Drug-resistant Ovarian Cancer Cells Research Articles

Impact of Obesity and Lysosomal Dysfunction on Chemoresistance in Ovarian Cancer.

Obesity is recognized as a significant risk factor for ovarian cancer, with accumulating evidence highlighting its impact on disease progression and chemoresistance. This review synthesizes current research elucidating the link between obesity-induced lysosomal dysfunction and ovarian cancer chemoresistance. Epidemiological studies consistently demonstrate a positive correlation between body mass index (BMI) and ovarian cancer risk, attributed in part to the predilection of epithelial ovarian cancer cells for adipose tissue, particularly the omentum. Adipokines released from the omentum contribute to cancer-associated characteristics, including energy supply to cancer cells. Moreover, obesity-induced alterations in lysosomal function have been implicated in systemic inflammation and lipid metabolism dysregulation, further exacerbating cancer progression. Lysosomes play a crucial role in drug resistance, as evidenced by studies demonstrating their involvement in mediating resistance to chemotherapy in ovarian cancer cells. Recent findings suggest that pharmacological inhibition of lysosomal calcium channels sensitizes drug-resistant ovarian cancer cells to cisplatin treatment, highlighting the therapeutic potential of targeting lysosomal dysfunction in obesity-related chemoresistance. This review underscores the importance of understanding the multifaceted roles of lysosomes in obesity-related drug resistance and their implications for the development of targeted therapeutic interventions in ovarian cancer management.

Magnoflorine inhibits cisplatin-induced protective autophagy by down-regulating HMGB1 and increases drug sensitivity in drug-resistant ovarian cancer cells

Magnoflorine inhibits cisplatin-induced protective autophagy by down-regulating HMGB1 and increases drug sensitivity in drug-resistant ovarian cancer cells

The TGFBI gene and protein expression in topotecan resistant ovarian cancer cell lines

PurposeThe primary limiting factor in achieving cures for patients with cancer, particularly ovarian cancer, is drug resistance. The mechanisms of drug resistance of cancer cells during chemotherapy may include compounds of the extracellular matrix, such as the transforming growth factor-beta-induced protein (TGFBI). In this study, we aimed to analyze the TGFBI gene and protein expression in different sensitive and drug-resistant ovarian cancer cell lines, as well as test if TGFBI can be involved in the response to topotecan (TOP) at the very early stages of treatment. Materials and methodsIn this study, we conducted a detailed analysis of TGFBI expression in different ovarian cancer cell lines (A2780, A2780TR1, A2780TR2, W1, W1TR, SKOV-3, PEA1, PEA2 and PEO23). The level of TGFBI mRNA (QPCR), intracellular and extracellular protein (Western blot analysis) were assessed in this study. ResultsWe observed upregulation of TGFBI mRNA in drug-resistant cell lines and estrogen-receptor positive cell lines, which was supported by overexpression of both intracellular and extracellular TGFBI protein. We also showed the TGFBI expression after a short period of treatment of sensitive ovarian cancer cell lines with TOP. ConclusionThe expression of TGFBI in ovarian cancer cell lines suggests its role in the development of drug resistance.

The mechanisms crosstalk and therapeutic opportunities between ferroptosis and ovary diseases.

Ferroptosis, a form of regulated cell death, was first defined in 2012. Ferroptosis mainly involves iron-driven lipid peroxidation damage of cells. This process is regulated by iron homeostasis, redox balance, lipid metabolism, glutathione metabolism, and various disease signaling pathways. Iron is one of the key mineral elements that regulate the physiological function of women and the development of ovarian tumors. Occurrence of Ferroptosis has some hidden dangers and advantages in ovary diseases. Some scholars have shown that ferroptosis of ovarian granulosa cells (GC) promotes the development of ovarian dysfunction and polycystic ovary syndrome (PCOS). Interestingly, drug-resistant ovarian cancer cells are very sensitive to ferroptosis, suggesting that pharmacological positive and negative regulation of ferroptosis has great potential in the treatment of benign ovarian diseases and ovarian cancer. This article aimed to assess how ferroptosis occurs and the factors controlling ferroptosis. Moreover, we summarize how ferroptosis can be used to predict, diagnose and target treatment ovary disease. Meanwhile, we also evaluated the different phenomena of Ferroptosis in ovarian diseases. It aims to provide new directions for the research and prevention of female reproductive diseases.

