Loss of heterozygosity in benign breast epithelium in relation to breast cancer risk

Somatic Mutations in KEAP1-NRF2 Complex in Breast Cancer

Breast cancer remains the leading cause of cancer deaths for women. Long-term estrogen exposure is considered carcinogenic due to semiquinone production and to compromised detoxification. Metabolic regulator polymorphisms, such as KEAP1 (rs1048290) and NRF2 (rs35652124, rs6721961, rs6706649), can be valuable in understanding the individual cytoprotection profile. Thus, we aim to genotype these polymorphisms in blood, tumours and surrounding tissue, to identify somatic mutations and correlate it to prognoses. A total of 23 controls and 69 women with histological confirmed breast cancer were recruited, and DNA from blood/surrounding/tumour tissue was genotyped. Genotyping and clinicopathological data were correlated. We verified that rs35652124 presents different genotype distribution between the blood/surrounding tissue (p-value = 0.023) and tumour/surrounding tissues (p-value = 0.041). Apart from rs35652124 and considering the histological grade, the other four polymorphisms have different distributions among different tissues. There is a tendency towards the loss of heterozygosity in the surrounding tissue when compared to blood and tumour tissues, and higher genotype variability in histologic grade 2. These somatic mutations and different distribution patterns may indicate a heterogeneous and active microenvironment, influencing breast cancer outcome. Additionally, it would be pertinent to evaluate the predictive value of the histologic grade 2 considering somatic mutation profiles and distributions.

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.

Field cancerization in breast cancer

Breast cancer affects one in seven women worldwide during their lifetime. Widespread mammographic screening programs and education campaigns allow for early detection of the disease, often during its asymptomatic phase. Current practice in treatment and recurrence monitoring is based primarily on pathological evaluations but can also encompass genomic evaluations, both of which focus on the primary tumor. Although breast cancer is one of the most studied cancers, patients still recur at a rate of up to 15% within the first 10 years post‐surgery. Local recurrence was originally attributed to tumor cells contaminating histologically normal (HN) tissues beyond the surgical margin, but advances in technology have allowed for the identification of distinct aberrations that exist in the peri‐tumoral tissues themselves. One leading theory to explain this phenomenon is the field cancerization theory. Under this hypothesis, tumors arise from a field of molecularly altered cells that create a permissive environment for malignant evolution, which can occur with or without morphological changes. The traditional histopathology paradigm dictates that molecular alterations are reflected in the tissue phenotype. However, the spectrum of inter‐patient variability of normal breast tissue may obfuscate recognition of a cancerized field during routine diagnostics. In this review, we explore the concept of field cancerization focusing on HN peri‐tumoral tissues: we present the pathological and molecular features of field cancerization within these tissues and discuss how the use of peri‐tumoral tissues can affect research. Our observations suggest that pathological and molecular evaluations could be used synergistically to assess risk and guide the therapeutic management of patients. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Genomic Changes in Normal Breast Tissue in Women at Normal Risk or at High Risk for Breast Cancer

Sporadic breast cancer develops through the accumulation of molecular abnormalities in normal breast tissue, resulting from exposure to estrogens and other carcinogens beginning at adolescence and continuing throughout life. These molecular changes may take a variety of forms, including numerical and structural chromosomal abnormalities, epigenetic changes, and gene expression alterations. To characterize these abnormalities, a review of the literature has been conducted to define the molecular changes in each of the above major genomic categories in normal breast tissue considered to be either at normal risk or at high risk for sporadic breast cancer. This review indicates that normal risk breast tissues (such as reduction mammoplasty) contain evidence of early breast carcinogenesis including loss of heterozygosity, DNA methylation of tumor suppressor and other genes, and telomere shortening. In normal tissues at high risk for breast cancer (such as normal breast tissue adjacent to breast cancer or the contralateral breast), these changes persist, and are increased and accompanied by aneuploidy, increased genomic instability, a wide range of gene expression differences, development of large cancerized fields, and increased proliferation. These changes are consistent with early and long-standing exposure to carcinogens, especially estrogens. A model for the breast carcinogenic pathway in normal risk and high-risk breast tissues is proposed. These findings should clarify our understanding of breast carcinogenesis in normal breast tissue and promote development of improved methods for risk assessment and breast cancer prevention in women.

