Description of a New Monoclonal Antibody, FC-2.15, Reactive with Human Breast Cancer and other Human Neoplasias

FC-2.15 is an IgM monoclonal antibody (MAb) obtained by immunizing Balb/c mice with tumor epithelial cells from a human undifferentiated primary breast carcinoma. FC-2.15 reacts with 93.9% (31/33) of human breast primary tumors, independently of their histology and hormone receptor content. Moreover, FC-2.15 reacts with 79.6 ± 13.8% (mean ± SD) of total breast malignant tumor cells and with 88.7 ± 9.9% of proliferating tumor cells. It recognizes other neoplasia such as colon cancer, squamous carinoma and melanoma. Among the normal tissues examined, strong cross-reactivity was found with kidney proximal convolute tubules, bone marrow myeloid progeny, peripheral granulocytes and large bowel epithelium. Through Western blots, FC-2.15 recognizes three major bands of Mr 160 kDa, 130 kDa and 115 kDa in membrane extracts of MCF-7 cells grown in nude mice and of human breast carcinoma and three major bands of 250 kDa, 185 kDa and 105 kDa in membrane extracts of peripheral granulocytes. This MAb mediates complement- cytotoxicity against malignant cells, reducing the clonogenic capacity of breast primary tumor cells and MCF-7 cells to 35.6 ± 41.2% and 11.7 ± 4.8 % of control values respectively, whereas that of normal bone marrow cells is not affected (104.7 ± 17.4%).

Hippocampal SPARC regulates depression-related behavior

SPARC (secreted protein acidic and rich in cysteine) is a matricellular protein highly expressed during development, reorganization and tissue repair. In the central nervous system, glial cells express SPARC during development and in neurogenic regions of the adult brain. Astrocytes control the glutamate receptor levels in the developing hippocampus through SPARC secretion. To further characterize the role of SPARC in the brain, we analyzed the hippocampal-dependent adult behavior of SPARC KO mice. We found that SPARC KO mice show increased levels of anxiety-related behaviors and reduced levels of depression-related behaviors. The antidepressant-like phenotype could be rescued by adenoviral vector-mediated expression of SPARC in the adult hippocampus, but anxiety-related behavior persisted in these mice. To identify the cellular mechanisms underlying these behavioral alterations, we analyzed neuronal activity and neurogenesis in the dentate gyrus (DG). SPARC KO mice have increased levels of neuronal activity, evidenced as more neurons that express c-Fos after a footshock. SPARC also affects cell proliferation in the subgranular zone of the DG, although it does not affect maturation and survival of new neurons. SPARC expression in the adult DG does not revert the proliferation phenotype in KO mice, but our results suggest a role of SPARC in limiting the survival of new neurons in the DG. This work suggests that SPARC could affect anxiety-related behavior by modulating neuronal activity, and that depression-related behavior is dependent upon the adult expression of SPARC, which affects adult brain function by mechanisms that need to be elucidated.

Mice vaccination with interleukin 12-transduced colon cancer cells potentiates rejection of syngeneic non-organ-related tumor cells

Cell-based gene therapy after cytokine gene transfer is being investigated for autologous and allogeneic vaccination in cancer therapy. Here we show that mice vaccinated with 3-5 x 10(6) interleukin 12 (IL-12) gene-transduced CT26 colon cancer cells developed a long-lasting antitumor immune memory able to reject not only parental cells but also syngeneic, LM3 mammary, and MCE fibrosarcoma tumorigenic cells. In contrast, mice vaccinated with 0.5-1 x 10(6) CT26 cells transduced with pBabe neo IL-12 retrovirus cells (CT26-IL12) were only able to reject parental cells. An increase in the total circulating levels of IgG2a and a clear shift toward a systemic Th1 response developed, regardless of the amount of injected CT26-IL12 cells. On the contrary, a strong increase in anti-CT26-specific IgG2a levels was observed only when 3-5 x 10(6) CT26-IL12 cells were injected. Immunocompetent mice vaccinated with 3-5 x 10(6) CT26-IL12 cells developed local nodules for a few days, which then ceased growing. These nodules comprised mainly blood vessels, suggesting that an angiogenic process was taking place. CD8+ T cells were responsible for the anti-LM3 tumor cell memory, whereas CD4+ T cells were not involved. Splenocytes and lymphocytes obtained from mice immunized against CT26 cells were able to kill LM3 cells in vitro. Adoptive transfer of lymphocytes obtained from animals immunized against CT26 colon cancer cells suppressed LM3 mammary tumor growth in tumor-bearing mice. The present studies raised the possibility of isolating CTL clones and identifying CTL epitopes shared by different tumor cell types, which can be a target for cancer therapy.

