Characterization of F3II, a sarcomatoid mammary carcinoma cell line originated from a clonal subpopulation of a mouse adenocarcinoma

Age-associated microenvironmental changes highlight the role of PDGF-C in ER+ breast cancer metastatic relapse

Patients with estrogen receptor (ER)-positive breast cancer are at risk of metastatic relapse for decades after primary tumor resection and treatment, a consequence of dormant disseminated tumor cells (DTCs) reawakening at secondary sites. Here we use syngeneic ER⁺ mouse models in which DTCs display a dormant phenotype in young mice but accelerated metastatic outgrowth in an aged or fibrotic microenvironment. In young mice, low-level Pdgfc expression by ER⁺ DTCs is required for their maintenance in secondary sites but is insufficient to support development of macrometastases. By contrast, the platelet-derived growth factor (PDGF)-C^hi environment of aging or fibrotic lungs promotes DTC proliferation and upregulates tumor cell Pdgfc expression stimulating further stromal activation, events that can be blocked by pharmacological inhibition of PDGFRα or with a PDGF-C-blocking antibody. These results highlight the role of the changing microenvironment in regulating DTC outgrowth and the opportunity to target PDGF-C signaling to limit metastatic relapse in ER⁺ breast cancer.

PEGylation of genistein-loaded bovine serum albumin nanoparticles and its effect on in vitro cell viability and genotoxicity properties

Self-assembled bovine serum albumin nanoparticles loaded with the isoflavone genistein have shown apoptosis-mediated cytotoxicity against murine mammary adenocarcinoma F3II cells. Due to their protein nature and small particle size (13-15 nm), their parenteral administration could be affected by possible immunogenic reactions and rapid clearance from the bloodstream. To avoid these problems, PEGylation of the systems was achieved in this work by using a 30 kDa methoxy-polyethylene glycol carbonyl imidazole derivative through the reaction between the carbonyl imidazole group and the amino groups of Lys residues on the protein surface, which was confirmed by a 17% reduction in the available amino groups content measured by the o-phthaldialdehyde method. PEGylated isoforms were obtained, showing an increase of particle size from 13 to 15 nm to around 260 nm, and were purified by SEC-FPLC and characterized by SDS-PAGE, DLS and AFM techniques. The effect of PEGylation on BSAnp-Gen cytotoxicity and genotoxicity against F3II cells was evaluated in vitro by MTT assay, flow cytometry analysis and micronucleus assay. From the results, PEGylation produced an improvement of the biological properties of genistein-loaded nanoparticles in terms of cytotoxicity (lower IC₅₀), not affecting the induction of apoptosis, decreasing the genotoxicity of the systems (less induction of micronucleus formation).

Murine Mammary Carcinoma Induces Chronic Systemic Inflammation and Immunosuppression in BALB/c Mice

Purpose

Methods

Results

Conclusion

Yerba Mate Modulates Tumor Cells Functions Involved in Metastasis in Breast Cancer Models

Breast cancer (BC) is the most frequent cancer in women and tumor metastasis is a major cause of cancer-related deaths. Our aim was to evaluate anti-metastatic properties of yerba mate extract (YMe) in BC models. 4T1, F3II, MCF-7, and MDA-MB231 cell lines were used to perform in vitro assays. The F3II syngeneic mammary carcinoma model in BALB/c mice was used to evaluate tumor progression, BC metastasis and survival. Cells were inoculated subcutaneously into the flank for the heterotopic model and into the mammary fat pad for the orthotopic model. YMe was administered p.o. in a dose of 1.6 g/kg/day. In vitro YMe inhibited cell proliferation and reduced tumor cell adhesion, migration and invasion. These biological effects were cell-line dependent. In vivo YMe reduced tumor metastasis and increased mice survival in both models. Our preclinical results suggest that YMe could modulate tumor progression and metastasis in BC models.

Breast cancer dormancy: need for clinically relevant models to address current gaps in knowledge

Breast cancer is the most commonly diagnosed cancer in the USA. Although advances in treatment over the past several decades have significantly improved the outlook for this disease, most women who are diagnosed with estrogen receptor positive disease remain at risk of metastatic relapse for the remainder of their life. The cellular source of late relapse in these patients is thought to be disseminated tumor cells that reactivate after a long period of dormancy. The biology of these dormant cells and their natural history over a patient's lifetime is largely unclear. We posit that research on tumor dormancy has been significantly limited by the lack of clinically relevant models. This review will discuss existing dormancy models, gaps in biological understanding, and propose criteria for future models to enhance their clinical relevance.

Genistein loaded in self-assembled bovine serum albumin nanovehicles and their effects on mouse mammary adenocarcinoma cells

Antitumor activity of plant-derived flavonoids has been researched during recent decades. Among them, genistein (Gen) stands out for showing cytotoxic activity against breast cancer cells. However, its low water solubility, limited bioavailability, and fast metabolism hinder its administration in chemopreventive therapies. To overcome these obstacles, bovine serum albumin nanovehicles (BSAnp) were obtained by a heat-induced self-assembly process at 70 °C and two aqueous medium pH (9.0 and 11.0) and assayed for the Gen loading. Thus, in this work, Gen loading in BSAnp was studied by spectroscopic techniques and compared with the one obtained for its stereoisomer, chrysin (Chrys). Results revealed that Gen binds to BSAnp via fluorescence quenching mechanism forming inclusion complexes. Compared to Chrys, Gen binding to BSAnp involved more molecules, whereas the association constant was similar for both flavonoids. In general, flavonoid loading in protein systems was strongly affected by the combined effects of BSA conformational state (native vs. aggregated), nanovehicle size, and flavonoid chemical structure. To evaluate the antitumor properties freeze-dried powders were obtained, and they were assayed in vitro after reconstitution by XTT technique and Annexin V-FITC flow cytometry against mouse mammary adenocarcinoma F3II cells. Gen-loaded BSAnp produced a significant decrease in cell viability compared with unloaded BSAnp systems, being the highest cytotoxic effects found for the lowest sized Gen-loaded BSAnp. The leading cytotoxicity mechanism for Gen-loaded systems was apoptosis. Summarizing, it can be concluded that BSAnp constitute versatile nanovehicles for potential flavonoid incorporation in pharmaceutical and nutraceutical matrices.

Preclinical efficacy of CIGB-300, an anti-CK2 peptide, on breast cancer metastasic colonization

CK2 is a serine/threonine kinase that is overexpressed in breast cancer and its inhibition is associated to reduced tumor growth and disease progression. CIGB-300 is an antitumor peptide with a novel mechanism of action, since it binds to protein kinase CK2 catalytic subunit alpha and to CK2 substrates thus preventing the enzyme activity. Our aim was to evaluate the potential therapeutic benefits of CIGB-300 on breast cancer disease using experimental models with translational relevance. We demonstrated that CIGB-300 reduces breast cancer cell growth in MDA-MB-231, MCF-7 and F3II cells, exerting a pro-apoptotic action and cell cycle arrest. We also found that CIGB-300 decreased cell adhesion, migration and clonogenic capacity of malignant cells. Effect on experimental breast cancer lung metastasis was evaluated after surgical removal of primary F3II tumors or after tail vein injection of tumor cells, also we evaluated CIGB-300 effect on spontaneous lung metastasis in an orthotopic model. Systemic CIGB-300 treatment inhibited breast cancer colonization of the lung, reducing the size and number of metastatic lesions. The present preclinical study establishes for the first time the efficacy of CIGB-300 on breast cancer. These encouraging results suggest that CIGB-300 could be used for the management of breast cancer as an adjuvant therapy after surgery, limiting tumor metastatic spread and thus protecting the patient from distant recurrence.

