Comparison of the effects of differentially sulphated bovine kidney- and porcine intestine-derived heparan sulphate on breast carcinoma cellular behaviour

Heparan sulphate is a sulphated glycosaminoglycan and is able to bind to and regulate the activity of many growth and signalling factors. We have previously shown that its expression is correlated with tumour grade and cell proliferation in breast phyllodes tumours. In this study, we examined the use of heparan sulphate as a biomarker of invasive ductal carcinoma and the effects of differentially sulphated heparan species on breast cancer cell behaviour. Immunohistochemistry using the 10E4 monoclonal antibody was carried out on 32 paraffin-embedded breast cancer specimens and paired non-cancerous breast tissues to compare the expression patterns of heparan sulphate. Upregulated expression of the sulphated 10E4 epitope in heparan sulphate was detected in both epithelial and stromal compartments of breast cancer compared with normal mammary tissues, with a 2.8X increase in immunoreactivity score. To determine the effects of differentially sulphated heparan sulphate molecules on breast cancer behaviour, cultured breast carcinoma cells were treated with chlorate, a competitive inhibitor of glycosaminoglycan sulphation, and two different heparan sulphate species. Inhibition of glycosaminoglycan sulphation resulted in a significant increase in cancer cell adhesion and a reduction in cell migration, together with upregulated expression of focal adhesion kinase and paxillin. Both porcine intestine- and bovine kidney-derived heparan sulphate species could block the change in cell adhesion. However, the former heparan sulphate species completely abolished, while the latter exacerbated, the chlorate-induced decrease in cell migration. The results show that heparan sulphate is a useful biomarker of breast invasive ductal carcinoma. Different sulphation patterns of heparan sulphate residues have differential effects in regulating breast cancer cellular behaviour, and this may be exploited to develop heparan sulphate into a useful target for treatment of breast carcinoma.     

Modulation of heparan-sulphate/chondroitin-sulphate ratio by glycosaminoglycan biosynthesis inhibitors affects liver metastatic potential of tumor cells

Previous data have indicated that the proteoglycan (PG) pattern is different on tumor cells with different liver metastatic potential. We selected “conventional” glycosaminoglycan (GAG) biosynthesis inhibitors, β T-D-xyloside (BX), 2-deoxy-D-glucose (2-DG), ethane-1-hydroxy-1, 1-diphosphonate (ETDP) and the newly discovered 5-hexyl-2-deoxyuridine (HUdR), to modulate PGs on highly metastatic/liver-specific 3LL-HH murine carcinoma and HT168 human melanoma cells and to influence their liver colonization potential. These compounds all induced remarkable changes in GAG biosynthesis, but to varying degrees: glucosamine labelling was affected mainly by 2-DG, and HUdR and sulphation by BX and HUdR. Furthermore, the ratio of he paran sulphate/chondroitin sulphate (HS/CS) of PGs was increased by ETDP and decreased after treatment by HUdR. In addition to changes in PG metabolism, tumor-cell proliferation and adhesion to fibronectin were affected; BX and 2-DG stimulated cell proliferation and adhesion, while HUdR inhibited both proliferation and adhesion. Most interestingly, HUdR, the most effective inhibitor of HS/HSPG, depressed the formation of liver colonies, while ETDP, the most effective inhibitor of CS/CSPG, stimulated the appearance of liver colonies. These observations indicated that, at least in these experimental systems, tumor cells with a high HS/CS ratio are more likely to form liver metastases; consequently, anti-HS agents could also be anti-metastatic. © 1995 Wiley-Liss, Inc.     

