TCTP overexpression is associated with the development and progression of glioma

Biological role and expression of translationally controlled tumor protein (TCTP) in tumorigenesis and development and its potential for targeted tumor therapy

Translationally controlled tumor protein (TCTP), also known as histamine-releasing factor (HRF) or fortilin, is a highly conserved protein found in various species. To date, multiple studies have demonstrated the crucial role of TCTP in a wide range of cellular pathophysiological processes, including cell proliferation and survival, cell cycle regulation, cell death, as well as cell migration and movement, all of which are major pathogenic mechanisms of tumorigenesis and development. This review aims to provide an in-depth analysis of the functional role of TCTP in tumor initiation and progression, with a particular focus on cell proliferation, cell death, and cell migration. It will highlight the expression and pathological implications of TCTP in various tumor types, summarizing the current prevailing therapeutic strategies that target TCTP.

Prognostic value of translationally controlled tumor protein in colon cancer

The translationally controlled tumor protein (TCTP) is a highly conserved protein involved in a variety of normal cell functions and disease processes. Preclinical studies revealed that TCTP has anti-apoptotic properties, promotes cell growth and division and is involved in cancer progression by promoting invasion and metastasis. The present study explored the potential value of TCTP as a prognostic marker in colon cancer. A retrospective analysis of 74 patients with colon cancer was performed. Using immunohistochemistry, TCTP levels in the primary tumor were assessed semi-quantitatively by the calculation of cytoplasmic and nuclear H-score. Cytoplasmic TCTP levels in the primary tumor had no statistically significant association with disease-free survival (DFS), progression-free survival (PFS) and overall survival (OS) in the present patient population. Patients whose primary tumors had a negative nuclear TCTP expression had significantly improved clinical outcomes. The PFS for the negative nuclear TCTP expression group was 7.7 months [95% confidence interval (CI), 5.8-9.5] compared with 5.5 months (95% CI, 3.2-7.8) in the group with positive nuclear expression (P=0.023, Mantel-Cox log-rank). Patients with a negative nuclear expression of TCTP had a significantly higher median OS (22.2 months; 95% CI, 16.1-28.3) compared with those with positive TCTP nuclear expression (median 13.2 months; 95% CI, 10.1-16.3; P=0.008, Mantel-Cox log-rank). In a multivariate Cox regression model, a positive nuclear TCTP H-score was an independent risk factor for worse PFS and OS. The 1-year OS rate in the group with negative nuclear TCTP expression was 86.3% compared with 56.5% in patients with positive nuclear TCTP expression (P=0.008). The present study suggested that semiquantitative H-score measurement of TCTP levels in the nuclei of tumor cells from the primary tumor is a potential prognostic marker for clinical outcomes in patients with colon cancer.

Harnessing the value of TCTP in breast cancer treatment resistance: an opportunity for personalized therapy

Early identification of breast cancer (BC) patients at a high risk of progression may aid in therapeutic and prognostic aims. This is especially true for metastatic disease, which is responsible for most cancer-related deaths. Growing evidence indicates that the translationally controlled tumor protein (TCTP) may be a clinically relevant marker for identifying poorly differentiated aggressive BC tumors. TCTP is an intriguing protein with pleiotropic functions, which is involved in multiple signaling pathways. TCTP may also be involved in stress response, cell growth and proliferation-related processes, underlying its potential role in the initiation of metastatic growth. Thus, TCTP marks specific cancer cell sub-populations with pronounced stress adaptation, stem-like and immune-evasive properties. Therefore, we have shown that in vivo phospho-TCTP levels correlate with the response of BC cells to anti-HER2 agents. In this review, we discuss the clinical relevance of TCTP for personalized therapy, specific TCTP-targeting strategies, and currently available therapeutic agents. We propose TCTP as an actionable clinically relevant target that could potentially improve patient outcomes.

AMG900 as novel inhibitor of the translationally controlled tumor protein

INTRODUCTION

Cancer is one of the leading causes of death worldwide. Classical cytotoxic chemotherapy exerts high side effects and low tumor selectivity. Translationally controlled tumor protein (TCTP) is a target for differentiation therapy, a promising, new therapeutic approach, which is expected to be more selective and less toxic than cytotoxic chemotherapy. The aim of the present investigation was to identify novel TCTP inhibitors.

METHODS

We performed in silico screening and molecular docking using a chemical library of more than 31,000 compounds to identify a novel inhibitor of TCTP. We tested AMG900 in vitro for binding to TCTP by microscale thermophoresis and co-immunoprecipitation. Additionally, we examined the effect of TCTP blockade on cell cycle progression by flow cytometry and Western blotting and cancer cell survival by resazurin assays in MCF-7, SK-OV3 and MOLT-4 cell lines.

RESULTS

We identified AMG900 as new inhibitor of TCTP. AMG900 bound to the p53 binding site of TCTP with a free binding energy of -9.63 ± 0.01 kcal/mol. This compound decreased TCTP expression to 23.4 ± 1.59% and increased p53 expression to 194.29 ± 24.27%. Furthermore, AMG900 induced G0/G1 arrest as shown by flow cytometry and Western blot of relevant cell cycle proteins. AMG900 decreased CDK2, CDK4, CDK6, cyclin D1 and cyclin D3 expression, whereas p18, p21 and p27 expression increased. Moreover, AMG900 disturbed TCTP-p53 complexation as shown by co-immunoprecipitation and increased expression of free p53.

DISCUSSION

AMG900 may serve as novel lead compound for the development of differentiation therapy approaches against cancer.

