Outer breast quadrants demonstrate increased levels of genomic instability

Mathematical Modeling of Field Cancerization through the Lens of Cancer Behavioral Ecology

Field cancerization is a process in which a normal tissue is replaced with pre-cancerous but histologically normal tissue. This transformed field can give rise to malignancy and contribute to tumor relapse. In this paper, we create a mathematical model of field cancerization from the perspective of cancer behavioral ecology. In our model, field cancerization arises from a breakdown in signaling integrity and control, and investigate implications for acute wounding, chronic wounding, aging, and therapeutic interventions. We find that restoration of communication networks can lead to cancer regression in the context of acute injury. Conversely, long term loss of controls, such as through chronic wounding or aging, can promote oncogenesis. These results are paralleled in therapeutic interventions: those that simply target cells in cancerous states may be less effective than those that reestablish signaling integrity. Viewing cancer as a corruption of communication systems rather than as a corruption of individual cells may lead to novel approaches for understanding and treating this disease.

Endocrine disrupting chemicals and breast cancer cells

Many hundreds of endocrine disrupting chemicals (EDCs) have been measured as entering human breast tissue from a range of environmental sources, and this review focuses on discussion of mechanisms by which such EDCs may be contributing to the globally rising incidence of breast cancer. Many of the distinguishing features of breast cancer may be accounted for by EDC exposure, including, but not limited to, the fact that many EDCs possess estrogenic activity and exposure to estrogen is a main risk factor for breast cancer. Studies of the actions of EDCs in human breast cancer cells are aided by use of the conceptual framework of the hallmarks of cancer, and, acting by a variety of genomic and nongenomic mechanisms, EDCs have now been shown to enable all the hallmarks of cancer to develop in human breast cancer cells. Many studies report that hallmarks can develop at concentrations which are within the range of those measured in human breast tissues, especially when added as mixtures. The varied levels of different EDCs measured in individual breast tissue samples together with the overlapping and complementary mechanisms of action of the EDCs imply that thematic mechanisms will be driven inevitably by different chemical mixtures. Despite the complexity, EDCs do need to now be acknowledged as a risk factor for breast cancer in order for preventative strategies to include reduction in EDC exposure.

Metabolomics of primary cutaneous melanoma and matched adjacent extratumoral microenvironment

BACKGROUND

Melanoma causes the vast majority of deaths attributable to skin cancer, largely due to its propensity for metastasis. To date, few studies have examined molecular changes between primary cutaneous melanoma and adjacent putatively normal skin. To broaden temporal inferences related to initiation of disease, we performed a metabolomics investigation of primary melanoma and matched extratumoral microenvironment (EM) tissues; and, to make inferences about progressive disease, we also compared unmatched metastatic melanoma tissues to EM tissues.

METHODS

Ultra-high performance liquid chromatography-mass spectrometry-based metabolic profiling was performed on frozen human tissues.

RESULTS

We observed 824 metabolites as differentially abundant among 33 matched tissue samples, and 1,118 metabolites as differentially abundant between metastatic melanoma (n = 46) and EM (n = 34) after false discovery rate (FDR) adjustment (p<0.01). No significant differences in metabolite abundances were noted comparing primary and metastatic melanoma tissues.

CONCLUSIONS

Overall, pathway-based results significantly distinguished melanoma tissues from EM in the metabolism of: ascorbate and aldarate, propanoate, tryptophan, histidine, and pyrimidine. Within pathways, the majority of individual metabolite abundances observed in comparisons of primary melanoma vs. EM and metastatic melanoma vs. EM were directionally consistent. This observed concordance suggests most identified compounds are implicated in the initiation or maintenance of melanoma.

Association between body mass index and localization of breast cancer: results from a nationwide inpatient database in Japan

PURPOSE

Although both localization of breast cancer and body mass index (BMI) are associated with prognosis, the association between localization of breast cancer and BMI remains unclear. This study aimed to investigate the association between localization of breast cancer and BMI at diagnosis.

METHODS

Patients who underwent surgery for stage 0-III breast cancer July 2010-March 2017 were identified retrospectively in a Japanese nationwide inpatient database. Multinomial logistic regression analyses adjusting for patient's age were conducted to compare the outcomes among five BMI groups: < 18.5 kg/m² (n = 31,724; 9.3%), 18.5-24.9 kg/m² (n = 218,244; 64.3%), 25.0-29.9 kg/m² (n = 69,813; 20.6%), 30.0-34.9 kg/m² (n = 16,052; 4.7%), and ≥ 35.0 kg/m² (n = 3716; 1.1%). The outcomes were the quadrant and side of the breast where tumors were detected.

RESULTS

In total, about half of the patients had breast cancer in the upper-outer quadrant (49.7%) and in the left breast (51.1%). In the multinomial analysis, BMI ≥ 25.0 kg/m² was associated with the occurrence of breast cancer in the upper-inner and lower-outer quadrants and in the central area, whereas BMI < 18.5 kg/m² was associated with the occurrence of breast cancer in the central area only. The side of breast cancer did not differ significantly among the five BMI groups.

CONCLUSIONS

Localization of breast cancer was associated with BMI in this large nationwide cohort. The findings may benefit patients' self-checks and doctors' examinations, potentially resulting in early detection and treatment.