Expression of Brca1 and splice variant Brca1delta11 RNA levels in mouse mammary gland during normal development and tumorigenesis

Expression of Brca1 in mouse mammary cancer has yet to be analysed. We use a progressive model of neoplasia based on several mouse epithelial cell lines that represent distinct steps toward the fully tumorigenic state. Using RNase protection analysis because acceptable anti-Brca1 antibodies are not available we investigated the expression of Brca1 and a splice variant, Brca1Delta11, in several mammary hyperplasias and tumors that arose from them, and in normal mammary gland through pregnancy and involution. Expression of Brca1 was highest in rapidly proliferating cells. Expression of the full-length Brca1 was detectable in the virgin gland, was slightly elevated in the midpregnant gland, and decreased to levels similar to the age-matched virgin gland in the completely involuted gland. Expression of both forms of Brca1 was detectable in 9/9 paired hyperplasias and tumors, with levels of total Brca1, but not the splice variant Brca1Delta11, in tumors higher than those in the hyperplasias. While in disagreement with the observation that Brca1 levels decrease in human breast cancer progression, these patterns support the notion that Brca1 expression is associated with proliferating cells, and suggests that the link with differentiation seen in normal cells can be removed when cells become tumorigenic.     

A comparative study between mixed-type tumours from human salivary and canine mammary glands

Background  

In comparative pathology, canine mammary tumours have special interest because of their similarities with human breast cancer. Mixed tumours are uncommon lesions in the human breast, but they are found most frequently in the mammary gland of the female dogs and in the human salivary glands. The aim of the study was to compare clinical, morphological and immunohistochemical features of human salivary and canine mammary gland mixed tumours, in order to evaluate the latter as an experimental model for salivary gland tumours.     

The effect of isoprenaline on induction of tumours by methyl nitrosourea in the salivary and mammary glands of female wistar rats.

Pretreatment of rats with isoprenaline sulphate (IPR) stimulated DNA synthesis in both salivary and mammary gland tissues. Salivary gland tumours induced by N-methyl-N-nitrosourea (MNU) were observed for the first time in rats, but occurred only in IPR-pretreated animals given MNU during the period of IPR-stimulated DNA synthesis. The cumulative index of MNU-induced mammary tumours and the number of tumours per tumour-bearing rat were increased by IPR-pretreament only if the animals received MNU during the period of IPR-stimulated DNA synthesis.     

Fibronectin expression modulates mammary epithelial cell proliferation during acinar differentiation

The mammary gland consists of a polarized epithelium surrounded by a basement membrane matrix that forms a series of branching ducts ending in hollow, sphere-like acini. Essential roles for the epithelial basement membrane during acinar differentiation, in particular laminin and its integrin receptors, have been identified using mammary epithelial cells cultured on a reconstituted basement membrane. Contributions from fibronectin, which is abundant in the mammary gland during development and tumorigenesis, have not been fully examined. Here, we show that fibronectin expression by mammary epithelial cells is dynamically regulated during the morphogenic process. Experiments with synthetic polyacrylamide gel substrates implicate both specific extracellular matrix components, including fibronectin itself, and matrix rigidity in this regulation. Alterations in fibronectin levels perturbed acinar organization. During acinar development, increased fibronectin levels resulted in overproliferation of mammary epithelial cells and increased acinar size. Addition of fibronectin to differentiated acini stimulated proliferation and reversed growth arrest of mammary epithelial cells negatively affecting maintenance of proper acinar morphology. These results show that expression of fibronectin creates a permissive environment for cell growth that antagonizes the differentiation signals from the basement membrane. These effects suggest a link between fibronectin expression and epithelial cell growth during development and oncogenesis in the mammary gland.     

Transfection of activated Ha-ras protooncogenes causes mouse mammary hyperplasia

ras protooncogenes activated by a point mutation have been implicated in the initiation of mammary carcinogenesis. However, the nature of phenotypic alterations induced by activated ras protoonocogenes during initiation has not been well understood. In the present studies, the phenotypic manifestation of activated ras genes was directly analyzed by transfecting them into normal mouse mammary epithelial cells. The ras genes were cotransfected with pSV2neo which expresses the bacterial neomycin resistance gene to partially select for successful transfectants in culture. Transfection of activated Ha-ras protooncogenes, containing a point mutation in codon 12, caused hyperplasia in the mouse mammary gland following transplantation. Hyperplastic phenotype is a prerequisite for neoplastic development. The hyperplasias induced by the activated Ha-ras protooncogenes, however, were not immortal in vivo, another essential characteristic of preneoplastic and neoplastic mouse mammary cells. Control cells transfected only with pSV2neo did not produce any hyperplasia. These results suggest that a functional role of activated ras protooncogenes in the initiation of mouse mammary carcinogenesis may be the induction of a hyperplastic phenotype, a prelude to neoplastic development.     

