A Novel Class of Human ADAM8 Inhibitory Antibodies for Treatment of Triple-Negative Breast Cancer

New targeted treatments are urgently needed to improve triple-negative breast cancer (TNBC) patient survival. Previously, we identified the cell surface protein A Disintegrin And Metalloprotease 8 (ADAM8) as a driver of TNBC tumor growth and spread via its metalloproteinase and disintegrin (MP and DI) domains. In proof-of-concept studies, we demonstrated that a monoclonal antibody (mAb) that simultaneously inhibits both domains represents a promising therapeutic approach. Here, we screened a hybridoma library using a multistep selection strategy, including flow cytometry for Ab binding to native conformation protein and in vitro cell-based functional assays to isolate a novel panel of highly specific human ADAM8 dual MP and DI inhibitory mAbs, called ADPs. The screening of four top candidates for in vivo anti-cancer activity in an orthotopic MDA-MB-231 TNBC model of ADAM8-driven primary growth identified two lead mAbs, ADP2 and ADP13. Flow cytometry, hydrogen/deuterium exchange-mass spectrometry (HDX-MS) and alanine (ALA) scanning mutagenesis revealed that dual MP and DI inhibition was mediated via binding to the DI. Further testing in mice showed ADP2 and ADP13 reduce aggressive TNBC characteristics, including locoregional regrowth and metastasis, and improve survival, demonstrating strong therapeutic potential. The continued development of these mAbs into an ADAM8-targeted therapy could revolutionize TNBC treatment.

ADAM8 is expressed widely in breast cancer and predicts poor outcome in hormone receptor positive, HER-2 negative patients

BACKGROUND

Breast malignancies are the predominant cancer-related cause of death in women. New methods of diagnosis, prognosis and treatment are necessary. Previously, we identified the breast cancer cell surface protein ADAM8 as a marker of poor survival, and a driver of Triple-Negative Breast Cancer (TNBC) growth and spread. Immunohistochemistry (IHC) with a research-only anti-ADAM8 antibody revealed 34.0% of TNBCs (17/50) expressed ADAM8. To identify those patients who could benefit from future ADAM8-based interventions, new clinical tests are needed. Here, we report on the preclinical development of a highly specific IHC assay for detection of ADAM8-positive breast tumors.

METHODS

Formalin-fixed paraffin-embedded sections of ADAM8-positive breast cell lines and patient-derived xenograft tumors were used in IHC to identify a lead antibody, appropriate staining conditions and controls. Patient breast cancer samples (n = 490) were used to validate the assay. Cox proportional hazards models assessed association between survival and ADAM8 expression.

RESULTS

ADAM8 staining conditions were optimized, a lead anti-human ADAM8 monoclonal IHC antibody (ADP2) identified, and a breast staining/scoring control cell line microarray (CCM) generated expressing a range of ADAM8 levels. Assay specificity, reproducibility, and appropriateness of the CCM for scoring tumor samples were demonstrated. Consistent with earlier findings, 36.1% (22/61) of patient TNBCs expressed ADAM8. Overall, 33.9% (166/490) of the breast cancer population was ADAM8-positive, including Hormone Receptor (HR) and Human Epidermal Growth Factor Receptor-2 (HER2) positive cancers, which were tested for the first time. For the most prevalent HR-positive/HER2-negative subtype, high ADAM8 expression identified patients at risk of poor survival.

CONCLUSIONS

Our studies show ADAM8 is widely expressed in breast cancer and provide support for both a diagnostic and prognostic value of the ADP2 IHC assay. As ADAM8 has been implicated in multiple solid malignancies, continued development of this assay may have broad impact on cancer management.

Abstract 23: Antibody targeting of ADAM8 for treatment of triple-negative breast cancer

Triple-Negative Breast Cancer (TNBC) accounts for 25% of breast cancer deaths. Current therapeutic options are restricted to chemotherapy (CT) and radiation, which fail to block disease progression. Recently, we identified the cell surface protein ADAM8 as a critical driver of TNBC tumor growth and of metastasis in half of all breast cancers (EMBO Mol. Med. 6:278, 2014). Elevated ADAM8 levels correlate with poor breast cancer patient outcome. One third of TNBC patient samples have high ADAM8 levels, while it is undetectable in normal breast tissue. ADAM8 Metalloproteinase (MP) and Disintegrin (DI) domains promote angiogenesis needed for tumor growth, and cancer cell adhesion to and invasion through the endothelium needed for dissemination, respectively. Using a prototype reagent in mice, we validated a unique antibody-based strategy that simultaneously targets ADAM8 MP/DI activities as an effective therapeutic intervention in TNBC.

