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ASPP (apoptosis-stimulating proteins of p53) proteins bind PP-1c (protein phosphatase 1) and regulate p53 impacting cancer cell growth and apoptosis. Here we determine the crystal structure of the oncogenic ASPP protein, iASPP, bound to PP-1c. The structure reveals a 1:1 complex that relies on interactions of the iASPP SILK and RVxF motifs with PP-1c, plus interactions of the PP-1c PxxPxR motif with the iASPP SH3 domain. Small-angle X-ray scattering analyses suggest that the crystal structure undergoes slow interconversion with more extended conformations in solution. We show that iASPP, and the tumor suppressor ASPP2, enhance the catalytic activity of PP-1c against the small-molecule substrate, pNPP as well as p53. The combined results suggest that PxxPxR binding to iASPP SH3 domain is critical for complex formation, and that the modular ASPP-PP-1c interface provides dynamic flexibility that enables functional binding and dephosphorylation of p53 and other diverse protein substrates.

Introduction: Since its discovery in 1999, a substantial body of research has shown that iASPP is highly expressed in various kinds of tumors, interacts with p53, and promotes cancer cell survival by antagonizing the apoptotic activity of p53. However, its role in neurodevelopment is still unknown. Methods: We studied the role of iASPP in neuronal differentiation through different neuronal differentiation cellular models, combined with immunohistochemistry, RNA interference and gene overexpression, and studied the molecular mechanism involved in the regulation of neuronal development by iASPP through coimmunoprecipitation coupled with mass spectrometry (CoIP-MS) and coimmunoprecipitation (CoIP). Results: In this study, we found that the expression of iASPP gradually decreased during neuronal development. iASPP silencing promotes neuronal differentiation, while its overexpression inhibited neurite differentiation in a variety of neuronal differentiation cellular models. iASPP associated with the cytoskeleton-related protein Sptan1 and dephosphorylated the serine residues in the last spectrin repeat domain of Sptan1 by recruiting PP1. The non-phosphorylated and phosphomimetic mutant form of Sptbn1 inhibited and promoted neuronal cell development respectively. Conclusion: Overall, we demonstrate that iASPP suppressed neurite development by inhibiting phosphorylation of Sptbn1. [ABSTRACT FROM AUTHOR]

Simple Summary: The hyaluronan receptor CD44 plays a vital role in tumor cell growth and chemotherapy resistance. The tumor suppressor p53 binds to the CD44 promoter via a non-canonical p53 consensus sequence and suppresses CD44 expression, promoting apoptosis. Conversely, the apoptotic function of p53 is negatively regulated through its interactions with iASPP, a specific inhibitor of p53-induced apoptosis in both normal and cancer cells. CD44, p53, and iASPP are co-expressed in a wide array of human cancers; however, the precise role of CD44 in p53-mediated apoptosis is not known. We discovered that the standard isoform of CD44 physically bound to iASPP and dictated the sub-cellular localization of iASPP-p53 complexes. The iASPP-CD44 complex affected fibroblast adhesion, migration, growth, and p53-mediated apoptosis. In the present study, we show that the inhibitor of the apoptosis-stimulating protein of p53 (iASPP) physically interacts with the hyaluronan receptor CD44 in normal and transformed cells. We noticed that the CD44 standard isoform (CD44s), but not the variant isoform (CD44v), bound to iASPP via the ankyrin-binding domain in CD44s. The formation of iASPP-CD44s complexes was promoted by hyaluronan stimulation in fibroblasts but not in epithelial cells. The cellular level of p53 affected the amount of the iASPP-CD44 complex. iASPP was required for hyaluronan-induced CD44-dependent migration and adhesion of fibroblasts. Of note, CD44 altered the sub-cellular localization of the iASPP-p53 complex; thus, ablation of CD44 promoted translocation of iASPP from the nucleus to the cytoplasm, resulting in increased formation of a cytoplasmic iASPP-p53 complex in fibroblasts. Overexpression of iASPP decreased, but CD44 increased the level of intracellular reactive oxygen species (ROS). Knock-down of CD44s, in the presence of p53, led to increased cell growth and cell density of fibroblasts by suppression of p27 and p53. Our observations suggest that the balance of iASPP-CD44 and iASPP-p53 complexes affect the survival and migration of fibroblasts. [ABSTRACT FROM AUTHOR]

Ca2+ release from the endoplasmic reticulum (ER) is an essential event in the modulation of Ca2+ homeostasis, which is coordinated by multiple biological processes, ranging from cell proliferation to apoptosis. Deregulated Ca2+ homeostasis is linked with various cancer hallmarks; thus, uncovering the mechanisms underlying Ca2+ homeostasis dynamics may lead to new anticancer treatment strategies. Here, we demonstrate that a reported Ca2+-channel protein TMCO1 (transmembrane and coiled-coil domains 1) is overexpressed in colon cancer tissues at protein levels but not at messenger RNA levels in colon cancer. Further study revealed that TMCO1 is a substrate of ER-associated degradation E3 ligase Gp78. Intriguingly, Gp78-mediated TMCO1 degradation at K186 is under the control of the iASPP (inhibitor of apoptosis-stimulating protein of p53) oncogene. Mechanistically, iASPP robustly reduces ER Ca2+ stores, mainly by competitively binding with Gp78 and interfering with Gp78-mediated TMCO1 degradation. A positive correlation between iASPP and TMCO1 proteins is further validated in human colon tissues. Inhibition of iASPP-TMCO1 axis promotes cytosolic Ca2+ overload-induced apoptotic cell death, reducing tumor growth both in vitro and in vivo. Thus, iASPP-TMCO1 represents a promising anticancer treatment target by modulating Ca2+ homeostasis. [ABSTRACT FROM AUTHOR]

Acute lung injury (ALI), a common and critical illness with high morbidity and mortality, is caused by multiple causes. It has been confirmed that oxidative stress plays an important role in the development of ALI. Ferroptosis, a newly discovered programmed cell death in 2012, is characterized by iron-dependent lipid peroxidation and involved in many diseases. To date, compelling evidence reveals the emerging role of ferroptosis in the pathophysiological process of ALI. Here, we review the role of ferroptosis in the pathogenesis of ALI and its therapeutic potential in ALI. [ABSTRACT FROM AUTHOR]