Exploring Association of Breast Pain, Pregnancy, and Body Mass Index with Breast Tissue Elasticity in Healthy Women: Glandular and Fat Differences

Breast sonoelastography is a relatively novel ultrasound (US) method that enables estimation of tissue stiffness to estimate the elasticity of normal breast tissue and seek to correlate it with well-known breast cancer risk factors. Two hundred women of different age were included in the study and completed a questionnaire about personal, familiar, and reproductive history. Glandular and fatty tissue elasticity in all breast quadrants was measured by shear wave elastography (SWE). Mean elastographic values of breast tissue were calculated and compared to personal history risk factors. Elasticity of normal glandular tissue (66.4 kilopascals (kPa)) was higher than fatty tissue (26.1 kPa) in all breast quadrants and in both breasts. Lower outer quadrant (LOQ) had the lowest elasticity values of both parenchyma and fat. Higher elasticity values of breast tissue were confirmed in the left breast than in the right breast. Glandular and fat tissue elasticity negatively correlated with body mass index (BMI). Women with mastodynia had higher glandular elastographic values compared to subjects without breast pain. Nuliparity was also associated with higher elasticity of glandular breast tissue. The results of this study are promising and could, over time, contribute to a better understanding of glandular breast tissue elasticity as a potential risk factor for breast cancer.

Breast cancer in women: a descriptive analysis of the national cancer database

Background and aim of the work:

Breast cancer is the most common cancer in women in the United States. National Cancer Database (NCDB) is one of the largest tumor databases of the United States. This study aimed to evaluate the features of breast cancer in women from a large updated database.

Methods:

We describe and analyze the frequencies and percentages of the clinical and pathological features of women diagnosed with breast cancer registered in NCDB, in a period from 2004 to 2015.

Results:

A total of 2,423,875 women were diagnosed with breast cancer between 2004 and 2015. The nationally representative analysis demonstrated that the incidence of breast cancer among women increased over the years. Upper-outer quadrant was the most frequent primary tumor site, and the intraductal carcinoma was the most frequent histology. The prevalence of breast cancer increased with age. The most frequent grade at diagnosis was grade II. Broadly, invasive characteristics were noted more frequently in younger patients. Left and right breast were affected with almost the same frequency, with a slight predominance of the left breast. The most frequent surgical treatment was a partial mastectomy. Reconstruction with implant was the most frequent choice. Post-mastectomy radiation therapy was administered in the majority of patients.

Conclusions:

To the authors’ knowledge, the current study is the largest descriptive analysis to date on the clinical and pathological features of breast cancer in a population-based database. The increase in incidence over the years indicates an important need for etiologic research and innovative approaches to improve breast cancer prevention. (www.actabiomedica.it)

High MYC Levels Favour Multifocal Carcinogenesis

The term "field cancerisation" describes the formation of tissue sub-areas highly susceptible to multifocal tumourigenesis. In the earlier stages of cancer, cells may indeed display a series of molecular alterations that allow them to proliferate faster, eventually occupying discrete tissue regions with irrelevant morphological anomalies. This behaviour recalls cell competition, a process based on a reciprocal fitness comparison: when cells with a growth advantage arise in a tissue, they are able to commit wild-type neighbours to death and to proliferate at their expense. It is known that cells expressing high MYC levels behave as super-competitors, able to kill and replace less performant adjacent cells; given MYC upregulation in most human cancers, MYC-mediated cell competition is likely to pioneer field cancerisation. Here we show that MYC overexpression in a sub-territory of the larval wing epithelium of Drosophila is sufficient to trigger a number of cellular responses specific to mammalian pre-malignant tissues. Moreover, following induction of different second mutations, high MYC-expressing epithelia were found to be susceptible to multifocal growth, a hallmark of mammalian pre-cancerous fields. In summary, our study identified an early molecular alteration implicated in field cancerisation and established a genetically amenable model which may help study the molecular basis of early carcinogenesis.

An evolutionary perspective on field cancerization

Tumorigenesis begins long before the growth of a clinically detectable lesion and, indeed, even before any of the usual morphological correlates of pre-malignancy are recognizable. Field cancerization, which is the replacement of the normal cell population by a cancer-primed cell population that may show no morphological change, is now recognized to underlie the development of many types of cancer, including the common carcinomas of the lung, colon, skin, prostate and bladder. Field cancerization is the consequence of the evolution of somatic cells in the body that results in cells that carry some but not all phenotypes required for malignancy. Here, we review the evidence of field cancerization across organs and examine the biological mechanisms that drive the evolutionary process that results in field creation. We discuss the clinical implications, principally, how measurements of the cancerized field could improve cancer risk prediction in patients with pre-malignant disease.

Mapping genomic and transcriptomic alterations spatially in epithelial cells adjacent to human breast carcinoma

Almost all genomic studies of breast cancer have focused on well-established tumours because it is technically challenging to study the earliest mutational events occurring in human breast epithelial cells. To address this we created a unique dataset of epithelial samples ductoscopically obtained from ducts leading to breast carcinomas and matched samples from ducts on the opposite side of the nipple. Here, we demonstrate that perturbations in mRNA abundance, with increasing proximity to tumour, cannot be explained by copy number aberrations. Rather, we find a possibility of field cancerization surrounding the primary tumour by constructing a classifier that evaluates where epithelial samples were obtained relative to a tumour (cross-validated micro-averaged AUC = 0.74). We implement a spectral co-clustering algorithm to define biclusters. Relating to over-represented bicluster pathways, we further validate two genes with tissue microarrays and in vitro experiments. We highlight evidence suggesting that bicluster perturbation occurs early in tumour development.

Studying the spatial mutational and gene expression alterations in breast cancer could impact our understanding of breast cancer development. Here, the authors analyse a unique dataset of epithelial samples that highlight potential field cancerisation surrounding the primary tumour.

