Inhibiting ERK/Mnk/eIF4E broadly sensitizes ovarian cancer response to chemotherapy

Dual MNK/VEGFR2 Inhibitor JDB153 Enhances Immunotherapeutic Efficiency and Chemosensitivity in Lung Cancer

Lung cancer continues to be the primary cause of cancer-related mortality worldwide, with non-small cell lung cancer (NSCLC) being the predominant type. Dysregulation of protein translation that participates in cell proliferation is an important factor to define oncogenic processes and cancer development. The eukaryotic initiation factor 4E (eIF4E) regulates ribosomal translation of proteins from mRNA, and the mitogen-activated protein kinase interacting kinases (MNKs) is reported to be the only kinases that can phosphorylate eIF4E. Substantial previous work has proven that the MNK-eIF4E axis is usually dysregulated in many cancer types. Moreover, abnormal angiogenesis is essential for tumorigenesis and cancer progression, and vascular endothelial growth factors (VEGF) together with their receptors play multiple crucial roles in angiogenesis, especially VEGFR2. In this study, we report a novel dual MNK/VEGFR2 inhibitor named JDB153 and investigate its antitumor effects in NSCLC. JDB153 can effectively inhibit the phosphorylation of eIF4E and VEGFR2, suppress proliferation, migration and invasion, promote apoptosis, and induce cycle arrest of lung cancer cells. Importantly, JDB153 exhibits antitumor activity and synergizes with anti-PD-1 therapy and cisplatin with reliable safety. Our findings reveal the potential value of JDB153 in lung cancer as monotherapy or in combination with immunotherapy and chemotherapy, with the hope to provide a novel combinational strategy for NSCLC treatment clinically.

Phase Ib Pharmacodynamic Study of the MNK Inhibitor Tomivosertib (eFT508) Combined With Paclitaxel in Patients With Refractory Metastatic Breast Cancer

PURPOSE

Preclinical data motivate clinical evaluation of inhibitors of MAPK-interacting kinases 1 and 2 (MNK1/2). We conducted a phase 1b clinical trial to study target engagement and safety of tomivosertib, a MNK1/2 inhibitor, alone and in combination with paclitaxel.

PATIENTS AND METHODS

Eligible patients had metastatic breast cancer resistant to standard-of-care treatments. Biopsies were obtained at baseline and during treatment with tomivosertib, and then tomivosertib was continued with the addition of paclitaxel until disease progression or toxicity. Serum drug levels were measured, and pharmacodynamic endpoints included IHC, proteomics, translatomics, and imaging mass cytometry.

RESULTS

Tomivosertib alone and in combination with paclitaxel was well tolerated. There was no pharmacokinetic interaction between the drugs. We observed a clear reduction in phosphorylation of eIF4E at S209, a major substrate of MNK1/2, and identified tomivosertib-induced perturbations in the proteome, translatome, and cellular populations of biopsied metastatic breast cancer tissue.

CONCLUSIONS

We conclude that tomivosertib effectively inhibits MNK1/2 activity in metastatic breast cancer tissue and that it can safely be combined with paclitaxel in future phase II studies. We demonstrate feasibility of using proteomic profiles, translatomic profiles, and spatial distribution of immune cell infiltrates for clinical pharmacodynamic studies.

Role of RGD-binding Integrins in ovarian cancer progression, metastasis and response to therapy

Integrins are transmembrane receptors that play a crucial role in cell adhesion and signaling by connecting the extracellular environment to the intracellular cytoskeleton. After binding with specific ligands in the extracellular matrix (ECM), integrins undergo conformational changes that transmit signals across the cell membrane. The integrin-mediated bidirectional signaling triggers various cellular responses, such as changes in cell shape, migration and proliferation. Irregular integrin expression and activity are closely linked to tumor initiation, angiogenesis, cell motility, invasion, and metastasis. Thus, understanding the intricate regulatory mechanism is essential for slowing cancer progression and preventing carcinogenesis. Among the four classes of integrins, the arginine-glycine-aspartic acid (RGD)-binding integrins stand out as the most crucial integrin receptor subfamily in cancer and its metastasis. Dysregulation of almost all RGD-binding integrins promotes ECM degradation in ovarian cancer, resulting in ovarian carcinoma progression and resistance to therapy. Preclinical studies have demonstrated that targeting these integrins with therapeutic antibodies and ligands, such as RGD-containing peptides and their derivatives, can enhance the precision of these therapeutic agents in treating ovarian cancer. Therefore, the development of novel therapeutic agents is essential for treating ovarian cancer. This review mainly discusses genes and their importance across different ovarian cancer subtypes, the involvement of RGD motif-containing ECM proteins in integrin-mediated signaling in ovarian carcinoma, ongoing, completed, partially completed, and unsuccessful clinical trials of therapeutic agents, as well as existing limitations and challenges, advancements made so far, potential strategies, and directions for future research in the field. Insight Box Integrin-mediated signaling regulates cell migration, proliferation and differentiation. Dysregulated integrin expression and activity promote tumor growth and dissemination. Thus, a proper understanding of this complex regulatory mechanism is essential to delay cancer progression and prevent carcinogenesis. Notably, integrins binding to RGD motifs play an important role in tumor initiation, evolution, and metastasis. Preclinical studies have demonstrated that therapeutic agents, such as antibodies and small molecules with RGD motifs, target RGD-binding integrins and disrupt their interactions with the ECM, thereby inhibiting ovarian cancer proliferation and migration. Altogether, this review highlights the potential of RGD-binding integrins in providing new insights into the progression and metastasis of ovarian cancer and how these integrins have been utilized to develop effective treatment plans.

