Control Of Cancer Growth Research Articles

New Strategies for Expression and Purification of Recombinant Human RNASET2 Protein in Pichia pastoris.

Ribonucleases form a large family of enzymes involved in RNA metabolism and are endowed with a broad range of biological functions. Among the different RNase proteins described in the last decades, those belonging to the Rh/T2/S subfamily show the highest degree of evolutionary conservation, suggesting the occurrence of a key critical ancestral role for this protein family. We have recently defined the human RNASET2 gene as a novel member of a group of oncosuppressors called "tumor antagonizing genes," whose activity in the control of cancer growth is carried out mainly in vivo. However, to better define the molecular pathways underlying the oncosuppressive properties of this protein, further structural and functional investigations are necessary, and availability of high-quality recombinant RNASET2 is of paramount importance. Here, we describe a multi-step strategy that allows production of highly pure, catalytically competent recombinant RNASET2 in both wild-type and mutant forms. The recombinant proteins that were produced with our purification strategy will be instrumental to perform a wide range of functional assays aimed at dissecting the molecular mechanisms of RNASET2-mediated tumor suppression.

MDM2 and CDK4 expression in periosteal osteosarcoma.

Periosteal osteosarcoma is defined by the World Health Organization as an intermediate-grade, malignant, cartilaginous, and bone-forming neoplasm arising on the surface of bone. Unlike other subtypes of osteosarcoma, no data have been published about mouse double minute 2 (MDM2) and cyclin-dependent kinase 4 (CDK4) expression. For this reason, we evaluated the molecular and immunohistochemical features of MDM2 and CDK4 in 27 cases relative to 20 patients with a diagnosis of periosteal osteosarcoma, surgically treated at the Rizzoli Institute between 1981 and 2014. When possible, these results were compared with the MDM2 amplification status as determined by fluorescence in situ hybridization (FISH). All but 1 case (26/27, 96.3%) were negative for MDM2 protein using immunohistochemistry both in primary and in recurrent periosteal osteosarcoma, whereas gene amplification of MDM2 was not detected in any tumor analyzed (10 cases). The positive immunohistochemical case shows a weak/moderate focal nuclear expression of MDM2 antibody in the prevalent cartilaginous component and in the spindle cells of peripheral fibroblastic areas associated with osteoid production in a primary periosteal osteosarcoma. CDK4 immunohistochemical expression was negative in all 27 cases. This retrospective analysis has demonstrated that MDM2 and CDK4 are very rarely expressed in primary and recurrent periosteal osteosarcomas and therefore do not appear to be molecules central to the control of cancer development, growth, and progression in periosteal osteosarcoma. Therefore, when compared with low-grade central and parosteal osteosarcomas, MDM2 and CDK4 markers cannot be used diagnostically to differentiate this subtype of osteosarcoma.

Comparison of immunity in mice cured of primary/metastatic growth of EMT6 or 4THM breast cancer by chemotherapy or immunotherapy.

PurposeWe have compared cure from local/metastatic tumor growth in BALB/c mice receiving EMT6 or the poorly immunogenic, highly metastatic 4THM, breast cancer cells following manipulation of immunosuppressive CD200:CD200R interactions or conventional chemotherapy.MethodsWe reported previously that EMT6 tumors are cured in CD200R1KO mice following surgical resection and immunization with irradiated EMT6 cells and CpG oligodeoxynucleotide (CpG), while wild-type (WT) animals developed pulmonary and liver metastases within 30 days of surgery. We report growth and metastasis of both EMT6 and a highly metastatic 4THM tumor in WT mice receiving iv infusions of Fab anti-CD200R1 along with CpG/tumor cell immunization. Metastasis was followed both macroscopically (lung/liver nodules) and microscopically by cloning tumor cells at limiting dilution in vitro from draining lymph nodes (DLN) harvested at surgery. We compared these results with local/metastatic tumor growth in mice receiving 4 courses of combination treatment with anti-VEGF and paclitaxel.ResultsIn WT mice receiving Fab anti-CD200R, no tumor cells are detectable following immunotherapy, and CD4+ cells produced increased TNFα/IL-2/IFNγ on stimulation with EMT6 in vitro. No long-term cure was seen following surgery/immunotherapy of 4THM, with both microscopic (tumors in DLN at limiting dilution) and macroscopic metastases present within 14 d of surgery. Chemotherapy attenuated growth/metastases in 4THM tumor-bearers and produced a decline in lung/liver metastases, with no detectable DLN metastases in EMT6 tumor-bearing mice-these latter mice nevertheless showed no significantly increased cytokine production after restimulation with EMT6 in vitro. EMT6 mice receiving immunotherapy were resistant to subsequent re-challenge with EMT6 tumor cells, but not those receiving curative chemotherapy. Anti-CD4 treatment caused tumor recurrence after immunotherapy, but produced no apparent effect in either EMT6 or 4THM tumor bearers after chemotherapy treatment.ConclusionImmunotherapy, but not chemotherapy, enhances CD4+ immunity and affords long-term control of breast cancer growth and resistance to new tumor foci.

