The HDAC inhibitor HFY-4A improves TUSC2 transcription to induce immunogenic cell death in breast cancer.

We managed to explore the function of HFY-4A, a novel histone deacetylases (HDACs) inhibitor, on breast cancer as well as its potential mechanisms. MCF7 and T47D cells were treated with 0.8, 1.6 or 3.2 µM HFY-4A for 0-72 h, following of which CCK-8, colony formation, EdU staining, flow cytometry, Transwell, and wound healing assays were carried out. Western blot, immunohistochemistry, and ELISA were conducted for assaying the expression of immunogenic cell death (ICD)-related proteins. The interaction between HFY-4A, HDAC1, and tumor suppressor candidate 2 (TUSC2) was evaluated by chromatin immunoprecipitation assay. Further, the function of HFY-4A in breast cancer progression in vivo was evaluated using xenograft mouse models. HFY-4A inhibited the proliferation, migration, and invasion, and induced apoptosis of breast cancer cells in a dose-dependent manner. HFY-4A dose-dependently caused the ICD of breast cancer cells, as evidenced by the significant high levels of high-mobility group box 1 (HMGB1), calreticulin (CRT), heat shock protein 70 (HSP70), and HSP90. Interestingly, HFY-4A could facilitate TUSC2 transcription by promoting acetylation of histones on the TUSC2 promoter. The results of rescue assays revealed that HFY-4A repressed proliferation and mobility, but enhanced apoptosis and ICD through facilitating TUSC2 transcription in breast cancer. In breast cancer xenograft mouse models, HFY-4A was verified to inhibit tumor growth via upregulating TUSC2. HFY-4A could inhibit breast cancer cell proliferation and mobility, and enhanced apoptosis and ICD through facilitating TUSC2 transcription.

Pharmacological Modulation of Energy and Metabolic Pathways Protects Hearing in the Fus1/Tusc2 Knockout Model of Mitochondrial Dysfunction and Oxidative Stress.

Tightly regulated and robust mitochondrial activities are critical for normal hearing. Previously, we demonstrated that Fus1/Tusc2 KO mice with mitochondrial dysfunction exhibit premature hearing loss. Molecular analysis of the cochlea revealed hyperactivation of the mTOR pathway, oxidative stress, and altered mitochondrial morphology and quantity, suggesting compromised energy sensing and production. Here, we investigated whether the pharmacological modulation of metabolic pathways using rapamycin (RAPA) or 2-deoxy-D-glucose (2-DG) supplementation can protect against hearing loss in female Fus1 KO mice. Additionally, we aimed to identify mitochondria- and Fus1/Tusc2-dependent molecular pathways and processes critical for hearing. We found that inhibiting mTOR or activating alternative mitochondrial energetic pathways to glycolysis protected hearing in the mice. Comparative gene expression analysis revealed the dysregulation of critical biological processes in the KO cochlea, including mitochondrial metabolism, neural and immune responses, and the cochlear hypothalamic-pituitary-adrenal axis signaling system. RAPA and 2-DG mostly normalized these processes, although some genes showed a drug-specific response or no response at all. Interestingly, both drugs resulted in a pronounced upregulation of critical hearing-related genes not altered in the non-treated KO cochlea, including cytoskeletal and motor proteins and calcium-linked transporters and voltage-gated channels. These findings suggest that the pharmacological modulation of mitochondrial metabolism and bioenergetics may restore and activate processes critical for hearing, thereby protecting against hearing loss.

Tumor Suppressor Candidate 2 (TUSC2): Discovery, Functions, and Cancer Therapy.

