Oestrogens, proteases and breast cancer. From cell lines to clinical applications

Breast and prostate cancer

There are interesting similarities between carcinomas of the breast and prostate. Both genetic and exogenous factors are probably important in the development of breast and prostate cancers. Since there is an alarming increasing trend in the incidence of both cancers worldwide including India, high level of apprehension/awareness has been created among the general educated population. Furthermore, both cancers are strongly linked with the expression of the c-erbB-2 oncogene which has been the focus of basic research in the recent past. This gene belongs to the family of growth factor receptors and it has important implication in diagnosis and future treatment modalities.

Variation in plasma insulin-like growth factor-1 and insulin-like growth factor binding protein-3: genetic factors

Insulin-like growth factors (IGFs) play key roles in cell proliferation and apoptosis. Whereas relatively stable within individuals, IGFs vary substantially between individuals, and a large component of this variation may be determined by genetic factors. Several polymorphisms in IGF genes have been identified, although their functional significance is not clear. We evaluated the association of polymorphisms in IGF-1 and IGFBP-3 and circulating levels of IGF-1 and IGFBP-3 in 323 population-based control subjects enrolled in a case-control study of colorectal cancer from September 1999 through February 2002. Total IGF-1 and IGFBP-3 levels were measured using ELISA assays, and all subjects were genotyped for a microsatellite polymorphism in IGF-1 and a single nucleotide polymorphism in IGFBP-3. Multiple linear regression was used to assess the association of genotype with circulating IGFs. IGF-1 levels were unrelated to either polymorphism. IGFBP-3 was significantly associated with IGFBP-3 genotype, with IGFBP-3 levels increasing from CC (1,895 ng/mL) --> GC (2,029 ng/mL) --> GG (2,182 ng/mL), (p-trend < 0.001). Having an IGF-1 genotype other than homozygous for the 19-repeat allele was associated with higher IGFBP-3 levels (1,945 versus 2,052 ng/mL). Furthermore, both IGF-1 and IGFBP-3 genotypes modified the relationship between postmenopausal hormone use and IGFs. This analysis provides evidence that common variation in IGF genes may contribute to the variation in circulating levels observed between individuals.

Irradiation differentially affects substratum-dependent survival, adhesion, and invasion of glioblastoma cell lines

Effects of ionising radiation on extracellular matrix (ECM)-modulated cell survival and on adhesion and invasion are not well understood. In particular, the aggressiveness of glioblastoma multiforme has been associated with tumour cell invasion into adjacent normal brain tissue. To examine these effects in more depth, four human glioblastoma cell lines (A-172, U-138, LN-229 and LN-18) were irradiated on fibronectin (FN), Matrigel, BSA or polystyrene. Major findings of this study include a significantly increased survival of irradiated A-172 but not of irradiated U-138, LN-229, and LN-18 cells on FN or Matrigel compared to cells irradiated on polystyrene or BSA. Irradiation induced a dose-dependent increase in functional β1- and β3-integrins in all four glioma cell lines. This integrin induction caused improved cell adhesion to FN or Matrigel. In contrast to U-138, LN-229 and LN-18 cells, irradiation strongly impaired A-172 cell invasion. Invasion of all cell lines was inhibited by anti-integrin antibodies, the disintegrin echistatin and the MMP-2/-9 inhibitor III. Additionally, β1- and β3-integrins modulated basal and radiation-altered gelatinolytic activity of MMP-2. Tested glioblastoma cell lines showed a differential cellular susceptibility to FN or Matrigel which affected the cellular radiosensitivity. Three out of four glioma cell lines demonstrated a combination of a substratum-independent survival after irradiation and an invasive potential which was not affected by irradiation. β1- and β3-integrins were identified to play a substantial, regulatory role in survival, adhesion, invasion and MMP-2 activity. Detailed insights into radioresistance and invasion processes might offer new therapeutic strategies to enhance cell killing of lethal high-grade astrocytoma.

The GH-IGF-I axis and breast cancer

The growth hormone-insulin-like growth factor-I (GH-IGF-I) axis plays a fundamental role in the development of the breast. The maintenance of breast tissue architecture is aided by its effect on proliferation, differentiation and apoptosis. There has been increasing recognition of its role as a major determinant of breast cancer and, more recently, its involvement in the development of resistance to both tamoxifen and an important novel therapy for advanced disease, trastuzumab (Herceptin). Here, we discuss the influence of the GH-IGF-I axis in normal mammary development and homeostasis, its putative role in breast tumorigenesis and its interactions with estrogen signalling.

