Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0006142 (breast cancer)
 160,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Osteopontin (OPN) is a secreted calcium-binding phosphoprotein produced in a variety of normal and pathological contexts, including tissue mineralization and cancer. OPN contains a conserved RGD (arg-gly-asp) amino acid sequence that has been implicated in binding of OPN to cell surface integrins. To determine whether the RGD sequence in OPN is required for adhesive and chemotactic functions, we have introduced two site-directed mutations in the RGD site of the mouse OPN cDNA, in which the RGD sequence was either deleted or mutated to RGE (arg-gly-glu). In order to test the effect of these mutations on OPN function, we expressed control and mutated mouse OPN in E. coli as recombinant glutathione-S-transferase (GST)-OPN fusion proteins. Control mouse GST-OPN was functional in cell adhesion assays, supporting attachment and spreading of mouse (malignant PAP2 ras-transformed NIH 3T3, and, to a lesser extent, normal NIH 3T3 fibroblasts) and human (MDA-MB-435 breast cancer, and normal gingival fibroblast) cells. In contrast, neither of the RGD-mutated OPN proteins ("delRGD" or "RGE") supported adhesion of any of the cell lines, even when used at high concentrations or for long assay times. GRGDS (gly-arg-gly-asp-ser) peptides inhibited cell adhesion to intact GST-OPN, as well as to fibronectin and vitronectin. In chemotaxis assays, GST-OPN promoted directed cell migration of both malignant (PAP2, MDA-MB-435) and normal (gingival fibroblast, and NIH 3T3) cells, while RGD-mutated OPN proteins did not. Together these results suggest that the conserved RGD sequence in OPN is required for the majority of the protein's cell attachment and migration-stimulating functions.
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PMID:Site-directed mutagenesis of the arginine-glycine-aspartic acid sequence in osteopontin destroys cell adhesion and migration functions. 754 53

Microcalcifications are a common phenomenon associated with breast cancer and are often the only mammographic sign of a malignant breast disease. Although microcalcifications are not restricted to breast cancer and can be also associated with benign lesions, it is noteworthy that they are composed exclusively of hydroxyapatite in breast carcinoma. Hydroxyapatite is the bone-associated phosphocalcic crystal the deposition of which in bone tissue requires the coordinated expression of several molecules such as osteonectin (OSN) and osteopontin (OPN), synthesized by cells of the osteoblastic lineage. In this study, we evaluated the expression of these two bone matrix proteins, using an immunoperoxidase technique and specific antibodies, in 79 breast lesions including 28 benign and 51 cancerous specimens. We found that normal mammary tissue associated with the lesions examined expressed generally undetectable or lightly detectable (0 or 1+) amounts of OSN and OPN (92 and 81%, respectively). Benign breast lesions, including fibroadenoma and fibrocystic dysplasia, were generally weakly stained (0 or 1+) with both anti-OSN and anti-OPN antibodies (96.4 and 60.7%, respectively). Interestingly, the majority of both in situ and invasive breast carcinoma lesions showed a strong expression (2+ or 3+) for OSN or OPN (74.5 and 84.3%, respectively). High expression of these two bone matrix proteins was associated with frequent microcalcification deposition in the lesion. This study is the first extensive study of OSN and OPN expression in mammary cancers. Our data suggest that OSN and OPN could play a role in the formation of ectopic microcalcifications often associated with breast cancer. It is also tempting to speculate that the expression of these two glycoproteins by breast cancer cells play a role in the preferred bone homing of breast metastases.
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PMID:Increased expression of osteonectin and osteopontin, two bone matrix proteins, in human breast cancer. 785 41

