iASPP and chemoresistance in ovarian cancers: effects on paclitaxel-mediated mitotic catastrophe

PAX2 mediated upregulation of ESPL1 contributes to cisplatin resistance in bladder cancer through activating the JAK2/STAT3 pathway

Extra spindle-polar body like 1 (ESPL1) is associated with the development of a variety of cancers, including bladder cancer, and is closely related to chemoresistance. In this study, we aimed to reveal the role of ESPL1 in bladder cancer progression and cisplatin (DDP) resistance. First, ESPL1 was found to be highly expressed in tumor tissues and cells of bladder cancer, and more highly expressed in cisplatin resistant tumor tissues or cells. The binding of PAX2 in ESPL1 promoter region was predicted by Jaspar database and verified by Ch-IP analysis and the luciferase reporter gene assay. Next, cisplatin-resistant T24 cells (T24/DDP) were established and transfected with ESPL1 siRNA (si-ESPL1) or overexpression vector (pcDNA-ESPL1) or co-transfected with PAX2 siRNA (si-PAX2) or overexpression vector (pcDNA-PAX2), and then treated with DDP or AG490, an inhibitor of JAK2. The results showed that silencing ESPL1 significantly reduced T24/DDP cell viability, colony formation and invasion, enhanced sensitivity to DDP, and induced cell apoptosis. Silencing PAX2 decreased ESPL1 expression, enhanced sensitivity to DDP, and induced apoptosis of T24/DDP cells, and inhibited activation of JAK2/STAT3 pathway. Overexpressing ESPL1 reversed the effect of PAX2 silencing on T24/DDP cells, while AG490 counteracted the reversal effect of overexpressing ESPL1. Finally, a xenograft tumor model was established and found that silencing ESPL1 or DDP treatment inhibited tumor growth, while silencing ESPL1 combined with DDP treatment had the best effect. In summary, this study suggested that PAX2-mediated ESPL1 transcriptional activation enhanced cisplatin resistance in bladder cancer by activating JAK2/STAT3 pathway.

Exploration of Verticillins in High-Grade Serous Ovarian Cancer and Evaluation of Multiple Formulations in Preclinical In Vitro and In Vivo Models

Verticillins are epipolythiodioxopiperazine alkaloids isolated from a fungus with nanomolar anti-tumor activity in high-grade serous ovarian cancer (HGSOC). HGSOC is the fifth leading cause of death in women, and natural products continue to be an inspiration for new drug entities to help tackle chemoresistance. Verticillin D was recently found in a new fungal strain and compared to verticillin A. Both compounds exhibited nanomolar cytotoxic activity against OVCAR4 and OVCAR8 HGSOC cell lines, significantly reduced 2D foci and 3D spheroids, and induced apoptosis. In addition, verticillin A and verticillin D reduced tumor burden in vivo using OVCAR8 xenografts in the peritoneal space as a model. Unfortunately, mice treated with verticillin D displayed signs of liver toxicity. Tolerability studies to optimize verticillin A formulation for in vivo delivery were performed and compared to a semi-synthetic succinate version of verticillin A to monitor bioavailability in athymic nude females. Formulation of verticillins achieved tolerable drug delivery. Thus, formulation studies are effective at improving tolerability and demonstrating efficacy for verticillins.

p53 inhibitor iASPP is an unexpected suppressor of KRAS and inflammation-driven pancreatic cancer

Oncogenic KRAS activation, inflammation and p53 mutation are key drivers of pancreatic cancer (PC) development. Here we report iASPP, an inhibitor of p53, as a paradoxical suppressor of inflammation and oncogenic KRAS^G12D-driven PC tumorigenesis. iASPP suppresses PC onset driven by KRAS^G12D alone or KRAS^G12D in combination with mutant p53^R172H. iASPP deletion limits acinar-to-ductal metaplasia (ADM) in vitro but accelerates inflammation and KRAS^G12D-induced ADM, pancreatitis and PC tumorigenesis in vivo. KRAS^G12D/iASPP^Δ8/Δ8 tumours are well-differentiated classical PCs and their derivative cell lines form subcutaneous tumours in syngeneic and nude mice. Transcriptomically, either iASPP deletion or p53 mutation in the KRAS^G12D background altered the expression of an extensively overlapping gene set, comprised primarily of NF-κB and AP1-regulated inflammatory genes. All these identify iASPP as a suppressor of inflammation and a p53-independent oncosuppressor of PC tumorigenesis.

Calcium homeostasis and cancer: insights from endoplasmic reticulum-centered organelle communications

Calcium ion (Ca²⁺) is a ubiquitous and versatile signaling molecule controlling a wide variety of cellular processes, such as proliferation, cell death, migration, and immune response, all fundamental processes essential for the establishment of cancer. In recent decades, the loss of Ca²⁺ homeostasis has been considered an important driving force in the initiation and progression of malignant diseases. The primary intracellular Ca²⁺ store, the endoplasmic reticulum (ER), plays an essential role in maintaining Ca²⁺ homeostasis by coordinating with other organelles and the plasma membrane. Here, we discuss the dysregulation of ER-centered Ca²⁺ homeostasis in cancer, summarize Ca²⁺-based anticancer therapeutics, and highlight the significance of furthering our understanding of Ca²⁺ homeostasis regulation in cancer.

Functional roles of long noncoding RNA MALAT1 in gynecologic cancers

Gynecologic cancers are reproductive disorders characterized by pelvic pain and infertility. The identification of new predictive markers and therapeutic targets for the treatment of gynecologic cancers is urgently necessary. One of the recent successes in gynecologic cancers research is identifying the role of signaling pathways in the pathogenesis of the disease. Recent experiments showed long noncoding RNAs (lncRNA) can be novel therapeutic approaches for the diagnosis and treatment of gynecologic cancers. LncRNA are transcribed RNA molecules that play pivotal roles in multiple biological processes by regulating the different steps of gene expression. Metastasis-associated lung adenocarcinoma transcript-1 (MALAT1) is a well-known lncRNA that plays functional roles in gene expression, RNA processing, and epigenetic regulation. High expression of MALAT1 is closely related to numerous human diseases. It is generally believed that MALAT1 expression is associated with cancer cell growth, autophagy, invasion, and metastasis. MALAT1 by targeting multiple signaling pathways and microRNAs (miRNAs) could contribute to the pathogenesis of gynecologic cancers. In this review, we will summarize functional roles of MALAT1 in the most common gynecologic cancers, including endometrium, breast, ovary, and cervix.