Our group has now prepared a panel of pre-clinical, highly specific anti-human ADAM8 mouse monoclonal antibodies (ADPs) of either IgG1 or IgG2 subclass with dual MP/DI antagonist activity. The top 6 ADPs bind ADAM8 with low dissociation constants of 1.3 x 10-9 M to 7.23 x 10-8 M. The 4 most effective inhibitory ADPs in cell-based assays were screened in a single-dose efficacy study (10 mg/kg 3x/wk) against pre-existing MDA-MB-231 cell-derived tumors (50-75 mm3). ADP2 and ADP13 treatment resulted in significant tumor volume reduction, of 47% and 52%, respectively. Dose-response curves are in progress. ADP13 was also tested in a neo-adjuvant model for its ability to reduce metastases. Antibody treatment was initiated as above and continued for 6 weeks after tumors were resected at a volume of ~200 mm3. Metastases in dissected organs were examined using biophotonic imaging. ADP13 substantially decreased metastasis to multiple organs. Lastly, a neo-adjuvant survival experiment was performed, as above, except that following surgical resection of tumors mice were treated for 12 weeks. Recurrence at the primary site was assessed using palpation. Mice were sacrificed when recurrent tumors reached 900 mm3. ADP13 treatment resulted in significantly improved disease-free survival (P=0.05) and overall survival (P=0.03). More recently, we noted that ADAM8 regulates miRNAs associated with resistance to CT and showed that ADAM8 inhibition sensitizes TNBC cells to Cisplatin, Paclitaxel, and Doxorubicin. In vivo testing of a combinatorial anti-ADAM8 + CT approach is in progress and may present a promising strategy for early entry into the clinic.

Conclusions: A new anti-ADAM8 antibody therapeutic shows efficacy against TNBC tumor growth and dissemination, and improves survival in pre-clinical testing. We hypothesize that addition of an anti-ADAM8 antibody to current CT standards of care will enhance tumor killing, reduce metastasis, and increase survival of patients with ADAM8-expressing TNBC.

Citation Format: Sonia G. Das, Stefania Pianetti, Gail E. Sonenshein, Nora D. Mineva. Antibody targeting of ADAM8 for treatment of triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 23. doi:10.1158/1538-7445.AM2017-23

Abstract 1137: ADAM8 drives aggressive phenotype of triple-negative inflammatory breast cancer & constitutes a novel therapeutic target

Inflammatory Breast Cancer (IBC) is a rare, highly aggressive form of cancer that is frequently locally advanced or metastasized at the time of diagnosis. The Triple-Negative subtype of IBC (TN-IBC), in particular, is characterized by very poor overall survival. TN-IBC lacks targeted therapies and is primarily treated with radiation or chemotherapy, which are inefficient. Recently, we identified the cell surface transmembrane ADAM8 (A Disintegrin and Metalloproteinase) protein as a driver of Triple-Negative Breast Cancer (TNBC) growth and metastasis via its Metalloproteinase (MP) and Disintegrin (DI) domains, respectively. In in vivo proof-of-concept experiments with a prototype reagent, we demonstrated that simultaneous, antibody-based, targeting of the ADAM8 MP and DI domains is an effective therapeutic approach for TNBC (Romagnoli et al., EMBO Mol. Med. 6:278, 2014).

The aggressive behavior of IBC cells has been attributed to a stem-like cancer cell compartment with high ALDH activity (ALDH+). Our studies of the green tea compound epigallocatechin-3 gallate (EGCG) revealed that it reduced growth of tumors derived from ALDH+ SUM-149 TN-IBC cells. We now report that EGCG concurrently decreases tumor levels of ADAM8 mRNA. This led us to assess the role of ADAM8 in TN-IBC. Tumor biopsies from 15 patients taken at the time of diagnosis and/or after neo-adjuvant treatment with chemotherapy, as well as paired lymph node and skin samples (when available) were analyzed by immunohistochemistry for ADAM8 expression. We report that 45.5% of primary TN-IBC patient tumors and 50.0% of metastases within the axillary lymph nodes express high levels of ADAM8 and its expression is largely unaffected by chemotherapy. In addition, ADAM8 expression was higher in the aggressive ALDH+ stem-like SUM-149 cell compartment. Consistently, knockdown of ADAM8 dramatically reduced the ability of SUM-149 cells to grow in an anchorage independent fashion and to migrate through Matrigel. A newly prepared anti-human ADAM8 mouse monoclonal antibody (ADP13) inhibited the MP and DI domains of ADAM8 on SUM-149 cells. ADP13 reduced orthotopic growth of tumors derived from SUM-149 cells by 40% in mice treated by i.p. injection 2 days a week with a dose of 4.5 mg/kg (n=7). Dose-response curves and survival experiments are in progress.