Tumor Suppressor Candidate 2 (TUSC2) was first discovered as a potential tumor suppressor gene residing in the frequently deleted 3p21.3 chromosomal region. Since its discovery, TUSC2 has been found to play vital roles in normal immune function, and TUSC2 loss is associated with the development of autoimmune diseases as well as impaired responses within the innate immune system. TUSC2 also plays a vital role in regulating normal cellular mitochondrial calcium movement and homeostasis. Moreover, TUSC2 serves as an important factor in premature aging. In addition to TUSC2's normal cellular functions, TUSC2 has been studied as a tumor suppressor gene that is frequently deleted or lost in a multitude of cancers, including glioma, sarcoma, and cancers of the lung, breast, ovaries, and thyroid. TUSC2 is frequently lost in cancer due to somatic deletion within the 3p21.3 region, transcriptional inactivation via TUSC2 promoter methylation, post-transcriptional regulation via microRNAs, and post-translational regulation via polyubiquitination and proteasomal degradation. Additionally, restoration of TUSC2 expression promotes tumor suppression, eventuating in decreased cell proliferation, stemness, and tumor growth, as well as increased apoptosis. Consequently, TUSC2 gene therapy has been tested in patients with non-small cell lung cancer. This review will focus on the current understanding of TUSC2 functions in both normal and cancerous tissues, mechanisms of TUSC2 loss, TUSC2 cancer therapeutics, open questions, and future directions.

NEDD4 degrades TUSC2 to promote glioblastoma progression.

Whether tumor suppressor candidate 2 (TUSC2) plays an important role in glioblastoma (GBM) progression is largely unknown. Whether TUSC2 undergoes polyubiquitination is unknown. Herein, we report that TUSC2 protein expression is reduced/lost in GBM compared to normal brain due to protein destabilization; TUSC2 mRNA is equally expressed in both tissues. NEDD4 E3 ubiquitin ligase polyubiquitinates TUSC2 at residue K71, and the TUSC2-K71R mutant is resistant to NEDD4-mediated proteasomal degradation. Analysis of GBM specimens showed NEDD4 protein is highly expressed in GBM and the level is inversely correlated with TUSC2 protein levels. Furthermore, TUSC2 restoration induces apoptosis and inhibits patient-derived glioma stem cells (PD-GSCs) in vitro and in vivo. Conversely, TUSC2-knockout promotes PD-GSCs in vitro and in vivo. RNA-Seq analysis and subsequent validations showed GBM cells with TUSC2-knockout expressed increased Bcl-xL and were more resistant to apoptosis induced by a Bcl-xL-specific BH3 mimetic. A TUSC2-knockout gene signature created from the RNA-seq data predicts poor patient survival. Together, these findings establish that NEDD4-mediated polyubiquitination is a novel mechanism for TUSC2 degradation in GBM and that TUSC2 loss promotes GBM progression in part through Bcl-xL upregulation.

Circ-EGFR Functions as an Inhibitory Factor in the Malignant Progression of Glioma by Regulating the miR-183-5p/TUSC2 Axis.

Circular RNAs (circRNAs) have pivotal functions in regulating diverse biological processes of human tumors, including glioma. Herein, a novel circRNA epidermal growth factor receptor (circ-EGFR, hsa_circ_0080223) was researched in glioma. The molecular expression levels were analyzed via quantitative real-time polymerase chain reaction (qRT-PCR). Cell Counting Kit-8 (CCK-8) and colony formation assays were conducted to assess cell proliferation. Apoptosis was analyzed using flow cytometry. Cell migration and invasion were examined via transwell assay. Interaction relations between targets were verified using dual-luciferase reporter assay. Tumor Suppressor Candidate 2 (TUSC2) protein expression was examined by Western blot. In vivo experiment was performed by establishing xenograft model in mice. The qRT-PCR showed the downregulation of circ-EGFR and TUSC2 but the upregulation of microRNA-183-5p (miR-183-5p) in glioma samples. In vitro assays revealed that circ-EGFR overexpression induced the repression of cell proliferation, migration, and invasion but the promotion of apoptosis. Circ-EGFR was identified as a sponge of miR-183-5p and circ-EGFR-mediated glioma progression inhibition was abolished by miR-183-5p downregulation. Additionally, miR-183-5p targeted TUSC2 and miR-183-5p inhibitor impeded the development of glioma by upregulating the expression of TUSC2. Furthermore, circ-EGFR could regulate the TUSC2 level by sponging miR-183-5p. Glioma growth in vivo was also reduced by circ-EGFR via targeting the miR-183-5p/TUSC2 axis. Altogether, our results suggested that circ-EGFR inhibited the malignant progression of glioma by regulating the levels of miR-183-5p and TUSC2. Circ-EGFR may be a useful therapeutic target to antagonize the glioma progression.