Bias in estimations of DNA content by competitive polymerase chain reaction

Competitive PCR is a highly sensitive method for specific DNA quantification. Despite the lack of studies related to the accuracy of the method it has been widely used. Here we present a simulation model for competitive PCR, which takes into account the efficiency decay as a linear relationship of the total product yield. The model helped us to study the kind and magnitude of errors that arise from quantitative and semiquantitative competitive PCR protocols and to find ways to minimize them. The simulation data suggest that differences in amplification efficiency between target and standard templates induce stronger biases in quantitative than in semiquantitative competitive PCR. Quantitative competitive PCR can only be used when both efficiencies are equal. In contrast, semiquantitative competitive PCR can be used even when the target is amplified with a higher efficiency than the standard, since under such conditions the method tends to underestimate the differences in initial DNA content. These predictions have been confirmed with experimental data and show that the estimation of the amplification efficiencies is a prerequisite for the use of quantitative and semiquantitative competitive PCR. A simple method for this estimation is also presented.

A novel doxycycline inducible autoregulatory plasmid which displays "on"/"off" regulation suited to gene therapy applications

The development of transcriptionally controlled systems which function in eukaryotic cells are important for achieving regulated gene expression in gene therapy. In this study we combined the components of the tetracycline-inducible system in self-contained retroviral and plasmid vectors. Regulated reporter gene expression from the autoregulatory plasmid pGTRTL in response to doxycycline (Dox) induction surpasses the expression observed from other self-contained retroviral and plasmid vectors. Induction kinetics and expression levels of luciferase and the therapeutic molecule, truncated soluble complement receptor 1 (sCR1) were characterised in a mouse fibroblast and a human neuroblastoma cell line. The regulatory characteristics of the plasmids were shown to be optimal for gene therapy applications, as there was a rapid reduction in expression levels following removal of Dox. Co-transfection of cells with an autoregulatory plasmid and a Dox inducible enhanced green fluorescent protein (EGFP) plasmid demonstrated the feasibility of using this plasmid combination to achieve parallel regulation of two genes of interest in a single cell under the control of Dox. These novel autoregulatory plasmids display the requirements for gene therapy applications in chronic conditions which are remitting/relapsing such as rheumatoid arthritis or multiple sclerosis, where novel protein therapeutics and combination therapies are needed. Gene Therapy (2000) 7, 2061-2070.

Immuno- and genetic therapy in autoimmune diseases

Animal models of autoimmune disease have been developed that mimic some aspects of the pathophysiology of human disease. These models have increased our understanding of possible mechanisms of pathogenesis at the molecular and cellular level and have been important in the testing, development and validation of new immunotherapies. The susceptibility to develop disease in the majority of these models is polygenic as is the case in humans. The exceptions to this rule are gene knock outs and transgenic models of particular genes which, in particular genetic backgrounds, have also contributed to the understanding of single gene function and their possible contribution to pathogenesis. Gene therapy approaches that target immune functions are being developed with encouraging results, despite the polygenic nature of these diseases. Basically this novel immuno-genetic therapy harnesses the knowledge of immunology with the myriad of biotechnological breakthroughs in vector design and delivery. Autoimmune disease is the result of genetic dysregulation which could be controlled by gene therapy. Here we summarize the genetic basis of these human diseases as well as some of the best characterized murine models. We discuss the strategies for their treatment using immuno- and gene therapy.

Different efficacy of in vivo herpes simplex virus thymidine kinase gene transduction and ganciclovir treatment on the inhibition of tumor growth of murine and human melanoma cells and rat glioblastoma cells

