Jennifer D. Elster

Mitochondrial Structure, Function and Dynamics Are Temporally Controlled by c-Myc

Although the c-Myc (Myc) oncoprotein controls mitochondrial biogenesis and multiple enzymes involved in oxidative phosphorylation (OXPHOS), the coordination of these events and the mechanistic underpinnings of their regulation remain largely unexplored. We show here that re-expression of Myc in myc−/− fibroblasts is accompanied by a gradual accumulation of mitochondrial biomass and by increases in membrane polarization and mitochondrial fusion. A correction of OXPHOS deficiency is also seen, although structural abnormalities in electron transport chain complexes (ETC) are not entirely normalized. Conversely, the down-regulation of Myc leads to a gradual decrease in mitochondrial mass and a more rapid loss of fusion and membrane potential. Increases in the levels of proteins specifically involved in mitochondrial fission and fusion support the idea that Myc affects mitochondrial mass by influencing both of these processes, albeit favoring the latter. The ETC defects that persist following Myc restoration may represent metabolic adaptations, as mitochondrial function is re-directed away from producing ATP to providing a source of metabolic precursors demanded by the transformed cell.

Dendritic cell vaccines: A review of recent developments and their potential pediatric application

ABSTRACT For many cancers the use of conventional chemotherapy has been maximized, and further intensification of chemotherapy generally results in excess toxicity with little long-term benefit for cure. Many tumors become resistant to chemotherapy, making the investigation of novel approaches such as immunotherapy of interest. Because the tumor microenvironment is known to promote immune tolerance and down regulate the bodys natural defense mechanisms, modulating the immune system with the use of dendritic cell (DC) therapy is an attractive approach. Thousands of patients with diverse tumor types have been treated with DC vaccines. While antigen specific immune responses have been reported, the duration and magnitude of these responses are typically weak, and objective clinical responses have been limited. DC vaccine generation and administration is a multi-step process with opportunities for improvement in source of DC for vaccine, selection of target antigen, and boosting effector cell response via administration of vaccine adjuvant or concomitant pharmacologic immunomodulation. In this review we will discuss recent developments in each of these areas and highlight elements that could be moved into pediatric clinical trials.

Rapid In Vitro Derivation of Endothelium Directly From Human Cancer Cells

The development of an independent blood supply by a tumor is essential for maintaining growth beyond a certain limited size and for providing a portal for metastatic dissemination. Host-derived endothelial cells (ECs) residing in and compromising the tumor vasculature originate via distinct processes known as sprouting angiogenesis and vasculogenesis. More recently ECs originating directly from the tumor cells themselves have been described although the basis for this phenomenon remains poorly understood. Here we describe in vitro conditions that allow lung and ovarian cancer cells to undergo a rapid and efficient transition into ECs that are indistinguishable from those obtained in vivo. A variety of methods were used to establish that the acquired phenotypes and behaviors of these tumor-derived ECs (TDECs) closely resemble those of authentic ECs. Xenografts arising from co-inoculated in vitro-derived TDECs and tumor cells were also more highly vascularized than control tumors; moreover, their blood vessels were on average larger and frequently contained admixtures of host-derived ECs and TDECs derived from the initial inoculum. These results demonstrate that cancer cells can be manipulated under well-defined in vitro conditions to initiate a tumor cell-to-EC transition that is largely cell-autonomous, highly efficient and closely mimics the in vivo process. These studies provide a suitable means by which to identify and perhaps modify the earliest steps in TDEC generation.

Angiomatoid Fibrous Histiocytoma With Paraneoplastic Platelet Storage Pool Deficiency

AFH and paraneoplastic effect are shown to manifest as a platelet storage pool deficiency. Angiomatoid fibrous histiocytoma is a rare soft tissue tumor usually discovered in young individuals. This tumor is often mistaken for a hematoma and typically misdiagnosed. It is commonly found in the extremities and may be associated with a site of recent or previous trauma. Characteristic histology includes nodules of histiocytoid spindle cells with pseudoangiomatoid spaces, fibrous pseudocapsules, and lymphoid cuffing. We describe the case of an 8-year-old girl who presented after incision and drainage of a superficial thigh lesion and experienced subsequent chronic bleeding of her wound. Her initial presentation was concerning for an underlying bleeding disorder, and laboratory analysis uncovered a paraneoplastic platelet function disorder that resolved with therapy of the primary tumor.