LncRNA GAS5-AS1 inhibits glioma proliferation, migration, and invasion via miR-106b-5p/TUSC2 axis.

Glioma is one of the most common malignant tumors and shows a high metastasis rate and poor prognosis. Abnormal expression of long non-coding RNAs (lncRNAs) contributes to various human tumors including gliomas. This study aimed to investigate the regulatory role of the antisense RNA of growth arrest special 5 (GAS5-AS1), a novel lncRNA, in gliomas. Expression of GAS5-AS1 and microRNA-106b-5p (miR-106b-5p) in glioma tissues and cells was detected by quantitative reverse transcription PCR, northern blotting, or fluorescent in situ hybridization. Cell proliferation, migration, and invasion were analyzed by CCK-8 and Transwell assays. BALB/c nude mice were used to establish a glioma xenograft animal model by subcutaneous injection of U251 cells transfected with small interfering RNA targeting GAS5-AS1. A dual-luciferase reporter assay was conducted to confirm the targeting relationship between GAS5-AS1 and miR-106b-5p. GAS5-AS1 expression was downregulated in glioma tissues and cells, and upregulation of GAS5-AS1 expression inhibited glioma cell proliferation, migration, and invasion. GAS5-AS1 expression was correlated with the glioma tumor grade. In nude mice, upregulation of GAS5-AS1 markedly suppressed glioma tumor growth. GAS5-AS1 overexpression significantly increased the miR-106b-5p level in glioma cells, and GAS5-AS1 expression was negatively related to miR-106b-5p expression in glioma tissues. Overexpression of miR-106b-5p reversed the inhibitory effects of GAS5-AS1 upregulation on glioma cell proliferation and metastasis, while restoration of TUSC2 rescued the proliferation and invasion of glioma cells transfected with miR-106b-5p mimics. In summary, lncRNA GAS5-AS1 inhibited glioma proliferation, migration, and invasion by sponging miR-106b-5p and regulating the expression of TUSC2. Our results suggest GAS5-AS1 as a novel target for the treatment and prognosis prediction of gliomas.

The TUSC2 Tumour Suppressor Inhibits the Malignant Phenotype of Human Thyroid Cancer Cells via SMAC/DIABLO Protein.

Thyroid carcinoma is the most common endocrine cancer and includes different forms. Among these, anaplastic thyroid carcinoma (ATC) is the rarest but the most lethal subtype, compared to papillary thyroid carcinoma (PTC) which shows an overall good prognosis. We have previously showed that Tumor Suppressor Candidate 2 (TUSC2), a known tumour suppressor gene, is downregulated in human PTC and ATC compared to normal thyroid samples. The aim of this study was to gain insight into the molecular mechanisms induced by TUSC2 in thyroid cancer cells. Here, we stably transfected TUSC2 in papillary (TPC-1) and in anaplastic (8505C) thyroid cancer cell lines and studied its effects on several biological processes, demonstrating that TUSC2 overexpression decreased thyroid cancer cell proliferation, migration and invasion. Through the proteome profiler apoptosis array, we observed that TUSC2 increased sensitivity to apoptosis by increasing the SMAC/DIABLO and CYTOCHROME C proteins. On the other hand, transient silencing of TUSC2, by siRNA, in an immortalized thyroid follicular epithelial cell line (Nthy-ori 3-1) showed the opposite effect. Finally modulation of SMAC/DIABLO partially rescued the biological effects of TUSC2. Thus, our data highlight a tumour suppressor role of TUSC2 in thyroid carcinogenesis, suggesting that it could be a promising target and biomarker for thyroid carcinoma.

MicroRNA-663 facilitates the growth, migration and invasion of ovarian cancer cell by inhibiting TUSC2.