3D MRI for Quantitative Analysis of Quadrant Percent Breast Density: Correlation with Quadrant Location of Breast Cancer

RATIONALE AND OBJECTIVES

Breast cancer occurs more frequently in the upper outer (UO) quadrant, but whether this higher cancer incidence is related to the greater amount of dense tissue is not known. Magnetic resonance imaging acquires three-dimensional volumetric images and is the most suitable among all breast imaging modalities for regional quantification of density. This study applied a magnetic resonance imaging-based method to measure quadrant percent density (QPD), and evaluated its association with the quadrant location of the developed breast cancer.

MATERIALS AND METHODS

A total of 126 cases with pathologically confirmed breast cancer were reviewed. Only women who had unilateral breast cancer located in a clear quadrant were selected for analysis. A total of 84 women, including 47 Asian women and 37 western women, were included. An established computer-aided method was used to segment the diseased breast and the contralateral normal breast, and to separate the dense and fatty tissues. Then, a breast was further separated into four quadrants using the nipple and the centroid as anatomic landmarks. The tumor was segmented using a computer-aided method to determine its quadrant location. The distribution of cancer quadrant location, the quadrant with the highest QPD, and the proportion of cancers occurring in the highest QPD were analyzed.

RESULTS

The highest incidence of cancer occurred in the UO quadrant (36 out of 84, 42.9%). The highest QPD was also noted most frequently in the UO quadrant (31 out of 84, 36.9%). When correlating the highest QPD with the quadrant location of breast cancer, only 17 women out of 84 (20.2%) had breast cancer occurring in the quadrant with the highest QPD.

CONCLUSIONS

The results showed that the development of breast cancer in a specific quadrant could not be explained by the density in that quadrant, and further studies are needed to find the biological reasons accounting for the higher breast cancer incidence in the UO quadrant.

Evaluation of the association between quantitative mammographic density and breast cancer occurred in different quadrants

BACKGROUND

To investigate the relationship between mammographic density measured in four quadrants of a breast with the location of the occurred cancer.

METHODS

One hundred and ten women diagnosed with unilateral breast cancer that could be determined in one specific breast quadrant were retrospectively studied. Women with previous cancer/breast surgery were excluded. The craniocaudal (CC) and mediolateral oblique (MLO) mammography of the contralateral normal breast were used to separate a breast into 4 quadrants: Upper-Outer (UO), Upper-Inner (UI), Lower-Outer (LO), and Lower-Inner (LI). The breast area (BA), dense area (DA), and percent density (PD) in each quadrant were measured by using the fuzzy-C-means segmentation. The BA, DA, and PD were compared between patients who had cancer occurring in different quadrants.

RESULTS

The upper-outer quadrant had the highest BA (37 ± 15 cm²) and DA (7.1 ± 2.9 cm²), with PD = 20.0 ± 5.8%. The order of BA and DA in the 4 separated quadrants were: UO > UI > LO > LI, and almost all pair-wise comparisons showed significant differences. For tumor location, 67 women (60.9%) had tumor in UO, 16 (14.5%) in UI, 7 (6.4%) in LO, and 20 (18.2%) in LI quadrant, respectively. The estimated odds and the 95% confidence limits of tumor development in the UO, UI, LO and LI quadrants were 1.56 (1.06, 2.29), 0.17 (0.10, 0.29), 0.07 (0.03, 0.15), and 0.22 (0.14, 0.36), respectively. In these 4 groups of women, the order of quadrant BA and DA were all the same (UO > UI > LO > LI), and there was no significant difference in BA, DA or PD among them (all p > 0.05).

CONCLUSIONS

Breast cancer was most likely to occur in the UO quadrant, which was also the quadrant with highest BA and DA; but for women with tumors in other quadrants, the density in that quadrant was not the highest. Therefore, there was no direct association between quadrant density and tumor occurrence.

Aluminium and the human breast

The human population is exposed to aluminium (Al) from diet, antacids and vaccine adjuvants, but frequent application of Al-based salts to the underarm as antiperspirant adds a high additional exposure directly to the local area of the human breast. Coincidentally the upper outer quadrant of the breast is where there is also a disproportionately high incidence of breast cysts and breast cancer. Al has been measured in human breast tissues/fluids at higher levels than in blood, and experimental evidence suggests that at physiologically relevant concentrations, Al can adversely impact on human breast epithelial cell biology. Gross cystic breast disease is the most common benign disorder of the breast and evidence is presented that Al may be a causative factor in formation of breast cysts. Evidence is also reviewed that Al can enable the development of multiple hallmarks associated with cancer in breast cells, in particular that it can cause genomic instability and inappropriate proliferation in human breast epithelial cells, and can increase migration and invasion of human breast cancer cells. In addition, Al is a metalloestrogen and oestrogen is a risk factor for breast cancer known to influence multiple hallmarks. The microenvironment is established as another determinant of breast cancer development and Al has been shown to cause adverse alterations to the breast microenvironment. If current usage patterns of Al-based antiperspirant salts contribute to causation of breast cysts and breast cancer, then reduction in exposure would offer a strategy for prevention, and regulatory review is now justified.