Tripterygium glycosides reverse chemotherapy resistance in ovarian cancer by targeting the NRF2/GPX4 signal axis to induce ferroptosis of drug-resistant human epithelial ovarian cancer cells

Cisplatin resistance is the main cause of postoperative recurrence and difficulty in the treatment of ovarian cancer. It is urgently needed to identify therapeutic drugs with unique functions to overcome the current challenges in the treatment of ovarian cancer. In this study, we found that TG promoted the accumulation of ROS and MDA in A2780/DDP cells and downregulated the expression of key antioxidant molecules. In vivo, the survival rate of tumor-bearing nude mice was prolonged by TG without significant hepatotoxic reaction. The expression of key antioxidant molecules in tumor tissues was consistent with that in vitro. These findings revealed that TG disrupted homeostasis of redox reactions and induced ferroptosis in A2780/DDP cells, thereby enhancing cisplatin chemosensitivity of ovarian cancer. Overall, TG may be a novel potential therapeutic option for reversing resistance to cisplatin chemotherapy.

Stem cell-assisted enzyme/prodrug therapy makes drug-resistant ovarian cancer cells vulnerable to natural killer cells through upregulation of NKG2D ligands.

Cancer stem-like cells (CSCs) are believed to be responsible for cancer recurrence and metastasis. Therefore, a therapeutic approach is needed to eliminate both rapidly proliferating differentiated cancer cells and slow-growing drug-resistant CSCs. Using established ovarian cancer cells lines as well as ovarian cancer cells isolated from a patient with high-grade drug-resistant ovarian carcinoma, we demonstrate that ovarian CSCs consistently express lower levels of NKG2D ligands (MICA/B and ULBPs) on their surfaces, a mechanism by which they evade natural killer (NK) cells' surveillance. Here, we discovered that exposure of ovarian cancer (OC) cells to SN-38 followed by 5-FU not only acts synergistically to kill the OC cells, but also makes the CSCs vulnerable to NK92 cells through upregulation of NKG2D ligands. Since systemic administration of these two drugs is marred by intolerance and instability, we engineered and isolated an adipose-derived stem cell (ASC) clone, which stably expresses carboxylesterase-2 and yeast cytosine deaminase enzymes to convert irinotecan and 5-FC prodrugs into SN-38 and 5-FU cytotoxic drugs, respectively. Co-incubation of ASCs and prodrugs with drug-resistant OC cells not only led to the death of the drug-resistant OC cells but also made them significantly vulnerable to NK92 cells. This study provides proof of principle for a combined ASC-directed targeted chemotherapy with NK92-assisted immunotherapy to eradicate drug-resistant OC cells.

Nanosecond-pulsed plasma jet in air and air/helium mixtures: Plasma properties and anticancer effect

Nanosecond-pulse power has the characteristics of quickly increasing applied power, short pulse width, and considerably high-energy electrons. In this study, we investigated the different air/helium mixture ratios of nanosecond-pulsed-power-driven plasma jet discharge characteristics and the physicochemical properties of the gaseous and aqueous phases. Results showed that the length and luminescence intensity of the plasma increased with decreasing air ratio. Notably, there is a maximum inflection point in N2O5 of Fourier transform infrared spectrometry detection and concentration of H2O2 at 70% air ratio. Furthermore, we used drug-resistant ovarian cancer cells (A2780/ADR) as a model to detect the anticancer effect, with the results indicating that 70% air ratio is the best condition to inhibit cell growth and induce cell apoptosis. Our research indicates that the air discharge driven by a nanosecond-pulse power supply has potential application in an ovarian cancer drug-resistant tumor cell therapy.