DHA Affects Microtubule Dynamics Through Reduction of Phospho-TCTP Levels and Enhances the Antiproliferative Effect of T-DM1 in Trastuzumab-Resistant HER2-Positive Breast Cancer Cell Lines

Trastuzumab emtansine (T-DM1) is an anti-human epidermal growth factor receptor 2 (HER2) antibody-drug conjugated to the microtubule-targeting agent emtansine (DM1). T-DM1 is an effective agent in the treatment of patients with HER2-positive breast cancer whose disease has progressed on the first-line trastuzumab containing chemotherapy. However, both primary and acquired tumour resistance limit its efficacy. Increased levels of the phosphorylated form of Translationally Controlled Tumour Protein (phospho-TCTP) have been shown to be associated with a poor clinical response to trastuzumab therapy in HER2-positive breast cancer. Here we show that phospho-TCTP is essential for correct mitosis in human mammary epithelial cells. Reduction of phospho-TCTP levels by dihydroartemisinin (DHA) causes mitotic aberration and increases microtubule density in the trastuzumab-resistant breast cancer cells HCC1954 and HCC1569. Combinatorial studies show that T-DM1 when combined with DHA is more effective in killing breast cells compared to the effect induced by any single agent. In an orthotopic breast cancer xenograft model (HCC1954), the growth of the tumour cells resumes after having achieved a complete response to T-DM1 treatment. Conversely, DHA and T-DM1 treatment induces a severe and irreversible cytotoxic effect, even after treatment interruption, thus, improving the long-term efficacy of T-DM1. These results suggest that DHA increases the effect of T-DM1 as poison for microtubules and supports the clinical development of the combination of DHA and T-DM1 for the treatment of aggressive HER2-overexpressing breast cancer.

Downregulation of transcription factor TCTP elevates microRNA-200a expression to restrain Myt1L expression, thereby improving neurobehavior and oxidative stress injury in cerebral palsy rats

Transcription factors have already been proposed to work on some human diseases. Yet the role of translationally controlled tumor protein (TCTP) in cerebral palsy (CP) remains elusive. This study intends to examine the mechanism of TCTP on CP by regulating microRNA-200a (miR-200a).CP models of rats were established referring to the internationally recognized improved hypoxic ischemic encephalopathy modeling method. The neuroethology of rats, ultrastructure and pathological condition in brain tissues of rats were observed through several assays. The expression of TCTP, miR-200a, myelin transcription factor 1-like (Myt1L), tyrosine hydroxylase (TH) and inducible nitric oxide synthase (iNOS) along with apoptosis in brain tissues of rats was detected. The levels of reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in brain tissues of rats were determined. The binding site between miR-200a and Myt1L was analyzed.TCTP and Myt1L were overexpressed and miR-200a was under-expressed in CP rats. Elevated miR-200a ameliorated neurobehavior of CP rats and pathological injury in brain tissues. Elevated miR-200a up-regulated TH, GSH, GSH-Px, and SOD levels, down-regulated iNOS, ROS, MDA, TNF-α, and IL-6 levels, and attenuated neuronal apoptosis in brain tissues of CP rats. Myt1L was a target gene of miR-200a.Altogether, our study suggested that diminution of transcription factor TCTP up-regulates miR-200a to limit Myt1L expression, thereby improving neurobehavior and oxidative stress injury in CP rats.

Regulation of Autophagy Is a Novel Tumorigenesis-Related Activity of Multifunctional Translationally Controlled Tumor Protein

Translationally controlled tumor protein (TCTP) is highly conserved in eukaryotic organisms and plays multiple roles regulating cellular growth and homeostasis. Because of its anti-apoptotic activity and its role in the regulation of cancer metastasis, TCTP has become a promising target for cancer therapy. Moreover, growing evidence points to its clinical role in cancer prognosis. How TCTP regulates cellular growth in cancer has been widely studied, but how it regulates cellular homeostasis has received relatively little attention. This review discusses how TCTP is related to cancer and its potential as a target in cancer therapeutics, including its novel role in the regulation of autophagy. Regulation of autophagy is essential for cell recycling and scavenging cellular materials to sustain cell survival under the metabolic stress that cancer cells undergo during their aggressive proliferation.

A Potential Role for Exosomal Translationally Controlled Tumor Protein Export in Vascular Remodeling in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is characterized by increased proliferation and resistance to apoptosis of pulmonary vascular cells. Increased expression of translationally controlled tumor protein (TCTP), a prosurvival and antiapoptotic mediator, has recently been demonstrated in patients with heritable PAH; however, its role in the pathobiology of PAH remains unclear. Silencing of TCTP in blood outgrowth endothelial cells (BOECs) isolated from control subjects led to significant changes in morphology, cytoskeletal organization, increased apoptosis, and decreased directionality during migration. Because TCTP is also localized in extracellular vesicles, we isolated BOEC-derived extracellular vesicles (exosomes and microparticles) by sequential ultracentrifugation. BOECs isolated from patients harboring BMPR2 mutations released more exosomes than those derived from control subjects in proapoptotic conditions. Furthermore, TCTP expression was significantly higher in exosomes than in microparticles, indicating that TCTP is mainly exported via exosomes. Coculture assays demonstrated that exosomes transferred TCTP from ECs to pulmonary artery smooth muscle cells, suggesting a role for endothelial-derived TCTP in conferring proliferation and apoptotic resistance. In an experimental model of PAH, rats treated with monocrotaline demonstrated increased concentrations of TCTP in the lung and plasma. Consistent with this finding, we observed increased circulating TCTP levels in patients with idiopathic PAH compared with control subjects. Therefore, our data suggest an important role for TCTP in regulating the critical vascular cell phenotypes that have been implicated in the pathobiology of PAH. In addition, this research implicates TCTP as a potential biomarker for the onset and development of PAH.

