The cells are so small that we can only see them under a microscope. Cells group together to make up the tissues and organs of our bodies. They are very similar. But vary in some ways because body organs do very different things. For example, nerves and muscles do different things, so the cells have different structures. There are more than types of cancer and we can classify cancers according to where they start in the body, such as breast cancer or lung cancer. We can also group cancer according to the type of cell they start in.
There are 5 main groups. These are:. Carcinomas are the most common type of cancer. There are different types of epithelial cells and these can develop into different types of carcinoma. These include:. Squamous cell carcinoma starts in squamous cells.
These are the flat, surface covering cells found in areas such as the skin or the lining of the throat or food pipe oesophagus. Adenocarcinomas start in glandular cells called adenomatous cells. Glandular cells produce fluids to keep tissues moist. Transitional cells are cells that can stretch as an organ expands. We will discuss several new technologies that have use in detecting the most common carcinomas that derive from the epithelium of the skin, gastrointestinal and urogenital tracts, and bronchoalveoli.
Publication types Research Support, N. Gov't Review. Future Oncol. Download references. We would like to thank Dr. Ursula Hille, Hannover, Dr. Dirk Grothuesmann, Hannover, and Dr. Reinhard von Wasielewski, Hannover, for providing the tissue specimen. We are indebted to Prof. Nalapareddy Kodandaramireddy, Ulm, for the telomerase trap assay. You can also search for this author in PubMed Google Scholar. Correspondence to Ralf Hass. RH conceived and designed the study, generated the primary cells from the tumor tissues, carried out the immune fluorescence analysis, aging studies and the chemotherapeutic assay and wrote the manuscript.
CB carried out the cell surface marker analysis and contributed to the chemotherapeutic assay and statistical analysis. The authors read and approved the final manuscript. This article is published under license to BioMed Central Ltd. Reprints and Permissions. Hass, R. Characterization of human breast cancer epithelial cells HBCEC derived from long term cultured biopsies.
J Exp Clin Cancer Res 28, Download citation. Received : 15 July Accepted : 14 September Published : 14 September Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article.
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Download PDF. Abstract Introduction For a more individualized therapeutic approach we explored a protease-free method to culture primary cells from breast cancer biopsies.
Methods and Results Tumor tissue from breast cancer patients after surgery was cultured ex vivo without enzymatic digestion for more than one year and revealed the continuous outgrowth of adherent and proliferating primary cell populations.
Conclusion The protease-free outgrowth of primary HBCEC offers a patient-specific approach to optimize an individually-designed cancer therapy.
Background Individual primary cultures of tissue biopsies from breast cancer patients represent an alternative model for in vitro studies as compared to the use of immortalized breast cancer cell lines. Materials and methods Individual mammary tumor-derived cell cultures Small tissue pieces from 8 different breast cancer patients were collected during surgery and pathologically characterized as ductal carcinomas, respectively.
Normal human mammary epithelial cell cultures Primary cultures of normal human mammary epithelial cells HMEC were isolated from a 50 year old caucasian female and commercially provided by BioWhittaker Inc. Electron microscopy The mammary tumor tissues were cultured on appropriate microscope slides for scanning SEM and transmission electron microscopy TEM , respectively. Results The ex vivo culture of tumor tissue from breast cancer patients after surgery was associated with the outgrowth of adherent human breast cancer epithelial-like cells HBCEC and demonstrated a massive extension of cytoplasmic protrusions similar to the morphology as described for normal human mammary epithelial cells HMEC Fig.
Figure 1. Full size image. Figure 2. Figure 3. Figure 4. Figure 5. Discussion Protease digestion-free ex vivo culture of human breast cancer epithelial cells HBCEC from breast cancer tissue revealed a cell morphology which resembled normal human mammary epithelial cells HMEC. Conclusion Taken together, the morphological evaluation and cytokeratin expression revealed epithelial-like cells in the primary tumor tissue-derived cultures without a significant contamination of other cell types.
References 1. Article Google Scholar 2. Article Google Scholar 4. CAS Google Scholar 5. Google Scholar 7. Like ZO-1, MUPP-1 also links to the membrane-associated JAM-1 protein suggesting a pivotal role of MUPP-1 as multivalent scaffolding protein to recruit several other proteins and participate in the regulation of epithelial cell growth and differentiation.
