Tumor Protein 53-induced Nuclear Protein 1 Research Articles

MircoRNA-29a in Astrocyte-derived Extracellular Vesicles Suppresses Brain Ischemia Reperfusion Injury via TP53INP1 and the NF-κB/NLRP3 Axis.

Brain ischemia reperfusion injury (BIRI) is defined as a series of brain injury accompanied by inflammation and oxidative stress. Astrocyte-derived extracellular vesicles (EVs) are importantly participated in BIRI with involvement of microRNAs (miRs). Our study aimed to discuss the functions of miR-29a from astrocyte-derived EVs in BIRI treatment. Thus, astrocyte-derived EVs were extracted. Oxygen and glucose deprivation (OGD) cell models and BIR rat models were established. Then, cell and rat activities and pyroptosis-related protein levels in these two kinds of models were detected. Functional assays were performed to verify inflammation and oxidative stress. miR-29a expression in OGD cells and BIR rats was measured, and target relation between miR-29a and tumor protein 53-induced nuclear protein 1 (TP53INP1) was certified. Rat neural function was tested. Astrocyte-derived EVs improved miR-29a expression in N9 microglia and rat brains. Astrocyte-derived EVs inhibited OGD-induced injury and inflammation in vitro, reduced brain infarction, and improved BIR rat neural functions in vivo. miR-29a in EVs protected OGD-treated cells and targeted TP53INP1, whose overexpression suppressed the protective function of EVs on OGD-treated cells. miR-29a alleviated OGD and BIRI via downregulating TP53INP1 and the NF-κB/NLRP3 pathway. Briefly, our study demonstrated that miR-29a in astrocyte-derived EVs inhibits BIRI by downregulating TP53INP1 and the NF-κB/NLRP3 axis.

Tumor protein 53-induced nuclear protein 1 deficiency alters mouse gastrocnemius muscle function and bioenergetics invivo.

Tumor protein 53‐induced nuclear protein 1 (TP53INP1) deficiency leads to oxidative stress‐associated obesity and insulin resistance. Although skeletal muscle has a predominant role in the development of metabolic syndrome, the bioenergetics and functional consequences of TP53INP1 deficiency upon this tissue remain undocumented. To clarify this issue, gastrocnemius muscle mechanical performance, energy metabolism, and anatomy were investigated in TP53INP1‐deficient and wild‐type mice using a multidisciplinary approach implementing noninvasive multimodal‐NMR techniques. TP53INP1 deficiency increased body adiposity but did not affect cytosolic oxidative stress, lipid content, and mitochondrial pool and capacity in myocyte. During a fatiguing bout of exercise, the in vivo oxidative ATP synthesis capacity was dramatically reduced in TP53INP1‐deficient mice despite ADP level (the main in vivo stimulator of mitochondrial respiration) did not differ between both genotypes. Moreover, TP53INP1 deficiency did not alter fatigue resistance but paradoxically increased the contractile force, whereas there were no differences for muscle fiber‐type distribution and calcium homeostasis between both genotypes. In addition, muscle proton efflux was decreased in TP53INP1‐deficient mice, thereby indicating a reduced blood supply. In conclusion, TP53INP1 plays a role in muscle function and bioenergetics through oxidative capacity impairment possibly as the consequence of abnormal mitochondrial respiration regulation and/or defective blood supply.

Prognostic impact of TP53INP1 gene expression in estrogen receptor α-positive breast cancer patients.

Tumor protein 53-induced nuclear protein 1 (TP53INP1) is a key stress protein with tumor suppressor function. Several studies have demonstrated TP53INP1 downregulation in many cancers. In this study, we investigated the correlations of TP53INP1 mRNA expression in breast cancer tissues with prognosis and the correlations of microRNAs that regulate TP53INP1 expression in breast cancer patients with long follow-up. A total of 453 invasive breast cancer tissues were analyzed for TP53INP1 mRNA expression. We examined correlations of clinicopathological factors and expression levels of TP53INP1 mRNA in these samples. The expressions of miR-155, miR-569 and markers associated with tumor-initiating capacity were also analyzed. The median follow-up period was 9.0 years. We found positive correlations between low expression of TP53INP1 mRNA and shorter disease-free survival and overall survival in breast cancer patients (P = 0.0002 and P < 0.0001, respectively), as well as in estrogen receptor α (ERα)-positive patients receiving adjuvant endocrine therapy (P = 0.01 and P = 0.0008, respectively). No correlations were found in ERα-negative patients. Low TP53INP1 mRNA levels positively correlated with higher grade and ERα-negativity. Multivariate analysis indicated that TP53INP1 mRNA level was an independent risk factor for overall survival both in overall breast cancer patients (hazard ratio, 2.13; 95% confidence interval, 1.17-3.92) and ERα-positive patients (hazard ratio, 2.34; 95% confidence interval, 1.18-4.64). We show that low expression of TP53INP1 is an independent factor of poor prognosis in breast cancer patients, especially ERα-positive patients. TP53INP1 might be a promising candidate biomarker and therapeutic target in ERα-positive breast cancer patients.

