Metabolic requirement for GOT2 in pancreatic cancer depends on environmental context

Mitochondrial glutamate-oxaloacetate transaminase 2 (GOT2) is part of the malate-aspartate shuttle, a mechanism by which cells transfer reducing equivalents from the cytosol to the mitochondria. GOT2 is a key component of mutant KRAS (KRAS*)-mediated rewiring of glutamine metabolism in pancreatic ductal adenocarcinoma (PDA). Here, we demonstrate that the loss of GOT2 disturbs redox homeostasis and halts proliferation of PDA cells in vitro. GOT2 knockdown (KD) in PDA cell lines in vitro induced NADH accumulation, decreased Asp and α-ketoglutarate (αKG) production, stalled glycolysis, disrupted the TCA cycle, and impaired proliferation. Oxidizing NADH through chemical or genetic means resolved the redox imbalance induced by GOT2 KD, permitting sustained proliferation. Despite a strong in vitro inhibitory phenotype, loss of GOT2 had no effect on tumor growth in xenograft PDA or autochthonous mouse models. We show that cancer-associated fibroblasts (CAFs), a major component of the pancreatic tumor microenvironment (TME), release the redox active metabolite pyruvate, and culturing GOT2 KD cells in CAF conditioned media (CM) rescued proliferation in vitro. Furthermore, blocking pyruvate import or pyruvate-to-lactate reduction prevented rescue of GOT2 KD in vitro by exogenous pyruvate or CAF CM. However, these interventions failed to sensitize xenografts to GOT2 KD in vivo, demonstrating the remarkable plasticity and differential metabolism deployed by PDA cells in vitro and in vivo. This emphasizes how the environmental context of distinct pre-clinical models impacts both cell-intrinsic metabolic rewiring and metabolic crosstalk with the TME.

Osteopontin (OPN/SPP1) isoforms collectively enhance tumor cell invasion and dissemination in esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) is often diagnosed at an advanced stage, thus understanding the molecular basis for EAC invasion and metastasis is critical. Here we report that SPP1/OPN was highly overexpressed in primary EACs and intracellularly localized to tumor cells. We further demonstrate that all known OPN isoforms (OPNa, b, c, 4 and 5) were frequently co-overexpressed in primary EACs. Distinct pro-invasion and dissemination phenotypes of isoform-specific OPNb and OPNc stable transfectants were observed. Expression of OPNb significantly enhanced cell migration and adhesion to laminin. In contrast, OPNc cells showed significantly decreased cell migration yet increased cell detachment. Enhanced invasion, both in vitro and in vivo, was observed for OPNb- but not OPNc-expressing cells. Inhibition of RGD integrins, one family of OPN receptors, attenuated OPNb cell migration, abrogated OPNb cell adhesion and significantly reduced OPNb cell clonogenic survival but did not affect OPNc phenotypes, indicating that OPNb but not OPNc acts through integrin-dependent signaling. Differential expression of vimentin, E-cadherin and β-catenin in OPN stable cells may account for the variation in cell adhesion and detachment between these isoforms. We conclude that while all OPN isoforms are frequently co-overexpressed in primary EACs, isoforms OPNb and OPNc enhance invasion and dissemination through collective yet distinct mechanisms.

IGFBP2 modulates the chemoresistant phenotype in esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) patients commonly present with advanced stage disease and demonstrate resistance to therapy, with response rates below 40%. Understanding the molecular mechanisms of resistance is crucial for improvement of clinical outcomes. IGFBP2 is a member of the IGFBP family of proteins that has been reported to modulate both IGF and integrin signaling and is a mediator of cell growth, invasion and resistance in other tumor types. In this study, high IGFBP2 expression was observed in a subset of primary EACs and was found to be significantly higher in patients with shorter disease-free intervals as well as in treatment-resistant EACs as compared to chemonaive EACs. Modulation of IGFBP2 expression in EAC cell lines promoted cell proliferation, migration and invasion, implicating a role in the metastatic potential of these cells. Additionally, knockdown of IGFBP2 sensitized EAC cells to cisplatin in a serum-dependent manner. Further in vitro exploration into this chemosensitization implicated both the AKT and ERK pathways. Silencing of IGFBP2 enhanced IGF1-induced immediate activation of AKT and reduced cisplatin-induced ERK activation. Addition of MEK1/2 (selumetinib or trametinib) or AKT (AKT Inhibitor VIII) inhibitors enhanced siIGFBP2-induced sensitization of EAC cells to cisplatin. These results suggest that targeted inhibition of IGFBP2 alone or together with either the MAPK or PI3K/AKT signaling pathway in IGFBP2-overexpressing EAC tumors may be an effective approach for sensitizing resistant EACs to standard neoadjuvant chemotherapy.