Science and mechanism of action of targeted therapies in cancer treatment.

To identify common signaling pathways that control cancer growth and discuss the mechanism of action of cancer targeted therapies. Medical and nursing literature, research articles, published clinical guidelines. Understanding the signaling pathways and genetic mutations that control cancer cell growth elucidates an understanding of the mechanism of targeted therapies. To understand the mechanism of action of targeted therapies, oncology nurses must first be familiar with the most common signaling pathways. Adding to this foundation, the nurse can easily learn about the classes of targeted therapies and the strategies to minimize and manage common side effects.

Immunomodulation in cancer.

We have to strengthen our 'chess-playing skills' when using immunotherapeutic approaches in cancer treatment: know the cancerous opponent, study its evolution and have an eye for its weaknesses. Besides tumor cells, other pieces on the board are stromal cells, endothelial cells and different immune cells. Some of these immune cells, like helper and cytotoxic T cells, natural killer (T) cells and mature dendritic cells are of help, others like regulatory T cells and myeloid-derived suppressor cells belong to the opponent, while macrophages and neutrophils can belong to both. A personalized approach, by selecting the optimal treatment from the myriad of possibilities based on biomarker findings, is essential to attack that particular cancer at that moment. We have to adapt the strategy to the changing positions created by the opponent. Using all these skills, we might control cancer growth in the future.

Overexpression of Ephrin A2 receptors in cancer stromal cells is a prognostic factor for the relapse of gastric cancer.

Microenvironments control cancer growth and progression. We explored the prognostic impact of stromal reaction and cancer stromal cells on relapse risk and survival after curative gastrectomy in gastric cancer patients. Tissue samples were obtained from 107 patients with gastric adenocarcinoma who underwent curative (R0) gastrectomy. Primary stromal cells isolated from gastric cancer tissue (GCSC) and normal gastric tissue (Gastric stromal cell: GSC) in each patient were cultured and subjected to comprehensive proteome (LC-MS/MS) and real-time RT-PCR analysis. Expression of Ephrin A2 receptors (EphA2) in cancers and GCSC was evaluated immunohistochemically. Intermingling of EphA2-positive cancer cells and GCSC (IC/A2+) and overexpression of EphA2 in cancer cells (Ca/A2+) in invasive parts of tumors were assessed, as were relationships of IC/A2+, Ca/A2+, and clinicopathological factors with relapse-free survival and overall survival. Proteome analysis showed that EphA2 expression was significantly higher in GCSC than GSC. Real-time RT-PCR analysis showed that levels of EphA1/A2/A3/A5 and EphB2/B4 were ≥2.0-fold higher in GCSC than GSC. Ca/A2 and IC/A2 were positive in 65 (60.7%) and 26 (24.3%) patients, respectively. Relapse was significantly more frequent in IC/A2-positive than in IC/A2-negative (HR, 2.12; 95% CI, 1.16-5.41; p=0.0207) patients. Among the 54 patients who received S-1 adjuvant chemotherapy, relapse-free survival (RFS) was significantly shorter in those who were IC/A2-positive than in those who were IC/A2-negative and Ca/A2-negative (HR, 2.83; 95% CI, 1.12-12.12; p=0.0339). Multivariable analysis indicated that pathological stage (p=0.010) and IC/A2+ (p=0.008) were independent risk factors for recurrence. IC/A2+ was predictive of relapse after curative (R0) gastrectomy.