Radiosensitivity of Cancer Cells Is Regulated by Translationally Controlled Tumor Protein

Translationally controlled tumor protein (TCTP) is a ubiquitous multifunctional protein that is essential for cell survival. This study reveals that the regulation of radiosensitivity of cancer cells is yet another function of TCTP. The relationship between endogenous TCTP levels and sensitivity to radiation was examined in breast cancer cell lines (T47D, MDA-MB-231, and MCF7) and lung cancer cells lines (A549, H1299, and H460). Cancer cells with high expression levels of TCTP were more resistant to radiation. TCTP overexpression inhibited radiation-induced cell death, while silencing TCTP led to an increase in radiosensitivity. DNA damage in the irradiated TCTP-silenced A549 cells was greater than in irradiated control shRNA-transfected A549 cells. p53, a well-known reciprocal regulator of TCTP, was increased in irradiated TCTP down-regulated A549 cells. Moreover, introduction of p53 siRNA in TCTP knocked-down A549 cells abrogated the increased radiosensitivity induced by TCTP knockdown. An in vivo xenograft study also confirmed enhanced radiosensitivity in TCTP down-regulated A549 cells. These findings suggest that TCTP has the potential to serve as a therapeutic target to overcome radiation resistance in cancer, a major problem for the effective treatment of cancers.

Mongolian Medicine RuXian-I Treatment of Estrogen-Induced Mammary Gland Hyperplasia in Rats Related to TCTP Regulating Apoptosis

Mongolian medicine RuXian-I is composed of 30 Mongolian herbs, which is a traditional Mongolian recipe for clinical treatment of breast "Qi Su Bu Ri Le Du Sen" disease (hyperplasia of mammary glands, HMG). Based on the previous study, this dissertation further explores the therapeutic mechanism of RuXian-I on estrogen-induced HMG in rats. RuXian-I had no effect on the body weight and food intake of HMG rats and had no toxic effects on the five organs (heart, lung, spleen, and kidney). RuXian-I reduced the diameter and height of nipple, organ index, and pathological changes and alleviated the sex hormone levels oh HMG; RuXian-I reduced the upregulation of TCTP, Mcl-1, and Bcl-xL in breast tissue of mammary gland hyperplasia and increased the downregulation of p53, Bax, caspase-9, and caspase-3 protein. RuXian-I has an effective therapeutic activity on HMG rats, and its possible therapeutic mechanism is closely related to antiapoptosis protein TCTP-regulated apoptosis.

Suppressor of Variegation 3-9 Homolog 2, a Novel Binding Protein of Translationally Controlled Tumor Protein, Regulates Cancer Cell Proliferation

Suppressor of Variegation 3-9 Homolog 2 (SUV39H2) methylates the lysine 9 residue of histone H3 and induces heterochromatin formation, resulting in transcriptional repression or silencing of target genes. SUV39H1 and SUV39H2 have a role in embryonic development, and SUV39H1 was shown to suppress cell cycle progression associated with Rb. However, the function of human SUV39H2 has not been extensively studied. We observed that forced expression of SUV39H2 decreased cell proliferation by inducing G1 cell cycle arrest. In addition, SUV39H2 was degraded through the ubiquitin-proteasomal pathway. Using yeast two-hybrid screening to address the degradation mechanism and function of SUV39H2, we identified translationally controlled tumor protein (TCTP) as an SUV39H2-interacting molecule. Mapping of the interacting regions indicated that the N-terminal 60 amino acids (aa) of full-length SUV39H2 and the C-terminus of TCTP (120-172 aa) were critical for binding. The interaction of SUV39H2 and TCTP was further confirmed by co-immunoprecipitation and immunofluorescence staining for colocalization. Moreover, depletion of TCTP by RNAi led to up-regulation of SUV39H2 protein, while TCTP overexpression reduced SUV39H2 protein level. The half-life of SUV39H2 protein was significantly extended upon TCTP depletion. These results clearly indicate that TCTP negatively regulates the expression of SUV39H2 post-translationally. Furthermore, SUV39H2 induced apoptotic cell death in TCTP-knockdown cells. Taken together, we identified SUV39H2, as a novel target protein of TCTP and demonstrated that SUV39H2 regulates cell proliferation of lung cancer cells.

Growth Cone Tctp Is Dynamically Regulated by Guidance Cues

Translationally controlled tumor protein (Tctp) contributes to retinal circuitry formation by promoting axon growth and guidance, but it remains unknown to what extent axonal Tctp specifically influences axon development programs. Various genome-wide profiling studies have ranked tctp transcripts among the most enriched in the axonal compartment of distinct neuronal populations, including embryonic retinal ganglion cells (RGCs), suggesting its expression can be regulated locally and that this may be important during development. Here, we report that growth cone Tctp levels change rapidly in response to Netrin-1 and Ephrin-A1, two guidance cues encountered by navigating RGC growth cones. This regulation is opposite in effect, as we observed protein synthesis- and mTORC1-dependent increases in growth cone Tctp levels after acute treatment with Netrin-1, but a decline upon exposure to Ephrin-A1, an inhibitor of mTORC1. Live imaging with translation reporters further showed that Netrin-1-induced synthesis of Tctp in growth cones is driven by a short 3'untranslated region (3'UTR) tctp mRNA isoform. However, acute inhibition of de novo Tctp synthesis in axons did not perturb the advance of retinal projections through the optic tract in vivo, indicating that locally produced Tctp is not necessary for normal axon growth and guidance.

