Mitochondrial proteomic analysis of cisplatin resistance in ovarian cancer

A proteomic landscape of pharmacologic perturbations for functional relevance

Pharmacological perturbation studies based on protein-level signatures are fundamental for drug discovery. In the present study, we used a mass spectrometry (MS)-based proteomic platform to profile the whole proteome of the breast cancer MCF7 cell line under stress induced by 78 bioactive compounds. The integrated analysis of perturbed signal abundance revealed the connectivity between phenotypic behaviors and molecular features in cancer cells. Our data showed functional relevance in exploring the novel pharmacological activity of phenolic xanthohumol, as well as the noncanonical targets of clinically approved tamoxifen, lovastatin, and their derivatives. Furthermore, the rational design of synergistic inhibition using a combination of histone methyltransferase and topoisomerase was identified based on their complementary drug fingerprints. This study provides rich resources for the proteomic landscape of drug responses for precision therapeutic medicine.

Metastasis suppressor genes in clinical practice: are they druggable?

Since the identification of NM23 (now called NME1) as the first metastasis suppressor gene (MSG), a small number of other gene products and non-coding RNAs have been identified that suppress specific parameters of the metastatic cascade, yet which have little or no ability to regulate primary tumor initiation or maintenance. MSG can regulate various pathways or cell biological functions such as those controlling mitogen-activated protein kinase pathway mediators, cell-cell and cell-extracellular matrix protein adhesion, cytoskeletal architecture, G-protein-coupled receptors, apoptosis, and transcriptional complexes. One defining facet of this gene class is that their expression is typically downregulated, not mutated, in metastasis, such that any effective therapeutic intervention would involve their re-expression. This review will address the therapeutic targeting of MSG, once thought to be a daunting task only facilitated by ectopically re-expressing MSG in metastatic cells in vivo. Examples will be cited of attempts to identify actionable oncogenic pathways that might suppress the formation or progression of metastases through the re-expression of specific metastasis suppressors.

Mass Spectrometry-based Proteomics of Epithelial Ovarian Cancers: a Clinical Perspective

Increasing proteomic studies focused on epithelial ovarian cancer (EOC) have attempted to identify early disease biomarkers, establish molecular stratification, and discover novel druggable targets. Here we review these recent studies from a clinical perspective. Multiple blood proteins have been used clinically as diagnostic markers. The ROMA test integrates CA125 and HE4, while the OVA1 and OVA2 tests analyze multiple proteins identified by proteomics. Targeted proteomics has been widely used to identify and validate potential diagnostic biomarkers in EOCs, but none has yet been approved for clinical adoption. Discovery proteomic characterization of bulk EOC tissue specimens has uncovered a large number of dysregulated proteins, proposed new stratification schemes, and revealed novel targets of therapeutic potential. A major hurdle facing clinical translation of these stratification schemes based on bulk proteomic profiling is intra-tumor heterogeneity, namely that single tumor specimens may harbor molecular features of multiple subtypes. We reviewed over 2500 interventional clinical trials of ovarian cancers since 1990, and cataloged 22 types of interventions adopted in these trials. Among 1418 clinical trials which have been completed or are not recruiting new patients, about 50% investigated chemotherapies. Thirty-seven clinical trials are at phase 3 or 4, of which 12 focus on PARP, 10 on VEGFR, 9 on conventional anti-cancer agents, and the remaining on sex hormones, MEK1/2, PD-L1, ERBB, and FRα. Although none of the foregoing therapeutic targets were discovered by proteomics, newer targets discovered by proteomics, including HSP90 and cancer/testis antigens, are being tested also in clinical trials. To accelerate the translation of proteomic findings to clinical practice, future studies need to be designed and executed to the stringent standards of practice-changing clinical trials. We anticipate that the rapidly evolving technology of spatial and single-cell proteomics will deconvolute the intra-tumor heterogeneity of EOCs, further facilitating their precise stratification and superior treatment outcomes.

Proteomic alterations associated with residual disease in neoadjuvant chemotherapy treated ovarian cancer tissues

BACKGROUND

Optimal cytoreduction to no residual disease (R0) correlates with improved disease outcome for high-grade serous ovarian cancer (HGSOC) patients. Treatment of HGSOC patients with neoadjuvant chemotherapy, however, may select for tumor cells harboring alterations in hallmark cancer pathways including metastatic potential. This study assessed this hypothesis by performing proteomic analysis of matched, chemotherapy naïve and neoadjuvant chemotherapy (NACT)-treated HGSOC tumors obtained from patients who had suboptimal (R1, n = 6) versus optimal (R0, n = 14) debulking at interval debulking surgery (IDS).

METHODS

Tumor epithelium was harvested by laser microdissection from formalin-fixed, paraffin-embedded tissues from matched, pre- and post-NACT treated tumors for twenty HGSOC patients and analyzed by quantitative mass spectrometry-based proteomics.

RESULTS

Differential analysis of patient matched pre- and post-NACT treated tumors revealed proteins associated with cell survival and metabolic signaling to be significantly altered in post-NACT treated tumor cells. Comparison of pre-NACT treated tumors from suboptimal (R1) versus optimally (R0) debulked patients identified proteins associated with tumor cell viability and invasion signaling enriched in R1 patients. We identified five proteins altered between R1 and R0 patients in pre- NACT treated tumors that significantly correlated with PFS in an independent cohort of HGSOC patients, including Fermitin family homolog 2 (FERMT2), a protein elevated in R1 that correlated with disease progression in HGSOC patients (multivariate Cox HR = 1.65, Wald p = 0.022) and increased metastatic potential in solid-tumor malignancies.

CONCLUSIONS

This study identified distinct proteome profiles in patient matched pre- and post-NACT HGSOC tumors that correlate with NACT resistance and that may predict residual disease status at IDS that collectively warrant further pre-clinical investigation.