Regulation of mitochondrial complex III activity and assembly by TRAP1 in cancer cells

BackgroundMetabolic reprogramming is an important issue in tumor biology. A recently-identified actor in this regard is the molecular chaperone TRAP1, that is considered an oncogene in several cancers for its high expression but an oncosuppressor in others with predominant oxidative metabolism. TRAP1 is mainly localized in mitochondria, where it interacts with respiratory complexes, although alternative localizations have been described, particularly on the endoplasmic reticulum, where it interacts with the translational machinery with relevant roles in protein synthesis regulation.ResultsHerein we show that, inside mitochondria, TRAP1 binds the complex III core component UQCRC2 and regulates complex III activity. This decreases respiration rate during basal conditions but allows sustained oxidative phosphorylation when glucose is limiting, a condition in which the direct TRAP1-UQCRC2 binding is disrupted, but not TRAP1-complex III binding. Interestingly, several complex III components and assembly factors show an inverse correlation with survival and response to platinum-based therapy in high grade serous ovarian cancers, where TRAP1 inversely correlates with stage and grade and directly correlates with survival. Accordingly, drug-resistant ovarian cancer cells show high levels of complex III components and high sensitivity to complex III inhibitory drug antimycin A.ConclusionsThese results shed new light on the molecular mechanisms involved in TRAP1-dependent regulation of cancer cell metabolism and point out a potential novel target for metabolic therapy in ovarian cancer.

Complementary anti-cancer pathways triggered by inhibition of sideroflexin 4 in ovarian cancer

DNA damaging agents are a mainstay of standard chemotherapy for ovarian cancer. Unfortunately, resistance to such DNA damaging agents frequently develops, often due to increased activity of DNA repair pathways. Sideroflexin 4 (SFXN4) is a little-studied inner mitochondrial membrane protein. Here we demonstrate that SFXN4 plays a role in synthesis of iron sulfur clusters (Fe-S) in ovarian cancer cells and ovarian cancer tumor-initiating cells, and that knockdown of SFXN4 inhibits Fe-S biogenesis in ovarian cancer cells. We demonstrate that this has two important consequences that may be useful in anti-cancer therapy. First, inhibition of Fe-S biogenesis triggers the accumulation of excess iron, leading to oxidative stress. Second, because enzymes critical to multiple DNA repair pathways require Fe-S clusters for their function, DNA repair enzymes and DNA repair itself are inhibited by reduction of SFXN4. Through this dual mechanism, SFXN4 inhibition heightens ovarian cancer cell sensitivity to DNA-damaging drugs and DNA repair inhibitors used in ovarian cancer therapy, such as cisplatin and PARP inhibitors. Sensitization is achieved even in drug resistant ovarian cancer cells. Further, knockout of SFXN4 decreases DNA repair and profoundly inhibits tumor growth in a mouse model of ovarian cancer metastasis. Collectively, these results suggest that SFXN4 may represent a new target in ovarian cancer therapy.

Terfenadine resensitizes doxorubicin activity in drug-resistant ovarian cancer cells via an inhibition of CaMKII/CREB1 mediated ABCB1 expression.

Ovarian cancer is one of the most lethal gynecological malignancies. Recurrence or acquired chemoresistance is the leading cause of ovarian cancer therapy failure. Overexpression of ATP-binding cassette subfamily B member 1 (ABCB1), commonly known as P-glycoprotein, correlates closely with multidrug resistance (MDR). However, the mechanism underlying aberrant ABCB1 expression remains unknown. Using a quantitative high-throughput combinational screen, we identified that terfenadine restored doxorubicin sensitivity in an MDR ovarian cancer cell line. In addition, RNA-seq data revealed that the Ca2+-mediated signaling pathway in the MDR cells was abnormally regulated. Moreover, our research demonstrated that terfenadine directly bound to CAMKIID to prevent its autophosphorylation and inhibit the activation of the cAMP-responsive element-binding protein 1 (CREB1)-mediated pathway. Direct inhibition of CAMKII or CREB1 had the same phenotypic effects as terfenadine in the combined treatment, including lower expression of ABCB1 and baculoviral IAP repeat-containing 5 (BIRC5, also known as survivin) and increased doxorubicin-induced apoptosis. In this study, we demonstrate that aberrant regulation of the Ca2+-mediated CAMKIID/CREB1 pathway contributes to ABCB1 over-expression and MDR creation and that CAMKIID and CREB1 are attractive targets for restoring doxorubicin efficacy in ABCB1-mediated MDR ovarian cancer.

A targetable MYBL2-ATAD2 axis governs cell proliferation in ovarian cancer.