BACKGROUND: MicroRNAs (miRNAs) have emerged as the critical modulators of the tumorigenesis and tumor progression. METHODS: The levels of miR-663 in ovarian cancer cell lines and clinical tissues were detected using qRT-PCR assays. The Transwell invasion and wound healing assay were conducted to assess the roles of miR-663 in the migration and invasion of ovarian cancer cell in vitro. Rescue assays were carried out to confirm the contribution of tumor suppressor candidate 2 (TUSC2) in the aggressiveness of cancer cell which was regulated by miR-663. RESULTS: The levels of miR-663 were up-regulated in ovarian cancer tissues in comparison with the corresponding normal tissues. Up-regulation of miR-663 increased the proliferation, colony formation, migration and invasion of ovarian cancer SKOV3 cell. Additional, over-expression of miR-663 increased the tumor growth of SKOV3 in xenograft model. Bioinformatics analysis and luciferase reporter assay identified that miR-663 decreased the level of TUSC2 via binding to the 3'-UTR of TUSC2 gene. Finally, the expression of TUSC2 was inversely associated with the level of miR-663 in ovarian carcinoma tissue and over-expression of TUSC2 inhibited the migration and invasion abilities of SKOV3 that was promoted by miR-663. CONCLUSION: Altogether, these results indicate that miR-663 acts as a potential tumor-promoting miRNA through targeting TUSC2 in ovarian cancer.

MicroRNA-663 facilitates the growth, migration and invasion of ovarian cancer cell by inhibiting TUSC2

BACKGROUND: MicroRNAs (miRNAs) have emerged as the critical modulators of the tumorigenesis and tumor progression. METHODS: The levels of miR-663 in ovarian cancer cell lines and clinical tissues were detected using qRT-PCR assays. The Transwell invasion and wound healing assay were conducted to assess the roles of miR-663 in the migration and invasion of ovarian cancer cell in vitro. Rescue assays were carried out to confirm the contribution of tumor suppressor candidate 2 (TUSC2) in the aggressiveness of cancer cell which was regulated by miR-663. RESULTS: The levels of miR-663 were up-regulated in ovarian cancer tissues in comparison with the corresponding normal tissues. Up-regulation of miR-663 increased the proliferation, colony formation, migration and invasion of ovarian cancer SKOV3 cell. Additional, over-expression of miR-663 increased the tumor growth of SKOV3 in xenograft model. Bioinformatics analysis and luciferase reporter assay identified that miR-663 decreased the level of TUSC2 via binding to the 3'-UTR of TUSC2 gene. Finally, the expression of TUSC2 was inversely associated with the level of miR-663 in ovarian carcinoma tissue and over-expression of TUSC2 inhibited the migration and invasion abilities of SKOV3 that was promoted by miR-663. CONCLUSION: Altogether, these results indicate that miR-663 acts as a potential tumor-promoting miRNA through targeting TUSC2 in ovarian cancer.

TUSC2P suppresses the tumor function of esophageal squamous cell carcinoma by regulating TUSC2 expression and correlates with disease prognosis.

BACKGROUND: Pseudogenes are RNA transcripts with high homology with its parent protein-coding genes. Although pseudogenes lost the ability to produce protein, it still exert import biological function, and play important role in the pathogenesis of a wide varity of tumors; However, the role of pseudogenes in esophageal squamous cell carcinoma (ESCC) is poorly understood. METHODS: TUSC2P function in ESCC were explored using both in vitro and in vivo experiments cell proliferation, invasion and apoptosis assay was performed to evaluated the effect of TUSC2P on the tumor biology of ESCC. Expression of relative genes was assessed by quantitative real-time PCR (qRT-PCR) and western blotting in EC109 and TE-1 cell, as well as ESCC patients. 3'UTR luciferase assay was used to confirm the direct binding of miRNAs with TUSC2 and TUSC2P 3'UTR. Relation betweenTUSC2P, TUSC2 and ESCC prognosis was predicted by survival analysis (n = 56). RESULTS: Pseudogene TUSC2P was down regulated in ESCC tissues compared with paired normal adjacent tissues, and the expression of TUSC2P was significantly correlated with survivalof ESCC patients. Over expression of TUSC2P in EC109 and TE-1 cells resulted in altered expression of TUSC2, thus inhibited proliferation, invasion and promoted apoptosis. Dual luciferase assay demonstrated that TUSC2P 3'UTR decoyed miR-17-5p, miR-520a-3p, miR-608, miR-661 from binding to TUSC2. CONCLUSIONS: TUSC2P can suppresses the tumor function of esophageal squamous cell carcinoma by regulating TUSC2 expression and may also serve as a prognostic factor for ESCC patients.