Conclusions: ADAM8 expression is present in almost half of TN-IBC patient tumors and their metastases, and promotes aggressive phenotype of TN-IBC cells in in vitro 3D-assays. A pre-clinical mouse model of TN-IBC validated ADAM8 as an accessible and promising new target for therapeutic intervention against this highly aggressive disease.

Citation Format: Mathilde Romagnoli, Stefania Pianetti, Sonia G. Das, Delphine Loussouarn, Carole Gourmelon, Mario Campone, Sophie Barillé-Nion, Giang T. Nguyen, Srimathi Srinivasan, Gail E. Sonenshein, Nora D. Mineva. ADAM8 drives aggressive phenotype of triple-negative inflammatory breast cancer & constitutes a novel therapeutic target [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1137. doi:10.1158/1538-7445.AM2017-1137

miR-720 is a downstream target of an ADAM8-induced ERK signaling cascade that promotes the migratory and invasive phenotype of triple-negative breast cancer cells

BACKGROUND

ADAM8 (a disintegrin and metalloproteinase 8) protein promotes the invasive and metastatic phenotype of triple-negative breast cancer (TNBC) cells. High ADAM8 expression in breast cancer patients is an independent predictor of poor prognosis. Here, we investigated whether ADAM8 regulates specific miRNAs, their roles in aggressive phenotype, and potential use as biomarkers of disease.

METHODS

Microarray analysis was performed on RNA from MDA-MB-231 cells after transient ADAM8 knockdown using TaqMan miRNA cards. Changes in miRNA levels were confirmed using two ADAM8 siRNAs in TNBC cell lines. Kinase inhibitors, β1-integrin antagonist antibody, and different forms of ADAM8 were employed to elucidate the signaling pathway required for miR-720 expression. miR-720 levels were modulated using a specific antagomiR or a mimic, and effects on aggressive phenotype of TNBC cells were determined using Boyden chamber and 3D-Matrigel outgrowth assays. Plasma was isolated from mice before and after implantation of MDA-MB-231 cells and analyzed for miR-720 levels. Serum samples of TNBC patients were evaluated for their ADAM8 and miR-720 levels.

RESULTS

We identified 68 miRNAs differentially regulated upon ADAM8 knockdown, including decreased levels of secreted miR-720. Ectopic overexpression of wild-type ADAM8 or forms that lack metalloproteinase activity similarly induced miR-720 levels. The disintegrin and cysteine-rich domains of ADAM8 were shown to induce miR-720 via activation of a β1-integrin to ERK signaling cascade. Knockdown of miR-720 led to a significant decrease in migratory and invasive abilities of TNBC cells. Conversely, miR-720 overexpression rescued these properties. A profound increase in plasma levels of miR-720 was detected 7 days after TNBC cell inoculation into mouse mammary fat pads when tumors were barely palpable. Concordantly, miR-720 levels were found to be significantly higher in serum samples of TNBC patients with high ADAM8 expression.

CONCLUSIONS

We have shown for the first time that miR-720 is induced by ADAM8 signaling via ERK and plays an essential role in promoting the aggressive phenotype of TNBCs. miR-720 is elevated in serum of patients with ADAM8-high TNBC and, in a group with other miRNAs downstream of ADAM8, holds promise as a biomarker for early detection of or treatment response of ADAM8-positive TNBCs.

Endogenous light scattering as an optical signature of circulating tumor cell clusters

Circulating tumor cell clusters (CTCCs) are significantly more likely to form metastases than single tumor cells. We demonstrate the potential of backscatter-based flow cytometry (BSFC) to detect unique light scattering signatures of CTCCs in the blood of mice orthotopically implanted with breast cancer cells and treated with an anti-ADAM8 or a control antibody. Based on scattering detected at 405, 488, and 633 nm from blood samples flowing through microfluidic devices, we identified 14 CTCCs with large scattering peak widths and intensities, whose presence correlated strongly with metastasis. These initial studies demonstrate the potential to detect CTCCs via label-free BSFC.

