Ann F. Chambers

London Health Sciences Centre, London, Ontario, Canada

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Publications (365)

  • Ann F Chambers
    Article · Aug 2016
  • [Show abstract] [Hide abstract] ABSTRACT: BackgroundTBX3 is a T-box transcription factor repressor that is elevated in metastatic breast cancer and is believed to promote malignancy of tumor cells, possibly by promoting cell survival and epithelial-mesenchymal transition. Methods The relative expression of TBX3 was assessed in the 21T cell lines which were derived from an individual patient and represent three distinct stages of breast cancer progression: 21PT, atypical ductal hyperplasia; 21NT, ductal carcinoma in situ; and 21MT-1, invasive mammary carcinoma. Two different isoforms of TBX3 (TBX3iso1 and TBX3iso2) were overexpressed to evaluate cell survival/colony forming ability, growth, and invasion in the ductal carcinoma in situ-like 21NT cell line using an in vitro Matrigel model of cancer progression. In addition, TBX3 expression was knocked down to evaluate the effects of downregulating TBX3 on the invasive mammary carcinoma-like 21MT-1 cell line. Finally, PCR array profiling was used to assess alterations in gene expression due to TBX3 overexpression in the 21NT cells. ResultsTBX3 is abundant in the invasive 21MT-1 cell line, while being minimally expressed in the non-invasive 21NT and 21PT cell lines. Overexpression of either TBX3iso1 or TBX3iso2 in 21NT cells resulted in increased cell survival/colony forming ability, growth vs. apoptosis and invasion in Matrigel. In contrast, short hairpin RNA-mediated knockdown of TBX3 in the 21MT-1 cells resulted in smaller colonies, with a more regular, less dispersed (less infiltrative) morphology. Array profiling of the 21NT TBX3 iso1 and iso2 transfectants showed that there are common alterations in expression of several genes involved in signal transduction, cell cycle control/cell survival, epithelial-mesenchymal transition and invasiveness. Conclusions Overall, these results indicate that TBX3 (isoform 1 or 2) expression can promote progression in a model of early breast cancer by altering cell properties involved in cell survival/colony formation and invasiveness, as well as key regulatory and EMT/invasiveness-related gene expressions.
    Article · Aug 2016 · BMC Cancer
  • Karla C Williams · Eugene Wong · Hon S Leong · [...] · Ann F Chambers
    [Show abstract] [Hide abstract] ABSTRACT: Cancer metastasis continues to be responsible for most cancer deaths. While much has been learned about molecular contributors to metastatic spread, the ability to effectively translate this knowledge to improved patient outcomes is still limited. Here we discuss various steps in the metastatic process from a physical sciences perspective, including hemodynamics pressure and forces in the circulatory system, sizes, half-lives and deformability of circulating tumor cells, physical aspects of cancer cell microvascular arrest, the role of adhesion and invadopodia in extravasation, and microparticles released by cancer cells during steps in metastasis. Awareness and improved understanding of the role of physical aspects of metastatic spread may offer new insights that may lead to new ways to better prevent, delay or treat metastatic disease.
    Article · Jun 2016
  • [Show abstract] [Hide abstract] ABSTRACT: The linear subtraction methods commonly used for preclinical contrast-enhanced imaging are susceptible to registration errors and motion artifacts that lead to reduced contrastto- tissue ratios. To address this limitation, a new approach to linear contrast-enhanced ultrasound (CEUS) is proposed based on analysis of the temporal dynamics of the speckle statistics during wash-in of a bolus injection of microbubbles. In the proposed method, the speckle signal is approximated as a mixture of temporally varying random processes, representing the microbubble signal, superimposed onto spatially heterogeneous tissue backscatter in multiple subvolumes within the region of interest. A wash-in curve is constructed by plotting the effective degrees of freedom (EDoF) of the histogram of the speckle signal as a function of time; the proposed method is therefore named the EDoF method. The EDoF parameter is proportional to the shape parameter of the Nakagami distribution. Images acquired at 18 MHz from a murine mammary fat pad breast cancer xenograft model were processed using gold-standard nonlinear amplitude modulation, conventional linear subtraction, and the proposed statistical method. The EDoF method shows promise for improving the robustness of linear CEUS based on reduced frame-toframe variability compared to conventional linear subtraction time-intensity curves. Wash-in curve parameters estimated using EDoF method also demonstrate higher correlation to nonlinear CEUS than the conventional linear method. The conceptual basis of the statistical method implies that EDoF wash-in curves may carry information about vascular complexity that could provide valuable new imaging biomarkers for cancer research.