miR-663b promotes tumor cell proliferation, migration and invasion in nasopharyngeal carcinoma through targeting TUSC2.

The authors' previous study revealed that the serum levels of microRNA (miR)-663b are significantly increased in patients with nasopharyngeal carcinoma (NPC), and are associated with NPC progression and poor prognosis. However, the molecular mechanism of underlying NPC growth and metastasis remains unclear. In the present study, quantitative polymerase chain reaction and western blot analyses were performed to examine changes to mRNA and protein expression, respectively. MTT, wound healing and Transwell assays were used to examine cell proliferation, migration and invasion, respectively. Luciferase reporter gene assays were performed to identify target genes of miR-663b. It was demonstrated that miR-663b was significantly upregulated in NPC tissue compared with non-tumor nasopharyngeal epithelial tissue samples. Furthermore, miR-663b expression gradually increased with advancing stages of NPC, with the highest expression being observed in the latest stage IV. The increased expression of miR-663b was associated with advanced clinical stage and lymph node metastasis. In addition, miR-663b expression was increased in NPC cell lines compared with normal nasopharyngeal epithelial NP69 cells. Knockdown of miR-663b resulted in a significant reduction in the proliferation, migration and invasion of NPC CNE1 cells. Tumor suppressor candidate 2 (TUSC2) was identified as a novel target gene of miR-663b. It was further demonstrated that TUSC2 was significantly downregulated in NPC tissue samples and cell lines. miR-663b negatively regulated the expression of TUSC2 at the post-transcriptional level in CNE1 cells. Additionally, inhibition of TUSC2 expression attenuated the suppressive effects of miR-663b downregulation on the proliferation, migration and invasion of CNE1 cells. To the best of our knowledge, this is the first study to demonstrate that miR-663b, which is upregulated in NPC, promotes the proliferation, migration and invasion of NPC cells, partially through the inhibition of TUSC2 expression. Therefore, it is suggested that miR-663b is a promising therapeutic target for the treatment of patients with NPC.

Mitochondrial protein Fus1/Tusc2 in premature aging and age-related pathologies: critical roles of calcium and energy homeostasis.

Decreased energy production and increased oxidative stress are considered to be major contributors to aging and aging-associated pathologies. The role of mitochondrial calcium homeostasis has also been highlighted as an important factor affecting different pathological conditions. Here, we present evidence that loss of a small mitochondrial protein Fus1 that maintains mitochondrial homeostasis results in premature aging, aging-associated pathologies, and decreased survival. We showed that Fus1KO mice develop multiple early aging signs including lordokyphosis, lack of vigor, inability to accumulate fat, reduced ability to tolerate stress, and premature death. Other prominent pathological changes included low sperm counts, compromised ability of adult stem cells to repopulate tissues, and chronic inflammation. At the molecular level, we demonstrated that mitochondria of Fus1 KO cells have low reserve respiratory capacity (the ability to produce extra energy during sudden energy demanding situations), and show significantly altered dynamics of cellular calcium response.Our recent studies on early hearing and memory loss in Fus1 KO mice combined with the new data presented here suggest that calcium and energy homeostasis controlled by Fus1 may be at the core of its aging-regulating activities. Thus, Fus1 protein and Fus1-dependent pathways and processes may represent new tools and targets for anti-aging strategies.