NT21MP negatively regulates paclitaxel-resistant cells by targeting miR‑155‑3p and miR‑155-5p via the CXCR4 pathway in breast cancer.

Evidence has shown that microRNAs (miRNAs) are vital in cell growth, migration, and invasion by inhibiting their target genes. A previous study demonstrated that miRNA (miR)-155-3p and miR-155-5p exerted opposite effects on cell proliferation, apoptosis, migration and invasion in breast cancer cell lines. An miRNA microarray was used to show that miR-155-3p was downregulated whereas miR-155-5p was upregulated in paclitaxel-resistant (PR) cells compared with parental breast cancer cells. However, the role of miR-155 in breast cancer cell invasion and metastasis remains to be elucidated. A 21-residue peptide derived from the viral macrophage inflammatory protein II (NT21MP), competes with the ligand of CXC chemokine receptor 4 (CXCR4) and its ligand stromal cell-derived factor-1α, inducing cell apoptosis in breast cancer. The present study aimed to identify the underlying mechanism of action of miR-155-3p/5p and NT21MP in PR breast cancer cells. Quantitative polymerase chain reaction, western blotting, wound-healing, cell cycle and apoptosis assays, and Cell Counting kit-8 assay were used to achieve this goal. The combined overexpression of miR-155-3p with NT21MP decreased the migration and invasion ability and increased the number of apoptotic and arrested cells in the G0/G1 phase transition in vitro. The knockdown of miR-155-5p combined with NT21MP had a similar effect on PR breast cancer cells. Furthermore, the ectopic expression of their target gene myeloid differentiation primary response gene 88 (MYD88) or tumor protein 53-induced nuclear protein 1 (TP53INP1) combined with NT21MP enhanced the sensitivity of the breast cancer cells to paclitaxel. Taken together, these findings suggested that miR-155-3p/5p and their target genes MYD88 and TP53INP1 may serve as novel biomarkers for NT21MP therapy through the CXCR4 pathway for improving sensitivity to paclitaxel in breast cancer.

MiR-221 inhibits autophagy and targets TP53INP1 in colorectal cancer cells.

Colorectal cancer (CRC) is the third most common cancer and the fourth leading cause of cancer-associated mortalities worldwide. MicroRNAs (miRNAs/miRs) serve important roles in tumor development, progression and metastasis. miR-221 has been reported to modulate proliferation, apoptosis, cell cycle distribution and cell migration in a variety of cancers. However, the function of miR-221 in the autophagy of cancer is unclear. In the present study, the role of miR-221 in the autophagy of CRC cells was investigated and its associated target was identified. Survival analysis using The Cancer Genome Atlas data suggested that a higher expression of miR-221 was associated with poor survival in patients with CRC. A Cell Counting kit-8 assay revealed that miR-221 promoted CRC cell proliferation. Autophagy flux analyzed by microtubule-associated protein 1 light chain 3 (LC3) turnover indicated that miR-221 reduced autophagy in CRC cells using different protease inhibitors (E64d and pepstatin A; Bafilomycin A1) in nutrient-rich medium or under starvation conditions. Tumor protein 53-induced nuclear protein 1 (TP53INP1) was identified as a potential novel target of miR-221 by bioinformative prediction. The protein expression of TP53INP1 was inversely regulated by miR-221 in CRC cells. Furthermore, luciferase activity assays were performed and indicated that miR-221 may regulate the luciferase activity of wild-type TP53INP1 without interfering with the activity of mutant TP53INP1. These data suggested that miR-221 may promote the cell proliferation of CRC via the inhibition of autophagy and targeted TP53INP1.

