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Research Grants Awarded
Development of Second Harmonic Generation Imaging for Intravital Monitoring of Mammary Tumorigenesis and Tumor-Stromal Interactions
Extracellular matrix (ECM) breakdown is a hallmark of invasive breast cancer, distinguishing ductal carcinoma in situ from invasive ductal carcinoma. Critical molecules in this process include collagens, other matrix proteins, matrix-degrading enzymes and their tissue inhibitors. In parallel, mouse models provide the means to study breast cancer development in a systematic manner and in the whole organ context. However, the ability to visualize matrix scaffold integrity and breakdown in vivo is lacking. Recent developments in optical second harmonic generation (SHG) imaging technologies have made visualization of ECM structure feasible, and offer the potential for studying cell-matrix interactions in vivo. SHG imaging allows for quantitative, qualitative and spatial information to be obtained from the ECM scaffold in vivo in real time. In addition, the appropriate labeling of different cellular compartments allows for further elucidation of the mechanisms behind matrix breakdown and ductal invasion. This proposal applies the cutting-edge SHG technology to imaging stromal changes during breast cancer development in mouse models. We hypothesize that SHG imaging of fibrillar collagen will provide a powerful method for visualizing dynamic changes in the tumor microenvironment during tumor development and invasion. Specifically, our goals are to i) elucidate the dynamics of ECM remodeling during mammary tumorigenesis; and ii) dissect the role of the matrix-bound ECM regulator timp3 (tissue inhibitor of metalloproteinase 3) in tumor suppression observed in timp3-/- mice, and iii) using quantum dot labeling, determine how immune cell infiltrates can play a role in mediating tumor progression, or in mediating tumor suppression due to the loss of timp3. Adaptation of these sophisticated imaging tools to monitor dynamic changes in breast cancer will provide critical knowledge of tissue structure and microenvironment during mammary epithelial transformation and tumor progression. Revealing ECM integrity and cell-ECM interactions in a minimally invasive manner will lay the groundwork towards future development of an optical biopsy to complement conventional techniques like mammography and needle biopsy.
Breast cancer is the second most common cause of cancer mortality in North American women. The breakdown of connective tissue components within the breast leads to the spread of breast cancer away from its initial site of formation. This local invasion is an important indicator of cancer progression, thus techniques that could monitor the integrity of the connective tissue surrounding these mammary ducts would be a useful addition to tools currently available for the diagnosis and staging of breast cancer. We propose to apply a new technique being developed in microscopy, second harmonic generation (SHG), to studying mouse models of breast cancer, in order to determine the applicability of this technique to studying connective tissue breakdown and thus cancer progression. Specifically, we plan to use mouse models that spontaneously develop breast cancer, in combination with mice that lack an important regulator of connective tissue integrity, timp3 (tissue inhibitor of metalloproteinase 3), to study this process. We have found that crossbreeding these mice which spontaneously develop breast cancer with those that are missing the timp3 gene results in the suppression of tumor growth. We plan to use SHG imaging to determine the mechanism behind this cancer suppression, while at the same time figuring out what structural changes taking place within the connective tissue are possible to image using this technology. In addition to the imaging of connective tissue, we also have the ability to label and monitor the behavior of cancer cells and immune cells, in order to determine the effect that the immune system has on tumor progression, or on tumor suppression due to timp3 loss. This study will show the potential for using SHG imaging to complement current diagnostic tools, revealing the benefits and drawbacks to this novel imaging method. This study will also attempt to determine the mechanism behind cancer suppression in mice lacking timp3, by focusing on imaging techniques to monitor duct breakdown, cancer cell invasion, and immune cell behavior. The results from this study could help point towards future potential therapeutic targets that may influence both the immune and connective tissue components of the breast.