Histopathological Features of Non-Neoplastic Breast Parenchyma Do Not Predict BRCA Mutation Status of Patients with Invasive Breast Cancer

BACKGROUND

Several studies have evaluated histologic features of non-neoplastic breast parenchyma in patients with BRCA1/2 mutations, but the results are conflicting. The limited data suggest a much higher prevalence of high-risk precursor lesions in BRCA carriers. Therefore, we designed this study to compare the clinicopathological characteristics of peritumoral benign breast tissue in patients with and without deleterious BRCA mutations.

METHODS

Women with breast cancer (BC) who were referred for genetic counseling and underwent BRCA genetic testing in 2010 and 2011 were included in the study.

RESULTS

Of the six benign histological features analyzed in this study, only stromal fibrosis grade 2/3 was found to be statistically different, with more BRCA noncarriers having stromal fibrosis grade 2/3 than BRCA1/2 carriers (P = 0.04).

CONCLUSION

There is no significant association between mutation risk and the presence of benign histologic features of peritumoral breast parenchyma.

Concurrent DNA Copy-Number Alterations and Mutations in Genes Related to Maintenance of Genome Stability in Uninvolved Mammary Glandular Tissue from Breast Cancer Patients

Somatic mosaicism for DNA copy-number alterations (SMC-CNAs) is defined as gain or loss of chromosomal segments in somatic cells within a single organism. As cells harboring SMC-CNAs can undergo clonal expansion, it has been proposed that SMC-CNAs may contribute to the predisposition of these cells to genetic disease including cancer. Herein, the gross genomic alterations (>500 kbp) were characterized in uninvolved mammary glandular tissue from 59 breast cancer patients and matched samples of primary tumors and lymph node metastases. Array-based comparative genomic hybridization showed 10% (6/59) of patients harbored one to 359 large SMC-CNAs (mean: 1,328 kbp; median: 961 kbp) in a substantial portion of glandular tissue cells, distal from the primary tumor site. SMC-CNAs were partially recurrent in tumors, albeit with considerable contribution of stochastic SMC-CNAs indicating genomic destabilization. Targeted resequencing of 301 known predisposition and somatic driver loci revealed mutations and rare variants in genes related to maintenance of genomic integrity: BRCA1 (p.Gln1756Profs*74, p.Arg504Cys), BRCA2 (p.Asn3124Ile), NCOR1 (p.Pro1570Glnfs*45), PALB2 (p.Ser500Pro), and TP53 (p.Arg306*). Co-occurrence of gross SMC-CNAs along with point mutations or rare variants in genes responsible for safeguarding genomic integrity highlights the temporal and spatial neoplastic potential of uninvolved glandular tissue in breast cancer patients.

An Improved Breast Epithelial Sampling Method for Molecular Profiling and Biomarker Analysis in Women at Risk for Breast Cancer

BACKGROUND

There is a strong need to define the molecular changes in normal at-risk breast epithelium to identify biomarkers and new targets for breast cancer prevention and to develop a molecular signature for risk assessment. Improved methods of breast epithelial sampling are needed to promote whole-genome molecular profiling, increase ductal epithelial cell yield, and reduce sample cell heterogeneity.

METHODS

We developed an improved method of breast ductal sampling with ductal lavage through a 22-gauge catheter and collection of ductal samples with a microaspirator. Women at normal risk or increased risk for breast cancer were studied. Ductal epithelial samples were analyzed for cytopathologic changes, cellular yield, epithelial cell purity, quality and quantity of DNA and RNA, and use in multiple downstream molecular applications.

RESULTS

We studied 50 subjects, including 40 subjects at normal risk for breast cancer and 37 subjects with non-nipple aspirate fluid-yielding ducts. This method provided multiple 1.0 mL samples of high ductal epithelial cell content (median ≥8 samples per subject of ≥5,000 cells per sample) with 80%-100% epithelial cell purity. Extraction of a single intact ductal sample (fluid and cells) or the separate frozen cellular component provided DNA and RNA for multiple downstream studies, including quantitative reverse transcription- polymerase chain reaction (PCR) for microRNA, quantitative PCR for the human telomerase reverse transcriptase gene, whole-genome DNA amplification, and array comparative genomic hybridization analysis.

CONCLUSION

An improved breast epithelial sampling method has been developed, which should significantly expand the acquisition and biomarker analysis of breast ductal epithelium in women at risk for breast cancer.