Efficacy of direct current generated by multiple-electrode arrays on F3II mammary carcinoma: experiment and mathematical modeling

Background

The modified Gompertz equation has been proposed to fit experimental data for direct current treated tumors when multiple-straight needle electrodes are individually inserted into the base perpendicular to the tumor long axis. The aim of this work is to evaluate the efficacy of direct current generated by multiple-electrode arrays on F3II mammary carcinoma that grow in the male and female BALB/c/Cenp mice, when multiple-straight needle electrodes and multiple-pairs of electrodes are inserted in the tumor.

Methods

A longitudinal and retrospective preclinical study was carried out. Male and female BALB/c/Cenp mice, the modified Gompertz equation, intensities (2, 6 and 10 mA) and exposure times (10 and 20 min) of direct current, and three geometries of multiple-electrodes (one formed by collinear electrodes and two by pair-electrodes) were used. Tumor volume and mice weight were measured. In addition, the mean tumor doubling time, tumor regression percentage, tumor growth delay, direct current overall effectiveness and mice survival were calculated.

Results

The greatest growth retardation, mean doubling time, regression percentage and growth delay of the primary F3II mammary carcinoma in male and female mice were observed when the geometry of multiple-pairs of electrodes was arranged in the tumor at 45, 135, 225 and 325^o and the longest exposure time. In addition, highest direct current overall effectiveness (above 66%) was observed for this EChT scheme.

Conclusions

It is concluded that electrochemical therapy may be potentially addressed to highly aggressive and metastic primary F3II murine mammary carcinoma and the modified Gompertz equation may be used to fit data of this direct current treated carcinoma. Additionally, electrochemical therapy effectiveness depends on the exposure time, geometry of multiple-electrodes and ratio between the direct current intensity applied and the polarization current induced in the tumor.

Computational and in vitro Pharmacodynamics Characterization of 1A-116 Rac1 Inhibitor: Relevance of Trp56 in Its Biological Activity

In the last years, the development of new drugs in oncology has evolved notably. In particular, drug development has shifted from empirical screening of active cytotoxic compounds to molecularly targeted drugs blocking specific biologic pathways that drive cancer progression and metastasis. Using a rational design approach, our group has developed 1A-116 as a promising Rac1 inhibitor, with antitumoral and antimetastatic effects in several types of cancer. Rac1 is over activated in a wide range of tumor types and and it is one of the most studied proteins of the Rho GTPase family. Its role in actin cytoskeleton reorganization has effects on endocytosis, vesicular trafficking, cell cycle progression and cellular migration. In this context, the regulatory activity of Rac1 affects several key processes in the course of the cancer including invasion and metastasis. The purpose of this preclinical study was to focus on the mode of action of 1A-116, conducting an interdisciplinary approach with in silico bioinformatics tools and in vitro assays. Here, we demonstrate that the tryptophan 56 residue is necessary for the inhibitory effects of 1A-116 since this compound interferes with protein-protein interactions (PPI) of Rac1GTPase involving several GEF activators. 1A-116 is also able to inhibit the oncogenic Rac1^P29S mutant protein, one of the oncogenic drivers found in sun-exposed melanoma. It also inhibits numerous Rac1-regulated cellular processes such as membrane ruffling and lamellipodia formation. These results deepen our knowledge of 1A-116 inhibition of Rac1 and its biological impact on cancer progression. They also represent a good example of how in silico analyses represent a valuable approach for drug development.

Genistein-triggered anticancer activity against liver cancer cell line HepG2 involves ROS generation, mitochondrial apoptosis, G2/M cell cycle arrest and inhibition of cell migration

INTRODUCTION

Liver cancer is one of the most common malignancies across the globe and one of the major causes of cancer-related mortality. With limited available treatment options, there is an urgent need to look for new available options. Genistein is an important plant flavonoid and has been shown to possess tremendous pharmacological potential. The objective of the present study was therefore to evaluate the anticancer effect of the genistein.

MATERIAL AND METHODS

The antiproliferative activity and IC₅₀ of genistein were determined by MTT assay. Reactive oxygen species (ROS) and cycle distribution were investigated by flow cytometry. Apoptosis was detected by DAPI and annexin V/IP staining. Cell migration was investigated by wound healing assay. Protein expression was estimated by western blotting.

RESULTS

MTT assay revealed that genistein reduced the cell viability of HepG2 cancer cells in a dose-dependent manner. Genistein also reduced the colony forming potential of the HepG2 cell concentration dependently. The IC₅₀ of genistein was found to be 25 μM. Genistein caused G2/M cell cycle arrest and G2/M cells increased from 4.2% in the control to 56.4% at 100 μM concentration. Genistein prompted generation of significant (p < 0.01) amounts of ROS, ultimately favouring cell death. Genistein also triggered apoptosis which was associated with upregulation of cytosolic cytochrome c, Bax, cleaved caspase 3 and 9 expression and downregulation of Bcl-2 expression in HepG2 cells.

CONCLUSIONS

We propose that genistein exhibits significant anticancer activity against liver cancer and therefore may prove beneficial in the management of liver cancer.

Dose-response study for the highly aggressive and metastatic primary F3II mammary carcinoma under direct current

Electrochemical treatment has been suggested as an effective alternative to local cancer therapy. Nevertheless, its effectiveness decreases when highly aggressive primary tumors are treated. The aim of this research was to understand the growth kinetics of the highly aggressive and metastatic primary F3II tumor growing in male and female BALB/c/Cenp mice under electrochemical treatment. Different amounts of electric charge (6, 9, and 18 C) were used. Two electrodes were inserted into the base, perpendicular to the tumor's long axis, keeping about 1 cm distance between them. Results have shown that the F3II tumor is highly sensitive to direct current. The overall effectiveness (complete response + partial response) of this physical agent was ≥75.0% and observed in 59.3% (16/27) of treated F3II tumors. Complete remission of treated tumors was observed in 22.2% (6/27). An unexpected result was the death of 11 direct current-treated animals (eight females and three males). It is concluded that direct current may be addressed to significantly affect highly aggressive and metastatic primary tumor growth kinetics, including the tumor complete response. Bioelectromagnetics. 39:460-475, 2018. © 2018 Wiley Periodicals, Inc.