TP53inp1 Gene Is Implicated in Early Radiation Response in Human Fibroblast Cells.

Tumor protein 53-induced nuclear protein-1 (TP53inp1) is expressed by activation via p53 and p73. The purpose of our study was to investigate the role of TP53inp1 in response of fibroblasts to ionizing radiation. γ-Ray radiation dose-dependently induces the expression of TP53inp1 in human immortalized fibroblast (F11hT) cells. Stable silencing of TP53inp1 was done via lentiviral transfection of shRNA in F11hT cells. After irradiation the clonogenic survival of TP53inp1 knockdown (F11hT-shTP) cells was compared to cells transfected with non-targeting (NT) shRNA. Radiation-induced senescence was measured by SA-β-Gal staining and autophagy was detected by Acridine Orange dye and microtubule-associated protein-1 light chain 3 (LC3B) immunostaining. The expression of TP53inp1, GDF-15, and CDKN1A and alterations in radiation induced mitochondrial DNA deletions were evaluated by qPCR. TP53inp1 was required for radiation (IR) induced maximal elevation of CDKN1A and GDF-15 expressions. Mitochondrial DNA deletions were increased and autophagy was deregulated following irradiation in the absence of TP53inp1. Finally, we showed that silencing of TP53inp1 enhances the radiation sensitivity of fibroblast cells. These data suggest functional roles for TP53inp1 in radiation-induced autophagy and survival. Taken together, we suppose that silencing of TP53inp1 leads radiation induced autophagy impairment and induces accumulation of damaged mitochondria in primary human fibroblasts.

MicroRNA-125b promotes tumor metastasis through targeting tumor protein 53-induced nuclear protein 1 in patients with non-small-cell lung cancer

BackgroundLung cancer, predominantly non-small-cell lung cancer (NSCLC), is the leading cause of cancer deaths worldwide. There is a great need to identify critical effectors involved in metastasis of NSCLC that will facilitate the development of new therapeutic strategies. Here we evaluated the potential role of miR-125b in the metastasis of NSCLC cells.MethodsHuman NSCLC cells were isolated from surgical tissues with Cancer Cell Isolation Kit. Expressions of miR-125b and TP53INP1 were detected with real-time PCR and western blot. Human miR-125b mimics, miR-125b inhibitor, TP53INP1 expression plasmid and TP53INP1 siRNA were transfected into NSCLC cells with nucleofector transfection kit. NSCLC metastasis was determined with adhesion assay, invasive assay and lung tumor metastasis model.ResultsThe expression of miR-125b was significantly higher in poorly differentiated NSCLC cells that are endowed with high metastatic potentials. Up-regulation of miR-125b could enhance the metastatic potential of NSCLC cells in vitro and in vivo, while down-regulation of miR-125b resulted in decreased metastatic potentials in vitro and in vivo. Further, tumor protein 53-induced nuclear protein 1 (TP53INP1) was an important target of miR-125b involved in metastasis of NSCLC cells. TP53INP1 served as a negative regulator of NSCLC metastasis. Decreased expression of TP53INP1 in tumor tissues was inversely associated with their expression of miR-125b, significantly lower in poorly differentiated tumors and inversely correlated with the clinical stages in patients with NSCLC.ConclusionsThese findings demonstrated that miR-125b promoted tumor metastasis via targeting TP53INP1 in human NSCLC cells, which uncovered a real clinical relevance of microRNAs in tumor biology, and provided novel potential candidates for NSCLC clinical practice.Electronic supplementary materialThe online version of this article (doi:10.1186/s12935-015-0233-x) contains supplementary material, which is available to authorized users.

The stress protein TP53INP1 plays a tumor suppressive role by regulating metabolic homeostasis.

