Premalignant and in situ breast disease: biology and clinical implications

Most types of invasive breast cancer are thought to evolve over long periods from specific preexisting benign lesions. Of the many types of benign entities found in the human breast, only a few have clinically significant premalignant potential. Currently, the best-characterized premalignant lesions are atypical ductal hyperplasia, atypical lobular hyperplasia, and lobular carcinoma in situ. Ductal carcinoma in situ is considered to be a preinvasive malignant lesion. Two additional lesions, unfolded lobules and usual ductal hyperplasia, are sometimes considered to be very early premalignant epithelial abnormalities. Premalignant lesions are currently defined by their histologic features, and not all necessarily progress to invasive cancer. This suggests that although lesions within specific categories look alike, they must possess underlying genetic differences that cause some to remain stable and others to advance. The development of modern molecular genetic techniques has allowed breast cancer researchers to clarify the multistep model of breast carcinogenesis. Recent studies indicate that cancer evolves by highly diverse genetic mechanisms, and research into these altered pathways may identify specific early defects that might be targeted to prevent progression of premalignant lesions to invasive cancer. Current clinical management is heterogeneous and depends on histologic examination and individual patient factors. Options for breast cancer risk reduction and prevention are available.     

Retinoids and their receptors in cancer development and chemoprevention.

Retinoids play an important role in regulating the growth and differentiation of normal, premalignant and malignant cell types, especially epithelial cells, mainly through interaction with two types of nuclear receptors: retinoic acid receptors (RARalpha, beta and gamma) and retinoid X receptors (RXRalpha, beta and gamma). Vitamin A deficiency in experimental animals has been associated with a higher incidence of cancer and with increased susceptibility to chemical carcinogens. This is in agreement with the epidemiological studies indicating that individuals with a lower dietary vitamin A intake are at a higher risk to develop cancer. At the molecular level, aberrant expression and function of nuclear retinoid receptors have been found in various types of cancer including premalignant lesions. Thus, aberrations in retinoid signaling are early events in carcinogenesis. Retinoids at pharmacological doses exhibit a variety of effects associated with cancer prevention. They suppress transformation of cells in vitro, inhibit carcinogenesis in various organs in animal models, reduce premalignant human epithelial lesions and prevent second primary tumors following curative therapy for epithelial malignancies such as head and neck, lung, liver, and breast cancer.     

Histological and biological evolution of human premalignant breast disease

Most human invasive breast cancers (IBCs) appear to develop over long periods of time from certain pre-existing benign lesions. Of the many types of benign lesions in the human breast, only a few appear to have significant premalignant potential. The best characterized of these include atypical hyperplasias and in situ carcinomas and both categories are probably well on along the evolutionary pathway to IBC. Very little is known about earlier premalignant alterations. All types of premalignant breast lesions are relatively common but only a small proportion appear to progress to IBC. They are currently defined by their histological features and their prognosis is imprecisely estimated from indirect epidemiological evidence. Although lesions within specific categories look alike, they must possess underlying biological differences causing some to remain stable and others to progress. Recent studies suggest that they evolve by highly diverse genetic mechanisms and research into these altered pathways may identify specific early defects that can be targeted to prevent premalignant lesions from developing or becoming cancerous. It is far more rational to think that breast cancer can be prevented than cured once it has developed fully. This review discusses histological models of human premalignant breast disease that provide the framework for scientific investigations into the biological alterations behind them and examples of specific biological alterations that appear to be particularly important.     