Anticancer activity of caffeic acid n‑butyl ester against A431 skin carcinoma cell line occurs via induction of apoptosis and inhibition of the mTOR/PI3K/AKT signaling pathway

Skin cancer is one of the primary causes of mortality worldwide. With an increasing frequency of skin cancers, there is an urgent requirement for the development of numerous treatment options. The present study investigated the anticancer activity of caffeic acid n-butyl ester (CAE) against the A431 skin cancer cell line. Antiproliferative effects were investigated using an MMT assay. Apoptosis was examined by DAPI and Annexin V/fluorescein isothiocyanate and propidium iodide staining. Reactive oxygen species (ROS), mitochondrial membrane potential (MMP) and cell cycle analyses were performed via flow cytometry. Protein expression was determined by western blotting. The findings of the present study demonstrated that among a variety of cancer cell lines, CAE exhibited significant anticancer activity against the A431 skin cancer cell line with a half-maximal inhibitory concentration of 20 µM. CAE was associated with apoptosis and cell cycle arrest of A431 cells, and induced ROS-mediated alterations in MMP. In addition, CAE considerably suppressed the expression of some of the important proteins of the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mechanistic target of rapamycin (mTOR) cascade. The results of the present study indicated that CAE exerted anticancer effects on the A431 skin carcinoma cell line via the induction of apoptosis and suppression of the PI3K/AKT/mTOR signaling pathway. Therefore, CAE may be beneficial for the development of chemotherapy for skin cancers.

Quantitation of TGF-β proteins in mouse tissues shows reciprocal changes in TGF-β1 and TGF-β3 in normal vs neoplastic mammary epithelium

Transforming growth factor-βs (TGF-βs) regulate tissue homeostasis, and their expression is perturbed in many diseases. The three isoforms (TGF-β1, -β2, and -β3) have similar bioactivities in vitro but show distinct activities in vivo. Little quantitative information exists for expression of TGF-β isoform proteins in physiology or disease. We developed an optimized method to quantitate protein levels of the three isoforms, using a Luminex® xMAP®-based multianalyte assay following acid-ethanol extraction of tissues. Analysis of multiple tissues and plasma from four strains of adult mice showed that TGF-β1 is the predominant isoform with TGF-β2 being ~10-fold lower. There were no sex-specific differences in isoform expression, but some tissues showed inter-strain variation, particularly for TGF-β2. The only adult tissue expressing appreciable TGF-β3 was the mammary gland, where its levels were comparable to TGF-β1. In situ hybridization showed the luminal epithelium as the major source of all TGF-β isoforms in the normal mammary gland. TGF-β1 protein was 3-8-fold higher in three murine mammary tumor models than in normal mammary gland, while TGF-β3 protein was 2-3-fold lower in tumors than normal tissue, suggesting reciprocal regulation of these isoforms in mammary tumorigenesis.

ANTICANCER ACTIVITY OF 5, 7-DIMETHOXYFLAVONE AGAINST LIVER CANCER CELL LINE HEPG2 INVOLVES APOPTOSIS, ROS GENERATION AND CELL CYCLE ARREST

BACKGROUND

Flavonoids are considered potential anticancer agents owing to their properties to interact with a diversity of cellular entities. Among flavonoids, methylated flavones are more efficient anticancer agents due to their higher stability in vivo. The purpose of the present study was, therefore, to evaluate the anticancer effect of methylated natural flavonoid 5, 7-dimethoxyflavone (5, 7-DMF).

MATERIALS AND METHODS

MTT assay was used to determine the anticancer activity and IC₅₀ of 5, -DMF). Cell viability, cell cycle distribution, reactive oxygen species (ROS) and mitochondrial membrane potential (ΔΨm) were carried out by flow cytometry. Apoptosis was studied by DAPI staining.

RESULTS

MTT assay revealed that the molecule reduced the cell viability of HepG2 cancer cells. The IC₅₀ of 5, 7-DMF was found to be 25 µM. Our result indicated that 5, 7-DMF triggered production of ROS and significantly reduced ΔΨ_m . It also leads to arrest of HepG2 cells in Sub-G1 stage of cell cycle, and ultimately induced apoptosis in a concentration-dependent manner, as indicated by DAPI staging. Additionally, 5, 7-DMF also reduced the colony forming potential of the HepG2 cells concentration dependently.

CONCLUSION

Taken together, we conclude that 5, 7-DMF induces cell death via ROS generation, cell cycle arrest and apoptosis, and, therefore, may prove beneficial in the treatment of liver cancer.

Immunocompetent mouse allograft models for development of therapies to target breast cancer metastasis

Effective drug development to combat metastatic disease in breast cancer would be aided by the availability of well-characterized preclinical animal models that (a) metastasize with high efficiency, (b) metastasize in a reasonable time-frame, (c) have an intact immune system, and (d) capture some of the heterogeneity of the human disease. To address these issues, we have assembled a panel of twelve mouse mammary cancer cell lines that can metastasize efficiently on implantation into syngeneic immunocompetent hosts. Genomic characterization shows that more than half of the 30 most commonly mutated genes in human breast cancer are represented within the panel. Transcriptomically, most of the models fall into the luminal A or B intrinsic molecular subtypes, despite the predominance of an aggressive, poorly-differentiated or spindled histopathology in all models. Patterns of immune cell infiltration, proliferation rates, apoptosis and angiogenesis differed significantly among models. Inherent within-model variability of the metastatic phenotype mandates large cohort sizes for intervention studies but may also capture some relevant non-genetic sources of variability. The varied molecular and phenotypic characteristics of this expanded panel of models should aid in model selection for development of antimetastatic therapies in vivo, and serve as a useful platform for predictive biomarker identification.

Addition of vasopressin synthetic analogue [V(4)Q(5)]dDAVP to standard chemotherapy enhances tumour growth inhibition and impairs metastatic spread in aggressive breast tumour models

[V(4)Q(5)]dDAVP is a novel 2nd generation vasopressin analogue with robust antitumour activity against metastatic breast cancer. We recently reported that, by acting on vasopressin V2r membrane receptor present in tumour cells and microvascular endothelium, [V(4)Q(5)]dDAVP inhibits angiogenesis and metastatic progression of the disease without overt toxicity. Despite chemotherapy remaining as a primary therapeutic option for aggressive breast cancer, its use is limited by low selectivity and associated adverse effects. In this regard, we evaluated potential combinational benefits by adding [V(4)Q(5)]dDAVP to standard-of-care chemotherapy. In vitro, combination of [V(4)Q(5)]dDAVP with sub-IC50 concentrations of paclitaxel or carmustine resulted in a cooperative inhibition of breast cancer cell growth in comparison to single-agent therapy. In vivo antitumour efficacy of [V(4)Q(5)]dDAVP addition to chemotherapy was first evaluated using the triple-negative MDA-MB-231 breast cancer xenograft model. Tumour-bearing mice were treated with i.v. injections of [V(4)Q(5)]dDAVP (0.3 μg/kg, thrice weekly) in combination with weekly cycles of paclitaxel (10 mg/kg i.p.). After 6 weeks of treatment, combination regimen resulted in greater tumour growth inhibition compared to monotherapy. [V(4)Q(5)]dDAVP addition was also associated with reduction of local aggressiveness, and impairment of tumour invasion and infiltration of the skin. Benefits of combined therapy were confirmed in the hormone-independent and metastatic F3II breast cancer model by combining [V(4)Q(5)]dDAVP with carmustine (25 mg/kg i.p.). Interestingly, [V(4)Q(5)]dDAVP plus cytotoxic agents severely impaired colony forming ability of tumour cells and inhibited breast cancer metastasis to lung. The present study shows that [V(4)Q(5)]dDAVP may complement conventional chemotherapy by modulating metastatic progression and early stages of microtumour establishment, and thus supports further preclinical testing of the compound for the management of aggressive breast cancer.