Impact of mesenchymal stem cells' secretome on glioblastoma pathophysiology

Background

Glioblastoma (GBM) is a highly aggressive primary brain cancer, for which curative therapies are not available. An emerging therapeutic approach suggested to have potential to target malignant gliomas has been based on the use of multipotent mesenchymal stem cells (MSCs), either unmodified or engineered to deliver anticancer therapeutic agents, as these cells present an intrinsic capacity to migrate towards malignant tumors. Nevertheless, it is still controversial whether this innate tropism of MSCs towards the tumor area is associated with cancer promotion or suppression. Considering that one of the major mechanisms by which MSCs interact with and modulate tumor cells is via secreted factors, we studied how the secretome of MSCs modulates critical hallmark features of GBM cells.

Methods

The effect of conditioned media (CM) from human umbilical cord perivascular cells (HUCPVCs, a MSC population present in the Wharton’s jelly of the umbilical cord) on GBM cell viability, migration, proliferation and sensitivity to temozolomide treatment of U251 and SNB-19 GBM cells was evaluated. The in vivo chicken chorioallantoic membrane (CAM) assay was used to evaluate the effect of HUCPVCs CM on tumor growth and angiogenesis. The secretome of HUCPVCs was characterized by proteomic analyses.

Results

We found that both tested GBM cell lines exposed to HUCPVCs CM presented significantly higher cellular viability, proliferation and migration. In contrast, resistance of GBM cells to temozolomide chemotherapy was not significantly affected by HUCPVCs CM. In the in vivo CAM assay, CM from HUCPVCs promoted U251 and SNB-19 tumor cells growth. Proteomic analysis to characterize the secretome of HUCPVCs identified several proteins involved in promotion of cell survival, proliferation and migration, revealing novel putative molecular mediators for the effects observed in GBM cells exposed to HUCPVCs CM.

Conclusions

These findings provide novel insights to better understand the interplay between GBM cells and MSCs, raising awareness to potential safety issues regarding the use of MSCs as stem-cell based therapies for GBM.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1303-8) contains supplementary material, which is available to authorized users.

Knockdown of translationally controlled tumor protein inhibits growth, migration and invasion of lung cancer cells

AIM

To investigate the role of translationally controlled tumor protein (TCTP) in lung cancer development.

MAIN METHODS

A549 and HCC827 cells were transfected with shRNA specifically targeting TCTP mRNA. Cell growth was assessed by colony formation assay and cell counting kit-8. Cell cycle and apoptosis were analyzed by flow cytometry. Cell migration and invasion was measured by scratch and transwell assays. In vivo tumorigenicity was evaluated by tumor xenografts in nude mice.

KEY FINDINGS

TCTP-silenced cells displayed a reduced ability of colony formation and a lower rate of proliferation in vitro. Knockdown of TCTP arrested cell cycle at G1 phase and led to downregulated expression of cyclins B1, D1 and E. Moreover, silencing of TCTP induced apoptosis and altered the levels of apoptosis-regulatory proteins such as cleaved caspase-3, Bcl-2, Bax and p53. Silencing of TCTP also inhibited migration and invasion of lung cancer cells. In addition, TCTP-silenced A549 cells, when subcutaneously inoculated in nude mice, formed tumors at a significantly slower rate.

SIGNIFICANCE

Our in vitro and in vivo data indicate that silencing of TCTP inhibits growth, migration and invasion of lung cancer cells. Thus, TCTP may be a potential target for lung cancer therapy.

Fortilin: A Potential Target for the Prevention and Treatment of Human Diseases

Fortilin is a highly conserved 172-amino-acid polypeptide found in the cytosol, nucleus, mitochondria, extracellular space, and circulating blood. It is a multifunctional protein that protects cells against apoptosis, promotes cell growth and cell cycle progression, binds calcium (Ca²⁺) and has antipathogen activities. Its role in the pathogenesis of human and animal diseases is also diverse. Fortilin facilitates the development of atherosclerosis, contributes to both systemic and pulmonary arterial hypertension, participates in the development of cancers, and worsens diabetic nephropathy. It is important for the adaptive expansion of pancreatic β-cells in response to obesity and increased insulin requirement, for the regeneration of liver after hepatectomy, and for protection of the liver against alcohol- and ER stress-induced injury. Fortilin is a viable surrogate marker for in vivo apoptosis, and it plays a key role in embryo and organ development in vertebrates. In fish and shrimp, fortilin participates in host defense against bacterial and viral pathogens. Further translational research could prove fortilin to be a viable molecular target for treatment of various human diseases including and not limited to atherosclerosis, hypertension, certain tumors, diabetes mellitus, diabetic nephropathy, hepatic injury, and aberrant immunity and host defense.

HpSlyD inducing CDX2 and VIL1 expression mediated through TCTP protein may contribute to intestinal metaplasia in the stomach

Helicobacter pylori infection is the most important risk factor for gastric intestinal metaplasia (IM). Our previous study demonstrated that infection with H. pylori HpslyD-positive strains associated with IM. To further investigate the signalling pathway involved in HpSlyD-induced IM, CDX2 and VIL1 expressions were determined before and after HpSlyD application. TCTP was knocked down by siRNA or overexpressed by plasmid transfection. An HpSlyD binding protein was used to block HpSlyD's enzymatic activity. The expression of CDX2 and TCTP in gastric diseases was measured by immunohistochemistry. Our results showed HpSlyD induced CDX2 and VIL1 expressions. TCTP protein expression was markedly increased after application of HpSlyD and in an HpSlyD-expressing stable cell line. Downregulation of TCTP protein led to decreased HpSlyD-induced CDX2 and VIL1. Overexpression of TCTP protein improved the expression of CDX2 and VIL1. Co-application of HpSlyD and FK506 led to significant reductions in CDX2, VIL1, and TCTP expression. Immunohistochemistry demonstrated that CDX2 and TCTP expression was higher in HpslyD-positive specimens compared with HpslyD-negative ones. Expression of CDX2 was positively correlated with TCTP in HpslyD-positive cells. Our study is the first to show that HpSlyD induction of CDX2 and VIL1 expression mediated through TCTP may contribute to IM in the stomach.