Abstract 4440: The functional role of insulin-like growth factor binding protein-2 in esophageal adenocarcinoma chemoresistance

Despite improved understanding of esophageal adenocarcinoma (EAC) progression and advances in endoscopic surveillance and multimodality treatment, patients commonly present with advanced stage disease and demonstrate resistance to therapy, with complete response rates below 40%. Understanding the molecular mechanisms of resistance is crucial for predicting and overcoming this resistance.

IGFBP2 is a member of the IGFBP family of proteins that has been shown to modulate both insulin growth factor (IGF) and integrin signaling and is a mediator of cell growth, invasion and resistance in other tumor types. Because these pathways have been implicated in esophageal cancer growth and progression, we evaluated the functional role of IGFBP2 in EAC tumorigenesis and chemoresistance. High IGFBP2 expression was observed in a subset of EAC patients and was found to be significantly higher in patients with shorter disease-free intervals as well as in treatment-resistant EACs as compared to chemonaive EACs.

To evaluate the role of IGFBP2 as a potential modulator of chemoresistance in vitro, IGFBP2-expressing Flo-1 EAC cells were pretreated with siRNA to IGFBP2 while non-expressing OE33 EAC cells were stably-transfected with an IGFBP2 expression construct or pre-treated with exogenous recombinant IGFBP2 followed by 3-day treatment with chemotherapy. All experiments were performed in serum-deprived and serum-replete conditions and were assessed using WST-1 cell proliferation reagent.

IGFBP2 siRNA inhibition sensitized Flo-1 cells to cisplatin in the presence of serum but exogenous treatment or ectopic expression of IGFBP2 in OE33 cells did not alter their chemosensitivity. Immunoblot analyses of Flo-1 cells treated with cisplatin showed a dose-dependent reduction in IGFBP2 expression but a dose-dependent induction of ERK and AKT phosphorylation at 24 hours post-treatment. Knockdown of IGFBP2 blocked IGF1 and CDDP-induced ERK activation at 15 minutes and 3-days post-treatment, respectively. In contrast, IGFBP2 knockdown resulted in the activation of AKT and was further enhanced by the addition of IGF1 up to 24 hours post-treatment. In an attempt to augment siIGFBP2-induced CDDP chemosensitization, we pretreated Flo-1 cells with either a MEK1/2 inhibitor, selumetinib or trametinib, or the AKT inhibitor, AKT Inhibitor VIII, in repeat cytotoxicity assays. The MEK1/2 inhibitors increased sensitivity in serum-replete conditions while AKT Inhibitor VIII increased sensitivity in serum-deprived conditions as compared to CDDP alone, IGFBP2 knockdown alone, and the combination of IGFBP2 knockdown and CDDP. These results suggest that targeted modulation of IGFBP2 and either the MAPK or PI3K/AKT signaling pathway in IGFBP2-overexpressing EAC tumors may be an effective approach for sensitizing resistant tumors to standard-of-care chemotherapy treatment options.

Citation Format: Amy L. Myers, Lin Lin, Derek J. Nancarrow, Zhuwen Wang, Daysha Ferrer-Torres, David G. Beer, Andrew C. Chang. The functional role of insulin-like growth factor binding protein-2 in esophageal adenocarcinoma chemoresistance. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4440. doi:10.1158/1538-7445.AM2015-4440

Self-efficacy as a relevant construct in understanding sexual response and dysfunction

While self-efficacy has been widely used to explain and treat various biobehavioral responses, few investigations have examined this concept in the context of sexual response and dysfunction. In this study, the authors constructed a measure of sexual self-efficacy, investigated whether it differentiated men with and without sexual dysfunction, and determined the utility of this construct by exploring its relation to other variables known to be related to erectile dysfunction in a sample of 60 men with erectile dysfunction and 14 functional men visiting a urology clinic. The sexual self-efficacy index differentiated men with and without erectile dysfunction, and general linear modeling showed that the index did indeed relate to other variables known to affect sexual and emotional response during a partnered sexual experience. These findings suggest that, as a unifying construct that predicts cognitive, affective, motivational, and behavioral responses, sexual self-efficacy has the potential to play an important role in the assessment of effective treatments for sexual problems.