miR-483-5p orchestrates the initiation of protein synthesis by facilitating the decrease in phosphorylated Ser209eIF4E and 4E-BP1 levels

Eukaryotic initiation factor 4E (eIF4E) is a pivotal protein involved in the regulatory mechanism for global protein synthesis in both physiological and pathological conditions. MicroRNAs (miRNAs) play a significant role in regulating gene expression by targeting mRNA. However, the ability of miRNAs to regulate eIF4E and its phosphorylation remains relatively unknown. In this study, we predicted and experimentally verified targets for miR-483-5p, including eukaryotic translation initiation factor eIF4E and its binding proteins, 4E-BPs, that regulate protein synthesis. Using the Web of Science database, we identified 28 experimentally verified miR-483-5p targets, and by the TargetScan database, we found 1818 predicted mRNA targets, including EIF4E, EIF4EBP1, and EIF4EBP2. We verified that miR-483-5p significantly reduced ERK1 and MKNK1 mRNA levels in HEK293 cells. Furthermore, we discovered that miR-483-5p suppressed EIF4EBP1 and EIF4EBP2, but not EIF4E. Finally, we found that miR-483-5p reduced the level of phosphorylated eIF4E (pSer209eIF4E) but not total eIF4E. In conclusion, our study suggests that miR-483-5p's multi-targeting effect on the ERK1/ MKNK1 axis modulates the phosphorylation state of eIF4E. Unlike siRNA, miRNA can have multiple targets in the pathway, and thereby exploring the role of miR-483-5p in various cancer models may uncover therapeutic options.

Tephrosin Suppresses the Chemoresistance of Paclitaxel-Resistant Ovarian Cancer via Inhibition of FGFR1 Signaling Pathway

Ovarian cancer is the leading cause of death among gynecologic cancers. Paclitaxel is used as a standard first-line therapeutic agent for ovarian cancer. However, chemotherapeutic resistance and high recurrence rates are major obstacles to treating ovarian cancer. We have found that tephrosin, a natural rotenoid isoflavonoid, can resensitize paclitaxel-resistant ovarian cancer cells to paclitaxel. Cell viability, immunoblotting, and a flow cytometric analysis showed that a combination treatment made up of paclitaxel and tephrosin induced apoptotic death. Tephrosin inhibited the phosphorylation of AKT, STAT3, ERK, and p38 MAPK, all of which simultaneously play important roles in survival signaling pathways. Notably, tephrosin downregulated the phosphorylation of FGFR1 and its specific adapter protein FRS2, but it had no effect on the phosphorylation of the EGFR. Immunoblotting and a fluo-3 acetoxymethyl assay showed that tephrosin did not affect the expression or function of P-glycoprotein. Additionally, treatment with N-acetylcysteine did not restore cell cytotoxicity caused by a treatment combination made up of paclitaxel and tephrosin, showing that tephrosin did not affect the reactive oxygen species scavenging pathway. Interestingly, tephrosin reduced the expression of the anti-apoptotic factor XIAP. This study demonstrates that tephrosin is a potent antitumor agent that can be used in the treatment of paclitaxel-resistant ovarian cancer via the inhibition of the FGFR1 signaling pathway.

Computational Investigations on Reaction Mechanisms of the Covalent Inhibitors Ponatinib and Analogs Targeting the Extracellular Signal-Regulated Kinases

As an important cancer therapeutic target, extracellular signal-regulated kinases (ERK) are involved in triggering various cellular responses in tumors. Regulation of the ERK signaling pathway by the small molecular inhibitors is highly desired for the sake of cancer therapy. In contrast to the routine inhibitors targeting ERKs through long-range non-bonding interactions, Ponatinib, a covalent inhibitor to ERK2 with a macrocyclic structure characterized by the α,β-C=C unsaturated ketone, can form the stable -C(S)-C(H)-type complex via the four-center barrier due to the nucleophilic addition reaction of the thiol group of the Cys166 residue of ERK2 with the C=C double bond of Ponatinib with reaction free-energy barrier of 47.2 kcal/mol. Reaction mechanisms for the covalent binding were calculated using QM/MM methods and molecular dynamics simulations. The interaction modes and the corresponding binding free energies were obtained for the non-covalent and covalent complexation. The binding free energies of the non-covalent and covalent inhibitions are 14.8 kcal/mol and 33.4 kcal/mol, respectively. The mechanistic study stimulated a rational design on the modified Ponatinib structure by substituting the C=C bond with the C=N bond. It was demonstrated that the new compound exhibits better inhibition activity toward ERK2 in term of both thermodynamic and kinetic aspects through the covalent binding with a lower reaction free-energy barrier of 23.1 kcal/mol. The present theoretical work sheds new light on the development of the covalent inhibitors for the regulation of ERKs.