Pan-cancer analysis of the prognosis and immunological role of AKAP12: A potential biomarker for resistance to anti-VEGF inhibitors

The primary or acquired resistance to anti-VEGF inhibitors remains a common problem in cancer treatment. Therefore, identifying potential biomarkers enables a better understanding of the precise mechanism. Through the GEO database, three profiles associated with bevacizumab (BV) resistance to ovarian cancer, glioma, and non-small-cell lung carcinoma, respectively, were collected for the screening process, and two genes were found. A-kinase anchor protein 12 (AKAP12), one of these two genes, correlates with tumorigenesis of some cancers. However, the role of AKAP12 in pan-cancer remains poorly defined. The present study first systematically analyzed the association of AKAP12 with anti-VEGF inhibitors’ sensitivity, clinical prognosis, DNA methylation, protein phosphorylation, and immune cell infiltration across various cancers via bioinformatic tools. We found that AKAP12 was upregulated in anti-VEGF therapy-resistant cancers, including ovarian cancer (OV), glioblastoma (GBM), lung cancer, and colorectal cancer (CRC). A high AKAP12 expression revealed dismal prognoses in OV, GBM, and CRC patients receiving anti-VEGF inhibitors. Moreover, AKAP12 expression was negatively correlated with cancer sensitivity towards anti-VEGF therapy. Clinical prognosis analysis showed that AKAP12 expression predicted worse prognoses of various cancer types encompassing colon adenocarcinoma (COAD), OV, GBM, and lung squamous cell carcinoma (LUSC). Gene mutation status may be a critical cause for the involvement of AKAP12 in resistance. Furthermore, lower expression of AKAP12 was detected in nearly all cancer types, and hypermethylation may explain its decreased expression. A decreased phosphorylation of T1760 was observed in breast cancer, clear-cell renal cell carcinoma, and lung adenocarcinoma. For the immunologic significance, AKAP12 was positively related to the abundance of pro-tumor cancer-associated fibroblasts (CAFs) in various types of cancer. The results of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis suggested that “cell junction organization” and “MAPK pathway” participated in the effect of AKAP12. Importantly, we discovered that AKAP12 expression was greatly associated with metastasis of lung adenocarcinoma as well as differential and angiogenesis of retinoblastoma through investigating the single-cell sequencing data. Our study showed that the dual role of AKAP12 in various cancers and AKAP12 could serve as a biomarker of anti-VEGF resistance in OV, GBM, LUSC, and COAD.

Chemoresistant Cancer Cell Lines Are Characterized by Migratory, Amino Acid Metabolism, Protein Catabolism and IFN1 Signalling Perturbations

Simple Summary

While chemoresistance remains a major barrier to improving the outcomes for patients with ovarian cancer, the molecular features, and associated biological functions, which underpin chemoresistance in ovarian cancer remain poorly understood. In this study we aimed to provide insight into the proteins and metabolites, and their associated biological pathways, which play a role in conferring chemoresistance to ovarian cancer. Through mass spectrometry analysis comparing the proteome and metabolome of chemosensitive vs chemoresistant ovarian cancer cell lines we revealed numerous perturbations in signalling and metabolic pathways in chemoresistant cells. Further comparison to primary cells taken from patients with chemoresistant or chemosensitive disease identified a shared dysregulation in cytokine and type 1 interferon signalling. Our research sets the foundation for a deeper understanding of the proteomic and metabolomic features of chemoresistance and identifies type 1 interferon signalling as a common feature of chemoresistance.

Abstract

Chemoresistance remains the major barrier to effective ovarian cancer treatment. The molecular features and associated biological functions of this phenotype remain poorly understood. We developed carboplatin-resistant cell line models using OVCAR5 and CaOV3 cell lines with the aim of identifying chemoresistance-specific molecular features. Chemotaxis and CAM invasion assays revealed enhanced migratory and invasive potential in OVCAR5-resistant, compared to parental cell lines. Mass spectrometry analysis was used to analyse the metabolome and proteome of these cell lines, and was able to separate these populations based on their molecular features. It revealed signalling and metabolic perturbations in the chemoresistant cell lines. A comparison with the proteome of patient-derived primary ovarian cancer cells grown in culture showed a shared dysregulation of cytokine and type 1 interferon signalling, potentially revealing a common molecular feature of chemoresistance. A comprehensive analysis of a larger patient cohort, including advanced in vitro and in vivo models, promises to assist with better understanding the molecular mechanisms of chemoresistance and the associated enhancement of migration and invasion.

Applications of Proteomics in Ovarian Cancer: Dawn of a New Era

The ability to identify ovarian cancer (OC) at its earliest stages remains a challenge. The patients present an advanced stage at diagnosis. This heterogeneous disease has distinguishable etiology and molecular biology. Next-generation sequencing changed clinical diagnostic testing, allowing assessment of multiple genes, simultaneously, in a faster and cheaper manner than sequential single gene analysis. Technologies of proteomics, such as mass spectrometry (MS) and protein array analysis, have advanced the dissection of the underlying molecular signaling events and the proteomic characterization of OC. Proteomics analysis of OC, as well as their adaptive responses to therapy, can uncover new therapeutic choices, which can reduce the emergence of drug resistance and potentially improve patient outcomes. There is an urgent need to better understand how the genomic and epigenomic heterogeneity intrinsic to OC is reflected at the protein level, and how this information could potentially lead to prolonged survival.

Lon upregulation contributes to cisplatin resistance by triggering NCLX-mediated mitochondrial Ca2+ release in cancer cells

Mitochondria are the major organelles in sensing cellular stress and inducing the response for cell survival. Mitochondrial Lon has been identified as an important stress protein involved in regulating proliferation, metastasis, and apoptosis in cancer cells. However, the mechanism of retrograde signaling by Lon on mitochondrial DNA (mtDNA) damage remains to be elucidated. Here we report the role of Lon in the response to cisplatin-induced mtDNA damage and oxidative stress, which confers cancer cells on cisplatin resistance via modulating calcium levels in mitochondria and cytosol. First, we found that cisplatin treatment on oral cancer cells caused oxidative damage of mtDNA and induced Lon expression. Lon overexpression in cancer cells decreased while Lon knockdown sensitized the cytotoxicity towards cisplatin treatment. We further identified that cisplatin-induced Lon activates the PYK2-SRC-STAT3 pathway to stimulate Bcl-2 and IL-6 expression, leading to the cytotoxicity resistance to cisplatin. Intriguingly, we found that activation of this pathway is through an increase of intracellular calcium (Ca²⁺) via NCLX, a mitochondrial Na⁺/Ca²⁺ exchanger. We then verified that NCLX expression is dependent on Lon levels; Lon interacts with and activates NCLX activity. NCLX inhibition increased the level of mitochondrial calcium and sensitized the cytotoxicity to cisplatin in vitro and in vivo. In summary, mitochondrial Lon-induced cisplatin resistance is mediated by calcium release into cytosol through NCLX, which activates calcium-dependent PYK2-SRC-STAT3-IL-6 pathway. Thus, our work uncovers the novel retrograde signaling by mitochondrial Lon on resistance to cisplatin-induced mtDNA stress, indicating the potential use of Lon and NCLX inhibitors for better clinical outcomes in chemoresistant cancer patients.