The chromatin-modifying enzyme ATAD2 confers oncogenic competence and proliferative advantage in malignances. We previously identified ATAD2 as a marker and driver of cell proliferation in ovarian cancer (OC); however, the mechanisms whereby ATAD2 is regulated and involved in cell proliferation are still unclear. Here, we disclose that ATAD2 displays a classical G2/M gene signature, functioning to facilitate mitotic progression. ATAD2 ablation caused mitotic arrest and decreased the ability of OC cells to pass through nocodazole-arrested mitosis. ChIP-seq data analyses demonstrated that DREAM and MYBL2-MuvB (MMB), two switchable MuvB-based complexes, bind the CHR elements in the ATAD2 promoter, representing a typical feature and principle mechanism of the periodic regulation of G2/M genes. As a downstream target of MYBL2, ATAD2 deletion significantly impaired MYBL2-driven cell proliferation. Intriguingly, ATAD2 silencing also fed back to destabilize the MYBL2 protein. The significant coexpression of MYBL2 and ATAD2 at both the bulk tissue and single-cell levels highlights the existence of the MYBL2-ATAD2 signaling in OC patients. This signaling is activated during tumorigenesis and correlated with TP53 mutation, and its hyperactivation was found especially in high-grade serous and drug-resistant OCs. Disrupting this signaling by CRISPR/Cas9-mediated ATAD2 ablation inhibited the in vivo growth of OC in a subcutaneous tumor xenograft mouse model, while pharmacologically targeting this signaling with an ATAD2 inhibitor demonstrated high therapeutic efficacy in both drug-sensitive and drug-resistant OC cells. Collectively, we identified a novel MYBL2-ATAD2 proliferative signaling axis and highlighted its potential application in developing new therapeutic strategies, especially for high-grade serous and drug-resistant OCs.

Electrochemical Detection of Carboplatin-Resistance in Ovarian Cancer

Epithelial ovarian cancer (EOC) has the highest mortality rate among gynecological cancers and affects patients on all continents. Primary treatments involve surgery and the administration of chemotherapeutics, such as carboplatin, which is listed by the World Health Organization as an essential medication for the treatment of human cancers. Unfortunately, due to high rates of drug resistance of EOC towards carboplatin, cancer relapse rates are devastating, and the mechanisms of chemoresistance to carboplatin have not been adequately identified. Consequently, there is a dire need for innovative strategies that are able to detect carboplatin resistance in cancer and to further our understanding of the fundamental nature of chemoresistance towards carboplatin.The presented work describes the thorough electrochemical characterization of carboplatin. The uptake of carboplatin by ovarian cancer cells was quantified by electrochemistry to better understand mechanisms of carboplatin chemoresistance. Scanning Electrochemical Microscopy studies demonstrate a differential behavior between drug-susceptible and drug-resistant ovarian cancer cells, in response to carboplatin exposure. Results emerging from this research might be important for future medical research, developing diagnostic and treatment strategies to combat chemoresistance.

