The oncogenic phosphatase PPM1D confers cisplatin resistance in ovarian carcinoma cells by attenuating checkpoint kinase 1 and p53 activation

SOD1 is a synthetic-lethal target in PPM1D-mutant leukemia cells

The DNA damage response is critical for maintaining genome integrity and is commonly disrupted in the development of cancer. PPM1D (protein phosphatase Mg2+/Mn2+-dependent 1D) is a master negative regulator of the response; gain-of-function mutations and amplifications of PPM1D are found across several human cancers making it a relevant pharmacological target. Here, we used CRISPR/Cas9 screening to identify synthetic-lethal dependencies of PPM1D, uncovering superoxide dismutase-1 (SOD1) as a potential target for PPM1D-mutant cells. We revealed a dysregulated redox landscape characterized by elevated levels of reactive oxygen species and a compromised response to oxidative stress in PPM1D-mutant cells. Altogether, our results demonstrate a role for SOD1 in the survival of PPM1D-mutant leukemia cells and highlight a new potential therapeutic strategy against PPM1D-mutant cancers.

Plasma Gelsolin Inhibits Natural Killer Cell Function and Confers Chemoresistance in Epithelial Ovarian Cancer

Plasma gelsolin (pGSN) overexpression in ovarian cancer (OVCA) disarms immune function, contributing to chemoresistance. The aim of this study was to investigate the immunoregulatory effects of pGSN expression on natural killer (NK) cell function in OVCA. OVCA tissues from primary surgeries underwent immunofluorescent staining of pGSN and the activated NK cell marker natural cytotoxicity triggering receptor 1 to analyze the prognostic impact of pGSN expression and activated NK cell infiltration. The immunoregulatory effects of pGSN on NK cells were assessed using apoptosis assay, cytokine secretion, immune checkpoint-receptor expression, and phosphorylation of STAT3. In OVCA tissue analyses, activated NK cell infiltration provided survival advantages to patients. However, high pGSN expression attenuated the survival benefits of activated NK cell infiltration. In the in vitro experiment, pGSN in OVCA cells induced NK cell death through cell-to-cell contact. pGSN increased T-cell immunoglobulin and mucin-domain-containing-3 expression (TIM-3) on activated NK cells. Further, it decreased interferon-γ production in activated TIM-3+ NK cells, attenuating their anti-tumor effects. Thus, increased pGSN expression suppresses the anti-tumor functions of NK cells. The study provides insights into why immunotherapy is rarely effective in patients with OVCA and suggests novel treatment strategies.

SOD1 is a synthetic lethal target in PPM1D-mutant leukemia cells

The DNA damage response is critical for maintaining genome integrity and is commonly disrupted in the development of cancer. PPM1D (protein phosphatase, Mg2+/Mn2+ dependent 1D) is a master negative regulator of the response; gain-of-function mutations and amplifications of PPM1D are found across several human cancers making it a relevant pharmacologic target. Here, we used CRISPR/Cas9 screening to identify synthetic-lethal dependencies of PPM1D, uncovering superoxide dismutase-1 (SOD1) as a potential target for PPM1D-mutant cells. We revealed a dysregulated redox landscape characterized by elevated levels of reactive oxygen species and a compromised response to oxidative stress in PPM1D-mutant cells. Altogether, our results demonstrate the protective role of SOD1 against oxidative stress in PPM1D-mutant leukemia cells and highlight a new potential therapeutic strategy against PPM1D-mutant cancers.

AFB1 Triggers Lipid Metabolism Disorders through the PI3K/Akt Pathway and Mediates Apoptosis Leading to Hepatotoxicity

As the most prevalent mycotoxin in agricultural products, aflatoxin B1 not only causes significant economic losses but also poses a substantial threat to human and animal health. AFB1 has been shown to increase the risk of hepatocellular carcinoma (HCC) but the underlying mechanism is not thoroughly researched. Here, we explored the toxicity mechanism of AFB1 on human hepatocytes following low-dose exposure based on transcriptomics and lipidomics. Apoptosis-related pathways were significantly upregulated after AFB1 exposure in all three hES-Hep, HepaRG, and HepG2 hepatogenic cell lines. By conducting a comparative analysis with the TCGA-LIHC database, four biomarkers (MTCH1, PPM1D, TP53I3, and UBC) shared by AFB1 and HCC were identified (hazard ratio > 1), which can be used to monitor the degree of AFB1-induced hepatotoxicity. Simultaneously, AFB1 induced abnormal metabolism of glycerolipids, sphingolipids, and glycerophospholipids in HepG2 cells (FDR < 0.05, impact > 0.1). Furthermore, combined analysis revealed strong regulatory effects between PIK3R1 and sphingolipids (correlation coefficient > 0.9), suggesting potential mediation by the phosphatidylinositol 3 kinase (PI3K) /protein kinase B (AKT) signaling pathway within mitochondria. This study revealed the dysregulation of lipid metabolism induced by AFB1 and found novel target genes associated with AFB-induced HCC development, providing reliable evidence for elucidating the hepatotoxicity of AFB as well as assessing food safety risks.

The Application of an Extracellular Vesicle-Based Biosensor in Early Diagnosis and Prediction of Chemoresponsiveness in Ovarian Cancer

BACKGROUND

Ovarian cancer (OVCA) is the most fatal gynecological cancer with late diagnosis and plasma gelsolin (pGSN)-mediated chemoresistance representing the main obstacles to treatment success. Since there is no reliable approach to diagnosing patients at an early stage as well as predicting chemoresponsiveness, there is an urgent need to develop a diagnostic platform for such purposes. Small extracellular vesicles (sEVs) are attractive biomarkers given their potential accuracy for targeting tumor sites.

METHODS

We have developed a novel biosensor which utilizes cysteine-functionalized gold nanoparticles that simultaneously bind to cisplatin (CDDP) and plasma/cell-derived EVs, affording us the advantage of predicting OVCA chemoresponsiveness, and early diagnosis using surface-enhanced Raman spectroscopy.

RESULTS

We found that pGSN regulates cortactin (CTTN) content resulting in the formation of nuclear- and cytoplasmic-dense granules facilitating the secretion of sEVs carrying CDDP; a strategy used by resistant cells to survive CDDP action. The clinical utility of the biosensor was tested and subsequently revealed that the sEV/CA125 ratio outperformed CA125 and sEV individually in predicting early stage, chemoresistance, residual disease, tumor recurrence, and patient survival.

CONCLUSION

These findings highlight pGSN as a potential therapeutic target and provide a potential diagnostic platform to detect OVCA earlier and predict chemoresistance; an intervention that will positively impact patient-survival outcomes.

A novel combination of niraparib and anlotinib in platinum-resistant ovarian cancer: Efficacy and safety results from the phase II, multi-center ANNIE study

BACKGROUND

Patients with platinum-resistant recurrent ovarian cancer (PROC) face poor prognosis and limited treatment options. Single-agent antiangiogenics and poly (ADP-ribose) polymerase (PARP) inhibitors both show some activities in platinum-resistant diseases. The ANNIE study aimed to evaluate the efficacy and safety of the novel combination of the PARP inhibitor niraparib and the antiangiogenic anlotinib in patients with PROC.

METHODS

ANNIE is a multicentre, single-arm, phase 2 study (ClinicalTrials.gov identifier NCT04376073) conducted at three hospitals in China. Eligible patients had histologically confirmed epithelial ovarian, fallopian tube, or primary peritoneal cancer that recurred within 6 months of last platinum-based chemotherapy. Patients with prior PARP inhibitor exposure were excluded. The enrolled patients received oral niraparib 200 mg or 300 mg (baseline body weight-directed) once daily continuously and anlotinib 10 mg (12 mg before protocol amendment) once daily on days 1-14 of each 21-day cycle until disease progression or intolerable toxicity. The primary endpoint was objective response rate (ORR).