Test Article

β2-microglobulin (β2-m) has become the focus of intense scrutiny since the discovery of its undesirable roles promoting osteomimicry and cancer progression. β2-m is a well-known housekeeping protein that forms complexes with the heavy chain of major histocompatibility complex class I molecules, which are heterodimeric cell surface proteins that present antigenic peptides to cytotoxic T cells. On recognition of foreign peptide antigens on cell surfaces, T cells actively bind and lyse antigen-presenting cancer cells. In addition to its roles in tumor immunity, β2-m has two different functions in cancer cells, either tumor promoting or tumor suppressing, in cancer cell context-dependent manner. Our studies have demonstrated that β2-m is involved extensively in the functional regulation of growth, survival, apoptosis, and even metastasis of cancer cells. We found that β2-m is a soluble growth factor and a pleiotropic signaling molecule which interacts with its receptor, hemochromatosis protein, to modulate epithelial-to-mesenchymal transition (EMT) through iron-responsive pathways. Specific antibodies against β2-m have remarkable tumoricidal activity in cancer, through β2-m action on iron flux, alterations of intracellular reactive oxygen species, DNA damage and repair enzyme activities, β-catenin activation and cadherin switching, and tumor responsiveness to hypoxia. These novel functions of β2-m and β2-m signaling may be common to several solid tumors including human lung, breast, renal, and prostate cancers. Our experimental results could lead to the development of a novel class of antibody-based pharmaceutical agents for cancer growth control. In this review, we briefly summarize the recent data regarding β2-m as a promising new cancer therapeutic target and discuss antagonizing this therapeutic target with antibody therapy for the treatment of localized and disseminated cancers.

Tumor Heterogeneity and Personalized Cancer Medicine: Are we Being Outnumbered?

Tumor heterogeneity is regarded as a major obstacle to successful personalized cancer medicine. The lack of reliable response assays reflective of in vivo tumor heterogeneity and associated resistance mechanisms hampers identification of reliable biomarkers. By contrast, oncogene addiction and paracrine signaling enable systemic responses despite tumor heterogeneity. This strengthens researchers in their efforts towards personalized cancer medicine. Given the fact that tumor heterogeneity is an integral part of cancer evolution, diagnostic tools need to be developed in order to better understand the dynamics within a tumor. Ultra-deep sequencing may reveal future resistant clones within a (liquid) tumor biopsy. On-treatment biopsies may provide insight into intrinsic or acquired drug resistance. Subsequently, upfront combinatorial treatment or sequential therapy strategies may forestall drug resistance and improve patient outcome. Finally, innovative response assays, such as organoid cultures or patient-derived tumor xenografts, provide an extra dimension to correlate molecular profiles with drug efficacy and control cancer growth.

