Shareen Iqbal

cAMP-responsive element-binding protein regulates vascular endothelial growth factor expression: implication in human prostate cancer bone metastasis

Aberrant expression of vascular endothelial growth factor (VEGF) is associated with human prostate cancer (PCa) metastasis and poor clinical outcome. We found that both phosphorylation of cyclic AMP-responsive element-binding protein (CREB) and VEGF levels were significantly elevated in patient bone metastatic PCa specimens. A PCa ARCaP progression model demonstrating epithelial-to-mesenchymal transition exhibited increased CREB phosphorylation and VEGF expression as ARCaP cells became progressively more mesenchymal and bone-metastatic. Activation of CREB induced, whereas inhibition of CREB blocked, VEGF expression in ARCaP cells. CREB may regulate VEGF transcription via a hypoxia-inducible factor-dependent mechanism in normoxic conditions. Activation of CREB signaling is involved in the coordinated regulation of VEGF and may pre-dispose to PCa bone metastasis.

Reproducible Research Practices and Transparency across the Biomedical Literature.

There is a growing movement to encourage reproducibility and transparency practices in the scientific community, including public access to raw data and protocols, the conduct of replication studies, systematic integration of evidence in systematic reviews, and the documentation of funding and potential conflicts of interest. In this survey, we assessed the current status of reproducibility and transparency addressing these indicators in a random sample of 441 biomedical journal articles published in 2000–2014. Only one study provided a full protocol and none made all raw data directly available. Replication studies were rare (n = 4), and only 16 studies had their data included in a subsequent systematic review or meta-analysis. The majority of studies did not mention anything about funding or conflicts of interest. The percentage of articles with no statement of conflict decreased substantially between 2000 and 2014 (94.4% in 2000 to 34.6% in 2014); the percentage of articles reporting statements of conflicts (0% in 2000, 15.4% in 2014) or no conflicts (5.6% in 2000, 50.0% in 2014) increased. Articles published in journals in the clinical medicine category versus other fields were almost twice as likely to not include any information on funding and to have private funding. This study provides baseline data to compare future progress in improving these indicators in the scientific literature.

Genetic polymorphisms linked to susceptibility to malaria

The influence of host genetics on susceptibility to Plasmodium falciparum malaria has been extensively studied over the past twenty years. It is now clear that malaria parasites have imposed strong selective forces on the human genome in endemic regions. Different genes have been identified that are associated with different malaria related phenotypes. Factors that promote severity of malaria include parasitaemia, parasite induced inflammation, anaemia and sequestration of parasitized erythrocytes in brain microvasculature.Recent advances in human genome research technologies such as genome-wide association studies (GWAS) and fine genotyping tools have enabled the discovery of several genetic polymorphisms and biomarkers that warrant further study in host-parasite interactions. This review describes and discusses human gene polymorphisms identified thus far that have been shown to be associated with susceptibility or resistance to P. falciparum malaria. Although some polymorphisms play significant roles in susceptibility to malaria, several findings are inconclusive and contradictory and must be considered with caution. The discovery of genetic markers associated with different malaria phenotypes will help elucidate the pathophysiology of malaria and enable development of interventions or cures. Diversity in human populations as well as environmental effects can influence the clinical heterogeneity of malaria, thus warranting further investigations with a goal of developing new interventions, therapies and better management against malaria.

EPLIN downregulation promotes epithelial–mesenchymal transition in prostate cancer cells and correlates with clinical lymph node metastasis

Epithelial–mesenchymal transition (EMT) is a crucial mechanism for the acquisition of migratory and invasive capabilities by epithelial cancer cells. By conducting quantitative proteomics in experimental models of human prostate cancer (PCa) metastasis, we observed strikingly decreased expression of EPLIN (epithelial protein lost in neoplasm; or LIM domain and actin binding 1, LIMA-1) upon EMT. Biochemical and functional analyses demonstrated that EPLIN is a negative regulator of EMT and invasiveness in PCa cells. EPLIN depletion resulted in the disassembly of adherens junctions, structurally distinct actin remodeling and activation of β-catenin signaling. Microarray expression analysis identified a subset of putative EPLIN target genes associated with EMT, invasion and metastasis. By immunohistochemistry, EPLIN downregulation was also demonstrated in lymph node metastases of human solid tumors including PCa, breast cancer, colorectal cancer and squamous cell carcinoma of the head and neck. This study reveals a novel molecular mechanism for converting cancer cells into a highly invasive and malignant form, and has important implications in prognosis and treating metastasis at early stages.

PDGF Upregulates Mcl-1 Through Activation of β-Catenin and HIF-1α-Dependent Signaling in Human Prostate Cancer Cells

Background Aberrant platelet derived growth factor (PDGF) signaling has been associated with prostate cancer (PCa) progression. However, its role in the regulation of PCa cell growth and survival has not been well characterized. Methodology/Principal Findings Using experimental models that closely mimic clinical pathophysiology of PCa progression, we demonstrated that PDGF is a survival factor in PCa cells through upregulation of myeloid cell leukemia-1 (Mcl-1). PDGF treatment induced rapid nuclear translocation of β-catenin, presumably mediated by c-Abl and p68 signaling. Intriguingly, PDGF promoted formation of a nuclear transcriptional complex consisting of β-catenin and hypoxia-inducible factor (HIF)-1α, and its binding to Mcl-1 promoter. Deletion of a putative hypoxia response element (HRE) within the Mcl-1 promoter attenuated PDGF effects on Mcl-1 expression. Blockade of PDGF receptor (PDGFR) signaling with a pharmacological inhibitor AG-17 abrogated PDGF induction of Mcl-1, and induced apoptosis in metastatic PCa cells. Conclusions/Significance Our study elucidated a crucial survival mechanism in PCa cells, indicating that interruption of the PDGF-Mcl-1 survival signal may provide a novel strategy for treating PCa metastasis.