Procathepsin D in breast cancer: what do we know? Effects of ribozymes and other inhibitors

Procathepsin D (pCD) is a major secreted glycoprotein in some human breast and other cancer cell lines. Several groups proposed that pCD served as a growth factor for these cell lines. Secreted pCD has been demonstrated in tissue section, tissue culture supernatants, carcinoma cytosols, and nipple aspirates. Moreover, several clinical studies suggested a potential role for this molecule in metastasis because its concentration in primary tumors correlated with an increased incidence of tumor metastases. In this paper, the effects of pCD were evaluated by proliferation in vitro and by mouse studies in vivo. Subsequent flow cytometry experiments showed the specificity of pCD binding to cancer cells. Cell cultivation showed that addition of either pCD or its activation peptide stimulates growth of cancer cells. These effects can be inhibited both in vitro and in vivo by anti-pCD antibodies. In addition, production of pCD can be inhibited by specifically designed ribozymes. This paper is focused on mitogenic effects of pCD, which seem to involve interaction of the activation peptide with as yet unidentified receptor. Different mechanisms by which pCD could promote development and spread of cancer cells are discussed.

Cathepsin-D in primary breast cancer: prognostic evaluation involving 2810 patients

There is controversy regarding the prognostic value of cathepsin-D in primary breast cancer. An increased level of cathepsin-D in tumour extracts has been found to be associated with a poor relapse-free and overall survival. Studies performed with immunohistochemistry or Western blotting have produced diverse results. We have analysed 2810 cytosolic extracts obtained from human primary breast tumours for cathepsin-D expression, and have correlated their levels with prognosis. The median follow-up of the patients still alive was 88 months. Patients with high cathepsin-D levels had a significantly worse relapse-free and overall survival, also in multivariate analysis (P < 0.0001). Adjuvant therapy which was associated with an improved prognosis in node-positive patients in univariate analysis, also significantly added to the multivariate models for relapse-free and overall survival. There were no statistically significant interactions between the levels of cathepsin-D and any of the classical prognostic factors in analysis for relapse-free survival, suggesting that the prognostic value of cathepsin-D is not different in the various subgroups of patients. Indeed, multivariate analyses in subgroups of node-negative and -positive patients, pre- and post-menopausal patients, and their combinations, showed that tumours with high cathepsin-D values had a significantly poor relapse-free survival, with relative hazard rates ranging from 1.3 to 1.5, compared with tumours with low cathepsin-D levels. The results presented here on 2810 patients confirm that high cytosolic cathepsin-D values are associated with poor prognosis in human primary breast cancer.

Cathepsin D in cancer metastasis: a protease and a ligand

Cathepsin D (cath-D) overexpression in breast cancer cells is associated with increased risk of metastasis in patients according to several clinical studies. No alterations of pro-cath-D structure or activation have been demonstrated in cancer cells. However, overexpression and dysrouting of pro-cath-D in illegitimate compartments could have consequences on tumor progression. Transfection of a human cDNA cath-D expression vector increases the metastatic potential of 3Y1-Ad12 embryonic rat tumorigenic cells when intravenously injected into nude mice. The mechanism by which cath-D increases the incidence of clinical metastasis seems to involve increased cell growth and decreased contact inhibition rather than escape of cancer cells through the basement membrane. Different mechanisms are discussed by which cath-D could act as a protease following its activation or as a ligand of different membrane receptors at a more neutral pH.

Bilateral orbital metastases from breast carcinoma. A case of false pseudotumor

OBJECTIVE

To inform clinicians of a metastatic orbital neoplasm that frequently masquerades as an orbital inflammatory syndrome and to stimulate thought regarding this neoplasm's fundamental pathobiology specific to its orbital involvement.

DESIGN

Interventional case report and literature review.

PARTICIPANTS

A 47-year-old woman with an acquired, bilateral, diffusely infiltrative orbital process is described.

INTERVENTION

The clinical and radiographic features of the patient's orbital process are reported. The review of two prior fine-needle aspiration biopsy specimens failed to reveal a diagnosis. Histopathologic examination of an open surgical biopsy specimen included standard light microscopy of frozen and formaldehyde-fixed, paraffin-embedded tissue.

RESULTS

Characteristics light microscopy findings suggested the diagnosis of metastatic lobular carcinoma of the breast. The patient refused all therapeutic intervention and died 9 months after orbitotomy.

CONCLUSION

The presentation of breast carcinoma metastatic to the orbit as a bilateral infiltrative process is far more common than appreciated previously. Its rate of bilateral orbital involvement is 20%, whereas this rate for other adult neoplasms is much lower. The authors report an additional case, review the clinical features of previous case reports and series, and discuss aspects of the metastatic process. Breast carcinoma must be included in the differential diagnosis of infiltrative orbital processes encountered in adult female patients. When "orbital pseudotumor" is detected in an adult female patient, a thorough medical history must be obtained and physical examination performed. If a possible primary breast carcinoma is indicated, one must be wary of metastatic disease, and a histologic orbital diagnosis is warranted. The frequency of orbital metastasis and bilateral orbital involvement of this neoplasm reinforces the possibility for organ-specific metastases.