    Article · Jun 2016 · IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control
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    [Show abstract] [Hide abstract] ABSTRACT: Introduction: The incidence of brain metastasis due to breast cancer is increasing, and prognosis is poor. Treatment is challenging because the blood-brain barrier (BBB) limits efficacy of systemic therapies. In this work, we develop a clinically relevant whole brain radiotherapy (WBRT) plan to investigate the impact of radiation on brain metastasis development and BBB permeability in a murine model. We hypothesize that radiotherapy will decrease tumor burden and increase tumor permeability, which could offer a mechanism to increase drug uptake in brain metastases. Methods: Contrast-enhanced magnetic resonance imaging (MRI) and high-resolution anatomical MRI were used to evaluate BBB integrity associated with brain metastases due to breast cancer in the MDA-MB-231-BR-HER2 model during their natural development. Novel image-guided microirradiation technology was employed to develop WBRT treatment plans and to investigate if this altered brain metastatic growth or permeability. Histology and immunohistochemistry were performed on whole brain slices corresponding with MRI to validate and further investigate radiological findings. Results: Herein, we show successful implementation of microirradiation technology that can deliver WBRT to small animals. We further report that WBRT following diagnosis of brain metastasis can mitigate, but not eliminate, tumor growth in the MDA-MB-231-BR-HER2 model. Moreover, radiotherapy did not impact BBB permeability associated with metastases. Conclusions: Clinically relevant WBRT is not curative when delivered after MRI-detectable tumors have developed in this model. A dose of 20 Gy in 2 fractions was not sufficient to increase tumor permeability such that it could be used as a method to increase systemic drug uptake in brain metastasis.
    Full-text Article · Jun 2016 · Translational oncology
  • [Show abstract] [Hide abstract] ABSTRACT: Cancer cell 'invasiveness' is one of the main driving forces in cancer metastasis, and assays that quantify this key attribute of cancer cells are crucial in cancer metastasis research. The research goal of many laboratories is to elucidate the signaling pathways and effectors that are responsible for cancer cell invasion, but many of these experiments rely on in vitro methods that do not specifically simulate individual steps of the metastatic cascade. Cancer cell extravasation is arguably the most important example of invasion in the metastatic cascade, whereby a single cancer cell undergoes transendothelial migration, forming invasive processes known as invadopodia to mediate translocation of the tumor cell from the vessel lumen into tissue in vivo. We have developed a rapid, reproducible and economical technique to evaluate cancer cell invasiveness by quantifying in vivo rates of cancer cell extravasation in the chorioallantoic membrane (CAM) of chicken embryos. This technique enables the investigator to perform well-powered loss-of-function studies of cancer cell extravasation within 24 h, and it can be used to identify and validate drugs with potential antimetastatic effects that specifically target cancer cell extravasation. A key advantage of this technique over similar assays is that intravascular cancer cells within the capillary bed of the CAM are clearly distinct from extravasated cells, which makes cancer cell extravasation easy to detect. An intermediate level of experience in injections of the chorioallantoic membrane of avian embryos and cell culture techniques is required to carry out the protocol.
