Outgrowth of BT-474 human breast cancer cells in immune-deficient mice: a new in vivo model for hormone-dependent breast cancer

Dissecting phospho-motif-dependent Shc1 interactome using long synthetic protein fragments

Activated receptor tyrosine kinases (RTKs) rely on the assembly of signaling proteins into high-dimensional protein complexes for signal transduction. Shc1, a prototypical scaffold protein, plays a pivotal role in directing phosphotyrosine (pY)-dependent protein complex formation for numerous RTKs typically through its two pY-binding domains. The three conserved pY sites within its CH1 region (Shc1CH1) hold particular significance due to their substantial contribution to its functions. However, how Shc1 differentially utilizes these sites to precisely coordinate protein complex assembly remains unclear. Here, we employed multiple peptide ligation techniques to synthesize an array of long protein fragments (107 amino acids) covering a significant portion of the Shc1CH1 region with varying phosphorylation states at residues Y239, 240, 313, and S335. By combining these phospho-Shc1CH1 fragments with integrated proteomics sample preparation and quantitative proteomic analysis, we were able to comprehensively resolve the site-specific interactomes of Shc1 with single amino acid resolution. By applying this approach to different cancer cell lines, we demonstrated that these phospho-Shc1CH1 fragments can be effectively used as a diagnostic tool to assess cell type-specific RTK signaling networks. Collectively, these biochemical conclusions help to better understand the sophisticated organization of pY-dependent Shc1 adaptor protein complexes and their functional roles in cancer.

Recent advances in breast cancer cell line research

Breast cancer, a formidable global health challenge, needs continuous translational research to understand the complexity of mechanisms and improve therapeutic and diagnostic strategies. Breast cancer cell lines are of paramount importance as they significantly contribute to the initial stage of research to understand cancer biology. This review provides insights into targeted therapies and immunotherapies that have emerged using in vitro models and microbiome analysis. It focuses on therapeutic development using cell lines and the limitations of tumor heterogeneity and microenvironment. We explore the evolving landscape of breast cancer cell lines from two-dimensional (2-D) cultures to patient-derived xenograft (PDX) models advancing both fundamental and translational research. Patient-derived xenografts, cell line-derived xenografts (CDX), three-dimensional (3-D) cultures, organoids, and circulating tumor cells (CTC) models provide promising alternatives that capture the intricacies of the tumor microenvironment. This review bridges the gap between traditional cell lines and newer developments exploring the therapeutic and diagnostic advancements and needs for cell lines to expedite the progress in breast cancer research and treatment.

The Interaction of the Endocannabinoid Anandamide and Paracannabinoid Lysophosphatidylinositol during Cell Death Induction in Human Breast Cancer Cells

Endocannabinoid anandamide (AEA) and paracannabinoid lysophosphatidylinositol (LPI) play a significant role in cancer cell proliferation regulation. While anandamide inhibits the proliferation of cancer cells, LPI is known as a cancer stimulant. Despite the known endocannabinoid receptor crosstalk and simultaneous presence in the cancer microenvironment of both molecules, their combined activity has never been studied. We evaluated the effect of LPI on the AEA activity in six human breast cancer cell lines of different carcinogenicity (MCF-10A, MCF-7, BT-474, BT-20, SK-BR-3, MDA-MB-231) using resazurin and LDH tests after a 72 h incubation. AEA exerted both anti-proliferative and cytotoxic activity with EC50 in the range from 31 to 80 µM. LPI did not significantly affect the cell viability. Depending on the cell line, the response to the LPI-AEA combination varied from a decrease in AEA cytotoxicity to an increase in it. Based on the inhibitor analysis of the endocannabinoid receptor panel, we showed that for the former effect, an active GPR18 receptor was required and for the latter, an active CB2 receptor. The data obtained for the first time are important for the understanding the manner by which endocannabinoid receptor ligands acting simultaneously can modulate cancer growth at different stages.

Bridging Scales: a Hybrid Model to Simulate Vascular Tumor Growth and Treatment Response

Cancer is a disease driven by random DNA mutations and the interaction of many complex phenomena. To improve the understanding and ultimately find more effective treatments, researchers leverage computer simulations mimicking the tumor growth in silico. The challenge here is to account for the many phenomena influencing the disease progression and treatment protocols. This work introduces a computational model to simulate vascular tumor growth and the response to drug treatments in 3D. It consists of two agent-based models for the tumor cells and the vasculature. Moreover, partial differential equations govern the diffusive dynamics of the nutrients, the vascular endothelial growth factor, and two cancer drugs. The model focuses explicitly on breast cancer cells over-expressing HER2 receptors and a treatment combining standard chemotherapy (Doxorubicin) and monoclonal antibodies with anti-angiogenic properties (Trastuzumab). However, large parts of the model generalize to other scenarios. We show that the model qualitatively captures the effects of the combination therapy by comparing our simulation results with previously published pre-clinical data. Furthermore, we demonstrate the scalability of the model and the associated C++ code by simulating a vascular tumor occupying a volume of 400mm3 using a total of 92.5 million agents.