β2-Microglobulin-mediated Signaling as a Target for Cancer Therapy

β2-microglobulin (β2-m) has become the focus of intense scrutiny since the discovery of its undesirable roles promoting osteomimicry and cancer progression. β2-m is a well-known housekeeping protein that forms complexes with the heavy chain of major histocompatibility complex class I molecules, which are heterodimeric cell surface proteins that present antigenic peptides to cytotoxic T cells. On recognition of foreign peptide antigens on cell surfaces, T cells actively bind and lyse antigen-presenting cancer cells. In addition to its roles in tumor immunity, β2-m has two different functions in cancer cells, either tumor promoting or tumor suppressing, in cancer cell context-dependent manner. Our studies have demonstrated that β2-m is involved extensively in the functional regulation of growth, survival, apoptosis, and even metastasis of cancer cells. We found that β2-m is a soluble growth factor and a pleiotropic signaling molecule which interacts with its receptor, hemochromatosis protein, to modulate epithelial-to-mesenchymal transition (EMT) through iron-responsive pathways. Specific antibodies against β2-m have remarkable tumoricidal activity in cancer, through β2-m action on iron flux, alterations of intracellular reactive oxygen species, DNA damage and repair enzyme activities, β-catenin activation and cadherin switching, and tumor responsiveness to hypoxia. These novel functions of β2-m and β2-m signaling may be common to several solid tumors including human lung, breast, renal, and prostate cancers. Our experimental results could lead to the development of a novel class of antibody-based pharmaceutical agents for cancer growth control. In this review, we briefly summarize the recent data regarding β2-m as a promising new cancer therapeutic target and discuss antagonizing this therapeutic target with antibody therapy for the treatment of localized and disseminated cancers.

MDM2 and CDK4 expression in periosteal osteosarcoma

Periosteal osteosarcoma is defined by World Health Organization as an intermediate-grade, malignant cartilage and bone forming neoplasm arising on the surface of bone. At difference to the other subtypes of osteosarcoma, in literature no data has been published about MDM2 and CDK4 expression. For this, we evaluate the immunohistochemistry expression of MDM2 and CDK4 to detect overexpression caused by gene amplification in 18 cases of periosteal osteosarcoma, surgically treated in Rizzoli Institute between 1981 and 2013. All but one case (17/18, 94.4%) were negative for MDM2 and CDK4 using immunohistochemistry. The positive case shows a strong nuclear expression of both antibodies in the prevalent cartilaginous component and in the spindle cells of peripheral fibroblastic areas associated with osteoid-producing. In conclusion, at difference to low grade central osteosarcoma and parosteal osteosarcomas, MDM2 and CDK4 are very rarely expressed in periosteal osteosarcoma and therefore do not appear to be a molecule central to the control of cancer development, growth and progression in periosteal osteosarcoma. These two markers can be used diagnostically to differentiate these subtypes of osteosarcoma and underline a different genetic pathway for the pathogenesis of this rare subtype of osteosarcoma. Periosteal osteosarcoma is defined by World Health Organization as an intermediate-grade, malignant cartilage and bone forming neoplasm arising on the surface of bone. At difference to the other subtypes of osteosarcoma, in literature no data has been published about MDM2 and CDK4 expression. For this, we evaluate the immunohistochemistry expression of MDM2 and CDK4 to detect overexpression caused by gene amplification in 18 cases of periosteal osteosarcoma, surgically treated in Rizzoli Institute between 1981 and 2013. All but one case (17/18, 94.4%) were negative for MDM2 and CDK4 using immunohistochemistry. The positive case shows a strong nuclear expression of both antibodies in the prevalent cartilaginous component and in the spindle cells of peripheral fibroblastic areas associated with osteoid-producing. In conclusion, at difference to low grade central osteosarcoma and parosteal osteosarcomas, MDM2 and CDK4 are very rarely expressed in periosteal osteosarcoma and therefore do not appear to be a molecule central to the control of cancer development, growth and progression in periosteal osteosarcoma. These two markers can be used diagnostically to differentiate these subtypes of osteosarcoma and underline a different genetic pathway for the pathogenesis of this rare subtype of osteosarcoma.

Immunogenicity and therapeutic efficacy of a dual-component genetic cancer vaccine cotargeting carcinoembryonic antigen and HER2/neu in preclinical models.

