Horizontal transfer of macrophage mitochondria (green) to breast cancer cells (purple)
Ferritin (yellow) localization at transferred mitochondria (magenta) in cancer cells.
In vivo zebrafish melanoma cells expressing actin binding protein, ena/vasp-m neon green
PaxillinB (green) and actin (Lifeact, magenta) localization in Dictyostelium discoideum.
Chimeric antigen receptor-expressing macrophage (magenta) phagocytosing melanoma cell (green).
3D Rendering of macrophages (red) contacting tumor cells (green) in the zebrafish skin
Tumor cells embedded in the zebrafish skin
Tumor cells (green) invading through the endothelium (red) in vitro
GFP expression in the zebrafish skin
Research
Overview
Metastases are the main cause of human cancer deaths. As cancer progresses, cancer cells migrate from the initial tumor mass and spread to vital organs. The microenvironment surrounding the tumor is complex, and we are becoming increasingly aware that the microenvironment contains signals that regulate cancer cell behavior. We seek to understand what these signals are, which cells send them, and how this communication regulates cancer decision-making in complex environments. While these questions are deeply rooted within a cancer context, our projects also address fundamental aspects of cellular behavior.
Projects in the Lab
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Lateral transfer of macrophage mitochondria to cancer
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Macrophage-dependent iron homeostasis in cancer
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Regulation of cell-matrix interactions in vivo
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Evolutionary origin, composition and function of cell-substrate adhesions
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Development of chimeric antigen receptor macrophages (CAR-Ms) to target melanoma in vivo
Lateral transfer of macrophage mitochondria in cancer
(Joey Casalini and Danny Bae)
Macrophages are a component of our immune system, but have a paradoxical role in cancer – Macrophages can promote metastasis. We previously discovered that macrophages spill their internal contents into cancer cells during metastasis, but what is the functionally important information in the contents? We recently discovered that macrophages transfer an organelle called mitochondria directly to cancer cells, and that receipt of macrophage mitochondria allow cancer cells to grow more rapidly. Thus, we seek to answer how this mitochondrial transfer process occurs and what happens when the mitochondria are received by cancer cells in an effort to develop strategies to prevent this process. Surprisingly, we find that after mitochondrial transfer occurs, the transferred mitochondria remain as a spatially distinct population from the host mitochondrial network. Furthermore, we found that high levels of local reactive oxygen species accumulate at transferred mitochondria, suggesting an intriguing hypothesis that transferred mitochondria may provide a signal to tumor cells, rather than providing excess mitochondrial function as has been previously described. We are currently testing this hypothesis, along with the role and regulation of macrophages during mitochondrial transfer in breast cancer.
Macrophage-dependent iron homeostasis in cancer
(Daniel Greiner and Sophia Varady)
In addition to their role in cancer, macrophages perform essential functions in the maintenance of both systemic and cellular iron homeostasis. Iron is critical as a cofactor for many enzymatic functions because it readily transfers electrons. As such, it is utilized by a wide variety of proteins for many cellular processes including DNA replication and oxidative phosphorylation. To acquire sufficient iron for unrestrained growth, many types of cancer exhibit dysregulation in iron homeostasis, with increased iron import and reduced export. Thus, we seek to understand how macrophage-tumor interactions within the tumor microenvironment disrupt the import, export and availability of iron in breast cancer cells, increasing the metastatic potential of the tumor. To answer these questions, we take advantage of human breast cancer cell lines and mouse models of mammary adenocarcinoma.
Regulation of cell-matrix interactions in vivo
(Qian Xue)
It is unclear how a melanocyte transitions from a premalignant nevus to an invasive melanoma cell; even less studied is the direct examination of this transition to motility in vivo. On 2-dimensional substrates, cancer cells migrate through a net forward movement of cell protrusion at the front and cell retraction at the back. Central to this form of cancer cell migration is cell attachment to the underlying substrate through focal adhesion complexes. Despite years of research on focal adhesion formation, the function and organization of these structures in their native environment are still unclear. What is the composition and dynamic regulation of focal adhesion structures in vivo? How do surrounding cells and extracellular matrix composition affect focal adhesion assembly and function in cancer cells? Inhibitors targeting focal adhesion components are currently being explored in the clinic, thus it is critical to understand how these complexes function in cancer cell migration in animals. We have developed an innovative system in zebrafish larvae in which we can directly visualize the formation of focal adhesion structures in highly migratory melanoma cells on a relatively planar surface of the larval zebrafish skin. We have used this system to dissect the composition and dynamics of focal adhesion structures in vivo and have identified unique properties of focal adhesion formation and regulation in cancer cells in their native environments.
Evolutionary origin, composition, and function of cell-substrate adhesions
(Julio Fierro)
Focal adhesion machinery was initially thought to be animal (metazoan)-specific, however comparative genomics of organisms evolutionary distant from Metazoa suggest full-length homologues of core components are found in organisms as distant as Amoebozoa. Interestingly, many organisms evolutionarily distant from Metazoans form cell-substrate adhesions for migration despite lacking the complete focal adhesion machinery found in Metazoans. We hypothesize species evolutionarily distant from Metazoans form cell-substrate adhesions using focal adhesion molecule orthologues that maintain conserved adhesive functions and interactions. We will use evolutionary analyses, biochemistry, and cell biology to elucidate the composition and function of evolutionary distant cell-substrate adhesions and characterize adhesion orthologues in the Amoebozoan, Dictyostelium discoideum.
Development of chimeric antigen receptor macrophages (CAR-Ms) to target melanoma in vivo
(Trinity Waddell)
The growing list of tumor-promoting macrophage functions includes increasing proliferation, increasing angiogenesis, facilitating immune escape, and strengthening metastatic potential. The recent development of chimeric antigen receptor macrophages, CAR-Ms (modeled off of the successful CAR-T cell therapy), to restore a proper anti-tumor macrophage phenotype has opened doors to new therapeutic cancer interventions. The premise behind this work is that macrophages can readily infiltrate solid tumors. Therefore, if a macrophage can be “taught” to phagocytose a specific cancer and is then introduced to the cancer environment, powerful therapeutics could be designed. We have generated CAR-Ms in vitro and have shown effective melanoma cell killing. We now seek to understand the regulation and function of these CAR-Ms in vivo, as well as test whether CAR-Ms can communicate to endogenous macrophage to elicit a robust anti-tumor response. We use a combination of cell culture, zebrafish and mouse melanoma models to visualize the dynamics of these processes in vitro and in vivo.