[89Zr]-Pertuzumab PET Imaging Reveals Paclitaxel Treatment Efficacy Is Positively Correlated with HER2 Expression in Human Breast Cancer Xenograft Mouse Models

Paclitaxel (PTX) treatment efficacy varies in breast cancer, yet the underlying mechanism for variable response remains unclear. This study evaluates whether human epidermal growth factor receptor 2 (HER2) expression level utilizing advanced molecular positron emission tomography (PET) imaging is correlated with PTX treatment efficacy in preclinical mouse models of HER2+ breast cancer. HER2 positive (BT474, MDA-MB-361), or HER2 negative (MDA-MB-231) breast cancer cells were subcutaneously injected into athymic nude mice and PTX (15 mg/kg) was administrated. In vivo HER2 expression was quantified through [89Zr]-pertuzumab PET/CT imaging. PTX treatment response was quantified by [18F]-fluorodeoxyglucose ([18F]-FDG) PET/CT imaging. Spearman's correlation, Kendall's tau, Kolmogorov-Smirnov test, and ANOVA were used for statistical analysis. [89Zr]-pertuzumab mean standard uptake values (SUVmean) of BT474 tumors were 4.9 ± 1.5, MDA-MB-361 tumors were 1.4 ± 0.2, and MDA-MB-231 (HER2-) tumors were 1.1 ± 0.4. [18F]-FDG SUVmean changes were negatively correlated with [89Zr]-pertuzumab SUVmean (r = -0.5887, p = 0.0030). The baseline [18F]-FDG SUVmean was negatively correlated with initial [89Zr]-pertuzumab SUVmean (r = -0.6852, p = 0.0002). This study shows PTX treatment efficacy is positively correlated with HER2 expression level in human breast cancer mouse models. Molecular imaging provides a non-invasive approach to quantify biological interactions, which will help in identifying chemotherapy responders and potentially enhance clinical decision-making.

18F-labeled ethisterone derivative for progesterone receptor targeted PET imaging of breast cancer

PURPOSE

A novel radiolabeled probe 1‑(17‑[¹⁸F]fluoro‑3,6,9,12,15‑pentaoxaheptadecyl‑1H‑1,2,3‑triazole testosterone ([¹⁸F]FPTT) was synthesized and evaluated for PET imaging of progesterone receptor (PR)-positive breast cancer.

METHODS

The ethinyl group of ethisterone, a PR targeting pharmacophore, was coupled with azide modified PEG-OTs by click chemistry to obtain the labeling precursor. The final [¹⁸F]FPTT was synthesized by a one-step nucleophilic substitution reaction with ¹⁸F. The in vitro stabilities of [¹⁸F]FPTT in saline or rat serum were determined after 2 h incubation. Then the in vitro cell binding, ex vivo biodistribution and in vivo imaging of [¹⁸F]FPTT were further investigated to evaluate the PR targeting ability and feasibility for the diagnosis of PR-positive breast cancer with PET imaging.

RESULTS

[¹⁸F]FPTT was obtained in high decay-corrected radiochemical yield (78 ± 9%) at the end of synthesis. It had high radiochemical purity (>98%) after HPLC purification and good in vitro stability. The molar activity of [¹⁸F]FPTT was calculated as 17 GBq/μmol. The microPET imaging of [¹⁸F]FPTT in tumor-bearing mice showed much higher tumor uptake in PR-positive MCF-7 tumor (3.9 ± 0.20%ID/g) than that of PR-negative MDA-MB-231 tumor (1.3 ± 0.08%ID/g). The high MCF-7 tumor uptake could be specifically inhibited by blocking with ethisterone (1.3 ± 0.11%ID/g) or [¹⁹F]FPTT (2.20 ± 0.17%ID/g), respectively. The biodistribution in estrogen-primed female SD rats of [¹⁸F]FPTT showed high uterus and ovary uptakes (8.31 ± 1.74%ID/g and 3.79 ± 0.82%ID/g at 1 h post-injection). The specific uptakes of uterus and ovary in normal rats were 3.52 ± 0.29%ID/g and 3.22 ± 0.50%ID/g respectively and could be inhibited by co-injecting of ethisterone.

