Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis which drives endothelial cell survival, proliferation, and migration while increasing vascular permeability. Playing an important role in the physiology of normal ovaries, VEGF has also been implicated in the pathogenesis of ovarian cancer. Essentially by promoting tumor angiogenesis and enhancing vascular permeability, VEGF contributes to the development of peritoneal carcinomatosis associated with malignant ascites formation, the characteristic feature of advanced ovarian cancer at diagnosis. In both experimental and clinical studies, VEGF levels have been inversely correlated with survival. Moreover, VEGF inhibition has been shown to inhibit tumor growth and ascites production and to suppress tumor invasion and metastasis. These findings have laid the basis for the clinical evaluation of agents targeting VEGF signaling pathway in patients with ovarian cancer. In this review, we will focus on VEGF involvement in the pathophysiology of ovarian cancer and its contribution to the disease progression and dissemination.

Angiogenesis is the formation of new blood vessels from the pre-existing vasculature. Besides its role in normal physiology, angiogenesis is significantly involved in many pathological conditions, including inflammation, cardiovascular diseases and cancer. Numerous studies have been undertaken in the area of tumor angiogenesis. It is known that pathological angiogenesis is necessary for tumors to proceed from avascular, dormant stage to vascular, sprouting stage and also contributes to their later invasion and metastasis. Playing a central role in tumor angiogenesis, vascular endothelial growth factor is considered as a key target in therapeutic approaches. This article aims to review the critical role of VEGF in tumor angiogenesis and the importance of VEGF-targeted strategies in cancer treatment.

Sprouty (Spry) proteins, modulators of receptor tyrosine kinase signaling pathways, have been shown to be deregulated in a variety of pathological conditions including cancer. In the present study we investigated the expression of Spry1 and Spry2 isoforms in a panel of human ovarian cancer cell lines in vitro. Our western blot analysis showed nonuniform patterns of Spry expression in the cancer cells, none of which conformed to the pattern observed in the normal ovarian epithelial cells employed as the control. Among the seven cancer cell lines studied, Spry1 was expressed lower in four cell lines and higher in one as compared with the control. As for Spry2, four cell lines showed lower and two exhibited higher expression. Results from RT-PCR assay raised the possibility that Spry protein levels may not necessarily correspond with its expression at mRNA level. Our immunostaining study revealed that Spry2 was predominantly distributed within the whole cytoplasm in vesicular structures whereas Spry1 was found in both the cytoplasm and nucleus. This might provide clues to further investigation of Spry mode of action and/or function. Collectively, our study unveiled the differential expression of Spry1 and Spry2 proteins in various ovarian cancer cell lines.

BackgroundBromelain is a pineapple stem extract with a variety of therapeutic benefits arising from interaction with a number of different biological processes. Several preclinical studies and anecdotal clinical observations have reported the anticancer properties of bromelain. In the present study, we investigated the cytotoxic effects of bromelain in four human cancer cell lines of gastrointestinal origin and the mechanisms involved.MethodsThe gastric carcinoma cell lines (KATO-III and MKN45) and two chemoresistant subpopulations of the HT29 colon adenocarcinoma cell line (HT29-5M21 and HT29-5F12) were treated with a range of concentrations of bromelain, as well as with cisplatin as a positive control. The effect of bromelain on the growth and proliferation of cancer cells was determined using a sulforhodamine B assay after 72 hours of treatment. Expression of apoptosis-associated proteins in MKN45 cells treated with bromelain was analyzed by Western blotting.ResultsData from our sulforhodamine B assay showed that bromelain inhibited proliferation of HT29-5F12, HT29-5M21, MKN45, and KATO-III cells, with respective half maximal inhibitory concentration values of 29, 34, 94, and 142 μg/mL. Analyzing the expression of proapoptotic and antiapoptotic proteins in bromelain-treated MKN45 cells, we observed activation of the caspase system, cleavage of PARP and p53, overexpression of cytochrome C, attenuation of phospho-Akt and Bcl2, and removal of MUC1. Apart from the caspase-dependent apoptosis observed, emergence of cleaved p53 supports a direct, extranuclear apoptotic function of p53. Moreover, interrupted Akt signaling and attenuation of Bcl2 and MUC1 oncoproteins suggest impaired survival of cancer cells.ConclusionOur findings collectively indicate that bromelain exerts cytotoxic effects in a panel of human gastric and colon carcinoma cells. Our study of MKN45 cells implicated different mechanisms in bromelain-induced cell death. While promoting apoptosis with involvement of the caspase system and extranuclear p53, bromelain also appears to impair cancer cell survival by blocking the Akt pathway and attenuating Bcl2 and MUC1 oncoproteins.