Abstract 3879: Osteopontin (SPP1/OPN) alternative splice variants and metastatic potential in esophageal adenocarcinoma

Objective: The incidence of esophageal adenocarcinoma (EAC) has increased over 300% in the past decades in western countries. EAC is characterized by an early metastasis, with a 5-year survival rate of only 19%, making the identification of clinically-targetable proteins critical for improving patient outcome. Osteopontin (SPP1/OPN) is a secreted glycosylated phosphoprotein that is found overexpressed in many cancer types including EAC. OPN protein functions in cell adhesion and cell migration by regulating cell-matrix interactions and cellular signaling through binding with integrin and CD44 receptors. However, little is known about the role of OPN in EAC invasion and metastasis.

Methods: We analyzed the OPN gene expression in a series of 46 esophageal samples including esophageal Barrett's, low-grade dysplasia, high-grade dysplasia and adenocarcinomas mRNA using Affymetrix U133A arrays. Real-time RT-PCR was performed to validate array results and examine a larger cohort of 130 EAC samples. Tissue microarrays (TMA) were made containing 64 EACs, eight lymph node metastases, eight dysplastic and 11 none dysplastic Barrett's mucosa sections from 59 patients. Primers flanking the potential gene alternative splice regions were designed and the in-frame transcript variants were sequenced. Expression of OPN in EAC cell lines was analyzed using RT-PCR and western blot analysis. Ectopic OPN expression of splice variants and OPN knockdown in EAC cell lines have been performed to examine its roles in tumor invasion and EMT assays.

Results: OPN is highly overexpressed in EAC and overexpression of the gene is associated with poorer survival in patients. Three OPN splice variants were identified with their expression either proportionally increased or differentially expressed in the primary EAC and EAC-derived cells. Highly overexpressed OPN is a transcriptional event as no OPN gene amplification was found in the corresponding EACs. In addition, abundant OPN protein was found primarily in tumor cells in the tissue sections using immunohistochemical (IHC)-TMA assays. OPN variants differ in their N-terminal thrombin fragment with either exon 6 or 5 being absent in OPN-b or OPN-c, respectively. We found that EAC cells treated with the medium containing different OPN variants demonstrated distinctive morphological phenotypes. We further identified that OPN variants played different roles in tumor cell proliferation, epithelial-mesenchymal transition (EMT), and chemosensitivity.

Conclusion: Upregulation of OPN is predominant event in primary EACs and associated with poorer survival in patients. The alternative splice variants demonstrate differential tumor invasion, EMT transition and chemosensitivity in EAC cells.

Citation Format: Zhuwen Wang, Kimmy Leverenz, Dafydd G. Thomas, Amy L. Myers, Andrew C. Chang, Mark B. Orringer, Thomas J. Giordano, Jules Lin, David G. Beer, Lin Lin. Osteopontin (SPP1/OPN) alternative splice variants and metastatic potential in esophageal adenocarcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3879. doi:10.1158/1538-7445.AM2013-3879

Role of attribution in affective responses to a partnered sexual situation among sexually dysfunctional men

Study Type - Therapy (qualitative) Level of Evidence 4 What's known on the subject? and What does the study add? Sexually dysfunctional men report higher negative affect and lower positive affect than sexually functional men. Furthermore, men with sexual problems tend to make internal, self-blaming, attributions for negative sexual events, which can result in a diminished sense of self-efficacy and cause men to expect similar negative outcomes across future sexual situations. This pattern may sustain and actually intensify the sexual problem. This study shows that causal attributions for dysfunctional response influence emotional response to a partnered sexual situation. Specifically, sexually dysfunctional men who attribute their problem to a medical condition do better emotionally than those who attribute the problem to unknown or psychological factors - and this attribution process is a more powerful and reliable predictor of emotional response than the man's actual diagnosed somatic risk for a sexual problem. Furthermore, the study strongly suggests that those men who attribute their problem to a physical/medical issue are able to 'externalize' it - needing to assume less responsibility for and/or control over it, thereby reducing their psychological burden. These findings indicate not only that communication between physician and patient regarding the aetiology of a sexual problem may be critically important but also that, at least for some patients, pharmacological treatment should be combined with strategies that promote the development of internal positive self-serving attributions surrounding sexual activity.