Abstract 4047: Targeted liposomes against ovarian cancer

Abstract Purpose: Cisplatin (CPT) is a first-line chemotherapeutic agent for the treatment of ovarian cancer. However, CPT has severe adverse effects. The purpose of this study is to develop targeted liposomes that selectively target the xCT transporter which is upregulated in ovarian cancer and carry CPT to ovarian cancer only, thereby avoiding the adverse effects of CPT. We evaluated the stability, the cytotoxicity and the cellular uptake of targeted liposomes in ovarian cancer cell lines. Methods: CPT was encapsulated by the remote loading method in liposomes. The stability of liposomes was evaluated by measuring the drug-leakage from liposomes and the growth of liposome size stored at 4°C and room temperature over a 30-day period. For the drug-leakage study, liposomes were placed into a dialysis tubing and dialysate aliquots were removed and analyzed twice weekly for CPT content. The liposome size was evaluated using Dynamic Light Scattering (Nano Brook Omni, Brookhaven Instruments). The cellular uptake of targeted liposomes (encapsulating the fluorescent dye sulforhodamine B, SRB) was evaluated in drug-resistant (A2870cis, OVCAR3, OVCAR4, IGROV1, and NCI/ADR-RES) and drug sensitive (A2870 and OVCAR8) ovarian cancer cell lines (purchased from the NIH), were evaluated using flow cytometry (BD Accuri C6). The cytotoxicity of CPT in targeted liposomes was evaluated in the various ovarian cell lines using the MTS assay (Novus Biologicals). Results: The targeted liposomes over the 30-day period, show that 6.8% of the total loaded CPT leaked out of the liposomes. During that period the growth of the liposomes was <5% for the liposomes stored at 4°C and <1% of their initial size, stored at 25°C. The cellular uptake of ovarian cancer cell lines, A2870, A2870cis, OVCAR3, OVCAR4, OVCAR8, and NCI/ADR-Res the targeted SRB loaded liposomes showed significantly more fluorescence intensity when compared to free SRB and non-targeted liposomes (p<0.05). In the cell line IGROV1, there is a similar trend seen, where there was a higher fluorescence intensity compared to free SRB and non-targeted. The fluorescence intensity was found to be higher compared to non-targeted liposomes (p<0.0001) but not statistically significant higher compared to free SRB. For cytotoxicity, a similar trend is seen in cell lines A2870, A2870cis, IGROV1, OVCAR3, OVCAR4, OVCAR8, and NCI/ADR-res, where the cisplatin loaded targeted liposomes had the lowest IC50 compared to free drug and non-targeted liposomes. Non-targeted liposomes had the highest IC50 values compared to free drug and targeted liposomes. In cell lines A2870, A2870cis, IGROV1, OVCAR3, OVCAR4, OVCAR8, and NCI/ADR-res the IC50 values show a 2.4, 5.3, 4.1, 3.3, 1.7, 1.6, and 2.5-fold lower values compared to free cisplatin, respectively. Conclusion: Targeted liposomes encapsulating CPT show stability, enhanced in-vitro cellular uptake and anti-cancer activity in resistant and sensitive ovarian cancer cell lines. Citation Format: Antonia Marashio, Maria (Mary) P. Lambros, Adenike Oyegbesan. Targeted liposomes against ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4047.

The significance of interferon gamma inducible protein 16 (IFI16) expression in drug resistant ovarian cancer cell lines.

Inherent or developed during treatment drug resistance is the main reason for the low effectiveness of chemotherapy in ovarian cancer. IFI16 is a cytoplasmic/nuclear protein involved in response to virus's infection and cell cycle arrest associated with the cellular senescence. Here we performed a detailed IFI16 expression analysis in ovarian cancer cell lines sensitive (A2780) and resistant to doxorubicin (DOX) (A2780DR1 and A2780DR2) and paclitaxel (PAC) (A2780PR1). IFI16 mRNA level, protein level in the nuclear and cytoplasmic fraction (Western blot analysis), the protein expression in cancer cells and nuclei (immunofluorescence analysis) and cancer patient lesions (immunohistochemistry) were performed in this study. We observed upregulation of IFI16 expression in drug resistant cell lines with dominant cytoplasmic localization in DOX-resistant cell lines and nuclear one in the PAC-resistant cell line. The most abundantly overexpressed isoforms of IFI16 were IFI16A and IFI16C. Finally, an analysis of a histological type of ovarian cancer (immunohistochemistry) showed expression in serous ovarian cancer. Expression of IFI16 in drug-resistant cell lines suggests its role in drug resistance development in ovarian cancer. Expression in serous ovarian cancer suggests its role in the pathogenesis of this histological type.

Multi-component redox system for selective and potent antineoplastic activity towards ovarian cancer cells

Ovarian cancer is the deadliest gynecological cancer which rarely causes symptoms, and goes undetected until reaching the advanced stage of drug-resistant metastases. The cationic porphyrin meso-tetra(4-N-methylpyridyl)porphine (TMPyP) is a well-known photosensitizer (PS) used in photodyamic therapy (PDT) for curing cancer due to its strong affinity for DNA and high yield of reactive oxygen species (ROS) upon light activation. The practicality to irradiate tumor cells alone in the physiological system being slim (due to the close proximity of healthy cells and tumors), we looked for a variation in the PDT using a mixture of TMPyP with 1,5-dihydroxynapthalene (DHN) and Fe(III) ions at a mole ratio of 1:20:17 (drug combo) respectively in aqueous solution. The drug combo needs no photoactivation in H2O2 rich environment (mimicking the microenvironment of cancer/tumor), where it generates ȮH and juglone, the latter being a known potent anticancer agent. In vitro studies of the drug combo in drug resistant and sensitive ovarian cancer cell lines showed drastic growth inhibition and cell death compared to normal epithelial cells. The drug combo provides an effective and non-invasive alternative to conventional PDT, exploiting the cytosolic carcinogenic H2O2 to produce an efficient anticancer treatment. The unique action of cancer-specific cytotoxicity arises from the redox chemistry involving activation of Fe(III) as the oxidizing agent to generate juglone, which utilizes the cytosolic ROS in cancer cells against itself.