FINDINGS

Between May 22, 2020, and April 22, 2021, 40 patients were enrolled and treated. Thirty-six patients underwent post-baseline tumour assessments. By data cut-off (January 31, 2022), median follow-up was 15.4 months (95% CI 12.6-17.7). Intention-to-treat ORR was 50.0% (95% CI 33.8-66.2), including one complete response and 19 partial responses. Median (95% CI) progression-free survival and overall survival were 9.2 months (7.4-11.9) and 15.3 months (13.9-not evaluable), respectively. Drug-related, grade ≥3 TEAEs were reported in 26 (68%) patients. There were no treatment-related deaths.

INTERPRETATION

Niraparib plus anlotinib showed promising antitumour activity in patients with PROC. This oral combination warrants further investigation as a potential novel, convenient treatment option for patients with PROC.

FUNDING

Zai Lab (Shanghai) Co., Ltd; Jiangsu Chia Tai-Tianqing Pharmaceutical Co., Ltd; the National Natural Science Foundation of China (No. 82102783).

S6K1 phosphorylates Cdk1 and MSH6 to regulate DNA repair

The mTORC1 substrate, S6 Kinase 1 (S6K1), is involved in the regulation of cell growth, ribosome biogenesis, glucose homeostasis, and adipogenesis. Accumulating evidence has suggested a role for mTORC1 signaling in the DNA damage response. This is mostly based on the findings that mTORC1 inhibitors sensitized cells to DNA damage. However, a direct role of the mTORC1-S6K1 signaling pathway in DNA repair and the mechanism by which this signaling pathway regulates DNA repair is unknown. In this study, we discovered a novel role for S6K1 in regulating DNA repair through the coordinated regulation of the cell cycle, homologous recombination (HR) DNA repair (HRR) and mismatch DNA repair (MMR) mechanisms. Here, we show that S6K1 orchestrates DNA repair by phosphorylation of Cdk1 at serine 39, causing G2/M cell cycle arrest enabling homologous recombination and by phosphorylation of MSH6 at serine 309, enhancing MMR. Moreover, breast cancer cells harboring RPS6KB1 gene amplification show increased resistance to several DNA damaging agents and S6K1 expression is associated with poor survival of breast cancer patients treated with chemotherapy. Our findings reveal an unexpected function of S6K1 in the DNA repair pathway, serving as a tumorigenic barrier by safeguarding genomic stability.

Damage to the DNA in our cells can cause harmful changes that, if unchecked, can lead to the development of cancer. To help prevent this, cellular mechanisms are in place to repair defects in the DNA. A particular process, known as the mTORC1-S6K1 pathway is suspected to be important for repair because when this pathway is blocked, cells become more sensitive to DNA damage.

It is still unknown how the various proteins involved in the mTORC1-S6K1 pathway contribute to repairing DNA. One of these proteins, S6K1, is an enzyme involved in coordinating cell growth and survival. The tumor cells in some forms of breast cancer produce more of this protein than normal, suggesting that S6K1 benefits these cells’ survival. However, it is unclear exactly how the enzyme does this.

Amar-Schwartz, Ben-Hur, Jbara et al. studied the role of S6K1 using genetically manipulated mouse cells and human cancer cells. These experiments showed that the protein interacts with two other proteins involved in DNA repair and activates them, regulating two different repair mechanisms and protecting cells against damage.

These results might explain why some breast cancer tumors are resistant to radiotherapy and chemotherapy treatments, which aim to kill tumor cells by damaging their DNA. If this is the case, these findings could help clinicians choose more effective treatment options for people with cancers that produce additional S6K1. In the future, drugs that block the activity of the enzyme could make cancer cells more susceptible to chemotherapy.

Plasma Gelsolin Confers Chemoresistance in Ovarian Cancer by Resetting the Relative Abundance and Function of Macrophage Subtypes

Simple Summary

Ovarian cancer is one of the deadliest female cancers with very poor survival, primarily due to late diagnosis, recurrence and chemoresistance. Although the over-expression of plasma gelsolin (pGSN) protects ovarian cancer cells from chemotherapy-induced death, its immunological role in the tumor microenvironment is less explored. Here, we demonstrate that pGSN over-expression downregulates the anti-tumor functions of M1 macrophages, an effect that contributes to chemoresistance and poor patient survival. This study demonstrates the novel inhibitory role of pGSN on tumor-infiltrated M1 macrophages and also offers new insights in maximizing the effectiveness of immunotherapy for ovarian cancer patients.

Abstract

Ovarian cancer (OVCA) is the most lethal gynaecological cancer with a 5-year survival rate less than 50%. Despite new therapeutic strategies, such as immune checkpoint blockers (ICBs), tumor recurrence and drug resistance remain key obstacles in achieving long-term therapeutic success. Therefore, there is an urgent need to understand the cellular mechanisms of immune dysregulation in chemoresistant OVCA in order to harness the host’s immune system to improve survival. The over-expression of plasma gelsolin (pGSN) mRNA is associated with a poorer prognosis in OVCA patients; however, its immuno-modulatory role has not been elucidated. In this study, for the first time, we report pGSN as an inhibitor of M1 macrophage anti-tumor functions in OVCA chemoresistance. Increased epithelial pGSN expression was associated with the loss of chemoresponsiveness and poor survival. While patients with increased M1 macrophage infiltration exhibited better survival due to nitric-oxide-induced ROS accumulation in OVCA cells, cohorts with poor survival had a higher infiltration of M2 macrophages. Interestingly, increased epithelial pGSN expression was significantly associated with the reduced survival benefits of infiltrated M1 macrophages, through apoptosis via increased caspase-3 activation and reduced production of iNOS and TNFα. Additionally, epithelial pGSN expression was an independent prognostic marker in predicting progression-free survival. These findings support our hypothesis that pGSN is a modulator of inflammation and confers chemoresistance in OVCA, in part by resetting the relative abundance and function of macrophage subtypes in the ovarian tumor microenvironment. Our findings raise the possibility that pGSN may be a potential therapeutic target for immune-mediated chemoresistance in OVCA.

Senescence-associated secretory phenotype and activation of NF-κB in splenocytes of old mice exposed to irradiation at a young age

DNA damage-induced cellular senescence is involved in aging. We reported previously that p53^+/- mice subjected to irradiation at a young age exhibited an increased number of splenic lymphocytes in the S and G2/M phases. However, the detailed nature of splenic disorders in these mice is not fully understood. In this study, we investigated the effects on molecules in splenocytes, especially on senescence factors after early exposure of mice to radiation. Mice, 8- (young) or 17-, 30-, and 41-week-old (old) p53^+/- were subjected to 3-Gy whole-body irradiation. Splenocytes were prepared at 56 weeks of age. Immunoblot showed that irradiation at 8 weeks enhanced the expression and phosphorylation of p53, cyclin-dependent kinase 2, cell division cycle 6, and the MDM2 proto-oncogene in splenocytes. However, these molecules were not affected by irradiation at 17, 30, and 41 weeks of age. Similarly, irradiation at 8, but not 17, 30, or 41 weeks, induced phosphorylation of IKKα, NF-κB inhibitor alpha, and p65. Electrophoretic mobility shift assay demonstrated that active forms of NF-κB were increased. In addition, enzyme-linked immunosorbent assay showed that lipopolysaccharide-induced IL-6 production was enhanced in splenocytes of mice irradiated at 8 weeks. ATP levels were increased in splenocytes of mice irradiated at 8, but not 17, 30, or 41 weeks. CDK2 expression and p65 phosphorylation were induced in CD45R/B220⁺ cells from irradiated mice. Overall, irradiation induced a NF-κB-related immune response in the spleen with an increase in senescence marker proteins, such as CDKs and IL-6, which are known to be typical senescence-associated secretory phenotype factors related to stresses, such as DNA damage.