Chitosan-Gelatin-EGCG Nanoparticle-Meditated LncRNA TMEM44-AS1 Silencing to Activate the P53 Signaling Pathway for the Synergistic Reversal of 5-FU Resistance in Gastric Cancer

Chemoresistance is one of the leading causes of therapeutic failure in gastric cancer (GC) treatment. Recent studies have shown lncRNAs play pivotal roles in regulating GC chemoresistance. Nanocarriers delivery of small interfering RNAs (siRNAs) to silence cancer-related genes has become a novel approach to cancer treatment research. However, finding target genes and developing nanosystems capable of selectively delivering siRNAs for disease treatment remains a challenge. In this study, a novel lncRNA TMEM44-AS1 that is related to 5-FU resistance is identified. TMEM44-AS1 has the ability to bind to and sponge miR-2355-5p, resulting in the upregulated PPP1R13L expression and P53 pathway inhibition. Next, a new nanocarrier called chitosan-gelatin-EGCG (CGE) is developed, which has a higher gene silencing efficiency than lipo2000, to aid in the delivery of a si-TMEM44-AS1 can efficiently silence TMEM44-AS1 expression to synergistically reverse 5-FU resistance in GC, leading to a markedly enhanced 5-FU therapeutic effect in a xenograft mouse model of GC. These findings indicate that TMEM44-AS1 may estimate 5-FU therapy outcome among GC cases, and that systemic si-TMEM44-AS1 delivery combined with 5-FU therapy is significant in the treatment of patients with recurrent GC.

Mechanisms of cancer cell death induction by paclitaxel: an updated review

Chemoresistance of cancer cells is a major problem in treating cancer. Knowledge of how cancer cells may die or resist cancer drugs is critical to providing certain strategies to overcome tumour resistance to treatment. Paclitaxel is known as a chemotherapy drug that can suppress the proliferation of cancer cells by inducing cell cycle arrest and induction of mitotic catastrophe. However, today, it is well known that paclitaxel can induce multiple kinds of cell death in cancers. Besides the induction of mitotic catastrophe that occurs during mitosis, paclitaxel has been shown to induce the expression of several pro-apoptosis mediators. It also can modulate the activity of anti-apoptosis mediators. However, certain cell-killing mechanisms such as senescence and autophagy can increase resistance to paclitaxel. This review focuses on the mechanisms of cell death, including apoptosis, mitotic catastrophe, senescence, autophagic cell death, pyroptosis, etc., following paclitaxel treatment. In addition, mechanisms of resistance to cell death due to exposure to paclitaxel and the use of combinations to overcome drug resistance will be discussed.

Targeting Protein Interaction Hotspots Using Structured and Disordered Chimeric Peptide Inhibitors

The main challenge in inhibiting protein-protein interactions (PPI) for therapeutic purposes is designing molecules that bind specifically to the interaction hotspots. Adding to the complexity, such hotspots can be within both structured and disordered interaction interfaces. To address this, we present a strategy for inhibiting the structured and disordered hotspots of interactions using chimeric peptides that contain both structured and disordered parts. The chimeric peptides we developed are comprised of a cyclic structured part and a disordered part, which target both disordered and structured hotspots. We demonstrate our approach by developing peptide inhibitors for the interactions of the antiapoptotic iASPP protein. First, we developed a structured, α-helical stapled peptide inhibitor, derived from the N-terminal domain of MDM2. The peptide bound two hotspots on iASPP at the low micromolar range and had a cytotoxic effect on A2780 cancer cells with a half-maximal inhibitory concentration (IC₅₀) value of 10 ± 1 μM. We then developed chimeric peptides comprising the structured stapled helical peptide and the disordered p53-derived LinkTer peptide that we previously showed to inhibit iASPP by targeting its disordered RT loop. The chimeric peptide targeted both structured and disordered domains in iASPP with higher affinity compared to the individual structured and disordered peptides and caused cancer cell death. Our strategy overcomes the inherent difficulty in inhibiting the interactions of proteins that possess structured and disordered regions. It does so by using chimeric peptides derived from different interaction partners that together target a much wider interface covering both the structured and disordered domains. This paves the way for developing such inhibitors for therapeutic purposes.

Targeting regulated cell death (RCD) with small-molecule compounds in triple-negative breast cancer: a revisited perspective from molecular mechanisms to targeted therapies

Triple-negative breast cancer (TNBC) is a subtype of human breast cancer with one of the worst prognoses, with no targeted therapeutic strategies currently available. Regulated cell death (RCD), also known as programmed cell death (PCD), has been widely reported to have numerous links to the progression and therapy of many types of human cancer. Of note, RCD can be divided into numerous different subroutines, including autophagy-dependent cell death, apoptosis, mitotic catastrophe, necroptosis, ferroptosis, pyroptosis and anoikis. More recently, targeting the subroutines of RCD with small-molecule compounds has been emerging as a promising therapeutic strategy, which has rapidly progressed in the treatment of TNBC. Therefore, in this review, we focus on summarizing the molecular mechanisms of the above-mentioned seven major RCD subroutines related to TNBC and the latest progress of small-molecule compounds targeting different RCD subroutines. Moreover, we further discuss the combined strategies of one drug (e.g., narciclasine) or more drugs (e.g., torin-1 combined with chloroquine) to achieve the therapeutic potential on TNBC by regulating RCD subroutines. More importantly, we demonstrate several small-molecule compounds (e.g., ONC201 and NCT03733119) by targeting the subroutines of RCD in TNBC clinical trials. Taken together, these findings will provide a clue on illuminating more actionable low-hanging-fruit druggable targets and candidate small-molecule drugs for potential RCD-related TNBC therapies.

iASPP is essential for HIF-1α stabilization to promote angiogenesis and glycolysis via attenuating VHL-mediated protein degradation

Hypoxia-inducible factor-1α (HIF-1α) plays central roles in the hypoxia response. It is highly expressed in multiple cancers, but not always correlated with hypoxia. Mutation of the von Hippel-Lindau (VHL) gene, which encodes an E3 ligase, contributes to the constructive activation of HIF-1α in specific tumor types, as exemplified by renal cell carcinoma; but how VHL wild-type tumors acquire this ability is not completely understood. Here, we found that the oncogene iASPP (inhibitor of apoptosis-simulating protein of p53) plays essential roles in such a context. Genetic inhibition of iASPP reduced tumor growth, accompanied by impaired angiogenesis, increased areas of tumor necrosis, and reduced glycolysis that was HIF-1α-dependent. These abilities of iASPP were validated by in vitro assays. Mechanistically, iASPP directly binds VHL at its β domain, a region also involved in HIF-1α binding, therefore blocking VHL's binding and the subsequent degradation of HIF-1α protein under normoxia. iASPP levels correlate with HIF-1α protein and vascular endothelial growth factor (VEGF) and the glucose transporter protein type 1(GLUT1), representative HIF-1α target genes, in human colon cancer tissues. Furthermore, inhibition of iASPP expression synergizes with low toxic dose of the HIF-1α inhibitor YC-1 to inhibit HIF-1α expression and tumor growth. Our findings suggest that iASPP contributes to HIF-1α activation in cancers, and that iASPP-mediated HIF-1α stabilization has potential as a therapeutic approach against cancer.

iASPP suppresses Gp78-mediated TMCO1 degradation to maintain Ca2+ homeostasis and control tumor growth and drug resistance

Accumulating preclinical and clinical evidence has supported a central role for alterations in Ca²⁺ homeostasis in the development of cancer. TMCO1 protein is an identified Ca²⁺-channel protein, while its roles in cancer remain obscure. Here, we found that TMCO1 is increased in colon cancer tissues. In addition, it is a substrate of E3 ligase Gp78. Enhanced oncogene iASPP stabilizes TMCO1 by competitively binding with Gp78. Inhibition of iASPP-TMCO1 sensitizes cancer cells’ response to Ca²⁺-induced apoptosis. This study has improved our fundamental understanding of the Ca²⁺ homeostasis in cancer cells. iASPP-TMCO1 axis may present a promising therapeutic target that can combine the conventional drugs to reinforce Ca²⁺-dependent apoptosis.