They consist of over 80 members, among which, E-cadherin is primarily expressed in epithelia. Specific adhesive binding is conferred by the extracellular portion that serves as a template and engages an identical molecule on the surface of neighboring cells.
The four nectins till now identified, are members of the immunoglobulin Ig superfamily of calcium-independent cell adhesion molecules and are characterized by an extracellular domain with three IgG-like loops, a single transmembrane region, and a cytoplasmic tail that binds to afadin through a C-terminal PDZ binding domain Nectin-1, nectin-2, and nectin-3 are ubiquitously expressed in a variety of cells including epithelial cells, neurons, and fibroblasts whereas nectin-4 is mainly expressed in the placenta Experimental evidence indicates that similar to cadherins, nectins are thought to form cis-homodimers and trans-homodimers with similar molecules of adjacent cells 51 Figure 2.
A key event in the establishment of cell-cell junctional complex is the polarization of epithelial cells. In fact, upon establishing a cell-cell contact and before forming AJs and TJs, epithelial cells must reorganize their cytoskeleton and polarize trafficking routes However, to correctly assemble and localize the junctional complex components, a set of evolutionarily conserved polarity proteins that cross-regulate one each other and interplay with cytoskeleton structures is required Figure 3.
Epithelial cells are polarized along their apicobasal axis, due to the action of three polarity complexes. SCRIB complex is localized to the basolateral region, antagonizes the function of the PAR complex and promotes basal membrane identity. The PAR complex was initially identified in Caenorhabditis elegans mutants partitioning-defective as involved in the regulation of the anterior-posterior cell polarity of the one-cell embryo PAR complex is localized to the apical junction domain and significant evidence indicates that it has a critical role in TJ formation and epithelial polarization 55 , The CRB and SCRIB complexes were initially identified in the fruit fly Drosophila melanogaster , as responsible for epithelial defects: fly embryos the lack Crumbs and stardust proteins fail to form a zonula adherens the Drosophila homolog of TJ and display a disruption of the apico-basal polarity In mammals, Crumbs3, one of the three mammalian homologs of Crumbs protein, is localized to the apical membrane where it forms a complex with Pals1 the mammalian homolog of Drosophila stardust protein , and Patj Pals-associated tight junction protein the mammalian homolog of Drosophila Dlt Disc lost In fact, phosphorylated Lgl is unable to localize to the membrane and is inactive Based on the work mainly performed in Drosophila and Caenorhabditis elegans , the formation of apical polarity seems to be a hierarchical and interactive process in which PAR and CRB complexes cooperate in establishing the apical domain and in the assembly of TJs, whereas SCRIB complex should define the basolateral plasma membrane domain.
Experimental evidence indicates that, in mammals, the earliest stage of junction biogenesis consists of the trans-interaction of nectins that recruit E-cadherin and JAMs to the apical side of AJs Experimental evidence indicates that the recruitment of aPKC by Par6 and the following phosphorylation of Par3, that allows the activation of the ternary complex, is a critical step for the maturation of the junctional complex into distinct TJ and AJs.
In addition to their role in establishing and maintaining a correct epithelial phenotype, several components of the apical junctional complex have also been found able to actively influence gene expression.
In fact, accumulating evidence indicated that some nontransmembrane proteins involved in the formation of the apical junctional complex can shuttle between plasma membrane and nucleus where they participate in the formation of chromatin-associated complexes and hence in the control of gene transcription.
In fact, if the apical junctional complex is intact, some apical proteins move into the nucleus and participate in the transcription repression of the genes that have to be silenced in order to maintain a differentiated phenotype. Conversely, when apical junctional complex is disrupted certain transcription regulators, normally compartmentalized at cell-cell junctions by apical polarity proteins, are free to move into the nucleus where they induce apical proteins to switch from nuclear repressors to nuclear promoters.
Such an hypothesis has recently been supported by the finding that nuclear over-expression of symplekin, a transcriptional regulation normally localized at TJs, promotes tumorigenesis in the human colon and that the regulation of claudin-2 expression is instrumental in this effect Disruption of intercellular junctions and alterations in cell polarity are specific hallmarks of epithelial cancer cells.
In fact, most human tumors arising in epithelial tissues, gradually lose their polarized morphology and acquire a more peculiar mesenchymal phenotype according to a process termed epithelial-mesenchymal transition EMT Physiologically associated with embryogenesis and wound healing in the adult, EMT is a process characterized by the loss of cell-cell adhesion and apicobasal cell polarity and the concomitant acquisition of a fibroblastoid motile phenotype.