Immunohistochemical Localization of Translationally Controlled Tumor Protein in Axon Terminals of Mouse Hippocampal Neurons

Translationally controlled tumor protein (TCTP) is a cytosolic protein with microtubule stabilization and calcium-binding activities. TCTP is expressed in most organs including the nervous system. However, detailed distribution and functional significance of TCTP in the brain remain unexplored. In this study, we investigated the global and subcellular distributions of TCTP in the mouse brain. Immunohistochemical analyses with anti-TCTP revealed that TCTP was widely distributed in almost all regions of the brain including the cerebral cortex, thalamus, hypothalamus, hippocampus, and amygdala, wherein it was localized in axon tracts and axon terminals. In the hippocampus, TCTP was prominently localized to axon terminals of the perforant path in the dentate gyrus, the mossy fibers in the cornu ammonis (CA)3 region, and the Schaffer collaterals in the CA1 field, but not in cell bodies of granule cells and pyramidal neurons, and in their dendritic processes. Widespread distribution of TCTP in axon tracts and axon terminals throughout the brain suggests that TCTP is likely involved in neurotransmitter release and/or maintaining synaptic structures in the brain, and that it might have a role in maintaining synaptic functions and synaptic configurations important for normal cognitive, stress and emotional functions.

Translationally controlled tumour protein TCTP is induced early in human colorectal tumours and contributes to the resistance of HCT116 colon cancer cells to 5-FU and oxaliplatin

Background

Translationally controlled tumour protein TCTP is an anti-apoptotic protein frequently overexpressed in cancers, where high levels are often associated with poor patient outcome. TCTP may be involved in protecting cancer cells against the cytotoxic action of anti-cancer drugs. Here we study the early increase of TCTP levels in human colorectal cancer (CRC) and the regulation of TCTP expression in HCT116 colon cancer cells, in response to treatment with the anti-cancer drugs 5-FU and oxaliplatin.

Methods

Using immunohistochemistry, we assessed TCTP levels in surgical samples from adenomas and adenocarcinomas of the colon, compared to normal colon tissue. We also studied the regulation of TCTP in HCT116 colon cancer cells in response to 5-FU and oxaliplatin by western blotting. TCTP mRNA levels were assessed by RT-qPCR. We used mTOR kinase inhibitors to demonstrate mTOR-dependent translational regulation of TCTP under these conditions. Employing the Real-Time Cell Analysis (RTCA) System and the MTS assay, we investigated the effect of TCTP-knockdown on the sensitivity of HCT116 cells to the anti-cancer drugs 5-FU and oxaliplatin.

Results

1. TCTP levels are significantly increased in colon adenomas and adenocarcinomas, compared to normal colon tissue. 2. TCTP protein levels are about 4-fold upregulated in HCT116 colon cancer cells, in response to 5-FU and oxaliplatin treatment, whereas TCTP mRNA levels are down regulated. 3. mTOR kinase inhibitors prevented the up-regulation of TCTP protein, indicating that TCTP is translationally regulated through the mTOR complex 1 signalling pathway under these conditions. 4. Using two cellular assay systems, we demonstrated that TCTP-knockdown sensitises HCT116 cells to the cytotoxicity caused by 5-FU and oxaliplatin.

Conclusions

Our results demonstrate that TCTP levels increase significantly in the early stages of CRC development. In colon cancer cells, expression of this protein is largely upregulated during treatment with the DNA-damaging anti-cancer drugs 5-FU and oxaliplatin, as part of the cellular stress response. TCTP may thus contribute to the development of anti-cancer drug resistance. These findings indicate that TCTP might be suitable as a biomarker and that combinatorial treatment using 5-FU/oxaliplatin, together with mTOR kinase inhibitors, could be a route to preventing the development of resistance to these drugs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-017-0164-3) contains supplementary material, which is available to authorized users.

The Translational Controlled Tumour Protein TCTP: Biological Functions and Regulation