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.

iASPP contributes to cell cortex rigidity, mitotic cell rounding, and spindle positioning

iASPP is a protein mostly known as an inhibitor of p53 pro-apoptotic activity and a predicted regulatory subunit of the PP1 phosphatase, which is often overexpressed in tumors. We report that iASPP associates with the microtubule plus-end binding protein EB1, a central regulator of microtubule dynamics, via an SxIP motif. iASPP silencing or mutation of the SxIP motif led to defective microtubule capture at the cortex of mitotic cells, leading to abnormal positioning of the mitotic spindle. These effects were recapitulated by the knockdown of the membrane-to-cortex linker Myosin-Ic (Myo1c), which we identified as a novel partner of iASPP. Moreover, iASPP or Myo1c knockdown cells failed to round up upon mitosis because of defective cortical stiffness. We propose that by increasing cortical rigidity, iASPP helps cancer cells maintain a spherical geometry suitable for proper mitotic spindle positioning and chromosome partitioning.

Centrosome Aberrations as Drivers of Chromosomal Instability in Breast Cancer

Chromosomal instability (CIN), or the dynamic change in chromosome number and composition, has been observed in cancer for decades. Recently, this phenomenon has been implicated as facilitating the acquisition of cancer hallmarks and enabling the formation of aggressive disease. Hence, CIN has the potential to serve as a therapeutic target for a wide range of cancers. CIN in cancer often occurs as a result of disrupting key regulators of mitotic fidelity and faithful chromosome segregation. As a consequence of their essential roles in mitosis, dysfunctional centrosomes can induce and maintain CIN. Centrosome defects are common in breast cancer, a heterogeneous disease characterized by high CIN. These defects include amplification, structural defects, and loss of primary cilium nucleation. Recent studies have begun to illuminate the ability of centrosome aberrations to instigate genomic flux in breast cancer cells and the tumor evolution associated with aggressive disease and poor patient outcomes. Here, we review the role of CIN in breast cancer, the processes by which centrosome defects contribute to CIN in this disease, and the emerging therapeutic approaches that are being developed to capitalize upon such aberrations.

Upregulation of iASPP ameliorates hypoxia/reoxygenation-induced apoptosis and oxidative stress in cardiomyocytes by upregulating Nrf2 signaling

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.

iASPP-Mediated ROS Inhibition Drives 5-Fu Resistance Dependent on Nrf2 Antioxidative Signaling Pathway in Gastric Adenocarcinoma

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.

Targeting an Interaction Between Two Disordered Domains by Using a Designed Peptide

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.

Increases of iASPP-Keap1 interaction mediated by syringin enhance synaptic plasticity and rescue cognitive impairments via stabilizing Nrf2 in Alzheimer's models

Oxidative stress is an important pathogenic manifestation of Alzheimer's disease (AD) that contributes to synaptic dysfunction, which precedes Aβ accumulation and neurofibrillary tangle formation. However, the molecular machineries that govern the decline of antioxidative defence in AD remains to be elucidated, and effective candidate for AD treatment is limited. Here, we showed that the decreases in the inhibitor of apoptosis-stimulating protein of p53 (iASPP) was associated with the vulnerability to oxidative stress in the amyloid precursor protein (APP)/presenilin 1 (PS1) mouse brain. Treatment with an antioxidant, syringin, could ameliorate AD-related pathologic and behavioural impairments. Interestingly, syringin treatment resulted in an upregulation of iASPP and the increase in the interaction of iASPP with Kelchlike ECH-associating protein 1 (Keap1). Syringin reduced neuronal apoptosis independently of p53. We confirmed that syringin-induced enhancement of antioxidant defenses involved the stabilization of Nrf2 in overexpressing human Swedish mutant APP (APPswe) cells in vitro. Syringin-mediated Nrf2 nuclear translocation facilitated the activation of the Nrf2 downstream genes via iASPP/Nrf2 axis. Our results demonstrate that syringin-mediated increases of iASPP-Keap1 interaction restore cellular redox balance. Further study on the syringin-iASPP interactions may help in understanding the regulatory mechanism and designing novel potent modulators for AD treatment.

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Poor expression of iASPP is associated with the serious accumulation of β-amyloid.

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Syringin reduces Aβ production and mitigates cognitive deficits by amending redox.

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Syringin-caused increases of iASPP facilitate the activation of NADPH and γGCL-C.

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Syringin protects neuronal cells against oxidative stress via iASPP/Nrf2 axis.

LncRNA XIST Promotes Growth of Human Chordoma Cells by Regulating miR-124-3p/iASPP Pathway

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.

Overexpression of iASPP is required for autophagy in response to oxidative stress in choriocarcinoma

Background

Gestational trophoblastic disease (GTD) is a heterogeneous group of diseases developed from trophoblasts. ASPP (Ankyrin-repeat, SH3-domain and proline-rich region containing protein) family proteins, ASPP1 and ASPP2, have been reported to be dysregulated in GTD. They modulate p53 activities and are responsible for multiple cellular processes. Nevertheless, the functional role of the ASPP family inhibitory member, iASPP, is not well characterized in GTD.

Methods

To study the functional role of iASPP in GTD, trophoblastic tissues from normal placentas, hydatidiform mole (HM) and choriocarcinoma were used for immunohistochemistry, whereas siRNAs were used to manipulate iASPP expression in choriocarcinoma cell lines and study the subsequent molecular changes.

Results

We demonstrated that iASPP was overexpressed in both HM and choriocarcinoma when compared to normal placenta. Progressive increase in iASPP expression from HM to choriocarcinoma suggests that iASPP may be related to the development of trophoblastic malignancy. High iASPP expression in HM was also significantly associated with a high expression of autophagy-related protein LC3. Interestingly, iASPP silencing retarded the growth of choriocarcinoma through senescence instead of induction of apoptosis. LC3 expression decreased once iASPP was knocked down, suggesting a downregulation on autophagy. This may be due to iASPP downregulation rendered decrease in Atg5 expression and concomitantly hindered autophagy in choriocarcinoma cells. Autophagy inhibition per se had no effect on the growth of choriocarcinoma cells but increased the susceptibility of choriocarcinoma cells to oxidative stress, implying a protective role of iASPP against oxidative stress through autophagy in choriocarcinoma.

Conclusions

iASPP regulates growth and the cellular responses towards oxidative stress in choriocarcinoma cells. Its overexpression is advantageous to the pathogenesis of GTD. (266 words).