Lung cancer chemoprevention

Lung cancer is the leading cause of cancer death in the United States, and the majority of diagnoses are made in former smokers. Although avoidance of tobacco abuse and smoking cessation clearly will have the greatest impact on lung cancer development, effective chemoprevention could prove to be more effective than treatment of established, advanced-stage disease. Chemoprevention is the use of dietary or pharmaceutical agents to reverse or block the carcinogenic process and has been successfully applied to common malignancies other than lung (including recent reports on the prevention of breast cancer in high-risk individuals). Despite previous studies in lung cancer chemoprevention failing to identify effective agents, our ability to define the highest-risk populations and the understanding of lung tumor and premalignant biology continue to make advances. Squamous cell carcinogenesis in the bronchial epithelium starts with normal epithelium and progresses through hyperplasia, metaplasia, dysplasia, and carcinoma in situ to invasive cancer. Precursor lesions also have been identified for adenocarcinoma, and these premalignant lesions are targeted by chemopreventive agents in current and future trials. Chemopreventive agents can currently only be recommended as part of well-designed clinical trials, and multiple trials have recently been completed or are enrolling subjects.     

Worldwide experiences of endoscopic submucosal dissection: not just Eastern acrobatics

The high incidence of gastric cancer has led to the initiation of cancer screening programs.As a result,the number of early gastric cancer cases has increased and consequentially,the cancer mortality rate has decreased.Moreover,the development of minimally invasive endoscopic treatment has been introduced for these early lesions.Endoscopic submucosal dissection(ESD) is now recognized as one of the preferred treatment modalities for premalignant gastrointestinal epithelial lesions and early gastric cancer wi...     

Splicing program of human MENA produces a previously undescribed isoform associated with invasive,mesenchymal-like breast tumors

Human mena (hMENA), a member of the actin cytoskeleton regulators Ena/VASP, is overexpressed in high-risk preneoplastic lesions and in primary breast tumors and has been identified as playing a role in invasiveness and poor prognosis in breast cancers that express HER2. Here we identify a unique isoform, hMENAΔv6, derived from the hMENA alternative splicing program. In an isogenic model of human breast cancer progression, we show that hMENA^11a is expressed in premalignant cells, whereas hMENAΔv6 expression is restricted to invasive cancer cells. “Reversion” of the malignant phenotype leads to concurrent down-regulation of all hMENA isoforms. In breast cancer cell lines, isoform-specific hMENA overexpression or knockdown revealed that in the absence of hMENA^11a, overexpression of hMENAΔv6 increased cell invasion, whereas overexpression of hMENA^11a reduced the migratory and invasive ability of these cells. hMENA^11a splicing was shown to be dependent on the epithelial regulator of splicing 1 (ESRP1), and forced expression of ESRP1 in invasive mesenchymal breast cancer cells caused a phenotypic switch reminiscent of a mesenchymal-to-epithelial transition (MET) characterized by changes in the cytoskeletal architecture, reexpression of hMENA^11a, and a reduction in cell invasion. hMENA-positive primary breast tumors, which are hMENA^11a-negative, are more frequently E-cadherin low in comparison with tumors expressing hMENA^11a. These data suggest that polarized and growth-arrested cellular architecture correlates with absence of alternative hMENA isoform expression, and that the hMENA splicing program is relevant to malignant progression in invasive disease.     

Methylation of estrogen receptor beta promoter correlates with loss of ER-beta expression in mammary carcinoma and is an early indication marker in premalignant lesions

The function of estrogen receptor beta (ER-beta) in mammary tissue is not completely understood. While early observations were often conflicting, more recent data suggest an important role as a tumor-suppressor gene. A decrease of ER-beta expression has been observed in ductal carcinoma in situ and invasive carcinoma as compared with benign mammary epithelial cells. The loss of ER-beta resulted in abnormal growth of mammary epithelial cells. We have previously shown that the mRNA expression of the ER-beta gene is almost totally suppressed in breast carcinomas from patients with a poor prognosis. Here we analyzed whether methylation changes in the different promoters of ER-beta are responsible for the loss of expression of the gene. A methylation assay with high specificity and sensitivity was developed, and a panel of breast tissue samples (n = 175) was characterized for methylation status. In contrast to benign breast, more than two-thirds of invasive breast cancers showed a high degree of methylation. Importantly, increased methylation was also detectable in numerous premalignant lesions. By analysis of breast tumors, previously characterized by gene-expression profiling, methylation was predominantly detected in a subgroup of patients with an unfavorable prognosis, suggesting a possible prognostic value of the ER-beta methylation status. We also investigated the structural characteristics of the two ER-beta promoters, which were both found to be closely associated with a second, downstream, localized and opposite-oriented promoter. However, we could not detect endogenous antisense RNA transcribed from these promoters, which may be involved in epigenetic gene silencing. We also failed to induce ER-beta promoter methylation by expressing siRNAs in cell lines. Interestingly, by comparing the promoter sequences of ER-beta with other genes known to be epigenetically inactivated in breast cancers, we identified a sequence motif possibly involved in promoter methylation.     