Several cancer vaccine efforts have been directed to simultaneously cotarget multiple tumor antigens, with the intent to achieve broader immune responses and more effective control of cancer growth. Genetic cancer vaccines based on in vivo muscle electro-gene-transfer of plasmid DNA (DNA-EGT) and adenoviral vectors represent promising modalities to elicit powerful immune responses against tumor-associated antigens (TAAs) such as carcinoembryonic antigen (CEA) and human epidermal growth factor receptor-2 (HER2)/neu. Combinations of these modalities of immunization (heterologous prime-boost) can induce superior immune reactions as compared with single-modality vaccines. We have generated a dual component-dual target genetic cancer vaccine consisting of a DNA moiety containing equal amounts of two plasmids, one encoding the extracellular and transmembrane domains of HER2 (ECD.TM) and the other encoding CEA fused to the B subunit of Escherichia coli heat-labile toxin (LTB), and of an adenoviral subtype 6 dicistronic vector carrying the same two tumor antigens gene constructs. The CEA/HER2 vaccine was tested in two different CEA/HER2 double-transgenic mouse models and in NOD/scid-DR1 mice engrafted with the human immune system. The immune response was measured by enzyme-linked immunospot assay, flow cytometry, and ELISA. The CEA/HER2 vaccine was able to break immune tolerance against both antigens. Induction of a T cell and antibody immune response was detected in immune-tolerant mice. Most importantly, the vaccine was able to slow the growth of HER2/neu⁺ and CEA⁺ tumors. A significant T cell response was measured in NOD/scid-DR1 mice engrafted with human cord blood cells. In conclusion, the CEA/HER2 genetic vaccine was immunogenic and able to confer significant therapeutic effects. These data warrant the evaluation of this vaccination strategy in human clinical trials.

The Dual Role of Smad7 in the Control of Cancer Growth and Metastasis

Smad7 was initially identified as an inhibitor of Transforming growth factor (TGF)-β due mainly to its ability to bind TGF-β receptor type I and prevent TGF-β-associated Smad signaling. More recently, it has been demonstrated that Smad7 can interact with other intracellular proteins and regulate also TGF-β-independent signaling pathways thus making a valid contribution to the neoplastic processes in various organs. In particular, data emerging from experimental studies indicate that Smad7 may differently modulate the course of various tumors depending on the context analyzed. These observations, together with the demonstration that Smad7 expression is deregulated in many cancers, suggest that therapeutic interventions around Smad7 can help interfere with the development/progression of human cancers. In this article we review and discuss the available data supporting the role of Smad7 in the modulation of cancer growth and progression.

Immunotherapy of melanoma with the immune costimulatory monoclonal antibodies targeting CD137

Knowledge of how the immune system recognizes and attempts to control cancer growth and development has improved dramatically. The advent of immunotherapies for cancer has resulted in robust clinical responses and confirmed that the immune system can significantly inhibit tumor progression. Until recently, metastatic melanoma was a disease with limited treatment options and a poor prognosis. CD137 (also known as 4-1BB) a member of the tumor necrosis factor (TNF) receptor superfamily, is an activation-induced T cell costimulator molecule. Growing evidence indicates that anti-CD137 monoclonal antibodies possess strong antitumor properties, the result of their powerful capability to activate CD8+ T cells, to produce interferon (IFN)-γ, and to induce cytolytic markers. Combination therapy of anti-CD137 with other anticancer agents, such as radiation, has robust tumor-regressing abilities against nonimmunogenic or poorly immunogenic tumors. Of importance, targeting CD137 eliminates established tumors, and the fact that anti-CD137 therapy acts in concert with other anticancer agents and/or radiation therapy to eradicate nonimmunogenic and weakly immunogenic tumors is an additional benefit. Currently, BMS-663513, a humanized anti-CD137 antibody, is in clinical trials in patients with solid tumors, including melanoma, renal carcinoma, ovarian cancer, and B-cell malignancies. In this review, we discuss the basis of the therapeutic potential of targeting CD137 in cancer treatment, focusing in particular, on BMS-663513 as an immune costimulatory monoclonal antibody for melanoma immunotherapy.