When pathologically activated during tumor development, EMT provides cells with ability to escape from the primary tumor mass and to migrate to distant region where they metastasize Disruption of cell-cell adhesion is principally due to the disassembly of the junctional complex that may be induced by a direct modification of the any junctional components transmembrane and cytoplasmic proteins or by indirect effects through the actin cytoskeleton that controls the integrity of TJs and AJs.
In particular, alterations in the structure and function of TJs have been reported in adenocarcinomas of various organs, including colon and breast 77 , 78 , whereas absent or defective TJs have also been associated with the development of the neoplastic phenotype in endometrial cells TJs dysfunction has also been described in inflammatory processes that end up in cancerous transformation. Interestingly, it has also been shown that the transforming potential of some oncoproteins, encoded by human adenovirus, papillomavirus HPV , T-cell leukaemia virus type, depends in part on their ability to interact with TJ-associated proteins of epithelial cells As previously illustrated, alterations in some apical proteins and transcription regulators compartmentalization, due to TJs and AJs disassembly, may have a dramatic impact on gene transcription with the switch in the apical proteins activity from nuclear repressors to nuclear promoters as supported by the observation that ZO-1 protein is found at the plasma membrane in noninvasive cells whereas it is located in the nucleus of invasive cells Also transmembrane and cytoplasmic proteins with at least a PDZ domain have been found target of some oncoproteins including HPV E6 protein, one of the major oncogenic determinants of the sexually transmitted HPV, the primary etiologic agent of cervical cancers.
Through such a binding E6 targets these proteins as well as the Dlg and Scrib molecules to ubiquitin-mediated degradation in the proteosome 89 , 90 , The first hint that polarity proteins might contribute to cancer was provided by experiments in Drosophila which showed that knockout of any member of the Scribble complex results in the loss of apicobasal cell polarity, mislocalization of apical junctions and failure to form the zonula adherens, and neoplastic overgrowth of imaginal discs, the ectodermal structure from which originate epithelia, that lead to death at the larval stage suggesting for these proteins an oncosuppressive key function 92 , Also in mammals, several reports describe a strong correlation between decreased expression of mammalian homologues of Scrib, Lgl and Dlg and tumor progression.
Mice lacking Lgl1, one of the two Lgl homologues, show severe brain dysplasia, accompanied by loss of cell polarity in neuroepithelial cells 94 , whereas loss or aberrant localization of Lgl2 is associated with human gastric epithelial dysplasia and adenocarcinomas In addition, as already described, ubiquitin-mediated degradation of Dlg and Scrib proteins may contribute to the development of the HPV-induced cervical carcinoma 91 , Recent findings also implicate the PAR complex in human carcinogenesis.
Gene amplification and elevated activity of aPKC have been detected in ovarian, lung and colon cancer and correlated with a poor prognosis 99 , , As the members of PAR complex play a pivotal role in signaling pathways that control polarity and proliferation, PAR complex implication in human carcinogenesis is not surprising It has recently been demonstrated that after activation, the ErbB2 receptor binds directly to Par6 protein, leading to the competitive recruitment of aPKC and the disruption of the apicobasal polarity Also mutations in tumor suppressor proteins, such as von Hippel-Lindau protein VHL , may affect PAR complex efficiency and junctional complex assembly.
In fact, as demonstrated by Okuda et al , VHL, a tumor suppressor involved in the von Hippel-Lindau syndrome which leads to the development of hemagioblastoma, clear-cell renal carcinoma and pheochromocytomas, mediates ubiquitination of a variety of proteins, including activated aPKC, and it regulates the assembly of intercellular junctions.
Because VHL tumor suppressor simultaneously affects cell polarity and growth, inactivating mutations result in an abnormal AJs and TJs organization and cell proliferation as evident in VHL-negative cancer cells.
Due to their multiple links to cancer, many structural and regulatory components of the junctional complex may represent valuable tumor biomarkers.
Even though the acquisition of new insights is increasing, at present the largest body of clinical evidence derived from studies on E-cadherin expression. Such a downregulation of E-cadherin may occur as a consequence of gene mutation or epigenetic silencing. The prevalence of E-cadherin loss in non-invasive precursor lesions as lobular carcinomas in situ of the breast or pancreas adenomas highlights the importance of E-cadherin as a tumor and invasion suppressor and it suggests E-cadherin loss as a critical step in the transition from adenoma to carcinoma.
