser894Ala/Thr ABCB1) on the risk of disease progression (HR 3,81; p = 0,010) after paclitaxel/cisplatin chemotherapy.

Conclusions

The unfavorable genetic variants could facilitate carcinogenic process and once their carriers developed malignancy, their chances of survival were smaller. Our analyses also showed a strong gene-dosage effect with the decrease of progression-free survival for the carriers of two unfavorable genetic factors.

Cytotoxicity and apoptosis induction by nanoscale talc particles from two different geographical regions in human lung epithelial cells

We have characterized the physicochemical properties of nanotalc particles from two different geographical regions and examined their toxicity mechanisms in human lung epithelial (A549) cells. Indigenous nanotalc (IN) of Indian origin and commercial nanotalc (CN) of American origin were used in this study. Physicochemical properties of nanotalc particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), Brunauer-Emmet-Teller (BET), and dynamic light scattering (DLS). Results showed that both IN and CN particles significantly induce cytotoxicity and alteration in cell cycle phases. Both IN and CN particles were found to induce oxidative stress indicated by induction of reactive oxygen species (ROS), lipid peroxidation, and depletion of antioxidant levels. DNA fragmentation and caspase-3 enzyme activation due to IN and CN particles exposure were also observed. We further showed that after iron chelation, IN and CN particles produce significantly less cytotoxicity, oxidative stress, and genotoxicity to A549 cells as compared with nonchelated particles. In conclusion, this study demonstrated that redox active iron plays significant role in the toxicity of IN and CN particles, which may be mediated through ROS generation and oxidative stress.

Polymorphisms of glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) in ovarian cancer risk

Glutathione S-transferases (GSTs) are ubiquitous, multifunctional phase II metabolic enzymes responsible for the detoxification of estrogen involved in the development of ovarian cancer. Data from epidemiological studies show conflicting results that remain to be further clarified. We estimated in this study the genetic effects of GSTM1 and GSTT1 polymorphisms on ovarian cancer risk. Eligible studies of the two polymorphisms and ovarian cancer risk were identified from China National Knowledge Infrastructure (CNKI), PubMed, Embase, and Web of Science. We summarized all data and performed a meta-analysis. Odds ratio (OR) and 95 % CI was calculated by using the fixed effects model to estimate the associations. Eight eligible studies were finally identified providing 2,397 cases and 2,910 controls for GSTM1 polymorphism and 2,049 cases and 2,668 controls for GSTT1 polymorphism. The overall data showed that carries of the GSTM1 null genotype did not have significantly increased ovarian cancer risk compared with those who carried the GSTM1 present genotype (null vs. present-OR, 1.01; 95 % CI, 0.91-1.11; heterogeneity, P=0.672). Similarly, for GSTT1 polymorphism, we observed no association under the investigated model in the overall analysis (null vs. present-OR, 1.02; 95 % CI, 0.89-1.17; heterogeneity, P=0.372), and in the subgroup of Caucasian subjects (null vs. present-OR, 0.99; 95 % CI, 0.86-1.14; heterogeneity, P=0.959). The meta-analysis does not provide a strong evidence for causal associations between GSTM1 and GSTT1 polymorphisms and risk of ovarian cancer in Caucasians.

Assessing ovarian cancer risk when considering elective oophorectomy at the time of hysterectomy

OBJECTIVE

To develop a risk-factor score that may provide additional guidance to women and their physicians regarding elective bilateral salpingo-oophorectomy at the time of hysterectomy.

METHODS

From a case-control study conducted from 1992 to 2008 in women residing in eastern Massachusetts or New Hampshire, we selected 1,098 women with invasive ovarian cancer (case group) and 1,363 for the control group who were older than 40 years and had neither hysterectomy nor a personal or family history of breast or ovarian cancer. Using logistic regression, we identified key risk factors and built a risk score. The score was separately assessed in 126 women in the case group and 156 in the control group with excluded prior hysterectomy to determine whether women who developed ovarian cancer could have been distinguished.