Novel Role of the Mitochondrial Protein Fus1 in Protection from Premature Hearing Loss via Regulation of Oxidative Stress and Nutrient and Energy Sensing Pathways in the Inner Ear.

AIMS: Acquired hearing loss is a worldwide epidemic that affects all ages. It is multifactorial in etiology with poorly characterized molecular mechanisms. Mitochondria are critical components in hearing. Here, we aimed to identify the mechanisms of mitochondria-dependent hearing loss using Fus1 KO mice, our novel model of mitochondrial dysfunction/oxidative stress. RESULTS: Using auditory brainstem responses (ABRs), we characterized the Fus1 KO mouse as a novel, clinically relevant model of age-related hearing loss (ARHL) of metabolic etiology. We demonstrated early decline of the endocochlear potential (EP) that may occur due to severe mitochondrial and vascular pathologies in the Fus1 KO cochlear stria vascularis. We showed that pathological alterations in antioxidant (AO) and nutrient and energy sensing pathways (mTOR and PTEN/AKT) occur in cochleae of young Fus1 KO mice before major hearing loss. Importantly, short-term AO treatment corrected pathological molecular changes, while longer AO treatment restored EP, improved ABR parameters, restored mitochondrial structure, and delayed the development of hearing loss in the aging mouse. INNOVATION: Currently, no molecular mechanisms linked to metabolic ARHL have been identified. We established pathological and molecular mechanisms that link the disease to mitochondrial dysfunction and oxidative stress. CONCLUSION: Since chronic mitochondrial dysfunction is common in many patients, it could lead to developing hearing loss that can be alleviated/rescued by AO treatment. Our study creates a framework for clinical trials and introduces the Fus1 KO model as a powerful platform for developing novel therapeutic strategies to prevent/delay hearing loss associated with mitochondrial dysfunction. Antioxid. Redox Signal. 27, 489-509.

TUSC2 downregulates PD-L1 expression in non-small cell lung cancer (NSCLC).

Expression of the TUSC2 tumor-suppressor gene in TUSC2-deficient NSCLC cells decreased PD-L1 expression and inhibited mTOR activity. Overexpressing TUSC2 or treatment with rapamycin resulted in similar inhibition of PD-L1 expression. Both TUSC2 and rapamycin decreased p70 and SK6 phosphorylation, suggesting that TUSC2 and rapamycin share the same mTOR target. Microarray mRNA expression analysis using TUSC2-inducible H1299 showed that genes that negatively regulate the mTOR pathway were significantly upregulated by TUSC2 compared with control. The presence of IFN-γ significantly increased PD-L1 expression in lung cancer cell lines, but overexpressing TUSC2 in these cell lines prevented PD-L1 from increasing in the presence of IFN-γ. Taken together, these findings show that TUSC2 can decrease PD-L1 expression in lung cancer cells. This ability to modify the tumor microenvironment suggests that TUSC2 could be added to checkpoint inhibitors to improve the treatment of lung cancer.

Fus1 KO Mouse As a Model of Oxidative Stress-Mediated Sporadic Alzheimer's Disease: Circadian Disruption and Long-Term Spatial and Olfactory Memory Impairments.