Despite recent advances in the management of ovarian cancer, it remains the most lethal gynecologic malignancy. Vascular endothelial growth factor (VEGF) has been shown to play a pivotal role in the progression of ovarian cancer leading to the eventual development of malignant ascites. On this basis, agents rendering VEGF ineffective by neutralizing VEGF (bevacizumab), blocking its receptors (aflibercept), or interfering with the postreceptor signaling pathways (sunitinib) provide us with the rational treatment options. These agents are generally used in combination with the standard chemotherapeutic drugs. Here, we discuss the basis of and the logic behind the use of these agents in the treatment of epithelial ovarian cancer, as well as their evaluation in different preclinical and clinical studies.

Introduction: Drivers that underlie the progression of MGUS (Monoclonal gammopathy of undetermined significance) to multiple myeloma are yet largely unknown. Because of the vast number of potential players, these drivers may not necessarily aimed to transform plasma cell or the bone marrow niche, but rather remodel a supporting microenvironment. Metabolic alterations have been linked to cancer development and resistance to chemotherapy. It has been suggested that high rates of glycolysis and glutaminolysis are necessary in malignant cells to allow sensitive and precise control of the pathways that generate metabolic intermediates for macromolecular biosynthesis, hence cancer progression and metastasis. Experimental evidence indicates that glutamine, the most abundant amino acid in the blood and tissues, is the major respiratory fuel for cancer cells, and its conversion to glutamate is the first step in a series of reactions that generate essential metabolic intermediates. Thus, physiologic concentrations of circulating glutamine are required for optimal growth of malignant cells. This study attempts to identify circulating metabolites in myeloma patients which could potentially relate to disease progression. Methods: We employed hydrophilic interaction liquid chromatography (ZIC-pHILIC)-high resolution mass spectrometry (Q-Exactive) to profile metabolites in cell-free serum samples from 10 MGUS and 10 myeloma patients with written consent. The data were analysed using IDEOM software and its quality was assessed by calculating % RSD (relative standard deviation) of peak median and internal standards within groups, repeated analysis of pooled quality control samples, and inspecting the heatmap for outlier samples. The fold changes of metabolites were measured in the MGUS versus myeloma cohorts using the ratio of the mean peak intensities. Significant features generated after statistical analyses were used for metabolic pathway analysis. Results: In excess of 600 metabolite features were reproducibly detected, with 76 metabolites confidently identified based on authentic standards and the remainder putatively identified by accurate mass. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis determined that amino acids, carbohydrate and glycerolipid metabolism were affected by myeloma. L-glutamate, L-alanine and L-phenylalanine amino acids showed 0.63-, 0.71- and 0.70-fold decreases, respectively, in myeloma patients compared to MGUS individuals (p<0.05). Consistent with the literature, the circulating level of glutamine was maintained, confirming that glutamine's uptake and release by various organs and skeletal muscle is proportional to its usage by cancer cells for glutaminolysis that supplies them with L-glutamate. With regard to carbohydrate metabolism, D-gluconic acid, pentitol, glycerol and citrate with 0.57-, 0.60-, 0.68- and 0.80-fold decreases, respectively, (p <0.05) were among the compounds with the highest confidence that contributed to the discrimination between MGUS and myeloma. The only markedly decreased lipid-associated metabolite was sn-Glycerol 3-phosphate (p value: 0.043). Exploring the metabolic pathways employed by myeloma cells for energy and biomass generation, Pentose Phosphate Pathway (PPP) appeared to be highly perturbed as D-gluconic acid, D-ribose, deoxyribose and D-glucono-1,5-lactone all showed significantly decreased levels ranging from 0.38 to 0.70 fold. The involvement of the tricarboxylic acid (TCA) cycle, to which both L-glutamate and glucose can contribute, was also evident as suggested by decreases in citrate, malate (0.48-fold), cis-aconitate (0.68-fold) and succinate (0.76-fold). Conclusions: As proof of concept, our results showed significant differences in a number of circulating metabolites between myeloma and MGUS, which requires further validation through a quantitative metabolomics study. Here, the analysis of non-invasive sampling and easily traceable circulating metabolites exemplifies how detailed metabolic profiling could be potentially utilized to predict progression of MGUS to myeloma and to identify potential targets for treatment interventions. Disclosures Spencer: Celgene: Honoraria, Research Funding, Speakers Bureau; Janssen-Cilag: Honoraria, Research Funding, Speakers Bureau; Amgen: Honoraria, Research Funding; BMS: Research Funding; Takeda: Honoraria, Research Funding, Speakers Bureau; STA: Honoraria.