Downregulation of iASPP Expression Suppresses Proliferation, Invasion and Increases Chemosensitivity to Paclitaxel of Head and Neck Squamous Cell Carcinoma In Vitro

Objective 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. Methods 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. Results 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 shRNA-NC 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). Conclusion 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.

Antioxidant Defenses: A Context-Specific Vulnerability of Cancer Cells

Reactive oxygen species (ROS) are well known for their capacity to cause DNA damage, augment mutagenesis, and thereby promote oncogenic transformation. Similarly, agents that reduce ROS levels (antioxidants) are frequently thought to have anti-cancer properties given their propensity to minimize DNA damage and mutagenesis. However, numerous clinical studies focused on antioxidants suggest that this is a facile premise and that antioxidant capacity can be important for cancer cells in a similar fashion to normal cells. As a consequence of this realization, numerous laboratories have been motivated to investigate the biological underpinnings explaining how and when antioxidant activity can potentially be beneficial to cancer cells. Relatedly, it has become clear that the reliance of cancer cells on antioxidant activity in certain contexts represents a potential vulnerability that could be exploited for therapeutic gain. Here, we review some of the recent, exciting findings documenting how cancer cells utilized antioxidant activity and under what circumstances this activity could represent an opportunity for selective elimination of cancer cells.

The anti-apoptotic proteins NAF-1 and iASPP interact to drive apoptosis in cancer cells

We reveal a novel interaction between the two anti-apoptotic proteins iASPP and NAF-1, which are overexpressed in many types of cancer cells, and propose that this interaction is required for apoptosis activation in cancer cells. A peptide derived from the interaction interface inhibits apoptosis in cells.

Suppression of apoptosis is a key Hallmark of cancer cells, and reactivation of apoptosis is a major avenue for cancer therapy. We reveal an interaction between the two anti-apoptotic proteins iASPP and NAF-1, which are overexpressed in many types of cancer cells and tumors. iASPP is an inhibitory member of the ASPP protein family, whereas NAF-1 belongs to the NEET 2Fe–2S protein family. We show that the two proteins are stimulated to interact in cells during apoptosis. Using peptide array screening and computational methods we mapped the interaction interfaces of both proteins to residues 764–778 of iASPP that bind to a surface groove of NAF-1. A peptide corresponding to the iASPP 764–780 sequence stabilized the NAF-1 cluster, inhibited NAF-1 interaction with iASPP, and inhibited staurosporine-induced apoptosis activation in human breast cancer, as well as in PC-3 prostate cancer cells in which p53 is inactive. The iASPP 764–780 IC₅₀ value for inhibition of cell death in breast cancer cells was 13 ± 1 μM. The level of cell death inhibition by iASPP 764–780 was altered in breast cancer cells expressing different levels and/or variants of NAF-1, indicating that the peptide activity is associated with NAF-1 function. We propose that the interaction between iASPP and NAF-1 is required for apoptosis activation in cancer cells. This interaction uncovers a new layer in the highly complex regulation of cell death in cancer cells and opens new avenues of exploration into the development of novel anticancer drugs that reactivate apoptosis in malignant tumors.

Impact of iASPP on chemoresistance through PLK1 and autophagy in ovarian clear cell carcinoma

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.

IGF2 mRNA binding protein 3 (IMP3) mediated regulation of transcriptome and translatome in glioma cells

RNA binding proteins mediate global regulation at the level of transcriptome and translatome of a cell. We studied the global level expression changes regulated by IMP3 in transcriptome and translatome by performing microarray using total cellular RNA and heavy polysome derived RNA of IMP3 silenced glioma cells respectively. Differentially regulated transcripts at the transcriptome level (n = 2388) and at the level of translatome (n = 479) were identified. Further, these transcripts were classified as direct and indirect targets on the basis of presence of IMP3 binding site. Additional investigation revealed that direct targets at transcriptome level were found to be associated with processes related to cell cycle, whereas direct targets at the translatome level participated in apoptosis related pathways. Probable mechanism of indirect regulation at both the levels is also investigated. Collectively, our study reveals multi-level gene expression regulation imposed by IMP3 in glioma cells.

Sertad1 antagonizes iASPP function by hindering its entrance into nuclei to interact with P53 in leukemic cells

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 iASPP^hi 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.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3787-2) contains supplementary material, which is available to authorized users.

Downregulation of Inhibition of Apoptosis-Stimulating Protein of p53 (iASPP) Suppresses Cisplatin-Resistant Gastric Carcinoma In Vitro

BACKGROUND Gastric cancer (GC) with cisplatin resistance is one of the leading causes of limitations to therapy. Inhibition of apoptosis-stimulating protein of p53 (iASPP) plays a key role in GC. However, the role of iASPP in GC with cisplatin resistance remains unclear. The aim of this study was to investigate iASPP expression in GC, and the functions of iASPP in cisplatin-resistant cell lines. MATERIAL AND METHODS In this study, the expression of iASPP was investigated in normal GC patients and patients with cisplatin resistance, along with GC cell lines and cell lines with cisplatin resistance. Furthermore, knockdown of iASPP was conducted in cell lines; and cell proliferation, apoptosis rate, cell cycle distribution, and cell migration and invasion were determined through CCK8, flow cytometry, Scratch test and Transwell assay, respectively. RESULTS The expression of iASPP in GC patients with cisplatin resistance was significant higher than in the health control group. Higher expression of iASPP was detected in cisplatin-resistant cancer cell lines. Cell proliferation of SGC-7901 and MGC-803 was inhibited by transfection with siRNA, along with evaluated apoptosis rate and G1 phase retardant. Furthermore, cells viability, including migration and invasion, was suppressed post-transfection with siRNA. CONCLUSIONS iASPP induced cisplatin resistance in GC patients. Thus, knockdown of iASPP might be a novel therapeutic strategy for the treatment of GC cisplatin-resistant patients.

iASPP Is an Antioxidative Factor and Drives Cancer Growth and Drug Resistance by Competing with Nrf2 for Keap1 Binding

Reactive oxygen species (ROS) have emerged as important signaling molecules that play crucial roles in carcinogenesis and cytotoxic responses. Nrf2 is the master regulator of ROS balance. Thus, uncovering mechanisms of Nrf2 regulation is important for the development of alternative treatment strategies for cancers. Here, we demonstrate that iASPP, a known p53 inhibitor, lowers ROS independently of p53. Mechanistically, iASPP competes with Nrf2 for Keap1 binding via a DLT motif, leading to decreased Nrf2 ubiquitination and increased Nrf2 accumulation, nuclear translocation, and antioxidative transactivation. This iASPP-Keap1-Nrf2 axis promotes cancer growth and drug resistance both in vitro and in vivo. Thus, iASPP is an antioxidative factor and represents a promising target to improve cancer treatment, regardless of p53 status.

iASPP facilitates tumor growth by promoting mTOR-dependent autophagy in human non-small-cell lung cancer

Autophagy serves a critical function in the pathogenesis, response to therapy and clinical outcome in cancers. Although a recent report showed a role of iASPP in suppressing autophagy, its potential activity as a regulator of autophagy has not been investigated in lung cancer. Here we investigated the potential function and molecular mechanism of iASPP in mediating autophagy in human non-small-cell lung cancer. Our data suggested that forced expression of iASPP triggered autophagic flux, while inhibition of iASPP suppressed autophagy at the autophagsome formation stage in vitro. Furthermore, in vivo overexpression of iASPP in SCID/NOD mice promoted tumorigenesis and autophagy, with an increase in the conversion from LC3-I to LC3-II. The effects of iASPP were mediated through activation of mTOR pathway. Finally, cytoplasmic iASPP expression was upregulated in lung cancer patients, and was identified as an independent poor prognostic factor for lung cancer-specific death in patient samples. Taken together, our data showed that iASPP could promote tumor growth by increasing autophagic flux, and iASPP could serve as a poor prognostic factor and a potential therapeutic target in lung cancer.