miRNAs are now starring in "No Time to Die: Overcoming the chemoresistance in cancer"

Cancer is a leading cause of death globally, with about 19.3 million new cases reported each year. Current therapies for cancer management include-chemotherapy, radiotherapy, and surgery. However, they are loaded with side effects and tend to cause toxicity in the patient's body posttreatment, ultimately hindering the response towards the treatment building up resistance. This is where noncoding RNAs such as miRNAs help provide us with a helping hand for taming the chemoresistance and providing potential holistic cancer management. MicroRNAs are promising targets for anticancer therapy as they perform critical regulatory roles in various signaling cascades related to cell proliferation, apoptosis, migration, and invasion. Combining miRNAs and anticancer drugs and devising a combination therapy has managed cancer well in various independent studies. This review aims to provide insights into how miRNAs play a mechanistic role in cancer development and progression and regulate drug resistance in various types of cancers. Furthermore, next-generation novel therapies using miRNAs in combination with anticancer treatments in multiple cancers have been put forth and how they improve the efficacy of the treatments. Exemplary studies currently in the preclinical and clinical models have been summarized. Ultimately, we briefly talk through the challenges that come forward with it and minimize them.

Optimized Transcriptional Signature for Evaluation of MEK/ERK Pathway Baseline Activity and Long-Term Modulations in Ovarian Cancer

Ovarian cancer is the most aggressive and lethal of all gynecologic malignancies. The high activity of the MEK/ERK signaling pathway is tightly associated with tumor growth, high recurrence rate, and treatment resistance. Several transcriptional signatures were proposed recently for evaluation of MEK/ERK activity in tumor tissue. In the present study, we validated the performance of a robust multi-cancer MPAS 10-gene signature in various experimental models and publicly available sets of ovarian cancer samples. Expression of four MPAS genes (PHLDA1, DUSP4, EPHA2, and SPRY4) displayed reproducible responses to MEK/ERK activity modulations across several experimental models in vitro and in vivo. Levels of PHLDA1, DUSP4, and EPHA2 expression were also significantly associated with baseline levels of MEK/ERK pathway activity in multiple human ovarian cancer cell lines and ovarian cancer patient samples available from the TCGA database. Initial platinum therapy resistance and advanced age at diagnosis were independently associated with poor overall patient survival. Taken together, our results demonstrate that the performance of transcriptional signatures is significantly affected by tissue specificity and aspects of particular experimental models. We therefore propose that gene expression signatures derived from comprehensive multi-cancer studies should be always validated for each cancer type.

Inhibition of miR-15a-5p Promotes the Chemoresistance to Pirarubicin in Hepatocellular Carcinoma via Targeting eIF4E

Chemoresistance has become a primary hurdle in the therapeutic outcome of hepatocellular carcinoma. Substantial evidences have demonstrated that microRNAs (miRNAs) are closely associated with the chemoresistance of hepatocellular carcinoma (HCC). Our investigation is aimed at testifying the influence of microRNA-15a-5p (miR-15a-5p)/eukaryotic translation initiation factor 4E (eIF4E) on hepatocellular carcinoma resistance to pirarubicin (THP). In our study, miR-15a-5p expression was increased in THP-treated HepG2 cells. Downregulation of miR-15a-5p blocked cell growth and elevated cell apoptosis of HepG2 cells treated with THP. Moreover, eIF4E was verified as a direct target of miR-15a-5p by binding its 3'-UTR, which was confirmed by luciferase report experiment. Additionally, eIF4E was negatively associated with the miR-15a-5p expression in HepG2 cells. Mechanically, eIF4E was proven as a specific downstream of miR-15a-5p and mediated the effects of miR-15a-5p on cell viability and apoptosis of HepG2 cells treated with THP. These findings supported that miR-15a-5p facilitated THP resistance of hepatocellular carcinoma cells by modulating eIF4E, thus providing an experimental basis that miR-15a-5p might act as a novel diagnostic target in hepatocellular carcinoma resistance to THP.