Initial studies have demonstrated the therapeutic efficacy for cancer treatment of in vivo transfer of the herpes simplex virus thymidine kinase gene followed by ganciclovir (GCV) treatment. However, recent studies have questioned the validity of this approach. Using retroviral vector-producing cells (VPC) as a source for in vivo gene transfer, we evaluated the efficacy of in vivo transduction of malignant cells using three different tumor cell models: B16 murine and IIB-MEL-LES human melanomas and a C6 rat glioblastoma. In vitro studies showed a bystander effect only in C6 cells. In vivo studies showed an inhibition of tumor growth in the two melanoma models when tumor cells were coinjected with VPC-producing retroviral vectors carrying the herpes simplex virus thymidine kinase gene, followed by GCV treatment; however, 100% of mice developed tumors in both models. Under similar experimental conditions, 70% (7 of 10) of syngeneic rats completely rejected stereotactically transferred C6 tumor cells; most of them (5 of 10) showed a prolonged survival. Treating established C6 tumors with VPC-producing retroviral vectors carrying the herpes simplex virus thymidine kinase gene and GCV led to the cure of 33% (4 of 12) of the animals. Rats that rejected tumor growth developed an antitumor immune memory, leading to a rejection of a stereotactic contralateral challenge with parental cells. The immune infiltrate, which showed the presence of T lymphocytes, macrophages, and polymorphonuclear cells at the site of the first injection and mainly T lymphocytes and macrophages at the site of tumor challenge, strengthened the importance of the immune system in achieving complete tumor rejection.

Prevention of collagen-induced arthritis by gene delivery of soluble p75 tumour necrosis factor receptor

Collagen type II-induced arthritis (CIA) in DBA/1 mice can be passively transferred to SCID mice with spleen B- and T-lymphocytes. In the present study, we show that infection ex vivo of splenocytes from arthritic DBA/1 mice with a retroviral vector, containing cDNA for the soluble form of human p75 receptor of tumour necrosis factor (TNF-R) before transfer, prevents the development of arthritis, bone erosion and joint inflammation in the SCID recipients. Assessment of IgG subclass levels and studies of synovial histology suggest that down-regulating the effector functions of T helper-type 1 (Th1) cells may, at least in part, explain the inhibition of arthritis in the SCID recipients. In contrast, the transfer of splenocytes infected with mouse TNF-alpha gene construct resulted in exacerbated arthritis and enhancement of IgG2a antibody levels. Intriguingly, infection of splenocytes from arthritic DBA/1 mice with a construct for mouse IL-10 had no modulating effect on the transfer of arthritis. The data suggest that manipulation of the immune system with cytokines, or cytokine inhibitors using gene transfer protocols can be an effective approach to ameliorate arthritis.

[Antitumor gene therapy using suicide genes]

Tumor cells transduced with retrovirus carrying the herpes simplex-1 virus thymidine kinase (HSV-tk) are capable of transforming the antiviral drug ganciclovir (GVC) into a metabolic form only toxic to dividing cells. The efficiency of this suicide gene therapy is increased by a "bystander" effect resulting not only in the death of the recipient cell, but also in the death of non modified surrounding cells. Even though the mechanism of this "bystander" effect remains to be elucidated, strong evidence suggest that the immune system plays a main role to achieve complete tumor eradication. In the present study we evaluate the efficiency of this suicide system on three different tumor models: one human melanoma, one murine melanoma, and a rat glioblastoma. Tumors were established by injection of tumor cells s.c. in nude and C57Bl/6 mice, respectively, and stereotactically into the brain of Sprague Dawley rats. Animals in the treated group were co-injected with packaging cells producing recombinant retrovirus carrying the HSV-tk gene, and followed by i.p. administration of GVC. In short term studies, we observed inhibition of tumor growth for all the tumor models evaluated (p < 0.01). In long term studies, using the C6 rat glioma line, 50% of the animals survived longer than 75 days (p < 0.0001), and were able to reject a contralateral challenges with C6 parental cells. Histological and immunohistochemical analysis showed the presence at an inflammatory infiltrate composed by T lymphocytes, macrophages and polymorphonuclear cells. These data demonstrate that suicide genes might represent an attractive form of cancer gene therapy in the treatment of brain tumors and their intracerebral dissemination.

