Ovarian cancer: Stat3, RhoA and IGF-IR as therapeutic targets

Advance in vasculogenic mimicry in ovarian cancer (Review)

Ovarian cancer (OC) is a common and highly prevalent malignant tumor in women, associated with a high mortality rate, easy recurrence and easy metastasis, which is predominantly at an advanced stage when detected in patients. This renders the cancer more difficult to treat, and consequently it is also associated with a low survival rate, being the malignancy with the highest mortality rate among the various gynecological tumors. As an important factor affecting the development and metastasis of OC, understanding the underlying mechanism(s) through which it is formed and developed is crucial in terms of its treatment. At present, the therapeutic methods of angiogenic mimicry for OC remain in the preliminary stages of exploration and have not been applied in actual clinical practice. In the present review, various signaling pathways and factors affecting angiogenic mimicry in OC were described, and the chemical synthetic drugs, natural compound extracts, small-molecule protein antibodies and their associated targets, and so on, that target angiogenic mimicry in the treatment of OC, were discussed. The purpose of this review was to provide new research ideas and potential theoretical support for the discovery of novel therapeutic targets for OC that may be applied in the clinic, with the aim of effectively reducing its metastasis and recurrence rates.

Hormone-Glutamine Metabolism: A Critical Regulatory Axis in Endocrine-Related Cancers

The endocrine-related cancers and hormones are undoubtedly highly interconnected. How hormones support or repress tumor induction and progression has been extensively profiled. Furthermore, advances in understanding the role of glutamine metabolism in mediating tumorigenesis and development, coupled with these in-depth studies on hormone (e.g., estrogen, progesterone, androgen, prostaglandin, thyroid hormone, and insulin) regulation of glutamine metabolism, have led us to think about the relationship between these three factors, which remains to be elucidated. Accordingly, in this review, we present an updated overview of glutamine metabolism traits and its influence on endocrine oncology, as well as its upstream hormonal regulation. More importantly, this hormone/glutamine metabolism axis may help in the discovery of novel therapeutic strategies for endocrine-related cancer.

Immunotherapy checkpoints in ovarian cancer vasculogenic mimicry: Tumor immune microenvironments, and drugs

Vasculogenic mimicry (VM), a vessel-like structure independent of endothelial cells, commonly exists in solid tumors which requires blood vessels to grow. As a special source of blood supply for tumor progression to a more aggressive state, VM has been observed in a variety of human malignant tumors and is tightly associated with tumor proliferation, invasion, metastasis, and poor patient prognosis. So far, various factors, including immune cells and cytokines, were reported to regulate ovarian cancer progression by influencing VM formation. Herein, we review the mechanisms that regulate VM formation in ovarian cancer and the effect of cells, cytokines, and signaling molecules in the tumor microenvironment on VM formation, Furthermore, we summarize the current clinical application of drugs targeting VM formation.

Loss of ZIP facilitates JAK2-STAT3 activation in tamoxifen-resistant breast cancer

Tamoxifen is beneficial in treating estrogen receptor–positive breast cancer, but resistance to this treatment eventually ensues. A method to identify mechanisms of tamoxifen resistance identified the histone deacetylase ZIP, leading to the finding that increased expression of the tyrosine kinase JAK2 is one important factor. As a result of this discovery, it may be possible to use an inhibitor of JAK2 to block the aberrant activation of STAT3 caused by ZIP deficiency to help overcome or prevent tamoxifen resistance.

Tamoxifen, a widely used modulator of the estrogen receptor (ER), targets ER-positive breast cancer preferentially. We used a powerful validation-based insertion mutagenesis method to find that expression of a dominant-negative, truncated form of the histone deacetylase ZIP led to resistance to tamoxifen. Consistently, increased expression of full-length ZIP gives the opposite phenotype, inhibiting the expression of genes whose products mediate resistance. An important example is JAK2. By binding to two specific sequences in the promoter, ZIP suppresses JAK2 expression. Increased expression and activation of JAK2 when ZIP is inhibited lead to increased STAT3 phosphorylation and increased resistance to tamoxifen, both in cell culture experiments and in a mouse xenograft model. Furthermore, data from human tumors are consistent with the conclusion that decreased expression of ZIP leads to resistance to tamoxifen in ER-positive breast cancer.