CONCLUSION

A novel [¹⁸F]FPTT probe based on ethisterone modification could be a potential diagnostic agent for PR-positive breast cancer.

Hydrogels bearing bioengineered mimetic embryonic microenvironments for tumor reversion

Embryonic microenvironments can reverse the metastatic phenotype of aggressive tumors by inhibiting the Nodal signaling pathway. Here, we hypothesize that embryonic microenvironments can be transplanted for the purpose of oncotherapy. We report the development of an injectable bioactive hydrogel system containing the key antagonists of Nodal signaling-Cripto-1 receptor antibodies (2B11)-for the creation of embryonic microenvironments and the examination of their effect on tumor reversion treatment using a mouse model. Our in vitro results show that the hydrogel system can reduce the mitochondrial membrane potential of MDA-MB-231 and MCF-7, promote cell apoptosis, and reduce the invasive ability of cells. Our in vivo results illustrate that the hydrogel system can significantly inhibit tumor growth in both breast cancer and melanoma tumor-bearing mouse models, as well as transform the cell morphology of melanoma B16 cells to melanin-like cells. Furthermore, the results of the up-regulation of tumor suppressor genes and the down-regulation of oncogenes by high-throughput sequencing confirm that the developed system can also selectively turn on some tumor suppressor genes and turn off certain oncogenes so as to prompt the benign reversion of the tumor phenotype. Taken together, our results demonstrate the injectable biomaterial system is able to create an effective microenvironment for melanoma and breast tumor therapy.

Development and characterization of two human triple-negative breast cancer cell lines with highly tumorigenic and metastatic capabilities

Triple-negative breast cancer (TNBC) is a group of cancer with high diversity, limited therapies, and poor prognosis. TNBC cell lines and animal models provide effective tools for studies and drug discovery. Here, we report the development of two TNBC cell lines (XtMCF and LmMCF) based on our existing cell model that consists of normal breast epithelial cell line MCF10F, estradiol-transformed cells trMCF, and Boyden chamber-selected tumorigenic cells bsMCF. The XtMCF and LmMCF cell line were derived from xenograft and lung metastasis of bsMCF cells, respectively. The bsMCF, XtMCF, and LmMCF cells have undergone epithelial-mesenchymal transition (EMT), exhibiting a mesenchymal-like feature. In vivo studies showed XtMCF and LmMCF cells were highly tumorigenic and metastatic. The injection of 5 × 10(4) cells to CB17/SCID mice mammary fat pad produced xenografts in 9/9 mice and tumors reached 10 millimeters in diameter in 5 weeks. The injection of 1 × 10(6) XtMCF or 8 × 10(4) LmMCF cells into the mice tail vein was sufficient to form extensive lung metastases in 4 weeks. The two new cell lines exhibited CD44(+) /CD49f(+) and CD44(+) /EpCAM(+) cancer stem cell (CSC) characteristics, and the EGF-like domain of EpCAM was cleaved off. Together with the normal and early transformed counterparts, herein we provide a complete cancer model for the study of initiation, evolution, and identification of new therapeutics for TNBC. The finding that EGF-like domain of EpCAM was cleaved off in cells which have undergone EMT suggests this cleavage may be involved in the EMT process and the cancer stem cell properties of these cells.

Development of a peptide by phage display for SPECT imaging of resistance-susceptible breast cancer

Personalized medicine is at the forefront of cancer diagnosis and therapy. Molecularly targeted therapies such as trastuzumab and tamoxifen have enhanced prognosis of patients with cancers expressing ERBB2 and the estrogen receptor, respectively. One obstacle to targeted therapy is the development of resistance. A targeted peptide that could distinguish resistance-susceptible cancer would aid in treatment. BT-474 human breast cancer cells can be resistant to both tamoxifen and trastuzumab, and may serve as a model for malignancies in which targeted therapy may not work. Bacteriophage (phage) display is a combinatorial technology that has been used to isolate peptides that target a specific cancer subtype. It was hypothesized that in vivo phage display could be used to select a peptide for SPECT imaging of BT-474 human breast cancer xenografts. A phage library displaying random 15 amino acid peptides was subjected to four rounds of selection, after which 14 clones were analyzed for BT-474 binding and specificity. One phage clone, 51, demonstrated superior binding and specificity, and the displayed peptide was synthesized for in vitro characterization. Peptide 51 bound specifically to BT-474 cells with an EC50 = 2.33 µM and was synthesized as a DOTA-conjugated peptide and radiolabeled with (111)In for in vitro and in vivo analysis. The radiolabeled peptide exhibited an IC50 = 16.1 nM to BT-474 cells and its biodistribution and SPECT imaging in BT-474 xenografted mice was analyzed. Although tumor uptake was moderate at 0.11% ID/g, SPECT imaging revealed a distinct tumor vasculature binding pattern. It was discovered that peptide 51 had an identical 5 amino acid N-terminal sequence to a peptide, V1, which bound to Nrp1, a tumor vasculature protein. Peptide 51 and V1 were examined for binding to target cells, and 51 bound both target and endothelial cells, while V1 only bound endothelial cells. Truncated versions of 51 did not bind BT-474 cells, demonstrating that the targeting ability of 51 was independent of the homologous V1 sequence. These results demonstrate that in vivo phage display can effectively identify a peptide that specifically targets a breast cancer cell line that is susceptible to targeted therapy resistance.