Cytokine gene therapy in experimental allergic encephalomyelitis by injection of plasmid DNA-cationic liposome complex into the central nervous system

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease of the central nervous system with many similarities to multiple sclerosis. The main effector cells involved are CD4+ T cells, recognizing encephalitogenic epitopes within the central nervous system, and macrophages, both of which secrete proinflammatory cytokines, such as IFN-gamma and TNF. Studies have shown that immunomodulation of this inflammatory response by anti-inflammatory cytokines (IL-4, IL-10, IFN-beta, and TGF-beta) can reduce clinical severity in EAE. The importance of TNF in EAE has been demonstrated by using soluble TNF-receptor molecules to inhibit EAE. However, the limitation of this type of therapy is the necessity for frequent administration of cytokine proteins due to their short biologic half-life. This study demonstrates that EAE can be inhibited by a single injection of therapeutic cytokine (IL-4, IFN-beta, and TGF-beta) DNA-cationic liposome complex directly into the central nervous system. DNA coding for a novel, dimeric form of human p75 TNF receptor also ameliorated clinical EAE. Local administration of DNA-cationic liposome complex has identified gene targets that may be more efficiently exploited using vectors producing more stable expression for effective treatment of neuroimmunologic disease.

Gene therapy for rheumatoid arthritis. Theoretical considerations

Current understanding of the pathogenesis of rheumatoid arthritis has provided evidence that therapeutic benefit can be achieved by using antagonists targeted to the inflammatory cytokines involved, mainly tumour necrosis factor-alpha and interleukin-1. Gene delivery of antagonists, which can inhibit the production or action of these cytokines and other mediators, has been achieved in experimental animal models. This new method of delivery can produce therapeutic effects at lower concentrations and in a local environment, overcoming the adverse effects that often accompany protein therapy. However, several technological and biological restraints preclude the immediate adaptation of this method to human treatment. Based on the experimental evidence, possible target therapeutic genes, cell types and vector systems that could be used are discussed in this article.

Pathogenic lymphoid cells engineered to express TGF beta 1 ameliorate disease in a collagen-induced arthritis model

Collagen-induced arthritis in DBA/1 mice is a model of rheumatoid arthritis with marked synovitis and erosions. The disease can be adoptively transferred to SCID mice with arthritogenic splenocytes from DBA/1 mice injected with bovine collagen type II. However, infection of arthritogenic splenocytes with a retrovirus expressing TGF beta 1 inhibits development of arthritis in SCID mice. When DBA/1 mice, at onset of arthritis have additional arthritogenic splenocytes transferred, exacerbation occurs, reflected in a rapid increase in the number of arthritic joints, increased paw swelling and higher levels of anti-collagen antibody. By infecting arthritogenic splenocytes ex vivo with TGF beta 1 retrovirus, this exacerbation was inhibited. TGF beta 1 was effective in lowering inflammation of joints with already established arthritis and inhibiting the spreading of the disease to other joints. Transient reduction in anti-collagen antibody levels could also be obtained using purified T cells infected with TGF beta 1 retrovirus. In addition, expression of TGF beta 1 in lymphocytes reduced the levels of gelatinase (MMP2) activity in inflamed joints.

The expression of the secreted protein acidic and rich in cysteine (SPARC) is associated with the neoplastic progression of human melanoma

SPARC (secreted protein acidic and rich in cysteine) is an extracellular protein associated with tissues exhibiting high rates of cell proliferation and matrix remodeling. The current work shows that the human melanoma cell lines IIB-MEL-LES, IIB-MEL-IAN, and IIB-MEL-J and different human metastatic melanomas expressed high levels of SPARC mRNA and protein. By western blot analysis we detected a single secreted 42-kDa band in human diploid fibroblasts-conditioned medium and a 45- to 40-kDa doublet in the three melanoma cell lines and all the metastatic melanomas tested. Part of the melanoma samples and cell lines showed an additional doublet of 36-34 kDa. SPARC mRNA was expressed by the three established cell lines, 14 metastatic melanoma samples, and tumors raised in nude mice, and no spliced variants were found. The heterogeneous pattern of SPARC secreted by human melanoma cells is the result of post-translational glycosylation and a specific extracellular leupeptin-inhibitable cleavage. Unlike human fibroblasts, melanoma cells did not overexpress SPARC on addition of TGF-beta. Immunohistochemical analysis showed that SPARC was strongly expressed in 100% of primary melanomas (7 of 7) and metastatic melanomas (29 of 29), moderately expressed in most of the positive dysplastic nevi (13 of 14), and only weakly expressed in nevocellular nevi (4 of 25). Normal melanocytes did not express SPARC. The data suggest that the expression of SPARC is associated with the neoplastic progression of human melanoma.

