Stroma in breast development and disease

It is increasingly apparent that normal and malignant breast tissues require complex local and systemic stromal interactions for development and progression. During development, mammary cell fate specification and differentiation require highly regulated contextual signals derived from the stroma. Likewise, during breast carcinoma development, the tissue stroma can provide tumor suppressing and tumor-promoting environments that serve to regulate neoplastic growth of the epithelium. This review focuses on the role of the stroma as a mediator of normal mammary development, as well as a critical regulator of malignant conversion and progression in breast cancer. Recognition of the important role of the stroma during the progression of breast cancers leads to the possibility of new targets for treatment of the initial breast cancer lesion as well as prevention of recurrence.     

Proteomics of breast cancer: the quest for markers and therapeutic targets

Proteomics of breast cancer has already delivered significant data in terms of proteome profiling in addition to the identification of a few proteins of potential interest for diagnosis and treatment. With more pathological and experimental situations being studied, it now enters into a new phase dominated by the concepts of deep proteome analysis and the definition of protein-protein interaction networks leading to mammary cell deregulation and cancer progression. Together, what could be called "Systems Proteomics", integrating with information from the genomics and the physiopathology, is clearly emerging to become the frame for future investigations. However, difficulties ahead should not be underestimated. First, the proteome is complex, and current tools are still far from providing a definitive solution for its exploration. Second, breast cancer is a multifactorial disease which is so diverse that a great deal of time and efforts will be necessary to define its associated proteome modifications and translate it into practical applications for the clinic.     

Cancer stem cells--normal stem cells "Jedi" that went over to the "dark side"

Evidence has accumulated that cancer develops from a population of quiescent tissue committed/pluripotent stem cells (TCSC/PSC) or cells developmentally closely related to them that are distributed in various organs. To support this notion, stem cells (SC) are long lived cells and thus may become the subject of accumulating mutations that are crucial for initiation/progression of cancer. More important, they may maintain these mutations and pass them to the daughter stem cells. Therefore, mutations that occur in normal SC, accumulate during the life of an organism at the clonal level in the stem cell compartment committed to a given tissue/organ. As a consequence, this may lead to the malignant transformation of SC and tumor initiation. Furthermore, many biological features of normal and cancer SC such as the physiological trafficking of normal and metastasis of cancer stem cells involve similar molecular mechanisms, and we discuss these similarities here. Therefore, looking both at the origin and behavioral aspects we can envision cancer SC being normal SC "Jedi" that went over to the "dark side".     

Cancer Development and Progression: A Non-Adaptive Process Driven by Genetic Drift

The current mainstream in cancer research favours the idea that malignant tumour initiation is the result of a genetic mutation. Tumour development and progression is then explained as a sort of micro-evolutionary process, whereby an initial genetic alteration leads to abnormal proliferation of a single cell that leads to a population of clonally derived cells. It is widely claimed that tumour progression is driven by natural selection, based on the assumption that the initial tumour cells acquire some properties that endow such cells with a selective advantage over the normal cells from which the tumour cells are derived. The standard view assumes that the transformed bodily cell somehow acquires "responsiveness" to natural selection independently of the whole organism to which the cell belongs. Yet, it is never explained where such an acquired capacity to respond to natural selection by the individual bodily cell comes from. This situation poses many difficult questions that so far have been left unanswered. For example, there is no explanation why some cells belonging to an organised whole and as such having no independent capacity for survival, apparently become 'independent' entities, able to respond to selective pressures in an autonomous fashion and then to be evaluated by natural selection. Hereunder it is argued that such a qualitative change cannot be the consequence of specific genetic mutations. Moreover, it is shown that natural selection is unlikely to be acting within the organism during tumour development and progression and that tumour evolution is a random, non-adaptive process, driven by no fundamental biological principle. Thus, mutations in the so-called oncogenes and tumour suppressor genes observed in epithelial cancers (that constitute more than 90% of all cancers) are not the result of selection for better cellular growth or survival under restrictive conditions. Instead, here it is suggested that they are the consequence of genetic drift acting upon gene functions that become non-relevant, either for the individual or the species fitness, once the organism is past its reproductive prime and as such, they also become superfluous for cell survival in the short term. It is proposed that the origin of cancer is epigenetic and it is a consequence of the need for a continued turnover of the individuals that constitute a species.     