Activation of STAT3 and STAT5 Signaling in Epithelial Ovarian Cancer Progression: Mechanism and Therapeutic Opportunity

Epithelial ovarian cancer (EOC) is the most lethal of all gynecologic malignancies. Despite advances in surgical and chemotherapeutic options, most patients with advanced EOC have a relapse within three years of diagnosis. Unfortunately, recurrent disease is generally not curable. Recent advances in maintenance therapy with anti-angiogenic agents or Poly ADP-ribose polymerase (PARP) inhibitors provided a substantial benefit concerning progression-free survival among certain women with advanced EOC. However, effective treatment options remain limited in most recurrent cases. Therefore, validated novel molecular therapeutic targets remain urgently needed in the management of EOC. Signal transducer and activator of transcription-3 (STAT3) and STAT5 are aberrantly activated through tyrosine phosphorylation in a wide variety of cancer types, including EOC. Extrinsic tumor microenvironmental factors in EOC, such as inflammatory cytokines, growth factors, hormones, and oxidative stress, can activate STAT3 and STAT5 through different mechanisms. Persistently activated STAT3 and, to some extent, STAT5 increase EOC tumor cell proliferation, survival, self-renewal, angiogenesis, metastasis, and chemoresistance while suppressing anti-tumor immunity. By doing so, the STAT3 and STAT5 activation in EOC controls properties of both tumor cells and their microenvironment, driving multiple distinct functions during EOC progression. Clinically, increasing evidence indicates that the activation of the STAT3/STAT5 pathway has significant correlation with reduced survival of recurrent EOC, suggesting the importance of STAT3/STAT5 as potential therapeutic targets for cancer therapy. This review summarizes the distinct role of STAT3 and STAT5 activities in the progression of EOC and discusses the emerging therapies specifically targeting STAT3 and STAT5 signaling in this disease setting.

Investigational IGF1R inhibitors in early stage clinical trials for cancer therapy

Introduction: The insulin-like growth factors (IGFs) are a family of secreted peptide hormones with important roles in different cellular and organism functions. The biological activities of the IGFs are mediated by the IGF1 receptor (IGF1R), a cell surface, tyrosine kinase-containing heterotetramer that is linked to numerous cytoplasmic signaling cascades. The IGF1R displays potent antiapoptotic, pro-survival capacities and plays a key role in malignant transformation. Research has identified the IGF1R as a candidate therapeutic target in cancer.Areas covered: We offer a synopsis of ongoing efforts to target the IGF axis for therapeutic purposes. Our review includes a digest of early experimental work that led to the identification of IGF1R as a candidate therapeutic target in oncology.Expert opinion: Targeting of the IGF axis has yielded disappointing results in phase III trials, but it is important to learn from this to improve future trials in a rational manner. The potential of anti-IGF1R antibodies and small molecular weight inhibitors, alone or in combination with chemotherapy or other biological agents, should be investigated further in randomized studies. Moreover, the implementation of predictive biomarkers for patient selection will improve the outcome of future trials. Emerging personalized medicine could have a major impact on IGF1R targeting.

Mechanisms of Vasculogenic Mimicry in Ovarian Cancer

Solid tumors carry out the formation of new vessels providing blood supply for growth, tumor maintenance, and metastasis. Several processes take place during tumor vascularization. In angiogenesis, new vessels are derived from endothelial cells of pre-existing vessels; while in vasculogenesis, new vessels are formed de novo from endothelial progenitor cells, creating an abnormal, immature, and disorganized vascular network. Moreover, highly aggressive tumor cells form structures similar to vessels, providing a pathway for perfusion; this process is named vasculogenic mimicry (VM), where vessel-like channels mimic the function of vessels and transport plasma and blood cells. VM is developed by numerous types of aggressive tumors, including ovarian carcinoma which is the second most common cause of death among gynecological cancers. VM has been associated with poor patient outcome and survival in ovarian cancer, although the involved mechanisms are still under investigation. Several signaling molecules have an important role in VM in ovarian cancer, by regulating the expression of genes related to vascular, embryogenic, and hypoxic signaling pathways. In this review, we provide an overview of the current knowledge of the signaling molecules involved in the promotion and regulation of VM in ovarian cancer. The clinical implications and the potential benefit of identification and targeting of VM related molecules for ovarian cancer treatment are also discussed.