Suppression of SPARC expression by antisense RNA abrogates the tumorigenicity of human melanoma cells

Acquisition of invasive/metastatic potential is a key event in tumor progression. Cell surface glycoproteins and their respective matrix ligands have been implicated in this process. Recent evidence reveals that the secreted glycoprotein SPARC (secreted protein, acidic and rich in cysteine) is highly expressed in different malignant tissues. The present study reports that the suppression of SPARC expression by human melanoma cells using a SPARC antisense expression vector results in a significant decrease in the in vitro adhesive and invasive capacities of tumor cells, completely abolishing their in vivo tumorigenicity. This is the first evidence that SPARC plays a key role in human melanoma invasive-metastatic phenotype development.

Tumor cells engineered to express interleukin-6 exhibit a reduced tumorigenicity depending on the tumor cell model

Cytokine gene transfer to tumor cells has been demonstrated to induce tumor rejection in different murine models. However, controversial results were presented for different cytokines. In order to study the antitumorigenic activity that has been proposed for IL-6, the poorly immunogenic melanoma B16 and the colon adenocarcinoma CT26-murine cell lines, were transduced with recombinant retrovirus expressing rat IL-6. In vivo studies showed that IL-6-producing-B 16 cells inoculated s.c. in syngeneic mice, exhibited reduced tumorigenicity compared to vector-transduced B 16 cells. The histology of growing IL-6-producing tumors showed a "pseudo-nodular" pattern which correlated with a strong inhibition of the in vitro invasive capacity of these cells. IL-6-producing-B 16 cells did not develop tumors in athymic nude mice suggesting that the antitumor effect is not mediated by a normal host-T- and B-cell response. In contrast, IL-6-producing CT26 cells grew as tumors in syngeneic mice with a faster growth rate than parental and vector-transduced cells, in accordance with an increased in vitro growth kinetics. These results indicate that IL-6 expression by tumor cells demonstrate different effects depending on the tumor cell model.

Inhibition of transfer of collagen-induced arthritis into SCID mice by ex vivo infection of spleen cells with retroviruses expressing soluble tumor necrosis factor receptor

Collagen-induced arthritis can be transferred into severe combined immunodeficiency (SCID) mice by spleen cells from diseased DBA/1 mice. The development of arthritis in SCID animals can be prevented by infection ex vivo of DBA/1 spleen cells with retroviruses expressing the monomeric soluble human p75 tumor necrosis factor (TNF) receptor (TNF-R). In addition, a vector engineered to express a polycystronic mRNA with TNF-R and the herpes simplex virus thymidine kinase (HSVtk) gene, while producing low levels of TNF-R, had a limited effect which could be blocked by treating the animals with ganciclovir. A retroviral vector expressing the HSVtk gene alone had no effect on this arthritis transfer model with or without ganciclovir. Serum levels of TNF-R did not correlate with clinical signs, however, lower anti-collagen antibody levels corresponded with lack of clinical symptoms. These results indicate that local production of cytokine inhibitor is essential for therapeutic purposes while systemic levels may not be required.

Biologic, immunocytochemical, and cytogenetic characterization of two new human melanoma cell lines: IIB-MEL-LES and IIB-MEL-IAN

Two human melanoma cell lines, derived from metastases of two patients with epithelioid malignant amelanotic melanomas, and designated IIB-MEL-LES and IIB-MEL-IAN, have been established. Both cell lines have been in continuous culture over 2 years and were propagated continuously for 85 and 75 serial passages, respectively. Morphologically, IIB-MEL-LES is composed predominantly of spindle shaped cells, whereas IIB-MEL-IAN grows as a monolayer of cuboid and stellate shaped cells with many rounded cells in suspension. Immunocytochemical studies revealed that both cell lines express S-100 protein, vimentin, and GD3 and GD2 gangliosides but are negative for keratin and collagen. Both cell lines express HLA class I and HLA-DR antigens in variable proportions. The MAGE-1 gene is expressed only by the IIB-MEL-IAN cell line, as revealed by PCR analysis. Cytogenetic analysis of both cell lines revealed abnormal karyotypes; the modal chromosome numbers of IIB-MEL-LES and IIB-MEL-IAN were 48 and 81, respectively. IIB-MEL-LES cells presented rearrangements in chromosomes 1, 14 and X, gains in chromosomes 10, 20, and 21 losses in chromosomes 15 and Y. The most frequent markers observed in IIB-MEL-IAN cells were 7q+, 10p+, 2p+, i(6p), 2q+, and 10q-. Clonal gains were observed in chromosomes 12 and 21, whereas losses were seen in chromosomes 1, 2, 3, 4, 6, 7, 11, and 17. Both cell lines were capable of forming colonies in soft agar and developed tumors when transplanted into nude mice, reproducing and maintaining the characteristics of the original tumors. These cell lines and their xenografts appear to provide useful systems for studying the biology, genetics and histogenesis of human malignant melanoma and could be utilized for the development of melanoma vaccines.