IK: A novel cell mitosis regulator that contributes to carcinogenesis

Carcinogenesis is characterized by abnormal regulation of cell growth and cell death. IK is a novel cell mitosis regulator that may contribute to carcinogenesis. Previous studies showed that the loss of IK expression resulted in cell mitotic arrest and even cell death. Besides, IK can also inhibit the interferon gamma (IFN-γ)-induced expression of human leukocyte antigen (HLA) class II antigen, which is associated with tumour immune microenvironment. To gain insight into the current research progress regarding IK, we conducted a review and searched the limited literature on IK using PubMed or Web of Science. In this review, we discussed the possible biological functions and mechanisms of IK in cancer and its immune microenvironment. Future perspectives of IK were also mentioned to explore its clinical significance.

p53 regulated senescence mechanism and role of its modulators in age-related disorders

Multiple co-morbidities are associated with age, and there is a need for the broad-spectrum drug to prevent multiple regimens that may cause an adverse effect in the geriatric population. Cellular senescence is a primary mechanism for ageing in various tissues. p53, a tumor suppressor protein, plays a significant role in forming DNA damage foci and post different stress responses. DNA damage foci can be transient or persistent that can progress to DNA-SCARS inducing senescence. p53 also plays a role in apoptosis and negative regulation of SASP. Few upstream targets like FOXO4, MDM2, MDM4, USP7 control the availability of p53 for apoptosis. Hence, the senolytic therapies, modulating p53 upstream targets, can be a good approach for preventing age-related disorders. This review discusses the insights on the role of p53 in the formation of DNA-SCARS, various upstream target proteins, and pathways involved in p53 regulation. Further, the review aimed to include recently discovered small molecules acting on these upstream targets, and those can be modified using medicinal chemistry approaches to give successful senotherapeutics.

Overview of Cellular Mechanisms and Signaling Pathways of Piceatannol

Stilbenoids are a group of naturally occurring phenolic compounds found in various plant species. They share a common backbone structure known as stilbene. However, differences in the nature and position of substituents have made it possible to produce many derivatives. Piceatannol [PT], a hydroxylated derivative from resveratrol, exerts various biological activities ranging from cancer prevention, cardio- protection, neuro-protection, anti-diabetic, depigmentation and so on. Although positive results were obtained in most cell culture and animal studies, the relevant cellular and molecular mechanisms of cytokines and signaling pathway about their biological effects still unclear. Thus, in the current review, we focus on the latest findings of PT on cellular biology in order to better understand the underlying therapeutic mechanisms of PT among various diseases.

Model-based optimization of combination protocols for irradiation-insensitive cancers

Alternations in the p53 regulatory network may render cancer cells resistant to the radiation-induced apoptosis. In this theoretical study we search for the best protocols combining targeted therapy with radiation to treat cancers with wild-type p53, but having downregulated expression of PTEN or overexpression of Wip1 resulting in resistance to radiation monotherapy. Instead of using the maximum tolerated dose paradigm, we exploit stochastic computational model of the p53 regulatory network to calculate apoptotic fractions for both normal and cancer cells. We consider combination protocols, with irradiations repeated every 12, 18, 24, or 36 h to find that timing between Mdm2 inhibitor delivery and irradiation significantly influences the apoptotic cell fractions. We assume that uptake of the inhibitor is higher by cancer than by normal cells and that cancer cells receive higher irradiation doses from intersecting beams. These two assumptions were found necessary for the existence of protocols inducing massive apoptosis in cancer cells without killing large fraction of normal cells neighboring tumor. The best found protocols have irradiations repeated every 24 or 36 h with two inhibitor doses per irradiation cycle, and allow to induce apoptosis in more than 95% of cancer cells, killing less than 10% of normal cells.

Plasma Gelsolin Inhibits CD8+ T-cell Function and Regulates Glutathione Production to Confer Chemoresistance in Ovarian Cancer

Although initial treatment of ovarian cancer is successful, tumors typically relapse and become resistant to treatment. Because of poor infiltration of effector T cells, patients are mostly unresponsive to immunotherapy. Plasma gelsolin (pGSN) is transported by exosomes (small extracellular vesicle, sEV) and plays a key role in ovarian cancer chemoresistance, yet little is known about its role in immunosurveillance. Here, we report the immunomodulatory roles of sEV-pGSN in ovarian cancer chemoresistance. In chemosensitive conditions, secretion of sEV-pGSN was low, allowing for optimal CD8⁺ T-cell function. This resulted in increased T-cell secretion of IFNγ, which reduced intracellular glutathione (GSH) production and sensitized chemosensitive cells to cis-diaminedichloroplatinum (CDDP)-induced apoptosis. In chemoresistant conditions, increased secretion of sEV-pGSN by ovarian cancer cells induced apoptosis in CD8⁺ T cells. IFNγ secretion was therefore reduced, resulting in high GSH production and resistance to CDDP-induced death in ovarian cancer cells. These findings support our hypothesis that sEV-pGSN attenuates immunosurveillance and regulates GSH biosynthesis, a phenomenon that contributes to chemoresistance in ovarian cancer. SIGNIFICANCE: These findings provide new insight into pGSN-mediated immune cell dysfunction in ovarian cancer chemoresistance and demonstrate how this dysfunction can be exploited to enhance immunotherapy.

The role of PPM1D in cancer and advances in studies of its inhibitors

A greater understanding of factors causing cancer initiation, progression and evolution is of paramount importance. Among them, the serine/threonine phosphatase PPM1D, also referred to as wild-type p53-induced phosphatase 1 (Wip1) or protein phosphatase 2C delta (PP2Cδ), is emerging as an important oncoprotein due to its negative regulation on a number of crucial cancer suppressor pathways. Initially identified as a p53-regulated gene, PPM1D has been afterwards found amplified and more recently mutated in many human cancers such as breast cancer. The latest progress in this field further reveals that selective inhibition of PPM1D to delay tumor onset or reduce tumor burden represents a promising anti-cancer strategy. Here, we review the advances in the studies of the PPM1D activity and its relevance to various cancers, and recent progress in development of PPM1D inhibitors and discuss their potential application in cancer therapy. Consecutive research on PPM1D and its relationship with cancer is essential, as it ultimately contributes to the etiology and treatment of cancer.

Role of p53 in the Regulation of Cellular Senescence

The p53 transcription factor plays a critical role in cellular responses to stress. Its activation in response to DNA damage leads to cell growth arrest, allowing for DNA repair, or directs cellular senescence or apoptosis, thereby maintaining genome integrity. Senescence is a permanent cell-cycle arrest that has a crucial role in aging, and it also represents a robust physiological antitumor response, which counteracts oncogenic insults. In addition, senescent cells can also negatively impact the surrounding tissue microenvironment and the neighboring cells by secreting pro-inflammatory cytokines, ultimately triggering tissue dysfunction and/or unfavorable outcomes. This review focuses on the characteristics of senescence and on the recent advances in the contribution of p53 to cellular senescence. Moreover, we also discuss the p53-mediated regulation of several pathophysiological microenvironments that could be associated with senescence and its development.

From Favorable Histology to Relapse: The Clonal Evolution of a Wilms Tumor

Favorable histology (FH) Wilms tumor (WT) is one of the most curable of all human cancers, yet a small minority of patients fail treatment. The underlying biological pathways that lead to therapy resistance are unknown. We report a case of initially unresectable, FH WT which revealed limited necrosis and persistent blastemal predominant histology following neoadjuvant chemotherapy. Despite intensification of therapy and whole abdominal radiation, the patient relapsed and succumbed to her disease. In an effort to discover candidate drivers of drug resistance, whole exome sequencing and copy number analysis were performed on samples from all 3 tumor specimens. Sequencing results revealed outgrowth of clones with a dramatically different genetic landscape including dominant mutations that could explain therapy evasion, some of which have not been previously reported in WT. Our results implicate PPM1D, previously shown to be associated with drug resistance in other tumors, as the major driver of treatment failure.

Potentiality of Protein phosphatase Mg2+ /Mn2+ dependent 1D as a biomarker for predicting prognosis in acute myeloid leukemia patients

Objective

The present study aimed to investigate the correlation of protein phosphatase Mg²⁺/Mn²⁺ dependent 1D (PPM1D) with the risk stratification, treatment response, and survival profile in acute myeloid leukemia (AML) patients.

Methods

Totally 221 de novo AML patients and 50 healthy donors were enrolled. The bone marrow samples were collected before treatment from AML patients and acquired after enrollment from healthy donors. And bone marrow mononuclear cells were separated for detecting the mRNA/protein expressions of PPM1D by reverse transcription‐quantitative polymerase chain reaction and Western blot. Complete remission (CR) was assessed after induction treatment, and event‐free survival (EFS) and overall survival (OS) were calculated in AML patients.