MicroRNA-519a inhibits the proliferation and promotes the apoptosis of ovarian cancer cells through targeting signal transducer and activator of transcription 3

Ovarian cancer is a highly prevalent cancer among women. Recent studies have indicated that microRNAs (miRs) may serve important roles in the pathogenesis of ovarian cancer. miR-519a was observed to be downregulated in tissue samples of patients with ovarian cancer; however, its role in ovarian cancer requires further investigation. The aim of the present study was to examine the role of miR-519a in the pathogenesis of ovarian cancer and determine its direct target. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was performed to examine the expression of miR-519a in 20 patients ovarian cancer and 20 normal ovarian tissue samples. Subsequently, SKOV3 cells were cultured and transfected with miR-519a mimics, while MTT and Annexin V assays were performed to investigate the role of miR-519a in the proliferation and apoptosis of SKOV3 cells. In addition, RT-qPCR and western blotting were used to determine the expression levels of miR-519a, signal transducer and activator of transcription 3 (STAT3), myeloid cell leukemia 1 (Mcl-1) and B-cell lymphoma-extra large (Bcl-xl) in untransfected and miR-519a mimic-transfected SKOV3 cells. Dual-luciferase reporter assay was also performed to confirm whether STAT3 was a direct target of miR-519a. The results revealed that miR-519a was significantly downregulated in tissue samples of patients with ovarian cancer as compared with the normal ovarian tissues. Furthermore, transient overexpression of miR-519a inhibited the proliferation and promoted the apoptosis of SKOV3 cells, as well as decreased the mRNA and protein expression levels of STAT3, Mcl-1 and Bcl-xl. Finally, dual-luciferase reporter assay confirmed that STAT3 was a direct target of miR-519a. In conclusion, the present study proved for the first time that miR-519a functions as a tumor suppressor by targeting STAT3 in ovarian cancer, suggesting that miR-519a may be a potential biomarker for the diagnosis and treatment of ovarian cancer.

Physapubescin B inhibits tumorgenesis and circumvents taxol resistance of ovarian cancer cells through STAT3 signaling

Ovarian cancer is the most lethal gynaecological malignancy. Recurrence and subsequent resistance to chemotherapy have become major obstacles to treating these diseases. In the present study, we showed that a natural withanolide isolated from the plant Physalis pubescens L. (Solanaceae), Physapubescin B, exhibited potent anti-tumor activity against ovarian cancer cells. Physapubescin B promoted apoptosis, induced cell-cycle arrest and inhibited invasion of ES-2 and A2780 cells. Physapubescin B treatment also resulted in suppression of the transcriptional activity of STAT3, an oncogenic transcription factor activated in many human malignancies including ovarian cancer, through disturbing the dimerization of STAT3, and thereby inhibited the nuclear translocation of Tyr705/Ser727-phosphorylated STAT3. The IL-6-stimulated activation of STAT3 and its downstream genes Cyclin D1, survivin, and Bcl-xL was also repressed by Physapubescin B. Furthermore, Physapubescin B sensitizes A2780 cells to taxol-induced cell growth inhibition in vitro. These findings strongly suggest that Physapubescin B has potential antitumor activity and may circumvent taxol resistance in human ovarian cancer cells through inhibition of aberrant activation of STAT3.

Prediction of therapy response in ovarian cancer: Where are we now?

Therapy resistance is a major challenge in the management of ovarian cancer (OC). Advances in detection and new technology validation have led to the emergence of biomarkers that can predict responses to available therapies. It is important to identify predictive biomarkers to select resistant and sensitive patients in order to reduce important toxicities, to reduce costs and to increase survival. The discovery of predictive and prognostic biomarkers for monitoring therapy is a developing field and provides promising perspectives in the era of personalized medicine. This review article will discuss the biology of OC with a focus on targetable pathways; current therapies; mechanisms of resistance; predictive biomarkers for chemotherapy, antiangiogenic and DNA-targeted therapies, and optimal cytoreductive surgery; and the emergence of liquid biopsy using recent studies from the Medline database and ClinicalTrials.gov.