Tumor-Targeting Multifunctional Micelles for Imaging and Chemotherapy of Advanced Bladder Cancer

This work aimed to determine if the treatment outcomes of bladder cancer could be improved by targeting micelles that are decorated with bladder cancer-specific ligands on the surface and loaded with the chemotherapeutic drug paclitaxel. Targeting efficacy and specificity was determined with cell lines. An in vivo targeting and anti-tumor efficacy study was conducted in mice carrying patient-derived xenografts. Targeting micelles were more efficient than nontargeting micelles in delivering the drug load into bladder cancer cells both in vitro and in vivo (p < 0.05). The micelle formulation of paclitaxel was less toxic than free paclitaxel in Cremophor(®) (Sigma, MO, USA) and allowed administration of three-times the maximum tolerated dose without increasing the toxicity. Targeting micelles were more effective than the nontargeting micelles in controlling cancer growth (p = 0.0002) and prolonging overall survival (p = 0.002). Targeting micelles loaded with paclitaxel offer strong potential for clinical applications in treating bladder cancer.

Abstract IA2: Microenvironmental control of bone metastasis

Abstract Breast cancer is often associated with a poor prognosis largely due to its tendency to metastasize. Breast cancer preferentially metastasizes to the skeleton. Since Paget's seed and soil hypothesis from more than a century ago, it is known that bones constitute a very hospitable soil that attracts and allows breast cancer cells to thrive. Surprisingly, however, only a few studies have addressed the role of the bone microenvironment in bone metastasis, and most of them emphasized the role of osteoclasts (bone-destructing cells). Osteoclasts are known to stimulate bone metastasis because of their bone resorbing activity, which releases into the bone marrow space growth factors normally embedded in the bone matrix. On the other hand, the role of osteoblasts (bone-making cells) in this process has not been addressed directly. There is growing evidence that osteoblasts' function is not limited to making bone. In particular, these cells regulate various aspects of hematopoiesis, insulin secretion in the pancreas, or even male fertility in mice. We hypothesized that osteoblasts play an important role in breast cancer metastasis to bone. We tested this possibility by inoculating a breast cancer cell line (PyMT-FVB-Luc+ cells) into either the mammary fat pad, or directly into the blood stream of syngeneic recipient mice, which presented either an increased or a decreased osteoblast number. Hypoxia and the hypoxia inducible factor 1alpha (Hif-1alpha) play a fundamental role in bone by stimulating the differentiation of the osteoblasts in hypoxic niches where metastatic cells coming from distant tumors are often found. However, the role of the hypoxic microenvironment in bone metastasis is unknown. We used a conditional knockout approach to suppress either Hif-1alpha or von Hippel Lindau (VHL, an E3 ubiquitin-ligase that targets Hif-1alpha for degradation) specifically in osteoblasts (ΔHif-1alphaOB and ΔVHLOB mice). VHL suppression leads to ectopic expression of Hif-1alpha, and thus functions as a gain-of-function model for Hif-1alpha. Tissue specific ablation of Hif-1alpha and VHL in osteoblasts was performed by mating floxed Hif-1alpha or VHL mice, with mice expressing the Cre recombinase under the control of the osterix promoter, which is solely activated in immature osteoblasts. ΔHif-1alphaOB mice presented a decreased number of osteoblasts and reduced bone mass. Conversely, ΔVHLOB mice exhibited a dramatic increase in osteoblast number and bone mass. Intracardiac injection of PyMT-FVB-Luc+ cells into these loss- or gain-of-function models revealed that osteoblasts directly or indirectly stimulate breast cancer metastasis to bone. Strikingly, our results also show that osteoblasts produce systemic changes, controlling breast cancer metastasis to the lungs, as well as the growth of primary mammary tumors. These results were obtained by either transplanting PyMT-FVB-Luc+ cells into the mammary gland, or by tail vein (intravenous) injections. Thus, osteoblasts can affect distant tissues, well beyond the bone microenvironment. By providing the first evidence that the skeleton exerts a systemic control of breast cancer growth and dissemination, our study expands the biological importance of this organ. Citation Format: Sylvain Provot, Audrey Brenot, Amy-Jo Casbon, Ying Yu, Zena Werb. Microenvironmental control of bone metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr IA2.