The inhibitor of apoptosis‐stimulating protein of p53 (iASPP) acts as a key modulator of cellular protection against oxidative stress. In the present work, we assessed the role of iASPP in the regulation of cardiomyocyte injury induced by hypoxia/reoxygenation (H/R). We found that H/R‐exposed cardiomyocytes expressed decreased levels of iASPP. The upregulation of iASPP repressed H/R‐induced injury by decreasing levels of apoptosis and reactive oxygen species production. The upregulation of iASPP increased nuclear factor (erythroid‐derived 2)‐like 2 (Nrf2) nuclear translocation and enhanced Nrf2 activation. The overexpression of Kelch‐like ECH‐associated protein 1 reversed iASPP‐mediated promotion of Nrf2 activation. Nrf2 inhibition abrogated iASPP‐mediated cardioprotective effects in H/R‐exposed cardiomyocytes. Our work demonstrates that the upregulation of iASPP ameliorates H/R‐induced apoptosis and oxidative stress in cardiomyocytes via potentiating Nrf2 signaling via modulation of Keap1. [ABSTRACT FROM AUTHOR]

Childhood dilated cardiomyopathy (DCM) is a leading cause of heart failure requiring cardiac transplantation and approximately 5% of cases result in sudden death. Knowledge of the underlying genetic cause can aid prognostication and clinical management and enables accurate recurrence risk counselling for the family. Here we used genomic sequencing to identify the causative genetic variant(s) in families with children affected by severe DCM. In an international collaborative effort facilitated by GeneMatcher, biallelic variants in PPP1R13L were identified in seven children with severe DCM from five unrelated families following exome or genome sequencing and inheritance‐based variant filtering. PPP1R13L encodes inhibitor of apoptosis‐stimulating protein of p53 protein (iASPP). In addition to roles in apoptosis, iASPP acts as a regulator of desmosomes and has been implicated in inflammatory pathways. DCM presented early (mean: 2 years 10 months; range: 3 months‐9 years) and was progressive, resulting in death (n = 3) or transplant (n = 3), with one child currently awaiting transplant. Genomic sequencing technologies are valuable for the identification of novel and emerging candidate genes. Biallelic variants in PPP1R13L were previously reported in a single consanguineous family with paediatric DCM. The identification here of a further five families now provides sufficient evidence to support a robust gene‐disease association between PPP1R13L and severe paediatric DCM. The PPP1R13L gene should be included in panel‐based genetic testing for paediatric DCM. [ABSTRACT FROM AUTHOR]

Aims: Inhibitor for the apoptosis-stimulating protein of p53 (iASPP) has been reported to be correlated with 5-fluorouracil (5-Fu) resistance in renal cell carcinoma. Here, we uncover mechanisms of iASPP-Nrf2-ROS regulation of 5-Fu resistance which are important for the development of alternative treatment strategies for gastric adenocarcinoma treatment. Methods: We analyzed iASPP and Nrf2 through TCGA RNA-seq data, UALCAN analysis, and cBioPortal datasets. Intracellular ROS generation was determined by 2′,7′-dichloro-fluorescin diacetate staining. Transwell was used to evaluate the invasion. The expression of iASPP, Nrf2, HO-1, and GSTP1 was tested using western blot. Results: We found that iASPP KD led to an apparent 5-Fu-induced ROS accumulation in MGC803 and SCG790 cells. Accompanied by iASPP KD, Nrf2 was markedly decreased. iASPP-induced ROS inhibition relies on Nrf2, and due to both knocked down iASPP and Nrf2, the level of ROS did not show an obvious difference with Nrf2 KD solely. Similarly, iASPP KD failed to enhance the Nrf2 KD-mediated ROS accumulation after 5-Fu treatment, suggesting that iASPP-induced antioxidative effects related to 5-Fu resistance are partially dependent on Nrf2. Also, the combination of iASPP KD and Nrf2 KD did not show any synergistic effect on apoptosis after 5-Fu treatment in MGC803 and SCG790 cells. Further studies revealed that iASPP KD or Nrf2 KD could decrease the expression of HO-1 and GSTP1. Conclusions: Our data highlight that iASPP plays a crucial role in the inhibition of 5-Fu-induced apoptosis resistance by removing ROS accumulation in gastric adenocarcinoma, and that the removal of ROS induced by iASPP is Nrf2 signaling dependent. [ABSTRACT FROM AUTHOR]

Intrinsically disordered regions in proteins (IDRs) mediate many disease‐related protein–protein interactions. However, the unfolded character and continuous conformational changes of IDRs make them difficult to target for therapeutic purposes. Here, we show that a designed peptide based on the disordered p53 linker domain can be used to target a partner IDR from the anti‐apoptotic iASPP protein, promoting apoptosis of cancer cells. The p53 linker forms a hairpin‐like structure with its two termini in close proximity. We designed a peptide derived from the disordered termini without the hairpin, designated as p53 LinkTer. The LinkTer peptide binds the disordered RT loop of iASPP with the same affinity as the parent p53 linker peptide, and inhibits the p53–iASPP interaction in vitro. The LinkTer peptide shows increased stability to proteolysis, penetrates cancer cells, causes nuclei shrinkage, and compromises the viability of cells. We conclude that a designed peptide comprising only the IDR from a peptide sequence can serve as an improved inhibitor since it binds its target protein without the need for pre‐folding, paving the way for therapeutic targeting of IDRs. [ABSTRACT FROM AUTHOR]

