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Preclinical micro-endoscopy in tumors: targeting metastatic intravasation and resistance

Final Report Summary - DEEPINSIGHT (Preclinical micro-endoscopy in tumors: targeting metastatic intravasation and resistance)

Poor prognosis of cancer results from two central progression events, (i) the intravasation of cancer cells into blood vessels which leads to metastasis to distant organs and ultimately lethal tumor overload and (ii) cancer cell survival and adaptation to metabolic stress which causes resistance to anti-cancer therapy and limits life expectancy. Recently, intravital microscopy near the tumor surface has revealed unexpected connections between cancer cell invasion and survival signaling, and ways to inhibit both processes by new combination therapy. Besides the tumor surface, the tumor center may represent an important additional reservoir for intravasation and survival due to its large “inner surface” in combination with a nutrient- and oxygen-deficient environment. However, the tumor center cannot be reached by in vivo microscopy due to detrimental light scattering, which precludes direct observation of both processes at live-cell level.
We here develop a novel multiphoton endomicroscope device in collaboration with project partners GRINTECH, Jena, Germany and LaVision BioTec, Bielefeld, Germany. For this project, GRINTECH has developed optical devices which enable light propagation and lateral side view of near-infrared and infrared laser light. LaVision BioTech provided system mechanical and computational integration of the endomicroscope into the existing multiphoton microscopy platform for preclinical applications. The device is suited to overcome tissue penetration limits of microscopy and monitor important progression events deeply inside tumors. The instrument enables direct in vivo visualization of cell functions in living tumors up to several millimeters below the tumor surface.
We developed the hard- and software of the endomicroscope, optimized the automated position control and panoramic rotation to sample large tissue volumes and validated in tissue phantoms and live tumors in mice for application stability and safety. From a range of prototypes, two instrument designs were finalized with 2 mm and 500 μm outer diameter with >2 and 11.5 mm length, respectively. Using different shielding and coating strategies, the stability of the instrument was greatly improved and compatibility with tissue was optimized. In addition, strategies to minimize tissue trauma by direct insertion of the endoscope into tissue were developed and proof of concept for the applicability in established vascularized tumors was successfully tested. The strategies included 3D microscopy of live fluorescent multi-color tumors expressing molecular reporters together with molecular profiling and histopathology, to record cancer cell migration, proliferation and death in the context with embedding tissue structures.
We identified tumor cell dynamics and interaction with the tumor vasculature. In addition, models and technology to isolate circulating tumor cells and tumor models of enhanced metastasis were developed and will be used for testing both safety and applicability of intratumor endomicroscopy to elucidate key steps of metastatic cancer progression. Besides pioneering preclinical microendoscopy and illuminating thus far hidden mechanisms of cancer progression in the tumor core, this technology may give impulses for applications of endomicroscopy in other tissue types and disease models as well as endoscopic disease monitoring in patients (“optical biopsy”).