Expression of cathepsin D in primary and metastatic human melanoma and dysplastic nevi

High levels of cytosolic cathepsin D expression have been associated with poor prognosis in breast cancer node-negative patients. In this work, we provide evidence that three cell lines established from human metastatic melanomas--IIB-MEL-J, IIB-MEL-LES, and IIB-MEL-IAN--express high levels of procathepsin D mRNA. IIB-MEL-J cells secreted into the conditioned media about 30% of the newly synthesized protein, which was active at acidic pH. Melanoma tumors arising in nude mice after injection of the three different cell lines expressed high levels of procathepsin D mRNA. Moreover, 13 human metastatic melanomas expressed variable levels of procathepsin D mRNA. To study the possible association between cathepsin D expression and melanoma development, samples corresponding to 10 primary tumors, 11 metastatic melanomas, 10 dysplastic nevi, 27 nevocellular nevi, and normal melanocytes were studied by immunohistochemistry for cathepsin D-specific staining. We found that cathepsin D was expressed in all of the dysplastic nevi and primary and metastatic melanomas tested but in only 18% of nevocellular nevi (five of 27), whereas normal melanocytes showed no cathepsin D expression. The overall data indicate that cathepsin D is expressed at a high level by melanoma cells, and because of its expression in preneoplastic lesions, it may be associated with melanoma development.

A novel metalloproteinase gene specifically expressed in stromal cells of breast carcinomas

A gene has been identified that is expressed specifically in stromal cells surrounding invasive breast carcinomas. On the basis of its sequence, the product of this gene, named stromelysin-3, is a new member of the family of metalloproteinase enzymes which degrade the extracellular matrix. The suggestion is that stromelysin-3 is one of the stroma-derived factors that have long been postulated to play an important part in progression of epithelial malignancies.

Effect of estradiol and tamoxifen on the anchorage-independent growth of the subpopulations derived from MCF-7 breast carcinoma cells: cytogenetic analysis of the stem cell subpopulation

The MCF-7 breast carcinoma cell line can be separated by Percoll density gradient centrifugation into several subpopulations, A to F, one of which (E) has been previously suggested to be highly enriched in stem cells. The anchorage-independent growth of the different fractions and its sensitivity to estradiol (E2) and tamoxifen (TAM) was assayed. The anchorage-independent growth capacity of the different fractions was E greater than A greater than B greater than D greater than C,F. The E fraction had the highest clonogenic index (6.62 +/- 1.18) and was unaffected by E2 or TAM. The karyotypic analysis of the E fraction revealed features similar to those of the unfractionated cell line. It is suggested that the high growth rate of fraction E is due to an enrichment in stem cells and not to the existence of a different clone.

In vitro analysis of the cellular proliferative response to 17-beta-estradiol of human breast cancer

In human breast cancer the proliferating cells appear to differ from those containing estrogen receptors (ER) as shown by studies on isolated cellular subpopulations. In this paper the in vitro effect of 17-beta-estradiol on cell proliferation in 30 primary breast tumors was studied. The effect of several estradiol concentrations was assayed, and the influence of diethylstilbestrol, tamoxifen, and nafoxidine was also tested. The response to these compounds was measured through the thymidine labeling index (TLI). When exposed to 10(-9) mol/l and 10(-8) mol/l estradiol, 14 of 19 ER-positive tumors and six of 11 ER-negative tumors were induced to further proliferate. The TLI increase over the control was 219% (P less than 0.05) at 10(-9) mol/l E2 and 258% (P less than 0.05) at 10(-8) mol/l E2 for ER-positive tumors, and 233% (0.1 less than P less than 0.2) at 10(-9) mol/l E2 and 321% (0.1 less than P less than 0.2) at 10(-8) mol/l E2 for ER-negative tumors. The addition of diethylstilbestrol and antiestrogens in vitro inhibited, to varying degrees, the estradiol-induced increase in the TLI irrespective of the ER-status. The response to E2 was correlated with the expression of the ras p21 protein and carcinoembryonic antigen. It was found that the ras p21 protein is preferentially expressed in ER-negative tumors, the opposite being true for carcinoembryonic antigen. The ras p21 protein is preferentially expressed in those ER-positive tumors that do not respond to estradiol with an increase in the TLI.