Introduction: Chordoma is a malignant primary bone tumor that is found in the spine and skull. X-inactive specific transcript (XIST) is a long non-coding RNA (lncRNA) is known to be involved in the development of various cancers, but its precise function and mechanism in human chordoma have not been elucidated. Here, we investigated the role of lncRNA XIST in chordoma progression. Methods: Quantitative real time-polymerase chain reaction (qRT-PCR) was performed to determine lncRNA XIST expression in human chordoma tissues and matched-noncancerous tissues. Western blot was used to determine protein expression. Silencing and overexpression of lncRNA XIST were carried out by RNA interference (RNAi) and lentiviral transduction, respectively. Cell Counting Kit-8 (CCK-8) assay and flow cytometry were employed to examine the effects of lncRNA XIST on growth of human chordoma cells. Lastly, the role of lncRNA XIST in vivo was explored using a xenograft model. Results: We found that lncRNA XIST expression was upregulated in chordoma and strongly correlated with poor patient prognosis. Moreover, lncRNA XIST promoted proliferation and inhibited apoptosis of chordoma cells. Mechanistically, upregulation of lncRNA XIST led to a decrease in miR-124-3p expression, thereby promoting the expression of the miR-124-3p target gene, inhibitor of apoptosis-stimulating protein of p53 (iASPP). Addition of miR-124-3p inhibitor or mimic reversed the effects induced by lncRNA XIST silencing or overexpression on chordoma cell proliferation. Lastly, using a xenograft mouse model, we found that silencing of lncRNA XIST decreased tumorigenicity in vivo, as shown by increased tumor cell apoptosis. Conclusion: Our findings demonstrate a key role for lncRNA XIST in chordoma progression by regulating miR124-3p/iAPSS pathway. [ABSTRACT FROM AUTHOR]

Abstract Background As the important suppressor of P53, iASPP is found to be overexpressed in leukemia, and functions as oncogene that inhibited apoptosis of leukemia cells. Sertad1 is identified as one of the proteins that can bind with iASPP in our previous study by two-hybrid screen. Methods Co-immunoprecipitation and immunofluorescence were perfomed to identified the interaction between iASPP and Sertad1 protein. Westernblot and Real-time quantitative PCR were used to determine the expression and activation of proteins. Cell proliferation assays, cell cycle and cell apoptosis were examined by flow cytometric analysis. Results iASPP combined with Sertad1 in leukemic cell lines and the interaction occurred in the cytoplasm near nuclear membrane. iASPP could interact with Sertad1 through its Cyclin-A, PHD-bromo, C terminal domain, except for S domain. Overexpression of iASPP in leukemic cells resulted in the increased cell proliferation and resistance to apoptosis induced by chemotherapy drugs. While overexpression of iASPP and Sertad1 at the same time could slow down the cell proliferation, lead the cells more vulnerable to the chemotherapy drugs, the resistance to chemotherapeutic drug in iASPPhi leukemic cells was accompanied by Puma protein expression. Excess Sertad1 protein could tether iASPP protein in the cytoplasm, further reduced the binding between iASPP and P53 in the nucleus. Conclusions Sertad1 could antagonize iASPP function by hindering its entrance into nuclei to interact with P53 in leukemic cells when iASPP was in the stage of overproduction.

Abstract Background Epithelial–mesenchymal transition (EMT) and dysregulated microRNAs (miRNAs) have important roles in driving chemoresistance. We previously reported that iASPP is a key EMT inducer and could increase cisplatin resistance in cervical cancer (CC) cells. Herein, we investigate the downstream mechanisms through which iASPP contributes to EMT and cisplatin resistance in CC. Methods By using a lentiviral system, we investigated the effects of iASPP knockdown on CC cell growth and chemosensitivity of CC cells to cisplatin in vivo. We examined if miR-20a, which was up-regulated following iASPP overexpression, would influence metastatic phenotypes and cisplatin resistance in CC cells, and explored the possible molecular mechanisms involved. Results Knockdown of iASPP suppressed CC cell proliferation and sensitized CC cells to cisplatin in vivo. iASPP promotes miR-20a expression in a p53-dependent manner. Upregulation of miR-20a induced EMT and the recovery of CC cell invasion and cisplatin chemoresistance that was repressed by iASPP knockdown. We identified FBXL5 and BTG3 as two direct miR-20a targets. Silencing of FBXL5 and BTG3 restored cell invasion and cisplatin chemoresistance, which was suppressed by iASPP or miR-20a knockdown. Reduced FBXL5 and BTG3 expression was found in CC samples and associated with poor prognosis in CC patients. Conclusions iASPP promotes EMT and confers cisplatin resistance in CC via miR-20a-FBXL5/BTG3 signaling.

Our previous study has revealed that iASPP is elevated in human head and neck squamous cell carcinoma (HNSCC) and iASPP overexpression signifcantly correlates with tumor malignant progression and poor survival of HNSCC. This study investigated the function of iASPP playing in proliferation and invasion of HNSCC in vitro. HNSCC cell line Tu686 transfected with Lentiviral vector-mediated iASPP-specific shRNA and control shRNA were named the shRNA-iASPP group and shRNA-NC group, respectively. The non-infected Tu686 cells were named the CON group. CCK-8 assay, flow cytometry, transwell invasion assay were performed to detect the effects of iASPP inhibition in vitro. Our results demonstrated that the proliferation of shRNA-iASPP cells at the time of 72 h (F =32.459, P =0.000), 96 h (F =51.407, P =0.000), 120 h (F =35.125, P =0.000) post-transfection, was significantly lower than that of shRNANC cells and CON cells. The apoptosis ratio of shRNA-iASPP cells was 9.42% ± 0.39% (F =299.490, P=0.000), which was significantly higher than that of CON cells (2.80% ± 0.42%) and shRNA-NC cells (3.18% ± 0.28%). The percentage of shRNA-iASPP cells in G0/G1 phase was 74.65% ± 1.09% (F =388.901, P =0.000), which was strikingly increased, compared with that of CON cells (55.19% ± 1.02%) and shRNA-NC cells (54.62% ± 0.88%). The number of invading cells was 56 ± 4 in the shRNA-iASPP group (F =84.965, P =0.000), which decreased significantly, compared with the CON group (111 ± 3) and the shRNA-NC group (105 ± 8). The survival rate of shRNA-iASPP cells administrated with paclitaxel was highly decreased, compared with CON cells and shRNA-NC cells (F =634.841, P =0.000). These results suggest iASPP may play an important role in progression and aggressive behavior of HNSCC and may be an efficient chemotherapeutic target for the treatment of HNSCC. [ABSTRACT FROM AUTHOR]