Also the expression of occludin, one of the major transmembrane components of TJs, has been found decreased with disease progression. For example, moderately and poorly differentiated gastric carcinomas show a reduced occludin mRNA and corresponding protein level when compared to well differentiated ones Similarly, loss of occludin has been found in human breast cancer , in unpolarized prostate cancer cells of Gleason grades 4 and 5 , and in grades 2 and 3 endometrioid carcinoma with respect to grade 1 Conversely, in other cancers such as papillary thyroid, oral squamous cell carcinoma, ovarian, colon, melanoma and gastric , , , , , , overexpression of claudins has been associated with a more aggressive phenotype.
With regards to the clinical relevance of cytoplasmic proteins, such as ZOs and JAMs proteins, several studies have reported that their reduced expression correlates with dedifferentiation in tumors arising from various compartments of the biliary tract and progression of clear cell renal carcinoma or endometrial cancer , , However, ZO-1, which is generally considered as a tumor suppressor, has unexpectedly been found overexpressed and associated with N-cadherin in melanoma , overexpressed and aberrantly localized in primary and metastatic pancreatic cancer , whereas JAM-A has been found overexpressed and positively correlated with poor prognosis in breast cancer patients About cell polarity complex components recent data provide evidence that aPKC is overexpressed in gastric cancer and associated with unfavorable prognosis In addition, in a very recent study, aPKC overexpression has been found associated with the loss of Lgl2, a component of the SCRIB polarity complex, in foveolar-type gastric dysplasia suggesting their combined evaluation useful to refine dysplasia diagnosis The immunohistochemical determination of Lgl2 expression has also provided to be useful in separating pancreatic intraepithelial neoplasia-3 and pancreatic ductal adenocarcinoma from lower-grade pancreatic intraepithelial neoplasias; in fact, while loss or abnormal Lgl2 expression is seen in pancreatic intraepithelial neoplasia-3 and adenocarcinoma, pancreatic intraepithelial neoplasia-1 and pancreatic intraepithelial neoplasia-2 express the protein in a normal-like basolateral fashion Similarly, the loss of Lgl1 has been associated with several solid tumors including melanoma, prostate, breast, colon, liver and lung cancer , , , In these cancers Lgl1 loss is generally associated with higher tumor grade, and is more pronounced in lymph node or distant metastases.
In fact, an emerging finding is the association of Dlg1 with HPV-induced gynecological malignancies: in later-stage and poorly differentiated tumors, cytoplasmic Dlg1 protein level increases while it decreases at the membrane sites of cell-cell adhesion , A similar trend of early-stage overexpression and mislocalization has been described in colon carcinogenesis: in adenomatous polyps and well- and moderately differentiated adenocarcinomas, Dlg1 protein level increased but become more diffuse with an increase cytoplasmic staining suggesting its potential use as selective biomarker.
Similarly even though preliminary, the evidence that alterations in Scrib protein expression and localization are associated with some cancer of epithelial origin including endometrial, cervical and colorectal neoplasias , In particular in the former, Scrib protein alterations have been found associated with clinical stage, histopathological differentiation, and lymph node metastasis whereas in cervical carcinoma the histochemical analysis showed a dramatic decrease in the expression of Scrib with the progression of disease from normal uterine cervical tissues to invasive cervical cancers through the precursor lesions While no clear evidence of a direct link between CRB complex components and tumor features and clinical outcome, it has now emerged, Par6 protein, a PAR complex component, has recently been found overexpressed in breast cancer-derived cell lines and in both precancerous breast lesions and advanced primary human breast cancers, especially in estrogen receptor-positive ones Although, as reported above, several polarity and junctional complex components have been found singly associated with initiation or progression in many cancers of epithelial origin, an integrated picture of the mechanisms controlling their expression and activity during cancer development is lacking.
To this aim, novel approaches such as gene expression profile analysis are needed to investigate the associations between the expression of genes coding for cell polarity and cell-cell adhesion determinants and the biologic features of preneoplastic and neoplastic lesions.