Sequence variation in PPP1R13L results in a novel form of cardio-cutaneous syndrome

Dilated cardiomyopathy (DCM) is a life-threatening disorder whose genetic basis is heterogeneous and mostly unknown. Five Arab Christian infants, aged 4-30 months from four families, were diagnosed with DCM associated with mild skin, teeth, and hair abnormalities. All passed away before age 3. A homozygous sequence variation creating a premature stop codon at PPP1R13L encoding the iASPP protein was identified in three infants and in the mother of the other two. Patients' fibroblasts and PPP1R13L-knocked down human fibroblasts presented higher expression levels of pro-inflammatory cytokine genes in response to lipopolysaccharide, as well as Ppp1r13l-knocked down murine cardiomyocytes and hearts of Ppp1r13l-deficient mice. The hypersensitivity to lipopolysaccharide was NF-κB-dependent, and its inducible binding activity to promoters of pro-inflammatory cytokine genes was elevated in patients' fibroblasts. RNA sequencing of Ppp1r13l-knocked down murine cardiomyocytes and of hearts derived from different stages of DCM development in Ppp1r13l-deficient mice revealed the crucial role of iASPP in dampening cardiac inflammatory response. Our results determined PPP1R13L as the gene underlying a novel autosomal-recessive cardio-cutaneous syndrome in humans and strongly suggest that the fatal DCM during infancy is a consequence of failure to regulate transcriptional pathways necessary for tuning cardiac threshold response to common inflammatory stressors.

Mitotic Vulnerability in Triple-Negative Breast Cancer Associated with LIN9 Is Targetable with BET Inhibitors

Triple-negative breast cancers (TNBC) are highly aggressive, lack FDA-approved targeted therapies, and frequently recur, making the discovery of novel therapeutic targets for this disease imperative. Our previous analysis of the molecular mechanisms of action of bromodomain and extraterminal protein inhibitors (BETi) in TNBC revealed these drugs cause multinucleation, indicating BET proteins are essential for efficient mitosis and cytokinesis. Here, using live cell imaging, we show that BET inhibition prolonged mitotic progression and induced mitotic cell death, both of which are indicative of mitotic catastrophe. Mechanistically, the mitosis regulator LIN9 was a direct target of BET proteins that mediated the effects of BET proteins on mitosis in TNBC. Although BETi have been proposed to function by dismantling super-enhancers (SE), the LIN9 gene lacks an SE but was amplified or overexpressed in the majority of TNBCs. In addition, its mRNA expression predicted poor outcome across breast cancer subtypes. Together, these results provide a mechanism for cancer selectivity of BETi that extends beyond modulation of SE-associated genes and suggest that cancers dependent upon LIN9 overexpression may be particularly vulnerable to BETi. Cancer Res; 77(19); 5395-408. ©2017 AACR.

iASPP overexpression is associated with clinical outcome in spinal chordoma and influences cellular proliferation, invasion, and sensitivity to cisplatin in vitro

The oncogenetic function of inhibitory member of the apoptosis stimulating protein of p53 family (iASPP) in chordoma is unclear and remains to elucidate. The expression of iASPP in chordoma tissues and cells, its correlation to clinicopathological parameters and the effect on the patients’ prognosis were evaluated. Cellular proliferation, invasion and cisplatin-response were observed after the iASPP knockdown or overexpression in vitro. Co-Immunoprecipitation assay was used to explore the interaction between iASPP and p53. The regulation of miRNA-124 on the expression and apoptotic function of iASPP was explored after transiently transfecting cells with miRNA-124 mimics or inhibitor. Results indicated that iASPP overexpressed in chordoma tissues and cells. Its overexpression was associated with tumor invasion and local recurrence, and was predictive of patients’ poor prognosis. Cells with iASPP-silence showed a decreased ability of proliferation and invasion, but an increasing sensitivity to cisplatin. Besides, iASPP could combine with p53 in either endogenous or exogenous detection. Post-transcriptionally, miRNA-124 negatively regulated the expression of iASPP, which further led to the changes of apoptosis-related proteins. Thus, iASPP overexpression is associated with the clinical outcome in spinal chordoma and influences cellular proliferation, invasion, and the sensitivity to cisplatin.

Inhibitory member of the apoptosis-stimulating protein of p53 is overexpressed in bladder cancer and correlated to its progression

Several lines of direct evidence show that inhibitory member of the apoptosis-stimulating protein of p53 (iASPP) has an important function in cancer progression. However, its expression pattern and relationship with clinical pathologic characteristics in bladder cancer (BC) have not been completely elucidated. In this study, firstly, samples from 3 patients with invasive BC were detected by liquid chromatography tandem mass spectrometry to confirm overexpression of iASPP in BC, then samples from patients with noninvasive and invasive BC were detected by real-time polymerase chain reaction, Western blot, and tissue microarry immunohistochemistry. The relationship between iASPP expression and various clinicopathological features was investigated. The results showed m-RNA and protein of iASPP were overexpressed in BC and the rate of iASPP-positive cells was positively correlated with Union for International Cancer Control-Tumor, Node, Metastases stage, histologic grade, lymph node metastasis and poor overall survive. The data demonstrate that iASPP is overexpressed in BC and promotes the malignancy of BC. iASPP maybe serve as a potential therapeutic target for BC.

iASPP induces EMT and cisplatin resistance in human cervical cancer through miR-20a-FBXL5/BTG3 signaling

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.

Long noncoding RNA MALAT1-regulated microRNA 506 modulates ovarian cancer growth by targeting iASPP

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.