Design of sensitive fluorogenic substrates for human cathepsin D

Cathepsin D is a lysosomal aspartic proteinase that has been implicated in several pathological processes such as breast cancer and Alzheimer's disease. We designed and synthesized a number of quenched fluorogenic substrates with P2 variations in the series AcEE(EDANS)KPIXFFRLGK(DABCYL)E-NH2, where X=cysteine, methylcysteine, ethylcysteine, tert-butylcysteine, carboxymethylcysteine, methionine, valine or isoleucine. Most of the fluorogenic substrates exhibited greater k(cat)/Km ratios than the best cathepsin D substrates described so far. Differences in kinetic constants, which were rationalized using structure-based modeling, might make certain substrates useful for particular applications, such as active site titrations or initial velocity determination using a fluorescent plate reader.

Oestrogen/growth factor cross-talk in breast carcinoma: a specific target for novel antioestrogens

Breast cancer cells express receptors for and are sensitive to a variety of steroids, polypeptide hormones and growth factors; the blocking of and/or the interference with their biochemical pathways could represent a new approach to breast tumour therapy. Antioestrogens achieve such a goal by competing with oestradiol for binding to the oestrogen receptors through which intracellular effects of the hormone are mediated. Tamoxifen has undergone the most extensive clinical evaluations and represents the treatment of choice for the endocrine management of breast cancer. Nevertheless, it is well known that tamoxifen retains agonist activity both in vitro and in vivo. To circumvent this disadvantage, new molecules with steroid-like structure, represented by ICI 164,384 and ICI 182,780, have been synthesized. In this review, Alessandra de Cupis and Roberto Favoni review data about the cross-talk between the two major families of breast cancer growth regulator: oestrogens and growth factors, focusing on the use of nonsteroidal antioestrogens and the new generation of steroidal antioestrogens as possible specifically targeted inhibitors of breast tumour proliferation.

Both estradiol and tamoxifen decrease proliferation and invasiveness of cancer cells transfected with a mutated estrogen receptor

Previous studies have shown that, after wild-type estrogen receptor (ER) transfection in ER-negative breast cancer cells, estradiol but not tamoxifen prevents growth, invasiveness and metastasis of these cells in mice. Because an ER mutation at position 400 converts the triphenylethylene antiestrogen, OH-tamoxifen into a full estrogen agonist, we transfected this mutated form of human ER in an ER-negative rat cancer cell line. This was aimed at inducing an inhibitory, estrogen-like response of tamoxifen in these cells. In two stable ER-positive transfectants, OH-tamoxifen inhibited cell growth and invasiveness in vitro as efficiently as estradiol. The pure antiestrogen, ICI 164,384, was not agonistic alone and antagonized estrogen action. In contrast, the three compounds were ineffective in control mock-transfected cells. When injected into ovariectomized nude mice, ER-negative mock-transfected cells formed tumours which were significantly stimulated by estradiol and inhibited by tamoxifen treatment. This indicates that estradiol and tamoxifen altered the growth of ER-negative tumours via a general effect on the host response. Surprisingly, the hormone responsiveness of ER-positive tumours developed from ER-transfected cells did not significantly differ from that of ER-negative (mock-transfected) tumours. We conclude that transfection of a mutated human estrogen receptor inhibited, through an estrogenic activity of tamoxifen, the growth and invasiveness of these cancer cells in vitro. However, the low expression of ER did not allowed us to obtain the same effect of tamoxifen in vivo.

An in vitro approach to ruminant mammary gland biology

This review discusses both fundamental and applied in vitro studies on ruminant mammary gland biology and summarizes progress made over the last decade in development of in vitro techniques to study growth, function and pathology of the mammary gland. The advantages and limitations of different in vitro systems are considered including explant cultures, primary cell cultures and immortalized lines of mammary-derived cells from cow, sheep and goat. The cell growth, differentiation and response to lactogenic hormones and growth factors are discussed as well as the relevance of the cell behavior in different culture conditions.

Estrogen action in human ovarian cancer

Evidence is accumulating for a facilitative role for estrogen in ovarian cancer. Although response to antiestrogen therapy has been poor, there is a distinct subset of patients that respond. Strategies for treatment of ovarian cancer would be improved by identification of patients likely to respond to hormonal therapy. Cell culture models that are responsive or resistant to estrogen and antiestrogen may be of value in finding markers that predict responsiveness to hormonal therapy. Several model cell lines have been generated that express ER and proliferate in response to estrogen in vitro. Further studies are needed to better characterize the response of these ER positive cells lines to estrogen in vivo in mouse xenograft models. Expression of many of the same genes are regulated by estrogen in breast and in ovarian cancer cell lines. One exception may be the HER-2/neu oncogene product, which is down-regulated by estrogen in responsive breast carcinoma cells but not in two ovarian carcinoma cell lines. Initial analyses of several estrogen responsive and one resistant cell model suggests the potential value of progesterone receptor presence and low levels of HER-2/neu expression for predicting responsiveness to hormonal therapy. Additional cell models need to be investigated to determine the frequency with which these markers are associated with antiestrogen resistance.