Tissue aluminum concentration does not affect the genomic stability of ERBB2, C-MYC, and CCND1 genes in breast cancer

It has long been hypothesized that body tissue uptake of aluminum may have biological implications in breast cancer. In vitro and in vivo studies have shown that aluminum may trigger genomic instability by interfering with DNA strands. The objective of this study was to examine the relationship between aluminum concentrations in the peripheral and central areas of breast tumors with the instability of three key genes in breast cancer, ERBB2, C-MYC, and CCND1 and aneuploidy of the chromosomes harboring these genes. Tissue samples of 118 women treated for breast cancer were obtained. Evaluation of aluminum content was carried out using graphite furnace atomic absorption spectrometry. A tissue microarray slide containing the tumor samples was used in FISH assays to assess ERBB2, C-MYC, and CCND1 expressions as well as the statuses of their respective chromosomes 17, 8, and 11. Clinicopathological data were obtained from patient's records. Aluminum levels of >2.0 mg/kg were found in 20.3 and 22.1% of the central and peripheral breast tumor areas, respectively. Amplification and/or aneuploid-positive statuses for ERBB2/CEP17, C-MYC/CEP8, and CCND1/CEP11 were detected in 24, 36.7, and 29.3% of the tumors, respectively. We found that aluminum concentration was not related to these altered gene statuses. Our findings suggest that aluminum concentration does not affect genomic stability in breast tissues. Tissue microenvironment modifications, due to the presence of aluminum compounds, seem more appealing as a possible target for future studies to determine the implications of aluminum in breast carcinogenesis.

Aluminum concentrations in central and peripheral areas of malignant breast lesions do not differ from those in normal breast tissues

Background

Aluminum is used in a wide range of applications and is a potential environmental hazard. The known genotoxic effects of aluminum might play a role in the development of breast cancer. However, the data currently available on the subject are not sufficient to establish a causal relationship between aluminum exposure and the augmented risk of developing breast cancer. To achieve maximum sensitivity and specificity in the determination of aluminum levels, we have developed a detection protocol using graphite furnace atomic absorption spectrometry (GFAAS). The objective of the present study was to compare the aluminum levels in the central and peripheral areas of breast carcinomas with those in the adjacent normal breast tissues, and to identify patient and/or tumor characteristics associated with these aluminum levels.

Methods

A total of 176 patients with breast cancer were included in the study. Samples from the central and peripheral areas of their tumors were obtained, as well as from the surrounding normal breast tissue. Aluminum quantification was performed using GFAAS.

Results

The average (mean ± SD) aluminum concentrations were as follows: central area, 1.88 ± 3.60 mg/kg; peripheral area, 2.10 ± 5.67 mg/kg; and normal area, 1.68 ± 11.1 mg/kg. Overall and two-by-two comparisons of the aluminum concentrations in these areas indicated no significant differences. We detected a positive relationship between aluminum levels in the peripheral areas of the tumors, age and menopausal status of the patients (P = .02).

Conclusions

Using a sensitive quantification technique we detected similar aluminum concentrations in the central and peripheral regions of breast tumors, and in normal tissues. In addition, we did not detect significant differences in aluminum concentrations as related to the location of the breast tumor within the breast, or to other relevant tumor features such as stage, size and steroid receptor status. The next logical step is the assessment of whether the aluminum concentration is related to the key genomic abnormalities associated with breast carcinogenesis.

Genomic (in)stability of the breast tumor microenvironment

The breast tumor microenvironment plays an active role in tumorigenesis. Molecular alterations have been identified in tumor-associated stroma; however, there is considerable debate as to whether the stroma is characterized by genomic instability or whether detection of chromosomal alterations reflects technological artifact rather than the true genomic content of the tumor microenvironment. Thus, breast stroma specimens from 112 women undergoing reductive mammoplasty (n = 7), prophylactic mastectomy (n = 6), or mastectomy for a breast disease (n = 99) were frozen in optimal cutting temperature medium. Allelic imbalance (AI) analysis was conducted using a panel of 52 microsatellite markers in 484 stromal specimens from 98 women, of which 92% had no detectable AI events. When compared with previously generated AI data from 77 formalin-fixed, paraffin-embedded (FFPE) stroma specimens, 42% of which harbored at least one detectable AI event, the frequency of AI in the FFPE specimens (4.62%) was significantly higher (P < 0.001) than that found in frozen specimens (0.45%). This comparison of AI between FFPE and research-grade specimens suggests that past reports of AI in breast stroma reflect artifact in the archival specimens caused by formalin-fixation, paraffin-embedding and tissue storage. Furthermore, SNP data were generated from a subset of 86 stromal specimens using SNP arrays and copy number alterations were identified using Partek Genomics Suite. For 95% of the specimens, no detectable copy number alterations were found and the 11 changes that were detected were small and not shared between specimens. These data, therefore, support a model in which the tumor microenvironment is genetically stable.

Influence of sex hormones in women on breast elasticity measured by shear wave sonoelastography--a cross-sectional study

The physiology of breast depends on age, hormonal status, menstrual cycle, lactation, and others. The aim of our study was to evaluate correlations between hormonal status and breast glandular and fat tissue elasticity in healthy women. We examined 77 women aged 20-55 with shear wave sonoelastography and estimated their hormonal levels. There were no important correlations between breast elasticity, follicle-stimulating hormone (FSH), estrogen, prolactine, and thyroid hormones (p > 0.05). Androgens negatively influenced glandular to fat elasticity ratio (Rs = -0.25, p < 0.005). Luteinizing hormone to FSH ratio correlated positively with glandular and fat elasticity, especially in outer-upper quadrant (Rs = 0.24, p = 0.003).