Subpopulations of MCF7 cells separated by Percoll gradient centrifugation: a model to analyze the heterogeneity of human breast cancer

Exponentially growing MCF7 human breast cancer cells were separated in Percoll gradients into six different fractions of increasing density (A to F). These fractions could be subcultured and were found to contain different cellular subpopulations as defined by the following criteria: ability to generate other cellular subpopulations; growth rate; DNA synthesis; and expression of estrogen receptors, ras oncogene-encoded protein p21, and carcinoembryonic antigen. One of the minor fractions (E), which contained about 5% of the total cell number, appeared to contain the stem cells, on the basis of the following criteria: (i) its ability to reproduce the other cellular subpopulations, (ii) its high rate of growth and DNA synthesis, and (iii) the inability of the other subpopulations to generate it. The most differentiated subpopulation appeared to be the densest one (F), since it was the slowest growing and appeared to be the end point of the other subpopulations.

Determination of DNA synthesis, estrogen receptors, and carcinoembryonic antigen in isolated cellular subpopulations of human breast cancer

Primary breast adenocarcinomas obtained from ten patients were enzymatically digested using collagenase (1 mg/ml), hyaluronidase (1 mg/ml), elastase (0.1 mg/ml) and DNAse (0.2 mg/ml). The tumor cells were labeled with 3H-thymidine and, in some cases, with 3H-estradiol. The isolated cells were submitted successively to a Ficoll-Hypaque and a bovine serum albumin gradient, from which 12 fractions were obtained. In each fraction, several characteristics were determined: carcinoembryonic antigen (CEA), thymidine (dThd) incorporation, and estrogen receptors (ER). Three main cellular subpopulations were characterized: An intermediate density subpopulation (1.046-1.054 g/ml), in which the proliferating cells are concentrated. In this subpopulation a small number of CEA-positive cells are present, but ER containing cells are virtually absent. A high-density, small cell subpopulation that concentrates most of the ER-containing cells. This subpopulation lacks proliferating cells, but CEA-containing cells are abundant. A low-density subpopulation, lacking proliferating cells and with scarce ER-positive cells, although CEA-positive cells are frequent. These findings strongly suggest that proliferating cells lack ER.

Characterization of lysosomal acid phosphatase from normal and malignant mammary tissue

Acid phosphatase (EC 3.1.3.2) isoenzyme 3 was purified from normal and malignant human mammary tissue and its properties in each were compared. The relative molecular mass of each was 53 000, as measured by sodium dodecyl sulfate gel electrophoresis. Several phosphomonoesters are good substrates for the isoenzymes, whereas organic and inorganic pyrophosphates and phosphoryl choline are hydrolyzed very slowly or not detectably. The optimum pH for interaction of these isoenzymes with p-nitrophenyl phosphate as substrate ranges from 3.5 to 4.5. L-(+)-Tartrate is a very strong inhibitor, Ki = 0.028 +/- 0.04 mmol/L (mean +/- SE), as are mercuric and fluoride ions in low concentrations. We conclude that type 3 isoenzymes obtained from normal and malignant tissue are very similar, though the malignant tissue appears to have a greater proportion of this type than does normal tissue.

Characterization of lysosomal acid phosphatase from normal and malignant mammary tissue

Acid phosphatase (EC 3.1.3.2) isoenzyme 3 was purified from normal and malignant human mammary tissue and its properties in each were compared. The relative molecular mass of each was 53 000, as measured by sodium dodecyl sulfate gel electrophoresis. Several phosphomonoesters are good substrates for the isoenzymes, whereas organic and inorganic pyrophosphates and phosphoryl choline are hydrolyzed very slowly or not detectably. The optimum pH for interaction of these isoenzymes with p-nitrophenyl phosphate as substrate ranges from 3.5 to 4.5. L-(+)-Tartrate is a very strong inhibitor, Ki = 0.028 +/- 0.04 mmol/L (mean +/- SE), as are mercuric and fluoride ions in low concentrations. We conclude that type 3 isoenzymes obtained from normal and malignant tissue are very similar, though the malignant tissue appears to have a greater proportion of this type than does normal tissue.