In the recent years, we have provided evidence that Tumor Protein 53-Induced Nuclear Protein 1 (TP53INP1) is a key stress protein with antioxidant-associated tumor suppressive function. The TP53INP1 gene, which is highly conserved in mammals, is over-expressed during stress responses including inflammation. This gene encodes two protein isoforms with nuclear or cytoplasmic subcellular localization depending on the context. TP53INP1 contributes to stress responses, thus preventing stress-induced dysfunctions leading to pathologies such as cancer. Two major mechanisms by which TP53INP1 functions have been unveiled. First, in the nucleus, TP53INP1 was shown to regulate the transcriptional activity of p53 and p73 by direct interaction, and to mediate the antioxidant activity of p53. Second, independently of p53, TP53INP1 contributes to autophagy and more particularly mitophagy through direct interaction with molecular actors of autophagy. TP53INP1 is thus required for the homeostasis of the mitochondrial compartment, and is therefore involved in the regulation of energetic metabolism. Finally, the antioxidant function of TP53INP1 stems from the control of mitochondrial reactive oxygen species production. In conclusion, TP53INP1 is a multifaceted protein endowed with multiple functions, including metabolic regulation, as is its main functional partner p53.

Abstract 5138: Histone deacetylase 2 and N-Myc reduce p53 protein phosphorylation at serine 46 by repressing gene transcription of tumor protein 53-induced nuclear protein 1

Abstract Myc oncoproteins and histone deacetylases (HDACs) exert oncogenic effects by modulating gene transcription. Paradoxically, N-Myc induces p53 gene expression. Tumor protein 53-induced nuclear protein 1 (TP53INP1) phosphorylates p53 protein at serine 46, leading to enhanced p53 activity, transcriptional activation of p53 target genes and programmed cell death. We aimed to identify the mechanism through which N-Myc overexpressing p53 wild-type neuroblastoma cells acquired resistance to apoptosis.Gene and protein expression was analysed by real-time RT-PCR and immunoblot. Cell survival/death was examined by flow cytometry study of Annexin V-staining. The prognostic value of TP53INP1 expression in tumor tissues was investigated in three independent cohorts of neuroblastoma patients. TP53INP1 was one of the genes most significantly repressed by HDAC2 and N-Myc according to Affymetrix microarray gene expression datasets. HDAC2 and N-Myc reduced TP53INP1 gene expression by direct binding to the TP53INP1 gene promoter, leading to transcriptional repression of TP53INP1, p53 protein de-phosphorylation at serine 46, neuroblastoma cell proliferation and survival. Moreover, low levels of TP53INP1 expression in human neuroblastoma tissues correlated with high levels of N-Myc expression and poor patient outcome, and the BET bromodomain inhibitors JQ1 and I-BET151 reduced N-Myc expression and reactivated TP53INP1 expression in neuroblastoma cells. These findings identify TP53INP1 repression as an important co-factor for N-Myc oncogenesis, and provide further evidence for the potential application of BET bromodomain inhibitors in the therapy of N-Myc-induced neuroblastoma. Citation Format: Jeyran Shahbazi, Christopher J. Scarlett, Murray Norris, Bing Liu, Michelle Haber, Andrew E. Tee, Alice Carrier, Andrew V. Biankin, Wendy B. London, Glenn M. Marshall, Richard Lock, Tao Liu. Histone deacetylase 2 and N-Myc reduce p53 protein phosphorylation at serine 46 by repressing gene transcription of tumor protein 53-induced nuclear protein 1. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5138. doi:10.1158/1538-7445.AM2014-5138

Histone deacetylase 2 and N-Myc reduce p53 protein phosphorylation at serine 46 by repressing gene transcription of tumor protein 53-induced nuclear protein 1.

Myc oncoproteins and histone deacetylases (HDACs) exert oncogenic effects by modulating gene transcription. Paradoxically, N-Myc induces p53 gene expression. Tumor protein 53-induced nuclear protein 1 (TP53INP1) phosphorylates p53 protein at serine 46, leading to enhanced p53 activity, transcriptional activation of p53 target genes and programmed cell death. Here we aimed to identify the mechanism through which N-Myc overexpressing p53 wild-type neuroblastoma cells acquired resistance to apoptosis. TP53INP1 was found to be one of the genes most significantly repressed by HDAC2 and N-Myc according to Affymetrix microarray gene expression datasets. HDAC2 and N-Myc reduced TP53INP1 gene expression by direct binding to the TP53INP1 gene promoter, leading to transcriptional repression of TP53INP1, p53 protein de-phosphorylation at serine 46, neuroblastoma cell proliferation and survival. Moreover, low levels of TP53INP1 expression in human neuroblastoma tissues correlated with high levels of N-Myc expression and poor patient outcome, and the BET bromodomain inhibitors JQ1 and I-BET151 reduced N-Myc expression and reactivated TP53INP1 expression in neuroblastoma cells. These findings identify TP53INP1 repression as an important co-factor for N-Myc oncogenesis, and provide further evidence for the potential application of BET bromodomain inhibitors in the therapy of N-Myc-induced neuroblastoma.