The Translational Controlled Tumour Protein TCTP (gene symbol TPT1, also called P21, P23, Q23, fortilin or histamine-releasing factor, HRF) is a highly conserved protein present in essentially all eukaryotic organisms and involved in many fundamental cell biological and disease processes. It was first discovered about 35 years ago, and it took an extended period of time for its multiple functions to be revealed, and even today we do not yet fully understand all the details. Having witnessed most of this history, in this chapter, I give a brief overview and review the current knowledge on the structure, biological functions, disease involvements and cellular regulation of this protein.TCTP is able to interact with a large number of other proteins and is therefore involved in many core cell biological processes, predominantly in the response to cellular stresses, such as oxidative stress, heat shock, genotoxic stress, imbalance of ion metabolism as well as other conditions. Mechanistically, TCTP acts as an anti-apoptotic protein, and it is involved in DNA-damage repair and in cellular autophagy. Thus, broadly speaking, TCTP can be considered a cytoprotective protein. In addition, TCTP facilitates cell division through stabilising the mitotic spindle and cell growth through modulating growth signalling pathways and through its interaction with the proteosynthetic machinery of the cell. Due to its activities, both as an anti-apoptotic protein and in promoting cell growth and division, TCTP is also essential in the early development of both animals and plants.Apart from its involvement in various biological processes at the cellular level, TCTP can also act as an extracellular protein and as such has been involved in modulating whole-body defence processes, namely in the mammalian immune system. Extracellular TCTP, typically in its dimerised form, is able to induce the release of cytokines and other signalling molecules from various types of immune cells. There are also several examples, where TCTP was shown to be involved in antiviral/antibacterial defence in lower animals. In plants, the protein appears to have a protective effect against phytotoxic stresses, such as flooding, draught, too high or low temperature, salt stress or exposure to heavy metals. The finding for the latter stress condition is corroborated by earlier reports that TCTP levels are considerably up-regulated upon exposure of earthworms to high levels of heavy metals.Given the involvement of TCTP in many biological processes aimed at maintaining cellular or whole-body homeostasis, it is not surprising that dysregulation of TCTP levels may promote a range of disease processes, foremost cancer. Indeed a large body of evidence now supports a role of TCTP in at least the most predominant types of human cancers. Typically, this can be ascribed to both the anti-apoptotic activity of the protein and to its function in promoting cell growth and division. However, TCTP also appears to be involved in the later stages of cancer progression, such as invasion and metastasis. Hence, high TCTP levels in tumour tissues are often associated with a poor patient outcome. Due to its multiple roles in cancer progression, TCTP has been proposed as a potential target for the development of new anti-cancer strategies in recent pilot studies. Apart from its role in cancer, TCTP dysregulation has been reported to contribute to certain processes in the development of diabetes, as well as in diseases associated with the cardiovascular system.Since cellular TCTP levels are highly regulated, e.g. in response to cell stress or to growth signalling, and because deregulation of this protein contributes to many disease processes, a detailed understanding of regulatory processes that impinge on TCTP levels is required. The last section of this chapter summarises our current knowledge on the mechanisms that may be involved in the regulation of TCTP levels. Essentially, expression of the TPT1 gene is regulated at both the transcriptional and the translational level, the latter being particularly advantageous when a rapid adjustment of cellular TCTP levels is required, for example in cell stress responses. Other regulatory mechanisms, such as protein stability regulation, may also contribute to the regulation of overall TCTP levels.

Role of TCTP for Cellular Differentiation and Cancer Therapy

The translationally controlled tumor protein (TCTP) is a highly conserved protein that is regulated due to a high number of extracellular stimuli. TCTP has an important role for cell cycle and normal development. On the other side, tumor reversion and malignant transformation have been associated with TCTP. TCTP has been found among the 12 genes that are differentially expressed during mouse oocyte maturation, and an overexpression of this gene was reported in a wide variety of different cancer types. Its antiapoptotic effect is indicated by the interaction with several proapoptotic proteins of the Bcl-2 family and the p53 tumor suppressor protein. In this article, we draw attention to the role of TCTP in cancer, especially, focusing on cell differentiation and tumor reversion, a biological process by which highly tumorigenic cells lose their malignant phenotype. This protein has been shown to be the most strongly downregulated protein in revertant cells compared to the parental cancer cells. Decreased expression of TCTP results either in the reprogramming of cancer cells into reversion or apoptosis. As conventional chemotherapy is frequently associated with the development of drug resistance and high toxicity, the urge for the development of new or additional scientific approaches falls into place. Differentiation therapy aims at reinducing differentiation backward to the nonmalignant cellular state. Here, different approaches have been reported such as the induction of retinoid pathways and the use of histone deacetylase inhibitors. Also, PPARγ agonists and the activation of the vitamin D receptor have been reported as potential targets in differentiation therapy. As TCTP is known as the histamine-releasing factor, antihistaminic drugs have been shown to target this protein. Antihistaminic compounds, hydroxyzine and promethazine, inhibited cell growth of cancer cells and decreased TCTP expression of breast cancer and leukemia cells. Recently, we found that two antihistaminics, levomepromazine and buclizine, inhibited cancer cell growth by direct binding to TCTP and induction of cell differentiation. These data confirmed that TCTP is an exquisite target for anticancer differentiation therapy and antihistaminics have potential to be lead compounds for the direct interaction with TCTP as new inhibitors of human TCTP and tumor growth.

Characterization of the Translationally Controlled Tumor Protein (TCTP) Interactome Reveals Novel Binding Partners in Human Cancer Cells

Translationally controlled tumor protein (TCTP) is a highly conserved housekeeping protein present in eukaryotic organisms. It is involved in regulating many fundamental processes and plays a critical role in tumor reversion and tumorigenesis. Increasing evidence suggests that TCTP plays a role in the regulation of cell fate determination and is a promising therapeutic target for cancer. To decipher the exact mechanisms by which TCTP functions and how all these functions are integrated, we analyzed the interactome of TCTP in HeLa cells by coimmunoprecipitation (IP) and mass spectrometry (MS). A total of 98 proteins were identified. We confirmed the in vitro and in vivo association of TCTP with six of the identified binding proteins using reciprocal IP and bimolecular fluorescence complementation (BiFC) analysis, respectively. Moreover, TCTP interacted with Y-box-binding protein 1 (YBX1), and their interaction was localized to the N-terminal region of TCTP and the 1-129 amino acid (aa) residues of YBX1. The YBX1 protein plays an important role in cell proliferation, RNA splicing, DNA repair, drug resistance, and stress response to extracellular signals. These data suggest that the interaction of TCTP with YBX1 might cooperate or coordinate their functions in the control of diverse regulatory pathways in cancer cells. Taken together, our results not only reveal a large number of TCTP-associated proteins that possess pleiotropic functions, but also provide novel insights into the molecular mechanisms of TCTP in tumorigenesis.