    Article · May 2016 · Nature Protocol
  • Jennifer M Kirstein · M Nicole Hague · Patricia M McGowan · [...] · Ann F Chambers
    [Show abstract] [Hide abstract] ABSTRACT: Progression from a primary tumor to distant metastases requires extensive interactions between tumor cells and their microenvironment. The primary tumor is not only the source of metastatic cells but also can also modulate host responses to these cells, leading to an enhancement or inhibition of metastasis. Tumor-mediated stimulation of bone marrow can result in pre-metastatic niche formation and increased metastasis. However, a primary tumor can also inhibit metastasis through concomitant tumor resistance—inhibition of metastatic growth by existing tumor mass. Here, we report that the presence of a B16F10 primary tumor significantly restricted numbers and sizes of experimental lung metastases through reduction of circulating platelets and reduced formation of metastatic tumor cell-associated thrombi. Tumor-bearing mice displayed splenomegaly, correlated with primary tumor size and platelet count. Reduction in platelet numbers in tumor-bearing animals was responsible for metastatic inhibition, as restoration of platelet numbers using isolated platelets re-established both tumor cell-associated thrombus formation and experimental metastasis. Consumption of platelets due to a B16F10 primary tumor is a form of concomitant tumor resistance and demonstrates the systemic impact of a growing tumor. Understanding the interplay between primary tumors and metastases is essential, as clarification of concomitant tumor resistance mechanisms may allow inhibition of metastatic growth following tumor resection. Key messages Mice with a primary B16F10 tumor had reduced metastasis vs. mice without a primary tumor. Tumor-bearing mice had splenomegaly and fewer platelets and tumor-associated thrombi. Restoring platelets restored tumor-associated thrombi and increased metastasis. This work shows the impact that a primary tumor can have on systemic metastasis. Understanding these interactions may lead to improved ways to inhibit metastasis.
    Article · Apr 2016 · Journal of Molecular Medicine
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    [Show abstract] [Hide abstract] ABSTRACT: Background: Extracellular vesicles released by prostate cancer present in seminal fluid, urine, and blood may represent a non-invasive means to identify and prioritize patients with intermediate risk and high risk of prostate cancer. We hypothesize that enumeration of circulating prostate microparticles (PMPs), a type of extracellular vesicle (EV), can identify patients with Gleason Score≥4+4 prostate cancer (PCa) in a manner independent of PSA. Patients and methods: Plasmas from healthy volunteers, benign prostatic hyperplasia patients, and PCa patients with various Gleason score patterns were analyzed for PMPs. We used nanoscale flow cytometry to enumerate PMPs which were defined as submicron events (100-1000nm) immunoreactive to anti-PSMA mAb when compared to isotype control labeled samples. Levels of PMPs (counts/µL of plasma) were also compared to CellSearch CTC Subclasses in various PCa metastatic disease subtypes (treatment naïve, castration resistant prostate cancer) and in serially collected plasma sets from patients undergoing radical prostatectomy. Results: PMP levels in plasma as enumerated by nanoscale flow cytometry are effective in distinguishing PCa patients with Gleason Score≥8 disease, a high-risk prognostic factor, from patients with Gleason Score≤7 PCa, which carries an intermediate risk of PCa recurrence. PMP levels were independent of PSA and significantly decreased after surgical resection of the prostate, demonstrating its prognostic potential for clinical follow-up. CTC subclasses did not decrease after prostatectomy and were not effective in distinguishing localized PCa patients from metastatic PCa patients. Conclusions: PMP enumeration was able to identify patients with Gleason Score ≥8 PCa but not patients with Gleason Score 4+3 PCa, but offers greater confidence than CTC counts in identifying patients with metastatic prostate cancer. CTC Subclass analysis was also not effective for post-prostatectomy follow up and for distinguishing metastatic PCa and localized PCa patients. Nanoscale flow cytometry of PMPs presents an emerging biomarker platform for various stages of prostate cancer.
    Full-text Article · Jan 2016 · Oncotarget
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    Full-text Dataset · Jan 2016
  • Dalit Barkan · Ann F Chambers
    Chapter · Jan 2016
  • N. Zarghami · M.D. Jensen · S. Talluri · [...] · E. Wong
    [Show abstract] [Hide abstract] ABSTRACT: Purpose: Small animal immobilization devices facilitate positioning of animals for reproducible imaging and accurate focal radiation therapy. In this study, the authors demonstrate the use of three-dimensional (3D) printing technology to fabricate a custom-designed mouse head restraint. The authors evaluate the accuracy of this device for the purpose of mouse brain irradiation.