Upregulated miR-182 increases drug resistance in cisplatin-treated HCC cell by regulating TP53INP1

Chemotherapy plays a crucial role in hepatocellular carcinoma (HCC) treatment especially for patients with advanced HCC. Cisplatin is one of the commonly used chemotherapeutic drugs for the treatment of HCC. However, acquisition of cisplatin resistance is common in patients with HCC, and the underlying mechanism of such resistance is not fully understood. In the study, we focused on identifying the role of miRNAs in chemotherapy resistance after cisplatin-based combination chemotherapy. We assayed the expression level of miR-182 after cisplatin-based chemotherapy in patients with advanced HCC, and defined the biological functions by real-time PCR analysis and CCK-8 assay. We found that miR-182 levels were significantly increased in HCC patients treated with cisplatin-based chemotherapy. miR-182 levels were also higher in cisplatin-resistant HepG2 (HepG2-R) cells than in HepG2 cells. Upregulated miR-182 significantly increased the cell viability, whereas miR-182 knockdown reduced the cell viability during cisplatin treatment. miR-182 inhibition also partially overcame cisplatin resistance in HepG2-R cell. Furthermore, we found that upregulated miR-182 inhibited the expression of tumor suppressor gene TP53INP1 (tumor protein 53-induced nuclear protein1) in vitro. In vivo, miR-182 and TP53INP1 expression was negatively correlated. We finally demonstrated that miR-182 increased cisplatin resistance of HCC cell, partly by targeting TP53INP1. These data suggest that miR-182/TP53INP1 signaling represents a novel pathway regulating chemoresistance, thus offering a new target for chemotherapy of HCC.

MiR-155 promotes proliferation of human breast cancer MCF-7 cells through targeting tumor protein 53-induced nuclear protein 1

BackgroundMiR-155 has emerged as an “oncomiR”, which is the most significantly up-regulated miRNA in breast cancer. However, the mechanisms of miR-155 functions as an oncomiR are mainly unknown. In this study, the aims were to investigate the effects of miR-155 on cell proliferation, cell cycle, and cell apoptosis of ERalpha (+) breast cancer cells and to verify whether TP53INP1 (tumor protein 53-induced nuclear protein 1) is a target of miR-155, and tried to explore the mechanisms of miR-155 in this process.ResultsThe expression of miR-155 is significantly higher in MCF-7 cells compared with MDA-MB-231 cells. Ectopic expression of TP53INP1 inhibits growth of MCF-7 cells by inducing cell apoptosis and inhibiting cell cycle progression. Overexpression of miR-155 increases cell proliferation and suppress cell apoptosis, whereas abrogating expression of miR-155 suppress cell proliferation and promotes cell apoptosis of MCF-7 cells. In addition, miR-155 negatively regulates TP53INP1 mRNA expression and the protein expression of TP53INP1, cleaved-caspase-3, -8, -9, and p21, and luciferase reporter reveals that TP53INP1 is targeted by miR-155.ConclusionsTP53INP1 is the direct target of miR-155. MiR-155, which is overexpressed in MCF-7 cells, contributes to proliferation of MCF-7 cells possibly through down-regulating target TP53INP1.

Development of an ELISA detecting Tumor Protein 53-Induced Nuclear Protein 1 in serum of prostate cancer patients

Tumor Protein 53-Induced Nuclear Protein 1 (TP53INP1) plays an important role during cell stress response in synergy with the potent “genome-keeper” p53. In human, the gene encoding TP53INP1 is expressed at very high level in some pathological situations, such as inflammation and prostate cancer (PC). TP53INP1 overexpression in PC seems to be a worse prognostic factor, particularly predictive of biological cancer relapse, making TP53INP1 a relevant specific target for molecular therapy of Castration Resistant (CR) PC. In that context, detection of TP53INP1 in patient biological fluids is a promising diagnostic avenue. We report here successful development of a new Enzyme-Linked Immunosorbent Assay (ELISA) detecting TP53INP1, taking advantage of molecular tools (monoclonal antibodies (mAbs) and recombinant proteins) generated in the laboratory during the course of basic functional investigations devoted to TP53INP1. The ELISA principle is based on a sandwich immunoenzymatic system, TP53INP1 protein being trapped by a first specific mAb coated on microplate then recognized by a second specific mAb. This new assay allows specific detection of TP53INP1 in serum of several PC patients. This breakthrough paves the way towards investigation of a large cohort of patients and assessment of clinical applications of TP53INP1 dosage.