Metalloproteomics for Biomedical Research: Methodology and Applications

Metals are essential components in life processes and participate in many important biological processes. Dysregulation of metal homeostasis is correlated with many diseases. Metals are also frequently incorporated into diagnosis and therapeutics. Understanding of metal homeostasis under (patho)physiological conditions and the molecular mechanisms of action of metallodrugs in biological systems has positive impacts on human health. As an emerging interdisciplinary area of research, metalloproteomics involves investigating metal-protein interactions in biological systems at a proteome-wide scale, has received growing attention, and has been implemented into metal-related research. In this review, we summarize the recent advances in metalloproteomics methodologies and applications. We also highlight emerging single-cell metalloproteomics, including time-resolved inductively coupled plasma mass spectrometry, mass cytometry, and secondary ion mass spectrometry. Finally, we discuss future perspectives in metalloproteomics, aiming to attract more original research to develop more advanced methodologies, which could be utilized rapidly by biochemists or biologists to expand our knowledge of how metal functions in biology and medicine. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The Clinical and Theranostic Values of Activated Leukocyte Cell Adhesion Molecule (ALCAM)/CD166 in Human Solid Cancers

Simple Summary

ALCAM (activated leukocyte cell adhesion molecule) is an important regulator in human cancers, particularly solid tumours. Its expression in cancer tissues has prognostic values depending on cancer types and is also linked to distant metastases. A truncated form, soluble form of ALCAM (sALCAM) in circulation has been suggested to be a prognostic indicator and a potential therapeutic tool. This article summarises recent findings and progress in ALCAM and its involvement in cancer, with a primary focus on its clinical connections and therapeutic values.

Abstract

Activated leukocyte cell adhesion molecule (ALCAM), also known as CD166, is a cell adhesion protein that is found in multiple cell types. ALCAM has multiple and diverse roles in various physiological and pathological conditions, including inflammation and cancer. There has been compelling evidence of ALCAM’s prognostic value in solid cancers, indicating that it is a potential therapeutic target. The present article overviews the recent findings and progress in ALCAM and its involvement in cancer, with a primary focus on its clinical connections in cancer and therapeutic values.

MASS SPECTROMETRY-BASED MITOCHONDRIAL PROTEOMICS IN HUMAN OVARIAN CANCERS

The prominent characteristics of mitochondria are highly dynamic and regulatory, which have crucial roles in cell metabolism, biosynthetic, senescence, apoptosis, and signaling pathways. Mitochondrial dysfunction might lead to multiple serious diseases, including cancer. Therefore, identification of mitochondrial proteins in cancer could provide a global view of tumorigenesis and progression. Mass spectrometry-based quantitative mitochondrial proteomics fulfils this task by enabling systems-wide, accurate, and quantitative analysis of mitochondrial protein abundance, and mitochondrial protein posttranslational modifications (PTMs). Multiple quantitative proteomics techniques, including isotope-coded affinity tag, stable isotope labeling with amino acids in cell culture, isobaric tags for relative and absolute quantification, tandem mass tags, and label-free quantification, in combination with different PTM-peptide enrichment methods such as TiO₂ enrichment of tryptic phosphopeptides and antibody enrichment of other PTM-peptides, increase flexibility for researchers to study mitochondrial proteomes. This article reviews isolation and purification of mitochondria, quantitative mitochondrial proteomics, quantitative mitochondrial phosphoproteomics, mitochondrial protein-involved signaling pathway networks, mitochondrial phosphoprotein-involved signaling pathway networks, integration of mitochondrial proteomic and phosphoproteomic data with whole tissue proteomic and transcriptomic data and clinical information in ovarian cancers (OC) to in-depth understand its molecular mechanisms, and discover effective mitochondrial biomarkers and therapeutic targets for predictive, preventive, and personalized treatment of OC. This proof-of-principle model about OC mitochondrial proteomics is easily implementable to other cancer types. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

Mitochondrial APE1 promotes cisplatin resistance by downregulating ROS in osteosarcoma

Apurinic/apyrimidinic endonuclease 1 (APE1) is a primary nuclear-localized multifunctional protein in osteosarcoma. However, the cytoplasmic localization of APE1 was found to be functional and to increase with cisplatin resistance, yet the molecular mechanism is unknown. In the present study, we explored the cisplatin resistance mechanism in osteosarcoma from the new perspective of APE1 extranuclear biological activity. Using cisplatin-resistant and cisplatin-sensitive osteosarcoma cell lines, we found that mitochondrial APE1 (mtAPE1) was overexpressed in cisplatin-resistant cells but not in sensitive cells. Overexpression of mtAPE1 reduced cisplatin-induced apoptosis, while knockdown of APE1 reversed this phenomenon and caused oxidative DNA damage via overproduction of reactive oxygen species (ROS). We further demonstrated that high mtAPE1 expression could downregulate ROS production by decreasing the phosphorylation of Rac1 (p-Rac1), further promoting cisplatin resistance in osteosarcoma. Our findings suggest that mitochondrial APE1 promotes cisplatin resistance by decreasing ROS generation, which may provide new ideas for researching the molecular mechanism of osteosarcoma chemoresistance and strategies to overcome cisplatin resistance in osteosarcoma.

Chemotherapy-Induced Distal Enhancers Drive Transcriptional Programs to Maintain the Chemoresistant State in Ovarian Cancer

Chemoresistance is driven by unique regulatory networks in the genome that are distinct from those necessary for cancer development. Here, we investigate the contribution of enhancer elements to cisplatin resistance in ovarian cancers. Epigenome profiling of multiple cellular models of chemoresistance identified unique sets of distal enhancers, super-enhancers (SE), and their gene targets that coordinate and maintain the transcriptional program of the platinum-resistant state in ovarian cancer. Pharmacologic inhibition of distal enhancers through small-molecule epigenetic inhibitors suppressed the expression of their target genes and restored cisplatin sensitivity in vitro and in vivo. In addition to known drivers of chemoresistance, our findings identified SOX9 as a critical SE-regulated transcription factor that plays a critical role in acquiring and maintaining the chemoresistant state in ovarian cancer. The approach and findings presented here suggest that integrative analysis of epigenome and transcriptional programs could identify targetable key drivers of chemoresistance in cancers. SIGNIFICANCE: Integrative genome-wide epigenomic and transcriptomic analyses of platinum-sensitive and -resistant ovarian lines identify key distal regulatory regions and associated master regulator transcription factors that can be targeted by small-molecule epigenetic inhibitors.

Chemotherapy Resistance in Advanced Ovarian Cancer Patients

Ovarian cancer is the seventh most common gynaecologic malignancy seen in women. Majority of the patients with ovarian cancer are diagnosed at the advanced stage making prognosis poor. The standard management of advanced ovarian cancer includes tumour debulking surgery followed by chemotherapy. Various types of chemotherapeutic regimens have been used to treat advanced ovarian cancer, but the most promising and the currently used standard first-line treatment is carboplatin and paclitaxel. Despite improved clinical response and survival to this combination of chemotherapy, numerous patients either undergo relapse or succumb to the disease as a result of chemotherapy resistance. To understand this phenomenon at a cellular level, various macromolecules such as DNA, messenger RNA and proteins have been developed as biomarkers for chemotherapy response. This review comprehensively summarizes the problem that pertains to chemotherapy resistance in advanced ovarian cancer and provides a good overview of the various biomarkers that have been developed in this field.