Evidence that sulphated polysaccharides inhibit tumour metastasis by blocking tumour-cell-derived heparanases

Recent studies in this laboratory demonstrated that several sulphated polysaccharides can inhibit metastasis of the rat mammary adenocarcinoma 13762 MAT, probably by preventing the passage of tumour cells through the walls of blood vessels. In order to directly test this possibility, 13762 MAT cells were cultured with (35S)O4(=)-labelled subendothelial extracellular matrices (ECM) and ECM degradation was monitored in either the presence or absence of different sulphated polysaccharides. Degradation products were detected by sodium dodecyl sulphate polyacrylamide gel electrophoresis and subsequent autoradiography. The 5 sulphated polysaccharides that had previously been shown to possess anti-metastatic activity were potent inhibitors of the degradation of subendothelial ECM by 13762 MAT cells. In contrast, of the 4 polysaccharides tested that failed to inhibit metastasis, 3 had no effect on ECM breakdown and one (carrageenan-kappa) was substantially less effective at inhibiting ECM degradation than the anti-metastatic preparations. It was also shown that 13762 MAT cells produce a heparan sulphate-specific glycosidase (heparanase) that degrades the heparan sulphate side-chains of the ECM, the action of this enzyme rather than that of other ECM-solubilizing enzymes being inhibited by the antimetastatic sulphated polysaccharides. Additional experiments indicated that the anti-coagulant activity of the polysaccharides probably plays a minor role in their anti-metastatic effects since heparin, almost completely depleted (98-99.5%) of heparin molecules with anti-coagulant activity by passage over an anti-thrombin III column, retained its ability to inhibit 13762 MAT heparanases and was almost as effective as unfractionated heparin at inhibiting tumour-cell metastasis. Collectively, these data suggest that sulphated polysaccharides inhibit the metastasis of 13762 MAT cells by inhibiting tumour-cell-derived heparanases involved in the penetration of the vascular endothelium and its underlying basement membrane by tumour cells.     

Effect of antioxidants and antitoxicants of isoniazid on the formation of lung tumours in mice by isoniazid and hydrazine sulphate

The present study reports the effects of antioxidants and antitoxicants on the formation of lung tumours in Swiss mice induced by isoniazid (INH) and hydrazine sulphate (HS).Dietary administration of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) or simultaneous oral administration of antitoxicants (l-arginine, l-sodium glutamate and pyridoxine hydrochloride) failed to prevent HS-induced lung tumours. On the other hand BHA and BHT inhibited the formation of lung tumours in groups of mice receiving INH. Folic acid supplementation had marginal effect on the formation of lung tumours in groups receiving HS (P < 0.1).Higher lung tumour incidence was observed in groups maintained only on BHT diet as compared to animals maintained on standard diet.     