The most frequently mutated protein in human cancer is p53, a transcription factor (TF) that regulates myriad genes instrumental in diverse cellular outcomes including growth arrest and cell death. Cell context-dependent p53 modulation is critical for this life-or-death balance, yet remains incompletely understood. Here we identify sequence signatures enriched in genomic p53-binding sites modulated by the transcription cofactor iASPP. Moreover, our p53-iASPP crystal structure reveals that iASPP displaces the p53 L1 loop-which mediates sequence-specific interactions with the signature-corresponding base-without perturbing other DNArecognizing modules of the p53 DNA-binding domain. A TF commonly uses multiple structural modules to recognize its cognate DNA, and thus this mechanism of a cofactor fine-tuning TF-DNA interactions through targeting a particular module is likely widespread. Previously, all tumor suppressors and oncoproteins that associate with the p53 DNA-binding domain-except the oncogenic E6 from human papillomaviruses (HPVs)-structurally cluster at the DNA-binding site of p53, complicating drug design. By contrast, iASPP inhibits p53 through a distinct surface overlapping the E6 footprint, opening prospects for p53-targeting precision medicine to improve cancer therapy. [ABSTRACT FROM AUTHOR]

Objective: To investigate the changes in serum miR-124 levels in patients with acute cerebral infarction (ACI) and elucidate the underlying mechanism by a dynamic monitor. Methods: Fifty-four patients with ACI and 51 healthy controls were included in our study. Baseline characteristics and blood samples were collected for further analysis. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure the serum miR-124 levels. The dual-luciferase reporter assay was used to evaluate the effect of miR-124 on iASPP, a protein that inhibits apoptosis stimulating proteins in the p53 family. Results: Compared with normal controls, the miR-124 levels in the ACI group rapidly decreased at phase 1 (within 24 h after ischemia) (p < 0.001) and then gradually increased at phase 2 (48 ∼ 72 h after ischemia) (p < 0.001) and phase 3 (the 7th day after ischemia) (p < 0.001). The dual-luciferase reporter assay showed that miR-124 down-regulates iASPP expression in 293T cells. Conclusion: The miR-124 levels are down-regulated in ACI patients. The dynamic changes of miR-124 might provide a possible method for the detection of ischemic stroke. The difference in miR-124 expression levels between ACI patients and normal controls. Dynamic changes of miR-124 expression levels in ACI patients. The down-regulation of miR-124 upon iASPP expression. [ABSTRACT FROM AUTHOR]

Ovarian clear cell carcinoma (OCCC) is a type of epithelial ovarian cancer that is strongly associated with endometriosis, resistance against conventional chemotherapy and thus poorer prognosis. The expression of inhibitory member of the ASPP family proteins (iASPP) and Polo‐like kinase (PLK)1 were significantly higher in OCCC compared to benign cystadenomas and endometriosis. Both protein expressions were found to correlate with chemoresistance in patients with OCCC while high iASPP expression alone was significantly associated with a poor patient survival. The growth of OCCC cell lines, OVTOKO and KK, were inhibited after iASPP silencing. Such effect was related to senescence triggering as evidenced by increased SA‐β‐Gal staining and p21WAF1/Cip1 expression. Moreover, knockdown of iASPP induced PLK1 downregulation, whereas either genes’ silencing sensitized the cells in response to cisplatin treatment. More prominent apoptosis was induced by cisplatin in OCCC cells after the knockdown of either iASPP or PLK1 as evidenced by the formation of more cleaved caspase 3. Heightened chemosensitivity to cisplatin after iASPP knockdown was further demonstrated in in vivo xenograft model. Additionally, both iASPP and PLK1 were shown to regulate autophagic flux as the induction of LC3B‐II and LC3 puncta were much less in OCCC cells with either knockdown. Importantly, inhibition of autophagy also enhanced chemosensitivity to cisplatin in OCCC cells. These findings strongly imply that iASPP and PLK1 affect the chemoresistance of OCCC via the regulation of autophagy and apoptosis. Both iASPP and PLK1 can be potential therapeutic targets for treating OCCC in combination with conventional chemotherapy. [ABSTRACT FROM AUTHOR]

Long-term exposure to ultraviolet B (UVB) light increases the risk of UVB damage due to increased UVB absorption by the retina and may further lead to age-related eye diseases. The retinal pigment epithelium (RPE) cell is a main target of UVB reaching the retina; its degeneration is an essential event in UVB-mediated age-related macular degeneration (AMD). Herein, we first evaluated the expression and effect of iASPP, an inhibitory regulator of apoptosis, in UVB-induced RPE cell damage. Through the mechanism of RNA interference at the post-transcriptional level, miRNA affects a variety of cellular processes, including UVB-mediated cell damage. We next screened for upstream candidate miRNAs that may regulate iASPP expression. Among 8 candidate miRNAs, UVB significantly increased miR-340 levels. We also confirmed the direct binding of miR-340 to the 3′UTR of iASPP, and assessed the combined effect of miR-340 and iASPP on UVB-induced RPE cell damage. Taken together, we demonstrated the possible mechanisms involved in UVB-induced retinal damage. In RPE cells, UVB irradiation inhibits iASPP expression through inducing miR-340 expression, thereby promoting RPE cell apoptosis and suppressing cell viability via affecting p53, p21 and caspase-3 protein expression. Targeting miR-340 to rescue iASPP expression in RPE cells may help treat UVB-mediated retinal damage. [ABSTRACT FROM AUTHOR]

Lung cancer is the leading cause of cancer‐related death worldwide. Thus, developing novel therapeutic agents has become critical for lung cancer treatment. In this study, compound AS7128 was selected from a 2‐million entry chemical library screening and identified as a candidate drug against non‐small cell lung cancer in vitro and in vivo. Further investigation indicated that AS7128 could induce cell apoptosis and cell cycle arrest, especially in the mitosis stage. In addition, we also found that iASPP, an oncogenic protein that functionally inhibits p53, might be associated with AS7128 through mass identification. Further exploration indicated that AS7128 treatment could restore the transactivation ability of p53 and, thus, increase the expressions of its downstream target genes, which are related to cell cycle arrest and apoptosis. This occurs through disruption of the interactions between p53 and iASPP in cells. Taken together, AS7128 could bind to iASPP, disrupt the interaction between iASPP and p53, and result in cell cycle arrest and apoptosis. These findings may provide new insight for using iASPP as a therapeutic target for non‐small cell lung cancer treatment. [ABSTRACT FROM AUTHOR]