Control of AMP-activated protein kinase, Akt, and mTOR in EGCG-treated HT-29 colon cancer cells

Suppressing the mammalian target of rapamycin (mTOR) pathway has emerged as an attractive method for controlling cancer growth and preventing cancers. Epigallocatechin-3-gallate (EGCG) is a well-known chemopreventive polyphenol, and its effects on AMP-activated protein kinase (AMPK) activation were previously reported. In this study the regulatory mechanisms of EGCG on mTOR and Akt, 2 cancer survival signals, and the interrelationships among mTORC1, Akt, and AMPK were examined. It was found that the suppression of mTORC1 by EGCG requires signals from AMPK, however, the inhibition of Akt with EGCG seems to be AMPK independent. Further, there was no clear indication of Akt as an upstream regulator of mTOR in EGCG treated HT-29 colon cancer cells.

Highlights of This Issue

Molecular targeted therapies against signaling molecules active in cancer have shown incomplete and temporary clinical benefit when used as single agents. Roller and colleagues hypothesized that a functional chemical genetic screen could identify novel interactions between signaling inhibitors that would not be predicted based on the current understanding of signaling networks. Interestingly, the screen identified synergistic cytotoxicities that did not correlate with the RAS and BRAF mutational status. The authors uncovered novel functional drug combinations (including sorafenib, a multi-kinase inhibitor with activity against RAF, and diclofenac, a non-steroidal anti-inflammatory drug) and suggest that the underlying signaling networks that control responses to targeted agents can vary substantially depending on unexplored components of the cell genotype.EGF receptor (EGFR)–targeted monoclonal antibodies (mAb), such as cetuximab, execute their antitumor effect in vivo via blockade of receptor–ligand interactions and engagement of Fcg receptors on immune effector cells that trigger antibody-dependent cell-mediated cytotoxicity. Bedi and colleagues show that tumors counteract the in vivo antitumor activity of anti-EGFR mAbs by increasing tumor cell-autonomous expression of TGF-β and that TGF-β suppresses the expression of key molecular effectors of immune cell–mediated cytotoxicity. TGF-β is a key molecular determinant of the de novo and acquired resistance of cancers to EGFR-targeted mAbs, and provides a rationale for combinatorial targeting of TGF-β to improve anti-EGFR–specific antibody therapy of EGFR-expressing cancers.CC chemokine receptor 4, CCR4, is upregulated and is highly expressed in a large proportion of cutaneous T cell lymphoma (CTCL) and regulatory T cells (Tregs). To identify its antagonist antibody for cancer therapy, Chang and colleagues humanized and affinity maturated a mouse anti-CCR4 monoclonal antibody. This humanized antibody was highly specific to CCR4, exhibited the antagonist function to inhibit chemotaxis of Tregs, and enhanced therapeutic index in a CTCL xenograft model. The anti-CCR4 antibody additionally abrogates Treg function and activates proliferation of effector T cells. This multifunctional antibody may present a novel and promising cancer immunotherapy with immunomodulatory activity.In non-small cell lung cancer (NSCLC), platelet-derived growth factor receptor α (PDGFRα) is expressed frequently by stromal cells in the tumor microenvironment. However, previous research has focused largely on targeting tumor cell PDGFRα. To evaluate the effects of targeting tumor cell and stromal PDGFRα, Gerber and colleagues capitalized on xenograft modeling (human cancer cells, mouse stroma) and species-specific anti-PDGFRα monoclonal antibodies. Stromal PDGFRα inhibition attenuated tumor growth and enhanced the effect of chemotherapy in PDGFRα-negative NSCLC xenografts. These results suggest that inhibition of stromal PDGFRα may represent a means for enhancing control of lung cancer growth, independent of tumor cell PDGFRα expression.