A prostatic-like acid phosphatase is present in human lactating milk

The presence of a prostatic-like acid phosphatase is reported in human lactating milk. Its activity is associated with skim milk and it could be separated from the other acid phosphatases only after Triton X-100 treatment. By all the criteria applied, it appears to be very similar to prostatic acid phosphatase. An approximate molecular weight of 96 000 was measured for the native enzyme, which is inhibited by L-(+)tartrate and has similar electrophoretic migration. Besides, it hydrolyzes choline-o-phosphate very well and cross-reacts with an antibody anti-prostatic acid phosphatase. This prostatic-like acid phosphatase has also been detected in a human mammary carcinoma from a lactating patient.

A high-molecular weight complex with acid phosphatase activity in human breast cancer

The presence of a high-molecular weight complex with acid phosphatase activity in the cytosol of human mammary tumors is reported. This complex appeared in the cytosol after tissue homogenization in the presence of dithiotreitol, with or without Triton X-100 and at acidic or neutral pH. Upon gel electrophoresis, this fraction showed only one band of enzyme activity which did not enter the fine pore gel. Lubrol or n-butanol had no apparent effect on this complex, and 8 M urea or 2% sodium dodecyl sulfate did not disaggregate this large molecule. After purification by gel filtration, ammonium sulfate precipitation and ion-exchange chromatography an apparent molecular weight or 10(6) was measured. It hydrolyzed typical acid phosphatase substrates such as p-NPP and alpha-NP, but also ATP and PPi. Only 44% inhibition was observed with L-(+)tartrate and it was still 40% active after 1 hr incubation at 60 degrees C. Reduction in the presence of SDS yielded several polypeptide bands. It was also detected in some samples of normal mammary tissues, but not in normal human placenta or liver.

Acid phosphatase in human breast cancer tissue

When the total acid phosphatase (AP) activity of mammary carcinoma was compared with those of benign pathology and normal mammary tissue the results showed statistically significant differences (P less than 0.05) when expressed per milligram of protein: 358 +/- 42 nmoles per hour (mean +/- standard error) in the malignant tumor, 216 +/- 30 in the benign pathology, and 96 +/- 45 in normal tissue and when expressed per milligram of DNA: 1858 +/- 234, 1227 +/- 140, 695 +/- 345 nmoles per hour, respectively. The polyacrylamide gel electrophoretic profiles showed different levels of isoenzymes 3 and 4 in the three tissue groups. The appearance of isoenzyme 1 is reported after treatment of the homogenates with 5% Triton X-100. It was also found by counterimmunoelectrophoresis that the 28,000 Xg mammary tumor supernatant cross reacts with an antiserum raised against AP isoenzyme 2 although the mammary tissue does not contain such an isoenzyme. To elucidate this point, isoenzymes 1, 3 and 4 were separated by columns of Sephadex G-200 and DEAE-Sephadex. By counterimmunoelectrophoresis, it was observed that only the fraction containing isoenzyme 4 cross-reacted with the antiserum anti-AP isoenzyme 2 maintaining the catalytic activity.

Effect of liposome-encapsulated quercetin on DNA synthesis, lactate production, and cyclic adenosine 3':5'-monophosphate level in Ehrlich ascites tumor cells

Quercetin (3,3',4',5,7-pentahydroxyflavone) entrapped within phospholipid vesicles inhibited [3H]thymidine incorporation and lactate production in Ehrlich ascites tumor cells. The presence of serum proteins in concentrations of up to 40 mg/ml did not alter the extent of the inhibitory effect of the liposome-entrapped flavone. At the same concentrations, serum proteins eliminated almost completely the inhibitory effects of the free quercetin on these metabolic processes. Prolonged sonication and different lipid compositions of the liposomes did not increase the inhibition of [3H]thymidine incorporation by the entrapped quercetin in the presence of serum albumin. On the other hand, serum albumin eliminated the elevation of the cyclic adenosine 3':5'-monophosphate level in these cells produced by both free and liposome-entrapped flavone. Attachment between Ehrlich ascites tumor cells and quercetin-loaded liposomes is demonstrated in negatively stained electron micrographs. The liposomes ranged in size from 50 to 100 nm. After 10 min of incubation, these liposomes were distributed randomly on the cell surface at distances of 100 to 200 nm.