Targeting mTOR and eIF4E: a feasible scenario in ovarian cancer therapy

Ovarian carcinoma is one of the most common causes for cancer death in women; lack of early diagnosis and acquired resistance to platinum-based chemotherapy account for its poor prognosis and high mortality rate. As with other cancer types, ovarian cancer is characterized by dysregulated signaling pathways and protein synthesis, which together contribute to rapid cellular growth and invasiveness. The mechanistic/mammalian target of rapamycin (mTOR) pathway represents the core of different signaling pathways regulating a number of essential steps in the cell, among which protein synthesis and the eukaryotic initiation factor 4E (eIF4E), the mRNA cap binding protein, is one of its downstream effectors. eIF4E is a limiting factor in translation initiation and its overexpression is a hallmark in many cancers. Because its action is regulated by a number of factors that compete for the same binding site, eIF4E is an ideal target for developing novel antineoplastic drugs. Several inhibitors targeting the mTOR signaling pathway have been designed thus far, however most of these molecules show poor stability and high toxicity in vivo. This minireview explores the possibility of targeting mTOR and eIF4E proteins, thus impacting on translation initiation in ovarian cancer, describing the most promising experimental strategies and specific inhibitors that have been shown to have an effect on other kinds of cancers.

Inhibition of sphingosine kinase 2 down-regulates ERK/c-Myc pathway and reduces cell proliferation in human epithelial ovarian cancer

Background

Epithelial ovarian cancer (EOC) is the leading cause of death from female cancers. In our previous study, sphingosine kinase 2 (SphK2) inhibitor was shown to display anti-EOC activities. The purpose of this study was to evaluate further the expression characteristics and clinical significance of SphK2 in EOC and to explore the roles and underlying mechanisms of SphK2 in EOC cell survival.

Methods

The expression of SphK2 was examined by immunohistochemistry (IHC) and Western blot, and its clinical implications and prognostic significance were analyzed. We performed a cellular proliferation assay, and a mouse xenograft model was established to confirm the roles of SphK2 in vitro and in vivo. Cell cycle analysis, apoptosis assay, and Western blot were performed to examine cell cycle progression and apoptosis rate. Gene set enrichment analysis (GSEA), and Western blot were used to investigate the downstream signaling pathways related to SphK2 function.

Results

The expression level of SphK2 was shown to be associated with stage, histological grade, lymph node metastasis, and ascites status. More importantly, a high SphK2 expression level was a prognostic indicator of overall survival (OS) and relapse-free survival (RFS). Moreover, knockdown of SphK2 arrested cell cycle progression and inhibited EOC cell proliferation both in vitro and in vivo. Furthermore, ERK/c-Myc, the key pathway in EOC progression, was important for SphK2-mediated mitogenic action in EOC cells.

Conclusions

Our findings provided the first evidence that SphK2 played a crucial role in EOC proliferation by regulating the ERK/c-Myc pathway. This indicated that SphK2 might serve as a prognostic marker and potential therapeutic target in EOC.

The MEK1/2 Pathway as a Therapeutic Target in High-Grade Serous Ovarian Carcinoma

High-grade serous ovarian carcinoma (HGSOC) is the deadliest of gynecological cancers due to its high recurrence rate and acquired chemoresistance. RAS/MEK/ERK pathway activation is linked to cell proliferation and therapeutic resistance, but the role of MEK1/2-ERK1/2 pathway in HGSOC is poorly investigated. We evaluated MEK1/2 pathway activity in clinical HGSOC samples and ovarian cancer cell lines using immunohistochemistry, immunoblotting, and RT-qPCR. HGSOC cell lines were used to assess immediate and lasting effects of MEK1/2 inhibition with trametinib in vitro. Trametinib effect on tumor growth in vivo was investigated using mouse xenografts. MEK1/2 pathway is hyperactivated in HGSOC and is further stimulated by cisplatin treatment. Trametinib treatment causes cell cycle arrest in G1/0-phase and reduces tumor growth rate in vivo but does not induce cell death or reduce fraction of CD133+ stem-like cells, while increasing expression of stemness-associated genes instead. Transient trametinib treatment causes long-term increase in a subpopulation of cells with high aldehyde dehydrogenase (ALDH)1 activity that can survive and grow in non-adherent conditions. We conclude that MEK1/2 inhibition may be a promising approach to suppress ovarian cancer growth as a maintenance therapy. Promotion of stem-like properties upon MEK1/2 inhibition suggests a possible mechanism of resistance, so a combination with CSC-targeting drugs should be considered.

A control theoretic three timescale model for analyzing energy management in mammalian cancer cells

Interaction among different pathways, such as metabolic, signaling and gene regulatory networks, of cellular system is responsible to maintain homeostasis in a mammalian cell. Malfunctioning of this cooperation may lead to many complex diseases, such as cancer and type 2 diabetes. Timescale differences among these pathways make their integration a daunting task. Metabolic, signaling and gene regulatory networks have three different timescales, such as, ultrafast, fast and slow respectively. The article deals with this problem by developing a support vector regression (SVR) based three timescale model with the application of genetic algorithm based nonlinear controller. The proposed model can successfully capture the nonlinear transient dynamics and regulations of such integrated biochemical pathway under consideration. Besides, the model is quite capable of predicting the effects of certain drug targets for many types of complex diseases. Here, energy and cell proliferation management of mammalian cancer cells have been explored and analyzed with the help of the proposed novel approach. Previous investigations including in silico/in vivo/in vitro experiments have validated the results (the regulations of glucose transporter 1 (glut1), hexokinase (HK), and hypoxia-inducible factor-1 α (HIF-1 α ) among others, and the switching of pyruvate kinase (M2 isoform) between dimer and tetramer) generated by this model proving its effectiveness. Subsequently, the model predicts the effects of six selected drug targets, such as, the deactivation of transketolase and glucose-6-phosphate isomerase among others, in the case of mammalian malignant cells in terms of growth, proliferation, fermentation, and energy supply in the form of adenosine triphosphate (ATP).