Automated whole animal bio-imaging assay for human cancer dissemination

A quantitative bio-imaging platform is developed for analysis of human cancer dissemination in a short-term vertebrate xenotransplantation assay. Six days after implantation of cancer cells in zebrafish embryos, automated imaging in 96 well plates coupled to image analysis algorithms quantifies spreading throughout the host. Findings in this model correlate with behavior in long-term rodent xenograft models for panels of poorly- versus highly malignant cell lines derived from breast, colorectal, and prostate cancer. In addition, cancer cells with scattered mesenchymal characteristics show higher dissemination capacity than cell types with epithelial appearance. Moreover, RNA interference establishes the metastasis-suppressor role for E-cadherin in this model. This automated quantitative whole animal bio-imaging assay can serve as a first-line in vivo screening step in the anti-cancer drug target discovery pipeline.

An integrated bioinformatics approach identifies elevated cyclin E2 expression and E2F activity as distinct features of tamoxifen resistant breast tumors

Approximately half of estrogen receptor (ER) positive breast tumors will fail to respond to endocrine therapy. Here we used an integrative bioinformatics approach to analyze three gene expression profiling data sets from breast tumors in an attempt to uncover underlying mechanisms contributing to the development of resistance and potential therapeutic strategies to counteract these mechanisms. Genes that are differentially expressed in tamoxifen resistant vs. sensitive breast tumors were identified from three different publically available microarray datasets. These differentially expressed (DE) genes were analyzed using gene function and gene set enrichment and examined in intrinsic subtypes of breast tumors. The Connectivity Map analysis was utilized to link gene expression profiles of tamoxifen resistant tumors to small molecules and validation studies were carried out in a tamoxifen resistant cell line. Despite little overlap in genes that are differentially expressed in tamoxifen resistant vs. sensitive tumors, a high degree of functional similarity was observed among the three datasets. Tamoxifen resistant tumors displayed enriched expression of genes related to cell cycle and proliferation, as well as elevated activity of E2F transcription factors, and were highly correlated with a Luminal intrinsic subtype. A number of small molecules, including phenothiazines, were found that induced a gene signature in breast cancer cell lines opposite to that found in tamoxifen resistant vs. sensitive tumors and the ability of phenothiazines to down-regulate cyclin E2 and inhibit proliferation of tamoxifen resistant breast cancer cells was validated. Our findings demonstrate that an integrated bioinformatics approach to analyze gene expression profiles from multiple breast tumor datasets can identify important biological pathways and potentially novel therapeutic options for tamoxifen-resistant breast cancers.

HER2/ErbB2-induced breast cancer cell migration and invasion require p120 catenin activation of Rac1 and Cdc42

Breast cancers that overexpress the receptor tyrosine kinase ErbB2/HER2/Neu result in poor patient outcome because of extensive metastatic progression. Herein, we delineate a molecular mechanism that may govern this malignant phenotype. ErbB2 induction of migration requires activation of the small GTPases Rac1 and Cdc42. The ability of ErbB2 to activate these small GTPases necessitated expression of p120 catenin, which is itself up-regulated by signaling through ErbB2 and the tyrosine kinase Src. Silencing p120 in ErbB2-dependent breast cancer cell lines dramatically inhibited migration and invasion as well as activation of Rac1 and Cdc42. In contrast, overexpression of constitutively active mutants of these GTPases reversed the effects of p120 silencing. Lastly, ectopic expression of p120 promoted migration and invasion and potentiated metastatic progression of a weakly metastatic, ErbB2-dependent breast cancer cell line. These results suggest that p120 acts as an obligate intermediate between ErbB2 and Rac1/Cdc42 to modulate the metastatic potential of breast cancer cells.