Results

PPM1D mRNA (P < .001)/protein (P < .001) relative expressions were increased in AML patients compared with healthy donors, and receiver operating characteristic curve presented that PPM1D mRNA (AUC: 0.728, 95% CI: 0.651‐0.806)/protein (AUC: 0.782, 95% CI: 0.707‐0.857) relative expressions could differentiate AML patients from healthy donors. In AML patients, PPM1D mRNA (P < .001)/protein (P < .001) high relative expressions were correlated with poor‐risk stratification. As for its association with prognosis, PPM1D mRNA (P < .001)/protein (P = .010) relative expressions were elevated in CR patients compared with non‐CR patients. Patients with PPM1D mRNA (P < .001 for EFS; P = .004 for OS)/protein (P < .001 for EFS; P = .006 for OS) high relative expressions exhibited reduced EFS and OS compared with those with low expressions.

Conclusion

PPM1D high expression correlates with poor‐risk stratification and might serve as a potential biomarker for worse prognosis in AML patients, suggesting its potential to guide AML management.

The exosome-mediated autocrine and paracrine actions of plasma gelsolin in ovarian cancer chemoresistance

Ovarian cancer (OVCA) is the most lethal gynecological cancer, due predominantly to late presentation, high recurrence rate and common chemoresistance development. The expression of the actin-associated protein cytosolic gelsolin (GSN) regulates the gynecological cancer cell fate resulting in dysregulation in chemosensitivity. In this study, we report that elevated expression of plasma gelsolin (pGSN), a secreted isoform of GSN and expressed from the same GSN gene, correlates with poorer overall survival and relapse-free survival in patients with OVCA. In addition, it is highly expressed and secreted in chemoresistant OVCA cells than its chemosensitive counterparts. pGSN, secreted and transported via exosomes (Ex-pGSN), upregulates HIF1α–mediated pGSN expression in chemoresistant OVCA cells in an autocrine manner as well as confers cisplatin resistance in otherwise chemosensitive OVCA cells. These findings support our hypothesis that exosomal pGSN promotes OVCA cell survival through both autocrine and paracrine mechanisms that transform chemosensitive cells to resistant counterparts. Specifically, pGSN transported via exosomes is a determinant of chemoresistance in OVCA.

Wild-type p53-induced phosphatase 1 down-regulation promotes apoptosis by activating the DNA damage-response pathway in amyotrophic lateral sclerosis

Accumulation of DNA damage has been detected in the spinal cord of patients as well as in the G93A mouse model of amyotrophic lateral sclerosis (ALS). Wild-type p53-induced phosphatase 1 (Wip1) is a p53-inducible serine/threonine phosphatase that terminates DNA-damage responses via dephosphorylation of DNA-damage response proteins, namely ataxia-telangiectasia mutated (ATM) kinase, checkpoint kinase 2, and p53, thus enhancing cell proliferation. However, the role of Wip1, DNA-damage responses, and their interaction in ALS development remains to be elucidated. Here, we showed that Wip1 expression levels were substantially decreased in ALS motor neurons compared with wild-type controls both in vivo and in vitro. The DNA-damage response was activated in superoxide dismutase 1 (SOD1) ^G93A-transfected cells. However, increased expression of Wip1 improved cell viability and inhibited the DNA-damage response in mutated SOD1^G93A cells. Further studies demonstrated that decreased Wip1 expression reduced cell viability and further activated the DNA-damage response in chronic H₂O₂-treated NSC34 cells. In contrast, Wip1 promoted cell survival and suppressed DNA damage-induced apoptosis during persistent DNA damage conditions. Over-expression of Wip1 in the central nervous system (CNS) can delay the onset of disease symptoms, extended the survival, decreased MN loss improved motor function and inhibit the DNA-damage response in SOD1 G93A mice. Furthermore, homeodomain-interacting protein kinase 2 (HIPK2) promoted the degradation of Wip1 via the ubiquitin-proteasome system during chronic stress. These findings indicate that persistent accumulation of DNA damage and subsequent chronic activation of the downstream DNA damage-response ATM and p53 pro-apoptotic signaling pathways may trigger neuronal dysfunction and neuronal death in ALS. Wip1 may play a protective role by targeting the DNA-damage response in ALS motor neurons. Importantly, these findings provide a novel direction for therapeutic options for patients with ALS.

PACT cessation overcomes ovarian cancer cell chemoresistance to cisplatin by enhancing p53-mediated apoptotic pathway

Ovarian cancer ranks as a lethal gynecological malignancy, and development of resistance to chemotherapy agents constitutes a major clinical challenge in ovarian carcinoma management. P53-associated cellular protein-testes derived (PACT) is recently proven to be expressed aberrantly in several cancers, and exerts a critical roles in cell proliferation, apoptosis and migration. Up to now, its function in chemoresistance of ovarian cancer remains poorly defined. In the present study, elevated expression of PACT was detected in cisplatin-resistant A2780/CP cells relative to cisplatin-sensitive A2780 cells. Moreover, exposure to cisplatin also increased PACT expression in A2780 cells. Functional assay confirmed that knockdown of PACT further aggravated the inhibitory effects of cisplatin on A2780 cell viability and enhanced cell apoptosis and caspase-3 activity in cisplatin-treated A2780 cells, indicating that PACT cessation elevates cell sensitivity to cisplatin in A2780 cells. Whilst, deletion of PACT affords little effects on cisplatin resistance in p53-defective SKOV3 cells. Mechanistic analysis corroborated that depression of PACT notably enhanced cisplatin-induced p53 expression, concomitant with the increases in p53-downstream Bax, p21 expression and decrease in Bcl-2 expression. Intriguingly, blocking the p53 pathway notably reversed PACT inhibition-increased cell sensitivity to cisplatin in A2780 cells by elevating cell viability and depressing cell apoptosis. Additionally, abrogation of p53 signaling also blunts PACT suppression-overcomed chemotherapy resistance to cisplatin in A2780/CP cells. Together, these findings confirm that targeting PACT may antagonize ovarian cancer cell resistance to cisplatin, supporting a promising therapeutic strategy to overcome the chemotherapy resistance in the treatment of ovarian cancer.

PPM1D Mutations Drive Clonal Hematopoiesis in Response to Cytotoxic Chemotherapy

Clonal hematopoiesis (CH), in which stem cell clones dominate blood production, becomes increasingly common with age and can presage malignancy development. The conditions that promote ascendancy of particular clones are unclear. We found that mutations in PPM1D (protein phosphatase Mn2+/Mg2+-dependent 1D), a DNA damage response regulator that is frequently mutated in CH, were present in one-fifth of patients with therapy-related acute myeloid leukemia or myelodysplastic syndrome and strongly correlated with cisplatin exposure. Cell lines with hyperactive PPM1D mutations expand to outcompete normal cells after exposure to cytotoxic DNA damaging agents including cisplatin, and this effect was predominantly mediated by increased resistance to apoptosis. Moreover, heterozygous mutant Ppm1d hematopoietic cells outcompeted their wild-type counterparts in vivo after exposure to cisplatin and doxorubicin, but not during recovery from bone marrow transplantation. These findings establish the clinical relevance of PPM1D mutations in CH and the importance of studying mutation-treatment interactions. VIDEO ABSTRACT.