Development of an ammonium sulfate DNA extraction method for obtaining amplifiable DNA in a small number of cells and its application to clinical specimens

DNA extraction from microdissected cells has become essential for handling clinical specimens with advances in molecular pathology. Conventional methods have limitations for extracting amplifiable DNA from specimens containing a small number of cells. We developed an ammonium sulfate DNA extraction method (A) and compared it with two other methods (B and C). DNA quality and quantity, β-globin amplification, and detectability of two cancer associated gene mutations were evaluated. Method A showed the best DNA yield, particularly when the cell number was very low. Amplification of the β-globin gene using DNA from the SNU 790 cell line and papillary thyroid carcinoma (PTC) cells extracted with Method A demonstrated the strongest band. BRAF(V600E) mutation analysis using ethanol-fixed PTC cells from a patient demonstrated both a "T" peak increase and an adjacent "A" peak decrease when 25 and 50 cells were extracted, whereas mutant peaks were too low to be analyzed using the other two methods. EGFR mutation analysis using formalin-fixed paraffin-embedded lung cancer tissues demonstrated a mutant peak with Method A, whereas the mutant peak was undetectable with Methods B or C. Method A yielded the best DNA quantity and quality with outstanding efficiency, particularly when paucicellular specimens were used.

Lipid metabolism genes in contralateral unaffected breast and estrogen receptor status of breast cancer

Risk biomarkers that are specific to estrogen receptor (ER) subtypes of breast cancer would aid the development and implementation of distinct prevention strategies. The contralateral unaffected breast of women with unilateral breast cancer (cases) is a good model for defining subtype-specific risk because women with ER-negative (ER-) index primaries are at high risk for subsequent ER-negative primary cancers. We conducted random fine needle aspiration of the unaffected breasts of cases. Samples from 30 subjects [15 ER-positive (ER+) and 15 ER- cases matched for age, race and menopausal status] were used for Illumina expression array analysis. Findings were confirmed using quantitative real-time PCR (qRT-PCR) in the same samples. A validation set consisting of 36 subjects (12 ER+, 12 ER- and 12 standard-risk healthy controls) was used to compare gene expression across groups. ER- case samples displayed significantly higher expression of 18 genes/transcripts, 8 of which were associated with lipid metabolism on gene ontology analysis (GO: 0006629). This pattern was confirmed by qRT-PCR in the same samples, and in the 24 cases of the validation set. When compared to the healthy controls in the validation set, significant overexpression of 4 genes (DHRS2, HMGCS2, HPGD and ACSL3) was observed in ER- cases, with significantly lower expression of UGT2B11 and APOD in ER+ cases, and decreased expression of UGT2B7 in both subtypes. These data suggest that differential expression of lipid metabolism genes may be involved in the risk for subtypes of breast cancer, and are potential biomarkers of ER-specific breast cancer risk.

Precancer: sequentially acquired or predetermined?

Recognition of focal morphological intraepithelial lesions associated with the eventual development of invasive cancer has long been the sine qua non of precancer. Empirically, precancers are associated with a morphological continuum from atypia to dysplasia and invasive neoplasia. Such lesions are used as early indicators of cancers and have dramatically reduced mortality from cancers of the colon, uterine cervix, and breast. Progression has been modeled as a linear, stepwise process. Some molecular evidence supports a linear model. However, clinical studies now suggest that preexisting cofactors such as human papilloma virus (HPV) in cervical cancer determines the cell fate. Other clinical studies such as bladder, prostate, and breast suggest that many intraepithelial lesions do not progress to malignancy. The more recent experimental analyses reveal that the key molecular and genetic events even predate the emergence of visible lesions. Thus, a new nonlinear, parallel model is proposed. The parallel model suggests an origin in a putative progenitor cell that expands and invades. The clinical outcome is thus predetermined. If correct, this model suggests that "progression" to malignancy is epigenetic. Further, future assessment of biological potential will involve identification and genetic analysis of the progenitor cell populations.