Effect of testosterone on E1S-sulfatase activity in non-malignant and cancerous breast cells in vitro

INTRODUCTION

Testosterone (T) is a therapeutic option for women with hypoactive sexual desire disorder. T may have an impact on the mammary gland by altering local estrogen synthesis. The aim of the present study was to measure the effect of T on estrone-sulfate (E1S)-sulfatase (STS) expression, and activity using hormone-dependent BC cells with high and low aggressive potential (BT-474, MCF-7), and HBL-100 as a breast cell line of non-malignant origin.

METHODS

Cells were incubated in RPMI 1640 medium containing 5% steroid-depleted fetal calf serum for 3d, and subsequently incubated in absence or presence of T alone, and combined with anastrozole (A) at 10(-8)M, and 10(-6)M at 37 degrees C for either 24h or directly in cell extracts ("direct"). STS protein expression was measured by dot-blot (immunoblotting), and STS, HSD17B1 and HSD17B2 mRNA levels by quantitative RT-PCR. STS activity was evaluated by incubating homogenized breast cells with [(3)H]-E1S and separating the products E1, and E2 by thin layer chromatography.

RESULTS

Basal STS mRNA expression did not reveal group differences. However, STS mRNA was decreased by T+A in MCF-7 cells. 17HSDB1 expression was decreased by T+A in BT-474 cells, and 17HSDB2 expression was decreased by A and T+A treatment in MCF-7 cells. Basal and T treated STS protein expression was significantly higher in malignant compared to non-malignant breast cells. However, T did not induce significant intra-cell line differences. Similarly, basal and T treated STS activity was significantly higher in highly malignant compared to non-malignant breast cells. Regardless of cell lines, T slightly decreased STS activity after "direct" incubation, but led to an increase of local estrogen formation after 24h which was attenuated, and partly reversed by A, respectively.

CONCLUSIONS

The more aggressive the breast cell line, the higher the local estrogen formation. The transition from normal to malignant seems to be accompanied by an altered autoregulation. The given local endocrine milieu seems to be essential for response to T.

Anchorage-independent cell growth signature identifies tumors with metastatic potential

The oncogenic phenotype is complex, resulting from the accumulation of multiple somatic mutations that lead to the deregulation of growth regulatory and cell fate controlling activities and pathways. The ability to dissect this complexity, so as to reveal discrete aspects of the biology underlying the oncogenic phenotype, is critical to understanding the various mechanisms of disease as well as to reveal opportunities for novel therapeutic strategies. Previous work has characterized the process of anchorage-independent growth of cancer cells in vitro as a key aspect of the tumor phenotype, particularly with respect to metastatic potential. Nevertheless, it remains a major challenge to translate these cell biology findings into the context of human tumors. We previously used DNA microarray assays to develop expression signatures, which have the capacity to identify subtle distinctions in biological states and can be used to connect in vitro and in vivo states. Here we describe the development of a signature of anchorage-independent growth, show that the signature exhibits characteristics of deregulated mitochondrial function and then demonstrate that the signature identifies human tumors with the potential for metastasis.

Human breast cancer tumor models: molecular imaging of drug susceptibility and dosing during HER2/neu-targeted therapy

PURPOSE

To use near-infrared (NIR) optical imaging to assess the therapeutic susceptibility and drug dosing of orthotopic human breast cancers implanted in mice treated with molecularly targeted therapy.

MATERIALS AND METHODS

This study was approved by the institutional animal care and use committee. Imaging probes were synthesized by conjugating the human epidermal growth factor receptor type 2 (HER2)-specific antibody trastuzumab with fluorescent dyes. In vitro probe binding was assessed with flow cytometry. HER2-normal and HER2-overexpressing human breast cancer cells were orthotopically implanted in nude mice. Intravital laser scanning fluorescence microscopy was used to evaluate the in vivo association of the probe with the tumor cells. Mice bearing 3-5-mm-diameter tumors were intravenously injected with 0.4 nmol of HER2 probe before or after treatment. A total of 123 mice were used for all in vivo tumor growth and imaging experiments. Tumor fluorescence intensity was assessed, and standard fluorescence values were determined. Statistical significance was determined by performing standard analysis of variance across the imaging cohorts.

RESULTS

HER2 probe enabled differentiation between HER2-normal and HER2-overexpressing human breast cancer cells in vitro and in vivo, with binding levels correlating with tumor trastuzumab susceptibility. Serial imaging before and during trastuzumab therapy revealed a significant reduction (P < .05) in probe binding with treatment and thus provided early evidence of successful HER2 inhibition days before the overall reduction in tumor growth was apparent.