Evaluation of nitric oxide donors impact on cisplatin resistance in various ovarian cancer cell lines

Ovarian cancer chemoresistance, both intrinsic and acquired, is the main obstacle in improving the outcome of anticancer therapies. Therefore the development of new treatment strategies, including the use of new compounds that can support the standard therapeutics is required. Among many candidates, nitric oxide (NO) donors, agents with multivalent targeted activities in cancer cells, are worth considering. The aim of this study was evaluation of SPER/NO and DETA/NO ability to enhance cisplatin cytotoxicity against different ovarian cancer cell lines. Obtained data indicate that NO donors action varies between different cancer cell lines and is strongest in low aggressive and cisplatin sensitive cells. While statistically significant, the enhancement of cisplatin cytotoxicity by NO donors is of low magnitude. The rise in the percentage of late apoptotic/necrotic ovarian cancer cells may suggest that NO donors enhancement action might be based on the cellular ATP depletion. Nevertheless, no significant impact of the NO donors, cisplatin or their combination on the expressions of ABCB1, BIRC5 and PTEN genes has been found. Although our data puts the therapeutical potential of NO donors to aid cisplatin action in question it may also point out at the further approach to utilize these compounds in therapies.

Nitric oxide donors reduce the invasion ability of ovarian cancer cells in vitro

The most important factors involved in tumor metastasis and angiogenesis are metalloproteinases (MMPs), vascular endothelial growth factor, and multifunctional transforming growth factor β1. These factors are responsible for extracellular matrix degradation, induction of vascular permeability, and enhancement of tumor cells' invasion and metastasis. Elevated expression and secretion of the above-mentioned factors are correlated with the higher aggressiveness of tumors and low patient survival for example, patients with ovarian cancer. Therefore, regulation of the expression, secretion, and activity of these factors is still considered a potent target for therapeutic intervention in cancer patients. Nitric oxide (NO) donors belong to the class of agents with multivalent targeted activities in cancer cells and are considered potential anticancer therapeutics. Our studies have shown that NO donors such as spermine/NO and diethylenetriamine/NO decrease the secretion of vascular endothelial growth factor-A from the OVCAR-3 ovarian cancer cell line, but not from the SK-OV-3 ovarian cancer cell line. The release of MMP-2 from both cell lines was reduced in a soluble guanylate cyclase-dependent manner by spermine/NO and diethylenetriamine/NO. Nevertheless, MMP-2 activity was only affected in SK-OV-3 cells. Both NO donors reduced the transmigration of the ovarian cancer cell lines. We did not observe any significant effect of spermine/NO and diethylenetriamine/NO on mRNA expression of the tested aggressiveness factors. In conclusion, our data indicated that NO donors reduced the metastatic potential of ovarian cancer cells, but its impact is rather low and requires high concentrations of donors. Moreover, both the tested cell lines differed in the susceptibility to NO donors.

miR-494 suppresses tumor growth of epithelial ovarian carcinoma by targeting IGF1R

A growing body of evidence suggests that microRNA-494 (miR-494) could act as tumor-suppressive or oncogenic microRNAs (miRNAs) in different types of tumors. However, the biological roles and underlying mechanisms of miR-494 remain unknown in human epithelial ovarian carcinoma (EOC). Therefore, the aims of this study were to investigate the miR-494 expression and the significance of its clinical diagnosis in patients suffering EOC and to analyze its role and underlying molecular mechanism on the carcinogenesis of EOC. Here, we found that miR-494 was significantly decreased in EOC cell lines and tissues and its expression was negatively correlated with advanced International Federation of Gynecology and Obstetrics (FIGO) stage, high pathological grade, and lymph node metastasis (all P < 0.01). Functional studies showed that overexpression of miR-494 in EOC cells could remarkably inhibit proliferation, colony formation, migration, and invasion and induce cell apoptosis, G0/G1 phase arrest. An in vivo analysis revealed that the overexpression of miR-494 suppressed tumor growth in a nude mouse xenograft model system. Bioinformatic assay and dual-luciferase assay confirmed that insulin-like growth factor 1 receptor (IGF1R) was as a direct target of miR-494 in EOC cells. Western blot assay showed that overexpression of miR-494 inhibited IGF1R expression and its downstream signal protein expression. In addition, downregulation of IGF1R has similar effects with miR-494 overexpression on EOC cells and overexpression of IGF1R effectively rescued the inhibition of overexpressed miR-494 in EOC cells. These data suggested that miR-494 functions as a tumor suppressor in EOC by targeting IGF1R.