Knockdown of cathepsin L sensitizes ovarian cancer cells to chemotherapy

Ovarian cancer is a leading gynecological malignancy associated with high mortality. The development of acquired drug resistance is the primary cause of chemotherapy failure in the treatment of ovarian cancer. To examine the mechanism underlying paclitaxel resistance in ovarian cancer and attempt to reverse it, the present study induced a TAX-resistant ovarian cancer cell line, SKOV3/TAX. Cathepsin L (CTSL) has been found to be overexpressed in ovarian cancer. The aim of the present study was to investigate the possible involvement of CTSL in the development of TAX resistance in ovarian cancer. CTSL expression was knocked down in SKOV3 ovarian cancer cells and their phenotypic changes were analyzed. The effects of silenced CTSL on the resistant cell line were investigated by proliferation and apoptosis analysis compared with control SKOV3 cells. CTSL was more highly expressed in SKOV3/TAX cells compared with SKOV3 cells. Paclitaxel treatment downregulated the expression of CTSL in SKOV-3 but not in the paclitaxel-resistant SKOV3/TAX cells. CTSL small hairpin RNA (shRNA) knockdown significantly potentiated apoptosis induced by paclitaxel compared with SKOV3/TAX cells transfected with control shRNA, suggesting that CTSL contributes to paclitaxel resistance in ovarian cancer cells and that CTSL silencing can enhance paclitaxel-mediated cell apoptosis. Thus, CTSL should be explored as a candidate of therapeutic target for modulating paclitaxel sensitivity in ovarian cancer.

Genome-wide DNA methylation analysis of transient neonatal diabetes type 1 patients with mutations in ZFP57

Background

Transient neonatal diabetes mellitus 1 (TNDM1) is a rare imprinting disorder characterized by intrautering growth retardation and diabetes mellitus usually presenting within the first six weeks of life and resolves by the age of 18 months. However, patients have an increased risk of developing diabetes mellitus type 2 later in life. Transient neonatal diabetes mellitus 1 is caused by overexpression of the maternally imprinted genes PLAGL1 and HYMAI on chromosome 6q24. One of the mechanisms leading to overexpression of the locus is hypomethylation of the maternal allele of PLAGL1 and HYMAI. A subset of patients with maternal hypomethylation at PLAGL1 have hypomethylation at additional imprinted loci throughout the genome, including GRB10, ZIM2 (PEG3), MEST (PEG1), KCNQ1OT1 and NESPAS (GNAS-AS1). About half of the TNDM1 patients carry mutations in ZFP57, a transcription factor involved in establishment and maintenance of methylation of imprinted loci. Our objective was to investigate whether additional regions are aberrantly methylated in ZFP57 mutation carriers.

Methods

Genome-wide DNA methylation analysis was performed on four individuals with homozygous or compound heterozygous ZFP57 mutations, three relatives with heterozygous ZFP57 mutations and five controls. Methylation status of selected regions showing aberrant methylation in the patients was verified using bisulfite-sequencing.

Results

We found large variability among the patients concerning the number and identity of the differentially methylated regions, but more than 60 regions were aberrantly methylated in two or more patients and a novel region within PPP1R13L was found to be hypomethylated in all the patients. The hypomethylated regions in common between the patients are enriched for the ZFP57 DNA binding motif.

Conclusions

We have expanded the epimutational spectrum of TNDM1 associated with ZFP57 mutations and found one novel region within PPP1R13L which is hypomethylated in all TNDM1 patients included in this study. Functional studies of the locus might provide further insight into the etiology of the disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-016-0292-4) contains supplementary material, which is available to authorized users.

Tumor suppressor genes and their underlying interactions in paclitaxel resistance in cancer therapy

Objectives

Paclitaxel (PTX) is frequently used in the clinical treatment of solid tumors. But the PTX-resistance is a great obstacle in cancer treatment. Exploration of the mechanisms of drug resistance suggests that tumor suppressor genes (TSGs) play a key role in the response of chemotherapeutic drugs. TSGs, a set of genes that are often inactivated in cancers, can regulate various biological processes. In this study, an overview of the contribution of TSGs to PTX resistance and their underlying relationship in cancers are reported by using GeneMANIA, a web-based tool for gene/protein function prediction.

Methods

Using PubMed online database and Google web site, the terms “paclitaxel resistance” or “taxol resistance” or “drug resistance” or “chemotherapy resistance”, and “cancer” or “carcinoma”, and “tumor suppressor genes” or “TSGs” or “negative regulated protein” or “antioncogenes” were searched and analyzed. GeneMANIA data base was used to predict gene/protein interactions and functions.

Results

We identified 22 TSGs involved in PTX resistance, including BRCA1, TP53, PTEN, APC, CDKN1A, CDKN2A, HIN-1, RASSF1, YAP, ING4, PLK2, FBW7, BLU, LZTS1, REST, FADD, PDCD4, TGFBI, ING1, Bax, PinX1 and hEx. The TSGs were found to have direct and indirect relationships with each other, and thus they could contribute to PTX resistance as a group. The varied expression status and regulation function of the TSGs on cell cycle in different cancers might play an important role in PTX resistance.

Conclusion

A further understanding of the roles of tumor suppressor genes in drug resistance is an important step to overcome chemotherapy tolerance. Tumor suppressor gene therapy targets the altered genes and signaling pathways and can be a new strategy to reverse chemotherapy resistance.

Caspase cleavage of iASPP potentiates its ability to inhibit p53 and NF-κB

An intriguing biological question relating to cell signaling is how the inflammatory mediator NF-kB and the tumour suppressor protein p53 can be induced by similar triggers, like DNA damage or infection, yet have seemingly opposing or sometimes cooperative biological functions. For example, the NF-κB subunit RelA/p65 has been shown to inhibit apoptosis, whereas p53 induces apoptosis. One potential explanation may be their co-regulation by common cellular factors: inhibitor of Apoptosis Stimulating p53 Protein (iASPP) is one such common regulator of both RelA/p65 and p53. Here we show that iASPP is a novel substrate of caspases in response to apoptotic stimuli. Caspase cleaves the N-terminal region of iASPP at SSLD294 resulting in a prominent 80kDa fragment of iASPP. This caspase cleavage site is conserved in various species from zebrafish to Homo sapiens. The 80kDa fragment of iASPP translocates from the cytoplasm to the nucleus via the RaDAR nuclear import pathway, independent of p53. The 80kDa iASPP fragment can bind and inhibit p53 or RelA/p65 more efficiently than full-length iASPP. Overall, these data reveal a potential novel regulation of p53 and RelA/p65 activities in response to apoptotic stimuli.

Mitotic catastrophe and cancer drug resistance: A link that must to be broken

An increased tendency of genomic alterations during the life cycle of cells leads to genomic instability, which is a major driving force for tumorigenesis. A considerable fraction of tumor cells are tetraploid or aneuploid, which renders them intrinsically susceptible to mitotic aberrations, and hence, are particularly sensitive to the induction of mitotic catastrophe. Resistance to cell death is also closely linked to genomic instability, as it enables malignant cells to expand even in a stressful environment. Currently it is known that cells can die via multiple mechanisms. Mitotic catastrophe represents a step preceding apoptosis or necrosis, depending on the expression and/or proper function of several proteins. Mitotic catastrophe was proposed to be an onco-suppressive mechanism and the evasion of mitotic catastrophe constitutes one of the gateways to cancer development. Thus, stimulation of mitotic catastrophe appears to be a promising strategy in cancer treatment. Indeed, several chemotherapeutic drugs are currently used at concentrations that induce apoptosis irrespective of the cell cycle phase, yet are very efficient at triggering mitotic catastrophe at lower doses, significantly limiting side effects. In the present review we summarize current data concerning the role of mitotic catastrophe in cancer drug resistance and discuss novel strategies to break this link.