Distinct roles for phosphoinositide 3-kinases γ and δ in malignant B cell migration

The PI 3-kinases (PI3K) are essential mediators of chemokine receptor signaling necessary for migration of chronic lymphocytic leukemia (CLL) cells and their interaction with tissue-resident stromal cells. While the PI3Kδ-specific inhibitor idelalisib shows efficacy in treatment of CLL and other B cell malignancies, the function of PI3Kγ has not been extensively studied in B cells. Here, we assess whether PI3Kγ has non-redundant functions in CLL migration and adhesion to stromal cells. We observed that pharmaceutical PI3Kγ inhibition with CZC24832 significantly impaired CLL cell migration, while dual PI3Kδ/γ inhibitor duvelisib had a greater impact than single isoform-selective inhibitors. Knockdown of PI3Kγ reduced migration of CLL cells and cell lines. Expression of the PI3Kγ subunits increased in CLL cells in response to CD40L/IL-4, whereas BCR cross-linking had no effect. Overexpression of PI3Kγ subunits enhanced cell migration in response to SDF1α/CXCL12, with the strongest effect observed within ZAP70 + CLL samples. Microscopic tracking of cell migration within chemokine gradients revealed that PI3Kγ functions in gradient sensing and impacts cell morphology and F-actin polarization. PI3Kγ inhibition also reduced CLL adhesion to stromal cells to a similar extent as idelalisib. These findings provide the first evidence that PI3Kγ has unique functions in malignant B cells.

Saikosaponin-d, a calcium mobilizing agent, sensitizes chemoresistant ovarian cancer cells to cisplatin-induced apoptosis by facilitating mitochondrial fission and G2/M arrest

Cisplatin (CDDP) and its derivatives are first line anti-cancer drugs for ovarian cancer (OVCA). However, chemoresistance due to high incidence of p53 mutations leads to poor clinical prognosis. Saikosaponin-d (Ssd), a saponin from a herbal plant extract, has been shown to induce cell death and sensitize chemoresistant cells to chemotherapeutic agents. Here, we demonstrated that Ssd sensitized chemoresistant OVCA cells with either p53-wt, -mutant and -null to CDDP. The action of Ssd appears to be through induction of mitochondrial fragmentation and G2/M arrest. Ssd is mediated via calcium signaling, up-regulation of the mitochondrial fission proteins Dynamin-related protein 1 (Drp1) and optic atrophy 1 (Opa1), and loss in mitochondrial membrane potential (MMP). Moreover, in the presence of CDDP, Ssd also down-regulates protein phosphatase magnesium-dependent 1 D (PPM1D) and increases the phosphorylation of checkpoint protein kinases (Chk) 1, cell division cycle 25c (Cdc25c) and Cyclin dependent kinase 1 (Cdk1). Our findings suggest that Ssd could sensitize OVCA to CDDP independent of the p53 status through multiple signaling pathways. They support the notion that Ssd may be a novel adjuvant for the treatment of chemoresistant OVCA.

Role of wild-type p53-induced phosphatase 1 in cancer

Wild-type p53-induced phosphatase (Wip1) is a member of the protein phosphatase type 2C family and is an established oncogene due to its dephosphorylation of several tumor suppressors and negative control of the DNA damage response system. It has been reported to dephosphorylate p53, ataxia telangiectasia mutated, checkpoint kinase 1 and p38 mitogen activated protein kinases, forming negative feedback loops to inhibit apoptosis and cell cycle arrest. Wip1 serves a major role in tumorigenesis, progression, invasion, distant metastasis and apoptosis in various types of human cancer. Therefore, it may be a potential biomarker and therapeutic target in the diagnosis and treatment of cancer. Furthermore, previous evidence has revealed a new role for Wip1 in the regulation of chemotherapy resistance. In the present review, the current knowledge on the role of Wip1 in cancer is discussed, as well as its potential as a novel target for cancer treatment and its function in chemotherapy resistance.

WIP1 phosphatase as pharmacological target in cancer therapy

DNA damage response (DDR) pathway protects cells from genome instability and prevents cancer development. Tumor suppressor p53 is a key molecule that interconnects DDR, cell cycle checkpoints, and cell fate decisions in the presence of genotoxic stress. Inactivating mutations in TP53 and other genes implicated in DDR potentiate cancer development and also influence the sensitivity of cancer cells to treatment. Protein phosphatase 2C delta (referred to as WIP1) is a negative regulator of DDR and has been proposed as potential pharmaceutical target. Until recently, exploitation of WIP1 inhibition for suppression of cancer cell growth was compromised by the lack of selective small-molecule inhibitors effective at cellular and organismal levels. Here, we review recent advances in development of WIP1 inhibitors and discuss their potential use in cancer treatment.

Wip1: A candidate phosphatase for cancer diagnosis and treatment

The critical regulatory mechanisms in numerous cellular pathways including cell survival and DNA damage response mostly depend on phosphorylation and dephosphorylation of proteins. The serine/threonine phosphatase wild-type p53-induced phosphatase 1 (Wip1) is a growth-promoting phosphatase and its numerous downstream targets are important tumor suppressors. Here, we review the Wip1 activity and its relevance to cancer as an oncoprotein. Consecutive investigations about Wip1 and its relation to cancer is critical, as these studies ultimately contribute to the etiology of cancer. A number of innovative studies have recently investigated the importance of Wip1 as a new candidate for cancer diagnosis and prognosis. Accordingly, we discuss the present challenges of using Wip1 as a target for cancer treatment.

Reverting p53 activation after recovery of cellular stress to resume with cell cycle progression

The activation of p53 in response to different types of cellular stress induces several protective reactions including cell cycle arrest, senescence or cell death. These protective effects are a consequence of the activation of p53 by specific phosphorylation performed by several kinases. The reversion of the cell cycle arrest, induced by p53, is a consequence of the phosphorylated and activated p53, which triggers its own downregulation and that of its positive regulators. The different down-regulatory processes have a sequential and temporal order of events. The mechanisms implicated in p53 down-regulation include phosphatases, deacetylases, and protein degradation by the proteasome or autophagy, which also affect different p53 protein targets and functions. The necessary first step is the dephosphorylation of p53 to make it available for interaction with mdm2 ubiquitin-ligase, which requires the activation of phosphatases targeting both p53 and p53-activating kinases. In addition, deacetylation of p53 is required to make lysine residues accessible to ubiquitin ligases. The combined action of these downregulatory mechanisms brings p53 protein back to its basal levels, and cell cycle progression can resume if cells have overcome the stress or damage situation. The specific targeting of these down-regulatory mechanisms can be exploited for therapeutic purposes in cancers harbouring wild-type p53.

Prognostic Mutations in Myelodysplastic Syndrome after Stem-Cell Transplantation

BACKGROUND

Genetic mutations drive the pathogenesis of the myelodysplastic syndrome (MDS) and are closely associated with clinical phenotype. Therefore, genetic mutations may predict clinical outcomes after allogeneic hematopoietic stem-cell transplantation.

METHODS

We performed targeted mutational analysis on samples obtained before transplantation from 1514 patients with MDS who were enrolled in the Center for International Blood and Marrow Transplant Research Repository between 2005 and 2014. We evaluated the association of mutations with transplantation outcomes, including overall survival, relapse, and death without relapse.

RESULTS

TP53 mutations were present in 19% of the patients and were associated with shorter survival and a shorter time to relapse than was the absence of TP53 mutations, after adjustment for significant clinical variables (P<0.001 for both comparisons). Among patients 40 years of age or older who did not have TP53 mutations, the presence of RAS pathway mutations was associated with shorter survival than was the absence of RAS pathway mutations (P=0.004), owing to a high risk of relapse, and the presence of JAK2 mutations was associated with shorter survival than was the absence of JAK2 mutations (P=0.001), owing to a high risk of death without relapse. The adverse prognostic effect of TP53 mutations was similar in patients who received reduced-intensity conditioning regimens and those who received myeloablative conditioning regimens. By contrast, the adverse effect of RAS pathway mutations on the risk of relapse, as compared with the absence of RAS pathway mutations, was evident only with reduced-intensity conditioning (P<0.001). In young adults, 4% of the patients had compound heterozygous mutations in the Shwachman-Diamond syndrome-associated SBDS gene with concurrent TP53 mutations and a poor prognosis. Mutations in the p53 regulator PPM1D were more common among patients with therapy-related MDS than those with primary MDS (15% vs. 3%, P<0.001).

CONCLUSIONS

Genetic profiling revealed that molecular subgroups of patients undergoing allogeneic hematopoietic stem-cell transplantation for MDS may inform prognostic stratification and the selection of conditioning regimen. (Funded by the Edward P. Evans Foundation and others.).