Immunolocalization of cathepsin D in pneumocytes of normal human lung and in pulmonary fibrosis

Cathepsin D expression has been assessed by immunohistochemistry and immunoelectron microscopy in fetal, normal adult and injured lungs of human beings. In addition to the well known positivity of alveolar macrophages and the bronchial epithelial cells, normal type I and to a lesser extent type II pneumocytes showed a granular, cytoplasmic staining pattern. Using immunogold labelling of lowicryl embedded human lung, cathepsin D was present in lysosomes of epithelial cells. Double immunofluorescence labelling employing type I and type II specific antibodies or lectins confirmed the epithelial staining for cathepsin D. At the terminal sac period during lung development cathepsin D appears in the alveolar epithelium. In fibrotic specimens, enhanced immunoreactivity was found in epithelial and non-epithelial cells. Proliferative epithelial formations were strongly stained with cathepsin D antibodies, whereas detached, desquamated epithelial cells were weakly positive or negative. We suggest that cathepsin D plays a role in the remodelling process during fibrogenesis.

Cellular localisation by in situ hybridisation of cathepsin D, stromelysin 3, and urokinase plasminogen activator RNAs in breast cancer

We have compared by RNA in situ hybridisation on serial cryo-sections the distribution of cathepsin D (cathD), stromelysin 3 (strom-3), and urokinase plasminogen activator (UPA) gene expression in different tissues of human benign and malignant mammary tumors. Cath-D expression was found to be higher in adenocarcinomas compared to non-tumoral glands. The cath-D RNA was located in mammary epithelial cancer cells rather than in fibroblasts, indicating that the cath-D gene was overexpressed in cancer cells, where the corresponding protein determined by immunohistochemical staining had been shown to be accumulated (E Roger et al., Human Pathol 25: 863-871,1994). In contrast strom-3 RNA in adjacent tissue sections used as a control of tissue localisation was mostly expressed in peritumoral fibroblasts rather than in cancer cells confirming previous results of Basset et al. and validating our methodology. UPA RNA was detected both in tumor cells and in stromal cells. In benign lesions the 3 protease RNAs were mostly found in epithelial cells. Stromal cells expressed UPA RNA in 5 of 7 lesions, cath-D and strom-3 in only one sample. We conclude that in breast cancer patients, cath-D gene expression is increased in epithelial mammary cancer cells at the RNA level as well as at the protein level, suggesting an altered transcriptional regulation. In non malignant lesions, the distribution was different with a predominant distribution in epithelial mammary cells for the 3 protease messenger RNA.

Estrogens increase the expression of fibulin-1, an extracellular matrix protein secreted by human ovarian cancer cells

Ovarian cancers have a high ability to invade the peritoneal cavity and some are stimulated by estrogens. In an attempt to understand the mode of action of estrogens on these cancer cells and to develop new markers, we have characterized estrogen-regulated proteins. This study was aimed at identifying a protein secreted by ovarian cancer cells whose level was increased by estradiol [Galtier-Dereure, F., Capony, F., Maudelonde, T. & Rochefort, H. (1992) J. Clin. Endocrinol. Metab. 75, 1497-1502]. By using microprotein sequencing, the 110-kDa protein was identified as fibulin-1, a protein of the extracellular matrix that binds to fibronectin, laminin, and nidogen. The amount of immunoprecipitated fibulin-1 secreted into the medium and present in the cell extract was increased up to 10-fold by estradiol in three estrogen-responsive ovarian cancer cell lines. By immunohistochemistry fibulin-1 was located in the stroma of several ovarian cancers and cysts. The findings highlight a potential role for fibulin-1 in the spread of ovarian cancer in the peritoneal cavity and/or in distal metastases.

Insulin-like growth factors in breast cancer

Insulin-like growth factor (IGF)-I is one of the most potent mitogens to many breast cancer cell lines in vitro. Effective growth inhibition in vitro may be achieved by antibodies to the type I IGF receptor (IGF-IR) or by using antisense strategies. Most human breast cancers express IGF-IR in vivo. Thus, different therapeutic strategies aimed at inhibiting ligand stimulation of the IGF-IR may be an attractive treatment option against breast cancer. Several drugs commonly used in breast cancer influence the IGF system both in vitro and in vivo. While antioestrogens such as tamoxifen and droloxifene reduce the expression of IGF-IR in vitro and suppress plasma levels of IGF-I but elevate IGF-binding protein-1 in vivo, megestrol acetate may reduce the delivery of IGFs to the tissues by inhibition of IGFBP-3 protease activity.