    Article · Nov 2015
  • Article · Nov 2015
  • Article · Aug 2015 · Cancer Research
  • Sean J. Leith · Ann F. Chambers · James B. McCarthy · [...] · Eva A. Turley
    Article · Aug 2015 · Cancer Research
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    [Show abstract] [Hide abstract] ABSTRACT: Brain metastases due to breast cancer are increasing, and the prognosis is poor. Lack of effective therapy is attributed to heterogeneity of breast cancers and their resulting metastases, as well as impermeability of the blood-brain barrier (BBB), which hinders delivery of therapeutics to the brain. This work investigates three experimental models of HER2+ breast cancer brain metastasis to better understand the inherent heterogeneity of the disease. We use magnetic resonance imaging (MRI) to quantify brain metastatic growth and explore its relationship with BBB permeability. Brain metastases due to breast cancer cells (SUM190-BR3, JIMT-1-BR3, or MDA-MB-231-BR-HER2) were imaged at 3 T using balanced steady-state free precession and contrast-enhanced T1-weighted spin echo sequences. The histology and immunohistochemistry corresponding to MRI were also analyzed. There were differences in metastatic tumor appearance by MRI, histology, and immunohistochemistry (Ki67, CD31, CD105) across the three models. The mean volume of an MDA-MB-231-BR-HER2 tumor was significantly larger compared to other models (F2,12 = 5.845, P < .05); interestingly, this model also had a significantly higher proportion of Gd-impermeable tumors (F2,12 = 22.18, P < .0001). Ki67 staining indicated that Gd-impermeable tumors had significantly more proliferative nuclei compared to Gd-permeable tumors (t[24] = 2.389, P < .05) in the MDA-MB-231-BR-HER2 model. CD31 and CD105 staining suggested no difference in new vasculature patterns between permeable and impermeable tumors in any model. Significant heterogeneity is present in these models of brain metastases from HER2+ breast cancer. Understanding this heterogeneity, especially as it relates to BBB permeability, is important for improvement in brain metastasis detection and treatment delivery. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Full-text Article · Jun 2015 · Translational oncology
  • Pieter H Anborgh · Laura Br Caria · Ann F Chambers · [...] · Muriel Brackstone
    [Show abstract] [Hide abstract] ABSTRACT: Osteopontin (OPN), a malignancy-associated secreted phosphoprotein, is a prognostic plasma biomarker for survival in metastatic breast cancer patients. We evaluated the role of OPN in Locally Advanced Breast Cancer (LABC) patients in predicting response to neoadjuvant chemotherapy and association with survival. Fifty-three patients with non-metastatic LABC were enrolled in this study and monitored serially for plasma OPN levels by ELISA during neoadjuvant chemotherapy prior to surgery. For fifty patients who had baseline OPN levels available for analysis, the median baseline OPN level was 63.6 ng/ml. Median patient follow up was 45 months and thirteen patients died from metastatic disease. Patients with baseline OPN levels ≥ 63.6 ng/ml were significantly more likely to die of their disease than those with baseline OPN < 63.6 ng/mL (Hazard Ratio = 3.4; 95% confidence interval 1.4-11.3; P = 0.011), and overall, baseline OPN level was significantly associated with survival (P = 0.002). There was little support for value of serial OPN determination in monitoring response to therapy in this patient population. Although the percentage of patients with baseline OPN levels < 63.6 ng/ml was higher in patients with pathological complete response than in those with no response, the difference was not statistically significant (64% and 14%, respectively (P = 0.066)). Thus, baseline plasma OPN level is a prognostic biomarker in this group of LABC patients, and could also be helpful in identifying LABC patients who will respond to neoadjuvant chemotherapy. Our results call for validation of our findings in large prospective trial data sets.