Reconstruction of functionally normal and malignant human breast tissues in mice

The study of normal breast epithelial morphogenesis and carcinogenesis in vivo has largely used rodent models. Efforts at studying mammary morphogenesis and cancer with xenotransplanted human epithelial cells have failed to recapitulate the full extent of development seen in the human breast. We have developed an orthotopic xenograft model in which both the stromal and epithelial components of the reconstructed mammary gland are of human origin. Genetic modification of human stromal cells before the implantation of ostensibly normal human mammary epithelial cells resulted in the outgrowth of benign and malignant lesions. This experimental model allows for studies of human epithelial morphogenesis and differentiation in vivo and underscores the critical role of heterotypic interactions in human breast development and carcinogenesis.     

Mining immune-related genes with prognostic value in the tumor microenvironment of breast invasive ductal carcinoma

The tumor microenvironment (TME) plays an important role in the development of breast cancer. Due to limitations in experimental conditions, the molecular mechanism of TME in breast cancer has not yet been elucidated. With the development of bioinformatics, the study of TME has become convenient and reliable.Gene expression and clinical feature data were downloaded from The Cancer Genome Atlas database and the Molecular Taxonomy of Breast Cancer International Consortium database. Immune scores and stromal scores were calculated using the Estimation of Stromal and Immune Cells in Malignant Tumor Tissues Using Expression Data algorithm. The interaction of genes was examined with protein-protein interaction and co-expression analysis. The function of genes was analyzed by gene ontology enrichment analysis, Kyoto Encyclopedia of Genes and Genomes analysis and gene set enrichment analysis. The clinical significance of genes was assessed with Kaplan-Meier analysis and univariate/multivariate Cox regression analysis.Our results showed that the immune scores and stromal scores of breast invasive ductal carcinoma (IDC) were significantly lower than those of invasive lobular carcinoma. The immune scores were significantly related to overall survival of breast IDC patients and both the immune and stromal scores were significantly related to clinical features of these patients. According to the level of immune/stromal scores, 179 common differentially expressed genes and 5 hub genes with prognostic value were identified. In addition, the clinical significance of the hub genes was validated with data from the molecular taxonomy of breast cancer international consortium database, and gene set enrichment analysis analysis showed that these hub genes were mainly enriched in signaling pathways of the immune system and breast cancer.We identified five immune-related hub genes with prognostic value in the TME of breast IDC, which may partly determine the prognosis of breast cancer and provide some direction for development of targeted treatments in the future.     

In vivo positron-emission tomography imaging of progression and transformation in a mouse model of mammary neoplasia

Imaging mouse models of human cancer promises more effective analysis of tumor progression and reduction of the number of animals needed for statistical power in preclinical therapeutic intervention trials. This study utilizes positron emission tomography imaging of 2-[18F]-fluoro-deoxy-D-glucose to monitor longitudinal development of mammary intraepithelial neoplasia outgrowths in immunocompetent FVB/NJ mice. The mammary intraepithelial neoplasia outgrowth tissues mimic the progression of breast cancer from premalignant ductal carcinoma in situ to invasive carcinoma. Progression of disease is clearly evident in the positron emission tomography images, and tracer uptake correlates with histological evaluation. Furthermore, quantitative markers of disease extracted from the images can be used to track proliferation and progression in vivo over multiple time points.     