Overcoming platinum-acquired resistance in ovarian cancer patient-derived xenografts

Background:

Epithelial ovarian cancer is the most lethal gynecological cancer and the high mortality is due to the frequent presentation at advanced stage, and to primary or acquired resistance to platinum-based therapy.

Methods:

We developed three new models of ovarian cancer patient-derived xenografts (ovarian PDXs) resistant to cisplatin (cDDP) after multiple in vivo drug treatments. By different and complementary approaches based on integrated metabolomics (both targeted and untargeted mass spectrometry-based techniques), gene expression, and functional assays (Seahorse technology) we analyzed and compared the tumor metabolic profile in each sensitive and their corresponding cDDP-resistant PDXs.

Results:

We found that cDDP-sensitive and -resistant PDXs have a different metabolic asset. In particular, we found, through metabolomic and gene expression approaches, that glycolysis, tricarboxylic acid cycle and urea cycle pathways were deregulated in resistant versus sensitive PDXs. In addition, we observed that oxygen consumption rate and mitochondrial respiration were higher in resistant PDXs than in sensitive PDXs under acute stress conditions. An increased oxidative phosphorylation in cDDP-resistant sublines led us to hypothesize that its interference could be of therapeutic value. Indeed, in vivo treatment of metformin and cDDP was able to partially reverse platinum resistance.

Conclusions:

Our data strongly reinforce the idea that the development of acquired cDDP resistance in ovarian cancer can bring about a rewiring of tumor metabolism, and that this might be exploited therapeutically.

Galectin-3 regulates chemotherapy sensitivity in epithelial ovarian carcinoma via regulating mitochondrial function

Galectin-3 (Gal-3) is a multifunctional carbohydrate-binding protein associated with cell migration, cell proliferation, cell adhesion, and cell-cell interaction in tumor cells. It has been implied to be involved in the tumor progression and chemoresistance of epithelial ovarian cancer (EOC). However, it is unclear whether the Gal-3-mediated regulation on the EOC chemosensitivity is associated with hypoxia or mitochondrial dysfunction. In the present study, we examined the regulation by Gal-3 overexpression on cisplatin-sensitivity or cisplatin-resistance in EOC cells in vitro. We manipulated Gal-3 via plasmid transfection and RNA interference in the cisplatin-resistant EOC cells, and re-evaluated the sensitivity of the cisplatin-resistant EOC cells to cisplatin, with CCK-8 assay, colony forming assay, apoptosis analysis and mitochondrial function examination. Results demonstrated that galectin-3 overexpression downregulated the cisplatin sensitivity in EOC OVCAR-3 cell clone, resulting in an upregulated growth and a reduced apoptosis in the cisplatin-treated OVCAR-3 cells. On the other hand, the Gal-3 knockdown with Gal-3-specific siRNA transfection aggravated cisplatin-induced apoptosis in OVCAR-3 cells. In conclusion, Galectin-3 reduces the sensitivity of ovarian cancer cells to cisplatin via regulating cisplatin-induced mitochondrial dysfunction. Galectin-3 knockdown inhibits the chemo-resistance of EOC cells. It implies that Galectin-3 might be a potential target to overcome the chemo-resistance in EOC cells.

Sab concentrations indicate chemotherapeutic susceptibility in ovarian cancer cell lines

The occurrence of chemotherapy-resistant tumors makes ovarian cancer (OC) the most lethal gynecological malignancy. While many factors may contribute to chemoresistance, the mechanisms responsible for regulating tumor vulnerability are under investigation. Our analysis of gene expression data revealed that Sab, a mitochondrial outer membrane (MOM) scaffold protein, was down-regulated in OC patients. Sab-mediated signaling induces cell death, suggesting that this apoptotic pathway is diminished in OC. We examined Sab expression in a panel of OC cell lines and found that the magnitude of Sab expression correlated to chemo-responsiveness; wherein, OC cells with low Sab levels were chemoresistant. The Sab levels were reflected by a corresponding amount of stress-induced c-Jun N-terminal kinase (JNK) on the MOM. BH3 profiling and examination of Bcl-2 and BH3-only protein concentrations revealed that cells with high Sab concentrations were primed for apoptosis, as determined by the decrease in pro-survival Bcl-2 proteins and an increase in pro-apoptotic BH3-only proteins on mitochondria. Furthermore, overexpression of Sab in chemoresistant cells enhanced apoptotic priming and restored cellular vulnerability to a combination treatment of cisplatin and paclitaxel. Contrariwise, inhibiting Sab-mediated signaling or silencing Sab expression in a chemosensitive cell line resulted in decreased apoptotic priming and increased resistance. The effects of silencing on Sab on the resistance to chemotherapeutic agents were emulated by the silencing or inhibition of JNK, which could be attributed to changes in Bcl-2 protein concentrations induced by sub-chronic JNK inhibition. We propose that Sab may be a prognostic biomarker to discern personalized treatments for OC patients.

Mass spectrometry-based proteomics techniques and their application in ovarian cancer research

Ovarian cancer has emerged as one of the leading cause of gynecological malignancies. So far, the measurement of CA125 and HE4 concentrations in blood and transvaginal ultrasound examination are essential ovarian cancer diagnostic methods. However, their sensitivity and specificity are still not sufficient to detect disease at the early stage. Moreover, applied treatment may appear to be ineffective due to drug-resistance. Because of a high mortality rate of ovarian cancer, there is a pressing need to develop innovative strategies leading to a full understanding of complicated molecular pathways related to cancerogenesis. Recent studies have shown the great potential of clinical proteomics in the characterization of many diseases, including ovarian cancer. Therefore, in this review, we summarized achievements of proteomics in ovarian cancer management. Since the development of mass spectrometry has caused a breakthrough in systems biology, we decided to focus on studies based on this technique. According to PubMed engine, in the years 2008-2010 the number of studies concerning OC proteomics was increasing, and since 2010 it has reached a plateau. Proteomics as a rapidly evolving branch of science may be essential in novel biomarkers discovery, therapy decisions, progression predication, monitoring of drug response or resistance. Despite the fact that proteomics has many to offer, we also discussed some limitations occur in ovarian cancer studies. Main difficulties concern both complexity and heterogeneity of ovarian cancer and drawbacks of the mass spectrometry strategies. This review summarizes challenges, capabilities, and promises of the mass spectrometry-based proteomics techniques in ovarian cancer management.