Reactivating p53 functions by suppressing its novel inhibitor iASPP: a potential therapeutic opportunity in p53 wild-type tumors

Although mutational inactivation of p53 is found in 50% of all human tumors, a subset of tumors display defective p53 function, but retain wild-type (WT) p53. Here, direct and indirect mechanisms leading to the loss of WT p53 activities are discussed. We summarize the oncogenic roles of iASPP, an inhibitor of WT p53, in promoting proliferation, invasion, drug or radiation-resistance and metastasis. From the therapeutic view, we highlight promising perspectives of microRNA-124, peptide and small molecules that reduce or block iASPP for the treatment of cancer. High iASPP expression enhances proliferation, aggressive behavior, the resistance to radiation/chemotherapy and correlates with poor prognosis in a range of human tumors. Overexpression of iASPP accelerates tumorigenesis and invasion through p53-dependent and p53-independent mechanisms. MicroRNA-124 directly targets iASPP and represses the growth and invasiveness of cancer cells. The disruption of iASPP-p53 interaction by a p53-derived peptide A34 restores p53 function in cancer cells. The inhibition of iASPP phosphorylation with small molecules induces p53-dependent apoptosis and growth suppression. The mechanisms underlying aberrant expression of iASPP in human tumors should be further investigated. Reactivating WT p53 functions by targeting its novel inhibitor iASPP holds promise for potential therapeutic interventions in the treatment of WT p53-containing tumors.

p21-Activated Kinases 1, 2 and 4 in Endometrial Cancers: Effects on Clinical Outcomes and Cell Proliferation

p21-activated kinases (Paks) are serine/threonine protein kinases involved in biological events linked to malignant tumor progression. In this study, expression of Pak1, p-Pak2 Ser²⁰, Pak4, pPak4 Ser⁴⁷⁴ in 21 normal endometrium, 16 hyperplastic endometrium without atypia, 17 atypical complex hyperplasia and 67 endometrial cancers was assessed by immunohistochemistry and correlated with clinicopathological parameters. We also accessed the proliferative role and downstream targets of Pak1 in endometrial cancer. Pak1 was expressed in cytoplasm whereas Pak4 and p-Pak4 were expressed in both cytoplasm and nucleus of endometrial tissues. In normal endometrium, significantly higher Pak1 (P = 0.028) and cytoplasmic p-Pak2 (P = 0.048) expression was detected in proliferative endometrium than secretory endometrium. Pak1, cytoplasmic and nuclear Pak4 and nuclear p-Pak4 was significantly overexpressed in endometrial cancer when compared to atrophic endometrium (all P<0.05). Moreover, type I endometrioid carcinomas showed significantly higher Pak1 expression than type II non-endometrioid carcinomas (P<0.001). On the other hand, Pak1, Pak4 and p-Pak4 expression negatively correlated with histological grade (all P<0.05) while p-Pak2 and cytoplasmic Pak4 expression inversely correlated with myometrial invasion (all P<0.05). Furthermore, patients with endometrial cancers with lower cytoplasmic Pak4 expression showed poorer survival (P = 0.026). Multivariate analysis showed cytoplasmic Pak4 is an independent prognostic factor. Functionally, knockdown of Pak1, but not Pak4, in endometrial cancer cell line led to reduced cell proliferation along with reduced cyclin D1, estrogen receptor (ERα) and progestogen receptor (PR) expression. Significant correlation between Pak1 and PR expression was also detected in clinical samples. Our findings suggest that Pak1 and cytoplasmic p-Pak2 may promote cell proliferation in normal endometrium during menstral cycle. Pak1, cytoplasmic and nuclear Pak4 and nuclear p-Pak4 are involved in the pathogenesis of endometrial cancer especially in postmenopausal women. Pak1 promote endometrial cancer cell proliferation, particular in type I endometrioid carcinoma. Cytoplasmic Pak4 can be potential prognostic marker in endometrial cancer.

Overexpression of SOX2 is involved in paclitaxel resistance of ovarian cancer via the PI3K/Akt pathway

Paclitaxel is recommended as a first-line chemotherapeutic agent against ovarian cancer, but drug resistance becomes a major limitation of its success clinically. The key molecule or mechanism associated with paclitaxel resistance in ovarian cancer still remains unclear. Sex-determining region Y-box 2 (SOX2) is of vital importance in the regulation of stem cell proliferation and carcinogenesis. The aim of this study was to evaluate the role of SOX2 in ovarian cancer tumorigenesis and paclitaxel resistance. In the present study, the expression of SOX2 was examined by immunohistochemistry (IHC) and real-time PCR in 40 clinical samples and in SKOV3 cells and SKOV3/TAX cells (paclitaxel-resistant human ovarian adenocarcinoma cell line). The effects of SOX2 knockdown on ovarian cancer cell proliferation, migration, and invasion were also studied. The IHC and real-time PCR results showed that the difference of SOX2 expression between ovarian cancer and the adjacent non-tumorous ovarian tissues was statistically significant. Western blot analysis revealed that the PI3K/Akt signaling pathway was inhibited in cells overexpressing SOX2. Western blot analysis showed that the SOX2 protein was overexpressed in paclitaxel-resistant cells and weakly detectable in paclitaxel-sensitive cells. SOX2 silencing significantly potentiated apoptosis induced by paclitaxel in SKOV3-TR with SOX2 knockdown compared to SKOV3-TR transfected with control small interfering RNA (siRNA). Our work indicates SOX2 will become both a rational indicator of ovarian cancer prognosis and a promising target for ovarian cancer gene therapy.

Highly homologous proteins exert opposite biological activities by using different interaction interfaces

We present a possible molecular basis for the opposite activity of two homologues proteins that bind similar ligands and show that this is achieved by fine-tuning of the interaction interface. The highly homologous ASPP proteins have opposite roles in regulating apoptosis: ASPP2 induces apoptosis while iASPP inhibits it. The ASPP proteins are regulated by an autoinhibitory interaction between their Ank-SH3 and Pro domains. We performed a detailed biophysical and molecular study of the Pro - Ank-SH3 interaction in iASPP and compared it to the interaction in ASPP2. We found that iASPP Pro is disordered and that the interaction sites are entirely different: iASPP Ank-SH3 binds iASPP Pro via its fourth Ank repeat and RT loop while ASPP2 Ank-SH3 binds ASPP2 Pro via its first Ank repeat and the n-src loop. It is possible that by using different moieties in the same interface, the proteins can have distinct and specific interactions resulting in differential regulation and ultimately different biological activities.

Surgery combined with chemotherapy for recurrent gastric cancer achieves better long-term prognosis

BACKGROUNDS

Recurrence is the most important factor associated with death of gastric cancer patients after surgery. The aim of this study was to explore the prognosis factors and the effective therapy for recurrent gastric cancer (RGC) patients after radical resection.

METHODS

The clinical data of 144 RGC patients who underwent radical resection from January 1999 to March 2004 were reviewed. The 15 clinicopathological factors and treatment modalities on the survival were analyzed. Univariate and multivariate analyses were performed to investigate the prognostic significance of these factors for RGC.