Tissue of origin determines cancer-associated CpG island promoter hypermethylation patterns

Background

Aberrant CpG island promoter DNA hypermethylation is frequently observed in cancer and is believed to contribute to tumor progression by silencing the expression of tumor suppressor genes. Previously, we observed that promoter hypermethylation in breast cancer reflects cell lineage rather than tumor progression and occurs at genes that are already repressed in a lineage-specific manner. To investigate the generality of our observation we analyzed the methylation profiles of 1,154 cancers from 7 different tissue types.

Results

We find that 1,009 genes are prone to hypermethylation in these 7 types of cancer. Nearly half of these genes varied in their susceptibility to hypermethylation between different cancer types. We show that the expression status of hypermethylation prone genes in the originator tissue determines their propensity to become hypermethylated in cancer; specifically, genes that are normally repressed in a tissue are prone to hypermethylation in cancers derived from that tissue. We also show that the promoter regions of hypermethylation-prone genes are depleted of repetitive elements and that DNA sequence around the same promoters is evolutionarily conserved. We propose that these two characteristics reflect tissue-specific gene promoter architecture regulating the expression of these hypermethylation prone genes in normal tissues.

Conclusions

As aberrantly hypermethylated genes are already repressed in pre-cancerous tissue, we suggest that their hypermethylation does not directly contribute to cancer development via silencing. Instead aberrant hypermethylation reflects developmental history and the perturbation of epigenetic mechanisms maintaining these repressed promoters in a hypomethylated state in normal cells.     

Fields and field cancerization: the preneoplastic origins of cancer: asymptomatic hyperplastic fields are precursors of neoplasia, and their progression to tumors can be tracked by saturation density in culture

Most basic research on cancer concerns genetic changes in benign and malignant tumors. Yet evidence indicates that the majority of the mutations in tumors occur in the preneoplastic field stage of their development. That early stage is represented by grossly invisible, broad regions of "field cancerization" which have not, heretofore, been operationally analyzed in cell culture. Conditions are described for quantitating preneoplasia by increased saturation density followed by progression to transformation. These parameters are driven by Darwinian selection of spontaneously occurring, cumulative mutations, in accordance with recent genomic analyses of human cancer, just as it is in the evolution of species. The cell culture model will allow correlation of the preneoplastic increases in saturation density with genetic changes, and development of methods for demarcating fields during surgery so that they can be excised along with the tumor, thereby reducing the possibility of recurrence at the site.     

Contribution of myeloid-derived suppressor cells to tumor-induced immune suppression, angiogenesis, invasion and metastasis

Growing evidence suggests that myeloid-derived suppressor cells (MDSCs), which have been named "immature myeloid cells" or "myeloid suppressor cells" (MSCs), play a critical role during the progression of cancer in tumor-bearing mice and cancer patients. As their name implies, these cells are derived from bone marrow and have a tremendous potential to suppress immune responses. Recent studies indicated that these cells also have a crucial role in tumor progression. MDSCs can directly incorporate into tumor endothelium.They secret many pro-angiogenic factors as well. In addition, they play an essential role in cancer invasion and metastasis through inducing the production of matrix metalloproteinases (MMPs), chemoattractants and creating a pre-metastatic environment. Increasing evidence supports the idea that cancer stem cells (CSCs) are responsible for tumorigenesis, resistance to therapies, invasion and metastasis.Here, we hypothesize that CSCs may "hijack" MDSCs for use as alternative niche cells, leading to the maintenance of stemness and enhanced chemo- and radio-therapy resistance. The countermeasure that directly targets to MDSCs may be useful for against angiogenesis and preventing cancer from invasion and metastasis. Therefore, the study of MDSCs is important to understand tumor progression and to enhance the therapeutic efficacy against cancer.     