CONCLUSION

NIR imaging with HER2-specific imaging probes enables evaluation of the therapeutic susceptibility of human mammary tumors and of drug dosing during HER2-targeted therapy with trastuzumab. This approach, combined with tomographic imaging techniques, has potential in the clinical setting for determining patient eligibility for and adequate drug dosing in molecularly targeted cancer therapies.

Pegylated liposomal doxorubicin: Proof of principle using preclinical animal models and pharmacokinetic studies

Encapsulation of doxorubicin in polyethylene glycol-coated liposomes (Doxil/Caelyx [PLD]), was developed to enhance the safety and efficacy of conventional doxorubicin. The liposomes alter pharmacologic and pharmacokinetic parameters of conventional doxorubicin so that drug delivery to the tumor is enhanced while toxicity normally associated with conventional doxorubicin is decreased. In animals and humans, pharmacokinetic advantages of PLD include an increased area under the plasma concentration-time curve, longer distribution half-life, smaller volume of distribution, and reduced clearance. In preclinical models, PLD produced remission and cure against many cancers including tumors of the breast, lung, ovaries, prostate, colon, bladder, and pancreas, as well as lymphoma, sarcoma, and myeloma. It was also found to be effective as adjuvant therapy. In addition, it was found to cross the blood-brain barrier and induce remission in tumors of the central nervous system. Increased potency over conventional doxorubicin was observed and, in contrast to conventional doxorubicin, PLD was equally effective against low- and high-growth fraction tumors. The combination of PLD with vincristine or trastuzumab resulted in additive effects and possible synergy. PLD appeared to overcome multidrug resistance, possibly as the result of increased intracellular concentrations and an interaction between the liposome and P-glycoprotein function. On the basis of pharmacokinetic and preclinical studies, PLD, either alone or as part of combination therapy, has potential applications to treat a variety of cancers.

Relevance of breast cancer cell lines as models for breast tumours: an update

The number of available breast cancer cell (BCC) lines is small, and only a very few of them have been extensively studied. Whether they are representative of the tumours from which they originated remains a matter of debate. Whether their diversity mirrors the well-known inter-tumoural heterogeneity is another essential question. While numerous similarities have long been found between cell lines and tumours, recent technical advances, including the use of micro-arrays and comparative genetic analysis, have brought new data to the discussion. This paper presents most of the BCC lines that have been described in some detail to date. It evaluates the accuracy of the few of them widely used (MCF-7, T-47D, BT-474, SK-BR-3, MDA-MB-231, Hs578T) as tumour models. It is concluded that BCC lines are likely to reflect, to a large extent, the features of cancer cells in vivo. The importance of oestrogen receptor-alpha (gene ESR1 ) and Her-2/ neu ( ERBB2 ) as classifiers for cell lines and tumours is underlined. The recourse to a larger set of cell lines is suggested since the exact origin of some of the widely used lines remains ambiguous. Investigations on additional specific lines are expected to improve our knowledge of BCC and of the dialogue that these maintain with their surrounding normal cells in vivo.

Therapeutic efficacy of anti-ErbB2 immunoliposomes targeted by a phage antibody selected for cellular endocytosis

Many targeted cancer therapies require endocytosis of the targeting molecule and delivery of the therapeutic agent to the interior of the tumor cell. To generate single chain Fv (scFv) antibodies capable of triggering receptor-mediated endocytosis, we previously developed a method to directly select phage antibodies for internalization by recovering infectious phage from the cytoplasm of the target cell. Using this methodology, we reported the selection of a panel of scFv that were internalized into breast cancer cells from a nonimmune phage library. For this work, an immunotherapeutic was generated from one of these scFv (F5), which bound to ErbB2 (HER2/neu). The F5 scFv was reengineered with a C-terminal cysteine, expressed at high levels in Escherichia coli, and coupled to sterically stabilized liposomes. F5 anti-ErbB2 immunoliposomes were immunoreactive as determined by surface plasmon resonance (SPR) and were avidly internalized by ErbB2-expressing tumor cell lines in proportion to the levels of ErbB2 expression. F5-scFv targeted liposomes containing doxorubicin had antitumor activity and produced significant reduction in tumor size in xenografted mice compared to nontargeted liposomes containing doxorubicin. This strategy should be applicable to generate immunotherapeutics for other malignancies by selecting phage antibodies for internalization into other tumor types and using the scFv to target liposomes or other nanoparticles.