Single-agent bevacizumab in the treatment of recurrent or refractory pediatric low-grade glioma: A single institutional experience

Bevacizumab‐based therapy has been demonstrated to be effective in the treatment of refractory or recurrent pediatric low‐grade glioma (LGG); however its efficacy as a single agent is less understood.

Abstract 5293: In vitro modeling of tumor-derived endothelial cell derivation

Background: Tumor growth beyond a few millimeters in size requires the development of a neovasculature. In addition to providing a portal for the systemic dissemination of metastatic cells, this allows the tumor bed to overcome the severe hypoxia, acidosis, and nutrient deprivation that otherwise limits tumor growth. Early research presumed the development of genetically and functionally normal tumor vasculature from normal host tissue. Anti-angiogenic agents were thus developed to inhibit tumor blood supply with the hope that the presumed normal tumor vascular endothelial cells (EC9s), would be less inclined to develop drug resistance. Thus far, however, the experience with these agents has been one of only incremental improvement in patient survival. We have previously demonstrated that tumor cells can differentiate, in vivo, into an EC phenotype and form functional tumor vasculature. Formation of these “tumor derived endothelial cells” (TDEC9s) offers a partial explanation for the disappointing clinical results of the angiogenesis inhibitors and suggests a new, complementary, therapeutic target. Objectives: To develop an in vitro system that would recapitulate the tumor cell to EC transition seen in vivo. We hypothesize that manipulation of culture conditions to mimic the tumor microenvironment would result in a switch to an EC phenotype. Design/Methods: A variety of human cancer cell lines (H460 lung cancer, PC3 prostate cancer, OVCAR-8 ovarian cancer) were cultured in 1% O 2 in low glucose DMEM supplemented with EC-specific growth factors. The cells were assayed for EC-specific proteins and transcripts with western blotting, immunofluorescence, flow cytometry, and rtPCR. Functionality was quantified by the uptake of acetylated-LDL and the ability to vascularize tumor xenografts. Results: Human cancer cell lines exposed to hypoxia and EC-specific growth factors increase expression of a variety of EC-specific proteins including von Willebrand9s factor, ESAM, and VE-Cadherin, while down regulating the epithelial specific cytokeratins. Inclusion of a twenty percent minority of these in vitro-derived TDEC9s in a tumor inoculum results in an increase in both tumor growth rate and vascular density. These in vitro-derived TDEC9s are also found within the tumor neo-vasculature. Conclusions: We have developed culture conditions that can, within a span of only five days, induce many of the same phenotypic and functional characteristics of the TDEC9s isolated from tumor xenografts grown for nearly two months. Furthermore, these cells are able to act as functional endothelial cells in vivo. Potential uses for this system include the ability to study the mechanistic underpinnings of the tumor cell to TDEC transition and to identify pharmacologic inhibitors of this transition. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5293. doi:1538-7445.AM2012-5293

Abstract 1259: c-Myc influences mitochondrial structure and function by regulating fusion and fission

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Background: c-Myc (Myc) is a global transcription factor that controls the expression of a large part of the human genome. The numerous Myc target genes function in a variety of normal cellular processes whose collective expression of these processes is referred to as the “Myc phenotype”. One such cellular process is the regulation of mitochondrial biogenesis. Objectives: To understand the specific influence that Myc has on mitochondrial structure and function. We hypothesize that Myc is involved in the regulation of both the production and destruction of mitochondria, and that the ability of Myc to maintain this balance has an impact on cellular transformation. Design/Method: Various cell lines that allow for the manipulation of Myc levels have been used. These include cells that have been engineered to have inducible Myc over-expression as well as inducible expression of Myc shRNA. These strains were used in a series of assays that measured different aspects of the Myc effect on mitochondrial structure and function. Most notably, metabolic pathways were measured by an extracellular flux analyzer and electron and confocal microscopy was performed to examine the structure of the mitochondria in detail. Results: The induction of Myc results in dramatic increases in overall mitochondrial mass, as well as increasing individual mitochondrial size and cristae density. This increase in recognizable mitochondria correlates to increases in oxidative phosphorylation and decreased mitochondrial loss through mitophagy. Finally, Myc levels correlate to increased mitochondrial inter-connectivity. This appears to be related to the ability of Myc to influence the expression of the mitochondrial fusion protein, Opa1 and the fission protein, DLP1. Conclusions Reached: The changes in mitochondrial structure and function are directly influenced by the expression of Myc. There appear to be multiple pathways involved in maintaining a specific mitochondrial mass, which emphasizes the importance of this organelle in cellular homeostasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1259. doi:10.1158/1538-7445.AM2011-1259