Abstract LB243: Implantable and insertable miniature dual-axis confocal (DAC) microscope to detect epithelial-mesenchymal transition (EMT) in the breast cancer microenvironment

The tumor microenvironment (TME) can be defined as non-transformed stromal elements within the tumor, effecting their growth, invasion, and metastatic ability. Cancer cells leave the primary tumor during metastasis, then spread and colonize in distant organs. In breast cancer, metastasis mechanisms are not yet fully understood within the TME. However, epithelial to mesenchymal transition (EMT) is a known essential step in metastasis, in which patterned epithelial cells transform into migratory cells with mesenchymal phenotypes. Developing state-of-the-art multiparametric in vivo imaging devices increases the opportunities to observe dynamic cellular properties and their interactions with the surrounding stroma and TME during the critical steps of invasion and metastasis. Currently available commercial imaging technologies only enable in vivo imaging under anesthesia in a fixed posture. In contrast, real-time confocal imaging of the EMT and TME is not possible in animals. We have adapted our miniature dual-axis confocal (DAC) fluorescent microscope to track breast cancer cells having fluorescent reporters indicating key molecular splicing events during EMT to overcome these limitations. This project aims to study EMT more thoroughly using rat breast cancer MTLn3 cell lines by mimicking in vivo scenarios through 3D in vitro mono/co-culture spheroids, 3D multi-spheroid matrix overlay models, and 3D sandwich. We have engineered MTLn3 cells with fluorescent reporters correlating with different EMT stages, depending on their invasiveness levels. The ultra-low attachment method is used to engineer 3D MTLn3 spheroids, embed within TME matrices, and monitor advanced in vitro live-cell imaging techniques for up to 10 days. Another goal is to use miniature DAC microscopes, implanted in animal models, to study the fundamental changes occurring during carcinoma progression. This transdisciplinary project9s final goal is to optimize the DAC microscope as an implantable and insertable device to investigate EMT-associated splicing events in the TME of orthotopic rat breast carcinoma models. This will be achieved by growing engineered MTLn3 cells and spheroids in their mammary fat pads and following microscopic changes for a certain period. This work will contribute to further developing the miniature implantable DAC microscopes for 3D high resolution, multiparametric imaging to reveal dynamic changes within the TME during carcinoma progression. Citation Format: Ehsanul Hoque Apu, Seock-Jin Chung, Michael J. Mandella, Frank Schonig, Frank B. Gertler, Zhen Qiu, Christopher H. Contag. Implantable and insertable miniature dual-axis confocal (DAC) microscope to detect epithelial-mesenchymal transition (EMT) in the breast cancer microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB243.