Long non-coding RNA (lncRNA) urothelial carcinoma associated 1 (UCA1) has been reported to be involved in the development and progression of many types of tumors including breast cancer, gastric cancer, and bladder cancer. However, the exact effects and molecular mechanisms of UCA1 in glioma progression remain unclear up to now. In this study, we firstly found that UCA1 was upregulated in glioma tumor samples and negatively correlated with survival time. Then, we investigated the role of UCA1 in human glioma cell lines. Our results showed that upregulation of lncRNA-UCA1 in glioma tissues and cell lines could promote glioma cell proliferation and migration through interaction with miR-182, and knockdown of UCA1 inhibited the proliferation and migration of human glioma cell. In addition, miR-182 dependent inhibitor of apoptosis-stimulating protein of p53 (iASPP) was required in the regulation of UCA1 induced glioma cell proliferation. Taken together, UCA1 might promote proliferation and migration of glioma, to regulate the tumor growth and metastasis via miR-182 dependent iASPP regulation. Therefore, lncRNA-UCA1 could be regarded as a therapeutic target in human glioma. [ABSTRACT FROM AUTHOR]

Ischemic stroke is one of the leading causes of death and disability globally and has been regarded as a major public health problem. MicroRNA 182 (miR-182) plays important roles in cellular differentiation, cell growth, cell apoptosis and metastasis. However, the role of miR-182 in the cerebral ischemia injury has never been investigated. In the present study, we demonstrate a crucial role of miR-182 in down-regulating inhibitory member of the ASPP family (iASPP) expression and promoting cerebral ischemia injury. MiR-182 also promotes NO and 3-NT production, and Caspase3 expression, while reduces SOD and MnSOD activities. Furthermore, the amplified cerebral ischemia injury induced by miR-182 is aggravated by inhibition of iASPP. In conclusion, miR-182 plays an aggressive role in the cerebral ischemia injury, and this is associated with inhibited iASPP expression. [ABSTRACT FROM AUTHOR]

Introduction: The ASPP family (apoptosis – stimulating proteins of p53) comprises three proteins, ASPP1, ASPP2 and iASPP, that interact with and modulate the behavior of p53. ASPP1 and ASPP2 enhance the ability of p53 to induce apoptosis by causing p53 to up regulate the expression of proapoptotic genes specifically rather than genes involved in cell cycle arrest. Inhibitory member of the ASPP family (iASPP) acts as inhibitor for the p53, it was originally identified as a nuclear protein that interacts with and inhibits NFkb p56 RelA and inhibits p53-mediated cell death as well. Material and methods: To examine the role of iASPP in acute leukemic patients, we analyzed iASPP mRNA expression in acute leukemia by semi quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Results: The results showed that the median level of iASPP in acute lymphoblastic leukemia and acute myeloid leukemia patients was significantly higher than those in cells from normal donors (p=0.04). The expression of iASPP in ALL and AML patients was not associated with age, gender, hemoglobin, platelets; blasts count in bone marrow, treatment outcome but was associated with blasts count in peripheral blood and total leucocytic count in AL patients. Conclusions: The results of the present study suggest that iASPP may play a role in leukemogenesis and/or disease progression of acute leukemia.

MALAT1, an important cancer-associated long noncoding RNA (lncRNA), contributes to the development and progression of several cancers. Disordered expression of MALAT1 has been observed in several cancers, including cervical cancer, breast cancer, and ovarian cancer. However, the exact effects and molecular mechanisms of MALAT1 in ovarian cancer progression are still unknown. Here, we investigated the role of MALAT1 in human ovarian cancer cell lines and clinical tumor samples, in order to determine the function of this molecule. In our research, lncRNA-MALAT1 was specifically upregulated in ovarian cancer cell lines and promoted ovarian cancer-cell growth through targeting microRNA (miR)-506. Knockdown of MALAT1 inhibited the proliferation and DNA synthesis of human ovarian cancer cell in vitro. In addition, miR-506-dependent iASPP regulation was required in MALAT1- induced ovarian cancer-cell growth. These findings indicated that MALAT1 might suppress tumor growth via miR-506-dependent iASPP regulation. Taken together, our data indicated that MALAT1 might be an oncogenic lncRNA that promotes proliferation of ovarian cancer and could be regarded as a therapeutic target in human ovarian cancer. [ABSTRACT FROM AUTHOR]

H19, one of the first found cancer-associated long non-coding RNAs (lncRNAs), is involved in the development and progression of many types of tumors. An aberrant expression of H19 was observed in hepatocellular carcinoma, cervical cancer, breast cancer, ovarian cancer, and colorectal cancer. However, the exact effects and molecular mechanisms of H19 in glioma progression are still unknown up to now. In this study, we investigated the role of H19 in human glioma cell lines and clinical tumor samples in order to determine the function of this molecule. In our research, lncRNA-H19 was specifically upregulated in glioma cell lines and promoted glioma cell growth through targeting miR-140. Knockdown of H19 inhibited the proliferation and invasion of human glioma cell and suppressed its metastasis in vitro and in vivo. In addition, miR-140 dependent inhibitor of apoptosis-stimulating protein of p53 (iASPP) regulation was required in H19 induced glioma cell growth. These findings indicated that H19 might regulate the tumor growth and metastasis via miR-140 dependent iASPP regulation. Taken together, our data indicated that H19 might be an oncogenic lncRNA that promoted proliferation and metastasis of glioma and could be regarded as a therapeutic target in human glioma. [ABSTRACT FROM AUTHOR]