Experimental studies of a vaccine formulation of recombinant human VEGF antigen with aluminum phosphate

CIGB-247 is a cancer vaccine that is a formulation of a recombinant protein antigen representative of the human vascular endothelial growth factor (VEGF) with a bacterially-derived adjuvant (VSSP). The vaccine has shown an excellent safety profile in mice, rats, rabbits, not-human primates and in recent clinical trials in cancer patients. Response to the vaccine is characterized by specific antibody titers that neutralize VEGF/VEGFR2 binding and a cytotoxic tumor-specific response. To expand our present anti-VEGF active immunotherapy strategies, we have now studied in mice and non-human primates the effects of vaccination with a formulation of our recombinant VEGF antigen and aluminum phosphate adjuvant (hereafter denominated CIGB-247-A). Administered bi-weekly, CIGB-247-A produces high titers of anti-VEGF IgG blocking antibodies in 2 mice strains. Particularly in BALB/c, the treatment impaired subcutaneous F3II mammary tumor growth and reduced the number of spontaneous lung macro metastases, increasing animals' survival. Spleen cells from specifically immunized mice directly killed F3II tumor cells in vitro. CIGB-247-A also showed to be immunogenic in non-human primates, which developed anti-VEGF blocking antibodies and the ability for specific direct cell cytotoxic responses, all without impairing the healing of deep skin wounds or other side effect. Our results support consideration of aluminum phosphate as a suitable adjuvant for the development of new vaccine formulations using VEGF as antigen.

Preclinical development of novel Rac1-GEF signaling inhibitors using a rational design approach in highly aggressive breast cancer cell lines

Rho GTPases play a key role in the regulation of multiple essential cellular processes, including actin dynamics, gene transcription and cell cycle progression. Aberrant activation of Rac1, a member of Rho family of small GTPases, is associated with tumorigenesis, cancer progression, invasion and metastasis. Particularly, Rac1 is overexpressed and hyperactivated in highly aggressive breast cancer. Thus, Rac1 appears to be a promising and relevant target for the development of novel anticancer drugs. We identified the novel Rac1 inhibitor ZINC69391 through a docking-based virtual library screening targeting Rac1 activation by GEFs. This compound was able to block Rac1 interaction with its GEF Tiam1, prevented EGF-induced Rac1 activation and inhibited cell proliferation, cell migration and cell cycle progression in highly aggressive breast cancer cell lines. Moreover, ZINC69391 showed an in vivo antimetastatic effect in a syngeneic animal model. We further developed the novel analog 1A-116 by rational design and showed to be specific and more potent than the parental compound in vitro and interfered Rac1-P-Rex1 interaction. We also showed an enhanced in vivo potency of 1A-116 analog. These results show that we have developed novel Rac1 inhibitors that may be used as a novel anticancer therapy.

Secretory Leukocyte Protease Inhibitor (SLPI) expression downregulates E-cadherin, induces β-catenin re-localisation and triggers apoptosis-related events in breast cancer cells

BACKGROUND INFORMATION

Epithelial cadherin (E-cadherin) is involved in cell-cell adhesion through its extracellular domain, whereas the intracellular domain interacts with adaptor proteins, i.e. β-catenin, links E-cadherin to the actin cytoskeleton and participates in signal transduction events. E-cadherin protects mammary epithelial cells from apoptosis and its loss during tumour progression has been documented. Secretory Leukocyte Protease Inhibitor (SLPI) has anti- and pro-tumourigenic activities but its role in breast cancer has not been fully elucidated. Notwithstanding its relevance, how SLPI affects E-cadherin in breast cancer is still unknown. This study evaluated the effect of SLPI upon E-cadherin/β-catenin expression and apoptosis-related markers in murine (F3II) and human (MCF-7) breast tumour cells either treated with exogenous recombinant human SLPI (rhSLPI) or stably transfected with a plasmid encoding its sequence.

RESULTS

Addition of rhSLPI to F3II cells caused a decrease (P < 0.05) in E-cadherin transcript and protein levels. Similar results were observed in SLPI-stable F3II transfectants (2C1), and treatment of 2C1 cells with a siRNA toward SLPI restored E-cadherin to control levels. SLPI-expressing cells showed disruption of E-cadherin/β-catenin complex and increased (P < 0.05) percentage of cells depicting nuclear β-catenin localisation. Associated to these changes, 2C1 cells showed increased Bax/Bcl-2 ratio and p21 protein levels, decreased c-Myc protein levels and decreased Cyclin D1 and Claudin-1 transcript levels. No differences in N- and P-cadherin were observed between SLPI-transfected cells and controls. Addition of rhSLPI to MCF-7 cells or stable transfection with SLPI caused a decrease (P < 0.05) in E-cadherin expression (transcript/protein) and its redistribution to the cytoplasm, as well as β-catenin re-localisation to the cell nucleus.

CONCLUSIONS

Expression of SLPI was associated to a decrease in E-cadherin expression and re-localisation of E-cadherin to the cell cytoplasm and β-catenin to the cell cytoplasm and nucleus, and had pro-apoptotic and cell cycle-arrest effects.

Cancer vaccine characterization: from bench to clinic

BACKGROUND

The development of safe, effective, and affordable vaccines has become a global effort due to its vast impact on overall world health conditions. A brief overview of vaccine characterization techniques, especially in the area of high-resolution mass spectrometry, is presented. It is highly conceivable that the proper use of advanced technologies such as high-resolution mass spectrometry, along with the appropriate chemical and physical property evaluations, will yield tremendous in-depth scientific understanding for the characterization of vaccines in various stages of vaccine development. This work presents the physicochemical and biological characterization of cancer vaccine Racotumomab/alumina, a murine anti-idiotypic antibody that mimics N-glycolyl-GM3 gangliosides. This antibody has been tested as an anti-idiotypic cancer vaccine, adjuvated in Al(OH)3, in several clinical trials for melanoma, breast, and lung cancer.

METHODS

Racotumomab was obtained from ascites fluid, transferred to fermentation in stirred tank at 10 L and followed to a scale up to 41 L. The mass spectrometry was used for the determination of intact molecule, light and heavy chains masses; amino acids sequence analysis, N- and C-terminal, glycosylation and posttranslational modifications. Also we used the DLS for the size distribution and zeta potential analysis. The biological analyses were performed in mice and chickens.

RESULTS

We observed differences in glycosylation pattern, charge heterogeneity and structural stability between in vivo-produced and bioreactor-obtained Racotumomab products. Interestingly, these modifications had no significant impact on the immune responses elicited in two different animal models.

CONCLUSIONS

We are demonstrated that this approach could potentially be more efficient and effective for supporting vaccine research and development.