Stromal Platelet-Derived Growth Factor Receptor α (PDGFRα) Provides a Therapeutic Target Independent of Tumor Cell PDGFRα Expression in Lung Cancer Xenografts

In lung cancer, platelet-derived growth factor receptor α (PDGFRα) is expressed frequently by tumor-associated stromal cells and by cancer cells in a subset of tumors. We sought to determine the effect of targeting stromal PDGFRα in preclinical lung tumor xenograft models (human tumor, mouse stroma). Effects of anti-human (IMC-3G3) and anti-mouse (1E10) PDGFRα monoclonal antibodies (mAb) on proliferation and PDGFRα signaling were evaluated in lung cancer cell lines and mouse fibroblasts. Therapy studies were conducted using established PDGFRα-positive H1703 cells and PDGFRα-negative Calu-6, H1993, and A549 subcutaneous tumors in immunocompromised mice treated with vehicle, anti-PDGFRα mAbs, chemotherapy, or combination therapy. Tumors were analyzed for growth and levels of growth factors. IMC-3G3 inhibited PDGFRα activation and the growth of H1703 cells in vitro and tumor growth in vivo, but had no effect on PDGFRα-negative cell lines or mouse fibroblasts. 1E10 inhibited growth and PDGFRα activation of mouse fibroblasts, but had no effect on human cancer cell lines in vitro. In vivo, 1E10-targeted inhibition of murine PDGFRα reduced tumor growth as single-agent therapy in Calu-6 cells and enhanced the effect of chemotherapy in xenografts derived from A549 cells. We also identified that low expression cancer cell expression of VEGF-A and elevated expression of PDGF-AA were associated with response to stromal PDGFRα targeting. We conclude that stromal PDGFRα inhibition represents a means for enhancing control of lung cancer growth in some cases, independent of tumor cell PDGFRα expression.

Control of Breast Cancer Growth and Initiation by the Stem Cell–Associated Transcription Factor TCF3

Regulatory factors controlling stem cell identity and self-renewal are often active in aggressive cancers and are thought to promote their growth and progression. TCF3 (also known as TCF7L1) is a member of the TCF/LEF transcription factor family that is central in regulating epidermal and embryonic stem cell identity. We found that TCF3 is highly expressed in poorly differentiated human breast cancers, preferentially of the basal-like subtype. This suggested that TCF3 is involved in the regulation of breast cancer cell differentiation state and tumorigenicity. Silencing of TCF3 dramatically decreased the ability of breast cancer cells to initiate tumor formation, and led to decreased tumor growth rates. In culture, TCF3 promotes the sphere formation capacity of breast cancer cells and their self-renewal. We found that in contrast to ES cells, where it represses Wnt-pathway target genes, TCF3 promotes the expression of a subset of Wnt-responsive genes in breast cancer cells while repressing another distinct target subset. In the normal mouse mammary gland, Tcf3 is highly expressed in terminal end buds, structures that lead duct development. Primary mammary cells are dependent on Tcf3 for mammosphere formation, and its overexpression in the developing gland disrupts ductal growth. Our results identify TCF3 as a central regulator of tumor growth and initiation, and a novel link between stem cells and cancer.

Targeting myeloid-derived suppressor cells augments antitumor activity against lung cancer

Lung cancer evades host immune surveillance by dysregulating inflammation. Tumors and their surrounding stromata produce growth factors, cytokines, and chemokines that recruit, expand, and/or activate myeloid-derived suppressor cells (MDSCs). MDSCs regulate immune responses and are frequently found in malignancy. In this review the authors discuss tumor-MDSC interactions that suppress host antitumor activities and the authors’ recent findings regarding MDSC depletion that led to improved therapeutic vaccination responses against lung cancer. Despite the identification of a repertoire of tumor antigens, hurdles persist for immune-based anticancer therapies. It is likely that combined therapies that address the multiple immune deficits in cancer patients will be required for effective therapy. MDSCs play a major role in the suppression of T-cell activation and they sustain tumor growth, proliferation, and metastases. Regulation of MDSC recruitment, differentiation or expansion, and inhibition of the MDSC suppressive function with pharmacologic agents will be useful in the control of cancer growth and progression. Pharmacologic agents that regulate MDSCs may be more effective when combined with immunotherapies. Optimization of combined approaches that simultaneously downregulate MDSC suppressor pathways, restore APC immune-stimulating activity, and expand tumor-reactive T cells will be useful in improving therapy.