Tumor Protein 53-Induced Nuclear Protein 1 Enhances p53 Function and Represses Tumorigenesis

Tumor protein 53-induced nuclear protein 1 (TP53INP1) is a stress-induced p53-target gene whose expression is modulated by transcription factors such as p53, p73, and E2F1. TP53INP1 gene encodes two isoforms of TP53INP1 proteins, TP53INP1α and TP53INP1β, both of which appear to be key elements in p53 function. In association with homeodomain-interacting protein kinase-2 (HIPK2), TP53INP1 phosphorylates p53 protein at Serine-46. This enhances p53 protein stability and its transcriptional activity, leading to transcriptional activation of p53-target genes such as p21 and PIG3, cell growth arrest and apoptosis upon DNA damage stress. The anti-proliferative and pro-apoptotic activities of TP53INP1 indicate that TP53INP1 has an important role in cellular homeostasis and DNA damage response. Deficiency in TP53INP1 expression results in increased tumorigenesis, whereas TP53INP1 expression is repressed during early stages of cancer by factors such as miR-155. This review aims to summarize the roles of TP53INP1 in blocking tumor progression through p53-dependant and p53-independent pathways, as well as the elements which repress TP53INP1 expression, hence highlighting its potential as a therapeutic target in cancer treatment.

Abstract P5-10-03: OncomiR-569 deregulate p53 pathway and initiate breast oncogenesis

Abstract Background: The 3q26.2 chromosomal loci is highly amplified in large set of breast cancers, primarily in aggressive basal tumors are difficult to treat in the clinic. Our amplicon data suggests that 3q26.2 is a large structurally complex amplicon and multiple components in the amplicon contribute to tumor initiation and progression either alone or through cooperative activity. Detailed mapping of the 3q26.2 amplicon by us demonstrated a microRNA, miR569 is highly amplified as a part of 3q26.2 amplicon in breast cancer patient's samples. The role of microRNAs amplified at 3q26 loci is not well studied and their molecular functions and targets were not well known. Thus our studies provide novel mechanism underlying miR569 oncogenesis. Methods: Following the Institutional Review Board approval, tissues obtained from MD Anderson Cancer Center tumor bank were used to exatract DNA and RNA. Human miR-569 was cloned into pEZX-MR06 lentiviral vector used for the production of amphotropic viruses to infect the target cells. The miRIDIAN microRNA mimics were used to overexpress miRs and the antimiRs were used to knock down the miRNAs. All the transfections were performed using Oligofectamine. Trypsinized cells were grown in 5% matrigel for the 3D morphogenesis of epithelial cells. Results: Our results demonstrated a strong correlation between 3q26.2 amplification and expression of miR569 in patient samples of breast cancer. We subsequently demonstrated that overexpression and knockdown of miR569 in the breast epithelial cells altered their growth, proliferation, and lumen filling in 3-dimensional cultures grown in Matrigel. Importantly ectopic expression of miR569 in breast epithelial cells promoted tumor growth and increased metastatic potential in mouse xenograft models. Seed match based analysis of the microRNA targets, in silico studies and in vitro experiments showed that miR-569 directly target Tumor protein 53-induced nuclear protein1 (TP53INP1) and inhibited the expression of a tumor suppressor gene TP53INP1 expression. Loss of TP53INP1 expression mediated by miR569 altered normal cell growth cycle and subsequently promoted the survival and growth of tumor cells. Our in vitro results showed that knockdown of miR-569 and subsequent increase in TP53INP1 expression enhanced the sensitivity of cancer cell lines to cisplatin. Our immunohistochemical analysis showed that TP53INP1 protein levels were higher in normal tissues compared to cancer tissues. Further, reduced expression of TP53INP1 was observed in invasive cancers as compared to low malignant potential tumors, and decreased TP53INP1 protein levels were associated with worsened outcomes in breast cancer patients. Disscussion: TP53INP1 had previously been identified as a combined target of p53 and p73; however our studies indicate that miR-569 regulates TP53INP1 levels independently of p53 and p73 expression. Based on our preclinical results of antimiR-569 on cell survival, tumor growth and cisplatin sensitivity, inhibiting miR-569 activity or increasing TP53INP1 expression may be valid therapeutic approaches to treat breast cancer. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-10-03.