[Early loss of heterozygosity on chromosome arm 16q in flat epithelial atypia of the breast. Detection by microsatellite analyses]

With the improvement of breast carcinoma screening, pre-malignant cell lesions such as flat epithelial atypia (FEA) are detected more frequently. Several studies have demonstrated that FEA show features of a ductal neoplasia, but is it really a precursor lesion? We have started a comparative genetic analysis of a panel of nine microsatellite markers on six different chromosomal regions to investigate whether FEAs show the same characteristic genetic alterations as ductal carcinomas in situ (DCISs) and invasive carcinoma of the breast. FEAs, DCISs and invasive carcinomas of the same patients were microdissected using PALM micro laser technology. DNA was isolated using the QIAamp DNA Micro Kit (QIAGEN). We have investigated a set of the polymorphic microsatellite markers D7S522, D8S522, NEFL, D10S541 (PTEN), D13S153 (RB1), D16S400, D16S402, D16S422 and D17S855 (BRCA1) using multiplex PCR for the detection of allelic imbalances. Most of the investigated FEAs showed a lower frequency of loss of heterozygosity than associated DCISs or invasive carcinomas. However, we were able to detect the same alterations in FEAs as in DCISs or invasive carcinomas in a number of cases. Notably, the microsatellite marker on 16q showed more prevalent allelic imbalances in FEAs than the other investigated markers. One of the hallmarks in the pathogenesis of a large subgroup of invasive breast carcinomas is the early loss of chromosome arm 16q. In this study, we were able to detect frequent genetic alterations on chromosome 16q in FEAs, associated DCISs and invasive carcinomas. This suggests that FEA is a precursor lesion in the low-grade pathway.

Genomic instability demonstrates similarity between DCIS and invasive carcinomas

PURPOSE

To assess telomere DNA content (TC) and the number of sites of allelic imbalance (AI) as a function of breast cancer progression.

EXPERIMENTAL DESIGN

TC and AI were determined in 54 histologically normal tissues, 10 atypical ductal hyperplasias (ADH), 122 in situ ductal carcinomas (DCIS) and 535 invasive carcinomas (Stage I-IIIA).

RESULTS

TC was altered in ADH lesions (20%), DCIS specimens (53%) and invasive carcinomas (51%). The mean number of sites of AI was 0.26 in histologically normal group tissue, increased to 1.00 in ADH, 2.94 in DCIS, and 3.07 in invasive carcinomas. All groups were statistically different from the histologically normal group (P < 0.001 for each); however, there was no difference between DCIS and the invasive groups.

CONCLUSIONS

Genomic instability increases in ADH and plateaus in DCIS without further increase in the invasive carcinomas, supporting the notion that invasive carcinomas evolve from or in parallel with DCIS.

Effectiveness of the CRCAPRO program in identifying patients suspected for HNPCC

Subjects affected by hereditary non-polyposis colorectal cancer exhibit a high susceptibility to colon and extracolonic tumours, due to MMR gene defects. Revised Bethesda criteria are used to select patients as candidates for genetic tests. Recently, the CRCAPRO model has been developed, based on family history of colorectal and endometrial cancers. Our study aims to evaluate the reliability of CRCAPRO in identifying mutation carriers. We used the CRCAPRO program to evaluate carrier probability risk in 99 patients fulfilling Amsterdam or Bethesda guidelines. MLH1 and MSH2 were studied by direct sequencing in all the 99 patients, and the study of microsatellite instability and of MMR proteins expression was performed. Nine MLH1 and nine MSH2 germline mutations were identified. Five out of the nine patients with MLH1 mutation showed a CRCAPRO risk evaluation of less than 20%. The same happened for four out of nine patients with MSH2 mutation. Of the 17 patients with an estimated risk of more than 80%, only four harboured a mutation, all in the MSH2 gene. The highest risk calculated by the CRCAPRO system in the nine carriers of a MLH1 mutation has been 31.7%. In our experience, the CRCAPRO program sensitivity and specificity appears to be low but needs to be further evaluated in larger samples.

The use of molecular assays to establish definitively the clonality of ipsilateral breast tumor recurrences and patterns of in-breast failure in patients with early-stage breast cancer treated with breast-conserving therapy

BACKGROUND

Results from numerous trials have indicated that breast-conserving therapy (BCT) produces outcomes equivalent to those produced by mastectomy in terms of both locoregional control and survival. However, conservative treatment has resulted in the dilemma of how best to address recurrences when they appear in a breast treated previously with radiation therapy. Attempts have been made to characterize ipsilateral breast tumor recurrences (IBTRs) as either true recurrences of the treated malignancy or new primary carcinomas, because cancers that represent new primary tumors may be associated with a more favorable prognosis compared with cancers that represent true recurrences.

METHODS

The authors studied the clonality of IBTRs relative to the initial invasive carcinomas by using a polymerase chain reaction loss-of-heterozygosity molecular comparison assay in 29 patients who received breast-conserving therapy (BCT).

