Genetic alterations in 'normal' luminal and myoepithelial cells of the breast.
ABSTRACT Chromosomal loci exhibiting loss of heterozygosity (LOH) at high frequency in invasive breast cancer have been investigated in 'normal' breast tissue from patients with carcinoma and from reduction mammoplasty specimens. Duct-lobular units dissected from paraffin-embedded tissues and 485 'normal' luminal and myoepithelial cell clones were studied. Overall, LOH was found in normal cells in 5/10 breast cancer cases and 1/3 reduction mammoplasty specimens. LOH was identified in normal cells adjacent to and distant from the tumour. In one case, all luminal and myoepithelial samples exhibited loss of the same allele on chromosome 13q. One case in which the patient had a germline truncating mutation in the BRCA1 gene exhibited LOH on 17q in 3/33 normal clones. One of these clones showed loss of wild-type allele indicating gene inactivation. This sample also had LOH at markers on chromosomes 11p and 13q. One of 93 clones from three reduction mammoplasties showed allele loss at a locus on chromosome 13q. The identification of LOH in breast lobules suggests that they may be clonal. The demonstration of genetic alteration in luminal and myoepithelial cells provides evidence for the presence of a common stem cell for the two epithelial cell types. LOH has been demonstrated in normal tissues near and away from the carcinoma, suggesting that genetic alterations are likely to be more heterogeneous and widespread than is currently envisaged, and probably occur very early in breast development. Homozygous deletion of BRCA1 per se does not appear to provide clonal advantage.
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ABSTRACT: RESUMEN El carcinoma ductal in situ incluye un grupo heterogéneo de lesiones con características, alteraciones genéticas, manifestación y com-portamiento clínico diversos. Debido al mayor uso de la mastografía de vigilancia, la detección del carcinoma ductal in situ puro se ha incrementado de manera importante. Los criterios diagnósticos del carcinoma ductal in situ dependen del grado de atipia citológica, pero en general incluyen características citonucleares y arquitecturales, la clonalidad de la población celular y la extensión de la lesión. Se han propuesto diversos sistemas de clasificación del carcinoma ductal in situ a fin de predecir la recurrencia de la enfermedad después de la resección quirúrgica, y la mayor parte de los sistemas se basa principalmente en el grado nuclear y, en segundo lugar, en la polarización celular y en la ausencia o presencia de necrosis. Debido a que el estándar de atención actual es la remoción quirúrgica de la lesión, la evolución natural del carcinoma ductal in situ no puede observarse directamente y, en la actualidad, es escasamente entendida. Sin embargo, varias líneas de evidencia apoyan el punto de vista de que el carcinoma ductal in situ sirve como un precursor no obligado de carcinoma invasivo. Debido a su naturaleza típicamente localizada, se ha demostrado que el carcinoma ductal in situ es tratable, en la mayoría de los casos, con escisión sola, generalmente en conjunto con radioterapia coadyuvante, con tasas bajas de recurrencia local. El riesgo de recurrencia depende de las características de la paciente –como el antecedente familiar de cáncer de mama y la edad al momento del diagnóstico– y de los factores del tumor, que incluyen extensión de la enfermedad, el tipo histológico, el grado nuclear, la presencia de comedonecrosis, el patrón arquitectural y el estado de los márgenes de resección. La baja morbilidad de la biopsia del ganglio linfático centinela impulsó el interés de usar esta biopsia en el manejo de pacientes con carcinoma ductal in situ; sin embargo, su uso rutinario en este marco es en la actualidad motivo de intenso debate. Nuestra capacidad de predecir el comportamiento biológico del carcinoma ductal in situ mejorará con el uso de nuevas técnicas moleculares para identificar los biomarcadores específicos, lo que permitirá el manejo óptimo de pacientes con carcinoma ductal in situ. Palabras clave: carcinoma ductal in situ. ABSTRACT Ductal carcinoma in situ (DCIS) includes a heterogeneous group of lesions with diverse morphologic features, genetic alterations, presenta-tion and clinical behavior. Following the increased use of screening mammography the detection of pure DCIS has dramatically increased. Diagnostic criteria for DCIS depend on the degree of cytologic atypia, but in general include cytonuclear and architectural features, clonality of the cell population and extent of the lesion. Numerous classification systems have been proposed for DCIS in order to predict disease recurrence after surgical resection, and most systems are based primarily on nuclear grade and secondarily on cell polarization and the absence or presence of necrosis. Since the current standard of care is surgical removal of the lesion, the natural history of DCIS cannot be directly observed and is currently poorly understood. However, several lines of evidence support the view that DCIS serves as a non-obligate precursor to invasive carcinoma. Due to its typically localized nature, DCIS was shown to be treatable in most cases with excision alone, usually in conjunction with adjuvant radiotherapy, with low rates of local recurrence. The risk of recurrence depends on both patient characteristics, such as family history of breast cancer and age at diagnosis, as well as on tumor factors including extent of disease, his-tological type, nuclear grade, presence of comedo-type necrosis, architectural pattern and the status of the resection margins. The advent of sentinel lymph node biopsy with its low morbidity prompted interest in its use in the management of patients with DCIS, however its routine use in this setting is currently a matter of intense debate. Our ability to predict the biologic behavior of DCIS will improve with the identification of specific biomarkers using new molecular techniques and will enable optimal management of patients with DCIS.Patología. 01/2010; 48:180-193.