Repression of GRIM19 expression potentiates cisplatin chemoresistance in advanced bladder cancer cells via disrupting ubiquitination-mediated Bcl-xL degradation

OBJECTIVE

The mainstay of treatment for advanced bladder cancer (BC) is cisplatin (CDDP)-based systematic chemotherapy. However, acquired chemoresistance induced by as yet unidentified mechanisms is encountered frequently and often results in treatment failure and disease progression. The present study was designed to elucidate the expression and potential role of the gene associated with retinoid-interferon-induced mortality-19 (GRIM19) in the pathogenesis of CDDP resistance in BC.

METHODS

RT-qPCR and immunoblotting were employed to evaluate the expression profile of GRIM19 in clinical BC samples and in different BC cells. Using cell viability assay, apoptotic ELISA, xenografts mouse model, and Transwell assay, the effects of GRIM19 inhibition or GRIM19 overexpression on CDDP resistance were determined in different BC cells. Lastly, using co-immunoprecipitation, we provided the molecular evidence for the interaction between GRIM19 and Bcl-xL.

RESULTS

Expression levels of GRIM19 were significantly down-regulated in recurrent BC specimens, and in experimentally induced CDDP-resistant BC cells. Functionally, overexpression of the exogenous GRIM19 potentiated CDDP sensitivity and suppressed the survival and invasion of BC cells in the presence of CDDP challenge. Mechanistically, the compromised CDDP chemosensitization induced by GRIM19 loss was at least partially attributed to the attenuation of Bcl-xL polyubiquitination and subsequent degradation, because (1) GRIM19 colocalized with Bcl-xL in the mitochondria of BC cells and (2) GRIM19 overexpression promoted the ubiquitination of Bcl-xL, and this event could be effectively reversed by pretreatment with inhibitors of p38-MAPK and JNK pathways, indicating that GRIM19 overexpression-induced Bcl-xL ubiquitination may achieve in a p38/JNK-dependent manner. Using the UMUC-3 cells stably depleted of endogenous GRIM19, we further show that inhibition of Bcl-xL rectified GRIM19 deficiency-caused CDDP resistance in BC cells. In addition, BCL2L1 mRNA levels were negatively correlated with GRIM19 mRNA levels in CDDP-associated clinical BC tissues.

CONCLUSIONS

Disruption of GRIM19/Bcl-xL is a key mechanism of CDDP resistance in advanced BC. Therapeutically, enhancement of GRIM19 expression or employment of p38/JNK inhibitors may serve as resensitizing therapies for subgroups of CDDP-resistant or refractory BC patients.

Mass spectrometry-assisted gel-based proteomics in cancer biomarker discovery: approaches and application

There is a critical need for the discovery of novel biomarkers for early detection and targeted therapy of cancer, a major cause of deaths worldwide. In this respect, proteomic technologies, such as mass spectrometry (MS), enable the identification of pathologically significant proteins in various types of samples. MS is capable of high-throughput profiling of complex biological samples including blood, tissues, urine, milk, and cells. MS-assisted proteomics has contributed to the development of cancer biomarkers that may form the foundation for new clinical tests. It can also aid in elucidating the molecular mechanisms underlying cancer. In this review, we discuss MS principles and instrumentation as well as approaches in MS-based proteomics, which have been employed in the development of potential biomarkers. Furthermore, the challenges in validation of MS biomarkers for their use in clinical practice are also reviewed.

Hyper-phosphorylation of Sequestosome-1 Distinguishes Resistance to Cisplatin in Patient Derived High Grade Serous Ovarian Cancer Cells

Platinum-resistance is a major limitation to effective chemotherapy regimens in high-grade serous ovarian cancer (HGSOC). To better understand the mechanisms involved we characterized the proteome and phosphoproteome in cisplatin sensitive and resistant HGSOC primary cells using a mass spectrometry-based proteomic strategy. PCA analysis identified a distinctive phosphoproteomic signature between cisplatin sensitive and resistant cell lines. The most phosphorylated protein in cisplatin resistant cells was sequestosome-1 (p62/SQSTM1). Changes in expression of apoptosis and autophagy related proteins Caspase-3 and SQSTM1, respectively, were validated by Western blot analysis. A significant increase in apoptosis in the presence of cisplatin was observed in only the sensitive cell line while SQSTM1 revealed increased expression in the resistant cell line relative to sensitive cell line. Furthermore, site-specific phosphorylation on 20 amino acid residues of SQSTM1 was detected indicating a hyper-phosphorylation phenotype. This elevated hyper-phosphorylation of SQSTM1 in resistant HGSOC cell lines was validated with Western blot analysis. Immunofluoresence staining of s28-pSQSTM1 showed inducible localization to autophagosomes upon cisplatin treatment in the sensitive cell line while being constitutively expressed to autophagosomes in the resistant cell. Furthermore, SQSTM1 expression was localized in cancer cells of clinical high-grade serous tumors. Here, we propose hyper-phosphorylation of SQSTM1 as a marker and a key proteomic change in cisplatin resistance development in ovarian cancers by activating the autophagy pathway and influencing down-regulation of apoptosis.

Establishment and characterization of a platinum- and paclitaxel-resistant high grade serous ovarian carcinoma cell line

High grade serous ovarian cancer (HGSOC) patients have a high recurrence rate after surgery and adjuvant chemotherapy due to inherent or acquired drug resistance. Cell lines derived from HGSOC tumors that are resistant to chemotherapeutic agents represent useful pre-clinical models for drug discovery. Here, we describe establishment of a human ovarian carcinoma cell line, which we term WHIRC01, from a patient-derived mouse xenograft established from a chemorefractory HGSOC patient who did not respond to carboplatin and paclitaxel therapy. This newly derived cell line is platinum- and paclitaxel-resistant with cisplatin, carboplatin, and paclitaxel half-maximal lethal doses of 15, 130, and 20 µM, respectively. Molecular characterization of this cell line was performed using targeted DNA exome sequencing, transcriptomics (RNA-seq), and mass spectrometry-based proteomic analyses. Results from exomic sequencing revealed mutations in TP53 consistent with HGSOC. Transcriptomic and proteomic analyses of WHIRC01 showed high level of alpha-enolase and vimentin, which are associated with cell migration and epithelial-mesenchymal transition. WHIRC01 represents a chemorefractory human HGSOC cell line model with a comprehensive molecular profile to aid future investigations of drug resistance mechanisms and screening of chemotherapeutic agents.