Consequences of altered TGF-beta expression and responsiveness in breast cancer: evidence for autocrine and paracrine effects

To characterize the impact of increased production of TGF-beta in a xenograft model of human breast cancer, TGF-beta-responsive MDA-231 cells were genetically modified by stable transfection so as to increase their production of active TGF-beta1. Compared with control cells, cells that produced increased amounts of TGF-beta proliferated in vitro more slowly. In vivo, however, tumors derived from these cells exhibited increased proliferation and grew at an accelerated pace. To evaluate the role of autocrine TGF-beta signaling, cells were also transfected with a dominant-negative truncated type II TGF-beta receptor (TbetaRII). Disruption of autocrine TGF-beta signaling in the TGF-beta-overexpressing cells reduced their in vivo growth rate. Co-inoculation of Matrigel with the TGF-beta-overexpressing cells expressing the truncated TbetaRII compensated for their diminished in vivo growth capacity, compared with the TGF-beta-overexpressing cells with an intact autocrine loop. Tissue invasion by the tumor was a distinctive feature of the TGF-beta-overexpressing cells, whether or not the autocrine loop was intact. Furthermore, tumors derived from TGF-beta-overexpressing cells, irrespective of the status of the autocrine TGF-beta-signaling pathway, had a higher incidence of lung metastasis. Consistent with the suggestion that TGF-beta's enhancement of invasion and metastasis is paracrine-based, we observed no significant differences among the cell clones in an in vitro invasion assay. Thus, in this experimental model system in vitro assays of cell proliferation and invasion do not accurately reflect in vivo observations, perhaps due to autocrine and paracrine effects of TGF-beta that influence the important in vivo-based phenomena of tumor growth, invasion, and metastasis.

A heterologous 3-D coculture model of breast tumor cells and fibroblasts to study tumor-associated fibroblast differentiation

The objective of our study was to establish spheroid cocultures as a valid 3-D in vitro model mimicking tumor-fibroblast interactions in scirrhous breast tumors. The experimental setup was designed to verify if in cocultures (a) adherence and migration reflect the invasive potential of breast tumor cells, (b) breast tumor cells induce tumor-associated fibroblast differentiation, and (c) tumor-derived fibroblasts better reflect the in vivo situation than normal skin fibroblasts. Only one (SK-BR-3) out of five tumor cell types showed extensive fibroblast infiltration, MCF-7 cells frequently invaded fibroblast spheroids; BT474, T47D, and ZR-75-1 were noninvasive. While tumor cell invasion was independent of fibroblast origin, tumor-associated myofibroblast differentiation defined by alpha-SMA expression was demonstrated for tumor-derived but not normal skin fibroblasts in coculture indicating that (a) tumor cell invasion and myofibroblast differentiation are autonomous processes and (b) cocultures with tumor-derived fibroblasts resemble advanced stages of desmoplastic carcinomas while cocultures with normal skin fibroblasts rather reflect the early tumor development. The latter is also implied by fibroblast-associated alterations in tumor cell morphology and ECM distribution in the system. By using RNA arbitrarily primed PCR and cells isolated from cocultures by fluorescence-activated and magnetic cell separation, peripheral myelin protein PMP22/SR13 has been identified as a novel candidate with potential relevance in the interaction between tumor cell and normal fibroblast since PMP22 mRNA was significantly reduced in normal skin fibroblasts in coculture with BT474 cells.

The growth and metastasis of human, HER-2/neu-overexpressing tumor cell lines in male SCID mice

HER-2/neu is overexpressed on a variety of human adenocarcinomas and overexpression has been associated with a poor prognosis. For this reason, HER-2 has become an attractive target for immunotherapy. To facilitate testing of anti-HER-2-monoclonal antibodies (MAbs) and immunotoxins (ITs), we have evaluated the in vivo growth and metastatic spread of three HER-2-overexpressing human breast cancer cell lines (BT474, MDA-MB-453 and HCC1954) and one ovarian cancer cell line (SKOV3.ip1) in pre-irradiated male SCID mice using subcutaneous (s.c.), intravenous (i.v.) and intraperitoneal (i.p.) routes of injection. All the cell lines tested grew as s.c. tumors and the growth of BT474 and MDA-MB-453 cells after s.c. injection was improved by co-inoculation with Matrigel. Metastases to the lungs were detectable by PCR or histopathology after s.c. injection of BT474 and to a much lesser extent after s.c. injection of HCC1954, MD-MB-453 and SKOV3.ip1 cells. I.p. injection of HCC1954 and SKOV3.ip1 cells produced fatal ascites while i.v. injection of SKOV3.ip1, but not BT474 or MDA-MB-453 cells, resulted in infiltration of lungs and death within 9-11 weeks.