Meaning of tumor protein 53-induced nuclear protein 1 in the molecular mechanism of gemcitabine sensitivity

Stress proteins of the pancreas, such as tumor protein 53-induced nuclear protein 1 (TP53INP1), are important factors in the invasion and metastasis of pancreatic cancer. TP53INP1 is a pro-apoptotic factor and is transcriptionally regulated in p53-dependent and -independent manners. A previous study proved that gemcitabine induces TP53INP1 expression in pancreatic cancer cells and the pancreatic cancer cell line (PANC-1). The present study aimed to clarify the association between TP53INP1 and gemcitabine sensitivity. The expression of TP53INP1 and its related factors, such as cell growth and cell cycle status in TP53INP1-knockout mouse embryonic fibroblasts [TP53INP1-/--mouse embryonic fibroblasts (MEFs)] to those in wild-type counterparts (TP53INP1+/+-MEFs) were compared. Flow cytometric analysis demonstrated no difference of the checkpoint function in TP53INP1-/--MEFs and TP53INP1+/+-MEFs when exposed to 10 ng/ml of gemcitabine. No significant difference was found in the level of p53 expression in the cell types, although the base level and gemcitabine-induced expression of p21 were significantly decreased in TP53INP1-/--MEFs, compared to those in wild-type counterparts. Results showed that gemcitabine induced the p21 expression in TP53INP1+/+-MEFs, although not in TP53INP1-/--MEFs. However, their respective cell-cycle checkpoints were not different. Therefore, TP53INP1 was found to be associated with drug sensitivity through control of the cell cycle.

TP53INP1, a tumor suppressor, interacts with LC3 and ATG8-family proteins through the LC3-interacting region (LIR) and promotes autophagy-dependent cell death

TP53INP1 (tumor protein 53-induced nuclear protein 1) is a tumor suppressor, whose expression is downregulated in cancers from different organs. It was described as a p53 target gene involved in cell death, cell-cycle arrest and cellular migration. In this work, we show that TP53INP1 is also able to interact with ATG8-family proteins and to induce autophagy-dependent cell death. In agreement with this finding, we observe that TP53INP1, which is mainly nuclear, relocalizes in autophagosomes during autophagy where it is eventually degraded. TP53INP1-LC3 interaction occurs via a functional LC3-interacting region (LIR). Inactivating mutations of this sequence abolish TP53INP1-LC3 interaction, relocalize TP53INP1 in autophagosomes and decrease TP53INP1 ability to trigger cell death. Interestingly, TP53INP1 binds to ATG8-family proteins with higher affinity than p62, suggesting that it could partially displace p62 from autophagosomes, modifying thereby their composition. Moreover, silencing the expression of autophagy related genes (ATG5 or Beclin-1) or inhibiting caspase activity significantly decreases cell death induced by TP53INP1. These data indicate that cell death observed after TP53INP1-LC3 interaction depends on both autophagy and caspase activity. We conclude that TP53INP1 could act as a tumor suppressor by inducing cell death by caspase-dependent autophagy.