TWIST1 drives cisplatin resistance and cell survival in an ovarian cancer model, via upregulation of GAS6, L1CAM, and Akt signalling

Epithelial ovarian cancer (EOC) is the most deadly gynaecologic malignancy due to late onset of symptoms and propensity towards drug resistance. Epithelial-mesenchymal transition (EMT) has been linked to the development of chemoresistance in other cancers, yet little is known regarding its role in EOC. In this study, we sought to determine the role of the transcription factor TWIST1, a master regulator of EMT, on cisplatin resistance in an EOC model. We created two Ovcar8-derived cell lines that differed only in their TWIST1 expression. TWIST1 expression led to increased tumour engraftment in mice, as well as cisplatin resistance in vitro. RNA sequencing analysis revealed that TWIST1 expression resulted in upregulation of GAS6 and L1CAM and downregulation of HMGA2. Knockdown studies of these genes demonstrated that loss of GAS6 or L1CAM sensitized cells to cisplatin, but that loss of HMGA2 did not give rise to chemoresistance. TWIST1, in part via GAS6 and L1CAM, led to higher expression and activation of Akt upon cisplatin treatment, and inhibition of Akt activation sensitized cells to cisplatin. These results suggest TWIST1- and EMT-driven increase in Akt activation, and thus tumour cell proliferation, as a potential mechanism of drug resistance in EOC.

Proteomics of ovarian cancer: functional insights and clinical applications

In the past decade, there has been an increasing interest in applying proteomics to assist in understanding the pathogenesis of ovarian cancer, elucidating the mechanism of drug resistance, and in the development of biomarkers for early detection of ovarian cancer. Although ovarian cancer is a spectrum of different diseases, the strategies for diagnosis and treatment with surgery and adjuvant therapy are similar across ovarian cancer types, increasing the general applicability of discoveries made through proteomics research. While proteomic experiments face many difficulties which slow the pace of clinical applications, recent advances in proteomic technology contribute significantly to the identification of aberrant proteins and networks which can serve as targets for biomarker development and individualized therapies. This review provides a summary of the literature on proteomics' contributions to ovarian cancer research and highlights the current issues, future directions, and challenges. We propose that protein-level characterization of primary lesion in ovarian cancer can decipher the mystery of this disease, improve diagnostic tools, and lead to more effective screening programs.

Nilotinib reduced the viability of human ovarian cancer cells via mitochondria-dependent apoptosis, independent of JNK activation

Nilotinib (AMN) induces apoptosis in various cancer cells; however the effect of AMN on human ovarian cancer cells is still unclear. A reduction in cell viability associated with the occurrence of apoptotic characteristics was observed in human SKOV-3 ovarian cancer cells under AMN but not sorafenib (SORA) or imatinib (STI) stimulation. Activation of apoptotic pathway including increased caspase (Casp)-3 and poly(ADP-ribose) polymerase 1 (PARP1) protein cleavage by AMN was detected with disrupted mitochondrial membrane potential (MMP) accompanied by decreased Bcl-2 protein and increased cytosolic cytochrome (Cyt) c/cleaved Casp-9 protein expressions was found, and AMN-induced cell death was inhibited by peptidyl Casp inhibitors, VAD, DEVD and LEHD. Increased phosphorylated c-Jun N-terminal kinase (JNK) protein expression was detected in AMN- but not SORA- or STI-treated SKOV-3 cells, and the JNK inhibitors, SP600125 and JNKI, showed slight but significant enhancement of AMN-induced cell death in SKOV-3 cells. The intracellular peroxide level was elevated by AMN and H2O2, and N-acetylcysteine (NAC) prevented H2O2- but not AMN-induced peroxide production and apoptosis in SKOV-3 cells. AMN induction of apoptosis with increased intracellular peroxide production and JNK protein phosphorylation was also identified in human A2780 ovarian cancer cells, cisplatin-resistant A2780CP cells, and clear ES-2 cells. The evidence supporting AMN effectively reducing the viability of human ovarian cancer cells via mitochondrion-dependent apoptosis is provided.

Nestin regulates proliferation and invasion of gastrointestinal stromal tumor cells by altering mitochondrial dynamics

Nestin is widely expressed in numerous tumors and has become a diagnostic and prognostic indicator. However, the exact mechanism by which nestin contributes to tumor malignancy remains poorly understood. Here, we found marked upregulation of nestin expression in highly proliferative and invasive gastrointestinal stromal tumor (GIST) specimens. Nestin knockdown in GIST cells reduced the proliferative and invasive activity owing to a decrease of mitochondrial intracellular reactive oxygen species (ROS) generation. Furthermore, nestin was co-localized with mitochondria, and knockdown of nestin increased mitochondrial elongation and influenced the mitochondrial function, including oxygen consumption rates, ATP generation and mitochondrial membrane potential and so on. In exploring the underlying mechanism, we demonstrated nestin knockdown inhibited the mitochondrial recruitment of Dynamin-related protein1 and induced the change of mitochondrial dynamics. Thus, nestin may have an important role in GIST malignancy by regulating mitochondrial dynamics and altering intracellular ROS levels. The findings provide new clues to reveal mechanisms by which nestin mediates the proliferation and invasion of GISTs.

Elevated AKAP12 in paclitaxel-resistant serous ovarian cancer cells is prognostic and predictive of poor survival in patients

A majority of high-grade (HG) serous ovarian cancer (SOC) patients develop resistant disease despite high initial response rates to platinum/paclitaxel-based chemotherapy. We identified shed/secreted proteins in preclinical models of paclitaxel-resistant human HGSOC models and correlated these candidate proteins with patient outcomes using public data from HGSOC patients. Proteomic analyses of a HGSOC cell line secretome was compared to those from a syngeneic paclitaxel-resistant variant and from a line established from an intrinsically chemorefractory HGSOC patient. Associations between the identified candidate proteins and patient outcome were assessed in a discovery cohort of 545 patients and two validation cohorts totaling 795 independent SOC patients. Among the 81 differentially abundant proteins identified (q < 0.05) from paclitaxel-sensitive vs -resistant HGSOC cell secretomes, AKAP12 was verified to be elevated in all models of paclitaxel-resistant HGSOC. Furthermore, elevated AKAP12 transcript expression was associated with worse progression-free and overall survival. Associations with outcome were observed in three independent cohorts and remained significant after adjusted multivariate modeling. We further provide evidence to support that differential gene methylation status is associated with elevated expression of AKAP12 in taxol-resistant ovarian cancer cells and ovarian cancer patient subsets. Elevated expression and shedding/secretion of AKAP12 is characteristic of paclitaxel-resistant HGSOC cells, and elevated AKAP12 transcript expression is a poor prognostic and predictive marker for progression-free and overall survival in SOC patients.

Metallomic and metalloproteomic strategies in elucidating the molecular mechanisms of metallodrugs

Advances in the mechanistic studies of metallodrugs by metallomic and metalloproteomic approaches will improve our understanding of the mechanism of action and allow more metallodrugs to be developed.