RESULTS

Twenty-two IBTRs (76%) were related clonally to the initial carcinoma, and 7 IBTRs (24%) were clonally different. Clonally related IBTRs were more frequently higher grade (72.2% vs 14.3%; P = .009) and developed sooner after initial treatment (mean time to IBTR, 4.04 years in clonally related IBTRs vs 9.25 years in clonally different IBTRs; P = .002). Six patients subsequently developed distant metastases, and 5 of those patients (83.3%) had clonally related IBTRs. Clinical IBTR classification and molecular clonality assay results differed in 30% of all patients. The proportion of IBTRs that were related clonally at 5 years, 10 years, and 15 years after BCT were 93%, 67%, and 33%, respectively.

CONCLUSIONS

Clinical classifications of IBTRs were unreliable methods for determining clonality in many patients. Molecular clonality assays provided a reliable means of identifying patients who may benefit from aggressive systemic therapy at the time of IBTR and also provided a more accurate assessment of the efficacy of various forms of local therapy.

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.

NSAIDs modulate CDKN2A, TP53, and DNA content risk for progression to esophageal adenocarcinoma

BACKGROUND

Somatic genetic CDKN2A, TP53, and DNA content abnormalities are common in many human cancers and their precursors, including esophageal adenocarcinoma (EA) and Barrett's esophagus (BE), conditions for which aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) have been proposed as possible chemopreventive agents; however, little is known about the ability of a biomarker panel to predict progression to cancer nor how NSAID use may modulate progression. We aimed to evaluate somatic genetic abnormalities with NSAIDs as predictors of EA in a prospective cohort study of patients with BE.

METHODS AND FINDINGS

Esophageal biopsies from 243 patients with BE were evaluated at baseline for TP53 and CDKN2A (p16) alterations, tetraploidy, and aneuploidy using sequencing; loss of heterozygosity (LOH); methylation-specific PCR; and flow cytometry. At 10 y, all abnormalities, except CDKN2A mutation and methylation, contributed to EA risk significantly by univariate analysis, ranging from 17p LOH (relative risk [RR] = 10.6; 95% confidence interval [CI] 5.2-21.3, p < 0.001) to 9p LOH (RR = 2.6; 95% CI 1.1-6.0, p = 0.03). A panel of abnormalities including 17p LOH, DNA content tetraploidy and aneuploidy, and 9p LOH was the best predictor of EA (RR = 38.7; 95% CI 10.8-138.5, p < 0.001). Patients with no baseline abnormality had a 12% 10-y cumulative EA incidence, whereas patients with 17p LOH, DNA content abnormalities, and 9p LOH had at least a 79.1% 10-y EA incidence. In patients with zero, one, two, or three baseline panel abnormalities, there was a significant trend toward EA risk reduction among NSAID users compared to nonusers (p = 0.01). The strongest protective effect was seen in participants with multiple genetic abnormalities, with NSAID nonusers having an observed 10-y EA risk of 79%, compared to 30% for NSAID users (p < 0.001).

CONCLUSIONS

A combination of 17p LOH, 9p LOH, and DNA content abnormalities provided better EA risk prediction than any single TP53, CDKN2A, or DNA content lesion alone. NSAIDs are associated with reduced EA risk, especially in patients with multiple high-risk molecular abnormalities.

Combined breast ductal lavage and ductal endoscopy for the evaluation of the high-risk breast: a feasibility study

BACKGROUND AND OBJECTIVES

Evaluation of the ductal epithelium of the breast at increased risk for breast cancer is needed to define the carcinogenic pathway, for risk assessment, and to improve selection of women for chemoprevention therapy. We studied the feasibility of combining breast ductal endoscopy with ductal lavage in the high-risk contralateral breast of women with ipsilateral breast cancer for the evaluation of high-risk ducts and acquisition of ductal epithelial cells for analysis.

METHODS

Breast ducts were studied by ductal lavage and ductal endoscopy, and epithelial cell content studied cytologically and quantitatively.

RESULTS

Twenty-five subjects and 44 ducts, including 22 (50.0%) which did not produce nipple aspirate fluid (NAF), were studied. Cellular atypia was present in five subjects. Ductal endoscopy was performed on 1 or more ducts in 24 subjects. Structural changes were noted in 63.6% of the ducts, most commonly fibrous stranding or bridging. Ductal sampling with endoscopic brush and coil sampling devices provided additional cellular samples of relatively pure ductal epithelial content (> or = 91% purity) in 8/11 subjects.

