Mitochondrial fusion limits breast cancer metastasis
Ontology highlight
ABSTRACT: Mitochondrial metabolism plays a central role in promoting cancer growth and metastatic progression. The transition between a hyperfused and fragmented mitochondrial network is termed mitochondrial dynamics and is important for many mitochondria-associated functions; however, little is known regarding how this process influences metastasis. Here, we show that breast cancer cells with low metastatic potential exhibit a more fused mitochondrial network compared to highly metastatic breast cancer cells. To examine whether a fused mitochondrial network could impair metastasis, we inhibited mitochondrial fission in metastatic breast cancer cells by individual genetic deletion of three key regulators of mitochondrial fission (Drp1, Fis1 and Mff) or pharmacological intervention using leflunomide, an anti-rheumatic drug. These cells displayed a fused mitochondrial network and limited survival under anoikis conditions, consistent with mitochondrial fusion limiting metastasis. Transcriptomics and metabolomics analyses revealed that mitochondrial fusion causes significant alterations in metabolic pathways and processes related to cell adhesion. Functional bioenergetics assays demonstrated that mitochondrial fusion limited the mitochondrial capacity of cancer cells. Mitochondrial fusion in breast cancer cells had no significant effect on primary tumor growth but almost completely ablated lung metastasis in vivo. Furthermore, the transcriptomics signature associated with enhanced mitochondrial fusion correlated with improved survival in patients with breast cancer. Overall, our findings highlight mitochondrial fusion as a therapeutic opportunity for breast cancer.
Project description:Metastatic cancer cells, originating from cancer stem cells with metastatic capacity, utilize nutrient flexibility to overcome the hurdles of metastatic cascade. However, the nutrient supply for maintaining the stemness potentials of metastatic cancer cells remains unknown. Here, we revealed that metastatic breast cancer cells maintain stemness and initiate metastasis upon detachment via uptaking and oxidating lactate. In detached metastasizing breast cancer cells, lactate was incorporated into tricarboxylic acid cycle and boosted oxidative phosphorylation, and then promoted the stemness potentials via α-KG-DNMT3B-mediated SOX2 hypomethylation. Moreover, lactate was uptake and oxidated in mitochondria by CD147/MCT1/LDHB complex, whose existence correlates to the stemness potentials and tumor metastasis in breast cancer patients. An intracellularly expressed single chain variable fragment targeting mitochondrial CD147 (mito-CD147 scFv) effectively disrupted mitochondrial CD147/MCT1/LDHB complex, inhibited lactate-induced stemness potentials, depleted circulating breast cancer cells and reduced metastatic burden, suggesting a promising clinical application in reducing lactate-fueled metastasis.
Project description:G1P3 (IFI6) was associated with poor distance metastasis free survival (DMFS) in breast cancer cases. Therefore, we tested the hypothesis that G1P3-induced mitochondrial redox deregulation confers metastatic potentials in breast cancer cells. Our results demonstrate that coordinated action of multiple pathways elicited by G1P3-induced mtROS augment actin-containing migratory structures to promote breast cancer cell migration and invasion Comparative network analysis identified upregulation of antioxidant, acin remodeling, and EMT networks in G1P3 overexpressing MCF-7 cells.
Project description:Spontaneous cell fusion of MDA-MB-231 bone-metastatic subline Bm (i.e., SCP2) and lung metastatic subline Lm (i.e., LM2) gave rise to hybrid lines BLm-FACS or BLm-DRUG, as well as its single clones (#8, #12, #18). The hybrids acquired the metastasis tropisms from both parental cells. Expression profiles of the parental cells, the hybrids and several previously characterized MDA-MB-231 metastatic derivatives were compared. Hierarchical clustering showed the hybrids assimilated the organ-specific metastasis gene signatures from both parental cells. Experiment Overall Design: Twenty-six cell lines were analyzed, including the parental line MDA-MB-231; cell fusion partner lines Bm and Lm; self-fused lines BBm and LLm; hetero-fused lines BLm-FACS, BLM-DRUG and clones BLm-DRUG-8, -12 and -18; strongly bone-metastatic lines 1833, SCP14, SCP20, SCP25 and SCP46; strongly lung-metastatic lines 3481, 4142, 4173, 4175 and 4180; and weakly metastatic lines SCP3, SCP4, SCP6, SCP28, SCP32 and SCP43. Single sample for each line.