The enhancer of zeste homolog 2 (EZH2) oncogene is a histone methyltransferase that functions canonically as a catalytic subunit of the polycomb repressive complex 2 (PRC2) to tri-methylate histone H3 at Lys 27 (H3K27me3). Although targeting of EZH2 methyltransferase is a promising therapeutic strategy against cancer, methyltransferase-independent oncogenic functions of EZH2 are also described. Moreover, pharmacological EZH2 methyltransferase inhibition was only variably effective in pre-clinical and clinical studies, suggesting that targeting EZH2 methyltransferase alone may be insufficient. Here, we demonstrate a non-canonical mechanism of EZH2’s oncogenic activity through interactions with inosine monophosphate dehydrogenase 2 (IMPDH2) and downstream promotion of guanosine-5'-triphosphate (GTP) production. Liquid Chromatography-Mass Spectrometry (LC-MS) of EZH2 immunoprecipitates from melanoma cell lines and human patient-derived xenografts (PDXs) revealed EZH2-IMPDH2 interactions that were verified to occur between the N-terminal EED-binding domain of cytosolic EZH2 and the CBS domain of IMPDH2 in a PRC2- and methylation-independent manner. EZH2 silencing reduced cellular GTP, ribosome biogenesis, RhoA-mediated actomyosin contractility and melanoma cell proliferation and invasion by impeding the activity and cytosolic localization of IMPDH2. Guanosine, which replenishes GTP, reversed these effects and thereby promoted invasive and clonogenic cell states even in EZH2 silenced cells. IMPDH2 silencing antagonized the proliferative and invasive effects of EZH2, also in a guanosine-reversible manner. In human melanomas, high cytosolic EZH2 and IMPDH2 expression were associated with nucleolar enlargement, a marker for ribosome biogenesis. We also identified EZH2-IMPDH2 complexes in a range of cancers in which Sappanone A (SA), which inhibits EZH2-IMPDH2 interactions and thereby IMPDH2 tetramerization, was anti-tumorigenic, although notably non-toxic in normal human melanocytes and bone marrow derived blood progenitor cells that lacked observable EZH2-IMPDH2 interactions. These findings illuminate a previously unrecognized, non-canonical, methyltransferase-independent, but GTP-dependent mechanism by which EZH2 regulates tumorigenicity in melanoma and other cancers, opening new avenues for development of anti-EZH2 therapeutics.

The enhancer of zeste homolog 2 (EZH2) oncoprotein is a histone methyltransferase that functions canonically as a catalytic subunit of the polycomb repressive complex 2 (PRC2) to tri-methylate histone H3 at Lys 27 (H3K27me3). Although targeting EZH2 methyltransferase is a promising therapeutic strategy against cancer, methyltransferase-independent oncogenic functions of EZH2 are described. Moreover, pharmacological EZH2 methyltransferase inhibition was only variably effective in pre-clinical and clinical studies, suggesting that targeting EZH2 methyltransferase alone may be insufficient. Here, we demonstrate a non-canonical mechanism of EZH2’s oncogenic activity characterized by interactions with inosine monophosphate dehydrogenase 2 (IMPDH2) and downstream promotion of guanosine-5’-triphosphate (GTP) production. EZH2-IMPDH2 interactions identified by Liquid Chromatography-Mass Spectrometry (LC-MS) of EZH2 immunoprecipitates from melanoma cells were verified to occur between the N-terminal EED-binding domain of cytosolic EZH2 and the CBS domain of IMPDH2 in a methyltransfersase-independent manner. EZH2 silencing reduced cellular GTP, ribosome biogenesis, RhoA-mediated actomyosin contractility and melanoma cell proliferation and invasion by impeding the activity of IMPDH2. Guanosine, which replenishes GTP, reversed these effects and thereby promoted invasive and clonogenic cell states even in EZH2 silenced cells. IMPDH2 silencing antagonized the proliferative and invasive effects of EZH2, also in a guanosine-reversible manner. In human melanomas, high cytosolic EZH2 and IMPDH2 expression were associated with nucleolar enlargement, a marker of ribosome biogenesis. EZH2-IMPDH2 complexes were also observed in a range of cancers in which Sappanone A (SA), which inhibits EZH2-IMPDH2 interactions, was anti-tumorigenic, although notably non-toxic in normal cells. These findings illuminate a previously unrecognized, non-canonical, methyltransferase-independent, and GTP-dependent mechanism by which EZH2 regulates tumorigenicity in melanoma and other cancers, opening new avenues for development of anti-EZH2 therapeutics. Graphical AbstractHighlightsEZH2 has non-canonical methyltransferase-independent and GTP-dependent tumorigenic and metastatic functions in melanoma.The N-terminal EED-binding domain of EZH2 interacts with the CBS domain of IMPDH2 in a polycomb repressive complex 2- (PRC2-) and methylation-independent manner.EZH2 accumulates with IMPDH2 in the cytoplasm and increases IMPDH2’s tetramerization-mediated activity independently of EZH2 methyltransferase.EZH2 upregulates GTP synthesis by IMPDH2 activation and thereby activates ribosome biogenesis via rRNA synthesis and actomyosin contractility via RhoA GTPase.Sappanone A (SA) inhibits IMPDH2-EZH2 interactions and is anti-proliferative across a range of cancers including melanoma, but not in normal cells.