TGF-β2 dictates disseminated tumour cell fate in target organs through TGF-β-RIII and p38α/β signalling

In patients non-proliferative disseminated tumour cells (DTCs) can persist in the bone marrow (BM) while other organs (i.e. lung) present growing metastasis. This suggested that the BM might be a metastasis “restrictive soil” by encoding dormancy-inducing cues in DTCs. Here we show in a HNSCC model that strong and specific TGFβ2 signalling in the BM activates p38α/β, inducing a [ERK/p38]^low signalling ratio. This results in induction of DEC2/SHARP1 and p27, downregulation of CDK4 and dormancy of malignant DTCs. TGFβ2-induced dormancy required TGFβ-receptor-I, TGFβ-receptor-III and SMAD1/5 activation to induce p27. In lungs, a metastasis “permissive soil” with low TGFβ2 levels, DTC dormancy was short lived and followed by metastatic growth. Importantly, systemic inhibition of TGFβ-receptor-I or p38α/β activities awakened dormant DTCs fueling multi-organ metastasis. Our work reveals a “seed and soil” mechanism where TGFβ2 and TGFβRIII signalling through p38α/β regulates DTC dormancy and defines restrictive (BM) and -permissive (lung) microenvironments for HNSCC metastasis.

Anti-tumor effect of SLPI on mammary but not colon tumor growth

Secretory leukocyte protease inhibitor (SLPI) is a serine protease inhibitor that was related to cancer development and metastasis dissemination on several types of tumors. However, it is not known the effect of SLPI on mammary and colon tumors. The aim of this study was to examine the effect of SLPI on mammary and colon tumor growth. The effect of SLPI was tested on in vitro cell apoptosis and in vivo tumor growth experiments. SLPI over-expressing human and murine mammary and colon tumor cells were generated by gene transfection. The administration of murine mammary tumor cells over-expressing high levels of SLPI did not develop tumors in mice. On the contrary, the administration of murine colon tumor cells over-expressing SLPI, developed faster tumors than control cells. Intratumoral, but not intraperitoneal administration of SLPI, delayed the growth of tumors and increased the survival of mammary but not colon tumor bearing mice. In vitro culture of mammary tumor cell lines treated with SLPI, and SLPI producer clones were more prone to apoptosis than control cells, mainly under serum deprivation culture conditions. Herein we demonstrated that SLPI induces the apoptosis of mammary tumor cells in vitro and decreases the mammary but not colon tumor growth in vivo. Therefore, SLPI may be a new potential therapeutic tool for certain tumors, such as mammary tumors.

Physicochemical and biological characterization of 1E10 anti-idiotype vaccine

BACKGROUND

1E10 monoclonal antibody is a murine anti-idiotypic antibody that mimics N-glycolyl-GM3 gangliosides. This antibody has been tested as an anti-idiotypic cancer vaccine, adjuvated in Al(OH)3, in several clinical trials for melanoma, breast, and lung cancer. During early clinical development this mAb was obtained in vivo from mice ascites fluid. Currently, the production process of 1E10 is being transferred from the in vivo to a bioreactor-based method.

RESULTS

Here, we present a comprehensive molecular and immunological characterization of 1E10 produced by the two different production processes in order to determine the impact of the manufacturing process in vaccine performance. We observed differences in glycosylation pattern, charge heterogeneity and structural stability between in vivo-produced 1E10 and bioreactor-obtained 1E10. Interestingly, these modifications had no significant impact on the immune responses elicited in two different animal models.

CONCLUSIONS

Changes in 1E10 primary structure like glycosylation; asparagine deamidation and oxidation affected 1E10 structural stability but did not affect the immune response elicited in mice and chickens when compared to 1E10 produced in mice.

Immunotherapy with SLPI over-expressing mammary tumor cells decreases tumor growth

We have demonstrated previously that the inoculation of murine mammary tumor cells genetically modified to express high levels of secretory leukocyte protease inhibitor (2C1) do not develop tumors in immunocompetent mice and these cells are more prone to apoptosis than control cells. The aim of the present study was to evaluate the role of the adaptive immune response in the lack of tumor growth of 2C1 cells and the possibility of using these cells for immunotherapy. The s.c. administration of mock transfected F3II cells induces tumor in BALB/c and Nude mice. However, the inoculation of 2C1 cells develops tumor in Nude but not in BALB/c mice. The inoculation of mock transfected F3II cells to 2C1 immunized BALB/c mice by repeated administration of 2C1 cells (once a week for 3 weeks) developed significantly smaller tumors than those observed in non-immunized mice. Remarkably, survival of tumor-bearing immunized mice was higher than non-immunized animals. Herein, we demonstrate that an immunotherapy with SLPI over-expressing non-irradiated tumor cells which do not develop tumor in immunocompetent mice, partially restrain the tumor growth induced by F3II cells and increase the survival of the mice.

Combined therapeutic effect of a monoclonal anti-idiotype tumor vaccine against NeuGc-containing gangliosides with chemotherapy in a breast carcinoma model

Anti-idiotypic monoclonal antibodies (mAb) have been evaluated for actively induced immunotherapy with encouraging results. However, rational combination of cancer vaccines with chemotherapy may improve the therapeutic efficacy of these two approaches used separately. The main objective of this study was to evaluate the antitumor effect of the co-administration of 1E10 (Racotumomab), a monoclonal anti-idiotype tumor vaccine against an IgM mAb, named P3 that reacts specifically with NeuGc-containing gangliosides and low-dose Cyclophosphamide in a mammary carcinoma model. F3II tumor-bearing mice were immunized subcutaneously with 100 microg of 1E10 mAb in Alum or with 150 mg/m(2) of Cyclophosphamide intravenously 7 days after the tumor inoculation. While a limited antitumor effect was induced by a single 1E10 mAb immunization; its co-administration with low-dose Cyclophosphamide reduced significantly the F3II mammary carcinoma growth. That response was comparable with the co-administration of the standard high-dose chemotherapy for breast cancer based on 60 mg/m(2) of Doxorubicin and 600 mg/m(2) of Cyclophosphamide, without toxicity signs. Combinatorial chemo-immunotherapy promoted the CD8(+) lymphocytes tumor infiltration and enhanced tumor apoptosis. Furthermore, 1E10 mAb immunization potentiated the antiangiogenic effect of low-dose Cyclophosphamide. Additionally, splenic myeloid cells Gr1(+)/CD11b(+) associated with a suppressor phenotype were significantly reduced in F3II tumor-bearing mice immunized with 1E10 mAb alone or in combination with low-dose Cyclophosphamide. This data may provide a rational for chemo-immunotherapy combinations with potential medical implications in breast cancer.