Inhibiting cytoplasmic accumulation of HuR synergizes genotoxic agents in urothelial carcinoma of the bladder

HuR, an RNA-binding protein, post-transcriptionally regulates nearly 4% of encoding proteins implicated in cell survival. Here we show that HuR is required for the efficacy of chemotherapies in urothelial carcinoma of the bladder. We identify pyrvinium pamoate, an FDA-approved anthelminthic drug, as a novel HuR inhibitor that dose-dependently inhibited cytoplasmic accumulation of HuR. Combining pyrvinium pamoate with chemotherapeutic agents (e.g. cisplatin, doxorubicin, vincristine and oxaliplatin) not only led to enhanced cytotoxicity in bladder cancer cells but also synergistically suppressed the growth of patient-derived bladder tumor xenografts in mice (P < 0.001). Mechanistically, pyrvinium pamoate promoted nuclear import of HuR by activating the AMP-activated kinase/importin α1 cascade and blocked HuR nucleo-cytoplasmic translocation by inhibiting the checkpoint kinase1/cyclin-dependent kinase 1 pathway. Notably, pyrvinium pamoate-additive treatment increased DNA double-strand breaks as indicated by elevated γH2AX expression, suggesting an involvement of DNA damage response. We further found that pyrvinium pamoate dramatically downregulated several key DNA repair genes in genotoxically-stressed cells, including DNA ligase IV and BRCA2, leading to unbearable genomic instability and cell death. Collectively, our findings are the first to characterize a clinical HuR inhibitor and provide a novel therapeutically tractable strategy by targeting cytoplasmic translocation of HuR for treatment of urothelial carcinoma of the bladder.

SOX17 increases the cisplatin sensitivity of an endometrial cancer cell line

Background

Endometrial cancer (EC) is the most common form of malignant gynecological tumor. Treatment with cisplatin (CDDP) is the mainstay of EC chemotherapy. The apoptotic machinery is regarded as an important etiological factor in chemoresistance. Recent evidence has suggested that overexpression of the transcription factor SOX17 prevented apoptosis in tumor cell lines. The effect of SOX17 on apoptosis in EC cisplatin chemoresistance remains unclear.

Methods

Immunohistochemistry and the reverse transcription-polymerase chain reaction were employed to detect gene expression in paraffin-embedded EC tissues and blood samples. The anti-proliferative ability of SOX17 on EC cells was assessed by MTT. Flow cytometric analysis was used to detect cell apoptosis by annexin V/PI double-staining. The expression of apoptosis-related proteins was analyzed by western blot. In the in vivo study, nude mice were subcutaneously injected with EC cells, and received cisplatin treatment through intraperitoneal chemotherapy. Apoptosis of in vivo samples was analyzed by TUNEL assay.

Results

SOX17 expression decreased the chemical resistance of EC cells to CDDP. HEC-1B cells with an elevated expression of SOX17 had a lower cell viability and higher apoptosis rate after cisplatin exposure. Overexpression SOX17 up-regulated wild type p53 after being exposed to cisplatin, while the expression of BCL2-associated X protein and cleaved caspase-3 simultaneously increased. Caspase-9 inhibitor reduced the efficacy of SOX17 in HEC-1B cells after cisplatin treatment. In the in vivo study, SOX17 overexpression clearly restrained the tumor growth and increased the cisplatin toxicity and apoptosis of tumor cells.

Conclusions

SOX17 is involved in the p53-mediated apoptosis pathway, and increases the sensitivity of HEC-1B cells to cisplatin.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-016-0304-7) contains supplementary material, which is available to authorized users.

Molecular pathogenesis of ovarian clear cell carcinoma

Ovarian clear cell carcinoma is a distinct subtype of epithelial ovarian cancer, characterized by an association with endometriosis, glycogen accumulation and resistance to chemotherapy. Key driver events, including ARID1A mutations and HNF1B overexpression, have been recently identified and their functional characterization is ongoing. Additionally, the role of glycogen in promoting the malignant phenotype is coming under scrutiny. Appreciation of the notion that ovarian clear cell carcinoma is essentially an ectopic uterine cancer will hopefully lead to improved animal models of the disease, in turn paving the way for effective treatments.

Mitochondrial dynamics regulating chemoresistance in gynecological cancers

Chemoresistance enables cancer cells to evade apoptotic stimuli and leads to poor clinical prognosis. It arises from dysregulation of signaling factors responsible for inducing cell proliferation and death and for modulating the microenvironment. In gynecologic cancers, p53 is a pivotal determinant of cisplatin sensitivity, while BCL-2 family members are associated with taxane sensitivity. Mitochondria fusion and fission dynamics are required for many mitochondrial functions and are also involved in mitochondria-mediated apoptosis, which is closely associated with chemosensitivity. Mitochondrial dynamics are controlled by a number of intracellular proteins, including fusion (Opa1 and mitofusion 1 and 2) and fission proteins (Drp1 and Fis1), which can be proapoptotic or antiapoptotic, depending on the cell types, status, and stimuli from the microenvironment. This paper describes the role of mitochondrial dynamics in the mechanism of chemoresistance and the evidence supporting a significant contribution of a hyperfusion state to chemoresistance in gynecological cancers. Moreover, we discuss our findings showing that enforced fission induces apoptosis of cancer cells and sensitizes them to chemotherapeutic agents. Understanding the regulation of mitochondrial dynamics in chemoresistance may provide insight into new biomarkers that better predict cancer chemosensitivity and may aid the development of effective therapeutic strategies for clinical management of gynecologic cancers.

Estrogen receptor α inhibitor activates the unfolded protein response, blocks protein synthesis, and induces tumor regression

Recurrent estrogen receptor α (ERα)-positive breast and ovarian cancers are often therapy resistant. Using screening and functional validation, we identified BHPI, a potent noncompetitive small molecule ERα biomodulator that selectively blocks proliferation of drug-resistant ERα-positive breast and ovarian cancer cells. In a mouse xenograft model of breast cancer, BHPI induced rapid and substantial tumor regression. Whereas BHPI potently inhibits nuclear estrogen-ERα-regulated gene expression, BHPI is effective because it elicits sustained ERα-dependent activation of the endoplasmic reticulum (EnR) stress sensor, the unfolded protein response (UPR), and persistent inhibition of protein synthesis. BHPI distorts a newly described action of estrogen-ERα: mild and transient UPR activation. In contrast, BHPI elicits massive and sustained UPR activation, converting the UPR from protective to toxic. In ERα(+) cancer cells, BHPI rapidly hyperactivates plasma membrane PLCγ, generating inositol 1,4,5-triphosphate (IP3), which opens EnR IP3R calcium channels, rapidly depleting EnR Ca(2+) stores. This leads to activation of all three arms of the UPR. Activation of the PERK arm stimulates phosphorylation of eukaryotic initiation factor 2α (eIF2α), resulting in rapid inhibition of protein synthesis. The cell attempts to restore EnR Ca(2+) levels, but the open EnR IP3R calcium channel leads to an ATP-depleting futile cycle, resulting in activation of the energy sensor AMP-activated protein kinase and phosphorylation of eukaryotic elongation factor 2 (eEF2). eEF2 phosphorylation inhibits protein synthesis at a second site. BHPI's novel mode of action, high potency, and effectiveness in therapy-resistant tumor cells make it an exceptional candidate for further mechanistic and therapeutic exploration.

Pharmacological reactivation of p53 as a strategy to treat cancer

It has been confirmed through studies using the technique of unbiased sequencing that the TP53 tumour suppressor is the most frequently inactivated gene in cancer. This finding, together with results from earlier studies, provides compelling evidence for the idea that p53 ablation is required for the development and maintenance of tumours. Genetic reconstitution of the function of p53 leads to the suppression of established tumours as shown in mouse models. This strongly supports the notion that p53 reactivation by small molecules could provide an efficient strategy to treat cancer. In this review, we summarize recent advances in the development of small molecules that restore the function of mutant p53 by different mechanisms, including stabilization of its folding by Apr-246, which is currently being tested in a Phase II clinical trial. We discuss several classes of compounds that reactivate wild-type p53, such as Mdm2 inhibitors, which are currently undergoing clinical testing, MdmX inhibitors and molecules targeting factors upstream of Mdm2/X or p53 itself. Finally, we consider the clinical applications of compounds targeting p53 and the p53 pathway.