The high-risk HPV E6 proteins modify the activity of the eIF4E protein via the MEK/ERK and AKT/PKB pathways

Previous studies have proposed that the human papillomavirus (HPV) E6 oncoproteins modify the transcriptional activity of eIF4E through mechanisms dependent on p53 degradation. However, the effect of these oncoproteins on pathways regulating the activity of the eIF4E protein remains poorly understood. Hence, we investigated the mechanisms whereby E6 proteins regulate the activity of the eIF4E protein and its effect on target genes. Overexpression of E6 constructs (HPV-6, HPV-16, HPV-18, and HPV52) showed that E6 oncoproteins increased phosphorylation of the eIF4E protein (Serine-209). This result was mainly mediated by phosphorylation of the 4EBP1 protein via the PI3K/AKT pathway. Additionally, the pharmacological inhibition of eIF4E phosphorylation in cervical cancer cell lines substantially reduced the protein levels of CCND1 and ODC1, indicating that E6 of the high-risk genotypes may modify protein synthesis of the eIF4E target genes by increasing the activity of the AKT and ERK pathways.

Eukaryotic translation initiation factors as promising targets in cancer therapy

The regulation of the translation of messenger RNA (mRNA) in eukaryotic cells is critical for gene expression, and occurs principally at the initiation phase which is mainly regulated by eukaryotic initiation factors (eIFs). eIFs are fundamental for the translation of mRNA and as such act as the primary targets of several signaling pathways to regulate gene expression. Mis-regulated mRNA expression is a common feature of tumorigenesis and the abnormal activity of eIF complexes triggered by upstream signaling pathways is detected in many tumors, leading to the selective translation of mRNA encoding proteins involved in tumorigenesis, metastasis, or resistance to anti-cancer drugs, and making eIFs a promising therapeutic target for various types of cancers. Here, we briefly outline our current understanding of the biology of eIFs, mainly focusing on the effects of several signaling pathways upon their functions and discuss their contributions to the initiation and progression of tumor growth. An overview of the progress in developing agents targeting the components of translation machinery for cancer treatment is also provided.

Phosphorylation of the mRNA cap-binding protein eIF4E and cancer

Dysregulated protein synthesis is frequently involved in oncogenesis and cancer progression. Translation initiation is thought to be the rate-limiting step in protein synthesis, and the mRNA 5' cap-binding protein eukaryotic translation initiation factor 4E (eIF4E) is a pivotal factor that initiates translation. The activities of eIF4E are regulated at multiple levels, one of which is through its phosphorylation at Serine 209 by the mitogen-activated protein kinase-interacting kinases (MNKs, including MNK1 and MNK2). Benefiting from novel mouse genetic tools and pharmacological MNK inhibitors, our understanding of a role for eIF4E phosphorylation in tumor biology and cancer therapy has greatly evolved in recent years. Importantly, recent studies have found that the level of eIF4E phosphorylation is frequently upregulated in a wide variety of human cancer types, and phosphorylation of eIF4E drives a number of important processes in cancer biology, including cell transformation, proliferation, apoptosis, metastasis and angiogenesis. The MNK-eIF4E axis is being assessed as a therapeutic target either alone or in combination with other therapies in different cancer models. As novel MNK inhibitors are being developed, experimental studies bring new hope to cure human cancers that are not responsive to traditional therapies. Herein we review recent progress on our understanding of a mechanistic role for phosphorylation of eIF4E in cancer biology and therapy.

WISP2 promotes cell proliferation via targeting ERK and YAP in ovarian cancer cells

Background

Wnt-inducible signaling pathway protein 2 (WISP2) is a wnt1-induced signaling pathway protein 2. Although studies indicate that WISP2 may promote the development of various tumors, its role in ovarian cancer remains unclear. The objective of the current study was to analyze the effects of WISP2 on the proliferation and migration of ovarian cancer cells in vitro and in vivo.

Results

Immunohistochemistry and western blotting indicated that WISP2 was highly expressed in various ovarian cancer tissues and cell lines, but weakly expressed in normal ovary tissue. WISP2 deletion inhibited cell growth, clone formation, and migration of ovarian cancer cells while promoting cell apoptosis and affecting the cell cycle. This growth inhibitory effect caused by WISP2 loss is due to the inhibition of phosphorylated extracellular signal-related kinase (p-ERK)1/2, as well as CCAAT/enhancer-binding protein α (CEBPα) and CEPBβ. In addition, WISP2 deletion also activated the Yes-associated protein (YAP).