Osteopontin (OPN), a secreted phosphoprotein, has been implicated in various biological phenomena (e.g. bone development, sepsis, tumor progression, and metastasis). Its role in any context is poorly understood. OPN contains a conserved Gly-Arg-Gly-Asp-Ser (GRGDS) sequence, and binds to cells via integrin-mediated mechanisms. Using recombinant human osteopontin-glutathione S-transferase fusion protein and our improved hybridoma fusion partner (Sp2/mIL6), we raised murine monoclonal antibodies against osteopontin. We characterized two antibodies that recognize not only recombinant but also native human osteopontin. These antibodies do not cross-react with mouse osteopontin (recombinant protein or that secreted by ras-transformed NIH 3T3 cells), or bovine bone osteopontin, suggesting that they recognize epitopes unique to human OPN. One antibody specifically inhibited adhesion of MDA-MB-435 human breast cancer cells and ras-transformed NIH 3T3 cells to human osteopontin. This antibody failed to recognize osteopontin cleaved by thrombin, which cleaves adjacent to the cell binding domain. We previously showed that thrombin cleavage reduces osteopontin cell binding activity. Thus we postulate that this monoclonal antibody recognizes and interferes with the function of the RGD/thrombin cleavage region of human OPN.
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PMID:Inhibition of Arg-Gly-Asp (RGD)-mediated cell adhesion to osteopontin by a monoclonal antibody against osteopontin. 808 34

The rat mammary epithelial cell line, Rama 37, yields benign, non-metastasizing adenomatous tumours in syngeneic Furth-Wistar rats. Transfection of this stably diploid cell line with genomic DNA fragments from a human metastasizing breast cancer cell line yields cells which, when injected subcutaneously in syngeneic rats, give rise to secondary tumours in a number of the animals. From one such secondary lung tumour, a cell line was established designated Ca2-5-LT1. This cell line, when introduced into the syngeneic rat host, also showed the ability to metastasise. To determine key changes in gene expression that occur during the progression from Rama 37, the benign tumour-inducing cell line, to the metastatic derivative Ca2-5-LT1, a general method of subtractive hybridization has been employed. This procedure in conjunction with Northern blotting and nucleic acid sequencing has been used to identify mRNAs expressed differentially between the metastatic and nonmetastatic cell lines described above. So far, of the subtracted cDNAs that have been identified which represent differentially expressed mRNAs, a large proportion of these cDNAs corresponded to the mRNA for rat osteopontin (OPN). The mRNA for OPN was expressed at a ninefold higher level in the metastatic Ca2-5-LT1 cell line when compared to the nonmetastatic parental Rama 37 cell line. Rama 37 cells transfected with DNA from a human benign cell line failed to show elevated levels of OPN mRNA. Following transfection of Rama 37 cells with an expression-construct producing elevated levels of OPN, the newly-transfected cells, when introduced into the rat host, developed metastases in 55% of the animals that produced primary tumours. These experiments show that increasing the expression of OPN in a previously benign cell tine is sufficient to produce a metastatic phenotype in this particular rat mammary model.
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PMID:The identification of osteopontin as a metastasis-related gene product in a rodent mammary tumour model. 870 May 59