Wip1 phosphatase in breast cancer

Understanding the factors contributing to tumor initiation, progression and evolution is of paramount significance. Among them, wild-type p53-induced phosphatase 1 (Wip1) is emerging as an important oncogene by virtue of its negative control on several key tumor suppressor pathways. Originally discovered as a p53-regulated gene, Wip1 has been subsequently found amplified and more recently mutated in a significant fraction of human cancers including breast tumors. Recent development in the field further uncovered the utility of anti-Wip1-directed therapies in delaying tumor onset or in reducing the tumor burden. Furthermore, Wip1 could be an important factor that contributes to tumor heterogeneity, suggesting that its inhibition may decrease the rate of cancer evolution. These effects depend on several signaling pathways modulated by Wip1 phosphatase in a spatial and temporal manner. In this review we discuss the recent development in understanding how Wip1 contributes to tumorigenesis with its relevance to breast cancer.

Targeting PPM1D by lentivirus-mediated RNA interference inhibits the tumorigenicity of bladder cancer cells

Protein phosphatase magnesium/manganese-dependent 1D (PPM1D) is a p53-induced phosphatase that functions as a negative regulator of stress response pathways and has oncogenic properties. However, the functional role of PPM1D in bladder cancer (BC) remains largely unknown. In the present study, lentivirus vectors carrying small hairpin RNA (shRNA) targeting PPM1D were used to explore the effects of PPM1D knockdown on BC cell proliferation and tumorigenesis. shRNA-mediated knockdown of PPM1D significantly inhibited cell growth and colony forming ability in the BC cell lines 5637 and T24. Flow cytometric analysis showed that PPM1D silencing increased the proportion of cells in the G0/G1 phase. Downregulation of PPM1D also inhibited 5637 cell tumorigenicity in nude mice. The results of the present study suggest that PPM1D plays a potentially important role in BC tumorigenicity, and lentivirus-mediated delivery of shRNA against PPM1D might be a promising therapeutic strategy for the treatment of BC.

Akt confers cisplatin chemoresistance in human gynecological carcinoma cells by modulating PPM1D stability

Ovarian cancer (OVCA) and cervical cancer (CECA) are lethal gynecological malignancies. Cisplatin (CDDP) and platinum derivatives are first line chemotherapeutics and their resistance impedes successful treatment. Understanding the molecular dysregulation underlying chemoresistance is important in developing rational therapeutic strategies. We have established that Protein Phosphatase Magnesium-dependent 1 D (PPM1D) confers CDDP resistance in gynecological cancer cells by deactivating p53. However, whether CDDP regulates intra-cellular PPM1D localization and whether this regulation is different between chemosensitive and chemoresistant cancer cells is unknown. Moreover, whether Akt regulates PPM1D in the context of CDDP resistance has not been studied. To illustrate the role of PPM1D in gynecological cancer cell chemoresistance and its regulation by Akt we have demonstrated that: (a) CDDP induced PPM1D down-regulation through proteasomal degradation in sensitive CECA cells; (b) CDDP induced PPM1D nuclear localization in resistant CECA cells, and nuclear exclusion in sensitive CECA cells and OVCA xenografts; (c) Over-expression of active Akt in sensitive CECA cells stabilized PPM1D content through inhibition of CDDP-induced PPM1D down-regulation; (d) Inhibition of Akt activity in resistant OVCA cells leads to decreased PPM1D stability and CDDP-induced down-regulation in resistant CECA cells; and (e) PPM1D is highly expressed in human ovarian tumor subtypes and in a tissue microarray panel of human ovarian tumors. In conclusion, we have established that PPM1D plays an important role in promoting CDDP resistance and as a novel downstream target of Akt, PPM1D mediates its action in conferring CDDP resistance in gynecological cancer cells.

Phytochemicals: a multitargeted approach to gynecologic cancer therapy

Gynecologic cancers constitute the fourth most common cancer type in women. Treatment outcomes are dictated by a multitude of factors, including stage at diagnosis, tissue type, and overall health of the patient. Current therapeutic options include surgery, radiotherapy, and chemotherapy, although significant unmet medical needs remain in regard to side effects and long-term survival. The efficacy of chemotherapy is influenced by cellular events such as the overexpression of oncogenes and downregulation of tumor suppressors, which together determine apoptotic responses. Phytochemicals are a broad class of natural compounds derived from plants, a number of which exhibit useful bioactive effects toward these pathways. High-throughput screening methods, rational modification, and developments in regulatory policies will accelerate the development of novel therapeutics based on these compounds, which will likely improve overall survival and quality of life for patients.

The malignancy of metastatic ovarian cancer cells is increased on soft matrices through a mechanosensitive Rho-ROCK pathway

Although current treatments for localized ovarian cancer are highly effective, this cancer still remains the most lethal gynecological malignancy, largely owing to the fact that it is often detected only after tumor cells leave the primary tumor. Clinicians have long noted a clear predilection for ovarian cancer to metastasize to the soft omentum. Here, we show that this tropism is due not only to chemical signals but also mechanical cues. Metastatic ovarian cancer cells (OCCs) preferentially adhere to soft microenvironments and display an enhanced malignant phenotype, including increased migration, proliferation and chemoresistance. To understand the cell-matrix interactions that are used to sense the substrate rigidity, we utilized traction force microscopy (TFM) and found that, on soft substrates, human OCCs increased both the magnitude of traction forces as well as their degree of polarization. After culture on soft substrates, cells underwent morphological elongation characteristic of epithelial-to-mesenchymal transition (EMT), which was confirmed by molecular analysis. Consistent with the idea that mechanical cues are a key determinant in the spread of ovarian cancer, the observed mechanosensitivity was greatly decreased in less-metastatic OCCs. Finally, we demonstrate that this mechanical tropism is governed through a Rho-ROCK signaling pathway.

The regulatory roles of phosphatases in cancer

The relevance of potentially reversible post-translational modifications required for controlling cellular processes in cancer is one of the most thriving arenas of cellular and molecular biology. Any alteration in the balanced equilibrium between kinases and phosphatases may result in development and progression of various diseases, including different types of cancer, though phosphatases are relatively under-studied. Loss of phosphatases such as PTEN (phosphatase and tensin homologue deleted on chromosome 10), a known tumour suppressor, across tumour types lends credence to the development of phosphatidylinositol 3-kinase inhibitors alongside the use of phosphatase expression as a biomarker, though phase 3 trial data are lacking. In this review, we give an updated report on phosphatase dysregulation linked to organ-specific malignancies.

Ovarian cancer stem cell-specific gene expression profiling and targeted drug prescreening

Cancer stem cells, with unlimited self-renewal potential and other stem cell characteristics, occur in several types of cancer, including ovarian cancer (OvC). Although CSCs can cause tumor initiation, malignant proliferation, relapse and multi-drug resistance, ways to eliminate them remain unknown. In the present study, we compared ovarian cancer stem cell (OVCSC) expression profiles in normal ovarian surface epithelium and ovarian cells from patients with advanced disease to identify key pathways and specific molecular signatures involved in OVC progression and to prescreen candidate small-molecule compounds with anti-OVCSC activity. Comparison of genome-wide expression profiles of OvC stemness groups with non-stemness controls revealed 6495, 1347 and 509 differentially expressed genes in SDC, SP1 and SP2 groups, respectively, with a cut-off of fold-change set at >1.5 and P<0.05. NAB1 and NPIPL1 were commonly upregulated whereas PROS1, GREB1, KLF9 and MTUS1 were commonly downregulated in all 3 groups. Most differentially expressed genes consistently clustered with molecular functions such as protein receptor binding, kinase activity and chemo-repellent activity. These genes regulate cellular components such as centrosome, plasma membrane receptors, and basal lamina, and may participate in biological processes such as cell cycle regulation, chemoresistance and stemness induction. Key Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways such as ECM receptor, ErbB signaling, endocytosis and adherens junction pathways were enriched. Gene co-expression extrapolation screening by the Connectivity Map revealed several small-molecule compounds (such as SC-560, disulfiram, thapsigargin, esculetin and cinchonine) with potential anti-OVCSC properties targeting OVCSC signature genes. We identified several key CSC features and specific regulation networks in OVCSCs and predicted several small molecules with potential anti-OVCSC pharmacological properties, which may aid the development of OVCSC-specific drugs.