Opposite effects of protein kinase C beta1 (PKCbeta1) and PKCepsilon in the metastatic potential of a breast cancer murine model

In this paper we investigated whether protein kinase C (PKC) beta1 and PKCepsilon, members of the classical and novel PKC family, respectively, induce phenotypic alterations that could be associated with tumor progression and metastatic dissemination in a murine model of breast cancer. Stable overexpression of PKCbeta1 in LM3 cells altered their ability to proliferate, adhere, and survive, and impaired their tumorigenicity and metastatic capacity. Moreover, PKCbeta1 induced the re-expression of fibronectin, an extracellular matrix glycoprotein which loss has been associated with the acquisition of a transformed phenotype in different cell models, and exerted an important inhibition on proteases production, effects that probably impact on LM3 invasiveness and dissemination. Conversely, PKCepsilon overexpression enhanced LM3 survival, anchorage-independent growth, and caused a significant increase in spontaneous lung metastasis. Our results suggest PKCbeta1 functions as an inhibitory protein for tumor growth and metastasis dissemination whereas PKCepsilon drives metastatic dissemination without affecting primary tumor growth.

Spindle cell carcinoma of the oral cavity and oropharynx: factors affecting outcome

BACKGROUND

Spindle cell carcinoma (SpCC) is considered to be a rare variant of squamous cell carcinoma (SCC). The behavior of such tumors is unclear. The aim of this study was to elucidate the treatment and outcome of oral and oropharyngeal SpCC.

METHODS

All the medical records of patients with the diagnosis of SpCC in the oral cavity and oropharynx in our hospital from 1994 to 2005 were reviewed. The clinical features, treatments and survival of the patients were evaluated.

RESULTS

Within the 11-year study period, 18 patients were diagnosed with oral and oropharyngeal SpCC. There were 3 cases of AJCC (American Joint Committee on Cancer) stage I, 3 of stage II, 2 of stage III, 9 of stage IV, and 1 case without definite staging. Twelve patients died of their diseases. The median overall survival time was 8.89 months. The 1-year overall survival rate was 36.7% and the 3-year overall survival rate was 27.5%. In the early stage group, the 1-year and 3-year survival rates were both 100%. In the late stage group, the 1-year survival rate was 9%, and the 3-year survival rate was 0%. The factors influencing overall survival were tumor grade, lymph nodes, metastasis, stage, vascular invasion and distant recurrence. A high local recurrence rate (73.3%) and distant metastasis rate (33.3%) were observed.

CONCLUSION

The behavior of SpCC seems to be more aggressive than that of SCC at a similar stage. Setting wider safety margins (> 2 cm) during surgical intervention is suggested. In the case of locoregional recurrence, salvage operation showed some benefit. Seeking an effective chemotherapy protocol is important for the control of distant recurrence.

Antitumor activity of some natural flavonoids and synthetic derivatives on various human and murine cancer cell lines

The effect of various natural flavonoids, cinnamic acid derivatives, and a series of synthetic flavones on cell proliferation was evaluated in vitro in a panel of established human and murine tumor cell lines. The most potent antiproliferative agents were caffeic acid n-butyl ester (12) > 2'-nitroflavone (26) > caffeic acid ethyl ester (11) approximately = 2',6-dinitroflavone (27) > apigenin (3) > 3'-bromoflavone (20) approximately = 2'-fluoro-6-bromoflavone (31). Some compounds showed a moderate effect, the order of cytotoxic activities being chrysin (2) > 2'-fluoro-6-chloroflavone (30) approximately = 2'-chlorochrysin (32) > alpha-naphthoflavone (7) > beta-naphthoflavone (8) approximately = 6-chloroflavone (14) approximately = 6-bromoflavone (15) approximately = 4'-nitroflavone (23). A structure-activity relationship analysis of each group of compounds was performed. None of the natural or synthetic compounds tested affected the proliferation of epithelial cells derived from normal mammary gland of mice or fibroblastic cells from mouse embryo, suggesting a selective action against tumor cells.

Malignant myoepithelial cells are associated with the differentiated papillary structure and metastatic ability of a syngeneic murine mammary adenocarcinoma model

BACKGROUND

The normal duct and lobular system of the mammary gland is lined with luminal and myoepithelial cell types. Although evidence suggests that myoepithelial cells might suppress tumor growth, invasion and angiogenesis, their role remains a major enigma in breast cancer biology and few models are currently available for exploring their influence. Several years ago a spontaneous transplantable mammary adenocarcinoma (M38) arose in our BALB/c colony; it contains a malignant myoepithelial cell component and is able to metastasize to draining lymph nodes and lung.

METHODS

To characterize this tumor further, primary M38 cultures were established. The low-passage LM38-LP subline contained two main cell components up to the 30th subculture, whereas the higher passage LM38-HP subline was mainly composed of small spindle-shaped cells. In addition, a large spindle cell clone (LM38-D2) was established by dilutional cloning of the low-passage MM38-LP cells. These cell lines were studied by immunocytochemistry, electron microscopy and ploidy, and syngeneic mice were inoculated subcutaneously and intravenously with the different cell lines, either singly or combined to establish their tumorigenic and metastatic capacity.

RESULTS

The two subpopulations of LM38-LP cultures were characterized as luminal and myoepithelium-like cells, whereas LM38-HP was mainly composed of small, spindle-shaped epithelial cells and LM38-D2 contained only large myoepithelial cells. All of them were tumorigenic when inoculated into syngeneic mice, but only LM38-LP cultures containing both conserved luminal and myoepithelial malignant cells developed aggressive papillary adenocarcinomas that spread to lung and regional lymph nodes.

CONCLUSION

The differentiated histopathology and metastatic ability of the spontaneous transplantable M38 murine mammary tumor is associated with the presence and/or interaction of both luminal and myoepithelial tumor cell types.

Karyotypic evolution of four novel mouse mammary carcinoma cell lines. Identification of marker chromosomes by fluorescence in situ hybridization

We studied the karyotypes of four different mammary carcinoma cell lines derived from a medroxy-progesterone acetate (MPA)-induced mouse mammary carcinoma using G-banding and fluorescence in situ hybridization. All the cell lines showed the same four marker chromosomes (M1-M4) as the parental tumor and also acquired new markers. M1 and M2 are Robertsonian translocations between chromosomes 1 and 10 and 2 and 17. M3 is an acrocentric marker derived from chromosomes 4, 5, and 12; M4 is derived from chromosomes 6 and 8. The parental tumor disclosed a modal number of 39, with a trisomy of chromosomes 3, 4, 10, and 11 and monosomies of 9, 13, and 16. MC4-L1 and MC4-L3 lines had a chromosome number similar to that of the parental tumor in early passages, which increased to the triploid range in late passages. MC4-L5 showed a near-diploid modal number in both early and late passages. MC4-L2 cells had a high chromosome number even in early passages. To our knowledge, this is the first study in which a complete characterization of the cytogenetics of murine mammary carcinoma cell lines and of their parental tumor is described. No associations between changes in ploidy, invasiveness, or hormone dependence were found. Conversely, the presence of one exclusive marker chromosome, a translocation between chromosomes 1 and 18 (M5), in the most aggressive and in vivo hormone-independent line suggests that this rearrangement may be associated with these biologic features. The constant presence of common marker chromosomes in both the parental tumor and the derived cell lines suggests that they are involved in the maintenance of this tumor phenotype.