In such a perspective, for example, we have investigated whether, with respect to normal tissue, epithelial or mixed malignant pleural mesothelioma MPM were associated with specific patterns of expression of a selected set of genes related to EMT and cell polarity and adhesion Using active and passive Principal Components Analysis-based biplots, to visualize specific patterns of expression for epithelial and mixed MPMs, we found that epithelial MPMs, mixed MPMs and normal tissues were characterized by different patterns of expression of genes contributing to a better characterization of MPM histologies, thus suggesting the possibility of using gene expression profile analysis in refining the morphological diagnosis also in other controversial pathological situations as for example preneoplastic lesions.
Blocking cell proliferation in neoplasias and preventing EMT in preneoplastic lesions eventually restoring normal epithelial morphology represent the main goal of differentiation therapy. Several attempts, targeting cell polarity and adhesion components, have been made at experimental level with interesting and promising results. For example, it has been observed that, in suspension 3D breast tumor spheroids, the retrovirally-induced reexpression of claudin-1, downregulated or completely lost in breast cancer cells in vitro , resulted in plasma membrane homing of the protein and reconstitution of paracellular flux Similarly, in several cancer cell lines, the treatment with demethylators and histone deacetylase inhibitors or retinoids was able to reexpress occludin silenced by CpG island hypermethylation on its promoter region with a decreased cellular invasiveness and motility, thereby abrogating the metastatic potency of cancer cells Conversely, as regard to claudins which appear overexpressed in tumors, the use of siRNA to silence gene expression has provided a significant reduction in cell proliferation, reduction in tumor growth and a significant increase in the number of apoptotic cells A negative control of claudins overexpression has also been achieved using monoclonal antibody against specific members of the family and promising results have been obtained in pancreatic and ovarian cancers , The use of monoclonal antibodies has also been applied to inhibit the activity of JAM proteins and in particular to block the proangiogenic activity of JAM-3, another component of TJs that in tumor cells mediates the homophilic interaction with endothelial cells.
In a murine model of lung carcinoma, monoclonal antibody against JAM-3 was able to inhibit the growth of lung pulmonary tumor grafts by reducing tumor vasculature In addition to the immunotherapeutic strategy, the potential of claudins as targets for cancer therapy has been highlighted by the observation that treatment with Clostridium perfringens enterotoxin CPE elicits a rapid and specific cytolysis of breast, ovarian, pancreatic and prostate carcinoma cells.
This toxin, responsible for the gastrointestinal symptoms associated with Clostridium perfringens food poisoning, is released into the intestinal lumen where it binds specifically to claudin-3 and -4 present in the intestinal epithelial.
This triggers the formation of a large multiprotein membrane pore that ultimately results in cell lysis. Since claudin-3 and -4 are overexpressed in numerous carcinomas, this condition represents a unique opportunity for innovative therapy using CPE , In particular, Par6 protein appears a promising target both in early and late stage of breast cancers whereas aPKC, as well as being a new prognostic indicator, has been proposed as a novel therapeutic target for the treatment of gastric cancer Increasing evidence clearly shows that the loss of apico-basal polarity and changes in cellular junctions can be initiating events in tumor formation and that they are hallmark of malignant transformation.
Although in recent years there has been a significant advance regarding our understanding of the physiologic mechanisms governing cell polarity, the exact sequence of events leading to cell polarity dysregulation are still being uncovered whereas it is clear that the expression of genes coding for core polarity and junctional adhesion components can be directly or indirectly transcriptionally regulated by several factors including growth factors, oncogene products, tumor suppressors and EMT inducers.
Of particular interest, the emerging relationship among EMT, cell polarity and stem cell phenotype based on the observation that the proteins regulating cell polarity also have an important function in asymmetric cell division, a critical event that guarantees the two essential properties of stem cells: self-renewal and differentiation In fact, studies in Drosophila have shown that the asymmetric localization of cell-fate determinants is controlled by PAR and SCRIB complexes and that mutations in their components provoke defects in asymmetric stem cell division which finally results in tumor development 93 , Also in adult somatic stem cells, which play a central role in epithelial homeostasis, it is thought that polarity is particularly important with respect to fate decisions on stem cell division and that the failure in establishing or regulating stem cell polarity might result in neoplastic transformation That taking into consideration also the recently proposed link between EMT activation and the acquisition by tumor cells of a stem-like phenotype Interfering with the signaling pathways that promote the loss of epithelial integrity may be one of the most promising avenues for the development of new therapeutic strategies to impair tumor progression and to revert preneoplastic lesion toward a more differentiated phenotype.
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