RESULTS

The early recurrence (<2 years) was found in 90 patients, while late recurrence (≥2 years) occurred in 54 patients. The 2-year cumulative survival rates were 23.8 % for recurrent patients receiving chemotherapy plus surgery vs. 1.2 % in patients having chemotherapy only (p < 0.001), while the median survival time was 11.0 months vs. 6.0 months (p < 0.001). Multivariate analysis indicated TNM stage after the first operation (p = 0.048), iASPP overexpression (p = 0.013), time to recurrence (p < 0.001) and treatment of recurrence (p < 0.001) as independent prognostic factors.

CONCLUSIONS

Surgery combined with chemotherapy for recurrent gastric cancer patients achieves ideal long-term prognosis, which should perform actively.

Novel biomarker candidates for the diagnosis of ovarian clear cell carcinoma

Ovarian clear cell carcinoma can arise from endometriosis; however, it is distinct from other types of epithelial ovarian carcinoma in terms of its clinicopathological and molecular features. Cancer antigen 125 lacks the sensitivity and specificity required for accurate clinical diagnosis of clear cell carcinoma. Therefore, the aim of the current review was to identify novel biomarker candidates for the immunohistochemical and serological diagnosis of clear cell carcinoma. A search of the relevant English language literature published between 1966 and 2014 was conducted using the PubMed MEDLINE online database. High-throughput tissue microarray technology and proteomic screening combined with mass spectrometry may provide additional information regarding diagnostic biomarker candidates for ovarian clear cell carcinoma. The present review summarizes the characteristics of potential genomic alterations that activate cancer signaling pathways and, thus, contribute to carcinogenesis. The major signaling pathways activated in clear cell carcinoma are associated with cell cycle regulation (hepatitis A virus cellular receptor 1 and tumor protein D52), growth factor signaling (insulin-like growth factor binding protein 1; KiSS-1 metastasis-suppressor; erb-b2 receptor tyrosine kinase 2; and fibroblast growth factor receptor 2), anti-apoptosis and survival pathways [sialidase 3 (membrane sialidase)], metabolism (γ-glutamyltransferase 1), chemoresistance (napsin A aspartic peptidase, glutathione peroxidase 3; and aldehyde dehydrogenase 1 family, member A1), coagulation [coagulation factor III (thromboplastin, tissue factor); and tissue factor pathway inhibitor 2], signaling (lectin, galactoside-binding and soluble, 3), and adhesion and the extracellular matrix [cadherin 1, type 1, E-cadherin (epithelial); versican; and laminin, α 5]. The present review of the relevant literature may provide a basis for additional clinical investigation of the ovarian clear cell carcinoma serum biomarker candidate proteins identified herein.

Overexpression of forkhead box protein M1 (FOXM1) in ovarian cancer correlates with poor patient survival and contributes to paclitaxel resistance

Aim

Deregulation of FOXM1 has been documented in various cancers. The aim of this study was to evaluate the role of FOXM1 in ovarian cancer tumorigenesis and paclitaxel resistance.

Experimental Design

Expression of FOXM1 was examined in 119 clinical samples by immunohistochemistry and correlated with clinicopathological parameters. Effects of FOXM1 knockdown on ovarian cancer cell migration, invasion and mitotic catastrophe were also studied. qPCR and ChIP-qPCR were used to establish KIF2C as a novel FOXM1 target gene implicated in chemoresistance.

Results

High nuclear FOXM1 expression in ovarian cancer patient samples was significantly associated with advanced stages (P = 0.035), shorter overall (P = 0.019) and disease-free (P = 0.014) survival. Multivariate analysis confirmed FOXM1 expression as an independent prognostic factor for ovarian cancer. FOXM1 knockdown significantly inhibited migration and invasion of ovarian cancer cells and enhanced paclitaxel-mediated cell death and mitotic catastrophe in a p53-independent manner. Bioinformatics analysis suggested a number of potential transcription targets of FOXM1. One of the potential targets, KIF2C, exhibited similar expression pattern to FOXM1 in chemosensitive and chemoresistant cells in response to paclitaxel treatment. FOXM1 could be detected at the promoter of KIF2C and FOXM1 silencing significantly down-regulated KIF2C.

Conclusion

Our findings suggest that FOXM1 is associated with poor patient outcome and contributes to paclitaxel resistance by blocking mitotic catastrophe. KIF2C is identified as a novel FOXM1 transcriptional target that may be implicated in the acquisition of chemoresistance. FOXM1 should be further investigated as a potential prognostic marker and therapeutic target for ovarian cancer.

A small peptide derived from p53 linker region can resume the apoptotic activity of p53 by sequestering iASPP with p53

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.

Nuclear iASPP may facilitate prostate cancer progression

One of the major challenges in prostate cancer (PCa) research is the identification of key players that control the progression of primary cancers to invasive and metastatic disease. The majority of metastatic PCa express wild-type p53, whereas loss of p63 expression, a p53 family member, is a common event. Here we identify inhibitor of apoptosis-stimulating protein of p53 (iASPP), a common cellular regulator of p53 and p63, as an important player of PCa progression. Detailed analysis of the prostate epithelium of iASPP transgenic mice, iASPP^Δ8/Δ8 mice, revealed that iASPP deficiency resulted in a reduction in the number of p63 expressing basal epithelial cells compared with that seen in wild-type mice. Nuclear and cytoplasmic iASPP expression was greater in PCa samples compared with benign epithelium. Importantly nuclear iASPP associated with p53 accumulation in vitro and in vivo. A pair of isogenic primary and metastatic PCa cell lines revealed that nuclear iASPP is enriched in the highly metastatic PCa cells. Nuclear iASPP is often detected in PCa cells located at the invasive leading edge in vivo. Increased iASPP expression associated with metastatic disease and PCa-specific death in a clinical cohort with long-term follow-up. These results suggest that iASPP function is required to maintain the expression of p63 in normal basal prostate epithelium, and nuclear iASPP may inactivate p53 function and facilitate PCa progression. Thus iASPP expression may act as a predictive marker of PCa progression.

In vitro effect of iASPP on cell growth of oral tongue squamous cell carcinoma

iASPP is an inhibitory member of the apoptosis-stimulating proteins of P53 (ASPP) family. iASPP is over expressed in several malignant tumors and potentially affects cancer progression. However, the expression and potential role of iASPP in oral tongue squamous cell carcinoma (OTSCC) have not been addressed. In our study, we detected iASPP expression in OTSCC by immunohistochemistry. iASPP expression is up-regulated in OTSCC tissues. Moreover, in clinical pathology specimens, we found that increased iASPP expression correlates with poor differentiation and lymph node metastasis. Using multicellular tumor spheroids (MTS) and flow cytometry, we demonstrated that iASPP down-regulation arrests OTSCC cells at the G0/G1 phase, induces OTSCC cell apoptosis and inhibits OTSCC cell proliferation. These results indicate that iASPP plays a significant role in the progression of OTSCC and may serve as a biomarker or therapeutic target for OTSCC patients.