Prolactin binding in benign and malignant mammary tissue of female dogs

Prolactin receptor (PRL-R) concentrations were determined in membrane preparations of canine mammary tumours and of non-affected mammary tissues by a radioreceptor-assay using ovine prolactin (oPRL) both for 125I-labelling and for displacement. Receptor levels greater than or equal to 3 fmol/mg membrane protein were considered positive. Histologically non-affected samples of mammary tissue from 6 dogs were PRL-R positive (12-195 fmol/mg protein). These levels were positively correlated with epithelium content (based on surface area in microscopic sections; r = 0.943, P less than 0.02). In tumour samples where pre-existing mammary epithelium (PME) was present (3 non-malignant and 6 malignant tumour samples; PME content 5-10%), the cut-off limit for PRL-R positivity was increased to 50 fmol/mg protein to forestall false positives due to non-affected tissue. If no PME was present the general limit of 3 fmol/mg protein was maintained. All 18 non-malignant tumours showed PRL-R (18-162 fmol/mg protein). The PRL-R levels were positively correlated with levels of oestrogen-(ER; r = 0.735, P less than 0.002) and progesterone receptors (PgR; r = 0.556, P less than 0.02) as measured by a multi-concentration dextran-coated charcoal method. ER and PgR levels were also proportional (r = 0.660, P less than 0.01). In 6 dogs bearing primary cancers with 5-10% PME, 1 out of a total of 6 tumours was PRL-R positive. In 9 dogs bearing primary or locally recurrent cancers without PME, significant PRL-R levels were measured in 2 out of a total of 10 tumours. Three metastatic sites in 2 other dogs were PRL-R positive. In 2 dogs (1 with a PRL-R negative local recurrence) the metastatic lesions were PRL-R negative. Thus 5 dogs of a total of 18, had PRL-R positive mammary cancers (3-377 fmol/mg protein). Unlike in non-malignant lesions the ER, PgR, and PRL-R levels were not related. In mammary cancer the presence of PRL-R was less common (P less than 0.001), and the ultimate levels less high (P less than 0.001) than in non-malignant tumours. In comparative studies using pooled membrane preparations from benign mammary tissues, oPRL was far more effective than canine prolactin (cPRL) in displacing 125I-oPRL; canine growth hormone (cGH) in this respect was ineffective. It is concluded that non-malignant mammary tissue in the dog generally is PRL-R positive; only some mammary cancers retain the PRL receptors.     

Analysis of the inhibition of tumour metastasis by sulphated polysaccharides

Lung metastases resulting from the intravenous (i.v.) injection of cells from the rat mammary adenocarcinoma 13762 MAT were significantly reduced by a variety of sulphated polysaccharides, the most effective being heparin, fucoidan and Carrageenan lambda. Although all the inhibitory polysaccharides were anticoagulants, it is unlikely that anticoagulation is the total explanation of their antimetastatic effect because: (i) heparin preparations from 2 different suppliers, although exhibiting comparable anticoagulant activities, differed 10-fold in their antimetastatic capability; (ii) certain sulphated polysaccharides consistently gave a 30% difference in the number of metastatic lesions, yet exhibited identical anticoagulant activity; and (iii) the entrapment of 13762 MAT cells in the lung was not impaired by heparin or fucoidan. It was more probable that the sulphated polysaccharides were interfering with the passaging of tumour cells across the capillary wall as heparin significantly inhibited metastasis when injected up to 3 hr after lodgement, and heparin and fucoidan caused a gradual loss of tumour cells from the lung which only became apparent greater than 1 hr following cell lodgement. The data did not eliminate the possibility that tumour cell adhesion to the endothelium occurred via sulphated polysaccharide recognition. A negative correlation existed between the sulphated polysaccharides that bound to the surface of the tumour cells and those that inhibited metastasis.     

Tumour incidence in mammary glands transplanted from the strains C3H and O20 into their mammectomized F1-hybrids

It has been demonstrated that genetic factors play an important role in the genesis of mammary cancer in mice but it was not known if the genetic action is localized in the mammary gland tissues or if the genetic influence is effective through some systemic mechanism. In this investigation the mammary glands from the inbred strains C3Hf and O20, differing in the incidence of mammary tumours, were transplanted into a common host, the F₁ hybrid, so that systemic influences would be equal. A difference in susceptibility to tumour development was found between the transplanted C3Hf and O20 mammary glands. In the group of animals free of the agent there is a difference in tumour frequency. In the animals carrying the mammary tumour agent this difference is expressed in the average tumour age at which the tumours develop. The genetic susceptibility in these two strains is, therefore, retained in the transplanted mammary glands. Transplantation per se has no influence on tumour development. Transplanted mammary glands react in the same manner as mammary glands in situ. All transplantations have been done into completely mammectomized hosts to avoid interference with tumours developing in the glands of the host. Investigations with partly mammectomized animals have shown that the mammary tumour frequency and the average tumour age are related to the amount of mammary gland tissue present. A reduction of the mammary gland tissue also reduces the tumour frequency or delays the appearance of mammary tumours.     