Factors influencing breast elasticity measured by the ultrasound Shear Wave elastography - preliminary results

INTRODUCTION

Many physiological changes of breast elasticity depend on the age, hormonal status, menstrual cycle and many others. The aim of this study was to evaluate viscoelastic properties of normal breast tissues in a large group of women and to search for factors which play a role in its mechanical properties.

MATERIAL AND METHODS

101 women aged 18-74 years who underwent B-mode sonography and additionally sonoelastography. We measured viscoelasticity in 8 quadrants by a share wave ultrasonic device estimating Young modules in regions of interest.

RESULTS

Mean elasticity measured in all 8 scans in glandular and fatty tissue were 11.28 ±5.79 kPa (0.1-46.26 kPa) and 9.24 ±4.48 kPa (0.1-29.78 kPa), respectively. The correlation between age and mean elasticity of glandular tissue was Rs = 0.27 (p = 0.007). The correlation between glandular tissue elasticity heterogeneity and breast mastalgia measured by VAS was Rs = -0.23 (p = 0.241). Fat tissue elasticity correlated with duration of lactation was Rs = 0.21 (p = 0.01).

CONCLUSIONS

There are several parameters influencing breast viscoelasticity measured by share wave sonoelastography. Glandular tissue elasticity correlates positively with age, fatty tissue elasticity correlates positively with duration of lactation and heterogeneity of the elasticity map of glandular tissue correlates with breast pain and fat tissue with BMI.

Quantitative methylation profiling in tumor and matched morphologically normal tissues from breast cancer patients

Background

In the present study, we determined the gene hypermethylation profiles of normal tissues adjacent to invasive breast carcinomas and investigated whether these are associated with the gene hypermethylation profiles of the corresponding primary breast tumors.

Methods

A quantitative methylation-specific PCR assay was used to analyze the DNA methylation status of 6 genes (DAPK, TWIST, HIN-1, RASSF1A, RARβ2 and APC) in 9 normal breast tissue samples from unaffected women and in 56 paired cancerous and normal tissue samples from breast cancer patients.

Results

Normal tissue adjacent to breast cancer displayed statistically significant differences to unrelated normal breast tissues regarding the aberrant methylation of the RASSF1A (P = 0.03), RARβ2 (P = 0.04) and APC (P = 0.04) genes. Although methylation ratios for all genes in normal tissues from cancer patients were significantly lower than in the cancerous tissue from the same patient (P ≤ 0.01), in general, a clear correlation was observed between methylation ratios measured in both tissue types for all genes tested (P < 0.01). When analyzed as a categorical variable, there was a significant concordance between methylation changes in normal tissues and in the corresponding tumor for all genes tested but RASSF1A. Notably, in 73% of patients, at least one gene with an identical methylation change in cancerous and normal breast tissues was observed.

Conclusions

Histologically normal breast tissues adjacent to breast tumors frequently exhibit methylation changes in multiple genes. These methylation changes may play a role in the earliest stages of the development of breast neoplasia.

Proliferative genes dominate malignancy-risk gene signature in histologically-normal breast tissue

Historical data have indicated the potential for the histologically-normal breast to harbor pre-malignant changes at the molecular level. We postulated that a histologically-normal tissue with "tumor-like" gene expression pattern might harbor substantial risk for future cancer development. Genes associated with these high-risk tissues were considered to be "malignancy-risk genes". From a total of 90 breast cancer patients, we collected a set of 143 histologically-normal breast tissues derived from patients harboring breast cancer who underwent curative mastectomy, as well as a set of 42 invasive ductal carcinomas (IDC) of various histologic grades. All samples were assessed for global gene expression differences using microarray analysis. For the purpose of this study we defined normal breast tissue to include histologically normal and benign lesions. Here we report the discovery of a "malignancy-risk" gene signature that may portend risk of breast cancer development in benign, but molecularly-abnormal, breast tissue. Pathway analysis showed that the malignancy-risk signature had a dramatic enrichment for genes with proliferative function, but appears to be independent of ER, PR, and HER2 status. The signature was validated by RT-PCR, with a high correlation (Pearson correlation = 0.95 with P < 0.0001) with microarray data. These results suggest a predictive role for the malignancy-risk signature in normal breast tissue. Proliferative biology dominates the earliest stages of tumor development.

Mammary field cancerization: molecular evidence and clinical importance

The term "field cancerization" originally denoted the presence of histologically abnormal tissue/cells surrounding primary tumors of the head and neck. Similar concepts with different and continuously changing definitions have been used for other types of tumors including breast adenocarcinoma, where field cancerization presently denotes the occurrence of molecular alterations in histologically normal tissues surrounding areas of overt cancer. Human mammary tissue morphology lends itself to the proposed concepts of field cancerization, which may include the gradual accumulation of genetic and other aberrations in stationary epithelial cells with intact morphology, or the spread of histologically normal yet genetically aberrant epithelial cells within mammary tissue. In this report, we review published molecular genetic, epigenetic, and gene expressional data in support of field cancerization in human mammary tissues. We then discuss the clinical implications of mammary field cancerization, including its source for potential biomarkers with diagnostic/prognostic potential, and its relationship to surgical margins and disease recurrence. We conclude with a future outlook on further research on mammary field cancerization addressing experimental methods, as well as the development of possible models and integrated approaches to gain a better understanding of the underlying mechanisms with the ultimate goal of developing clinical applications.

Correlation of Levels and Patterns of Genomic Instability With Histological Grading of DCIS

BACKGROUND

Histological grading of ductal carcinoma-in-situ (DCIS) lesions separates DCIS into three subgroups (well-, moderately, or poorly differentiated). It is unclear, however, whether breast disease progresses along a histological continuum or whether each grade represents a separate disease. In this study, levels and patterns of allelic imbalance (AI) were examined in DCIS lesions to develop molecular models that can distinguish pathological classifications of DCIS.