Project description:<p>Breast cancer metastasis occurs via blood and lymphatic vessels. Breast cancer cells 'educate' lymphatic endothelial cells (LECs) to support tumor vascularization and growth. However, despite known metabolic alterations in breast cancer, it remains unclear how lymphatic endothelial cell metabolism is altered in the tumor microenvironment and its effect in lymphangiogenic signaling in LECs. We analyzed metabolites inside LECs in co-culture with MCF-7, MDA-MB-231, and SK-BR-3 breast cancer cell lines using 1H nuclear magnetic resonance (NMR) metabolomics, Seahorse, and the spatial distribution of metabolic co-enzymes using optical redox ratio imaging to describe breast cancer-LEC metabolic crosstalk. LECs co-cultured with breast cancer cells exhibited cell-line dependent altered metabolic profiles, including significant changes in lactate concentration in breast cancer co-culture. Cell metabolic phenotype analysis using Seahorse showed LECs in co-culture exhibited reduced mitochondrial respiration, increased reliance on glycolysis and reduced metabolic flexibility. Optical redox ratio measurements revealed reduced NAD(P)H levels in LECs potentially due to increased NAD(P)H utilization to maintain redox homeostasis. 13C-labeled glucose experiments did not reveal lactate shuttling into LECs from breast cancer cells, yet showed other 13C signals in LECs suggesting internalized metabolites and metabolic exchange between the two cell types. We also determined that breast cancer co-culture stimulated lymphangiogenic signaling in LECs, yet activation was not stimulated by lactate alone. Increased lymphangiogenic signaling suggests paracrine signaling between LECs and breast cancer cells which could have a pro-metastatic role.</p>
Project description:Metastatic breast cancer cells disseminate to organs with a soft microenvironment. Whether and how tissue mechanical properties influence their response to treatment remains unclear. Here we found that a soft ECM empowers redox homeostasis. Cells cultured on a soft ECM display increased peri-mitochondrial F-actin promoted by Spire1C and Arp2/3 nucleation factors, and increased DRP1- and MIEF1/2-dependent mitochondrial fission. Changes in mitochondrial dynamics lead to increased mtROS production and activate the NRF2 antioxidant transcriptional response, including increased cystine uptake and glutathione metabolism. This retrograde response endows cells with resistance to oxidative stress and ROS-dependent chemotherapy drugs. This is relevant in a mouse model of metastatic breast cancer cells dormant in the lung soft tissue, where inhibition of DRP1 and NRF2 restored cisplatin sensitivity and prevented disseminated cancer cell awakening. We propose that targeting this mitochondrial dynamics- and redox-based mechanotransduction pathway could open new avenues to prevent metastatic relapse.
Project description:Abstract:
Accumulating experimental and clinical evidence suggest that the immune response to cancer is not exclusively anti-tumor. Indeed, the pro-tumor roles of the immune system - as suppliers of growth and pro-angiogenic factors or defenses against cytotoxic immune attacks, for example - have been long appreciated, but relatively few theoretical works have considered their effects. Inspired by the recently proposed "immune-mediated" theory of metastasis, we develop a mathematical model for tumor-immune interactions at two anatomically distant sites, which includes both anti- and pro-tumor immune effects, and the experimentally observed tumor-induced phenotypic plasticity of immune cells (tumor "education" of the immune cells). Upon confrontation of our model to experimental data, we use it to evaluate the implications of the immune-mediated theory of metastasis. We find that tumor education of immune cells may explain the relatively poor performance of immunotherapies, and that many metastatic phenomena, including metastatic blow-up, dormancy, and metastasis to sites of injury, can be explained by the immune-mediated theory of metastasis. Our results suggest that further work is warranted to fully elucidate the pro-tumor effects of the immune system in metastatic cancer.