Down-regulation of Ras-related protein Rab 5C-dependent endocytosis and glycolysis in cisplatin-resistant ovarian cancer cell lines

Drug resistance poses a major challenge to ovarian cancer treatment. Understanding mechanisms of drug resistance is important for finding new therapeutic targets. In the present work, a cisplatin-resistant ovarian cancer cell line A2780-DR was established with a resistance index of 6.64. The cellular accumulation of cisplatin was significantly reduced in A2780-DR cells as compared with A2780 cells consistent with the general character of drug resistance. Quantitative proteomic analysis identified 340 differentially expressed proteins between A2780 and A2780-DR cells, which involve in diverse cellular processes, including metabolic process, cellular component biogenesis, cellular processes, and stress responses. Expression levels of Ras-related proteins Rab 5C and Rab 11B in A2780-DR cells were lower than those in A2780 cells as confirmed by real-time quantitative PCR and Western blotting. The short hairpin (sh)RNA-mediated knockdown of Rab 5C in A2780 cells resulted in markedly increased resistance to cisplatin whereas overexpression of Rab 5C in A2780-DR cells increases sensitivity to cisplatin, demonstrating that Rab 5C-dependent endocytosis plays an important role in cisplatin resistance. Our results also showed that expressions of glycolytic enzymes pyruvate kinase, glucose-6-phosphate isomerase, fructose-bisphosphate aldolase, lactate dehydrogenase, and phosphoglycerate kinase 1 were down-regulated in drug resistant cells, indicating drug resistance in ovarian cancer is directly associated with a decrease in glycolysis. Furthermore, it was found that glutathione reductase were up-regulated in A2780-DR, whereas vimentin, HSP90, and Annexin A1 and A2 were down-regulated. Taken together, our results suggest that drug resistance in ovarian cancer cell line A2780 is caused by multifactorial traits, including the down-regulation of Rab 5C-dependent endocytosis of cisplatin, glycolytic enzymes, and vimentin, and up-regulation of antioxidant proteins, suggesting Rab 5C is a potential target for treatment of drug-resistant ovarian cancer. This constitutes a further step toward a comprehensive understanding of drug resistance in ovarian cancer.

MitProNet: A knowledgebase and analysis platform of proteome, interactome and diseases for mammalian mitochondria

Mitochondrion plays a central role in diverse biological processes in most eukaryotes, and its dysfunctions are critically involved in a large number of diseases and the aging process. A systematic identification of mitochondrial proteomes and characterization of functional linkages among mitochondrial proteins are fundamental in understanding the mechanisms underlying biological functions and human diseases associated with mitochondria. Here we present a database MitProNet which provides a comprehensive knowledgebase for mitochondrial proteome, interactome and human diseases. First an inventory of mammalian mitochondrial proteins was compiled by widely collecting proteomic datasets, and the proteins were classified by machine learning to achieve a high-confidence list of mitochondrial proteins. The current version of MitProNet covers 1124 high-confidence proteins, and the remainders were further classified as middle- or low-confidence. An organelle-specific network of functional linkages among mitochondrial proteins was then generated by integrating genomic features encoded by a wide range of datasets including genomic context, gene expression profiles, protein-protein interactions, functional similarity and metabolic pathways. The functional-linkage network should be a valuable resource for the study of biological functions of mitochondrial proteins and human mitochondrial diseases. Furthermore, we utilized the network to predict candidate genes for mitochondrial diseases using prioritization algorithms. All proteins, functional linkages and disease candidate genes in MitProNet were annotated according to the information collected from their original sources including GO, GEO, OMIM, KEGG, MIPS, HPRD and so on. MitProNet features a user-friendly graphic visualization interface to present functional analysis of linkage networks. As an up-to-date database and analysis platform, MitProNet should be particularly helpful in comprehensive studies of complicated biological mechanisms underlying mitochondrial functions and human mitochondrial diseases. MitProNet is freely accessible at http://bio.scu.edu.cn:8085/MitProNet.

Cancer stem cells and cisplatin-resistant cells isolated from non-small-lung cancer cell lines constitute related cell populations

Lung cancer is the top cause of cancer-related deceases. One of the reasons is the development of resistance to the chemotherapy treatment. In particular, cancer stem cells (CSCs), can escape treatment and regenerate the bulk of the tumor. In this article, we describe a comparison between cancer cells resistant to cisplatin and CSCs, both derived from the non-small-cell lung cancer cell lines H460 and A549. Cisplatin-resistant cells were obtained after a single treatment with the drug. CSCs were isolated by culture in defined media, under nonadherent conditions. The isolated CSCs were clonogenic, could be differentiated into adherent cells and were less sensitive to cisplatin than the original cells. Cisplatin resistant and CSCs were able to generate primary tumors and to metastasize when injected into immunodeficient Nu/Nu mice, although they formed smaller tumors with a larger latency than untreated cells. Notably, under appropriated proportions, CSCs synergized with differentiated cells to form larger tumors. CSCs also showed increased capacity to induce angiogenesis in Nu/Nu mice. Conversely, H460 cisplatin-resistant cells showed increased tendency to develop bone metastasis. Gene expression analysis showed that several genes involved in tumor development and metastasis (EGR1, COX2, MALAT1, AKAP12, ADM) were similarly induced in CSC and cisplatin-resistant H460 cells, in agreement with a close similarity between these two cell populations. Cells with the characteristic growth properties of CSCs were also isolated from surgical samples of 18 out of 44 lung cancer patients. A significant correlation (P = 0.028) was found between the absence of CSCs and cisplatin sensitivity.

Systems biology of cisplatin resistance: past, present and future

The platinum derivative cis-diamminedichloroplatinum(II), best known as cisplatin, is currently employed for the clinical management of patients affected by testicular, ovarian, head and neck, colorectal, bladder and lung cancers. For a long time, the antineoplastic effects of cisplatin have been fully ascribed to its ability to generate unrepairable DNA lesions, hence inducing either a permanent proliferative arrest known as cellular senescence or the mitochondrial pathway of apoptosis. Accumulating evidence now suggests that the cytostatic and cytotoxic activity of cisplatin involves both a nuclear and a cytoplasmic component. Despite the unresolved issues regarding its mechanism of action, the administration of cisplatin is generally associated with high rates of clinical responses. However, in the vast majority of cases, malignant cells exposed to cisplatin activate a multipronged adaptive response that renders them less susceptible to the antiproliferative and cytotoxic effects of the drug, and eventually resume proliferation. Thus, a large fraction of cisplatin-treated patients is destined to experience therapeutic failure and tumor recurrence. Throughout the last four decades great efforts have been devoted to the characterization of the molecular mechanisms whereby neoplastic cells progressively lose their sensitivity to cisplatin. The advent of high-content and high-throughput screening technologies has accelerated the discovery of cell-intrinsic and cell-extrinsic pathways that may be targeted to prevent or reverse cisplatin resistance in cancer patients. Still, the multifactorial and redundant nature of this phenomenon poses a significant barrier against the identification of effective chemosensitization strategies. Here, we discuss recent systems biology studies aimed at deconvoluting the complex circuitries that underpin cisplatin resistance, and how their findings might drive the development of rational approaches to tackle this clinically relevant problem.