Inauhzin sensitizes p53-dependent cytotoxicity and tumor suppression of chemotherapeutic agents

Toxicity and chemoresistance are two major issues to hamper the success of current standard tumor chemotherapy. Combined therapy of agents with different mechanisms of action is a feasible and effective means to minimize the side effects and avoid the resistance to chemotherapeutic drugs while improving the antitumor effects. As the most essential tumor suppressor, p53 or its pathway has been an attractive target to develop a new type of molecule-targeting anticancer therapy. Recently, we identified a small molecule, Inauhzin (INZ), which can specifically activate p53 by inducing its deacetylation. In this study, we tested if combination with INZ could sensitize tumor cells to the current chemotherapeutic drugs, cisplatin (CIS) and doxorubicin (DOX). We found that compared with any single treatment, combination of lower doses of INZ and CIS or DOX significantly promoted apoptosis and cell growth inhibition in human non-small lung cancer and colon cancer cell lines in a p53-dependent fashion. This cooperative effect between INZ and CIS on tumor suppression was also confirmed in a xenograft tumor model. Therefore, this study suggests that specifically targeting the p53 pathway could enhance the sensitivity of cancer cells to chemotherapeutic agents and markedly reduce the doses of the chemotherapy, possibly decreasing its adverse side effects.

The mTORC2 component rictor contributes to cisplatin resistance in human ovarian cancer cells

Resistance to cisplatin-based therapy is a major cause of treatment failure in human ovarian cancer. A better understanding of the mechanisms of cisplatin resistance will offer new insights for novel therapeutic strategies for this deadly disease. Akt and p53 are determinants of cisplatin sensitivity. Rictor is a component of mTOR protein kinase complex 2, which is required for Akt phosphorylation (Ser473) and full activation. However, the precise role of rictor and the relationship between rictor and p53 in cisplatin resistance remains poorly understood. Here, using sensitive wild-type p53 (OV2008 and A2780s), resistant wild-type p53 (C13* and OVCAR433), and p53 compromised (A2780cp, OCC1, and SKOV-3) ovarian cancer cells, we have demonstrated that (i) rictor is a determinant of cisplatin resistance in chemosensitive human ovarian cancer cells; (ii) cisplatin down-regulates rictor content by caspase-3 cleavage and proteasomal degradation; (iii) rictor down-regulation sensitizes chemo-resistant ovarian cancer cells to cisplatin-induced apoptosis in a p53-dependent manner; (iv) rictor suppresses cisplatin-induced apoptosis and confers resistance by activating and stabilizing Akt. These findings extend current knowledge on the molecular and cellular basis of cisplatin resistance and provide a rationale basis for rictor as a potential therapeutic target for chemoresistant ovarian cancer.

Ubiquitin E3 ligase CRL4(CDT2/DCAF2) as a potential chemotherapeutic target for ovarian surface epithelial cancer

Cullin-RING ubiquitin ligases (CRLs) are the largest family of E3 ligases and require cullin neddylation for their activation. The NEDD8-activating enzyme inhibitor MLN4924 reportedly blocked cullin neddylation and inactivated CRLs, which resulted in apoptosis induction and tumor suppression. However, CRL roles in ovarian cancer cell survival and the ovarian tumor repressing effects of MLN4924 are unknown. We show here that CRL4 components are highly expressed in human epithelial ovarian cancer tissues. MLN4924-induced DNA damage, cell cycle arrest, and apoptosis in ovarian cancer cells in a time- and dose-dependent manner. In addition, MLN4924 sensitized ovarian cancer cells to other chemotherapeutic drug treatments. Depletion of CRL4 components Roc1/2, Cul4a, and DDB1 had inhibitory effects on ovarian cancer cells similar to MLN4924 treatment, which suggested that CRL4 inhibition contributed to the chemotherapeutic effect of MLN4924 in ovarian cancers. We also investigated for key CRL4 substrate adaptors required for ovarian cancer cells. Depleting Vprbp/Dcaf1 did not significantly affect ovarian cancer cell growth, even though it was expressed by ovarian cancer tissues. However, depleting Cdt2/Dcaf2 mimicked the pharmacological effects of MLN4924 and caused the accumulation of its substrate, CDT1, both in vitro and in vivo. MLN4924-induced DNA damage and apoptosis were partially rescued by Cdt1 depletion, suggesting that CRL4(CDT2) repression and CDT1 accumulation were key biochemical events contributing to the genotoxic effects of MLN4924 in ovarian cancer cells. Taken together, these results indicate that CRL4(CDT2) is a potential drug target in ovarian cancers and that MLN4924 may be an effective anticancer agent for targeted ovarian cancer therapy.

Wip1 suppresses apoptotic cell death through direct dephosphorylation of BAX in response to γ-radiation

Wild-type p53-induced phosphatase 1 (Wip1) is a p53-inducible serine/threonine phosphatase that switches off DNA damage checkpoint responses by the dephosphorylation of certain proteins (i.e. p38 mitogen-activated protein kinase, p53, checkpoint kinase 1, checkpoint kinase 2, and uracil DNA glycosylase) involved in DNA repair and the cell cycle checkpoint. Emerging data indicate that Wip1 is amplified or overexpressed in various human tumors, and its detection implies a poor prognosis. In this study, we show that Wip1 interacts with and dephosphorylates BAX to suppress BAX-mediated apoptosis in response to γ-irradiation in prostate cancer cells. Radiation-resistant LNCaP cells showed dramatic increases in Wip1 levels and impaired BAX movement to the mitochondria after γ-irradiation, and these effects were reverted by a Wip1 inhibitor. These results show that Wip1 directly interacts with and dephosphorylates BAX. Dephosphorylation occurs at threonines 172, 174 and 186, and BAX proteins with mutations at these sites fail to translocate efficiently to the mitochondria following cellular γ-irradiation. Overexpression of Wip1 and BAX, but not phosphatase-dead Wip1, in BAX-deficient cells strongly reduces apoptosis. Our results suggest that BAX dephosphorylation of Wip1 phosphatase is an important regulator of resistance to anticancer therapy. This study is the first to report the downregulation of BAX activity by a protein phosphatase.

Piceatannol enhances cisplatin sensitivity in ovarian cancer via modulation of p53, X-linked inhibitor of apoptosis protein (XIAP), and mitochondrial fission

Resistance to cisplatin (CDDP) in ovarian cancer (OVCA) arises from the dysregulation of tumor suppressors and survival signals. During genotoxic challenge, these factors can be influenced by secondary agents that facilitate the induction of apoptosis. Piceatannol is a natural metabolite of the stilbene resveratrol found in grapes and is converted from its parent compound by the enzyme CYP1BA1 p450. It has been hypothesized to exert specific effects against various cellular targets; however, its ability to influence CDDP resistance in cancer cells has not been investigated to date. Here, we show that piceatannol is a potent enhancer of CDDP sensitivity in OVCA, and this effect is achieved through the modulation of several major determinants of chemoresistance. Piceatannol enhances p53-mediated expression of the pro-apoptotic protein NOXA, increases XIAP degradation via the ubiquitin-proteasome pathway, and enhances caspase-3 activation. This response is associated with an increase in Drp1-dependent mitochondrial fission, leading to more effective induction of apoptosis. In vivo studies using a mouse model of OVCA reveal that a number of these changes occur in association with a greater overall reduction in tumor weight when mice are treated with both piceatannol and CDDP, in comparison to treatment with either agent alone. Taken together, these findings demonstrate the potential application of piceatannol to enhance CDDP sensitivity in OVCA, and it acts on p53, XIAP, and mitochondrial fission.