Establishment and characterization of three new breast-cancer cell lines

We have established and characterized 3 new breast-cancer cell lines from pleural effusions of patients with advanced breast cancer. All 3 cell lines, designated IBEP-1, IBEP-2 and IBEP-3, showed typical ultrastructural characteristics of epithelial mammary tumor cells. Electron microscopy showed, among other characteristics, the presence of numerous microvilli, desmosomal junctions, intracytoplasmic duct-like vacuoles, well-developed endoplasmic reticulum and large nuclei. Immunohistochemical and biochemical studies revealed that the 3 cell lines expressed cytokeratin, epithelial membrane antigen, CEA and CA 15-3, but all showed negative immunoreaction for vimentin. On the other hand, other antigens (LEU-M1, GCDFP 15, c-erbB-2) were expressed by some of the cell lines, but in a variable manner. Ploidy studies confirmed the neoplastic origin of the cell lines. The doubling times were 68 hr for IBEP-1, 29 hr for IBEP-2 and 39 hr for IBEP-3. Only IBEP-2 cells expressed estrogen receptors (ER+), which were down-regulated after preincubation with E2, but they did not express progesterone receptors (PgR-). IBEP-1 and IBEP-3 cells were ER- but expressed PgR (PgR+). In these 2 cell lines, PgR were down-regulated after pre-incubation of the cells with progesterone (10(-8) M) for 24 hr. Estradiol (E2) increased the proliferation rate of IBEP-2 cells and progesterone increased the proliferation of IBEP-I and -3 cell lines. S.C. injection of the 3 IBEP cell lines into nude mice resulted in the growth of solid tumors between 11 and 16 weeks after inoculation. These cell lines could thus be new models for studying various aspects of the biology and the tumorigenicity of breast-cancer cells. A major interest of these new cell lines is that 2 of them were ER- and PgR+, which is an exceptional phenotypic feature. These 2 cell lines could be interesting models for studying the regulation of PgR and the effects of progestins and antiprogestins independently of the presence of ER.

Development of a new metastatic human breast carcinoma xenograft line

Xenografts originated from human tumours offer the most appropriate research material for in vivo experimental research. However, primary human breast carcinomas are difficult to grow when transplanted in athymic mice: tumour take is less than 15%. Recently, we have achieved 60% tumour take by injecting tumour cell suspensions mixed with Matrigel. Human breast xenografts originated from primary breast carcinoma also frequently show the potential to metastasize spontaneously. In the present study, we generated a human breast carcinoma xenograft line (UISO-BCA-NMT-18) that shows 100% tumorigenicity and 80-100% lung metastasis when transplanted s.c. in athymic mice. We have studied in detail the characteristics of the xenograft and the patient's tumour from which the xenograft line originated. Both the xenograft and the patient's tumour showed intense staining for mutant p53 nuclear protein, and high expression of U-PA, PAI and u-PAR. In vivo growth of the xenograft is stimulated by exogenous supplementation of oestrogen. This xenograft is continuously growing in mice and has shown 80-100% metastasis for the last three successive in vivo passages. This well-characterized, oestrogen-responsive, metastatic breast carcinoma xenograft line will provide excellent research material for metastasis-related research.

Migration and gap junctional intercellular communication determine the metastatic phenotype of human tumor cell lines

Gap junctional intercellular communication (GJIC) as well as cell migration play an essential role in the metastatic cascade of human tumors. We show a dependence of metastatogenic phenotypes of human tumor cells (cell lines T 24, SCC-25, MDA-MB-361 and SK-BR-3) from the GJIC and the migration activity. The GJIC was studied by microinjection of the fluorescent dye Lucifer Yellow (LY) and cell migration was studied by investigating the locomotion of the tumor cells in 3-dimensional collagen matrices. Diminished GJIC seems to be more influential for the metastatic phenotype than modulation of the locomotory behavior of the tumor cells.

Locomotory phenotypes of human tumor cell lines and T lymphocytes in a three-dimensional collagen lattice

Active cellular locomotion is a feature of such diverse cell types as lymphocytes and cancer cells. The locomotory phenotype of a cell should ultimately reflect the biochemical basis of different migratory strategies. We investigated the locomotory behavior of five epithelial cell lines and one non-epithelial human cell-line as well as human CD4+ T lymphocytes in a three-dimensional collagen type I matrix using time-lapse video microscopy and computer assisted cell-tracking. Migration velocity was up to 70 times lower in tumor cells (0.1-0.3 microm/min) as compared to T lymphocytes (7-7.5 microm/min), whereas the percentage of spontaneously active cells was up to twice as high in tumor cells (80-90%) in comparison to T lymphocytes (54%). Persistence, i.e. the degree of roaming, varied appreciably between the different cell types. In conclusion, velocity and persistence may describe distinct migration strategies in different cell types, i.e. discerning T cell migration from tumor cell invasion.