Proteomics methods for subcellular proteome analysis

The elucidation of the subcellular distribution of proteins under different conditions is a major challenge in cell biology. This challenge is further complicated by the multicompartmental and dynamic nature of protein localization. To address this issue, quantitative proteomics workflows have been developed to reliably identify the protein complement of whole organelles, as well as for protein assignment to subcellular location and relative protein quantification based on different cell culture conditions. Here, we review quantitative MS-based approaches that combine cellular fractionation with proteomic analysis. The application of these methods to the characterization of organellar composition and to the determination of the dynamic nature of protein complexes is improving our understanding of protein functions and dynamics.

Mitochondria proteome profiling: a comparative analysis between gel- and gel-free approaches

Mitochondrial proteomics emerged aiming to disclose the dynamics of mitochondria under various pathophysiological conditions. In the present study we investigated the relative merits of gel-based (2DE and SDS-LC) and gel-free (2D-LC) protein separation approaches and protein identification algorithms (Mascot and Paragon) in the proteome profiling of mitochondria isolated from cultured fibroblasts, a sample traditionally used for diagnosis purposes. Combining data retrieved from 2DE, 2D-LC and SDS-LC and search methods, a total of 696 non-redundant proteins were identified. An overlap of only 19% between the proteins identified by the three different methods was observed when Mascot and Paragon were used. Regarding protein ID, a consistency in the number of identified proteins per sample was noticed for 2DE approach. Independent of the methodological approach chosen, it was noticed that the predominance in mitochondria of hydrophilic proteins with 20-50 kDa and pI 5-6 and 8-9; however, 2D-LC and SDS-LC allowed the enrichment of proteins with a mass below 30 kDa and of basic proteins with pI values above 8. In conclusion, data from the present study highlight the power of integrating different separation technologies and protein identification algorithms.

Mass spectrometry-based proteomics in molecular diagnostics: discovery of cancer biomarkers using tissue culture

Accurate diagnosis and proper monitoring of cancer patients remain a key obstacle for successful cancer treatment and prevention. Therein comes the need for biomarker discovery, which is crucial to the current oncological and other clinical practices having the potential to impact the diagnosis and prognosis. In fact, most of the biomarkers have been discovered utilizing the proteomics-based approaches. Although high-throughput mass spectrometry-based proteomic approaches like SILAC, 2D-DIGE, and iTRAQ are filling up the pitfalls of the conventional techniques, still serum proteomics importunately poses hurdle in overcoming a wide range of protein concentrations, and also the availability of patient tissue samples is a limitation for the biomarker discovery. Thus, researchers have looked for alternatives, and profiling of candidate biomarkers through tissue culture of tumor cell lines comes up as a promising option. It is a rich source of tumor cell-derived proteins, thereby, representing a wide array of potential biomarkers. Interestingly, most of the clinical biomarkers in use today (CA 125, CA 15.3, CA 19.9, and PSA) were discovered through tissue culture-based system and tissue extracts. This paper tries to emphasize the tissue culture-based discovery of candidate biomarkers through various mass spectrometry-based proteomic approaches.

Overcoming chemotherapy resistance of ovarian cancer cells by liposomal cisplatin: molecular mechanisms unveiled by gene expression profiling

Previously we reported that liposomal cisplatin (CDDP) overcomes CDDP resistance of ovarian A2780cis cancer cells (Krieger et al., Int. J. Pharm. 389, 2010, 10-17). Here we find that the cytotoxic activity of liposomal CDDP is not associated with detectable DNA platination in resistant ovarian cancer cells. This suggests that the mode of action of liposomal CDDP is different from the free drug. To gain insight into mechanisms of liposomal CDDP activity, we performed a transcriptome analysis of untreated A2780cis cells, and A2780cis cells in response to exposure with IC50 values of free or liposomal CDDP. A process network analysis of upregulated genes showed that liposomal CDDP induced a highly different gene expression profile in comparison to the free drug. p53 was identified as a key player directing transcriptional responses to free or liposomal CDDP. The free drug induced expression of essential genes of the intrinsic (mitochondrial) apoptosis pathway (BAX, BID, CASP9) most likely through p38MAPK activation. In contrast, liposomal CDDP induced expression of genes from DNA damage pathways and several genes of the extrinsic pathway of apoptosis (TNFRSF10B-DR5, CD70-TNFSF7). It thus appears that liposomal CDDP overcomes CDDP resistance by inducing DNA damage and in consequence programmed cell death by the extrinsic pathway. Predictions from gene expression data with respect to apoptosis activation were confirmed at the protein level by an apoptosis antibody array. This sheds new light on liposomal drug carrier approaches in cancer and suggests liposomal CDDP as promising strategy for the treatment of CDDP resistant ovarian carcinomas.

The Interaction of Adrenomedullin and Macrophages Induces Ovarian Cancer Cell Migration via Activation of RhoA Signaling Pathway

Tumor-associated macrophages (TAMs) are correlated with poor prognosis in many human cancers; however, the mechanism by which TAMs facilitate ovarian cancer cell migration and invasion remains unknown. This study was aimed to examine the function of adrenomedullin (ADM) in macrophage polarization and their further effects on the migration of ovarian cancer cells. Exogenous ADM antagonist and small interfering RNA (siRNA) specific for ADM expression were treated to macrophages and EOC cell line HO8910, respectively. Then macrophages were cocultured with HO8910 cells without direct contact. Flow cytometry, Western blot and real-time PCR were used to detect macrophage phenotype and cytokine production. The migration ability and cytoskeleton rearrangement of ovarian cancer cells were determined by Transwell migration assay and phalloidin staining. Western blot was performed to evaluate the activity status of signaling molecules in the process of ovarian cancer cell migration. The results showed that ADM induced macrophage phenotype and cytokine production similar to TAMs. Macrophages polarized by ADM promoted the migration and cytoskeleton rearrangement of HO8910 cells. The expression of RhoA and its downstream effector, cofilin, were upregulated in macrophage-induced migration of HO8910 cells. In conclusion, ADM could polarize macrophages similar to TAMs, and then polarized macrophages promote the migration of ovarian cancer cells via activation of RhoA signaling pathway in vitro.