Insufficient advances in the development of effective therapeutic treatments of sporadic Alzheimer's Disease (sAD) to date are largely due to the lack of sAD-relevant animal models. While the vast majority of models do recapitulate AD's hallmarks of plaques and tangles by virtue of tau and/or beta amyloid overexpression, these models do not reflect the fact that in sAD (unlike familial AD) these genes are not risk factors per se and that other mechanisms like oxidative stress, metabolic dysregulation and inflammation play key roles in AD etiology. Here we characterize and propose the Fus1 KO mice that lack a mitochondrial protein Fus1/Tusc2 as a new sAD model. To establish sAD relevance, we assessed sAD related deficits in Fus1 KO and WT adult mice of 4-5 months old, the equivalent human age when the earliest cognitive and olfactory sAD symptoms arise. Fus1 KO mice showed oxidative stress (increased levels of ROS, decreased levels of PRDX1), disruption of metabolic homeostasis (decreased levels of ACC2, increased phosphorylation of AMPK), autophagy (decreased levels of LC3-II), PKC (decreased levels of RACK1) and calcium signaling (decreased levels of Calb2) in the olfactory bulb and/or hippocampus. Mice were behaviorally tested using objective and accurate video tracking (Noldus), in which Fus1 KO mice showed clear deficits in olfactory memory (decreased habituation/cross-habituation in the short and long term), olfactory guided navigation memory (inability to reduce their latency to find the hidden cookie), spatial memory (learning impairments on finding the platform in the Morris water maze) and showed more sleep time during the diurnal cycle. Fus1 KO mice did not show clear deficits in olfactory perception (cross-habituation), association memory (passive avoidance) or in species-typical behavior (nest building) and no increased anxiety (open field, light-dark box) or depression/anhedonia (sucrose preference) at this relatively young age. These neurobehavioral deficits of the Fus1 KO mice at this relatively young age are highly relevant to sAD, making them suitable for effective research on pharmacological targets in the context of early intervention of sAD.

TWIST1/miR-584/TUSC2 pathway induces resistance to apoptosis in thyroid cancer cells.

TWIST1, a transcription factor, plays a pivotal role in cancer initiation and progression. Anaplastic thyroid carcinoma (ATC) is one of the deadliest human malignancies; TWIST1 is overexpressed in ATC and increases thyroid cancer cell survival, migration and invasion. The molecular mechanisms underlying the effects of TWIST1 are partially known. Here, using miRNome profiling of papillary thyroid cancer cells (TPC-1) ectopically expressing TWIST1, we identified miR-584. We showed that TWIST1 directly binds miR-584 using chromatin immunoprecipitation. Importantly, miR-584 was up-regulated in human ATC compared to papillary thyroid carcinoma (PTC) and normal thyroid samples. Overexpression of miR-584 in TPC cells induced resistance to apoptosis, whereas stable transfection of anti-miR-584 in TPC-TWIST1 and 8505C cells increased the sensitivity to apoptosis. Using bioinformatics programs, we identified TUSC2 (tumor suppressor candidate 2) as a novel target of miR-584. TUSC2 mRNA and protein levels were decreased in TPC miR-584 and increased in TPC-TWIST1 anti-miR-584 cells. Luciferase assays demonstrated direct targeting. Restored expression of TUSC2 rescued the inhibition of apoptosis induced by miR-584. Finally, qRT-PCR and immunohistochemical analysis showed that TUSC2 was down-regulated in ATC and PTC samples compared to normal thyroids. In conclusion, our study identified a novel TWIST1/miR-584/TUSC2 pathway that plays a role in resistance to apoptosis of thyroid cancer cells.

Mitochondria, calcium, and tumor suppressor Fus1: At the crossroad of cancer, inflammation, and autoimmunity.

Mitochondria present a unique set of key intracellular functions such as ATP synthesis, production of reactive oxygen species (ROS) and Ca2+ buffering. Mitochondria both encode and decode Ca2+ signals and these interrelated functions have a direct impact on cell signaling and metabolism. High proliferative potential is a key energy-demanding feature shared by cancer cells and activated T lymphocytes. Switch of a metabolic state mediated by alterations in mitochondrial homeostasis plays a fundamental role in maintenance of the proliferative state. Recent studies show that tumor suppressors have the ability to affect mitochondrial homeostasis controlling both cancer and autoimmunity. Herein, we discuss established and putative mechanisms of calcium-dependent regulation of both T cell and tumor cell activities. We use the mitochondrial protein Fus1 as a case of tumor suppressor that controls immune response and tumor growth via maintenance of mitochondrial homeostasis. We focus on the regulation of mitochondrial Ca2+ handling as a key function of Fus1 and highlight the mechanisms of a crosstalk between Ca2+ accumulation and mitochondrial homeostasis. Given the important role of Ca2+ signaling, mitochondrial Ca2+ transport and ROS production in the activation of NFAT and NF-κB transcription factors, we outline the importance of Fus1 activities in this context.