METHODS

Laser microdissected DNA samples were collected from DCIS lesions characterized by a single pathologist including well- (n = 18), moderately (n = 35), and poorly differentiated (n = 47) lesions. A panel of 52 microsatellite markers representing 26 chromosomal regions commonly altered in breast cancer was used to assess patterns of AI.

RESULTS

The overall frequency of AI increased significantly (P < .001) with increasing grade (well differentiated, 12%; moderately differentiated, 17%; poorly differentiated, 26%). Levels of AI were not significantly different between well- and moderately differentiated grades of disease but were significantly higher (P < .0001) in poorly differentiated compared with well- or moderately differentiated disease. No statistically significant differences in patterns of AI were detected between well- and moderately differentiated disease; however, AI occurred significantly more frequently (P < .05) in high-grade lesions at chromosomes 6q25-q27, 8q24, 9p21, 13q14, and 17p13.1, and significantly more frequently in low-grade lesions at chromosome 16q22.3-q24.3.

CONCLUSIONS

The inability to discriminate DCIS at the genetic level suggests that grades 1 and 2 DCIS may represent a single, non-high-grade form of DCIS, whereas poorly differentiated DCIS seems to be a genetically more advanced disease that may represent a discrete disease entity, characterized by a unique spectrum of genetic alterations.

Assessment of the frequency of allelic imbalance in human tissue using a multiplex polymerase chain reaction system

Genomic instability can generate chromosome breakage and fusion randomly throughout the genome, frequently resulting in allelic imbalance, a deviation from the normal 1:1 ratio of maternal and paternal alleles. Allelic imbalance reflects the karyotypic complexity of the cancer genome. Therefore, it is reasonable to speculate that tissues with more sites of allelic imbalance have a greater likelihood of having disruption of any of the numerous critical genes that cause a cancerous phenotype and thus may have diagnostic or prognostic significance. For this reason, it is desirable to develop a robust method to assess the frequency of allelic imbalance in any tissue. To address this need, we designed an economical and high-throughput method, based on the Applied Biosystems AmpFlSTR Identifiler multiplex polymerase chain reaction system, to evaluate allelic imbalance at 16 unlinked, microsatellite loci located throughout the genome. This method provides a quantitative comparison of the extent of allelic imbalance between samples that can be applied to a variety of frozen and archival tissues. The method does not require matched normal tissue, requires little DNA (the equivalent of approximately 150 cells) and uses commercially available reagents, instrumentation, and analysis software. Greater than 99% of tissue specimens with >or=2 unbalanced loci were cancerous.

Clinical implications and utility of field cancerization

Cancer begins with multiple cumulative epigenetic and genetic alterations that sequencially transform a cell, or a group of cells in a particular organ. The early genetic events might lead to clonal expansion of pre-neoplastic daughter cells in a particular tumor field. Subsequent genomic changes in some of these cells drive them towards the malignant phenotype. These transformed cells are diagnosed histopathologically as cancers owing to changes in cell morphology. Conceivably, a population of daughter cells with early genetic changes (without histopathology) remain in the organ, demonstrating the concept of field cancerization. With present technological advancement, including laser capture microdisection and high-throughput genomic technologies, carefully designed studies using appropriate control tissue will enable identification of important molecular signatures in these genetically transformed but histologically normal cells. Such tumor-specific biomarkers should have excellent clinical utility. This review examines the concept of field cancerization in several cancers and its possible utility in four areas of oncology; risk assessment, early cancer detection, monitoring of tumor progression and definition of tumor margins.

Mapping geographic zones of cancer risk with epigenetic biomarkers in normal breast tissue

PURPOSE

Genetic alterations were previously identified in normal epithelia adjacent to invasive cancers. The aim of this study was to determine DNA methylation in histologically normal tissues from multiple geographic zones adjacent to primary breast tumors.

EXPERIMENTAL DESIGN

First, methylation status of a 4-kb region of RASSF1A promoter was interrogated using oligonucleotide-based microarray in 144 samples (primary tumors, 47; adjacent normals, 69; reduction mammoplasty tissues, 28). Second, allelic imbalance (AI)/loss of heterozygosity (LOH) surrounding RASSF1A promoter were analyzed in 30 samples (tumors, 8; adjacent normals, 22). Third, global methylation screening of 49 samples (tumors, 12; adjacent normals, 25; reduction mammoplasty, 12) was done by differential methylation hybridization. Real-time quantitative methylation-specific PCR was used to validate the microarray findings.

RESULTS

DNA methylation in the core RASSF1A promoter was low in reduction mammoplasty tissues (P=0.0001) when compared with primary tumors. The adjacent normals had an intermediate level of methylation. The regions surrounding the core were highly methylated in all sample types. Microsatellite markers showed AI/LOH in tumors and some of the adjacent normals. Concurrent AI/LOH and DNA methylation in RASSF1A promoter occurred in two of six tumors. Global methylation screening uncovered genes more methylated in adjacent normals than in reduction mammoplasty tissues. The methylation status of four genes was confirmed by quantitative methylation-specific PCR.

CONCLUSIONS

Our findings suggest a field of methylation changes extending as far as 4 cm from primary tumors. These frequent alterations may explain why normal tissues are at risk for local recurrence and are useful in disease prognostication.