Inhibitor of apoptosis-stimulating protein of p53 (iASPP), encoded by PPP1R13L gene, is often overexpressed in human cancers. From the PPP1R13L gene, at least two isoforms, iASPP-L and iASPP-SV, are produced through alternative splicing. However, the role of these isoforms in glioma is still elusive. In this study, we examined the expression of iASPP-SV in astrocytic glioma tissues with different grades and normal human cerebral tissues. The result showed a higher messenger RNA (mRNA) expression level of iASPP-SV in astrocytic glioma patients with World Health Organization (WHO) grade II to IV in comparison to the normal controls. Additionally, mRNA expression level of iASPP-SV was gradually increased with the raise of the grade in glioma. High mRNA expression level of iASPP-SV was significantly associated with malignant WHO grades ( P < 0.001). The protein expression level of iASPP-SV was consistent with the mRNA expression level. The Kaplan-Meier analysis revealed that high iASPP-SV mRNA expression significantly affected overall survival and progression-free survival (both P < 0.001). Furthermore, multivariate analysis indicated that the mRNA expression of iASPP-SV was an independent prognostic marker in glioma ( P < 0.001). To further explore the role of iASPP-SV in glioma, U87 cells were transfected with iASPP-SV by lentivirus and then treated with temozolomide (TMZ). Overexpression of iASPP-SV promoted the cell viability and downregulated the expression of pro-apoptosis genes (Bax, Puma, p21, and Noxa) to inhibit apoptosis induced by TMZ. Our study provides the first evidence that high iASPP-SV expression may be a novel prognostic factor and therapeutic target for glioma. [ABSTRACT FROM AUTHOR]

Concurrent mutation of a RAS oncogene and the tumor suppressor p53 is common in tumorigenesis, and inflammation can promote RAS-driven tumorigenesis without the need to mutate p53. Here, we show, using a well-established mutant RAS and an inflammation-driven mouse skin tumor model, that loss of the p53 inhibitor iASPP facilitates tumorigenesis. Specifically, iASPP regulates expression of a subset of p63 and AP1 targets, including genes involved in skin differentiation and inflammation, suggesting that loss of iASPP in keratinocytes supports a tumor-promoting inflammatory microenvironment. Mechanistically, JNK-mediated phosphorylation regulates iASPP function and inhibits iASPP binding with AP1 components, such as JUND, via PXXP/SH3 domain-mediated interaction. Our results uncover a JNK-iASPP-AP1 regulatory axis that is crucial for tissue homeostasis. We show that iASPP is a tumor suppressor and an AP1 coregulator. [Display omitted] • iASPP is a tumor suppressor of DMBA/TPA-driven mouse skin tumorigenesis • iASPP controls selective transcription of AP1 and p63 target genes in keratinocytes • JNK activation disrupts iASPP-JunD complexes that are mediated by PxxP/SH3 binding • iASPP is a regulator of the AP1 signaling pathway Al Moussawi et al. show that iASPP, a known p53 inhibitor, suppresses inflammation-driven skin tumorigenesis in vivo. Mechanistically, iASPP binds JunD via PxxP/SH3 interaction and forms a JNK-iASPP-AP1 axis that selectively represses the expression of a subset of AP1 and p63 target genes involved in skin differentiation and inflammation. [ABSTRACT FROM AUTHOR]

One of the most important tumor suppression functions of p53 is its ability to induce apoptosis. iASPP is an inhibitory member of the ASPP protein family. It can specifically inhibit the normal function of p53 as a suppressor. The mechanism of iASPP suppressing the cell apoptotosis is through inhibiting the transactivation function of p53 on the promoters of proapoptotic genes by binding with p53. Therefore, relieving the combination of iASPP with p53 and leaving p53 free may be a useful strategy to activate p53 function. We therefore use A34, a small peptide derived from p53 linker region, to investigate the possibility of resuming the apoptosis activity of p53 by sequestering iASPP with p53 and derepressing p53. The results show that A34 can competitively combine with iASPP and therefore release p53 from iASPP; A34 can enhance the transcriptional activity of p53 on the promoters of Bax and PUMA; A34 can increase cell apoptosis and slow tumor growth in vitro and vivo. This study will open the way for using small molecule peptides that directly disturb the interaction of p53 with iASPP, thereby resume function of p53 as a suppressor. [ABSTRACT FROM AUTHOR]

The protein iASPP (encoded by PPP1R13L) is an evolutionarily conserved p53 inhibitor, the expression of which is often upregulated in human cancers. We have recently shown that iASPP is a crucial regulator of epidermal homeostasis. Here, we report that iASPP also acts as autophagy inhibitor in keratinocytes. Our data show that depletion of iASPP protects keratinocytes from apoptosis by modulating the expression of Noxa (also known as PMAIP1). In our model, iASPP expression can affect the fission-fusion cycle, mass and shape of mitochondria. iASPP-silenced keratinocytes display disorganization of cytosolic compartments and increased metabolic stress caused by deregulation of mTORC1 signaling. Moreover, increased levels of lipidated LC3 protein confirmed the activation of autophagy in iASPP-depleted cells. We have identified a novel mechanism modulating autophagy in keratinocytes that relies upon iASPP expression specifically reducing the interaction of Atg5-Atg12 with Atg16L1, an interaction that is essential for autophagosome formation or maturation. Using organotypic culture, we further explored the link between autophagy and differentiation, and we showed that impairing autophagy affects epidermal terminal differentiation. Our data provide an alternative mechanism to explain how epithelial integrity is maintained against environmental stressors and might also improve the understanding of the etiology of skin diseases that are characterized by defects in differentiation and DNA damage responses. [ABSTRACT FROM AUTHOR]