OBJECTIVE

To investigate factors that influence sexually dysfunctional men's emotional response within a partnered sexual situation, and, most specifically, whether they attribute their dysfunctional response to a specific biomedical cause vs a psychological or unknown cause.

PATIENTS AND METHODS

Based on a sample of 59 sexually dysfunctional men visiting a urology clinic, linear regression was used to determine the relationship between patients' attributions and five global affective factors derived through principal components analysis: apprehension, insecure, arousable, affection, and pleasant. Two other covariates were included: actual (diagnosed) somatic risk as determined by the patient's medical history and clinician's notes, and the patient's self-reported importance of sexual intimacy.

RESULTS

Attribution (biomedical vs psychological/unknown) had significant effects on three psycho-affective factors (insecure, arousable, affection); men who attributed their problem to a biomedical cause had higher positive affect and lower insecurity. Diagnosed somatic risk was significant for insecure and marginally for affection. Importance of sex was significant on four psycho-affective variables (insecure, arousable, pleasant, affection), with higher endorsement associated with higher insecurity and lower positive affect.

CONCLUSIONS

Men who can attribute their sexual dysfunction to a medical condition do much better emotionally (higher positive affect and lower negative affect) than those who attribute the problem to unknown or psychological factors - and this factor is more predictive of their emotionality than the patient's actual somatic risk for sexual dysfunction. As demonstrated in a previous analysis, higher ratings of the importance of sex independently predicted stronger negative affect for men experiencing sexual problems.

Maturation of tumor vasculature by interferon-beta disrupts the vascular niche of glioma stem cells

BACKGROUND

The vascular niche necessary for cancer stem cell maintenance is a potential target for cancer therapy.

MATERIALS AND METHODS

Human glioma xenografts were treated with IFN-β delivered systemically via a liver-targeted, adeno-associated viral vector. The vascular niche was examined with immunofluorescence for glioma stem cells, endothelial cells, and perivascular cells.

RESULTS

Although IFN-β was not directly toxic to glioma stem cells in vitro, IFN-β decreased tumor size and the number of stem cells recovered in both heterotopic and orthotopic models. Treatment with IFN-β increased perivascular cells investing the tumor vasculature (6-fold) distancing stem cells from endothelial cells. Additionally, vascular smooth muscle cells co-cultured between stem cells and endothelial cells decreased stem cell recovery.

CONCLUSION

Continuous delivery of IFN-β decreased the number of stem cells in glioma xenografts by disrupting the vascular niche through an increase in perivascular cells, which created a barrier between the glioma stem cells and the endothelial cells.

Discharge Planning Process

Discharge planning is an integral but ill-defined process in most acute care settings. The time available to a healthcare team to adequately prepare patients for discharge has virtually evaporated with decreasing lengths of hospital stay. A research utilization (RU) team at a tertiary care teaching institution reviewed the literature from 1990 to 2002 in search of a research-based practice regarding staff nurses' roles in the discharge process. Review of the literature revealed varied discharge planning processes using staff nurses, advanced practice nurses, or case managers specifically prepared to implement the discharge planning process. Insufficient evidence was found to support a change from the current staff nurse practice.

The use of 16S and 16S-23S rDNA to easily detect and differentiate common Gram-negative orchard epiphytes

The identification of Gram-negative pathogenic and non-pathogenic bacteria commonly isolated from an orchard phylloplane may result in a time consuming and tedious process for the plant pathologist. The paper provides a simple "one-step" protocol that uses the polymerase chain reaction (PCR) to amplify intergenic spacer regions between 16S and 23S genes and a portion of 16S gene in the prokaryotic rRNA genetic loci. Amplified 16S rDNA, and restriction fragment length polymorphisms (RFLP) following EcoRI digestion produced band patterns that readily distinguished between the plant pathogen Erwinia amylovora (causal agent of fire blight in pear and apple) and the orchard epiphyte Pantoea agglomerans (formerly E. herbicola). The amplified DNA patterns of 16S-23S spacer regions may be used to differentiate E. amylovora at the intraspecies level. Isolates of E. amylovora obtained from raspberries exhibited two major fragments while those obtained from apples showed three distinct amplified DNA bands. In addition, the size of the 16S-23S spacer region differs between Pseudomonas syringae and Pseudomonas fluorescens. The RFLP pattern generated by HaeIII digestion may be used to provide a rapid and accurate identification of these two common orchard epiphytes.