Tumor protein Tctp regulates axon development in the embryonic visual system

The transcript encoding translationally controlled tumor protein (Tctp), a molecule associated with aggressive breast cancers, was identified among the most abundant in genome-wide screens of axons, suggesting that Tctp is important in neurons. Here, we tested the role of Tctp in retinal axon development in Xenopus laevis. We report that Tctp deficiency results in stunted and splayed retinotectal projections that fail to innervate the optic tectum at the normal developmental time owing to impaired axon extension. Tctp-deficient axons exhibit defects associated with mitochondrial dysfunction and we show that Tctp interacts in the axonal compartment with myeloid cell leukemia 1 (Mcl1), a pro-survival member of the Bcl2 family. Mcl1 knockdown gives rise to similar axon misprojection phenotypes, and we provide evidence that the anti-apoptotic activity of Tctp is necessary for the normal development of the retinotectal projection. These findings suggest that Tctp supports the development of the retinotectal projection via its regulation of pro-survival signalling and axonal mitochondrial homeostasis, and establish a novel and fundamental role for Tctp in vertebrate neural circuitry assembly.

Highlighted article: The cancer-associated protein Tctp controls neural circuitry in Xenopus via its regulation of pro-survival signalling and axonal mitochondrial homeostasis.

Phospho-TCTP as a therapeutic target of Dihydroartemisinin for aggressive breast cancer cells

Upregulation of Translationally Controlled Tumor Protein (TCTP) is associated with poorly differentiated aggressive tumors, including breast cancer, but the underlying mechanism(s) are still debated. Here, we show that in breast cancer cell lines TCTP is primarily localized in the nucleus, mostly in the phosphorylated form.

The effects of Dihydroartemisinin (DHA), an anti-malaria agent that binds TCTP, were tested on breast cancer cells. DHA decreases cell proliferation and induces apoptotic cell death by targeting the phosphorylated form of TCTP. Remarkably, DHA enhances the anti-tumor effects of Doxorubicin in triple negative breast cancer cells resulting in an increased level of apoptosis. DHA also synergizes with Trastuzumab, used to treat HER2/neu positive breast cancers, to induce apoptosis of tumor cells.

Finally, we present new clinical data that nuclear phospho-TCTP overexpression in primary breast cancer tissue is associated with high histological grade, increase expression of Ki-67 and with ER-negative breast cancer subtypes. Notably, phospho-TCTP expression levels increase in trastuzumab-resistant breast tumors, suggesting a possible role of phospho-TCTP as a new prognostic marker.

In conclusion, the anti-tumor effect of DHA in vitro with conventional chemotherapeutics suggests a novel therapeutic strategy and identifies phospho-TCTP as a new promising target for advanced breast cancer.

RNA interference‑mediated knockdown of translationally controlled tumor protein induces apoptosis, and inhibits growth and invasion in glioma cells

Translationally controlled tumor protein (TCTP) is a highly conserved, growth-associated and small molecule protein, which is highly expressed in various types of tumor cell. TCTP can promote the growth and suppress apoptosis of tumor cels. However, few studies have reported the effects of TCTP in gliomas. In the present study, a glioma cell line was established, which was stably transfected with TCTP short hairpin ribonucleic acid (shRNA), to investigate the impact of downregulated expression of TCTP on the proliferation, apoptosis and invasion of glioma cells. Western blot and reverse transcription-quantitative polymerase chain reaction analyses demonstrated that TCTP shRNA effectively reduced the expression of TCTP in the U251 glioma cell line. MTT and colony formation assays revealed that downregulated expression of TCTP significantly inhibited glioma cell proliferation. Cell cycle analysis using flow cytometry revealed that the cells in the pRNA-H1.1-TCTP group were arrested in the G0/G1 phase of the cell cycle. Western blot analysis detected downregulated expression levels of cyclins, including Cyclin D1, Cyclin E and Cyclin B. Annexin V-fluorescein isothiocyanate/propidium iodide and Hoechst staining demonstrated that the apoptotic rate of the cells in the pRNA-H1.1-TCTP group was significantly higher than that of the cells in the pRNA-H1.1-control group, with upregulated expression levels of B-cell-associated X protein and cleaved-caspase-3 and downregulated expression of B-cell lmyphoma-2 in the apoptotic process. Wound healing and Transwell assays revealed that downregulated expression of TCTP significantly inhibited the migration and invasiveness of the glioma cells; and the expression levels and activities of matrix metalloproteinase (MMP)-2 and MMP-9 were also significantly affected. In conclusion, the present study demonstrated that downregulated expression of TCTP significantly inhibited proliferation and invasion, and induced apoptosis in the glioma cells. These results suggested that TCTP may be important in glioma development and metastasis. Therefore, TCTP is expected to become an effective target for glioma gene therapy.

Growth-factor dependent expression of the translationally controlled tumour protein TCTP is regulated through the PI3-K/Akt/mTORC1 signalling pathway

Translationally controlled tumour protein TCTP (gene symbol: TPT1) is a highly-conserved, cyto-protective protein implicated in many physiological and disease processes, in particular cancer, where it is associated with poor patient outcomes. To understand the mechanisms underlying the accumulation of high TCTP levels in cancer cells, we studied the signalling pathways that control translation of TCTP mRNA, which contains a 5'-terminal oligopyrimidine tract (5'-TOP). In HT29 colon cancer cells and in HeLa cells, serum increases the expression of TCTP two- and four-fold, respectively, and this is inhibited by rapamycin or mTOR kinase inhibitors. Polysome profiling and mRNA quantification indicate that these effects occur at the level of mRNA translation. Blocking this pathway upstream of mTOR complex 1 (mTORC1) by inhibiting Akt also prevented increases in TCTP levels in both HeLa and HT29 colon cancer cells, whereas knockout of TSC2, a negative regulator of mTORC1, led to derepression of TCTP synthesis under serum starvation. Overexpression of eIF4E enhanced the polysomal association of the TCTP mRNA, although it did not protect its translation from inhibition by rapamycin. Conversely, expression of a constitutively-active mutant of the eIF4E inhibitor 4E-BP1, which is normally inactivated by mTORC1, inhibited TCTP mRNA translation in HEK293 cells. Our results demonstrate that TCTP mRNA translation is regulated by signalling through the PI3-K/Akt/mTORC1 pathway. This explains why TCTP levels are frequently increased in cancers, since mTORC1 signalling is hyperactive in ~80% of tumours.