Abstract: Aims: There has been limited information about the relations between Helicobacter pylori infection and expressions of apoptosis-related proteins p53, ASPP and iASPP in gastric cancer and precancerous lesions. Methods: H. pylori in gastric mucosa were identified by W-S staining and rapid urease test. Expression of apoptosis-related proteins P53, ASPP2 and iASPP in the gastric tissues were determined by immunohistochemistry. Results: The concentrations of H. pylori and expressions of p53 and iASPP in gastric carcinoma group and precancerous lesion group were higher than in benign gastric diseases group (P <0.05). The expressions of ASPP2 in gastric carcinoma and precancerous lesion group were lower than in benign gastric diseases group (P <0.05). The expressions of p53 and iASPP in H. pylori positive group were higher than in H. pylori negative group (P <0.05), whereas ASPP2 in H. pylori positive group were lower than in H. pylori negative group (P <0.05). Conclusion: There was a higher rate H. pylori infection, an increased expression of apoptosis inhibitor iASPP, and decreased expression of apoptosis stimulator ASPP2 in gastric cancer or precancerous tissues. These results suggest that H. pylori may cause gastric cancer by up-regulating iASPP and down-regulating ASPP2. [Copyright &y& Elsevier]

iASPP (inhibitory member of the ASPP family), the conserved key inhibitor of p53, is overexpressed and plays an important oncogenetic role in many human cancers. However, its function in cervical cancer remains unknown. The objective of this study was to investigate the expression and clinical relevance of iASPP in cervical cancer. The mRNA and protein expression levels of iASPP were determined by real-time quantitative reverse transcription with the polymerase chain reaction and Western blot. Paraffin sections of 149 patients with FIGO Ib1-IIa squamous cell cervical cancer were stained by using immunohistochemistry for iASPP, and its relationship with clinicopathologic parameters and prognosis of cervical cancer patients was analyzed. The mRNA and protein expression levels of iASPP were significantly elevated in cervical cancer tissues. The increased nuclear iASPP expression was correlated strongly with higher FIGO staging, deep cervical stromal invasion, pelvic lymph node metastasis, and poor overall and disease-free survival of patients with cervical cancer (all P<0.05). Multivariate Cox analysis showed that high nuclear iASPP expression was an independent prognostic factor for overall survival. Furthermore, patients with high nuclear iASPP expression were much more resistant to radiation or chemotherapy, resulting in poor overall and disease-free survival than those with low expression after receiving radiation or chemotherapy (all P<0.05) and indicating correlations with chemoresistance and radioresistance. This study thus demonstrates that iASPP is highly elevated in human cervical cancer, and that overexpression of nuclear iASPP is correlated with poor prognosis and chemoresistance/radioresistance, suggesting that iASPP might serve as a novel potential prognostic marker and therapeutic target for cervical cancer. [ABSTRACT FROM AUTHOR]

iASPP is shown to be elevated in several cancers. However, the role of iASPP in head and neck squamous cell carcinoma (HNSCC) remains unknown. We have investigated iASPP expression in HNSCC tissue and cell lines and evaluated its prognostic significance in HNSCC. The expression of iASPP in 109 primary HNSCC tissue specimens was examined by immunohistochemistry and its association with clinicopathological parameters and prognosis was analyzed. Additionally, expression status of iASPP in 16 paired HNSCC tissues and 7 HNSCC cell lines was evaluated by quantitative real-time PCR ( qPCR) and immunoblotting. The protein and mRNA expression of iASPP were increased in HNSCC tissues and cell lines. Immunohistochemical staining indicated iASPP was detected in both cytoplasm and nucleus. Importantly, overexpression of cytoplasmic and nuclear iASPP was significantly associated with T classification ( p = 0.002 and p = 0.033, respectively), clinical stage ( p < 0.001 and p = 0.004), lymph node metastasis ( p = 0.001 and p < 0.001), and recurrence (both p < 0.001). Survival analysis demonstrated high iASPP expression significantly correlated with shorter disease-free survival (DFS) (both p < 0.001 for cytoplasmic and nuclear expression) and overall survival (OS) (both p < 0.001 for cytoplasmic and nuclear expression). Multivariate analysis revealed that cytoplasmic iASPP was the only independent prognostic factor for HNSCC patients. iASPP expression is elevated in HNSCC tissues and cell lines, which suggests iASPP may contribute to the malignant progression of HNSCC, and serves as a novel prognostic marker and a potential therapeutic target in HNSCC. [ABSTRACT FROM AUTHOR]

Abstract: iASPP was an inhibitory member of ASPP family and could specifically inhibit the apoptotic function of p53. iASPPsv was identified by our lab as the short isoform of iASPP, which encoded a 407aa protein and highly matched the carboxyl terminus of iASPP. In this study, iASPPsv was stably transfected into the breast cancer cell line MCF-7 by means of lentivirus to explore the effects of iASPPsv on biological functions of MCF-7. Thymocytes from iASPP/iASPPsv transgenic mice were also used to explore the effects of iASPP/iASPPsv on cell biological function. The results demonstrated that iASPPsv antagonized the growth inhibition induced by etoposide (VP-16) in MCF-7 cells. iASPPsv also down-regulated proapoptotic genes (Bax, Puma and Noxa) expression to inhibit apoptosis caused by VP-16. Moreover, iASPP and iASPPsv could both help the thymocytes of transgenic mice to resist the growth inhibition and apoptosis caused by dexamethasone (Dex) or VP-16. At the same time, DNA double strand break damage accumulated in either iASPPsv MCF-7 cells or iASPP/iASPPsv thymocytes. These findings showed that iAPSS/iASPPsv reduced the growth inhibition and apoptosis induced by Dex or VP-16, with DNA damage accumulating which might promote the pathogenesis and/or progression of cancer. [Copyright &y& Elsevier]