Conclusion

WISP2 deletion inhibits ovarian cancer cell proliferation by affecting ERK signaling pathways.

GRHL2 Upregulation Predicts a Poor Prognosis and Promotes the Resistance of Serous Ovarian Cancer to Cisplatin

Background

GRHL2 has been shown to function in ovarian carcinogenesis. However, the relationship between GRHL2 and cisplatin (DDP) resistance in serous ovarian cancer (SOC) is not clear. The purpose of this study was to elucidate the function and mechanism of GRHL2 in DDP resistance of SOC.

Materials and Methods

Immunohistochemistry (IHC) was utilized to identify GRHL2 protein expression in DDP resistant and sensitive SOC tissues. GRHL2 mRNA and protein levels were identified using quantitative real-time PCR (qRT-PCR) and Western blotting in SKOV3/DDP and SKOV3 cell lines. We conducted loss- and gain-of-function experiments to uncover the consequence of GRHL2 knockdown or overexpression on the sensitivity of ovarian cancer cells to DDP in vitro and in vivo and the underlying mechanism.

Results

It was observed that expression of GRHL2 was higher in DDP resistant SOC tissues relative to DDP sensitive SOC tissues. In addition, the increased expression of GRHL2 led to shorter progression-free survival (PFS) and overall survival (OS). Meanwhile, the GRHL2 transcript and protein levels in SKOV3/DDP were also higher than SKOV3. Small hairpin RNA (shRNA)-facilitated GRHL2 gene knockdown considerably heightened the sensitivity of SKOV3/DDP cells to DDP by inhibiting proliferation and promoting apoptosis, while up-regulation of GRHL2 significantly reduced the sensitivity of SKOV3 cells to DDP by promoting proliferation and decreasing apoptosis. In addition, GRHL2 promotes DDP resistance of SOC through activation of ERK/MAPK signaling pathways.

Conclusion

Our results suggest that GRHL2 up-regulation predicts a poor prognosis and promotes the resistance of SOC to DDP. Therefore, GRHL2 may be a possible treatment target for cisplatin-resistant serous ovarian cancer.

Deeping in the Role of the MAP-Kinases Interacting Kinases (MNKs) in Cancer

The mitogen-activated protein kinase (MAPK)-interacting kinases (MNKs) are involved in oncogenic transformation and can promote metastasis and tumor progression. In human cells, there are four MNKs isoforms (MNK1a/b and MNK2a/b), derived from two genes by alternative splicing. These kinases play an important role controlling the expression of specific proteins involved in cell cycle, cell survival and cell motility via eukaryotic initiation factor 4E (eIF4E) regulation, but also through other substrates such as heterogeneous nuclear ribonucleoprotein A1, polypyrimidine tract-binding protein-associated splicing factor and Sprouty 2. In this review, we provide an overview of the role of MNK in human cancers, describing the studies conducted to date to elucidate the mechanism involved in the action of MNKs, as well as the development of MNK inhibitors in different hematological cancers and solid tumors.

ERK is a Pivotal Player of Chemo-Immune-Resistance in Cancer

The extracellular signal-related kinases (ERKs) act as pleiotropic molecules in tumors, where they activate pro-survival pathways leading to cell proliferation and migration, as well as modulate apoptosis, differentiation, and senescence. Given its central role as sensor of extracellular signals, ERK transduction system is widely exploited by cancer cells subjected to environmental stresses, such as chemotherapy and anti-tumor activity of the host immune system. Aggressive tumors have a tremendous ability to adapt and survive in stressing and unfavorable conditions. The simultaneous resistance to chemotherapy and immune system responses is common, and ERK signaling plays a key role in both types of resistance. In this review, we dissect the main ERK-dependent mechanisms and feedback circuitries that simultaneously determine chemoresistance and immune-resistance/immune-escape in cancer cells. We discuss the pros and cons of targeting ERK signaling to induce chemo-immune-sensitization in refractory tumors.

MNK1/NODAL Signaling Promotes Invasive Progression of Breast Ductal Carcinoma In Situ