Network-based survival-associated module biomarker and its crosstalk with cell death genes in ovarian cancer

Ovarian cancer remains a dismal disease with diagnosing in the late, metastatic stages, therefore, there is a growing realization of the critical need to develop effective biomarkers for understanding underlying mechanisms. Although existing evidences demonstrate the important role of the single genetic abnormality in pathogenesis, the perturbations of interactors in the complex network are often ignored. Moreover, ovarian cancer diagnosis and treatment still exist a large gap that need to be bridged. In this work, we adopted a network-based survival-associated approach to capture a 12-gene network module based on differential co-expression PPI network in the advanced-stage, high-grade ovarian serous cystadenocarcinoma. Then, regulatory genes (protein-coding genes and non-coding genes) direct interacting with the module were found to be significantly overlapped with cell death genes. More importantly, these overlapping genes tightly clustered together pointing to the module, deciphering the crosstalk between network-based survival-associated module and cell death in ovarian cancer.

Knockdown of RhoA expression alters ovarian cancer biological behavior in vitro and in nude mice

RhoA regulates cell proliferation, migration, angiogenesis and gene expression. Altered RhoA activity contributes to cancer progression. The present study investigated the effects of RhoA knockdown on the regulation of ovarian cancer biological behavior in vitro and in nude mice. The expression of RhoA was knocked down using a lentivirus carrying RhoA short hairpin RNA (shRNA) in ovarian cancer cells and was confirmed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. The altered ovarian cancer biological behaviors were assayed by cell viability, terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling (TUNEL), migration, invasion, and nude mice tumorigenicity assays, while the altered gene expression was detected by RT-qPCR and western blot analysis. The results showed that lentivirus-carrying RhoA shRNA significantly suppressed RhoA expression in ovarian cancer cells, which suppressed tumor cell viability, migration, invasion and adhesion in vitro. RhoA silencing also inhibited the tumorigenicity of ovarian cancer cells in nude mice, which was characterized by the suppression of tumor xenograft formation and growth and induction of tumor cell apoptosis. The results of the present study demonstrated that knockdown of RhoA expression had a significant antitumor effect on ovarian cancer cells in vitro and in nude mice, suggesting that RhoA may be a target for the development of a novel therapeutic strategy in the control of ovarian cancer.

Atypical protein kinase C zeta: potential player in cell survival and cell migration of ovarian cancer

Ovarian cancer is one of the most aggressive gynaecological cancers, thus understanding the different biological pathways involved in ovarian cancer progression is important in identifying potential therapeutic targets for the disease. The aim of this study was to investigate the potential roles of Protein Kinase C Zeta (PRKCZ) in ovarian cancer. The atypical protein kinase C isoform, PRKCZ, is involved in the control of various signalling processes including cell proliferation, cell survival, and cell motility, all of which are important for cancer development and progression. Herein, we observe a significant increase in cell survival upon PRKCZ over-expression in SKOV3 ovarian cancer cells; additionally, when the cells are treated with small interference RNA (siRNA) targeting PRKCZ, the motility of SKOV3 cells decreased. Furthermore, we demonstrate that over-expression of PRKCZ results in gene and/or protein expression alterations of insulin-like growth factor 1 receptor (IGF1R) and integrin beta 3 (ITGB3) in SKOV3 and OVCAR3 cells. Collectively, our study describes PRKCZ as a potential regulatory component of the IGF1R and ITGB3 pathways and suggests that it may play critical roles in ovarian tumourigenesis.

A novel neutralizing antibody targeting pregnancy-associated plasma protein-a inhibits ovarian cancer growth and ascites accumulation in patient mouse tumorgrafts

The majority of ovarian cancer patients acquire resistance to standard platinum chemotherapy and novel therapies to reduce tumor burden and ascites accumulation are needed. Pregnancy-associated plasma protein-A (PAPP-A) plays a key role in promoting insulin-like growth factor (IGF) pathway activity, which directly correlates to ovarian cancer cell transformation, growth, and invasiveness. Herein, we evaluate PAPP-A expression in tumors and ascites of women with ovarian cancer, and determine the antitumor efficacy of a neutralizing monoclonal PAPP-A antibody (mAb-PA) in ovarian cancer using primary patient ovarian tumorgrafts ("Ovatars"). PAPP-A mRNA expression in patient ovarian tumors correlated with poor outcome and was validated as a prognostic surrogate in Ovatar tumors. Following confirmation of mAb-PA bioavailability and target efficacy in vivo, the antitumor efficacy of mAb-PA in multiple Ovatar tumor models was examined and the response was found to depend on PAPP-A expression. Strikingly, the addition of mAb-PA to standard platinum chemotherapy effectively sensitized platinum-resistant Ovatar tumors. PAPP-A protein in ascites was also assessed in a large cohort of patients and very high levels were evident across the entire sample set. Therefore, we evaluated targeted PAPP-A inhibition as a novel approach to managing ovarian ascites, and found that mAb-PA inhibited the development, attenuated the progression, and induced the regression of Ovatar ascites. Together, these data indicate PAPP-A as a potential palliative and adjunct therapeutic target for women with ovarian cancer.