基因突变在结直肠癌诊疗及预后中的研究进展

结直肠癌是常见的恶性肿瘤之一,其发病率居全球恶性肿瘤发病率的第三位,死亡率呈逐年上升趋势。中国已成为全球结直肠癌每年新发病例数和死亡病例数最多的国家。对结直肠癌基因突变状态的识别以及对结直肠癌发生发展过程进行精确分类,可实现对患者进行个性化精准治疗的目的,而精准治疗的实现有赖于基因测序技术。目前,二代测序技术(Next generation sequencing,NGS)结合基因捕获技术,集中对研究者感兴趣的候选基因或外显子进行平行测序,极大拓展了对肿瘤特征基因的认识,为发展新的治疗手段和治疗策略奠定了基础。整合癌症基因组数据库IntOgen已明确72个结直肠癌驱动突变基因,包括“TP53”、“KRAS”、“PIK3CA”等;癌基因数据库Cancer Gene Census目前收录的结直肠癌突变基因有59个,包括原癌基因“BRAF”、抑癌基因“SMAD4”等;在线人类孟德尔遗传OMIM数据库已收录55个与结直肠癌相关的体细胞突变基因,包括“SRC”、“APC”等。本文通过26篇国内外文献,对结直肠癌基因突变检测的共识基因进行综述,并总结了与结直肠癌患者临床诊断、分型、预后、治疗等临床病理特征相关的突变基因标志物。     

Breast cancer, a stem cell disease

Breast cancer is a first magnitude problem of public health worldwide. There is increasing evidence that this cancer is originated in and maintained by a small population of undifferentiated cells with self-renewal properties. This small population generates a more differentiated pool of cells which represents the main mass of the tumor, resembling the hierarchical tissue organization of the normal breast. These cancer stem cells seem to share a similar phenotype with their normal counterparts but they display dysfunctional patterns of proliferation and differentiation, and they no longer respond to normal physiological controls that ensure a balanced cellular turnover. The origin of these cancer stem cells is controversial; it is not well known if they are originated from normal stem cells or from more differentiated progenitors where a de novo stem cell program is activated by the oncogenic insult. Here we review the origin of breast cancer stem cells and their role in the pathogenesis of cancer development, together with their implications in breast cancer progression, treatment and prognosis.     

Ablation of Akt2 induces autophagy through cell cycle arrest, the downregulation of p70S6K, and the deregulation of mitochondria in MDA-MB231 cells

Background

Akt/PKB is a promising anticancer therapeutic target, since abnormally elevated Akt activity is directly correlated to tumor development, progression, poor prognosis and resistance to cancer therapies. Currently, the unique role of each Akt isoform and their relevance to human breast cancer are poorly understood.

Methodology/Principal Findings

We previously found that Akt1, 2 and 3 are localized at specific subcellular compartments (the cytoplasm, mitochondria and nucleus, respectively), raising the possibility that each isoform may have unique functions and employ different regulation mechanisms. By systematically studying Akt-ablated MDA-MB231 breast cancer cells with isoform-specific siRNA, we here show that Akt2 is the most relevant isoform to cell proliferation and survival in our cancer model. Prolonged ablation of Akt2 with siRNA resulted in cell-cycle arrest in G0/G1 by downregulating Cdk2 and cyclin D, and upregulating p27. The analysis of the Akt downstream signaling pathways suggested that Akt2 specifically targets and activates the p70S6K signaling pathway. We also found that Akt2 ablation initially resulted in an increase in the mitochondrial volume concomitantly with the upregulation of PGC-1α, a regulator of mitochondrial biogenesis. Prolonged ablation of Akt2, but not Akt1 or Akt3, eventually led to cell death by autophagy of the mitochondria (i.e., mitophagy).

Conclusions/Significance

Collectively, our data demonstrates that Akt2 augments cell proliferation by facilitating cell cycle progression through the upregulation of the cell cycle engine, and protects a cell from pathological autophagy by modulating mitochondrial homeostasis. Our data, thus, raises the possibility that Akt2 can be an effective anticancer target for the control of (breast) cancer.     