RESULTS

Summing eight conditions found to be associated with ovarian cancer (Jewish ethnicity, less than 1 year of oral contraceptive use, nulliparity, no breastfeeding, no tubal ligation, painful periods or endometriosis, polycystic ovary syndrome or obesity, talc use), we created a five-level score. Assigning average risk to those with a score of 2, the odds ratios varied from 0.56 (95% confidence interval [CI] 0.42-0.74) for a score of 0-1 to 3.30 (95% CI 2.50-4.35) for a score of 5 or greater (P trend <.001). The risk score was higher for women who developed ovarian cancer after hysterectomy than those who did not (P=.01). Lifetime risks for ovarian cancer for a woman at age 40 years are changed from 1.2% with a 0-1 score to 6.6% with a score of 5 or higher.

CONCLUSION

We developed a risk-assessment tool that can quantify women's risk for ovarian cancer and should be validated in other data sets.

Does bilateral salpingectomy with ovarian retention warrant consideration as a temporary bridge to risk-reducing bilateral oophorectomy in BRCA1/2 mutation carriers?

Risk-reducing salpingo-oophorectomy (RRSO) is the most definitive surgical intervention for ovarian cancer risk reduction among BRCA1/2 mutation carriers. For women who have completed child-bearing but who are not ready for RRSO, bilateral salpingectomy with ovarian retention (BSOR) might serve as a temporary measure while definitive risk-reducing surgery is being contemplated. Here we summarize recent insights into the pathogenesis of hereditary ovarian cancer that might provide a basis for consideration of the proposed BSOR management strategy and outline the evidence for and against this potential risk-reducing intervention. Based on the evidence, we suggest that there may be sufficient merit in this proposed intervention to consider evaluating it formally, perhaps through an intergroup-based clinical trial. In the meanwhile, we believe that BSOR should be considered an investigational risk management option of unproven clinical usefulness, particularly because delay in bilateral oophorectomy theoretically could reduce the protective effect against breast cancer that has been documented in women who have undergone RRSO.

Glutathione S-transferase M1, T1, and P1 polymorphisms and ovarian cancer risk: a meta-analysis

INTRODUCTION

Cytosolic glutathione S-transferase (GST) comprises multiple isoenzymes that catalyze reactions between glutathione and lipophilic compounds with electrophilic centers, resulting in the neutralization of toxic compounds, xenobiotics, and products of oxidative stress. Several studies have examined whether GST polymorphisms (GSTM1 null/present genotype, GSTT1 null/present genotype, and GSTP1 Ile105Val) represent risk factors for ovarian cancer, as they all may denote reduced enzyme activity. This meta-analysis aimed to examine the associations between the aforementioned polymorphisms and ovarian cancer risk.

METHODS

The MEDLINE database was searched up to September 2009 using the appropriate terms. Case-control studies with no mutually overlapping populations were selected. Pooled odds ratios (ORs) were appropriately derived from fixed-effects or random-effects models. Meta-regression with publication year was also performed.

RESULTS

Eight studies regarding GSTM1 null polymorphism status (2357 cases and 3044 controls), 6 studies concerning GSTT1 null polymorphism (1923 cases and 2759 controls), and 3 studies on GSTP1 Ile105Val were included in the meta-analysis. The GSTM1 null genotype was not associated with an increased risk for ovarian cancer (pooled OR, 1.031; 95% confidence interval, 0.867-1.226; random effects). The GSTT1 null genotype was not associated with an increased ovarian cancer risk (pooled OR, 0.934; 95% confidence interval, 0.804-1.086; random effects); similarly, no significant associations were demonstrated for GSTP1 Ile105Val.

CONCLUSIONS

The examined GSTM1, GSTT1, and GSTP1 genotype polymorphisms do not seem to confer any additional risk for ovarian cancer. Given that the studies included in this meta-analysis involve mainly white populations, these results cannot be extrapolated on other populations, and additional data are needed for future race-specific analyses.

Interaction between use of non-steroidal anti-inflammatory drugs and selected genetic polymorphisms in ovarian cancer risk