The role of Rho GTPase in cell stiffness and cisplatin resistance in ovarian cancer cells

Changes in cell stiffness (Young's modulus, E), as measured via Atomic Force Microscopy (AFM), is a newly recognized characteristic of cancer cells and may play a role in platinum drug resistance of ovarian cancers. We previously showed that, compared to their syngeneic cisplatin-sensitive counterpart, cisplatin-resistant ovarian cancer cells are stiffer, and this cell stiffness was dependent on actin polymerization and presence of stress fibers. Here, we measured the correlation between Young's modulus (via AFM measurements on live, non-apoptotic cells in physiological buffer) and cisplatin-sensitivity (IC50 as determined via the XTT cell viability assay) in a panel of nine ovarian cancer cell lines representing a range of cisplatin sensitivities. We found that cisplatin-sensitive cells had a lower Young's modulus, compared to cisplatin-resistant cells and resistant cells had a cytoskeleton composed of long actin stress fibers. As Rho GTPase mediates stress fiber formation, we examined the role of Rho GTPase in cell stiffness and platinum resistance. Rho inhibition decreased cell stiffness in cisplatin-resistant CP70 cells and increased their cisplatin sensitivity while Rho activation increased cell stiffness in cisplatin-sensitive A2780 cells and decreased their cisplatin sensitivity. Based on changes in cell stiffness, IC50 and cellular actin stress fiber organization in CP70 and A2780 cells, our findings reveal a direct role of Rho mediated actin remodeling mechanism in cisplatin resistance of ovarian cancer cells. These findings suggest the potential applicability of cell mechanical phenotyping as a model for determining sensitivity of ovarian cancer cells that could have major implications in ovarian cancer diagnosis and personalized medicine.

MiR-124 represses vasculogenic mimicry and cell motility by targeting amotL1 in cervical cancer cells

miRNAs have extensive functions in differentiation, metabolism, programmed cell death, and tumor metastasis by post-transcriptional regulation. Vasculogenic mimicry is an important pathway in tumor metastasis. Many factors can regulate vasculogenic mimicry, including miRNAs. In previous studies, miR-124 was found to repress proliferation and metastasis in different types of cancers, but whether it functions in cervical cancer remained unknown. Here, we demonstrate that miR-124 can repress vasculogenic mimicry, migration and invasion in HeLa and C33A cells in vitro. Furthermore, we reveal that the effect of miR-124 on vasculogenic mimicry, migration and invasion results from its interaction with AmotL1. MiR-124 regulates AmotL1 negatively by targeting its 3'untranslated region (3'UTR). We found that miR-124 can repress the EMT process. Together, these results improve our understanding of the function of miR-124 in tumor metastasis and will help to provide new potential target sites for cervical cancer treatment.

Metabolic shifts toward glutamine regulate tumor growth, invasion and bioenergetics in ovarian cancer

Glutamine can play a critical role in cellular growth in multiple cancers. Glutamine‐addicted cancer cells are dependent on glutamine for viability, and their metabolism is reprogrammed for glutamine utilization through the tricarboxylic acid (TCA) cycle. Here, we have uncovered a missing link between cancer invasiveness and glutamine dependence. Using isotope tracer and bioenergetic analysis, we found that low‐invasive ovarian cancer (OVCA) cells are glutamine independent, whereas high‐invasive OVCA cells are markedly glutamine dependent. Consistent with our findings, OVCA patients’ microarray data suggest that glutaminolysis correlates with poor survival. Notably, the ratio of gene expression associated with glutamine anabolism versus catabolism has emerged as a novel biomarker for patient prognosis. Significantly, we found that glutamine regulates the activation of STAT3, a mediator of signaling pathways which regulates cancer hallmarks in invasive OVCA cells. Our findings suggest that a combined approach of targeting high‐invasive OVCA cells by blocking glutamine's entry into the TCA cycle, along with targeting low‐invasive OVCA cells by inhibiting glutamine synthesis and STAT3 may lead to potential therapeutic approaches for treating OVCAs.