Metastasis of murine mammary tumour lines from the mammary gland and ectopic sites.

A murine model of spontaneous metastasis of mammary adenocarcinomas in mice was developed by serial transplantation of spontaneous BALB/cfC3H/ Crgl tumours into the mammary gland. Through 8 transplant generations, 5 lines demonstrated maintenance of metastatic phenotype and consistent gross and histological morphology and growth properties. Tumour lines M12, M35 , and M51 metastasized from the mammary gland with overall frequencies of 53, 80, and 85%, respectively. Line T5 was weakly metastatic, capable of a minor degree of lung colonization in 8% of hosts, while line WT2 failed to establish any grossly or histologically detectable pulmonary foci. The significance of the mammary gland as transplant site was shown by comparing the growth and metastasis of these lines in mammary gland with that observed upon subcutaneous transplantation. Subcutaneous metastatic frequency of one tumour line was significantly reduced from that obtained when grown in the mammary gland while histological organization differed markedly in 2 of the tumours. Furthermore, while tumours implanted into the gland grew as well encapsulated masses, the same tumours grown subcutaneously frequently invaded the body wall and occasionally colonized adjacent peritoneal organs and, more often, mesenteries. Intravenous injection of dissociated tumours further emphasized the importance of events that occur at the primary site. There was no correlation between spontaneous metastatic ability and the capacity to colonize the lung following i.v. inoculation. This study demonstrates the importance of transplant site in the assessment of metastasis in experimental systems.     

A contrasting function for miR-137 in embryonic mammogenesis and adult breast carcinogenesis

MicroRNAs are differentially expressed in breast cancer cells and have been implicated in cancer formation, tumour invasion and metastasis. We investigated the miRNA expression profiles in the developing mammary gland. MiR-137 was expressed prominently in the developing mammary gland. When the miR-137 was over-expressed in the embryo, the mammary epithelium became thickened. Moreover, genes associated with mammary gland formation such as Tbx3 and Lef1 were not expressed. This suggests that miR-137 induces gland formation and invasion. When miR-137 was over-expressed in MDA-MB-231 cells, their ability to form tumours in adult mice was significantly reduced. These data support miR-137 decides epithelial cell behavior in the human breast cancer. It also suggests that miR-137 is a potential therapeutic target for amelioration of breast cancer progression.     

Early neoplastic and metastatic mammary tumours of transgenic mice detected by 5-aminolevulinic acid-stimulated protoporphyrin IX accumulation

A photodynamic technique for human breast cancer detection founded upon the ability of tumour cells to rapidly accumulate the fluorescent product protoporphyrin IX (PpIX) has been applied to transgenic mouse models of mammary tumorigenesis. A major goal of this investigation was to determine whether mouse mammary tumours are reliable models of human disease in terms of PpIX accumulation, for future mechanistic and therapeutic studies. The haeme substrate 5-aminolevulinic acid (5-ALA) (200 mg kg(-1)) was administered to mouse strains that develop mammary tumours of various histological subtypes upon expression of the transgenic oncogenes HRAS, Polyoma Virus middle T antigen, or Simian Virus 40 large T antigen in the mammary gland. Early neoplastic lesions, primary tumours and metastases showed consistent and rapid PpIX accumulation compared to the normal surrounding tissues, as evidenced by red fluorescence (635 nm) when the tumours were directly illuminated with blue light (380-440 nm). Detection of mouse mammary tumours at the stage of ductal carcinoma in situ by red fluorescence emissions suggests that enhanced PpIX synthesis is a good marker for early tumorigenic processes in the mammary gland. We propose the mouse models provide an ideal experimental system for further investigation of the early diagnostic and therapeutic potential of 5-ALA-stimulated PpIX accumulation in human breast cancer patients.     

