RESEARCH SNAPSHOT published: 05 April 2019 doi: 10.3389/fphar.2019.00342 Frontiers in Pharmacology | www.frontiersin.org 1 April 2019 | Volume 10 | Article 342 Edited by: Chiranjib Chakraborty, Galgotias University, India Reviewed by: Raghvendra Mohan Srivastava, Memorial Sloan Kettering Cancer Center, United States Emerson Soares Bernardes, Instituto de Pesquisas Energéticas e Nucleares (CNEN), Brazil *Correspondence: Elizaveta Fasler-Kan elizaveta.fasler@insel.ch Vadim V. Sumbayev V.Sumbayev@kent.ac.uk Specialty section: This article was submitted to Experimental Pharmacology and Drug Discovery, a section of the journal Frontiers in Pharmacology Received: 15 December 2018 Accepted: 19 March 2019 Published: 05 April 2019 Citation: Sakhnevych SS, Yasinska IM, Fasler-Kan E and Sumbayev VV (2019) Mitochondrial Defunctionalization Supresses Tim-3-Galectin-9 Secretory Pathway in Human Colorectal Cancer Cells and Thus Can Possibly Affect Tumor Immune Escape. Front. Pharmacol. 10:342. doi: 10.3389/fphar.2019.00342 Mitochondrial Defunctionalization Supresses Tim-3-Galectin-9 Secretory Pathway in Human Colorectal Cancer Cells and Thus Can Possibly Affect Tumor Immune Escape Svetlana S. Sakhnevych 1 , Inna M. Yasinska 1 , Elizaveta Fasler-Kan 2,3 * and Vadim V. Sumbayev 1 * 1 Medway School of Pharmacy, Universities of Kent and Greenwich, Chatham, United Kingdom, 2 Department of Pediatric Surgery and Department of Biomedical Research, Children’s Hospital, Inselspital, University of Bern, Bern, Switzerland, 3 Department of Biomedicine, University Hospital Basel and University of Basel, Basel, Switzerland The Tim-3-galectin-9 secretory pathway is known to protect various types of cancer cells against host immune surveillance. We found that pharmacologically induced mitochondrial dysfunction leads to a reduced galectin-9 expression/exocytosis in human colorectal cancer cells and re-distribution of this protein (the effect described for various cellular proteins) into mitochondria. Keywords: galectin-9, Tim-3, immune surveillance, mitochondria, colorectal cancer RESULTS It has recently been discovered that the immune receptor Tim-3 (T cell immunoglobulin and mucin domain-containing protein 3) and it’s ligand galectin-9 determines the capability of various types of malignant cells [e.g., acute myeloid leukemia (AML), colorectal cancer] to escape host immune surveillance (Kang et al., 2015; Gonçalves Silva et al., 2017; Sakhnevych et al., 2018; Yasinska et al., 2018b). Also, some of the galectin family members (for example galectin-3) were found to be able to protect AML and colorectal cancer cells against apoptosis through mitochondrial stabilization in a B cell lymphoma protein (Bcl) 2-dependent manner (Lee et al., 2013; Ruvolo, 2016). We asked whether galectin-9 has the same intracellular anti-apoptotic activity in addition to its extracellular immunosuppressive role. We used a pharmacological inhibitor 5-[(4-bromophenyl)methylene]- a-(1-methylethyl)-4-oxo-2-thioxo-3-thiazolidineacetic acid (BH3I-1, Figure 1A), a synthetic cell permeable Bcl-X L antagonist, which induces apoptosis via inhibition of interactions between the BH3 domain and Bcl-X L thus defunctionalyzing mitochondria. We found that BH3I-1 was capable of inducing apoptosis in Colo 205 colorectal adenocarcinoma cells of epithelial origin (based on increased caspase-3 activity and decreased viability of the cells, Figure 1A). Silencing either galectin-9 or its receptor and possible trafficker Tim-3 did not affect the pro-apoptotic activity of BH3I-1 suggesting that galectin-9 is unlikely to display anti-apoptotic activity in this case. Interestingly, the action of BH3I-1 did not affect the activity of mammalian target of rapamycin (mTOR) translational pathway as seen from its capability to phosphorylate eukaryotic initiation