Inflammation and non-steroidal anti-inflammatory agents (NSAIDs) may play important role in ovarian cancer. However, epidemiologic data are inconsistent, possibly reflecting inter-individual genetic differences affecting the metabolism of NSAIDs. We examined whether common polymorphisms affecting the metabolism of NSAIDs modify the association between NSAIDs and ovarian cancer risk. We genotyped 1,353 DNA samples from women who developed ovarian cancer and 1,823 samples from matched controls participating in the New England Case-Control study and the Nurses' Health Studies. Conditional logistic regression estimated odds ratios (ORs) and 95% confidence intervals (CIs) associated with regular use of NSAIDs and with relevant polymorphisms on ovarian cancer risk. Multivariable unconditional logistic regression estimated the association of NSAID use across stratum of each genotype. Regular use of NSAIDs was not associated with ovarian cancer risk. Multivariable OR (95% CI) associated with use NSAIDs was 0.85 (95% CI: 0.71-1.02). Associations between NSAID use and ovarian cancer risk did not differ significantly across strata of genotypes. None of the studied polymorphisms was associated with ovarian cancer risk. The multivariable ORs (95% CI) associated with CYP2C9 and UGT1A6 variant genotypes were 0.99 (0.90-1.08) and 0.93 (0.82-1.05), respectively. The multivariable ORs (95% CI) associated with PPAR-γ, COX-2 -765G>C, and COX-2 Ex10+837T>C polymorphisms were 1.02 (0.87-1.20), 0.87 (0.75-1.00), and 0.97 (0.87-1.09), respectively. In this relatively large study, we found no convincing evidence supporting an association between NSAIDs use and ovarian cancer risk. Furthermore, data did not suggest interaction between selected polymorphisms and use of NSAIDs in relation to ovarian cancer risk.

Perineal use of talcum powder and endometrial cancer risk

BACKGROUND

Several studies have reported a positive association between perineal use of talcum powder among adult women and ovarian cancer risk. However, the relationship between talcum powder use and other gynecologic malignancies such as endometrial cancer has not been examined, and little information is available on nonhormonal risk factors for endometrial cancer.

METHODS

Perineal use of talcum powder was assessed in 1982 in the Nurses' Health Study. Approximately 40% of women who responded to the questions about perineal use of talcum powder reported ever use. Cox proportional hazards models were used to estimate the incidence rate ratio of endometrial cancer and 95% confidence interval (CI), adjusted for body mass index and other potential confounders. We evaluated the relationship among all women and stratified by menopausal status.

RESULTS

Our analysis included 66,028 women with 599 incident cases of invasive endometrial adenocarcinoma diagnosed between 1982 and 2004. Although no association was observed overall, the association varied by menopausal status (P interaction=0.02) and a positive association was observed among postmenopausal women; ever use of talcum powder was associated with a 21% increase in risk of endometrial cancer (95% CI, 1.02-1.44), whereas regular use (at least once a week) was associated with a 24% increase in risk (95% CI, 1.03-1.48). In addition, we observed a borderline increase in risk with increasing frequency of use (P trend=0.04).

CONCLUSIONS

Our results suggest that perineal talcum powder use increases the risk of endometrial cancer, particularly among postmenopausal women.

IMPACT

Future and larger studies are needed to confirm this association and investigate potential mechanisms.

Common genetic variation in IGF1, IGFBP1 and IGFBP3 and ovarian cancer risk

Insulin-like growth factor (IGF) 1 and its binding proteins foster cellular proliferation and inhibit apoptosis. In vitro studies show that IGF1 increases ovarian cell growth and invasive potential, suggesting a role for the IGF1 pathway in ovarian cancer etiology. We evaluated genetic variation in the IGF1, IGFBP1 and IGFBP3 genes in relation to ovarian cancer risk by genotyping 29 haplotype-tagging single nucleotide polymorphisms in 1173 cases and 1201 controls from the New England Case-Control (NECC) study and 296 cases and 854 controls from the Nurses' Health Study (NHS). The association of haplotypes and single nucleotide polymorphisms (SNPs) with ovarian cancer was estimated using unconditional (NECC) and conditional (NHS) logistic regression. Additionally, we evaluated the association of SNPs with IGF1, IGF-binding protein (IGFBP) 3 and IGFBP2 plasma levels (n = 380 NHS controls). Our data suggest a decreased risk for women carrying haplotype 2C of the IGF1 gene [odds ratios (ORs) = 0.82, 95% confidence intervals (CIs) = 0.69-0.98] and an increased risk for women carrying haplotype 1D (OR = 1.41, 95% CI = 1.03-1.94) or 2D (OR = 1.20, 95% CI = 1.01-1.41) in the binding proteins. When evaluated individually, three SNPs in the IGFBPs (rs10228265, rs4988515 and rs2270628) were associated with increased ovarian cancer risk, and several IGF1 (rs11111285, rs1996656 and rs1019731) and IGFBP3 (rs2270628, rs2854746 and rs2854744) SNPs were significantly associated with IGF1, IGFBP3 and IGFBP2 plasma levels. Some haplotypes and SNPs in the IGF pathway genes may be associated with ovarian cancer risk; however, these results need to be confirmed. Of particular interest was the IGFBP3 SNP rs2270628, which was associated with both increased IGF1 plasma levels and higher ovarian cancer risk.