Macrophage capping protein CapG is a putative oncogene involved in migration and invasiveness in ovarian carcinoma

The actin binding protein CapG modulates cell motility by interacting with the cytoskeleton. CapG is associated with tumor progression in different nongynecologic tumor entities and overexpression in breast cancer cell lines correlates with a more invasive phenotype in vitro. Here, we report a significant CapG overexpression in 18/47 (38%) of ovarian carcinomas (OC) analyzed by qRealTime-PCR analyses. Functional analyses in OC cell lines through siRNA mediated CapG knockdown and CapG overexpression showed CapG-dependent cell migration and invasiveness. A single nucleotide polymorphism rs6886 inside the CapG gene was identified, affecting a CapG phosphorylation site and thus potentially modifying CapG function. The minor allele frequency (MAF) of SNP rs6886 (c.1004A/G) was higher and the homozygous (A/A, His335) genotype was significantly more prevalent in patients with fallopian tube carcinomas (50%) as in controls (10%). With OC being one of the most lethal cancer diseases, the detection of novel biomarkers such as CapG could reveal new diagnostic and therapeutic targets. Moreover, in-depth analyses of SNP rs6886 related to FTC and OC will contribute to a better understanding of carcinogenesis and progression of OC.

Improvement of human keratinocyte migration by a redox active bioelectric dressing

Exogenous application of an electric field can direct cell migration and improve wound healing; however clinical application of the therapy remains elusive due to lack of a suitable device and hence, limitations in understanding the molecular mechanisms. Here we report on a novel FDA approved redox-active Ag/Zn bioelectric dressing (BED) which generates electric fields. To develop a mechanistic understanding of how the BED may potentially influence wound re-epithelialization, we direct emphasis on understanding the influence of BED on human keratinocyte cell migration. Mapping of the electrical field generated by BED led to the observation that BED increases keratinocyte migration by three mechanisms: (i) generating hydrogen peroxide, known to be a potent driver of redox signaling, (ii) phosphorylation of redox-sensitive IGF1R directly implicated in cell migration, and (iii) reduction of protein thiols and increase in integrin_αv expression, both of which are known to be drivers of cell migration. BED also increased keratinocyte mitochondrial membrane potential consistent with its ability to fuel an energy demanding migration process. Electric fields generated by a Ag/Zn BED can cross-talk with keratinocytes via redox-dependent processes improving keratinocyte migration, a critical event in wound re-epithelialization.

Nitric oxide donors: spermine/NO and diethylenetriamine/NO induce ovarian cancer cell death and affect STAT3 and AKT signaling proteins

The important features of cancer cells are uncontrolled growth and proliferation, as well as the ability to metastasis. These features depend mainly on the constant overexpression and activity of various cell signaling proteins, such as signal transducer and activator of transcription 3 (STAT3) and serine-threonine protein kinase AKT proteins. Nitric oxide (NO) has the potential of being anti-tumoral agent, however the exact character of anti-tumoral action of NO is still a matter of debate. In our research we used two NO donors, belonging to NONOates family, with different half-life times: spermine nitric oxide complex hydrate (SPER/NO t1/2=39min) and diethylenetriamine nitric oxide adduct (DETA/NO, t1/2=20h). We evaluated the cytotoxic effect of aforementioned NO donors on SK-OV-3 and OVCAR-3 ovarian cancer cell lines, as well as their effect on posttranslational modification of STAT3 and AKT proteins in these cells. We found that both NO donors present cytotoxic activity on the cancer cell lines, mainly through the induction of apoptosis. What is more, at the high concentration and longer exposure time they were also capable of inducing late apoptosis/necrosis. Both NO donors inhibited STAT3 and AKT3 proteins phosphorylation and down regulated their cytosolic levels, with DETA/NO being stronger inhibitor. We suggests, that NO donors have the potential to act as anti-tumoral agent through inhibiting cancer cell signaling and reducing their viability.