ADAM8 expression in invasive breast cancer promotes tumor dissemination and metastasis

The transmembrane metalloprotease-disintegrin ADAM8 mediates cell adhesion and shedding of ligands, receptors and extracellular matrix components. Here, we report that ADAM8 is abundantly expressed in breast tumors and derived metastases compared to normal tissue, especially in triple-negative breast cancers (TNBCs). Furthermore, high ADAM8 levels predicted poor patient outcome. Consistently, ADAM8 promoted an aggressive phenotype of TNBC cells in culture. In a mouse orthotopic model, tumors derived from TNBC cells with ADAM8 knockdown failed to grow beyond a palpable size and displayed poor vascularization. Circulating tumor cells and brain metastases were also significantly reduced. Mechanistically, ADAM8 stimulated both angiogenesis through release of VEGF-A and transendothelial cell migration via β1-integrin activation. In vivo, treatment with an anti-ADAM8 antibody from the time of cell inoculation reduced primary tumor burden and metastases. Furthermore, antibody treatment of established tumors profoundly decreased metastases in a resection model. As a non-essential protein under physiological conditions, ADAM8 represents a promising novel target for treatment of TNBCs, which currently lack targeted therapies and frequently progress with fatal dissemination.

Abstract B166: MicroRNAs downstream of ADAM8 as therapeutic targets and non-invasive biomarkers for triple-negative breast cancer

Triple-negative breast cancer (TNBC) represents ∼20% of breast cancers, is highly aggressive and lacks targeted therapies due to the absence of hormone and HER2 receptors. TNBCs respond only poorly to chemotherapy and recur more frequently than other breast cancers. Their recurrence often involves distant metastasis, especially to the brain and lungs with a poor prognosis, which lead to approximately 25% of the half million yearly deaths worldwide from breast cancer. Thus, there is a critical unmet need for early detection and new therapeutic targets for TNBC treatment, which was the focus of our current study. Recently, our lab has shown that the transmembrane protein ADAM8 (A Disintegrin And Metalloproteinase 8) plays a key role in invasion and metastasis of TNBCs and high ADAM8 levels correlate with a poor prognosis in breast cancer patients. MicroRNAs (miRNAs) play important functions in both normal and disease development. It is estimated that more than 60% of the protein-coding genes in the human genome are regulated by miRNAs. Furthermore, circulating tumor cell-associated miRNAs and free circulating miRNAs have been identified in whole blood, plasma and serum in various cancer subtypes. Here we tested two related hypotheses, that: (1) miRNAs regulated by the ADAM8 pathway are important mediators promoting invasion and migration of TNBC cells; and (2) these miRNAs represent potential therapeutic targets and/or noninvasive biomarkers for detection of TNBC recurrence. A microarray analysis was performed using TaqMan microRNA cards on RNA isolated from MDA-MB-231 cells after 72 h of transient siRNA-mediated knockdown of ADAM8. We identified 68 miRNAs that were differentially regulated upon ADAM8 knockdown. Thus far we have confirmed 13 miRNAs using real-time PCR. Of the miRNAs confirmed, miR-720 was selected as the initial candidate of study, since it has been previously identified as an oncomiR and also detected in blood from breast cancer patients. Transient ectopic ADAM8 overexpression in MDA-MB-231 and SUM149 TNBC cell lines induced levels of miR-720 whereas ADAM8 siRNA reduced them. Furthermore, knockdown of miR-720 using an antagomiR led to a significant decrease of the migratory and invasive phenotype of TNBC cells as judged by Boyden chamber and 3D Matrigel outgrowth assays, respectively. Consistently, we used a miRNA mimic to overexpress miR-720 activity and observed increased migration and invasion of TNBC cells. Importantly, a profound increase in levels of miR-720 was detected in the plasma of mice bearing orthotopic mammary tumors derived from control shRNA-MDA-MB-231 cells in contrast to shADAM8-MDA-MB-231 cells and non-tumor bearing mice, which suggests that miR-720 levels in blood correlate with ADAM8 expression in tumors. Taken together our data indicates that the miR-720 is induced by ADAM8 and miRNAs regulated downstream of ADAM8 have a strong potential as both biomarkers and therapeutic targets for the treatment of TNBC.

Research was funded by grants from the DOD (W81XWH-11-1-0814) and the NIH (R01 CA129129)

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B166.

Citation Format: Sonia G. Das, Mathilde Romagnoli, Nora D. Mineva, Gail E. Sonenshein. MicroRNAs downstream of ADAM8 as therapeutic targets and non-invasive biomarkers for triple-negative breast cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B166.