The mechanisms by which breast cancers progress from relatively indolent ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC) are not well understood. However, this process is critical to the acquisition of metastatic potential. MAPK-interacting serine/threonine-protein kinase 1 (MNK1) signaling can promote cell invasion. NODAL, a morphogen essential for embryogenic patterning, is often reexpressed in breast cancer. Here we describe a MNK1/NODAL signaling axis that promotes DCIS progression to IDC. We generated MNK1 knockout (KO) or constitutively active MNK1 (caMNK1)-expressing human MCF-10A-derived DCIS cell lines, which were orthotopically injected into the mammary glands of mice. Loss of MNK1 repressed NODAL expression, inhibited DCIS to IDC conversion, and decreased tumor relapse and metastasis. Conversely, caMNK1 induced NODAL expression and promoted IDC. The MNK1/NODAL axis promoted cancer stem cell properties and invasion in vitro. The MNK1/2 inhibitor SEL201 blocked DCIS progression to invasive disease in vivo. In clinical samples, IDC and DCIS with microinvasion expressed higher levels of phospho-MNK1 and NODAL versus low-grade (invasion-free) DCIS. Cumulatively, our data support further development of MNK1 inhibitors as therapeutics for preventing invasive disease. SIGNIFICANCE: These findings provide new mechanistic insight into progression of ductal carcinoma and support clinical application of MNK1 inhibitors to delay progression of indolent ductal carcinoma in situ to invasive ductal carcinoma.

Targeting eIF4E signaling with ribavirin as a sensitizing strategy for ovarian cancer

The essential roles of eukaryotic translation initiation factor 4E (eIF4E) have been shown in various cancers, including ovarian cancer. In this work, we demonstrate that eIF4E inhibition in ovarian cancer can be achieved by ribavirin, a FDA-approved antiviral drug. We show that ribavirin at clinically relevant doses significantly inhibits growth and survival in multiple ovarian cancer cell lines, regardless of morphological and molecular subtypes. Mechanistically, ribavirin suppresses Akt/mTOR and eIF4E/p70S6K signaling pathways in ovarian cancer cells. We confirm that eIF4E is the critical molecular target of ribavirin, and furthermore that this is dependent on phosphorylation at S209. Notably, using both in vitro cell culture system and in vivo xenograft mouse model, we show that the combination of ribavirin with cisplatin (standard of care for patients with ovarian cancer) results in significantly greater efficacy than cisplatin alone in ovarian cancer. Interestingly, the sensitivity to ribavirin varies among a panel of ovarian cancer cell lines, mostly likely due to their differential expression level of eIF4E and dependency to eIF4E inhibition. The differential expression level is further observed in ovarian cancer tissues, with the higher level of eIF4E in the majority of ovarian cancer tissues compared to normal ovary tissues. Our work suggests that eIF4E expression varies among ovarian cancer. Additionally, ribavirin is a useful addition to ovarian cancer treatment, particularly to those with high dependency on eIF4E.

Clinically relevant concentration of anti-viral drug ribavirin selectively targets pediatric osteosarcoma and increases chemosensitivity

Ribavirin is an anti-viral drug but has recently gained attention as a potential candidate for cancer treatment. In line with these efforts, our work is the first to demonstrate that ribavirin, at clinically relevant concentration, selectively targets pediatric osteosarcoma and increases chemosensitivity. Using preclinical osteosarcoma cell and xenograft models, we found that ribavirin is active against osteosarcoma bulk and subpopulations with highly proliferative and invasive properties via inhibiting growth, inducing apoptosis and suppressing colony formation. At the same concentrations, ribavirin either did not or affected human normal osteoblastic cell and fibroblast cells in a less extent than osteosarcoma cells. Notably, the combination of ribavirin with doxorubicin resulted in greater efficacy than single drug alone. The combination completely arrested the osteosarcoma growth in vivo throughout the whole duration of drug treatment. We further showed that ribavirin acted on osteosarcoma largely via targeting eIF4E. In addition to eIF4E, ribavirin also modulated phosphorylation of Erk and expression of EZH2 and Snail without affecting Akt and mTOR. Lastly, we found that eIF4E expression and phosphorylation were elevated in osteosarcoma compared to normal cells, which might explain the selective anti-osteosarcoma activity of ribavirin. eIF4E depletion mimics the inhibitory effects of ribavirin, further confirm that eIF4E is the essential target of ribavirin in osteosarcoma. Our work provides fundamental evidence of repurposing ribavirin for the treatment of osteosarcoma. Our findings also highlight the therapeutic value of inhibiting eIF4E in osteosarcoma.

Induction of MNK Kinase-dependent eIF4E Phosphorylation by Inhibitors Targeting BET Proteins Limits Efficacy of BET Inhibitors

BET inhibitors (BETi), which target transcription of key oncogenic genes, are currently being evaluated in early-phase clinical trials. However, because BETis show limited single-agent activity, there is increasing interest in identifying signaling pathways to enhance the efficacy of BETis. Here, we demonstrate increased MNK kinase-dependent eIF4E phosphorylation following treatment with BETis, indicating activation of a prosurvival feedback mechanism in response to BETis. BET PROTACs, which promote degradation of BET proteins, also induced eIF4E phosphorylation in cancer cells. Mechanistically, we show that the effect of BETis on MNK-eIF4E phosphorylation was mediated by p38 MAPKs. We also show that BETis suppressed RacGAP1 to induce Rac signaling-mediated eIF4E phosphorylation. Significantly, MNK inhibitors and MNK1/2 knockdown enhanced the efficacy of BETis in suppressing proliferation of cancer cells in vitro and in a syngeneic mouse model. Together, these results demonstrate a novel prosurvival feedback signaling induced by BETis, providing a mechanistic rationale for combination therapy with BET and MNK inhibitors for synergistic inhibition of cancer cells.