Lovastatin alters cytoskeleton organization and inhibits experimental metastasis of mammary carcinoma cells

Lovastatin is a competitive inhibitor of 3-hydroxy 3-methylglutaryl coenzyme A reductase, the key regulatory enzyme of cholesterol biosynthesis. This enzyme catalyzes the formation of mevalonate, which is also the precursor of isoprenoid moieties, such as farnesol and geraniol, that are incorporated into several molecules essential for tumor cell signaling. Here, we describe that pretreatment with a non-cytotoxic concentration of lovastatin (10 microM) dramatically inhibited the metastatic ability of F311 mammary carcinoma cells in syngeneic BALB/c mice. Similarly, daily i.p. treatment of animals with a well-tolerated dose of lovastatin (10 mg/kg/day) significantly reduced the number of experimental lung metastases. In vitro, incubation of F3II monolayers in the presence of lovastatin caused a rounded-cell morphology. Immunofluorescence analysis revealed a lack of cortical actin organization, micrutubule disruption and inhibition of integrin-mediated focal contacts in lovastatin-treated cells. Exposure of F3II cells to lovastatin significantly inhibited tumor cell adhesion and migration, and coincubation with the cholesterol precursor mevalonate prevented these effects. Lovastatin reduced membrane localization of Rho protein, a signaling molecule involved in the regulation of actin-based cell motility that needs geranylation for membrane association and activation. In addition, lovastatin induced a dose-dependent inhibition in the secretion of urokinase, a key proteolytic enzyme during tumor invasion and metastasis, and a significant increase of tissue-type plasminogen activator, a marker of good prognosis in mammary cancer. These data suggest that antimetastatic properties of lovastatin are strongly associated with alterations in cytoskeleton organization and the consequent modulation of adhesion, motility and proteolysis.

Desmopressin inhibits lung and lymph node metastasis in a mouse mammary carcinoma model of surgical manipulation

BACKGROUND AND OBJECTIVES

Desmopressin (DDAVP) is a synthetic derivative of vasopressin with hemostatic and fibrinolytic properties that has been used during surgery in patients with bleeding disorders. Our aim was to investigate the effect of DDAVP on lung and lymph node metastatic cell colonization using a preclinical mouse mammary carcinoma model of subcutaneous tumor manipulation and surgical excision.

METHODS

Female BALB/c mice bearing the highly aggressive F3II mammary carcinoma were subjected to repeated manipulations of primary tumors (0.5 kg/cm(2) during 2 min), followed (or not) by surgical excision. DDAVP was administered intravenously 30 min before and 24 h after each manipulation or surgery, at a dose of 2 microg/kg. At the end of the experiment, mice were sacrificed and necropsied.

RESULTS

Tumor manipulation induced dissemination to the axillary nodes and increased up to 6-fold the number of metastatic lung nodules. Perioperative treatment with DDAVP dramatically reduced regional metastasis. The incidence of lymph node involvement in manipulated animals was 12% with DDAVP and 87% without treatment (P < 0.02). Histopathological analysis of axillary nodes from DDAVP-treated animals showed sinusal histiocytosis and no evidence of cancer cells. Metastatic lung nodules were also reduced about 65% in animals treated with DDAVP (P = 0.026).

CONCLUSIONS

Our results suggest a potential clinical application of DDAVP in the management of breast cancer, as well as other aggressive solid tumors. DDAVP may be useful to reduce the risk of metastatic cell colonization both during and after surgical manipulation.

Apoptotic cell death in mammary adenocarcinoma cells is prevented by soluble factors present in the target organ of metastasis

Target organ of metastasis determines the fate of metastasis. The soluble factors released from one or more cell types in the new stroma may influence growth and survival of metastatic cells. In the present study, we used conditioned media from the kidney, liver and lung, the latter being the target organ of metastasis of murine mammary adenocarcinoma cell lines LM3, LMM3 and F3II, to assess whether the soluble factors released from these organs could modulate in vitro survival of these cell lines after apoptosis-inducing treatments and to investigate the mechanisms involved in this effect. We demonstrate that conditioned medium from lung, but not from liver or kidney, promotes survival of these cells after doxorubicin, cisplatin, agonistic anti-Fas antibody and serum withdrawal treatments. Furthermore, LMM3 cells treated with lung conditioned medium after doxorubicin exposure maintained their tumorigenic capacity and metastatic potential. Neither IGF nor EGF could promote survival but, surprisingly, TGF-beta could reduce sensitivity of LMM3 cells to doxorubicin in vitro. Doxorubicin treatment induced Bax expression and down-regulated Bcl-2 expression. In contrast, lung conditioned medium increased Bcl-2 expression and inhibited doxorubicin-mediated Bcl-2 down-regulation. Neither of those treatments alone modified Bcl-X(L) expression, although co-treatment induced a 3- to 5-fold increase of its expression. These results suggest that the lung microenvironment could promote metastasis of these adenocarcinoma cell lines by increasing survival of metastatic cells, possibly by modulation of Bcl-2 protein family expression.

Chronic in vitro exposure to 3'-azido-2', 3'-dideoxythymidine induces senescence and apoptosis and reduces tumorigenicity of metastatic mouse mammary tumor cells

Normal cells in culture divide a certain amount of times and undergo a process termed replicative senescence. Telomere loss is thought to control entry into senescence. Activation of telomerase in tumors bypasses cellular senescence and is thus a requirement for tumor progression. We reported previously the preferential incorporation of 3'-azido-2', 3'-dideoxythymidine (AZT) in telomeric sequences of immortalized cells in culture. In this work, we have investigated the effects of chronic in vitro AZT exposure on F3II mouse mammary carcinoma cells. We demonstrate, for the first time, that AZT-treated tumor cells have a reduced tumorigenicity in syngeneic BALB/c mice. Tumor incidence was reduced and survival was prolonged in animals inoculated with AZT-treated cells when comparing with control counterparts. The number and size of spontaneous metastases were also decreased in animals inoculated with AZT-treated cells. In addition, we present evidence of morphological and biochemical signs of senescence, as shown by the staining for senescence associated beta-galactosidase activity, and induction of programmed cell death, as demonstrated by an increase of caspase-3 activity, in tumor cells exposed to AZT. These data indicate that chronic exposure of mammary carcinoma cells to AZT may be sufficient to induce a senescent phenotype and to reduce tumorigenicity.

Modulation of urokinase-type plasminogen activator and metalloproteinase activities in cultured mouse mammary-carcinoma cells: enhancement by paclitaxel and inhibition by nocodazole

Paclitaxel is a potent anti-tumor drug used in the treatment of breast cancer. It induces de-centralization of the microtubular system in tumor cells, blocking cell division. In the search for dissemination to a secondary site, cancer cells are capable of degrading most components of the extracellular matrix via an extracellular proteolytic cascade, including urokinase-type plasminogen activator (uPA) and the matrix metalloproteinases (MMPs). In the present study, the effects of paclitaxel and nocodazole, 2 drugs known to affect microtubules with opposite mechanisms of action, have been tested for their effect on the secretion of uPA and MMPs in cultures of F3II mouse mammary-tumor cells. Tumor-derived uPA activity significantly increased after pre-treatment of tumor cells for 24 hr with micromolar concentrations of paclitaxel (4 microM), while decreasing after pre-treatment with nocodazole (1 microM). A similar modulation was found for MMP-9 by zymographic analysis. Immunofluorescence and Western-blot analysis confirmed the formation of parallel microtubule fragments in paclitaxel-treated cells and almost complete de-polymerization of microtubules in nocodazole-treated ones. Our data suggest that, through opposite actions on microtubule organization and dynamics, paclitaxel and nocodazole exert inverse modulation of tumor-derived proteolytic activity in mammary tumor cells.