Mouse mammary hyperplasias and neoplasias exhibit different patterns of cyclins D1 and D2 binding to cdk4

Deregulated expression of G1 cyclins D1 and D2 is a featureof some neoplasias. This study examined the altered expressionof D1 and D2 cyclins, both the total pool and as associatedwith cdk4 and cdk2, at different stages of mouse mammary tumorigenesis.Three different mammary hyperplastic outgrowth lines, TM2, TMl0and TM12, and their respective tumors were examined. Increasinglevels of the cyclin D1 protein pool, D1 binding to cdk4 andcdk2 and cdk4 kinase activity were closely correlated with tumorigenesis.In constrast, cyclin D2 binding to cdk4 was predominant in hyperplasiasand much less in tumors, where cyclin D1 became predominant.However, the cyclin D2 pool showed increases of 15–65times in hyperplasias compared with the normal gland and furtherincreases of 11–15 times in two of three different tumors.The message level for cyclin D1 increased only 2–3 timesin tumors compared with normal gland. Cyclin D2 mRNA was highestin normal tissue and decreased only marginally in tumors. Theseresults suggest that cyclin D2 functions uniquely from cyclinD1 in the early stages of mouse mammary tumor development. CyclinD2 bound to cdk4 may act to guarantee a low level of kinaseactivity in hyperplasias and may be an attempt to direct themammary epithelial cells through differentiation rather thanproliferation. This interaction may be one of the negative regulatorymechanisms in the early stages in mouse mammary tumor development,until cyclin D1 totally replaces cyclin D2 binding to cdk4,which would activate the high levels of cdk4 kinase activityobserved in neoplasias.     

Mammary cancer in transgenic mice expressing insulin-like growth factor II (IGF-II)

The effect of insulin-like growth factor II (IGF-II) on tumour development in the mouse mammary gland was studied. To promote extra IGF-II expression in the mammary gland, sheep beta-lactoglobulin regulatory elements were attached to the coding regions of the mouse Igf-2 gene and injected into the pronuclei of mouse zygotes. Mammary tumours developed in each of the four independent lines of mice which expressed transgene IGF-II in the gland. Tumours from two of the lines grew after transplantation to both male and female hosts. Primary tumours contained stromal and epithelial regions, but the tumours were dominated by mammary adenocarcinoma after transplantation. The tumours expressed high levels of Igf-2 mRNA transcribed from the integrated transgenes.     

Activation of beta-catenin in prostate epithelium induces hyperplasias and squamous transdifferentiation

The Wnt/beta-catenin signaling pathway is critical for normal mammalian development, the specification of epidermal cells and neoplastic transformation of intestinal epithelium. However, precise molecular information regarding cell-specific responses to beta-catenin signaling has been limited. This question was addressed using a mouse model in which exon 3 of the beta-catenin gene was deleted in several cell types with loxP-mediated recombination utilizing a Cre transgene under control of the mouse mammary tumor virus-long terminal repeat (MMTV-LTR). The stabilization of beta-catenin in prostate epithelium resulted in hyperplasias and extensive transdifferentiation into epidermal-like structures, which expressed keratins 1 and 6, filaggrin, loricrin and involucrin. The cell-specific loss of NKCC1 protein and reduced nuclear Stat5a is further suggestive of a loss of prostate epithelial characteristics. In addition to the prostate, hyperplasias and squamous metaplasias were detected in epithelia of the epididymis, vas deferens, coagulating gland, preputial gland and salivary gland. However, and in contrast to a recent study, no lesions reminiscent of high-grade prostate intraepithelial neoplasia were detected. Since beta-catenin was activated in several cell types and impinged upon the viability of these mice, it was not possible to evaluate the cumulative effect over more than 3 months. To assess long-term consequences of beta-catenin activation, mutant and control prostate tissues were transplanted into the mammary fat pads of wild-type males. Notably, squamous metaplasias, intra-acinous hyperplasia and possible neoplastic transformation were observed after a total of 18 weeks of beta-catenin stimulation. This suggests that the transdifferentiation into squamous metaplasias is an early response of endoderm-derived cells to beta-catenin, and that the development of intra-acinous hyperplasias or neoplastic foci is a later event.