On the Role of the Microenvironment in Mammary Gland Development and Cancer

Knowledge of the specific microenvironmental cues involved at the earliest stages of breast cancer development is currently limited.Breast cancer can be viewed as a disease of defective development, wherein the processes that guide growth and morphogenesis of the mammary gland are inappropriately activated during tumor proliferation and invasion. Research over the last couple of decades, reviewed by Polyak and Kalluri (2011), has defined some of the key microenvironmental signals that underlie both tissue development and disease progression. Meticulous investigation of animal models has revealed how processes controlling mammary gland development during puberty, pregnancy, lactation, and involution become activated in cancer. For example, some of the same stromally produced matrix metalloproteinases (MMPs) that facilitate outgrowth and branching morphogenesis as the glandular epithelium grows into the fat pad during puberty are also involved in the penetration of the basement membrane by the developing cancer (Wiseman and Werb 2002). In parallel, development of physiologically relevant 3D culture systems has enabled identification of specific biochemical and biophysical signals, required for maintenance of normal tissue structure, that become dysregulated as tumors grow. For example, recent studies have found that increasing the stiffness and collagen composition of the extracellular matrix can cause normal mammary epithelial structures to acquire invasive characteristics (Egeblad et al. 2010).Although models for studying the impact of the microenvironment on mammary tissue behavior have become increasingly sophisticated, a significant impediment in elucidating the most important changes in breast cancer development is a limited understanding of the specific microenvironmental cues involved at the earliest stages of disease development. The most commonly hypothesized model of breast cancer development posits an evolution through incremental steps of accumulating cellular abnormalities from normal epithelium through proliferative disease without atypia (PDWA), atypical hyperplasia, ductal carcinoma in situ (DCIS), and then invasive breast cancer (Santen and Mansel 2005). This model is supported by epidemiologic studies that show a stepwise increase in relative risk (RR) of subsequent development of invasive breast cancer from PDWA (RR = 2) to atypical hyperplasia (RR = 4) to DCIS (RR = 10) (Arpino et al. 2005). What are the critical factors that influence whether a premalignant lesion will develop into invasive cancer? Although seminal work by Polyak and coworkers (Hu et al. 2005), as well as other researchers, has identified some of the specific characteristics associated with subsequent disease progression for patients with DCIS, such lesions have already accumulated a broad array of genetic and structural abnormalities. Investigations of yet earlier stages of disease may help us to identify which alterations are the key drivers of progression to malignancy. This information could lead to entirely novel approaches targeting these processes, toward the ultimate goal of prevention of breast cancer formation.     

Surfing the big WAVE: Insights into the role of WAVE3 as a driving force in cancer progression and metastasis

WAVE3 belongs to the WASP/WAVE family of actin cytoskeleton remodeling proteins. These proteins are known to be involved in several biological functions ranging from controlling cell shape and movement, to being closely associated with pathological conditions such as cancer progression and metastasis. Last decade has seen an explosion in the literature reporting significant scientific advances on the molecular mechanisms whereby the WASP/WAVE proteins are regulated both in normal physiological as well as pathological conditions.The purpose of this review is to present the major findings pertaining to how WAVE3 has become a critical player in the regulation of signaling pathways involved in cancer progression and metastasis. The review will conclude with suggesting options for the potential use of WAVE3 as a therapeutic target to prevent the progression of cancer to the lethal stage that is the metastatic disease.     

Risques prostatiques de la testostérone : nouveau retour du balancier?

Since the 1940??s, testosterone (T) is deemed dangerous to the prostate, though without solid evidence. Longitudinal studies do not show association between T levels and prostate cancer (PCa) incidence. To the contrary, aggressive PCa cases are associated with low T levels. Randomized placebo controlled trials of T therapy do not show any increase in PCa incidence in the T groups. These reassuring data have led some doctors to prescribe T replacement therapy to men with prostatic intraepithelial neoplasia, or previously treated for a low grade PCa, or under active surveillance for such untreated cancer without showing a high risk of progression or recurrence of cancer with this treatment. There is however no doubt that normal prostate and PCa, at least in its advanced forms, are made with androgen-dependent tissues. These apparent contradictions might be explained, besides the possibility of a very low diffusion of circulating T in the prostate, by the hypothesis of a saturation of the prostate androgen receptors from very low levels of circulating T, close to castration levels, explaining that an increase in T beyond this level cannot stimulate the prostate tissue. Some recent reports of PCa progression under T therapy, sometimes persisting despite T withdrawal, show that the reassuring results of the previous studies cannot be generalized. Objective data also suggest that the saturation level of the prostate androgen receptor is actually close to the lower limit of the normal T range. We must remain cautious about expanding the indication of T therapy in men with a history of PCa. Only large-scale, randomized, double-blind placebo controlled trials, will provide reliable information on the prostatic risks of such a treatment.     