Epigallocatechin-3-gallate inhibits stem-like inflammatory breast cancer cells

Inflammatory Breast Cancer (IBC) is a highly aggressive form of cancer characterized by high rates of proliferation, lymphangiogenesis and metastasis, and an overall poor survival. As regular green tea consumption has been associated with improved prognosis of breast cancer patients, including decreased risk of recurrence, here the effects of the green tea polyphenol epigallocatechin-3-gallate (EGCG) were tested on two IBC lines: SUM-149 and SUM-190. EGCG decreased expression of genes that promote proliferation, migration, invasion, and survival. Consistently, growth, invasive properties, and survival of IBC cells were reduced by EGCG treatment. EGCG also reduced lymphangiogenesis-promoting genes, in particular VEGF-D. Conditioned media from EGCG-treated IBC cells displayed decreased VEGF-D secretion and reduced ability to promote lymphangiogenesis in vitro as measured by hTERT-HDLEC lymphatic endothelial cell migration and tube formation. Tumorsphere formation by SUM-149 cells was robustly inhibited by EGCG, suggesting effects on self-renewal ability. Stem-like SUM-149 cells with high aldehyde dehydrogenase (ALDH) activity, previously implicated in poor patient prognosis, were isolated. EGCG treatment reduced growth and induced apoptosis of the stem-like SUM-149 cells in culture. In an orthotopic mouse model, EGCG decreased growth of pre-existing tumors derived from ALDH-positive stem-like SUM-149 cells and their expression of VEGF-D, which correlated with a significant decrease in peritumoral lymphatic vessel density. Thus, EGCG inhibits the overall aggressive IBC phenotype. Reduction of the stem-like cell compartment by EGCG may explain the decreased risk of breast cancer recurrence among green tea drinkers. Recent clinical trials demonstrate the efficacy of green tea polyphenol extracts in treatment of prostate cancer and lymphocytic leukemia with low toxicity. Given the poor prognosis of IBC patients, our findings suggest further exploration of EGCG or green tea in combinatorial treatments against active IBC disease or in maintenance regimens to avoid recurrence is warranted.

Abstract B62: ADAM8 promotes tumorigenesis, angiogenesis, and spreading of circulating tumor cells in breast cancer

ADAM (a disintegrin and metalloprotease) proteins mediate cell adhesion and shedding of receptors and proteins of the extracellular matrix via their disintegrin and metalloproteinase domains, respectively. Recently, using microarray analysis we identified ADAM8 as a target of a pathway mediated by NF-κB RelB/Ras to B lymphocyte-induced maturation protein (Blimp-1) that promotes a more aggressive breast cancer cell phenotype. ADAM8 is a membrane-anchored protein that is synthesized as a pro-form and needs to multimerize to autocatalytically clip off its prodomain leaving an active processed form. Using the Oncomine and bc-GenExMiner databases, ADAM8 mRNA levels were found overexpressed in invasive breast tumors compared to normal breast tissue, and high ADAM8 levels were correlated with metastatic relapse in breast cancer patients. As ADAM8 is not essential under physiological conditions as evidenced by the lack of phenotype in ADAM8 deficient mice, here we tested the hypothesis that ADAM8 represents a novel target for the treatment of aggressive breast cancer. Immunohistochemical analysis revealed that ADAM8 is abundantly expressed in 34.0% (17/50) of triple-negative breast tumors and in 48.2% (27/56) of breast cancer metastases. In particular, ADAM8 was highly expressed in brain metastases (63.0%). In contrast, ADAM8 was not observed in normal mammary tissue and was only detected in 13.5% of Ductal Carcinoma In Situ tumors. Consistently, we found that ADAM8 promotes aggressive breast cancer cell behavior in culture. ADAM8 siRNA knockdown reduced the migratory and invasive properties of triple-negative breast cancer lines MDA-MB-231 and Hs578T in Boyden chamber and 3D Matrigel assays. MDA-MB-231 clones stably expressing an ADAM8 shRNA or Control shRNA showed equal rates of growth and survival in vitro. However, when these clones were used in a mammary fat pad mouse model (n=7/group), tumors derived from ADAM8 shRNA MDA-MB-231 clone uniformly failed to grow significantly beyond a palpable size over the 33 day-time course in contrast to the Control shRNA clone (0.08 g versus 2.0 g). Angiogenesis was also significantly decreased in ADAM8 shRNA cell-derived tumors as measured by CD31 staining. As the clones were stably expressing Green Fluorescent Protein, spreading of circulating tumor cells (CTCs) into the blood was analyzed by flow cytometry. The CTC numbers in mice bearing ADAM8 shRNA tumors did not exceed background level. In contrast, the Control shRNA group showed a high number of CTCs. To address the mechanism causing tumorigenesis and tumor cell spreading, we investigated the effects of hypoxia, which is an early event that promotes tumor angiogenesis. In vitro, hypoxia (1% oxygen) induced levels of ADAM8 pro-form and processed protein by ~3-fold in the Control shRNA clone, but not in the ADAM8 shRNA clone. As an early step in migration of cancers cells requires β1-integrin activation, we tested the effects of ADAM8 knockdown. Immunofluorescence demonstrated an essential role of ADAM8 in activation of β1-integrin in the MDA-MB-231 clones. Consistently, expression and activity of the matrix metalloprotease MMP-9, which is induced downstream of β1-integrin pathway, were reduced by ADAM8 knockdown, suggesting this is an essential pathway whereby ADAM8 promotes matrix remodeling and angiogenesis. Despite recent advances in diagnosis and treatment of breast cancer, in many patients the disease still progresses to invasive carcinoma with fatal metastatic spread of primary tumors to distant organs. Our findings suggest that ADAM8 constitutes a promising new target for the treatment of these aggressive breast cancers.

