Novel mechanisms of endothelial-epithelial interactions underlying cancer metastasis

Thesis (Ph. D. in Medical Engineering and Medical Physics)--Harvard-MIT Program in Health Sciences and Technology, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 356-386).Elucidation of molecular mechanisms underlying metastasis is the final frontier in cancer biology research. Identifying individual pathways in the metastatic cascade could lead to development of metastasis-specific therapeutics; however, current in vivo metastasis model systems are not efficient tools for isolating a single molecular event from the network of complex biological pathways. In response to these needs, we have developed a 3D in vitro co-culture system that isolates molecular and physical interactions between metastatic cells and the endothelium, which are prerequisite for invasive spread. We have used this model to identify key mediators of epithelial-endothelial cell interactions, to screen metastasis specific therapeutics, and most significantly, to elucidate a novel form of intercellular communication through thin cytoskeletal projections called nanoChannels (nCs) that is involved in pathological angiogenesis and that may prime metastatic spread. Metastatic cells preferentially form nCs with the endothelium, enabling rapid and directed transfer of intracellular contents. Proteins, small cytoplasmic dyes, nanoparticles, and most interestingly, functional microRNAs (miRNAs) are transported through these structures. Communication of miRNAs through nCs presents a novel mechanism of pathological angiogenesis and the angiogenic switch. NanoChannel-mediated communication introduces a new paradigm of cancer progression in which tumor cells can directly transform surrounding cell populations in order to facilitate cancer pathogenesis.by Yamicia Doyasi Connor.Ph.D.in Medical Engineering and Medical Physic

Medulloblastoma Recurrence and Metastatic Spread Are Independent of Colony-Stimulating Factor 1 Receptor Signaling and Macrophage Survival

International audiencePURPOSE: Tumor infiltration by immunosuppressive myeloid cells or tumor-associated macrophages (TAMs) contributes to tumor progression and metastasis. In contrast to their adult counterparts, higher TAM signatures do not correlate with aggressive tumor behavior in pediatric brain tumors. While prominent TAM infiltrates exist before and after radiation, the degree to which irradiated macrophages and microglia support progression or leptomeningeal metastasis remains unclear. Patients with medulloblastoma often present with distant metastases and tumor recurrence is largely incurable, making them prime candidates for the study of novel approaches to prevent neuroaxis dissemination and recurrence. METHODS: Macrophage depletion was achieved using CSF-1 receptor inhibitors (CSF-1Ri), BLZ945 and AFS98, with or without whole brain radiation in a variety of medulloblastoma models, including patient-derived xenografts bearing Group 3 medulloblastoma and a transgenic Sonic Hedgehog (Ptch1+/-, Trp53-/-) medulloblastoma model. RESULTS: Effective reduction of microglia, TAM, and spinal cord macrophage with CSF-1Ri resulted in negligible effects on the rate of local and spinal recurrences or survival following radiation. Results were comparable between medulloblastoma subgroups. While notably few tumor-infiltrating lymphocytes (TILs) were detected, average numbers of CD3+ TILs and FoxP3+ Tregs did not differ between groups following treatment and tumor aggressiveness by Ki67 proliferation index was unaltered. CONCLUSION: In the absence of other microenvironmental influences, medulloblastoma-educated macrophages do not operate as tumor-supportive cells or promote leptomeningeal recurrence in these models. Our data add to a growing body of literature describing a distinct immunophenotype amid the medulloblastoma microenvironment and highlight the importance of appropriate pediatric modeling prior to clinical translation

Physical nanoscale conduit-mediated communication between tumour cells and the endothelium modulates endothelial phenotype

Metastasis is a major cause of mortality and remains a hurdle in the search for a cure for cancer. Not much is known about metastatic cancer cells and endothelial cross-talk, which occurs at multiple stages during metastasis. Here we report a dynamic regulation of the endothelium by cancer cells through the formation of nanoscale intercellular membrane bridges, which act as physical conduits for transfer of microRNAs. The communication between the tumour cell and the endothelium upregulates markers associated with pathological endothelium, which is reversed by pharmacological inhibition of these nanoscale conduits. These results lead us to define the notion of ‘metastatic hijack’: cancer cell-induced transformation of healthy endothelium into pathological endothelium via horizontal communication through the nanoscale conduits. Pharmacological perturbation of these nanoscale membrane bridges decreases metastatic foci in vivo. Targeting these nanoscale membrane bridges may potentially emerge as a new therapeutic opportunity in the management of metastatic cancer