TP53INP1 as new therapeutic target in castration‐resistant prostate cancer

Prostate cancer (PC) is one of the most common malignancies in industrialized countries, and the second leading cause of cancer-related death in the United States. We recently showed that over-expression of tumor protein 53-induced nuclear protein 1 (TP53INP1), a cell stress response protein, is a worse prognostic factor in PC, particularly predictive of biological cancer relapse. Moreover, treatment of castration-sensitive (CS) LNCaP tumor cells with a TP53INP1 antisense oligonucleotide (TP53INP1 ASO) inhibits proliferation and induces apoptosis. The aim of this study was to investigate variations of TP53INP1 expression in PC during androgen withdrawal therapy and in castration-resistant prostate cancer (CRPC). Quantitative measurements of immunohistochemical expression of TP53INP1 using high-throughput densitometry, assessed on digitized microscopic tissue micro-array images were correlated with hormone therapy (HT) status in human PC. Northern blot analysis of TP53INP1 after castration was performed in LNCaP xenograft. Treatment of CR C4-2 tumor cells in vitro with TP53INP1 ASO was analyzed. We also analyzed the effect of TP53INP1 ASO treatment in vivo on tumor xenograft growth. TP53INP1 protein expression decreases during HT and increases after HT in human CRPC. TP53INP1 mRNA increases significantly in CR tumors of LNCaP xenograft. Moreover, treatment of CR C4-2 cells with TP53INP1 ASO downregulates TP53INP1 protein level, inhibits proliferation, and induces apoptosis. Finally, in vivo, TP53INP1 ASO treatment significantly inhibits the tumoral progression of CR C4-2 xenograft and enhances docetaxel cytotoxicity. These results suggest that TP53INP1 could be considered as a relevant-specific target for molecular therapy of CRPC.

MiR-125b promotes proliferation and migration of type II endometrial carcinoma cells through targeting TP53INP1 tumor suppressor in vitro and in vivo

BackgroundOur previous studies have identified that miR-125b was overexpressed in type II endometrial carcinoma (EC) cells compared with type I using microRNAs microarray. Although recent studies have shown the important role of miR-125b in several tumors and overexpression of miR-125b in advanced EC, its function in this disease has not yet been defined. In the present study, we tried to confirm the result of microRNAs microarray and further investigated the functions of miR-125b in EC, and tried to find new downstream targets of miR-125b.MethodsDifferential expression of miR-125b was detected between type II EC cells (KLE, AN3CA) with ER negative and type I EC cells (ishikawa, RL95-2) with ER positive by qRT-PCR and northern blotting. The effects of miR-125b of on proliferation, migration, and target protein expression were evaluated by CCK8 assay, wound healing assay, transwell migration assay, western blotting, and Tumorigenicity assays in nude mice. In addition, luciferase reporter plasmid was constructed to demonstrate the direct target of miR-125b.ResultsMiR-125b was overexpressed in type II EC cells compared with type I. Exogenous miR-125b expression increased proliferation and migration of ishikawa cells and abrogating expression of miR-125b suppressed proliferation, and migration of AN3CA cells in vitro. In addition, in vivo tumor formation assay confirmed that forced miR-125b expression promoted proliferation potential of ishikawa cells, and tumor suppressor gene Tumor Protein 53-Induced Nuclear Protein 1 (TP53INP1) was identified to be the direct target of miR-125b.ConclusionsTP53INP1 was newly identified to be the direct downstream target of miR-125b. MiR-125b, which was overexpressed in type II EC cells compared with type I, contributes to malignancy of type II EC possibly through down-regulating TP53INP1.

Absence of Tumor Suppressor Tumor Protein 53-Induced Nuclear Protein 1 (TP53INP1) Sensitizes Mouse Thymocytes and Embryonic Fibroblasts to Redox-Driven Apoptosis

The p53-transcriptional target TP53INP1 is a potent stress-response protein promoting p53 activity. We previously showed that ectopic overexpression of TP53INP1 facilitates cell cycle arrest as well as cell death. Here we report a study investigating cell death in mice deficient for TP53INP1. Surprisingly, we found enhanced stress-induced apoptosis in TP53INP1-deficient cells. This observation is underpinned in different cell types in vivo (thymocytes) and in vitro (thymocytes and MEFs), following different types of injury inducing either p53-dependent or -independent cell death. Nevertheless, absence of TP53INP1 is unable to overcome impaired cell death of p53-deficient thymocytes. Stress-induced ROS production is enhanced in the absence of TP53INP1, and antioxidant NAC complementation abolishes increased sensitivity to apoptosis of TP53INP1-deficient cells. Furthermore, antioxidant defenses are defective in TP53INP1-deficient mice in correlation with ROS dysregulation. Finally, we show that autophagy is reduced in TP53INP1-deficient cells both at the basal level and upon stress. Altogether, these data show that impaired ROS regulation in TP53INP1-deficient cells is responsible for their sensitivity to induced apoptosis. In addition, they suggest that this sensitivity could rely on a defect of autophagy. Therefore, these data emphasize the role of TP53INP1 in protection against cell injury.