Citation Format: Mathilde Romagnoli, Nora D. Mineva, Delphine Loussouarn, Sophie Barillé-Nion, Mike Polmear, Irene Georgakoudi, Catharina Conrad, Uwe Schlomann, Joerg W. Bartsch, Maddy Parsons, Gail E. Sonenshein. ADAM8 promotes tumorigenesis, angiogenesis, and spreading of circulating tumor cells in breast cancer. [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 B62.

Abstract A94: Epigallocatechin-3-gallate inhibits stem-like inflammatory breast cancer cells

Inflammatory Breast Cancer (IBC) is a highly aggressive form of cancer characterized by an unusual growth pattern with nests of tumor emboli rather than a solid mass, rapid spread via lymphatic dissemination and high proliferative rates. Multi-modality therapies have improved survival but the outcome still remains poorer for these patients. Given the potent anti-cancer properties of green tea polyphenols, including epigallocatechin-3-gallate (EGCG), here we tested the hypothesis that EGCG inhibits IBC cells. Two IBC cell lines were studied. SUM-149 cells have a triple negative receptor status (ER-, PR-, Her-2-), while SUM-190 cells are ER-, PR- and Her-2 amplified. Doses of EGCG used ranged from 5 μg/ml (10.9 μM) to 160 μg/ml (349.1 μM), depending upon the presence of serum which inactivates the polyphenol. Treatment with 40 μg/ml (87.3 μM) EGCG decreased mRNA expression of genes that promote migration and invasion (RHOC, FN1, CDH1 and VIM), lymphangiogenesis (VEGF-D), proliferation (CCND1), and survival (BCL-XL) in both lines. Consistently, EGCG treatment resulted in decreased invasive phenotype, ability for anchorage independent growth and viability, as judged by Matrigel outgrowth, soft agar colony assays and ATP assays. Substantial apoptosis was detected starting at 80 μg/ml (174.5 μM) and 160 μg/ml (349.1 μM) of EGCG for SUM-149 and SUM-190 cells, respectively. Conditioned media isolated from EGCG-treated IBC cells displayed decreased secretion of the pro-lymphangiogenic factor VEGF-D and reduced ability to promote cultured hTERT-HDLEC lymphatic endothelial cell migration in wound healing assays and tube formation in Matrigel, processes critical for lymphangiogenesis. The poor clinical outcome of IBC patients has been attributed to a stem-like cell compartment, which is characterized by increased aldehyde dehydrogenase (ALDH) activity. The SUM-149, but not the SUM-190, line has been reported to contain such a stem-like compartment. EGCG treatment inhibited SUM-149 cell spheroid formation and decreased the size of pre-formed spheroids, suggesting efficacy on the cancer stem-like cells. ALDH-positive SUM-149 cells were isolated using an ALDEFUOR Fluorescence Activated Cell Sorting-based assay. EGCG treatment of these cells led to a significant dose-dependent decrease in ATP levels. Furthermore, doses of 80 and 160 μg/ml EGCG induced apoptosis, as judged by increased Caspase-3 and -7 activities. ALDH-positive SUM-149 cancer stem-like cells were used in an orthotopic mammary fat pad mouse model (n = 6/ group). After 25 days, palpable tumors were detected in all of the mice. The experimental group was given a 0.1 ml intraperitoneal injection of 16.5 mg/kg EGCG while the control group was injected with vehicle 1X PBS. Treatment was administered five times a week for five weeks and then daily for one last week for a total of 43 days. EGCG significantly reduced the growth of pre-existing tumors derived from ALDH-positive stem-like SUM-149 cells such that at the end of the experiment a 37.7 ± 4.4% decrease in tumor volume was seen in the EGCG-treated vs control groups. RT-PCR and immunoblot analyses revealed substantially reduced expression of VEGF-D RNA and VEGF-D protein within tumor tissues of EGCG-treated vs control animals, which correlated with a trend toward decreased peritumoral lymphatic vessel density. Thus, EGCG has pleiotropic inhibitory effects on IBC cells, including the cancer stem-like cell compartment believed to be responsible for recurrence. Recent clinical trials using various green tea polyphenol preparations have shown efficacy in treatment of prostate cancer and lymphocytic leukemia, and low toxicity. Our studies suggest the use of EGCG or green tea in combination with standard therapeutic modalities for IBC patients warrants further exploration.