Epidermal Growth Factor Promotes Protein Degradation of Epithelial Protein Lost in Neoplasm (EPLIN), a Putative Metastasis Suppressor, during Epithelial-mesenchymal Transition

Background: The mechanism of EGF signaling in the regulation of prostate cancer (PCa) metastasis remains unclear. Results: EGF promotes epithelial-mesenchymal transition (EMT) and induces degradation of epithelial protein lost in neoplasm (EPLIN), a putative suppressor of PCa metastasis. Conclusion: EGF activates ERK1/2-dependent phosphorylation, ubiquitination, and protein turnover of EPLIN. Significance: This study suggested that blockade of EGF signaling could retard EMT and inhibit invasiveness of PCa cells. Aberrant expression of EGF receptors has been associated with hormone-refractory and metastatic prostate cancer (PCa). However, the molecular mechanism for EGF signaling in promoting PCa metastasis remains elusive. Using experimental models of PCa metastasis, we demonstrated that EGF could induce robust epithelial-mesenchymal transition (EMT) and increase invasiveness. Interestingly, EGF was found to be capable of promoting protein turnover of epithelial protein lost in neoplasm (EPLIN), a putative suppressor of EMT and tumor metastasis. Mechanistic study revealed that EGF could activate the phosphorylation, ubiquitination, and degradation of EPLIN through an extracellular signal-regulated kinase 1/2 (ERK1/2)-dependent signaling cascade. Pharmacological inhibition of the ERK1/2 pathway effectively antagonized EGF-induced EPLIN degradation. Two serine residues, i.e. serine 362 and serine 604, were identified as putative ERK1/2 phosphorylation sites in human EPLIN, whose point mutation rendered resistance to EGF-induced protein turnover. This study elucidated a novel molecular mechanism for EGF regulation of EMT and invasiveness in PCa cells, indicating that blockade of EGF signaling could be beneficial in preventing and retarding PCa metastasis at early stages.

Genistein enhances the efficacy of cabazitaxel chemotherapy in metastatic castration-resistant prostate cancer cells

Cabazitaxel (Jevtana) has been approved for the treatment of metastatic castration‐resistant prostate cancer (mCRPC). However, most patients progress and become chemoresistant, which remains a major challenge in the management of advanced PCa. In this study, we investigated whether genistein, an isoflavone abundant in soy products, could sensitize mCRPC cells to cabazitaxel treatment in experimental models.

BKM1740, an Acyl-Tyrosine Bisphosphonate Amide Derivative, Inhibits the Bone Metastatic Growth of Human Prostate Cancer Cells by Inducing Apoptosis

Purpose: Survivin overexpression has been associated with an unfavorable outcome in human PCa; however, its role in metastasis remains elusive. We aim to (a) evaluate the clinical implications of survivin expression in PCa bone metastasis; (b) determine in vivo efficacy of BKM1740, a small-molecule compound, against PCa skeletal growth and survival; and (c) investigate molecular mechanism by which BKM1740 augments apoptosis in bone metastatic PCa cells. Experimental Design: Survivin expression was analyzed in PCa specimens and experimental models. Bone metastatic C4-2 and ARCaPM cell lines were used to evaluate the in vitro effects of BKM1740 and molecular mechanism for the induction of apoptosis. C4-2 cells were grown intratibially in athymic nude mice to evaluate the in vivo efficacy of BKM1740. Tumor growth in mouse bone was assessed by serum prostate-specific antigen and radiography and confirmed by immunohistochemical analyses. Results: Survivin expression is positively associated with clinical PCa bone metastasis. BKM1740 induced apoptosis in PCa cells by repressing survivin. Mice with established C4-2 tumors in tibia showed a marked decrease in serum prostate-specific antigen and much improved bone architecture radiographically after treatment with BKM1740. Immunohistochemical assays of mouse tumor samples confirmed that the in vivo effects were mediated by inhibition of survivin and induction of apoptosis. Conclusions: Survivin expression is associated with PCa bone metastasis. BKM1740 treatment specifically inhibited survivin and induced apoptosis in vitro and was efficacious in retarding PCa skeletal growth in a mouse model. BKM1740 is a promising small-molecule compound that could be used to treat PCa bone metastasis.

Pomegranate extract inhibits the bone metastatic growth of human prostate cancer cells and enhances the in vivo efficacy of docetaxel chemotherapy.

Docetaxel treatment is the only first‐line chemotherapy with a survival benefit in metastatic castration‐resistant prostate cancer (PCa). Nonetheless, most patients become docetaxel resistant and inevitably progress with no cure. In this study, we investigated the potential of pomegranate extract (PE) in targeting metastatic castration‐resistant PCa and improving docetaxel chemotherapy.