    Article · Jun 2015 · American Journal of Translational Research
  • [Show abstract] [Hide abstract] ABSTRACT: Clear cell renal cell carcinoma (ccRCC) is characterized by Von Hippel-Lindau (VHL)-deficiency, resulting in pseudohypoxic, angiogenic and glycolytic tumours. Hydrogen sulfide (H2S) is an endogenously-produced gasotransmitter that accumulates under hypoxia and has been shown to be pro-angiogenic and cytoprotective in cancer. It was hypothesized that H2S levels are elevated in VHL-deficient ccRCC, contributing to survival, metabolism and angiogenesis. Using the H2S-specific probe MeRhoAz, it was found that H2S levels were higher in VHL-deficient ccRCC cell lines compared to cells with wild-type VHL. Inhibition of H2S-producing enzymes could reduce the proliferation, metabolism and survival of ccRCC cell lines, as determined by live-cell imaging, XTT/ATP assay, and flow cytometry respectively. Using the chorioallantoic membrane angiogenesis model, it was found that systemic inhibition of endogenous H2S production was able to decrease vascularization of VHL-deficient ccRCC xenografts. Endogenous H2S production is an attractive new target in ccRCC due to its involvement in multiple aspects of disease. Copyright © 2015 Elsevier Inc. All rights reserved.
    Article · Jun 2015 · Nitric Oxide
  • Article · Apr 2015 · The Journal of Urology
  • Ann F Chambers · Zena Werb
    [Show abstract] [Hide abstract] ABSTRACT: IntroductionMost cancer deaths are due to metastasis—the spread of cancer from its site of origin to distant, vital organs—and the physiological damage caused by tumor growth in those organs. While the broad outlines of the process of metastatic spread are known, much of the details of the process remain poorly understood. To continue to improve cancer survival rates, we must face and tackle the problems inherent to metastatic disease. Cancers that are detected early, before they are believed to have spread to other organs, are generally treated with more success than cancers that are metastatic at diagnosis. However, even cancers that are detected early will recur in some patients, but our ability to predict which individuals will have recurrences is limited. Thus, adjuvant therapy is often given to patients with early-stage disease who are believed as a group to be at risk for recurrence, leading to overtreatment of some patients to benefit a subset of them and possibly failing to tr ...
    Article · Mar 2015 · Journal of Molecular Medicine
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    [Show abstract] [Hide abstract] ABSTRACT: Due to the high level of heterogeneity and mutations inherent in human cancers, single agent therapies, or combination regimens which target the same pathway, are likely to fail. Emphasis must be placed upon the inhibition of pathways that are responsible for intrinsic and/or adaptive resistance to therapy. An active field of investigation is the development and testing of DNA repair inhibitors that promote the action of, and prevent resistance to, commonly used chemotherapy and radiotherapy. We used a novel protocol to evaluate the effectiveness of BRCA2 inhibition as a means to sensitize tumor cells to the DNA damaging drug cisplatin. Tumor cell metabolism (acidification and respiration) was monitored in real-time for a period of 72 hr to delineate treatment effectiveness on a minute by minute basis. In combination, we performed an assessment of metastatic frequency using a chicken embryo chorioallantoic membrane (CAM) model of extravasation and invasion. This protocol addresses some of the weaknesses of commonly used in vitro and in vivo methods to evaluate novel cancer therapy regimens. It can be used in addition to common methods such as cell proliferation assays, cell death assays, and in vivo murine xenograft studies, to more closely discriminate amongst candidate targets and agents, and select only the most promising candidates for further development.
    Full-text Article · Feb 2015 · Journal of Visualized Experiments

Publication Stats

18k Citations

Institutions

  • 2001-2014
    • London Health Sciences Centre
      London, Ontario, Canada
  • 2003-2013
    • The University of Western Ontario
      • Department of Medical Biophysics
      London, Ontario, Canada
  • 2010
    • Massachusetts General Hospital
      Boston, Massachusetts, United States
  • 2006
    • KGK Synergize Inc.
      London, Ontario, Canada
    • The University of Calgary
      Calgary, Alberta, Canada
    • University of Sydney
      Sydney, New South Wales, Australia
  • 2004
    • Tom Baker Cancer Centre
      Calgary, Alberta, Canada
  • 2002-2004
    • University of South Florida
      • • Department of Surgery
      • • Department of Pathology and Cell Biology
      Tampa, Florida, United States