CD44 is a ubiquitous multistructural and multifunctional cells surface adhesion molecule involved in cell-cell and cell-matrix interactions. Twenty exons are involved in the genomic organization of this molecule. The first five and the last 5 exons are constant, whereas the 10 exons located between these regions are subjected to alternative splicing, resulting in the generation of a variable region. Differential utilization of the 10 variable region exons, as well as variations in N-glycosylation, O-glycosylation, and glycosaminoglycanation (by heparan sulfate or chondroitin sulfate), generate multiple isoforms (at least 20 are known) of different molecular sizes (85-230 kDa). The smallest CD44 molecule (85-95 kDa), which lacks the entire variable region, is standard CD44 (CD44s). As it is expressed mainly on cells of lymphohematopoietic origin, CD44s is also known as hematopoietic CD44 (CD44H). CD44s is a single-chain molecule composed of a distal extracellular domain (containing, the ligand-binding sites), a membrane-proximal region, a transmembrane-spanning domain, and a cytoplasmic tail. The molecular sequence (with the exception of the membrane-proximal region) displays high interspecies homology. After immunological activation, T lymphocytes and other leukocytes transiently upregulate CD44 isoforms expressing variant exons (designated CD44v). A CD44 isform containing the last 3 exon products of the variable region (CD44V8-10, also known as epithelial CD44 or CD44E), is preferentially expressed on epithelial cells. The longest CD44 isoform expressing in tandem eight exons of the variable region (CD44V3-10) was detected in keratinocytes. Hyaluronic acid (HA), an important component of the extracellular matrix (ECM), is the principal, but by no means the only, ligand of CD44. Other CD44 ligands include the ECM components collagen, fibronectin, laminin, and chondroitin sulfate. Mucosal addressin, serglycin, osteopontin, and the class II invariant chain (Ii) are additional, ECM-unrelated, ligands of the molecule. In many, but not in all cases, CD44 does not bind HA unless it is stimulated by phorbol esters, activated by agonistic anti-CD44 antibody, or deglycosylated (e.g., by tunicamycin). CD44 is a multifunctional receptor involved in cell-cell and cell-ECM interactions, cell traffic, lymph node homing, presentation of chemokines and growth factors to traveling cells, and transmission of growth signals. CD44 also participates in the uptake and intracellular degradation of HA, as well as in transmission of signals mediating hematopoiesis and apoptosis. Many cancer cell types as well as their metastases express high levels of CD44. Whereas some tumors, such as gliomas, exclusively express standard CD44, other neoplasms, including gastrointestinal cancer, bladder cancer, uterine cervical cancer, breast cancer and non-Hodgkin's lymphomas, also express CD44 variants. Hence CD44, particularly its variants, may be used as diagnostic or prognostic markers of at least some human malignant diseases. Furthermore, it has been shown in animal models that injection of reagents interfering with CD44-ligand interaction (e.g., CD44s- or CD44v-specific antibodies) inhibit local tumor growth and metastatic spread. These findings suggest that CD44 may confer a growth advantage on some neoplastic cells and, therefore, could be used as a target for cancer therapy. It is hoped that identification of CD44 variants expressed on cancer but not on normal cells will lead to the development of anti-CD44 reagents restricted to the neoplastic growth.
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PMID:CD44: structure, function, and association with the malignant process. 911 68

The skeleton is the privileged target of metastatic human breast cancer cells. Bone metastases are indeed found in virtually all advanced breast cancer patients and generate major morbidity. The high osteotropism of breast cancer cells suggests that they exhibit a selective affinity for mineralized tissues. The observation that mammary malignant cells are able to induce hydroxyapatite crystals deposition within the primary tumour suggests that they can generate a microenvironment that favors the crystallization of calcium and phosphate ions into the bone specific hydroxyapatite. Osteonectin (OSN), osteopontin (OPN) and bone sialoprotein (BSP), 3 bone matrix proteins involved in bone matrix mineralization, are expressed in human breast cancers. BSP, an RGD (Arg-Gly-Asp) containing phosphoprotein, initiates hydroxyapatite deposition and mediates attachment of osteoclast to the same crystals prior to their resorption. Detection of BSP at both the protein and the mRNA levels in human breast cancer and in human breast cancer cell lines (MCF-7, T47-D and MDA-MB 231) indicates that mammary malignant cells synthesize directly BSP rather than uptaking it from the serum. Interestingly, the level of BSP expression correlates with the development of bone metastases and with poor survival. These data suggest that the ectopic expression of bone matrix proteins could be involved in conferring osteotropic properties to circulating metastatic breast cancer cells. These observations open new alleys of investigation for the identification of the molecular mechanisms responsible for the genesis of bone metastases.
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PMID:Expression of bone matrix proteins in human breast cancer: potential roles in microcalcification formation and in the genesis of bone metastases. 918 Aug 54

Several human breast cancer cell lines express the calcitonin receptor (CTR), but this has not been demonstrated previously in clinical breast cancers. We examined 18 primary breast cancers by reverse transcription-PCR, for expression of CTR and of the bone proteins osteopontin (OPN) and bone sialoprotein (BSP). OPN and CTR were expressed by each of the tumours, and 7 (39%) additionally expressed an alternate form of CTR, whilst BSP was expressed by 13 tumours (72%). In situ hybridisation confirmed that expression of OPN and CTR was confined to the tumour cells. Expression of CTR, BSP and OPN may prove to be a useful marker for breast cancers, and their role in the homing of breast cancer cells to bone remains to be investigated.
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PMID:Calcitonin receptors, bone sialoprotein and osteopontin are expressed in primary breast cancers. 939 57