Junctions gone bad: claudins and loss of the barrier in cancer

The tight junctions (TJs) of epithelia are responsible for regulating the "fence and gate" function of polarized epithelial cells. It is now well-established that dysregulation of these functions contributes to initiation and progression of cancer. Recently, it has become clear that the Claudins, members of a large family of 27 closely related transmembrane proteins, play a crucial role in formation, integrity and function of TJs, the epithelial permeability barrier and epithelial polarization. A growing body of data indicates that Claudin expression is altered in numerous epithelial cancers in a stage- and tumor-specific manner. While a single universal mechanism is still lacking, accumulating evidence supports a role for epigenetic regulation of Claudin expression in tumorgenesis, with concomitant alterations in barrier function. We review here new insights and challenges in understanding Claudin function in normal physiology and cancer.     

Prevention of prostate cancer through custom tailoring of chemopreventive regimen

One practical way to control cancer is through chemoprevention, which refers to the administration of synthetic or naturally occurring agents to block, reverse or delay the process of carcinogenesis. For a variety of reasons, the most important of which is human acceptance, for chemopreventive intervention naturally occurring diet-based agents are preferred over synthetic agents. For a long time, the prevailing mantra of cancer chemoprevention has been: "Find effective agents with acceptable or no toxicity and use them in preventing cancer in relatively healthy people or individuals at high risk for developing cancer". In pursuing this goal many naturally occurring phytochemicals capable of affording protection against carcinogenesis in preclinical settings in experimental animals have been described. However, clinical trials of single agents have yielded disappointing results. Since carcinogenesis is a multistage phenomenon in which many normal cellular pathways become aberrant, it is unlikely that one agent could prove effective in preventing cancer. This review underscores the need to build an armamentarium of naturally occurring chemopreventive substances that could prevent or slow down the development and progression of prostate cancer. Thus, the new effective approach for cancer prevention "building a customized mechanism-based chemoprevention cocktail of naturally occurring substances" is advocated.     

Defining a molecularly normal colon.

As techniques evolve that allow molecular characterization of disease processes such as cancer, definition of "normal" at a molecular level becomes increasingly important. Increasingly large numbers of mutations are found at the genomic level, but whether all of those mutations contribute to the malignant state of a carcinoma cell is not clear. Without knowledge of what constitutes normality on the proteomic level in an organ or cell, we cannot determine what genomic changes are physiologically important. Traditionally, colon cancer is identified and classified by histological criteria. Margins of the colon are defined as "grossly uninvolved" when the histology is indistinguishable from that of normal (free from disease) colon. By using molecular pathology techniques and working backward from colon adenocarcinoma to hypoplastic polyps to presumably normal mucosa, we defined some of those protein differences. Our results may provide a molecular basis for identifying tumor formation and progression in situ.(J Histochem Cytochem 49:667-668, 2001)     

Quantitative Proteomic Analysis of Oral Brush Biopsies Identifies Secretory Leukocyte Protease Inhibitor as a Promising,Mechanism-Based Oral Cancer Biomarker

A decrease in the almost fifty percent mortality rate from oral cancer is needed urgently. Improvements in early diagnosis and more effective preventive treatments could affect such a decrease. Towards this end, we undertook for the first time an in-depth mass spectrometry-based quantitative shotgun proteomics study of non-invasively collected oral brush biopsies. Proteins isolated from brush biopsies from healthy normal tissue, oral premalignant lesion tissue (OPMLs), oral squamous cell carcinoma (OSCC) and matched control tissue were compared. In replicated proteomic datasets, the secretory leukocyte protease inhibitor (SLPI) protein stood out based on its decrease in abundance in both OPML and OSCC lesion tissues compared to healthy normal tissue. Western blotting in additional brushed biopsy samples confirmed a trend of gradual decreasing SLPI abundance between healthy normal and OPML tissue, with a larger decrease in OSCC lesion tissue. A similar SLPI decrease was observed in-vitro comparing model OPML and OSCC cell lines. In addition, exfoliated oral cells in patients’ whole saliva showed a loss of SLPI correlated with oral cancer progression. These results, combined with proteomics data indicating a decrease in SLPI in matched healthy control tissue from OSCC patients compared to tissue from healthy normal tissue, suggested a systemic decrease of SLPI in oral cells correlated with oral cancer development. Finally, in-vitro experiments showed that treatment with SLPI significantly decreased NF-kB activity in an OPML cell line. The findings indicate anti-inflammatory activity in OPML, supporting a mechanistic role of SLPI in OSCC progression and suggesting its potential for preventative treatment of at-risk oral lesions. Collectively, our results show for the first time the potential for SLPI as a mechanism-based, non-invasive biomarker of oral cancer progression with potential in preventive treatment.