Citation Format: Nora D. Mineva, K. Eric Paulson, Stephen P. Naber, Amy S. Yee, Gail E. Sonenshein. Epigallocatechin-3-gallate inhibits stem-like inflammatory breast cancer cells. [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 A94.

Inhibition of RelB by 1,25-dihydroxyvitamin D3 promotes sensitivity of breast cancer cells to radiation

Aberrant constitutive expression of the NF-kappaB c-Rel and RelA subunits in breast cancer cells was shown to promote their survival. Recently, we demonstrated that aggressive breast cancers constitutively express high levels of the RelB subunit, which promotes their more invasive phenotype via induction of the BCL2 gene. As these cancers are frequently resistant to therapy, here we tested the hypothesis that RelB promotes their survival. High RelB expressing Hs578T and MDA-MB-231 breast cancer cells were more resistant to gamma-radiation than MCF7 and ZR-75 cells, which express lower RelB levels. Knockdown of RelB in Hs578T led to decreased survival in response to gamma-irradiation, while conversely ectopic expression of RelB in MCF7 cells protected these cells from radiation. Similar data were obtained upon treatment of Hs578T or MCF7 cells with the chemotherapeutic agent doxorubicin. High serum levels of 25-hydroxyvitamin D are associated with decreased breast cancer risk and mortality, although, the mechanisms of its protective actions have not been fully elucidated. Treatment of Hs578T and Her-2/neu-driven NF639 cells with 1,25-dihydroxyvitamin D3 decreased RelB/RELB gene expression and levels of pro-survival targets Survivin, MnSOD and Bcl-2, while increasing their sensitivity to gamma-irradiation. Thus, RelB, which promotes survival and a more highly invasive phenotype of breast cancer cells, is a target of 1,25-dihydroxyvitamin D3, providing one mechanism for the observed protective role of 25-hydroxyvitamin D in patients with breast cancer.

c-Myc represses FOXO3a-mediated transcription of the gene encoding the p27(Kip1) cyclin dependent kinase inhibitor

The p27(Kip1) (p27) cyclin-dependent kinase inhibitor and c-Myc oncoprotein play essential roles in control of cell cycle progression and apoptosis. Induction of p27 (CDKN1B) gene transcription by Forkhead box O proteins such as FOXO3a leads to growth arrest and apoptosis. Previously, we observed that B cell receptor (surface IgM) engagement of WEHI 231 immature B lymphoma cells with an anti-IgM antibody results in activation of FOXO3a, growth arrest and apoptosis. As ectopic c-Myc expression in these cells prevented anti-IgM induction of p27 and cell death, we hypothesized that c-Myc represses FOXO3a-mediated transcription. Here we show that c-Myc inhibits FOXO3a-mediated activation of the p27 promoter in multiple cell lines. The mechanism of this repression was explored using a combination of co-immunoprecipitation, oligonucleotide precipitation, and chromatin immunoprecipitation experiments. The studies demonstrate a functional association of FOXO3a and c-Myc on a proximal Forkhead binding element in the p27 promoter. This association involves the Myc box II domain of c-Myc and the N-terminal DNA-binding portion of FOXO3a. Analysis of publicly available microarray datasets showed an inverse pattern of c-MYC and p27 RNA expression in primary acute myeloid leukemia, prostate cancer and tongue squamous cell carcinoma samples. The inhibition of FOXO3a-mediated activation of the p27 gene by the high aberrant expression of c-Myc in many tumor cells likely contributes to their uncontrolled proliferation and invasive phenotype.