Genetic and pharmacological inhibition of eIF4E effectively targets esophageal cancer cells and augments 5-FU's efficacy

Background

Aberrant activation of eIF4E is critically involved in the progression and chemoresistance of various cancers. Elevated expression of eIF4E has also been documented in human cancerous esophageal tissues. However, the role of eIF4E in esophageal cancer is unclear.

Methods

We analysed the levels of eIF4E expression and eIF4E function in a number of normal and cancerous esophageal cancer cell lines, and studied its underlying mechanism.

Results

We observed that eIF4E expression varies in different esophageal cancer cell lines but was significantly elevated in all tested esophageal cell lines as compared to the control cell lines. We demonstrated that eIF4E inhibition via genetic and pharmacological approaches inhibits cancer cell growth and survival. This inhibition also augments 5-flurouracil's (5-FU's) efficacy as demonstrated with both the in vitro esophageal cancer culture system and our in vivo xenograft mouse model. Of note, the sensitivity of esophageal cancer cells to ribavirin or eIF4E knockdown correlates well with the expression levels of eIF4E, demonstrating that esophageal cells with higher eIF4E expression are more sensitive to eIF4E inhibition. We further confirmed that the mechanism of action of ribavirin on esophageal cancer cells was through suppressing the Akt/mTOR/eIF4E and eIF4E-regulated pathways.

Conclusions

To our knowledge, our work is the first to demonstrate the multiple roles of eIF4E in esophageal cancer. eIF4E was shown to promote cancer cell growth and survival, and protected the cells from chemotherapy. Our work also demonstrated that ribavirin is an attractive candidate for the treatment of esophageal cancer.

MAP Kinase-Interacting Kinase 1 Promotes Proliferation and Invasion of Hepatocellular Carcinoma and Is an Unfavorable Prognostic Biomarker

Background

Hepatocellular carcinoma (HCC) accounts for one of the most prevalent tumor types in the world. The MAP kinase-interacting kinase 1 (MNK1) functions downstream of MAP kinases such as p38 and ERK, and its potential role in cancer development is being uncovered. The aim of this study was to investigate the expression and function of MNK1 in HCC.

Material/Methods

Immunohistochemical staining and quantitative PCR were performed to explore the expression of MNK1 in both HCC tissues and adjacent normal liver tissues. Chi-square test, univariate analysis, and multivariate analysis were conducted to statistically evaluate clinical significance of MNK1 in HCC. Proliferation, migration, and invasion capacities of HCC cells were assessed after overexpressing or silencing MNK1.

Results

Both the RNA and protein levels of MNK1 were upregulated in HCC tissues compared to normal liver tissues. High expression of MNK1 was correlated with advanced tumor stage and poor overall survival. Moreover, MNK1 was identified as a novel independent prognostic factor for HCC patients. Cellular studies showed that MNK1 can enhance the proliferation, migration, and invasion capacities of HCC cells, thereby promoting tumor progression.

Conclusions

High expression of MNK1 is frequent in HCC tissues, which promotes tumor proliferation and invasion, and is correlated with a poor overall survival. Targeting MNK1 may be a novel direction for the drug development of HCC therapy.

Enhanced Chemotherapeutic Efficacy of Paclitaxel Nanoparticles Co-delivered with MicroRNA-7 by Inhibiting Paclitaxel-Induced EGFR/ERK pathway Activation for Ovarian Cancer Therapy

Chemotherapy-induced activation of cell survival pathways leads to drug resistance. MicroRNAs (miRNAs) post-transcriptionally regulate gene expression in many biological pathways. Paclitaxel (PTX) is one of the first-line chemotherapy drugs for ovarian cancer, and it induces the activation of the epidermal growth factor receptor (EGFR)/extracellular signal-regulated kinase (ERK) pathway that leads to tumor cell proliferation, survival, invasion, and drug resistance. MicroRNA-7 (miR-7) has the ability to suppress the EGFR/ERK pathway. To sensitize chemotherapy, we developed monomethoxy(poly(ethylene glycol))-poly(d,l-lactide- co-glycolide)-poly(l-lysine) nanoparticles for the simultaneous co-delivery of PTX and miR-7. The resulting PTX/miR-7 nanoparticles (P/MNPs) protect miRNA from degradation, possess a sequential and controlled release of drugs, improve the transfection efficiency of miRNA, decrease the half-maximal inhibitory concentration of PTX, and increase the apoptosis of ovarian cancer cells. The chemotherapeutic efficacy of PTX is prominently enhanced in vitro and in vivo via the inhibition of PTX-induced EGFR/ERK pathway activation by miR-7. Our studies in P/MNPs reveal a novel paradigm for a dual-drug-delivery system of chemotherapeutics and gene therapy in treating cancers.