Evidence is mounting that changes in the ability of cancer cells to adhere to extracellular matrices play a decisive role in metastatic spread. The mechanism underlying the preference of breast cancer cells to metastasize to bone is, however, poorly understood. We investigated the expression and involvement of integrin adhesion receptors in the adhesion of breast cancer cells to bone matrix (constituents) in two in vitro attachment assays using RGD peptides and anti-integrin antibodies. Breast cancer cells adhered rapidly to extracellular bone matrix. Adhesion of most cells to vitronectin, fibronectin, thrombospondin, osteopontin, and the fairly bone-specific bone sialoprotein was inhibited by the 200 micrograms/ml GRGDS peptide. These data suggest that integrin adhesion receptors can modulate the attachment of breast cancer cells to bone matrix molecules. In accordance with these findings, we found that alpha 1-alpha 5(beta 1) and alpha v(beta 3) integrins were expressed by mammary carcinoma cells. Highly tumorigenic MDA-MB-231 cells, which form osteolytic metastases in vivo, expressed relatively high levels of alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1, alpha v beta 3 integrins, when compared to MCF-7, T47D, and ZR75-1 breast cancer cells. Addition of function-blocking anti-alpha 2 beta 1, -alpha 3 beta 1, -alpha 5 beta 1, and -alpha v beta 3 antibodies significantly inhibited the adhesion of MDA-MB-231 breast cancer cells to bone matrices. In conclusion, our data suggest a possible role for beta 1 and beta 3 integrin subfamily members in the establishment of skeletal metastases in advanced breast cancer patients. Clearly, functional evidence is required to understand the mechanisms involved in the development of skeletal metastases in breast cancer patients.
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PMID:Attachment characteristics and involvement of integrins in adhesion of breast cancer cell lines to extracellular bone matrix components. 942 5

Microcalcifications are often associated with both benign and malignant human breast lesions. Around 40% of mammary carcinoma present such ectopic mineralization and frequently, they are the only mammographic feature that indicate the presence of a tumoral lesion. Microcalcifications associated with breast cancer are usually composed of hydroxyapatite, the bone specific mineral. The mechanisms responsible for the formation of such crystals within breast malignant tissue have not been elucidated. A possible clue could be provided by the recent demonstration that breast cancer cells express several bone matrix proteins including osteonectin, osteopontin and bone sialoprotein (BSP). This latter phospho-protein is involved in the initiation of hydroxyapatite crystallisation and its expression in breast cancer has been associated to the presence of hydroxyapatite microcalcifications. We examined 10 human breast cancer lesions which were characterized by the presence of microcalcifications and high expression of BSP. Histological examination of the lesions suggested, in most of the cases, that the microcalcifications were breast cancer cells which became mineralized. Hydroxyapatite stained in blue by hematoxylin appears concentrated around single of associated cancer cells. Staining of these tissue sections with 4',6 diamidino-2-phenylindole which specifically labels DNA led us to demonstrate that the mineralizated structures contain cells. These data are the first direct demonstration that breast microcalcifications are fossils of cancer cells. The mechanisms for such a phenomenon remain to be demonstrated. We speculate that the high expression of BSP could create an appropriate microenvironment for the crystallisation of calcium and phosphate into hydroxyapatite.
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PMID:Evidence that breast cancer associated microcalcifications are mineralized malignant cells. 945 53

The metastatic spread of cancer is a little understood process, in part because it is difficult to model the entire process using experimental approaches in vitro. The ability to transfer DNA into non-metastatic mammary cells and to observe the induction of metastasis in vivo provides a means for identifying DNA sequences that are associated with the development of metastatic capability. Using these techniques, a metastasis-associated cytoskeletal calcium binding protein, S100A4 (p9Ka), has been identified as an inducer of metastatic capability in benign rat mammary epithelial cells. Metastasis can also be induced in the rat mammary epithelial cells by fragments of DNA from metastatic, but not from benign, human breast tumour cells. These non-coding fragments of DNA act via the induction of osteopontin, an extracellular, integrin binding, calcium binding protein. Since both osteopontin and S100A4 are thought to be associated with malignancy in human breast cancer specimens, gene transfer techniques can identify genes for metastasis-inducing proteins that may play a role in breast cancer, and further suggest that cell migration/motility might be important in the metastatic process.
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PMID:Use of DNA transfer in the induction of metastasis in experimental mammary systems. 951 30


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