  Citation: Liliac, I.M.; Ungureanu, B.S.; M ˘ arg˘ aritescu, C.; Sacerdot , ianu, V.M.; S˘ aftoiu, A.; Mogoant ˘ a, L.; Moraru, E.; Pirici, D. E-Cadherin Modulation and Inter-Cellular Trafficking in Tubular Gastric Adenocarcinoma: A High-Resolution Microscopy Pilot Study. Biomedicines 2022, 10, 349. https://doi.org/ 10.3390/biomedicines10020349 Academic Editor: Dakeun Lee Received: 13 January 2022 Accepted: 30 January 2022 Published: 1 February 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). biomedicines Article E-Cadherin Modulation and Inter-Cellular Trafficking in Tubular Gastric Adenocarcinoma: A High-Resolution Microscopy Pilot Study Ilona Mihaela Liliac 1,† , Bogdan Silviu Ungureanu 2,† , Claudiu Mărgăritescu 3, *, Victor Mihai Sacerdot , ianu 2 , Adrian Săftoiu 4 , Laurent , iu Mogoantă 5 , Emil Moraru 6 and Daniel Pirici 5, * 1 PhD Student, Doctoral School, Department of Histology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania; ilona.mihaela.liliac@gmail.com 2 Department of Gastroenterology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania; bogdan.ungureanu@umfcv.ro (B.S.U.); sacerdotianumihai@gmail.com (V.M.S.) 3 Department of Pathology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania 4 Department of Research Methodology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania; adrian.saftoiu@umfcv.ro 5 Department of Histology, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania; laurentiu.mogoanta@umfcv.ro 6 Department of Surgery, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania; emil.moraru@umfcv.ro * Correspondence: claudiu.margaritescu@umfcv.ro (C.M.); daniel.pirici@umfcv.ro (D.P.) † I.M.L. and B.S.U. had equal contributions and share the first authorship. Abstract: Despite the numerous advances in tumor molecular biology and chemotherapy options, gastric adenocarcinoma is still the most frequent form of gastric cancer. One of the core proteins that regulates inter-cellular adhesion, E-cadherin plays important roles in tumorigenesis as well as in tumor progression; however, the exact expression changes and modulation that occur in gastric cancer are not yet fully understood. In an attempt to estimate if the synthesis/degradation balance matches the final membrane expression of this adhesion molecule in cancer tissue, we assessed the proportion of E-cadherin that is found in the Golgi vesicles as well as in the lysosomal pathway We utilized archived tissue fragments from 18 patients with well and poorly differentiated intestinal types of gastric cancer and 5 samples of normal gastric mucosa, by using high-magnification multispectral microscopy and high-resolution fluorescence deconvolution microscopy. Our data showed that E-cadherin is not only expressed in the membrane, but also in the cytoplasm of normal and tumor gastric epithelia. E-cadherin colocalization with the Golgian vesicles seemed to be increasing with less differentiated tumors, while co-localization with the lysosomal system decreased in tumor tissue; however, the membrane expression of the adhesion molecule clearly dropped from well to poorly differentiated tumors. Thus E-cadherin seems to be more abundantly synthetized than eliminated via lysosomes/exosomes in less differentiated tumors, suggesting that post-translational modifications, such as cleavage, conformational inactivation, or exocytosis, are responsible for the net drop of E-cadherin at the level of the membrane in more anaplastic tumors. This behavior is in perfect accor- dance with the concept of partial epithelial-to-mesenchymal transition (P-EMT), when the E-cadherin expression of tumor cells is in fact not downregulated but redistributed away from the membrane in recycling vesicles. Moreover, our high-resolution deconvolution microscopy study showed for the first time, at the tissue level, the presence of Lysosome-associated membrane glycoprotein 1 (LAMP1)-positive exosomes/multivesicular bodies being trafficked across the membranes of tumor epithelial cells. Altogether, a myriad of putative modulatory pathways is available as a treatment turning point, even if we are to only consider the metabolism of membrane E-cadherin regulation. Future super-resolution microscopy studies are needed to clarify the extent of lysosome/exosome exchange between tumor cells and with the surrounding stroma, in histopathology samples or even in vivo. Biomedicines 2022, 10, 349. https://doi.org/10.3390/biomedicines10020349 https://www.mdpi.com/journal/biomedicines