CONCLUSIONS

Breast ductal endoscopy combined with ductal lavage represents a feasible approach for characterizing the ducts and ductal epithelium of the high-risk breast, especially in a research setting.

A comparison of five methods for extracting DNA from paucicellular clinical samples

Translational protocols in cancer and carcinogenesis often require isolation of genomic DNA from paucicellular clinical samples. DNA extraction methods for PCR-based applications should optimize the recovery of amplifiable DNA. We compared five methods for DNA extraction in paucicellular epithelial and lymphocyte samples using proportion of extractions producing amplifiable DNA and mean real-time PCR Ct values for GAPDH as the endpoint measures. The methods included solid-phase DNA adsorption (QIAamp), sequential protein and DNA precipitation (Puregene), magnetic bead adsorption (Dynabeads), phenol-chloroform extraction, and single-step proteinase K digestion. In general, the performance of the three commercial kits was superior to either phenol-chloroform extraction or single-step proteinase K digestion. However, QIAamp and Puregene produced amplifiable DNA more frequently than Dynabeads for starting cell numbers <50,000. GAPDH Ct values for QIAamp extractions showed the greatest dynamic range and the best linearity across the range of starting cell numbers, but QIAamp was not statistically significantly superior to Puregene. Of the three commercial kits, Puregene is the least expensive. QIAamp and Puregene DNA extraction methods are well-suited for the preparation of paucicellular clinical samples for PCR-based assays.

Telomere DNA content and allelic imbalance demonstrate field cancerization in histologically normal tissue adjacent to breast tumors

Cancer arises from an accumulation of mutations that promote the selection of cells with progressively malignant phenotypes. Previous studies have shown that genomic instability, a hallmark of cancer cells, is a driving force in this process. In the present study, two markers of genomic instability, telomere DNA content and allelic imbalance, were examined in two independent cohorts of mammary carcinomas. Altered telomeres and unbalanced allelic loci were present in both tumors and surrounding histologically normal tissues at distances at least 1 cm from the visible tumor margins. Although the extent of these genetic changes decreases as a function of the distance from the visible tumor margin, unbalanced loci are conserved between the surrounding tissues and the tumors, implying cellular clonal evolution. Our results are in agreement with the concepts of "field cancerization" and "cancer field effect," concepts that were previously introduced to describe areas within tissues consisting of histologically normal, yet genetically aberrant, cells that represent fertile grounds for tumorigenesis. The finding that genomic instability occurs in fields of histologically normal tissues surrounding the tumor is of clinical importance, as it has implications for the definition of appropriate tumor margins and the assessment of recurrence risk factors in the context of breast-sparing surgery.

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.

Ductal carcinoma in situ of the breast with different histopathological grades and corresponding new breast tumour events: analysis of loss of heterozygosity

To compare chromosomal alterations in ductal carcinoma in situ (DCIS) of different histopathological grades and to study aberrations between primary DCIS and corresponding ipsi- or contralateral new in situ or invasive tumours, a study was undertaken of the pattern of loss of heterozygosity (LOH) at chromosomal regions in which LOH has previously been described in invasive breast cancer. LOH was analysed using 19 microsatellite markers located on chromosomes 3p, 6q, 8p, 8q, 9p, 11p, 11q, 16q, 17p, and 17q in 30 women with a primary DCIS. Eleven women with DCIS of grade 1 and 19 with grade 3 according to the EORTC classification system were included. In six patients LOH was also analysed in a subsequent new breast cancer. Fractional allelic loss (FAL, the ratio of chromosomal arms where allelic loss was detected divided by the total number of chromosomal arms with informative markers) was statistically significantly higher in grade 1 DCIS compared with grade 3 (p=0.02) for the 19 loci, indicating that the amount of allelic loss does not correlate with increasing aggressiveness of the studied tumours. Also observed was a complete heterogeneity of LOH in the primary DCIS and their corresponding new events, suggesting that these events probably developed from genetically divergent clones.

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.