In vitro assessment of stearyl triphenyl phosphonium toxicity in drug-resistant tumor cells

Introduction: The triphenyl phosphonium residue is a well-documented mitochondriotropic that has been shown to improve the accumulation of biomolecules in mitochondria. Stearyl triphenyl phosphonium (STPP) modified liposomes have been shown to facilitate the selective accumulation of various biomolecules in mitochondria resulting in improved effect in-vitro and in-vivo. More recently, STPP was reported to have higher toxicity towards a drug resistant ovarian cancer cell line compare to a non-drug resistant cell line. The purpose of this study was to further investigate STPP toxicity using multiple drug resistant and non-drug resistant cell lines. Methods: STPP was incorporated into phosphatidylcholine cholesterol liposomes using the thin film hydration method. Mean particle size and zeta potential was measured using dynamic light scattering. The 5,5,6,6′-tetrachloro-1,1′,3,3′ tetraethylbenzimi-dazoylcarbocyanine iodide (JC-1) dye accumulation assay was used as an indicator of mitochondrial membrane potential in the tested cell lines. Cytotoxicity of the preparations towards different cell lines was determined using light microscopy and the CellTiter 96® AQueous One Solution Cell Proliferation assay. Results: The JC-1 accumulation assay confirmed that the drug-resistant cell lines had significantly higher dye accumulation than the non-drug resistant cell lines. Higher cytotoxicity of STPP towards drug resistant cell line was seen when incorporated into liposomes but not when dissolved in dimethyl sulfoxide (DMSO). STPP showed a comparable toxicity profile to the known oxidative phosphorylation uncoupler carbonyl cyanide p-trifluoro-methoxyphenyl hydrazone (FCCP). Discussion: Taken together, the data suggest that higher STPP toxicity in the drug-resistant cell lines is influenced by the presence of liposomal lipids and that STPP acts in a way similar to an oxidative phosphorylation uncoupler and is therefore more toxic to the drug-resistant cells that rely on a higher mitochondrial membrane potential to maintain their viability.

Predicting response to platinum and non-platinum drugs through bioluminescence resonance energy transfer (BRET) based bio-molecular interactions in platinum resistant epithelial ovarian cancer

Therapy induced rewiring of signalling networks often lead to acquirement of platinum-resistance, thereby necessitating the use of non-platinum agents as second-line treatment particularly for epithelial ovarian cancer (EOC). A prior subject-specific assessment can guide the choice of optimal non-platinum agent/s and possible targeted therapeutic/s. Assessment of protein-protein interactions are superior to simple cytotoxicity assays to determine therapeutic efficacy and associated molecular responses. Utilizing improved PIP3-AKT and ERK1/2 activation Bioluminescence Resonance Energy Transfer (BRET) sensors, we report chemotherapy-induced ERK1/2 activation predominantly in cisplatin-paclitaxel resistant EOC cells and increased activation of both ERK1/2 and AKT in malignant ascites derived cancer cells from platinum-resistant patients but not from treatment-naive or platinum-sensitive relapse patients. Further, majority of the non-platinum drugs except irinotecan increased ERK1/2 activation in platinum-taxol resistant cells as observed by live-cell BRET assessment which were associated with p90RSK1/2 and BAD activation along with upregulation of multidrug transporter gene ABCC1 and cell survival genes like cyclin D1 and Bcl2. Interestingly, only irinotecan was able to sensitize these resistant cells. Altogether, this first report of BRET based sensing of molecular pathway activations in platinum resistant cell lines and patient's derived cancer cells highlight the clinical potential of BRET sensors in management of therapy resistant cancer.