The ability to induce apoptosis is the most important tumor-suppression function of p53. Inhibitory member of apoptosis-stimulating protein of p53 family (iASPP) is an apoptotic-specific regulator of p53. iASPP suppresses apoptosis by inhibiting the transactivation function of p53 on the promoters of proapoptotic genes; however, the mechanism whereby iASPP influences apoptosis in tumor cells with mutant or deficient p53 has not been completely defined. In this study, we investigated the role of iASPP in the p63/p73 apoptosis pathway. iASPP inhibited apoptosis independently of p53 in tumor cells, mainly by inhibiting the transcriptional activity of p63/p73 on the promoters of proapoptotic genes. Because p63 and p73 are rarely mutated in human cancers, inhibiting the expression of endogenous iASPP may provide a useful strategy for restoring the apoptotic activity of p63 and p73 in human tumors with p53 loss or mutation. These results represent a promising new strategy for the treatment of cancers with non-wild-type p53. [ABSTRACT FROM AUTHOR]

iASPP is an evolutionally conserved inhibitory member of the ASPP (apoptosis-stimulating protein of p53) protein family. Overexpression of iASPP was observed in several types of human tumors, however, its role in tumorigenesis has not been fully clarified. To investigate the role of iASPP in human glioblastoma multiforme (GMB) progression, the authors employed lentivirus-mediated shRNA to silence endogenous iASPP expression and elucidated iASPP function by analysis of viability, colony formation, DNA synthesis, and cell cycle in p53-mutant glioblastoma cell line U251. iASPP was significantly and sustainably knocked down by iASPP-specific shRNA in U251 cells. Stable down-regulation of iASPP expression-induced cell proliferation inhibition and G0/G1 cell cycle arrest by down-regulation of cyclin D1 and up-regulation of p21. Thus, the findings not only provide a molecular basis for the role of iASPP in cell cycle progression of glioblastoma cells but also suggest a novel therapeutic target for the treatment of GBM. [ABSTRACT FROM AUTHOR]

The article explores the basis for the functional diversity of the ASPP protein family by examining the protein-binding regions of the ASPP proteins which contain the C-terminal ankyrin repeats and SH3 domains (ANK-SH3). It compares the full binding domains of ASPP proteins ASPP1, ASPP2 and iASPP and the binding sites between ASPP2 and apoptosis regulators p53, Bcl-2, and NFκB. The results showed electrostatic differences in binding interfaces between the pro- and anti-apoptotic proteins.

Abstract: Oncoprotein inhibitory member of the ASPP family (iASPP) is a key inhibitor of tumor suppressor p53. Our previous study revealed that the expression of iASPP in acute leukemia (AL) patients was higher than that of normal control which implied that iASPP might play an important role in the pathogenesis and/or disease progression of AL. In this study, the iASPP expression was blocked by RNA interference (RNAi) in two leukemic cell lines, Nalm6 and K562, to explore the effects of iASPP on leukemia cells. The results indicated that down-regulation of endogenous iASPP increased p53-dependent apoptosis of leukemia cells. Thus, iASPP could be a molecular target in leukemia therapy. [Copyright &y& Elsevier]

Abstract: In order to obtain a full-length expression plasmid for the p53 inhibitor protein, iASPP, fractional amplification was used to clone its full-length coding sequence (CDS) region. The amplified PCR product was then digested and inserted into the pMD19-T simple vector and subcloned into the pCDNA3.1(+) vector. A recombinant eukaryotic expression vector containing the complete CDS region of iASPP was successfully constructed. pcDNA3.1(+)/iASPP was able to express iASPP protein in an in vitro translation system and in cells. Its biological activity was verified using Western blotting, immunoprecipitation and cell apoptosis analysis. This successful preparation of a full-length iASPP expression plasmid lays the foundations for further studies on the function of iASPP. [Copyright &y& Elsevier]

ASPP family is proved to be apoptotic specific regulators of p53. Among them, iASPP acts as an inhibitor of p53. To investigate the effect of the iASPP RNAi on the apoptosis of breast cancer cell MCF-7, we transfected the recombinant plasmid PGCsilencer H1/Neo/GFP/RNAi into MCF-7. The iASPP expression was analyzed by RT-PCR and Western blot. The cell apoptosis was detected by FCM. The results show that the expression of iASPP is descended and the apoptosis rate is increased after transfection. Therefore, we conclude that inhibition of expression of iASPP may resume the ability of p53 to induce apoptosis in MCF-7 cells. [ABSTRACT FROM AUTHOR]

Abstract: The p53 protein family consists of three transcription factors: p53, p63, and p73. These proteins share significant structural and functional similarities and each has unique biological functions as well. Although the role of p53 in cellular stress is extensively studied, many questions remain about p63 and p73. In this review we summarize current data on functional interactions within the p53 family, their regulation and roles in response to genotoxic stress. We also discuss the significance of p73 and p63 for cancer therapy and outline novel approaches in development of therapeutic drugs that specifically target the p53 family. [Copyright &y& Elsevier]

Abstract: iASPP is an inhibitory member of ASPP (apoptosis stimulating protein of p53, or Ankyrin repeats, SH3 domain and proline-rich region contain Protein) family. As reported previously, it at least includes two isoforms, one is iASPP/RAI (351 amino acids, aa) and the other is iASPP (828 aa).Here, we identified a novel open reading frame of human iASPP, which encodes a 407 aa protein and highly matches with the C terminus of iASPP (828 aa, CAI60219). Hereafter, iASPP (407 aa) will be referred to as iASPP-SV (iASPP splice variant). In further study, we found that iASPP-SV is a nuclear protein, and is capable of binding to p53 in vivo. Moreover, overexpression of iASPP-SV can inhibit the transcriptional activity of p53 on the promoters of both Bax and p21. [Copyright &y& Elsevier]

ASPP1 and ASPP2 are both proteins that interact with p53 and enhance its ability to induce apoptosis by selectively elevating the expression of proapoptotic p53-responsive genes. iASPP(RAI) is a third member of the family that is the most conserved inhibitor of p53-mediated apoptosis. Here, we have described iASPP, a longer form of iASPP(RAI), which at 828 amino acids is more than twice the size of iASPP(RAI). Using two antibodies that recognize both iASPP and iASPP(RAI), we report that this longer form of iASPP is the predominant form of the molecule expressed in cells. Like iASPP(RAI), iASPP also binds to p53 and inhibits apoptosis induced by p53 overexpression. However, whereas iASPP(RAI) is predominantly nuclear, the N-terminus of iASPP is entirely cytoplasmic, and the longer iASPP is located in both the cytoplasm and the nucleus. The effect upon subcellular localization of the longer N-terminus of iASPP means that this new, longer form of the molecule may be subject to greater regulation and provides another layer in the control of p53-induced apoptosis.Oncogene (2004) 23, 9007-9016. doi:10.1038/sj.onc.1208088 Published online 18 October 2004 [ABSTRACT FROM AUTHOR]