Project description:Tumor metastasis is responsible for the high mortality rate of patients with oral squamous cell carcinoma (OSCC). Although many hypotheses have been proposed to elucidate the mechanism of tumor metastasis, the origin of the metastatic tumor cells remains unclear. In this study, we explored the role of cell fusion in the formation of OSCC metastatic tumor cells. Murine OSCC tumor cells and macrophages were fused in vitro, and the cell proliferation, migration, and phagocytosis abilities of hybrid cells and parental cells were compared. Subsequently, we compared the transcriptome differences between hybrid and parental cells. Finally, we observed an association between the hybrid cells and the prognosis of patients with OSCC. Murine OSCC tumor cells and macrophages were successfully fused in vitro. The cytological and molecular experimental results revealed that OSCC tumor cells obtained a migration-related phenotype after fusion with macrophages, and the migration ability of hybrid cells was related to the activation of the “chemokine signal pathway”. Moreover, we proved that the existence of hybrid cells in OSCC tumor tissues is closely related to lymph node metastasis and poor prognosis. After fusion with macrophages, the chemokine signaling pathway in OSCC tumor cells was activated, leading to metastasis.
Project description:High Arid4b promotes mammary tumor growth and metastasis in mouse model systems, and is associated with poor metastasis-free survival in human breast cancer patients. Through shRNA-mediated knockdown, we demonstrated that loss of Arid4b significantly inhibits the ability of mouse breast cancer cells to metastasize to the lungs. We performed microarray expression and subsequent network analysis to identify genes diferentially regulated as a consequence of Arid4b knockdown. The highly metastatic mouse breast cancer cell line 6DT1 was transduced with lentiviral shRNAs targeting Arid4b (RMM4534-NM_194262, Open Biosystems) or scrambled control in the same pLKO.1 vector backbone. Stably transduced cells were selected with puromycin, then total RNA was isolated from pooled clones.
Project description:Introduction: The prognosis for patients with breast tumor metastases to brain is extremely poor. Identification of prognostic molecular markers of the metastatic process is critical for designing therapeutic modalities for reducing the occurrence of metastasis. Although ubiquitously present in most human organs, calcium-activated potassium (BK) channel is significantly upregulated in breast cancer cells. In this study we investigated the role of KCNMA1 gene, which encodes α subunit of KCa channels (BK channels) in breast cancer metastasis and invasion. Methods: We performed Global exon array to study the expression of KCNMA1 in metastatic breast cancer in brain, compared its expression in primary breast cancer and breast cancers metastatic to other organs, and validated the findings by RT-PCR. Immunohistochemistry was performed to study the expression and localization of α subunit of KCa channel protein in primary and metastatic breast cancer tissues and breast cancer cell lines. We performed matrigel invasion, transendothelial migration and membrane potential assays in established lines of normal breast cells (MCF-10A), non-metastatic breast cancer (MCF-7), non-brain metastatic breast cancer cells (MDA-MB-231), and brain-specific metastatic breast cancer cells (MDA-MB-361) to study whether KCa channel inhibition attenuates breast tumor invasion and metastasis using KCNMA1 knockdown with siRNA and biochemical inhibition with IBTX (Iberiotoxin). Results: The Global exon array and RT-PCR showed higher KCNMA1 expression in metastatic breast cancer in brain compared to metastatic breast cancers in other organs. Our results clearly show that metastatic breast cancer cells exhibit increased BK channel activity, leading to greater invasiveness and transendothelial migration, both of which could be attenuated by blocking KCNMA1. Conclusion: Determining the relative abundance of BK channel over expression in breast cancer metastatic to brain and the mechanism of its action in brain metastasis will provide a unique opportunity to identify and differentiate between low grade breast tumors that are at high risk for metastasis from those at low risk for metastasis. This distinction would in turn allow for the appropriate and efficient application of effective treatments while sparing patients with low risk for metastasis from the toxic side effects of chemotherapy.