Article: Selective regain of egfr gene copies in CD44+/CD24-/low breast cancer cellular model MDA-MB-468.[show abstract] [hide abstract]
ABSTRACT: Increased transcription of oncogenes like the epidermal growth factor receptor (EGFR) is frequently caused by amplification of the whole gene or at least of regulatory sequences. Aim of this study was to pinpoint mechanistic parameters occurring during egfr copy number gains leading to a stable EGFR overexpression and high sensitivity to extracellular signalling. A deeper understanding of those marker events might improve early diagnosis of cancer in suspect lesions, early detection of cancer progression and the prediction of egfr targeted therapies. The basal-like/stemness type breast cancer cell line subpopulation MDA-MB-468 CD44high/CD24-/low, carrying high egfr amplifications, was chosen as a model system in this study. Subclones of the heterogeneous cell line expressing low and high EGF receptor densities were isolated by cell sorting. Genomic profiling was carried out for these by means of SNP array profiling, qPCR and FISH. Cell cycle analysis was performed using the BrdU quenching technique. Low and high EGFR expressing MDA-MB-468 CD44+/CD24-/low subpopulations separated by cell sorting showed intermediate and high copy numbers of egfr, respectively. However, during cell culture an increase solely for egfr gene copy numbers in the intermediate subpopulation occurred. This shift was based on the formation of new cells which regained egfr gene copies. By two parametric cell cycle analysis clonal effects mediated through growth advantage of cells bearing higher egfr gene copy numbers could most likely be excluded for being the driving force. Subsequently, the detection of a fragile site distal to the egfr gene, sustaining uncapped telomere-less chromosomal ends, the ladder-like structure of the intrachromosomal egfr amplification and a broader range of egfr copy numbers support the assumption that dynamic chromosomal rearrangements, like breakage-fusion-bridge-cycles other than proliferation drive the gain of egfr copies. Progressive genome modulation in the CD44+/CD24-/low subpopulation of the breast cancer cell line MDA-MB-468 leads to different coexisting subclones. In isolated low-copy cells asymmetric chromosomal segregation leads to new cells with regained solely egfr gene copies. Furthermore, egfr regain resulted in enhanced signal transduction of the MAP-kinase and PI3-kinase pathway. We show here for the first time a dynamic copy number regain in basal-like/stemness cell type breast cancer subpopulations which might explain genetic heterogeneity. Moreover, this process might also be involved in adaptive growth factor receptor intracellular signaling which support survival and migration during cancer development and progression.BMC Cancer 03/2010; 10:78. · 3.01 Impact Factor
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ABSTRACT: To detect the molecular changes of malignancy in histologically normal breast (HNB) tissues, we recently developed a novel 117-gene-malignancy-signature. Here we report validation of our leading malignancy-risk-genes, topoisomerase-2-alpha (TOP2A), minichromosome-maintenance-protein-2 (MCM2) and "budding-uninhibited-by-benzimidazoles-1-homolog-beta" (BUB1B) at the protein level. Using our 117-gene malignancy-signature, we classified 18 fresh-frozen HNB tissues from 18 adult female breast cancer patients into HNB-tissues with low-grade (HNB-LGMA; N = 9) and high-grade molecular abnormality (HNB-HGMA; N = 9). Archival sections of additional HNB tissues from these patients, and invasive ductal carcinoma (IDC) tissues from six other patients were immunostained for these biomarkers. TOP2A/MCM2 expression was assessed as staining index (%) and BUB1B expression as H-scores (0-300). Increasing TOP2A, MCM2, and BUB1B protein expression from HNB-LGMA to HNB-HGMA tissues to IDCs validated our microarray-based molecular classification of HNB tissues by immunohistochemistry. We also demonstrated an increasing expression of TOP2A protein on an independent test set of HNB/benign/reductionmammoplasties, atypical-ductal-hyperplasia with and without synchronous breast cancer, DCIS and IDC tissues using a custom tissue microarray (TMA). In conclusion, TOP2A, MCM2, and BUB1B proteins are potential molecular biomarkers of malignancy in histologically normal and benign breast tissues. Larger-scale clinical validation studies are needed to further evaluate the clinical utility of these molecular biomarkers.Pathology research international. 01/2011; 2011:489064.