CD40 ligand-mediated activation of the de novo RelB NF-kappaB synthesis pathway in transformed B cells promotes rescue from apoptosis

CD40, a tumor necrosis factor receptor family member, is expressed on B lymphocytes. Interaction between CD40 and its ligand (CD40L), expressed on activated T lymphocytes, is critical for B cell survival. Here, we demonstrate that CD40 signals B cell survival in part via transcriptional activation of the RelB NF-kappaB subunit. CD40L treatment of chronic lymphocytic leukemia cells induced levels of relB mRNA. Similarly, CD40L-mediated rescue of WEHI 231 B lymphoma cells from apoptosis induced upon B cell receptor (surface IgM) engagement led to increased relB mRNA levels. Recently, we characterized a new de novo synthesis pathway for the RelB NF-kappaB subunit, induced by the cytomegalovirus IE1 protein, in which binding of p50/p65 NF-kappaB and c-Jun/Fra-2 AP-1 complexes to the relB promoter works in synergy to potently activate transcription (Wang, X., and Sonenshein, G. E. (2005) J. Virol. 79, 95-105). CD40L treatment of WEHI 231 cells caused induction of AP-1 family members Fra-2, c-Jun, JunD, and JunB. Cotransfection of Fra-2 with the Jun AP-1 subunits and p50/c-Rel NF-kappaB led to synergistic activation of the relB promoter. Ectopic expression of relB or RelB knockdown using small interfering RNA demonstrated the important role of this subunit in control of WEHI 231 cell survival and implicated activation of the anti-apoptotic factors Survivin and manganese superoxide dismutase. Thus, CD40 engagement of transformed B cells activates relB gene transcription via a process we have termed the de novo RelB synthesis pathway, which protects these cells from apoptosis.

Oestrogen signalling inhibits invasive phenotype by repressing RelB and its target BCL2

Aberrant constitutive expression of c-Rel, p65 and p50 NF-kappaB subunits has been reported in over 90% of breast cancers. Recently, we characterized a de novo RelB NF-kappaB subunit synthesis pathway, induced by the cytomegalovirus (CMV) IE1 protein, in which binding of p50-p65 NF-kappaB and c-Jun-Fra-2 AP-1 complexes to the RELB promoter work in synergy to potently activate transcription. Although RelB complexes were observed in mouse mammary tumours induced by either ectopic c-Rel expression or carcinogen exposure, little is known about RelB in human breast disease. Here, we demonstrate constitutive de novo RelB synthesis is selectively active in invasive oestrogen receptor alpha (ERalpha)-negative breast cancer cells. ERalpha signalling reduced levels of functional NF-kappaB and Fra-2 AP-1 and inhibited de novo RelB synthesis, leading to an inverse correlation between RELB and ERalpha gene expression in human breast cancer tissues and cell lines. Induction of Bcl-2 by RelB promoted the more invasive phenotype of ERalpha-negative cancer cells. Thus, inhibition of de novo RelB synthesis represents a new mechanism whereby ERalpha controls epithelial to mesenchymal transition (EMT).

Identification of genes potentially involved in the acquisition of androgen-independent and metastatic tumor growth in an autochthonous genetically engineered mouse prostate cancer model

BACKGROUND

A major focus of prostate cancer research has been to identify genes that are deregulated during tumor progression, potentially providing diagnostic markers and therapeutic targets.

METHODS

We have employed serial analysis of gene expression (SAGE) and microarray hybridization to identify alterations that occur during malignant transformation in the Transgenic Adenocarcinoma of the Mouse Prostate (TRAMP) model. Many of these alterations were validated by real-time PCR (rtPCR).

RESULTS

We identified several hundred mRNAs that were deregulated. Cluster analysis of microarray profiles with samples from various stages of the disease demonstrated that androgen-independent (AI) primary tumors are similar to metastases; 180 transcripts have expression patterns suggesting an involvement in the genesis of late-stage tumors, and our data support a role for phospholipase A2 group IIA in the acquisition of their highly aggressive characteristics.

CONCLUSIONS

Our analyses identified well-characterized genes that were previously known to be involved in prostate cancer, validating our study, and also uncovered transcripts that had not previously been implicated in prostate cancer progression.