Mouse Mammary Tumour Virus (MMTV) in Human Breast Cancer—The Value of Bradford Hill Criteria

For many decades, the betaretrovirus, mouse mammary tumour virus (MMTV), has been a causal suspect for human breast cancer. In recent years, substantial new evidence has been developed. Based on this evidence, we hypothesise that MMTV has a causal role. We have used an extended version of the classic A. Bradford Hill causal criteria to assess the evidence. 1. Identification of MMTV in human breast cancers: The MMTV 9.9 kb genome in breast cancer cells has been identified. The MMTV genome in human breast cancer is up to 98% identical to MMTV in mice. 2. Epidemiology: The prevalence of MMTV positive human breast cancer is about 35 to 40% of breast cancers in Western countries and 15 to 20% in China and Japan. 3. Strength of the association between MMTV and human breast cancer: Consistency—MMTV env gene sequences are consistently five-fold higher in human breast cancer as compared to benign and normal breast controls. 4. Temporality (timing) of the association: MMTV has been identified in benign and normal breast tissues up to 10 years before the development of MMTV positive breast cancer in the same patient. 5. Exposure: Exposure of humans to MMTV leads to development of MMTV positive human breast cancer. 6. Experimental evidence: MMTVs can infect human breast cells in culture; MMTV proteins are capable of malignantly transforming normal human breast epithelial cells; MMTV is a likely cause of biliary cirrhosis, which suggests a link between MMTV and the disease in humans. 7. Coherence—analogy: The life cycle and biology of MMTV in humans is almost the same as in experimental and feral mice. 8. MMTV Transmission: MMTV has been identified in human sputum and human milk. Cereals contaminated with mouse fecal material may transmit MMTV. These are potential means of transmission. 9. Biological plausibility: Retroviruses are the established cause of human cancers. Human T cell leukaemia virus type I (HTLV-1) causes adult T cell leukaemia, and human immunodeficiency virus infection (HIV) is associated with lymphoma and Kaposi sarcoma. 10. Oncogenic mechanisms: MMTV oncogenesis in humans probably differs from mice and may involve the enzyme APOBEC3B. Conclusion: In our view, the evidence is compelling that MMTV has a probable causal role in a subset of approximately 40% of human breast cancers.     

Models of ovarian cancer--are we there yet?

Ovarian cancer is the most lethal of all gynecological cancers and arises most commonly from the surface epithelium. Successful clinical management of patients with epithelial ovarian cancer is limited by the lack of a reliable and specific method for early detection, and the frequent recurrence of chemoresistant disease. Experimental models are of crucial importance not only to understand the biological and genetic factors that influence the phenotypic characteristics of the disease but also to utilize as a basis for developing rational intervention strategies. Ovarian cancer cell lines derived from ascites or primary ovarian tumors have been used extensively and can be very effective for studying the processes controlling growth regulation and chemosensitivity or evaluating novel therapeutics, both in vitro and in xenograft models. While our limited knowledge of the initiating events of ovarian cancer has restricted the development of models in which the early pathogenic events can be studied, recent advances in the ability to manipulate gene expression in ovarian surface epithelial cells in vitro and in vivo have begun to provide insights into the molecular changes that may contribute to the development of ovarian cancer. This review highlights the strengths and weaknesses of some of the current models of ovarian cancer, with special consideration of the recent progress in modeling ovarian cancer using genetically engineered mice.     

Colonic cancer and polyps

Colorectal cancer (CRC) is one of the best studied cancers. It is easily accessible and develops slowly over several years from premalignant lesions (adenomatous polyps) to invasive cancers. The key molecular events in this sequence have been characterized. Different screening strategies have proven to be effective in lowering both the mortality and the incidence of CRC. Nevertheless, CRC is still the second leading cause of cancer-related deaths for both men and women in the USA and other Western countries. An estimated 130 000 new cases and more than 50 000 deaths have been diagnosed in the USA in 2000. Surgical resection remains the only curative treatment, and the likelihood of cure is greater when the disease is detected at an early stage. Hereditary non-polyposis colorectal cancer (HNPCC) and the different polyposis syndromes such as familial adenomatous polyposis (FAP) or Peutz-Jeghers disease are rare causes of CRC but have been a major focus of research in past years, helping with the understanding of the molecular events in carcinogenesis. This review summarizes our current knowledge of the pathogenesis and management of colorectal polyps and polyposis syndromes as well as sporadic CRC.     