Antimetastatic effect of desmopressin in a mouse mammary tumor model

We have investigated the effects of desmopressin (DDAVP), a synthetic analog of the natural hormone vasopressin, on experimental lung colonization of mammary tumor cells using a syngeneic BALB/c mouse model. Coinjection of DDAVP (1-2 microg/kg body weight) at the time of i.v. inoculation of F3II carcinoma cells or LM3 adenocarcinoma cells significantly inhibited the formation of experimental lung metastases. In both cases, the number of pulmonary nodules was reduced about 70%. Inhibition of metastasis was also obtained with i.v. administration of DDAVP 24 h after tumor cell inoculation. Interestingly, the inhibition of lung metastasis was not due to direct cytotoxic effects of DDAVP on mammary tumor cells. The in vitro formation of multicellular aggregates in the presence of citrated plasma from control and DDAVP-treated mice was also examined. Control plasma rapidly induced a significant tumor cell aggregation. In contrast, in the presence of plasma from DDAVP-treated mice, tumor cells remained as a single cell suspension. DDAVP may help to dissolve the protective fibrin shield of circulating tumor cells. Our data suggest, for the first time, that adjuvant DDAVP therapy may impair successful implantation of circulating mammary tumor cells.

Role of tumor-derived granulocyte-macrophage colony-stimulating factor in mice bearing a highly invasive and metastatic mammary carcinoma

We have examined the role of granulocyte-macrophage colony-stimulating factor (GM-CSF) in tumor-bearing BALB/c mice using the syngeneic F3II mammary carcinoma. In the present model, progression of subcutaneous tumors induced massive myelopoiesis in bone marrow and spleen due to GM-CSF secretion by tumor cells. In vitro, the addition of recombinant mouse GM-CSF (5- 25 ng/ml) caused a significant increase in F3II cell growth, either in the presence or absence of serum. Zymographic analysis of conditioned media from F3II monolayers showed that GM-CSF exerted a dose-dependent enhancement in the metalloproteinases MMP-9 (105 kD) and MMP-2 (70 kD), key enzymes in mammary tumor cell invasion. Our data suggest that ectopic GM-CSF production stimulates myelopoiesis and may also play an important role in tumor progression and metastasis formation.

Verapamil inhibits tumor protease production, local invasion and metastasis development in murine carcinoma cells

The invasion and metastasis process involves degradation of the extracellular matrix mediated by tumor- and host-produced proteolytic enzymes. The main enzymes involved in this process are urokinase-type plasminogen activator (uPA) and the matrix metalloproteinases (MMPs). Calcium is a main co-factor in the signaling pathways that regulate cell proliferation and protease production. We have studied here the effect of verapamil, a calcium channel blocker widely used to treat hypertensive diseases, on local tumor growth, spontaneous and experimental metastasis development, tumor-associated protease production and circulating MMP activity in tumor-bearing mice. BALB/c mice treated for 45 days with verapamil showed no toxic effects. Oral administration of verapamil to mice injected with F311 tumor cells, either pre-treated or not with verapamil, showed a significant decrease of local tumor invasion and both spontaneous and experimental metastasis development (51.3% inhibition of metastasis in both cases, p < 0.01). uPA and MMP-9 production by tumor cells in vitro was significantly inhibited by verapamil in a dose-dependent manner, showing a long-term inhibition after removal of the drug. Verapamil also exhibited a marked cytostatic effect on F311 cell proliferation in vitro. In addition, circulating MMP activity, usually enhanced in tumor-bearing mice, diminished significantly with all verapamil treatments. Our results suggest that modulation of the calcium-dependent signaling pathways that regulate tumor- or host-dependent production of proteases and tumor cell proliferation could contribute to the inhibition of metastasis development. Finally, we describe the inhibitory effects of a commonly used hypotensor in humans, verapamil, on the invasive and metastatic capacity of mammary tumor cells.

Function and expression of CD44 during spreading, migration, and invasion of murine carcinoma cells

The cell surface glycoprotein CD44 is proposed as a main participant in cell adhesion and migration. We studied the function, expression, and distribution of CD44 in the invasive and metastatic F3II murine carcinoma cell line during adhesion, spreading, migration, and invasion. A mAb anti-CD44 (KM 201) dramatically blocked F3II cell adhesion on both plastic and hyaluronic acid coatings, as well as spreading on uncoated plastic surfaces (P < 0.01). KM201 mAb significantly inhibited F3II cell migration and invasion in Transwell chambers. Immunocytochemistry of spreading cells revealed that CD44 distributed in bands on the cell surface, particularly in the tip of leading edges and in the perinuclear zones of the cell membrane. CD44 antigen was never detected in filopodia or lamellipodia nor in focal adhesion-like structures, but was also detectable as strong interlamellar bands. Fully spread cells showed a decreased CD44 signal compared to cells in early stages of spreading. This decrease correlated with a reduced expression of CD44 as detected by Western blot. We also investigated the signals that may regulate CD44 expression in F3II cells. Treatment of F3II cells, with phorbol myristate acetate (PMA) or phosphatidic acid (PA, the product of PLD-dependent hydrolysis of phosphatidylcholine), significantly enhanced CD44 expression. Conversely, the treatment of F3II cells with H7, a specific PKC inhibitor, or propranolol, which blocks PA conversion to DAG, significantly decreased CD44 expression levels. These results suggest the involvement of PKC and PLD pathways in CD44 expression. These results demonstrate that CD44 plays an important role during F3II cells adhesion, spreading, migration, and invasion. In addition we provide information linking the PLD- and PKC-dependent pathways with the regulation of CD44 expression.

Reduction of mouse mammary tumor formation and metastasis by lovastatin, an inhibitor of the mevalonate pathway of cholesterol synthesis

Lovastatin, a fungal antibiotic used in the treatment of hypercholesterolemia, is an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the key regulatory enzyme in the mevalonate pathway of cholesterol synthesis. We examined the antitumor properties of lovastatin on the F3II sarcomatoid mammary carcinoma, a highly invasive and metastatic murine tumor model. Female BALB/c inbred mice were inoculated subcutaneously with F3II tumor cells and injected i.p. daily with 10 mg/kg body weight of lovastatin or administered p.o. at a level corresponding to the human dosage of 1-2 mg/kg/day. Treatment significantly prolonged tumor latency and reduced tumor formation and metastatic dissemination to the lungs from established mammary tumors. In vitro, antitumor properties of lovastatin were strongly associated with inhibition of tumor cell attachment and migration. These actions were prevented by addition of mevalonate but not by equivalent concentrations of farnesyl pyrophosphate. In accordance, Western blot assays showed that lovastatin effects did not appear to be related to modifications in Ras oncoproteins in our model. The present data indicate that lovastatin could be an antitumor agent with potentially useful clinical applications in breast cancer.