Mapping loss of heterozygosity in normal human breast cells from BRCA1/2 carriers

We have studied loss of heterozygosity at the BRCA1 and BRCA2 loci in 992 normal cell clones derived from topographically defined areas of normal tissue in four samples from BRCA1/BRCA2 mutation carriers. The frequency of loss of heterozygosity in the clones was low (1.01%), but it was found in all four samples, whether or not a tumour was present. Topographical mapping revealed that the genetic changes were clustered in some breast samples. Our study confirms the previous finding that a field of genetic instability can exist around a tumour, suggesting that sufficient tissue must be removed at surgery to avoid local recurrence. We also demonstrate that such a field of genetic change can exist in morphologically normal tissue before a tumour develops and, for the first time, we demonstrate that the field is of a size greater than one terminal duct-lobular unit. The genetic changes are not identical, however, which suggests that genetic instability in these regions may play an early role in tumour development. We also confirm and extend our original observation of loss of the wild-type BRCA1 allele in some clones, and loss of the mutant allele in others, demonstrating that loss of either allele is a stochastic event.

Alteration of proliferation and apoptotic markers in normal and premalignant tissue associated with prostate cancer

Background

Molecular markers identifying alterations in proliferation and apoptotic pathways could be particularly important in characterizing high-risk normal or pre-neoplastic tissue. We evaluated the following markers: Ki67, Minichromosome Maintenance Protein-2 (Mcm-2), activated caspase-3 (a-casp3) and Bcl-2 to determine if they showed differential expression across progressive degrees of intraepithelial neoplasia and cancer in the prostate. To identify field effects, we also evaluated whether high-risk expression patterns in normal tissue were more common in prostates containing cancer compared to those without cancer (supernormal), and in histologically normal glands adjacent to a cancer focus as opposed to equivalent glands that were more distant.

Methods

The aforementioned markers were studied in 13 radical prostatectomy (RP) and 6 cystoprostatectomy (CP) specimens. Tissue compartments representing normal, low grade prostatic intraepithelial neoplasia (LGPIN), high grade prostatic intraepithelial neoplasia (HGPIN), as well as different grades of cancer were mapped on H&E slides and adjacent sections were analyzed using immunohistochemistry. Normal glands within 1 mm distance of a tumor focus and glands beyond 5 mm were considered "near" and "far", respectively. Randomly selected nuclei and 40 × fields were scored by a single observer; basal and luminal epithelial layers were scored separately.

Results

Both Ki-67 and Mcm-2 showed an upward trend from normal tissue through HGPIN and cancer with a shift in proliferation from basal to luminal compartment. Activated caspase-3 showed a significant decrease in HGPIN and cancer compartments. Supernormal glands had significantly lower proliferation indices and higher a-casp3 expression compared to normal glands. "Near" normal glands had higher Mcm-2 indices compared to "far" glands; however, they also had higher a-casp3 expression. Bcl-2, which varied minimally in normal tissue, did not show any trend across compartments or evidence for field effects.

Conclusion

These results demonstrate that proliferation and apoptosis are altered not only in preneoplastic lesions but also in apparently normal looking epithelium associated with cancer. Luminal cell expression of Mcm-2 appears to be particularly promising as a marker of high-risk normal epithelium. The role of apoptotic markers such as activated caspase-3 is more complex, and might depend on the proliferation status of the tissue in question.

Environmental oestrogens, cosmetics and breast cancer

The established role of oestrogen in the development and progression of breast cancer raises questions concerning a potential contribution from the many chemicals in the environment which can enter the human breast and which have oestrogenic activity. A range of organochlorine pesticides and polychlorinated biphenyls possess oestrogen-mimicking properties and have been measured in human breast adipose tissue and in human milk. These enter the breast from varied environmental contamination of food, water and air, and due to their lipophilic properties can accumulate in breast fat. However, it is emerging that the breast is also exposed to a range of oestrogenic chemicals applied as cosmetics to the underarm and breast area. These cosmetics are left on the skin in the appropriate area, allowing a more direct dermal absorption route for breast exposure to oestrogenic chemicals and allowing absorbed chemicals to escape systemic metabolism. This review considers evidence in support of a functional role for the combined interactions of cosmetic chemicals with environmental oestrogens, pharmacological oestrogens, phyto-oestrogens and physiological oestrogens in the rising incidence of breast cancer.

Regulation of endocrine-disrupting chemicals: critical overview and deficiencies in toxicology and risk assessment for human health

Regulation of endocrine-disrupting chemicals is reviewed in terms of hazard assessment (regulatory toxicology) and risk assessment. The current range of regulatory general toxicology protocols can detect endocrine toxicity, but specific endocrine toxicology tests are required to confirm mechanisms (e.g. oestrogenic, anti-androgenic). Strategies for validating new endocrine toxicology protocols and approaches to data assessment are discussed, and deficiencies in regulatory toxicology testing (e.g. lack of adrenocortical function assessment) identified. Recent evidence of a role of prolactin in human breast cancer also highlights deficiencies in regulatory evaluation. Actual human exposure to chemicals and the high-exposure example of chemicals in body-care cosmetics is reviewed with reference to evidence that common ingredients (e.g. parabens, cyclosiloxanes) are oestrogenic. The hypothesis and epidemiology concerning chemical exposure from body-care cosmetics (moisturizers, lotions, sun screens, deodorants) and breast cancer in women is reviewed, applying Bradford-Hill criteria for association and causality, and research requirements are identified.