Germ-line mutations in BRCA1 or BRCA2 in the normal breast are associated with altered expression of estrogen-responsive proteins and the predominance of progesterone receptor A

The breast cancer susceptibility genes BRCA1 and BRCA2 are responsible for a large proportion of familial breast and ovarian cancer, yet little is known of how disruptions in the functions of the proteins these genes encode increased cancer risk preferentially in hormone-dependent tissue. There is no information on whether a germ-line mutation in BRCA1 or BRCA2 causes disruptions in hormone-signaling pathways in the normal breast. In this study markers of hormone responsiveness were measured in prophylactically removed normal breast tissue (n = 31) in women bearing a germ-line pathogenic mutation in one of the BRCA genes. The estrogen receptor (ER) and proteins associated with ER action in hormone-sensitive tissues, namely, PS2 and the progesterone receptor (PR), were detected immunohistochemically. ER expression was not different in BRCA mutation carriers than in noncarriers, but there was a reduction in PS2 expression. PR expression was also reduced, and there was a striking lack of expression of the PRB isoform, which resulted in cases with PRA-only expression in BRCA1 and BRCA2 mutation carriers. The alterations in PS2 and PR expression were similar in the BRCA1 and BRCA2 carriers, demonstrating that although these proteins are structurally and functionally distinct, there is overlap in their interaction with hormone-signaling pathways. This study provides evidence for altered cell function arising from loss of function of one BRCA allele in the normal breast, leading to PS2 loss, preferential PRB loss, and expression of PRA alone. In breast cancer development, PRA overexpression becomes evident in premalignant lesions and is associated with features of poor prognosis in invasive disease and altered cell function in vitro. The results of this study suggest that heterozygosity for a germ-line mutation in BRCA1 or BRCA2 results in development of PRA predominance. This is likely to lead to changes in progesterone signaling in hormone-dependent tissues, which may be a factor in the increased risk of cancer in these tissues in women with germ-line BRCA1 or BRCA2 mutations.

Ductal lavage: clinical utility and future promise

This article discusses the use of ductal lavage to enhance the tolerability, efficiency, and reproducibility of collecting breast duct epithelial cells for analysis for breast cancer risk assessment. Aspects discussed include the rationale for use of ductal lavage, identification of appropriate candidates for the procedure, clinical implications, ongoing evaluation of the procedure, and its future utility.

Unbiased whole-genome amplification directly from clinical samples

Preparation of genomic DNA from clinical samples is a bottleneck in genotyping and DNA sequencing analysis and is frequently limited by the amount of specimen available. We use Multiple Displacement Amplification (MDA) to amplify the whole genome 10,000-fold directly from small amounts of whole blood, dried blood, buccal cells, cultured cells, and buffy coats specimens, generating large amounts of DNA for genetic testing. Genomic DNA was evenly amplified with complete coverage and consistent representation of all genes. All 47 loci analyzed from 44 individuals were represented in the amplified DNA at between 0.5- and 3.0-fold of the copy number in the starting genomic DNA template. A high-fidelity DNA polymerase ensures accurate representation of the DNA sequence. The amplified DNA was indistinguishable from the original genomic DNA template in 5 SNP and 10 microsatellite DNA assays on three different clinical sample types for 20 individuals. Amplification of genomic DNA directly from cells is highly reproducible, eliminates the need for DNA template purification, and allows genetic testing from small clinical samples. The low amplification bias of MDA represents a dramatic technical improvement in the ability to amplify a whole genome compared with older, PCR-based methods.

Rating the risk factors for breast cancer

OBJECTIVE

To update and summarize evidence of risk factors for breast cancer.

SUMMARY BACKGROUND DATA

Women who are at high risk for breast cancer have a variety of options available to them, including watchful waiting, prophylactic surgery, and chemoprevention. It is increasingly important to accurately assess a patient's risk profile to ensure that the cost/benefit ratio of the selected treatment is favorable.

METHODS

Estimates of relative risk for documented risk factors were obtained from seminal papers identified in previous reviews. These estimates were updated where appropriate with data from more recent reports using large sample sizes or presenting meta-analyses of previous studies. These reports were identified from a review of the Medline database from 1992 to 2002.

RESULTS

Risk factors that have received a great deal of publicity (hormone use, alcohol consumption, obesity, nulliparity) present a relatively modest relative risk for breast cancer (<2). Factors associated with a prior history of neoplastic disease or atypical hyperplasia and factors associated with a genetic predisposition significantly affect the risk of breast cancer, with relative risks ranging from 3 (for some cases of positive family history) to 200 (for premenopausal women positive for a BRCA mutation).

CONCLUSIONS

More precise tools, based on techniques of molecular biology such as microarray analysis, will be needed to assess individual risk for breast cancer.