Dachshund inhibits oncogene-induced breast cancer cellular migration and invasion through suppression of interleukin-8

Oncogene-mediated signaling to the host environment induces a subset of cytokines and chemokines. The Drosophila Dac gene promotes migration of the morphogenetic furrow during eye development. Expression of the cell-fate determination factor Dachshund (DACH1) was lost in poor prognosis invasive breast cancer. Mouse embryo fibroblasts derived from Dach1(-/-) mice demonstrated endogenous Dach1 constitutively represses cellular migration. DACH1 inhibited cellular migration and invasion of oncogene (Ras, Myc, ErbB2, c-Raf)-transformed human breast epithelial cells. An unbiased proteomic analysis identified and immunoneutralizing antibody and reconstitution experiments demonstrated IL-8 is a critical target of DACH1 mediating breast cancer cellular migration and metastasis in vivo. DACH1 bound the endogenous IL-8 promoter in ChIP assays and repressed the IL-8 promoter through the AP-1 and NF-kappaB binding sites. Collectively, our data identify a pathway by which an endogenous cell-fate determination factor blocks oncogene-dependent tumor metastasis via a key heterotypic mediator.     

Genetically defined mouse models that mimic natural aspects of human prostate cancer development

This review is focused on mouse models for prostate cancer that have been designed on the basis of genetic alterations that are frequently found in human prostate cancer. It begins with an analysis of the similarities and differences in the gross and microscopic anatomy of the mouse and human prostate glands, and extends to the pathologies induced in the genetically manipulated mouse prostate in comparison with the sporadic development of the disease in humans. Major achievements have been made in modeling human prostate cancer in mice in recent years. There are models which display slow, temporal development of increasingly severe preneoplastic lesions, which are remarkably restricted to the prostate gland, a property similar to the aging-related progression of these lesions in humans. Other models rapidly progress to local invasive adenocarcinoma, and, in some of them metastasis is manifested subsequently with defined kinetics. Global assessment of molecular changes in the prostate of the genetically manipulated mice is increasingly underscoring the validity of the models through identification of 'signature' genes which are associated with the organ-confined primary or distant metastases of human prostate cancer. Taken together, various 'natural' models depicting stages of the disease, ranging from the early preneoplastic lesions to metastatic prostate cancer, now provide new tools both for exploring the molecular mechanism underlying prostate cancer and for development or testing of new targeted therapies.     

HIN-1, a putative cytokine highly expressed in normal but not cancerous mammary epithelial cells

To identify molecular alterations implicated in the initiating steps of breast tumorogenesis, we compared the gene expression profiles of normal and ductal carcinoma in situ (DCIS) mammary epithelial cells by using serial analysis of gene expression (SAGE). Through the pair-wise comparison of normal and DCIS SAGE libraries, we identified several differentially expressed genes. Here, we report the characterization of one of these genes, HIN-1 (high in normal-1). HIN-1 expression is significantly down regulated in 94% of human breast carcinomas and in 95% of preinvasive lesions, such as ductal and lobular carcinoma in situ. This decrease in HIN-1 expression is accompanied by hypermethylation of its promoter in the majority of breast cancer cell lines (>90%) and primary tumors (74%). HIN-1 is a putative cytokine with no significant homology to known proteins. Reintroduction of HIN-1 into breast cancer cells inhibits cell growth. These results indicate that HIN-1 is a candidate tumor suppressor gene that is inactivated at high frequency in the earliest stages of breast tumorogenesis.