3D Clinorotation Affects Drug Sensitivity of Human Ovarian Cancer Cells

Numerous studies have reported that gravity alteration displays a remarkable influence on the biological processes of cancer cells. Therefore, gravity-related experiments have become a promising method of improving knowledge in the field of cancer biology and may be useful to detect remarkable implications for future cancer treatment. Taking this concept further, we used a 3D clinostat (3D-C; 10 rpm of changing direction) to analyse the effect of short-term exposure to simulated microgravity (sμg) on cisplatin sensitivity of drug resistant human ovarian cancer cells SKOV-3. This allowed us to investigate whether altered gravity affects drug susceptibility of cancer cells. Our studies revealed that sμg exposure affects SKOV-3 cells morphology and drug efficiency. We observed the altered cell shape, the presence of membrane blebbing and lamellipodia as well as the lack of filopodia when the cells had been cultured on 3D-C for 2 h. Cytotoxicity, cell death and cell cycle assays showed an increased percentage of apoptotic cells and G0/G1 cell cycle arrest after exposure on the 3D-C with cisplatin in comparison to the static control, non clinorotated cells. Cell proliferation and migration were altered after the exposure to sμg as well. Our studies suggest that the altered gravity conditions affected cellular mechanisms involved in cisplatin resistance, resulting in higher sensitivity of cancer cells to the chemotherapeutic. The investigation and clarification of these results may be a crucial step toward improving our understanding of the relationship between cellular resistance to chemotherapy and the response to altered gravitational conditions.

MKNK2 enhances chemoresistance of ovarian cancer by suppressing autophagy via miR-125b

Chemoresistance is a major cause for high mortality and poor survival in patients with ovarian cancer. Changes of cellular autophagy is associated with tumor cell chemoresistance. MAP kinase interacting serine/threonine kinase 2 (MKNK2) belongs to the protein kinase superfamily mediating cell cycle, apoptosis and angiogenesis. However, its effects on chemoresistance during ovarian cancer development remain unclear. In this study, we found that MKNK2 expression levels were markedly up-regulated in chemoresistant ovarian cancer cells compared with the sensitive cells. In addition, significantly increased expression of MKNK2 was detected in clinical ovarian cancer tissues, particularly in tumor samples from patients with drug resistance, and high MKNK2 expression is closely associated with poor prognosis. Our in vitro experiments subsequently showed that MKNK2 knockdown markedly reduced the proliferation of chemoresistant ovarian cancer cells, which was confirmed in SKOV3/DDP xenograft mouse models. Importantly, MKNK2 knockdown considerably induced autophagy in ovarian cancer cells with drug resistance, which was involved in the suppression of cell proliferation. Of note, we showed that miR-125b directly targeted MKNK2, and a negative correlation was observed between the expression of them in clinical tumor tissues. MKNK2 silence also increased miR-125b expression levels in drug-resistant ovarian cancer cells. Intriguingly, MKNK2 knockdown-suppressed cell proliferation and -induced autophagy were almost abrogated by miR-125b inhibition in chemoresistant ovarian cancer cells. Together, these findings demonstrated that MNKN2 is responsible for chemoresistance in ovarian cancer through modulating autophagy by targeting miR-125b, which may be a promising therapeutic target to develop strategies against ovarian cancer with drug resistance.

Targeting eukaryotic elongation factor-2 kinase suppresses the growth and peritoneal metastasis of ovarian cancer

Ovarian cancer (OC) is the deadliest gynecological cancer and is currently incurable with standard treatment regimens. Early invasion, intraperitoneal metastasis, and an aggressive course are the hallmarks of OC. The major reason for poor prognosis is a lack of molecular targets and highly effective targeted therapies. Therefore, identification of novel molecular targets and therapeutic strategies is urgently needed to improve OC survival. Herein we report that eukaryotic elongation factor-2 kinase (EF2K) is highly upregulated in primary and drug-resistant OC cells and its expresssion associated with progression free survival TCGA database) and promotes cell proliferation, survival, and invasion. Downregulation of EF2K reduced expression of integrin β1 and cyclin D1 and the activity of the Src, phosphoinositide 3-kinase/AKT, and nuclear factor-κB signaling pathways. Also, in vivo, therapeutic targeting of EF2K by using single-lipid nanoparticles containing siRNA led to substantial inhibition of ovarian tumor growth and peritoneal metastasis in nude mouse models. Furthermore, EF2K inhibition led to robust apoptosis and markedly reduced intratumoral proliferation in vivo in ovarian tumor xenografts and intraperitoneal metastatic models. Collectively, our data suggest for the first time that EF2K plays an important role in OC growth, metastasis, and progression and may serve as a novel therapeutic target in OCs.