Aluminium, antiperspirants and breast cancer

Aluminium salts are used as the active antiperspirant agent in underarm cosmetics, but the effects of widespread, long term and increasing use remain unknown, especially in relation to the breast, which is a local area of application. Clinical studies showing a disproportionately high incidence of breast cancer in the upper outer quadrant of the breast together with reports of genomic instability in outer quadrants of the breast provide supporting evidence for a role for locally applied cosmetic chemicals in the development of breast cancer. Aluminium is known to have a genotoxic profile, capable of causing both DNA alterations and epigenetic effects, and this would be consistent with a potential role in breast cancer if such effects occurred in breast cells. Oestrogen is a well established influence in breast cancer and its action, dependent on intracellular receptors which function as ligand-activated zinc finger transcription factors, suggests one possible point of interference from aluminium. Results reported here demonstrate that aluminium in the form of aluminium chloride or aluminium chlorhydrate can interfere with the function of oestrogen receptors of MCF7 human breast cancer cells both in terms of ligand binding and in terms of oestrogen-regulated reporter gene expression. This adds aluminium to the increasing list of metals capable of interfering with oestrogen action and termed metalloestrogens. Further studies are now needed to identify the molecular basis of this action, the longer term effects of aluminium exposure and whether aluminium can cause aberrations to other signalling pathways in breast cells. Given the wide exposure of the human population to antiperspirants, it will be important to establish dermal absorption in the local area of the breast and whether long term low level absorption could play a role in the increasing incidence of breast cancer.

Timing of Critical Genetic Changes in Human Breast Disease

BACKGROUND

Breast cancer development has been characterized as a nonobligatory sequence of histological changes from normal epithelium through invasive malignancy. Although genetic alterations are thought to accumulate stochastically during tumorigenesis, little is known about the timing of critical mutations. This study examined allelic imbalance (AI) in tissue samples representing a continuum of breast cancer development to examine the evolution of genomic instability.

METHODS

Laser-microdissected DNA samples were collected from histologically normal breast specimens (n = 25), atypical ductal hyperplasia (ADH, n = 16), ductal carcinoma-in-situ (DCIS, n = 37), and stage I to III invasive carcinomas (n = 72). Fifty-two microsatellite markers representing 26 chromosomal regions commonly deleted in breast cancer were used to assess patterns of AI.

RESULTS

AI frequencies were <5% in histologically normal and ADH specimens, 20% in DCIS lesions, and approximately 25% in invasive tumors. Mann-Whitney tests showed (1) that levels of AI in ADH samples did not differ significantly from those in histologically normal tissues and (2) that AI frequencies in DCIS lesions were not significantly different from those in invasive carcinomas. ADH and DCIS samples, however, differed significantly (P < .0001).

CONCLUSIONS

DCIS lesions contain levels of genomic instability that are characteristic of advanced invasive tumors, and this suggests that the biology of a developing carcinoma may already be predetermined by the in situ stage. Observations that levels of AI in ADH lesions are similar to those in disease-free tissues provide a genomic rationale for why prevention strategies at the ADH level are successful and why cases with ADH involving surgical margins do not require further resection.

Genomic patterns of allelic imbalance in disease free tissue adjacent to primary breast carcinomas

Mammary stroma plays an important role in facilitating the neoplastic transformation of epithelial cells, modulating integrity of the extracellular matrix, and maintaining genomic stability, but molecular mechanisms by which stroma affects epithelial structure and function are not well-defined. We used laser-assisted microdissection of paraffin-embedded breast tissues from 30 patients with breast disease and a panel of 52 microsatellite markers defining 26 chromosomal regions to characterize genomic patterns of allelic imbalance (AI) in disease-free tissue adjacent to sites of breast disease and to define genomic regions that may contain genes associated with early carcinogenic processes. The mean frequency of AI in histologically normal tissue adjacent to the primary carcinomas (15.4%) was significantly higher than that in distant tissue from the same breast (3.7%). The pattern of AI across all chromosomal regions differed between the adjacent tissue and primary tumor in every case. Unique AI events, observed only in tumor (15% of informative markers) or only in adjacent cells (10% of informative markers), were far more common than AI events shared between tumor and adjacent cells (approximately 4%). Levels of AI characteristic of advanced invasive carcinomas were already present in non-invasive ductal carcinomas in situ, and appreciable levels of AI were observed in adjacent non-neoplastic tissue at all pathological stages. Chromosome 11p15.1 showed significantly higher levels of AI in adjacent cells (p < 0.01), suggesting that this region may harbor genes involved in breast cancer development and progression. Our data indicate that genomic instability may be inherently greater in disease-free tissue close to developing tumors, which may have important implications for defining surgical margins and predicting recurrence.

Genomic instability in histologically normal breast tissues: implications for carcinogenesis

Breast cancer is an important contributor to morbidity and mortality in society, but factors that affect the cause of the disease are poorly defined. Genomic instability drives tumorigenic processes in invasive carcinomas and premalignant breast lesions, and might promote the accumulation of genetic alterations in apparently normal tissues before histological abnormalities are detectable. Evidence suggests that genomic changes in breast parenchyma affect the behaviour of epithelial cells, and ultimately might affect tumour growth and progression. Inherent instability in genes that maintain genomic integrity, as well as exogenous chemicals and environmental pollutants, have been implicated in breast-cancer development. Although molecular mechanisms of tumorigenesis are unclear at present, carcinogenic agents could contribute to fields of genomic instability localised to specific areas of the breast. Understanding the functional importance of genomic instability in early carcinogenesis has important implications for improvement of diagnostic and treatment strategies.