Research
Laboratory for Intravital Imaging and Dynamics of Tumor Progression
We study the dynamics of tumor progression at multiple scales ranging from the molecular level to the organ level. During this process, the affected organ transforms from a highly organized and functional structure into a disorganized and dysfunctional assembly of cells. Our goal is to understand how healthy tissue architecture is involved in this dynamic process of tumorigenic transformation. Better understanding of the interplay between healthy tissue structure and transformed cells will give us new insights into how tissue architecture can either prevent or promote tumor initiation and progression. Ultimately, we aim to use these new insights to explore new therapeutic strategies that could delay or even prevent tumor progression.
Tissues have several barriers to protect themselves against damage or mutation accumulation and subsequent (pre-)malignant transformation. Although the most obvious protection against malignant transformation is to be post-mitotic, even epithelial tissues with high turnover are well protected against oncogenic mutation accumulation. The first barrier is the cellular organization: many tissues are organized in a hierarchical manner, with a minority population of self-renewing stem cells giving rise to a large population of short-lived differentiated cells. Since the vast majority of cells is short-lived, mutations in these cells will eventually be lost. Only when mutations occur in one of the few stem cells, the mutation can be retained in the tissue. Fortunately, tissues do not depend on just one stem cell, and at the multi-cellular level stem cells continuously compete for niche signals and space. As a result of this stem cell competition, mutant stem cells can be outcompeted against wild-type stem cells and will eventually be lost due to tissue turnover, which provides a second barrier against mutation accumulation. Even if a mutation confers a survival advantage and is retained in the stem cell compartment, tissues are often compartmentalized into distinct stem-progenitor cell units, which strongly limits the expansion of such a mutant cell clone.
Visualizing tumorigenesis in real-time
In order for a tumor to initiate, progress, and eventually metastasize, these natural tissue barriers are overruled by the cancer cells. However, little is known about the mechanisms and dynamics by which transformed cells eliminate, rearrange or adopt the existing tissue structures.
To investigate the dynamics of these complex tissue rearrangements, we develop and use state-of-the-art imaging techniques, such as whole organ 3D imaging (Hannezo and Scheele, Mothods Molecular Biology, 2023), and high-resolution intravital microscopy (Scheele et al., Nature Reviews Methods Primers, 2022), and combine these techniques with the latest genetic mouse models. To gain visual access to the tissues we use small imaging windows (Mourao et al., JoVE, 2022; Messal et al., Journal of Mammary Gland Biology and Neoplasia, 2021) that can be surgically implanted into mice. These windows enable visualization of the behavior of individual tumor cells within the tissue context. Moreover, malignant transformation can be followed at the single cell level in real-time within the primary tumor or at distant organs over a period of several days to weeks (van Rheenen and Scheele, Current Opinion in Cell Biology, 2021; Rios et al., CSH Perspectives in Medicine, 2023).
Intravital movie of mammary epithelial cells remodeling a side branch within the mammary gland.
To fully understand the complex interplay between healthy tissue organization and malignant transformation, just visualization is not enough. Therefore, our lab combines imaging approaches with lineage tracing techniques to obtain quantitative information on cellular behavior, as well as more detailed molecular analysis to further understand the molecular networks involved in (pre-)malignant transformation. In addition, we also developed and use patient-derived xenograft models (Hutten et al., Cancer Cell, 2023; Hutten et al., STAR protocols, 2023) and complex organoid models (Caruso et al., Frontiers in Physiology, 2022; Caruso et al., Methods Molecular Biology, 2024).
Remodeling of a branched mammary organoid.
Whole-mount image of a patient-derived xenograft model of ductal carcinoma in situ (green) growing within the mouse mammary ducts (magenta and white). These cells form a potential precursor of breast cancer.
Menstrual cycle influences spread of mutant cells in mammary tissue
Using these techniques, we previously studied branching morphogenesis in the mammary gland (Scheele et al., Nature 2017; Hannezo et al., Cell, 2017). We uncovered the location and number of the stem cells that drive mammary gland development and were able to visualize stem cell behavior and dynamics for the first time in vivo. After understanding the basic principles of branching morphogenesis in the mammary gland, we took it a step further to understand the dynamics of failure of these organs due to genetic defects, tissue damage, or mutation accumulation and subsequent tumor formation. Using a model of Brca1;P53-driven tumorigenesis, we discovered three layers of protection in the mammary gland against tumorigenesis (Ciwinska et al., Nature, 2024). Interestingly, we found that tissue remodeling driven by the estrous cycle (equivalent of menstrual cycle in humans) plays a key role in preventing tumorigenesis. Although this remodeling is very effective at cleaning out mutant cells, it is not flawless. We discovered that some mutant cells, by chance, survive. Strikingly, the same tissue remodeling process now allows these mutant cells to proliferate and spread within the normal tissue leading to large fields of mutant cells within the healthy ductal structures of the mammary gland. This field clonalization predisposes to tumor formation in both mouse and human breast tissue (Ciwinska et al., Nature, 2024; Hutten et al., The Journal of Pathology, 2024). Thus, the natural tissue remodeling in the breast appears to be a double-edged sword: on the one hand it leads to the natural removal of excess (both normal and mutant) cells, on the other hand it facilitates the expansion of a few mutant cells within the healthy tissue.
Fields with mutant cells (in cyan, green and red) colonizing the mammary ducts (white).
Technology
Intravital microscopy
3D whole organ imaging
Genetically Engineered Mouse Models
Patient-Derived Tumor Xenografts
Lineage tracing