CUSP9* treatment protocol for recurrent glioblastoma: aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, ritonavir, sertraline augmenting continuous low dose temozolomide

CUSP9 treatment protocol for recurrent glioblastoma was published one year ago. We now present a slight modification, designated CUSP9*. CUSP9* drugs--aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, sertraline, ritonavir, are all widely approved by regulatory authorities, marketed for non-cancer indications. Each drug inhibits one or more important growth-enhancing pathways used by glioblastoma. By blocking survival paths, the aim is to render temozolomide, the current standard cytotoxic drug used in primary glioblastoma treatment, more effective. Although esthetically unpleasing to use so many drugs at once, the closely similar drugs of the original CUSP9 used together have been well-tolerated when given on a compassionate-use basis in the cases that have come to our attention so far. We expect similarly good tolerability for CUSP9*. The combined action of this suite of drugs blocks signaling at, or the activity of, AKT phosphorylation, aldehyde dehydrogenase, angiotensin converting enzyme, carbonic anhydrase -2,- 9, -12, cyclooxygenase-1 and -2, cathepsin B, Hedgehog, interleukin-6, 5-lipoxygenase, matrix metalloproteinase -2 and -9, mammalian target of rapamycin, neurokinin-1, p-gp efflux pump, thioredoxin reductase, tissue factor, 20 kDa translationally controlled tumor protein, and vascular endothelial growth factor. We believe that given the current prognosis after a glioblastoma has recurred, a trial of CUSP9* is warranted.

Expression and clinical role of TCTP in epithelial ovarian cancer

The aim of this study is to investigate the potential role and prognostic significance of translationally controlled tumor protein (TCTP) in human epithelial ovarian cancer (EOC). Western blot was used to evaluate the expression of TCTP in eight fresh EOC tissues. Immunohistochemistry was performed on formalin-fixed paraffin-embedded sections of 119 cases of ovarian cancers. Kaplan-Meier method indicated the relation between TCTP and EOC patients' overall survival rate. Starvation and re-feeding was used to assess cell cycle. Knocking down of TCTP and CCK8 assay showed the role of TCTP in HO8910 cell cycle. We found that TCTP was overexpressed in carcinoma tissues compared with normal tissues. Immunohistochemistry revealed that TCTP expression was significantly associated with clinicopathologic variables. Kaplan-Meier analysis revealed that high TCTP expression was significantly related to poor prognosis of the patients. Starvation and re-feeding suggested TCTP played a critical role in HO8910 cell proliferation. Interference of TCTP and CCK8 assay showed that the TCTP-siRNA treated HO8910 cells grew more slowly than the control group. CCK-8 assays and terminal-deoxynucleoitidyl transferase mediated nick end labeling assays were also performed to demonstrate the cisplatin could inhibit the survival of HO8910 cells and promote their apoptosis. All the experiments we have done showed that TCTP could promote the progression of EOC and reduce the sensitiveness of HO8910 cells to cisplatin.

Comparative proteomics analysis of global cellular stress responses to hydroxyurea-induced DNA damage in HeLa cells

Both environmental agents and spontaneous cellular events cause serious DNA damage, threatening the integrity of the genome. In response to replication stress or genotoxic agents triggered DNA damage, degradation of p12 subunit of DNA polymerase delta (Pol δ) results in an inter-conversion between heterotetramer (Pol δ4) and heterotrimer (Pol δ3) forms and plays a significant role in DNA damage response in eukaryotic cells. In this work, we used mass spectrometry-based proteomic approach to identify those cellular stress response protein changes corresponding to the degradation of p12 in DNA-damaged HeLa cells by the treatment with hydroxyurea (HU). A total of 736 ± 13 proteins in non-treated control group and 741 ± 19 protein spots in HU-treated cells were detected, of which 34 proteins (17 up-regulated and 17 down-regulated) exhibited significantly altered protein expression levels. Their physiological roles are mainly associated with cellular components, molecular functions, and biological processes by gene ontology analysis, among which 21 proteins were mapped to KEGG pathways. They are involved in 5 primary pathways with the subsets involving 16 secondary pathways by further KEGG analysis. More interestingly, the up-regulation of translationally controlled tumor protein was further identified to be associated with p12 degradation by Western blot analysis. Our works may enlarge and broaden our view for deeply understanding how global cellular stress responds to DNA damage, which could contribute to the etiology of human cancer or other diseases that can result from loss of genomic stability.

TCTP as therapeutic target in cancers

The translationally controlled tumor protein (TCTP) is a highly conserved protein present in eukaryotic organisms. This protein, located both in the cytoplasmic and the nucleus, is expressed in various tissues and is regulated in response to a wide range of extracellular stimuli. TCTP interacts with itself and other protein including MCL1 and p53. TCTP has been shown to play an important role in physiological events, such as cell proliferation, cell death and immune responses but also in stress response and tumor reversion. Moreover, TCTP expression is associated with malignancy and chemoresistance. In this review, we will evaluate pathways regulated by TCTP and current inhibitory strategy to target TCTP in cancerous diseases.