Early responses of the STAT3 pathway to platinum drugs are associated with cisplatin resistance in epithelial ovarian cancer

Cisplatin resistance remains one of the major obstacles when treating epithelial ovarian cancer. Because oxaliplatin and nedaplatin are effective against cisplatin-resistant ovarian cancer in clinical trials and signal transducer and activator of transcription 3 (STAT3) is associated with cisplatin resistance, we investigated whether overcoming cisplatin resistance by oxaliplatin and nedaplatin was associated with the STAT3 pathway in ovarian cancer. Alamar blue, clonogenic, and wound healing assays, and Western blot analysis were used to compare the effects of platinum drugs in SKOV-3 cells. At an equitoxic dose, oxaliplatin and nedaplatin exhibited similar inhibitory effects on colony-forming ability and greater inhibition on cell motility than cisplatin in ovarian cancer. Early in the time course of drug administration, cisplatin increased the expression of pSTAT3 (Tyr705), STAT3α, VEGF, survivin, and Bcl-X_L, while oxaliplatin and nedaplatin exhibited the opposite effects, and upregulated pSTAT3 (Ser727) and STAT3β. The STAT3 pathway responded early to platinum drugs associated with cisplatin resistance in epithelial ovarian cancer and provided a rationale for new therapeutic strategies to reverse cisplatin resistance.

Hospicells promote upregulation of the ATP-binding cassette genes by insulin-like growth factor-I via the JAK2/STAT3 signaling pathway in an ovarian cancer cell line

Interaction between tumor cells and their microenvironment has a crucial role in the development, progression and drug resistance of cancer. Our objective was to confirm the role of Hospicells, which are stromal cells from the cancer microenvironment, in drug resistance and tumor cell growth. We demonstrated that soluble factors secreted by Hospicells activate several genes and upregulate the JAK/STAT signaling pathway in ovarian cancer cell lines. Hospicells express all insulin-like growth factor (IGF) family as detected by gene array, RT-PCR, protein array and immunocytochemistry. While focusing attention on the microenvironment, we considered the role of IGF-I in proliferation and survival of ovarian cancer cells. Indeed, IGF-I is a major regulator of different stages of cancer development. We studied the effect of exogenously added IGF-I on the regulation of ATP-binding cassette (ABC) genes (MDR1, MRP1, MRP2, MRP3, MRP5 and BCRP) in the ovarian cancer cell line OVCAR3 and validated the results obtained using the IGF-IR antagonist picropodophyllin. IGF-I regulates the expression of ABC genes in OVCAR3 cells via the PI3-kinase, MEK and JAK2/STAT3 signaling pathways. The OVCAR3 cell line when co-cultured with Hospicells showed a marked degree of drug resistance. The drug resistance observed could be amplified with exogenous IGF-I. Addition of IGF-IR inhibitor, however, reduced the degree of resistance in these exposed cells. Cells that were treated with anticancer drugs and then exposed to IGF-I showed an increase in drug resistance and, thereby, an increase in cell survival. This observation indicates that drug resistance of OVCAR3 cells increases when there is synergy between OVCAR3 cells and Hospicells and it is amplified when IGF-I was exogenously added. In conclusion, inhibition of IGF-IR and targeting of the JAK2/STAT3 signaling pathway can be a target for ovarian cancer therapy.

Targeting IGF-1 signaling pathways in gynecologic malignancies

INTRODUCTION

The signaling pathways of the insulin-like growth factors (IGF) have been implicated in the etiology of a number of epithelial neoplasms including prostate, breast, colon and more recently, gynecologic cancers. The insulin-like growth factor-1 receptor (IGF-1R) is expressed in most transformed cells, where it displays potent anti-apoptotic, cell-survival and potentially, transforming activities. IGF-1R expression and activation are typical hallmarks associated with tumor initiation and progression. Multiple approaches have been used to abrogate IGF-1R signaling for targeted cancer therapy including antibodies and small molecule tyrosine kinase inhibitors. These novel IGF-1R targeting agents have produced significant experimental and clinical results in many cancers and generated considerable optimism in the field of cancer therapy.

AREAS COVERED

The authors will review important research advances regarding the role of the IGF axis in cancer, particularly preclinical and clinical studies in cervical, uterine and ovarian cancers. The significance of tumor expression and circulating levels of the IGF pathway as well as targeting therapies of the IGF axis in the gynecologic cancers will be discussed.

EXPERT OPINION

Accumulating data confirm that the IGF-1R pathway has an important role in gynecologic cancers and in vivo and in vitro studies have shown a significant impact of IGF-1R targeted therapies in these malignancies, mainly ovarian and endometrial cancers. Currently, ongoing preclinical and clinical trials are evaluating the efficacy of IGF-1R targeting. A better understanding of the complex mechanisms underlying the regulation of the IGF system will improve the ability to develop effective treatment modalities for these malignancies.