Current understanding of risk factors for ovarian cancer

OPINION STATEMENT

Ovarian cancer is the deadliest gynecologic cancer. Unlike many cancers such as breast, cervical and colon cancers, there is no easily clinically identifiable pre-malignant phase of this malignancy making early identification difficult. Similarly, unlike lung, head and neck, and skin cancers, there is not easily identifiable risk factor making prevention short of oophorectomy difficult. Even so, theories as to the causative factors of ovarian cancer continue to evolve making our understanding of the genesis of ovarian cancer more clear. Genetics, parity, environment, hormonal factors, and inflammation all play an important and pivotal role in the development of ovarian cancer. The most current understanding of these elements and their respective contribution to the development of this cancer are presented in this chapter.

Polymorphisms in the vitamin D receptor and risk of ovarian cancer in four studies

Prior studies have suggested that vitamin D may reduce ovarian cancer risk. Thus, we examined whether three single nucleotide polymorphisms (SNP) in the vitamin D receptor (VDR) gene (Fok1, Bsm1, Cdx2) were associated with risk of epithelial ovarian cancer in a retrospective case-control study (New England Case-Control study, NECC) and a nested case-control study of three prospective cohort studies: the Nurses' Health Study (NHS), NHSII, and the Women's Health Study. Data from the cohort studies were combined and analyzed using conditional logistic regression and pooled with the results from the NECC, which were analyzed using unconditional logistic regression, using a random effects model. We obtained genotype data for 1,473 cases and 2,006 controls. We observed a significant positive association between the number of Fok1 f alleles and ovarian cancer risk in the pooled analysis (P(trend) = 0.03). The odds ratio (OR) for the ff versus FF genotype was 1.26 [95% confidence interval (CI) = 1.01-1.57]. Neither the Bsm1 (P(trend) = 0.96) or Cdx2 (P(trend) = 0.13) SNPs were significantly associated with ovarian cancer risk. Among the prospective studies, the risk of ovarian cancer by plasma vitamin D levels did not clearly vary by any of the genotypes. For example, among women with the Fok1 FF genotype, the OR comparing plasma 25-hydroxyvitamin D >or=32 ng/mL versus <32 ng/mL was 0.66 (95% CI, 0.34-1.28), and among women with the Ff or ff genotype the OR was 0.71 (95% CI, 0.43-1.18). Our results of an association with the Fok1 VDR polymorphism further support a role of the vitamin D pathway in ovarian carcinogenesis.

Coffee intake, variants in genes involved in caffeine metabolism, and the risk of epithelial ovarian cancer

We evaluated whether genetic variability, as well as menopausal status, modify the association between coffee intake and risk of ovarian cancer. Risk factor information and biologic specimens from three large epidemiological studies, the Nurses' Health Study (NHS), NHSII, and the New England based Case-Control Study of ovarian cancer (NECC) were pooled resulting in 1,354 ovarian cancer cases and 1,851 controls for analysis. Odds ratios (ORs) and 95% confidence intervals (CI) were estimated using conditional (NHS/NHSII) and unconditional (NECC) logistic regression. Coffee consumption was not associated with overall risk (OR = 0.99; 95% CI 0.77-1.28); however, there was a suggested increased risk of ovarian cancer among premenopausal women in the NECC only and an inverse association among postmenopausal women. Carrying one or both of the variant CYP19013 A or CYP19027 G alleles was associated with an 18% increased (P for trend = 0.02) and 15% decreased (P for trend = 0.05) risk of ovarian cancer, respectively. Variation in CYP1A1, CYP1A2, or CYP2A6 did not explain the inconsistent reports of coffee intake and risk. Furthermore, we did not observe any clear gene-environment interactions between caffeine metabolizing genes and ovarian cancer. Future studies evaluating mechanisms by which coffee mediates this relationship are warranted.